USHGA Ground Skimmer July 1976 by US Hang Gliding & Paragliding Association

ONE DOLLAR

oun

JULY, 1976

Although only 14 WILLS WI NG SST's entered the 1976 World Open at Country among a field of over three hundred and fifty competitors, 'JO SST's qualified among the top one hundred gliders. When the field was cut to fifty, 8 SST's were still in the running. When it was cut again to ten, there were still 4 SST's in contention, and when it was all over a WILLS WING SST was the highest placing rogallo in the meet, as Dave Saffold finished second overall in a production SST 1OOC. The other three in the top ten were Dave Vincent, Curt Kiefer, and Bob Wills, all in production SST I OOB's. Meanwhile, Al Bartholomew was flying his SST HlOB in the U.S. Nationals qualifying meet at place by over 1,000 points.

Mountain. Al took first

These impressive accomplishments follow on the heels of Chris Price's incredible 33.6 mile world record cross-country flight across the San Fernando Valley in a production SST 11 OP. Find out for yourself why the SST is performing these feats. Don't just talk to a salesman. Test fly an SST and discover,

ILLS

XP RI N

L 1208 H East Walnut Street Santa Ana, California 92701 (714) 547-1344

•••

JULY 1976 ISSUE NO. 42

EDITOR: R,ch Grigsby LA YOUT & DES IGN : M ark Al lison EDITORIAL ASS ISTANT : Sharon G ri gsby OFFICE STAH MANAGER : C.irol Veld errain Susan Bischof, H f'dy Kleyweg, Jane l M eyer USHGA OFFICER<, PRE SIDENT : Vern Round1rec VICE PRESIDEN r: Jo hn LJke SECRET1\RY: John I IMrn TREASURER: Ll oyd I 1cher USHGA REGIO NAL DIRECTORS REG ION I: Vern Roundtree, Gil Dodgen . REGION 2: lee S1erio,, Jo hn G r.ice.REGION I: Ll oyd Licher, D,,n Poynter, John l,lkt:, Ch r i, W ills REGION 4: D on Bench . REGION 5: Gary Osaba . REGION 6 . D,1rryl Sm it h. RE GION 7: M ik e Z1o1sk,1,. RE G ION 8: To m Peghin y, Dan Ch apman . REG ION 9: V ic Pow el l, Chuck Sl usarc,yk. RE GION 10: H arry Robb, Jo hn H arris. REGION 1 I: Dave Broyles. DI RECTOR S- AT -LARGE : RE G ION I : Bill Johnson. REG ION 6: Al Mul,,t t i. REG ION 9: Dfmni s Pagcm . REG ION 11: John Wh i te. HONORARY DIRECTOR: I lugh Morton. EX O FFICIO DIRECTO R of USHG1\ as we are a d ivi sion of NAA: General Brooke Allen.

CONSUMER ADV I S ORY : G ROUND SKIMMER and USHGA, Inc. do not endorse or take any responsibility for the produc ts advertised or mentioned within these pages. Please consult the HMA or pilots and dealers in your area .

GROUnn ,HlfflffllR fflAGAZlftE CONTE N TS ~~~~~~~~~~-

ULTRALIGHT CONVERSATION

10.

ULTRALIGHT N EW S

l I.

CALENDAR

20.

FLYING YOSEMITE by John Davi~ & Dean Pascha ll

22.

THE STABILIT Y OF TA ILLESS G LIDERS by Stan H al l

28.

GALLERY

32.

FLEXIBILITY vs. STRENGTH by Chri s Wil b, M ike M eier, Chris Price

35.

USH GA, 1976 NATIO NA L CHAMPIONSHIPS -

36.

BATTEN S hy Jim W alker

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~~~~~~~~~~~~~~~~~~~~~~~

RESU LTS

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39. SAFETY CO LUMN by Tom Ga ul 40.

FLAP HAPPY by W alt er Carn ahan

43.

REG IO N 2 : USI-IGA INSTRUCTOR CE RTI FICATION CLINIC by Jack H all

... µort t•n 1hu,1,,._h 10 t rt•,11 (' ll1tl h<'r 1n 1~1e-.11n 1lw .. 1H,, 1, ht• ,I medn .. ol UI K'II c omnwn1l.i1to11 ,uu l l o ,uh .i nc t•

44 .

PITCH STABILI TY AND CONTROL PART Il l hy Ga ry Va l le

h ,,nH Hl1d1r1R metit()(f, .1ml ,Jlctv . Con1r1hut 10 1h ,11t• wi~l<.rnn•• Anyo,w ,., rnv1 1NI 10 (on1nhuw ,HI •< It•,, p hnw,, .1 nd , Ilu.,11 ,1l 1<>1h ( onl N n i nJJ, h ,lflH >tlulin~ .u

48.

HANG RATIN G PROGRAM

55 .

CLASSIFIED AD VERTISIN G

c; ROlJNl) <;)l;.l 'v\1\.\U,t 1, 1>1Jh lhhed l11r h,rn~ l{hd111t,:

11 v1l1l'' II 1h,· m.111•11.,I hr.. ht• rt•tumed. ,, 'tl,1 m pt•d , "'.. lh1tld1f',,etl •l"htrn ,.. m,•lo~,c IHLl\1 he t>Ut lo ..t•d C~OlJND !>KIMMl l~ tt",<.' 1\JC'\ ttw t1Rht to ccl,t t.011

1r,hv1mn, wl1cn" nece),.,,y. l"he1\,.,ol1.111or1 ,,od put,. he ,\llon cfr, n m ,f'l,u nw ,c•,p11n-.,h,l1tv lor 1hr.· m ,11(· r1.1 I m IIJ)IIHUR) u l t.on 1u hu11,,.., C ~Ol/Nt> \~IMMF~ " pul>l"lwcl """"hly h\ 1he Untll•d ~ t ..ih'" I IJo~ C lid111~ A,,ol •Jlio11, Int . whu,t• rn.,11 1111-t ,,ddtt'"'" , , P () Bo:.. hf) Hlh . I u, An)(c·li.."',.

c..,lfl CJOO<>h ,•ncl who.,f' oll ,n:-, .ire loc...i 1e d ,II

11 t l .! 1 , Vt-•111tc• Ulvd , l ,h An~t'lt..., , l.,1 11 900(,h , tt.•l 1•1)hone 111 O l91J Wh5 ~t.'(,.1UHI r l,1), po.,l,•JW ,, Jl,tld .1t lo) An~clt• ... C .11 11 CKOUND !-. KIMMl:K ,, prnllNI IJv S,ocl,111 P11n11n~ & t ,1ho, 1\lh11mb1.,, (..d 1r

<iuh,c nption" .1v,.ttl.1hlc Qnly ,,, p .irt Qi nwmlu~r, h11:. ,n 1hc.1 l /~1 t (~A. ,, 11)t.•m hl'r ·<0 1·11rolled t•1 l11tdl1cm,1l .u11I 'lc.1entu 1< o,~.111 1l,llt01l rlr:d11....t1t•rl h> l''<plon n~ ,111 i.u t•h 0 1 h n •llt-'>'>, , ,.. 1(.1,wnt h<'d uhr,1l 1g h1 fl 1Kht. Meml,cr,h,p " Opt•n IO ,rnvone ,nr~rt•..ietl 1n lh" realm ol th ghl. Due, Me\ 10 per yc,u (\ 11 l or fnte•~n ,uldfc_•, .. e,) OI wlu, h 1,4 Jre dt•'.)1>(1'1,1le<I Im ,ul,.,, 11p 110n 10 <.t{OlJNO ')KIMMER Ch,mJ,1.L'" 0 1 ,Hh lr,•..,

, huulfl be <telll "111( W 1.lc.•k, H'I <1d ViHlte, 11H..l1.ufHlK 1),lfl\l', USt IC.A rncmbN .. h1p nt1mhr1 prf'v 101,, .lntl nf'" .1.i . dre~,. J1ul ., nl..11f111~ f,tlwl tmm ,I recent l'>:.ue

Covrr· Cruism' Supine - Mike Huellcr, ~ailm;iker ior E1pper-forrn.inc.c, d i,plc1y, hi~ ea~y ~tyle 111 a cu~ lo m Cumulus VB . Da ve Cronk pho1ogr,1phed M ike', fli gh1 just before sun,e t at Pt. ~erm in.

rhem's a lot mor<cl lo selecting a n1an-~,erromn·· once glider than Just wl,ich one highclaims. It est or listening to really want to be confused Just compare in Ground Skimmer Magazine.

There's a better way . Now you can go to one and fly Just about any high-performance that interests Our weekly High-Performance Glider Clinic you learn first hand the difference In feel between bat1en tip and truncated tip gliders. plkh response, yaw Compare roll sensitivity, Inertial control pressures, and stall and landing characteristics - all Important points to consider. W<,) don't want to sell you Just ar,y glider. we want to sell you the or,e that's best for you. For more information call or write 1o:

Southern California School of Gliding Box

Van

SOUTHERN SCHOOL Of HANG GLIDING

Dear Editor, This letler will be of interest to anyone who wishes to power a glider. We have been working with the F.A.A. Van Nuys, and Washingin Los ton, D.C., and also with our congressman to obtain a waiver from I he requirement lo carry flighl instr111rients on bo;ird our powered Icarus II (e.g., fuel gauge, altirm•lr'r, ai i 11d icat or, magnetic: compass, tac:homPler, and Lemper.iture gauge). On April .rn, 1976, after 6 months of phone calls, and waiting, the decision reached through the E.A.A. Western Regional Office in Los Angeles, California concerning powc,red ers is: The following ilc'rns are considered necessary for the safe operalion of a powered glider: (1) an altirneter (2) a seat with a seat belt or a harness Fantastic! We bolh came to lhe reconciliation that in an ultralight aircraft of Ii miled range, instruments would be of marginal value and may unduly overweight the aircraf1. All of lhis has been made possible through the issuance of a new policy directive from D.C There is quite a fulure ahead for footlaunched, powered hang gliders. Chuck and Craig Catto Cupertino,

6061T6 (the tubing good manufacturers have used) is recommended for "heavy duty structures requiring good corrosion resistance" The aluminum manufacturers will not certify 6063TB32 as being of dependable strength. In the Aluminum Standards and Data Cuide, Table 1, "Typical Mechanical Properties", there is no endurance limit specified for 6063TB32, ("endurance limit" being the "limiting stress below which a material will withstand a specified large number of of stress"). Since the alurni num rnanufoct urers no enduram:e limit, they are not certifying that it has any particular strength. The 606.3Hl32 tubing has no workhardening rigure because it is not cerlain what are in it (it was described to me as a potpourri mixture which scrap alloys are sometimes put into). I was also informed that 6063TB32 is sornetimes m,rnufactured by extruding thmugh a spider or porthole die (6061T6 is never made this way). This method of manufacture causes a seam (usu;JJly unobservable) called an "extrusion seam" described as "a seam in tube pipe and hollow shape resulting from the pressure bonding of two or more edges in the course of extruding through a spider or porthole die", thus constituting a weak point in an already inferior grade of aluminum tubing. So, what 6063T832 is is a tubing with ( 1) no or reliable strength; (2) no consistence as to the alloys which make it up, and 0) often a tube which has an unobservable seam.

Dear Editor, I was very upset when I discovered that many hang glider manufacturers have been using a tubing which is completely unsafe. The tubing is 606fffl32. According to the Aluminurn Standards and !Jata which is put out by the Aluminum Association (representing all of the rnajor producers of aluminum in the United States), the recommended use of 6063TB32 is for "pipe railing", whereas

You rnay think that only small-time hang glider manufacturers would use such an inferior tubing, but at one time many of the major manufacturers of hang gliders were using the tubing (it was less expensive than 6061T6). Sorne manufacturers tried to get the others to stop using 6063TB32, informing them of its Bui most of the rna 11ufact urers continued to use the tubing, de .. ciding that profit was more important than How can a hang glider manufacturer sell you a glider made with tubing which the aluminum tubing manufacturers will not even certify? (continued on page 6)

JUL_Y, 1976 4

•

Contributors tu lJ,S

h,nd

Ji111 CIPaveland, l'A John KPrnndle, NC r,,rry rhrnn,i,, VII Bellina Cr,ry, W,1dley, C:/1 f'rice, W/1 Larry lliehl, Ml B,illew, MO MuellN, I,\ Awdli,mi, NY J, lr,mk Sharp, Ralph Roun•;avall, John Norman, WI

WL Wdym' Douglas Kevin Fuchs, MA John Strei!, Al Desdwn<', MA flluestorw, MA Jim Coff, Michel Fredy, l A

forn Laµpas, C/1

Dail' I oration, Cnald Uoyle, PA Alex Dunc,rn, Cl\

Fmery

Southl,rnd I Jang

Murrdy f·vt1ns, Will llattlr,s, CA

Lastc•rn PPnn, H.G. A~,sn., PA

Chart,,, PPPr St1hr CA Ji1n Kickrn,:1n,

Mike

Mike Buchanan,

lord W<1lters, CA

I arry Arndt, Ml Toni Pelett, OR Rolwrt Boellner, NY J,rnie•; Willi,Hns, NY Louis NY

Clt,n I Pwis, AK Jimmy Hibbe11s, /\Z Rod Cuidry, TX John Ritter, f>A Nathan Waddill, CA Lee Shurie, CO Mike Pierceall, IL Dan Poynter, C:A D, Menges, Vern Roundtree, W/1 Dave FrPt~mcH1, WA Don Dearth, CA

f onin Meck,

Sterling Stoll, CA ChMles Ashford,

David Cuth, WI Rod Schmidt, Harry [arls, OR I !ecly Daniel !\imar Matlano, Argentina

UdVl(ISOfl, CA Bur·rni11gham, CA

Leonardo deWitte, CA Fd OK Jarnl's NY Neil Ormond, TX Sanphillippo, CA Ralph, M~ Joseph Lopex-Lewis, C/1 J,R, Mclammany, PA William Kamp, NY I arry Witherspoon, CA John Welsh, CA Ruby, KY Labrie, ME Earl Hanson, NY Ken Mannion, WA Waridkois, MN Lewis, IA Bruce Reubert, CA

Lewis Billings, VT W, Rhett, CA P,wl WA Mike 13or'ko,wsl,L IL

Ulltr,aliigt,t Ci:.H"IVersation conlinucd Blueprints Now Available

Some manufacturers are still building hang gliders with 6063Hl32. Many have only stopped using tho tubing within tho last six to 12 months, so your good old hang gl idc:_r may boon made with 60(dTBl 2. I suggest you chock. Mark Buckley

Dear Editor, VJ-24 Sunlun • Airplarw controls O All metal, except fabric. e Easy to lx1ild. • Semi·-cantilever, monoplane hang glider. • Send $2 for brochure.

VJ-23 Swingwing

In reference to Mr. Allen's article in the April issue of CS, page 20, not all of which I agree with, I would like lo make the fol·lowi ng cornrnenls. I) Since this world is run on mo1wy and not virtue, it seems patently obvious that if this sport is lo wrnain alive, it is the man· uLictu rers who wi II have to shoulder much of the respo11sihility. 2) I IMA Members rr111st sci mini mum standcird requirements for dealers ,rnd man11fact11 must b(: willing to jerk (ka if the dr>,iler foils to 11phold them. 3) U.S.H.C.A. should lw rqlrPsf'nled at all I IMA 111<:eling,; ,1s tlw co11su111er's watchdog, and reports in Crounc/ Shimmer should serw as its tC'eth. (This should be

• Has been soared for 42. min. on :34'-r1igt1 hill, 23-slope, 17 mph wind. • Takes off and lands in 2 steps in a 15-mph wind. • Fully controllable in 3 axis. • WorlrJ's first high performance hang glider • Send $2 for literature, 3-view, and color photo

TWO GREAT BOOKS ON ULTRALIGHT FLIGHT

done before the Federal Coni;urners Advisory Age11cy gets involved.) 4) High performance gliders should he serial numbered ,rnd ,111 owners log kPpL This might insure thc1t the prPsent owner is [JUalified to fly it. .'i) I agrt>c with Mr. Allt>n's observation concerning tlw l,ick of "commercial in· cc?ntivP for giving lessons after a hang glider ha, been sold," ,rnd for that'reason dealers should he req11i1HI to show that ,ill s,1les of glick•rs were made lo qualified rated pilots. This could be h,rndled by the HMA and over.seen by the LJ.S.11.C.A., with cooperation from qualified dealers. 6) M,1nufacturer', should realize that "fly-by-nigh!" dealers do more> to harm the reputation of tlwir product in the long run. rhese "dealers" ,1lso make it hard for the more sincere de,ilcrs to s.iy alive, lei alone build ,1 husi1wss. 7) Mr. Allen of a11 I IMA officP pro)?/'1111 hy "levying ,l t;ix" of "just $4.00 per glider." I don'I beliPw th,1t would he an equitable solution, since the eight compc111it•s would be paying the mdjm sharc> of the cosl, ;ind not deriv·· ing proportion,1te benefits. I .im surP tlH'rl: is a way to do it f,1irly the point ·1s to work logellwr ,rnd find it. ll) Now to deal with Mr. Allen's call for FAA help i11 "healthy and hones!" regulation. Since wlwn hc1s bur(;;111cr,1Cy bec,n ,rn aid in keeping <1ny1hi11g healthy ;rnd hon· est? It will 11wrPly ,iccei<'r,ite the gmwing cost ,rnd of our sport bt'yond th(' point of lolera11ce. J.iy Raser Missoula, Montana

De,H Editor, on foot launching. 6th revisior\ over sold. $5.95 postpoid. (Cali forr1'1ans odd.36¢ soles tax) 200

VJ-11 So-lo • Build the world's first fully controllable hang glider. • Standard aircra/1 controls. • Fully engineered. 1111 Can be built in 6 weeks spare tirne. • Material cost approximately $400 • Send $2 for literature, specifications, and photo

Plans & Bror:htm:i::;

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VOLMER AIRCRAFT OSK AIRCRAFT BOX 5222 DEPT. G 14547 ARMINTA ST. GLENDALE, CA. 91201 VAN NUYS, CA. 91402

Write for FREE hang gliding information kit. Dan Box 4232-96 Santa CA 93103

Last December I wPnt through tho flight school al Fscape Country, and was instantly" hooked" on hang gliding. I rented ;1 kite from Country for a day and decided it was time lo b11y. To make a long story short, I purchased a used lknnelt Phoenix VI from ,1 11,mg 4 pilot. With six minutes total flying tirne, I wc1s a "turkey" ,1nd knew it. So, I spent about 16 happy ho11rson the training hill lc;irning to fly this Mr. AIIL,n's ,irliclc 1m1chi1w. Afler in Cmund Sl<immN (April issue, p,1gc )2), I can understand why most hang glider manufacturers have rJli11g rPquirements for their high 1wrformann, kites. On lhP other hand, I ec111 unders1a11d tlw position of tlw hegin1wr who doe's not wfsh to spend several hundred dollars 011 ,1 glider ho may outgrow in a few monlhs. My biggest problem in learning lo fly the Phoenix (continued on page ll)

,JULY, 1976

drnq issue o! Ground Skimnwr)

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Conversation continut>d VI was setting up a landing approJch. The roll response did not present the problem that I had expectl!d. I might also add, after omparing the performance of my Phoenix VI with that of a standard, or even an adv<1nced sl,rndard glider, my decision to buy a high performance glider is one I wi 11 never regret. rlw F.A.A. separates pilot ratings from specific aircraft ratings ... why not do the same thing with hang gliders/ The same hang rating system for pilots could be used in conjunction with a separate class rat system for a fie glider. forex,1111ple, ,1 manufacturer could dPcide in which clJss out of thn!e his particular make glider would belong; or perhaps, each glider class would have a performance and/or d parameters. Most manufdc. turers and dealers h,1ve LJSHCA examin· ers, observers or instructors on their staff who could judge a piloi's competence on a demonstrator kite of the same make lw wishes lo purchase. When the pilot per· forms the required rn;uwuvPrs, sm:h as linked S-turns, and lands within d disl,rnu· from a target, a glider class rating would be aw;irded. This systPrn would apply to all h,rng r,ited pilots and would benefit the 1.wginner and expert alike. Fi rsl, it would ,illow ,1 beginner a chann' lo lw rated in the class of glider he wishes lo this system would prevent Joe Hotshol, who has flown a sta11tbrd glider for the last lhree years, from buying the latest superkile, driving lo the fll;.ire,t '1,000 ft. rnounLlin, and his lasl flight! I wish lo congratulate Mr. Robert V. Wills on the fine job he is doing with the difficult task of hang glidc·r accident investigation. I hctve one question, would ii be possible to nwntion the frequency which the pilot has flown in the preceed three months before the accident? Pilot currency played an irnport,1111 rol(· in flying s,ifety during 1ny military days, and it would seem th<1t this could apply to hang

gliders as wPII. I rea I ize th is would be very difficult, if not impossible to ascertain in every c,ise, but over d period of time this data might the pilots an ide,1 how often we should fly to remain safe. Also, this data could bP 11s(·cl by tlw USIJCA lo Pstahlish currency sta11cL1rds for their r,1ti11g pmgram. llarry Frazier Huntington BeilCh, CA

Dear Fd itor, Recently, a friend of mine returned from thP west coast and told me .1bout the gre;1t time he had. One thing he brought to my attention was teaching methods used liy west co,1st schools. ApparPnlly one of the most useful tools we have here in the Nmtheilsl has not made its way west ye1. I !ope· fully this lelter will go far in increasing the awareness of this simple and inexpensive training aid. rl1e "Tu St as we know it here, w,1s introduced to nw at the CSI Instructor's seminar at ML Cranmore l;ist summer. Very simply staled it is a length of cotton cord, approximately to 40' in length, that is ,ittached to the top of the king post of your tr,1ining kite. As the student sl,irts down the slope the instructor follows, paying out cord, hut alert 10 it (wear a glove) in case a student starts to dive in; thereby turning thP much dreaded "stunch" into a harmless sit· down stall. Practice with a good pilot lo get used to it, so you know just how hard to pull back. Before, you know ii you will become sensitive enough to ch,1nge the angle of attack so that the student can conlinw" gliding safely to the bottom of the hill. Check it out; the dollar spent on cord will conw back many times when you consider wear and te,u on your equipment not to mention your students. Jim Aronson New York

Dear Editor, It seems to me that the most dynamic as .. pect of lo activity over the recent past, presPnt ,ind the forseeable future, is that of With so much bei achieved in terms of irnprovemenls in along with performance, it seems undesireable that ;1 standard class rogal lo concept as we cur rently should have any part in interna .. tional competition. The design limits are at best arbitr,uy and ,1t worst unhealthy in the sense that there is an incentive to build a rule cheater. Assuming !hilt one of the rn,iin oiJ .. of the standard rogallo class is to provide level pilot skill in competition conditions, the better way to go would be lo have settled on one rigidly controlled con .. ical and allowed for variations in wing loading only. What I would 1·eally likP to see h,1ppen is this: a standardized sys!(!m of tciliulating a mg.ii Io's vital st,1tistics be formulated. At all rnajor contests over the next two or three years, the vital statistics of perhaps thl' top scoring four gliders in each class be recorded with the eventu,il a i rn of forrnuL1ting a mean· ingful and work,ible systern of giving a glider a rati11g. llopdully it would then be possible to operate a foir handicapping systern. There would thus be accurate pilot skill cornpari .. sons without any darnp('r on glider dPvelopment. At this stage in hang glider development, it is crazy lo promote a situ,l· I ion which places any rest ric1ions on design. Isn't the altern;1tivP of stimulating de· vPloprne11t a 11111cl1 b(,lter one/ Rick l'oynte1· New Zealand

/lave on your mind? CS welcomes letters lo the editor. Please address your letters 10 Crouncl Skimmer, 'In USI/CA, Box 66306, Los CA 900b(i.

LI $700/Set Complete F'.0.B. San ,Jose (\1l1forn1M)S ,Hid (>'\. s<1le~, tr1x

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,JUL.Y, 1976

Keith Nichols, flying the n<!W ASC-21, led the' '76 Nal ionals Open Division at Dog Mt., Washington. l<('ilh, who hc1s been flying ,rnd working in tlw hang gliding industry for 3 V, years, h;is enterPd very few cornpPlitions (he, once plJcc,d 291h al Telluride). HP has mixed emotions about competition, and ,1dds, "l'ersonally I can do wilhout competition. The most enjoyable flying is getting logeth<'r with friends and pilots who really fly well. Rut compel it ions are i rnportant con1111er .. cially because they force manufacturers to improve and all the pilots a chance to see the new sluff and old friends." Now th,1t he has a competitive, high performance glidr!r, he will proh;ibly be entering more meets. To begin with, he'll be with the ll other U.S. Tearn mc!mhers to ll!present our country at thP World Mee! in Kosse>n, Austria this September. fhc ponytailcd, bushy bearded pilot is known to m,111y as THE nice guy, gu;iranteed to provide you with a chuckle. He is a sailmaker (with Albatross since its beginning in I 973) and an artist specia I izing i 11 si Ikscreeni ng (remember those blue-on-gray Otto

Solar Aircraft Corp. is hang gliding towing ;1ccessmy for tlw 197b Summer season. It is a sophisticated bridle sysll'm lhal can tow a ider up while continuou,;ly adjusti11g the tow point. This maintains the best of attack to the air until the dcsirf'd ;:1ltitude is reached and the aircraft is released. This patent pend system adds a degree of con1rolability sirnilarto the power of an automobile. Pulleys ;ire used lo olJ. lain the mcch;:rnical advantage. l)reviously, hang glider towing had been accomplished by placing the tow lines a1 only one or two points on till) glider frame. This allowed only om' ,rngk o{ att,ick which could stress the glider as much as 400 pounds at certain angles. The Solar

Lilienthal Now a partner in Alb;itross Sails, Inc., J<eilh is in dwrge of advertising and publ Albatross was exclusively a sailmaker until although they have built and flow111hcir own gliders. have resca rclwd and perimented in glider for ycc1rs, and four months ago production of lhe ASC-21. l<eith describes it as 116° nose, 2B° sweep, with an aspect ratio of 6. He is certain that his isoneoftlw highest perforrningglid· ers to hut doesn't w,rn I to get into stat istics hec,wse there is no 100% accurate measurement as yet. He is working on electronic: instrumentation which would provide accurate perforn1ancf' statistics for hang gl idcrs. Congratulations lo Kci1h, along with l~ob RePd (Standard Cl ,iss) and Ken Kuklenski (Unlimited Class) for 1heir excellent flying in the Nationals. Note: /'or com/)fc,;ic results of the 76 Nalionals, see page Photographs and de tailed account of IIH' meet to lo/low in the

CS.

Hcltin,1 Cray

John Lake, USHC/\ Vice President and chairman of the Cmnpelition ComrnittPe, has just t,iken the position of Vice President and Cener;1I Manager of Wills Wing, Inc. John's contributions to hang gliding have been rn,1ny. he served as USI IC/\ Flight Director, and directed the '7 4 and ' Nc1tionals. He authored tlw I Lrng Rating r>rograrn ,rnd originated the Otto Lilienthal Awards. He is also a contl'ibuting author to CS and i nvc\ntor of the Sai !feather. Congratul,itions John and Wills Wing.

Ed.

floating bridle' adjusts lhC' tow to literally hundreds of points or during the climb. This !he glider at the smallest of att,ick 11eccss;1ry to gain ,iltiludc ,ind stresses the glider only 50 to pounds in order to do so. Since )u1w 1975, this new sysle111 has hel'n tested in florid.i, Tennessee and Michigan undPr ,i grPal v.iriety of condi. lions. First tcsled behind boats on the waler, it has ;ilso lwen flown behind c.irs and snowmobiles. The system was in an effort lo make tow hang gliding safer by adding controlability and relieving the great amounts of strf'ss that wc>re occurring. ,r·:i,t""" ,rnd further information are ,1vailalJIP fref' from Solar Aircraft tow ers 1416 Williams Street, Chattanooga, TN 1740/l.

,JULY, 1976

Thl: f i rsf 11,11 i on.i 1111 sf n1cto I Cc t'! i fie at ion l'rogr,im wds sucu",sfully held dt lus, canit ki .irc,1, ll10mpsonlow11, l'A, MMch 2h-21L This was liy lk with lhe aid of l),ivc Stcirhuck, and llill lllwood, Tht('l' of in!Pnsivc• ,111[1 !(",ling look rcsulti11g in I a pilots tlw cours<', rlwsl' will rc•n,ivP th('ir ll.1sic [n,;trLH tor cMd ,rnd will IJ(' allowed lo for Adv,rnccd Instructor ,1 yr•,11 lwnn•, rhc n,rnws of tlw new instructors will l1e islwd ,it ,1 ldtl'r tirnc, c.01rmlc•tio11 of the first ,1id cours(', lhe schcdtil<' iricludPd le,H h,i11s 011 ""''"'" ra11gi11g from to thP lc,;rn1ing process, '.'iulJS•l'(lllt'llt ing pr,1Ctice ,lllrl testing was 111c1dc more difficult by the [H<'sc,nn• of S<'vcral pilot<; ,,oMing I 000 fod ;ihov<' the program ,11e<1 i 11 Ii P ,\ u ti f u I co 11 di ti on I Io we v er, everyone the course Wd', rewa nlPd hy gaining mu ch insight ,md Pxperi(·ncc i11 ti)(' lield of h,111g gliding in, ,,trnctio11, hard work l'l1d(•d with an l'V('l1ing filled willi d flock of hdppy, certificd!ed instructors, Cl<!ANMORI, NORl 11 CONW/\ Y, NIL A comhim'd c;s1 ,rnd l.JSH(;A program took M,nch .lll l I, Over l() te<;I the course·, i testi11g of tc•c1ch i ng ,111d ,ihilily, Jlw org,111iz,1tio11 of the program Ml

service to

(free) informdlion your wing

with your .idt Ires, and p/1onC' nwnher,

m1 May 4, lftlw Pntire kite-, or even the sail is rc•turned !here will b(' no asked ,rnd the person rel the kite would be: t lw sport It 1elior1gs of t lw sport's

rllis kite was stolen at

GF10LJt'10 SKIMMEF1

w.i, h,rndlcd liy Don McC1be, li,ti11 1.; tlw .iid of /\I Mul;i i, l'c111 I.ii ilicrte .ind I )enr1is 1';1gc·n ,is grou l(·aders, l ,ilb wen· prescnll'd hy Swc·c11y ,rnd lony Velhurst as well ;is optional first ;1id course, !lying w,1s only OIH' but tJii,; w;is ',uffic:iPnt n,nn,lntn the testing of this ph.ise of progr,1111, Much infor111,1tio11 w,is irn to ,ill p.irticip,rnt,, including the Ccrl,1ir1ly, this cvP11t will ill' ,1 model coursl' 011tli1w for future ccrtific,1t progrc1 rn•;,

2-4, Fireworks! 2nd Annual Fourth of and meet at Caverns Ch,itt,inc,oga, Tennessee, Call (6 l 5) "Suds in the

Fly Alask<1 Ai dine An!:horage, Honolulu, $30l.l.

rnembcJrship rm!eting,7:30 P,M, DepL ,iuclit<:1riL11m, 111 N, Hope

9-11, 2nd Annual Molsorn, Invitational !Jang c1! '1100' McKay, Thun-

Glider der

For

26, Sl1GA l1'1i',mbcmhip meeting, 7:30 P,M, Dept of Water and Power auditorium, 111 N,

l·lop1c1 St., Los n"""'""'

J1111c Cenc lllytl1P, flying ;i Phoenix VIB, took orf at l'.1rkcr ML, a popular 1,UOO fL site nmth of Los In I 00 I 0 he,11, ,rnd mild Santa Ana wind coridi!ions, Gene reports that he 11scd strong thermal lift the first I miles of the flight He then c11, tered shear ue,1lcd by tlw coolero11-shore flow forcPs with the intense desert off,shore flow, At one time, Cern~ was flying .it a cold 12,000 ft, /\SI, having g;iined llBOO' above t;ikcofL rhc shear l,xl south into the San l(•mall(lo where he eventu,illy l,rnderl rn1 <1 couN' just south of V,111 Nuys Airport Congratulations, Gene!

spent two months of hdrd work in"~'''"''""

11w sail It's ollvious that whoever took it can't r·vcr fly it ,is it is ('asily n!cogniJ'e,1ble and very The kite me,rnt a lot lo /V\('rHlij, ,rnd he is very discouraged that Wl' hcivc this sort of h,ippening, f'l('ilSP return the kit(', Call John Davis at (21 l) 64 l-7-4(>4 or (21 l) ':l7l-'j()J ;> if you want lo return it or have any infor., mation ,is to its whereabouts, I'm •;urc would be willing to p,iy a rcwdl'd

IV, missing April 30 from owner Ashford's home in l)ortland, OR, Col, ors from keel p,mel out .ire purple, orange, lime, purple leading with orangc, It is wired for seat, and the seat is and covered with imitation leopard cloth, The cover is red cordura, with twist snaps, Roth kite and cover are very clean, I ike new, Contact Craig /\sh ford, 2604 N ,E, liht, Or, 97213 ('50l) 2ill 14/l4

a, SIICA ,,,,.,nl""H'<hin rne1,1ung, 7: 30 P.M, Dept au<1ilciriu1m, 111 N, Hope

Gliding Meet at Crystal Cav(1rns Tennessee, For 1321°0097,

Telluride Invitational Meet The nw,11 will be an HMA sanctio1ied meieL The pilots will be chosen from and this group, Th,i T,illuride area is closed to for the i11vitatiom1I flyors during tators welcornE), 19,2 l, 3rd <.111< ,,,,m Lakefront Festiv<1I, Delta GI ider Cl1,amoio,nsl1ips, Contact Harry R<lbb, to Apt, Q-203, Clearwater, Fla, 33515, {1)13) 23, SHCA mtieling, 7:30 P,M, Dept, of Water and Power, I '11 N, Hope St, Los

SEPTEMBER J, I

First World Championfurther inttirm1ati,on, Kossen, Austria. USHGA, Box 66306, Los Angeles, CA

9()()(,6,

9, SllCA 1rnm1ber$hip 111t:''"""M, 7:30 P,M, Dept. of Water and Power 111 N, Hope St, Los Angeles,

World Cup, Dolomiten, Italy, 20°26, Harker World Cup, Leysin, Switzerland, Park, rh"n""'''"''" formation call

25-26, Crandfather Mc>un1ta1n

me,mlJershin meeting, 7:30 P,M, Dept of Water and Power auditoriurn, 11 'I N, Hope SL, Los

IFI The Alpine is the product of o 10 month cte,•elc,pmenl high perform once soaring glider, Alpine stall, and virtually no yow from its unique pre-formed cambered battens prevent soil inver!icms and maintain the of the modified Wortman/Murray sailplane airfoil throughout the gliders entire speed tnmcoted tips, on oirfoiled keel, double deflexer.;, and the patented wing make the soil draw up tight during set-up to provide o "stationary" wing, yet fold up quickly and easily in 6! minutes too Rogol lo size bog. The cross-country success of the Alpine lies in ifs obility to hove on extreomely low minimum sink rote and o high L/D ratio. This allows the flier to core light thermals in o tightbanked radius lo gain altitude, and then achieve o long flat glide to the next lift zone. The L/D deteriorates very little over o wide speed of 10 - 50 MPH, ollowing the pilot to of altilude. In ridge soaring conditions, through ttirbulent air without significant will soar in virtu,1lly wisps of wind, and the L/D will allow you to crass ridge gaps loniier flights. The Alpine: A cross-country soaring machine designed lo be used as o If you ore a proficient flier, perhaps you should further investigate the Alpine. Pricing and further information ovoiloble by request. Please include $1 .00 to cover postage and handling.

· SAN CLEMENTE· CALIFORNIA· USA· (714) 49r0670

mode. With on L/D of 6: l the or expert because <,four variable airframe. Our extruded wing slider and riser system allows variable soil billow and our custom reinforced stainless channels allow control bor reflex and seated or in sewnds with no tools. ball-lok on usage. All hardto insure foil-safe and tested for hong rJI Pacific Gull cmd meet or exceed all HMA All units ore test flown, balanced and come with on extensive instrudion book. A detailed seven page brochure with soil cloth color and location of our nearest available for one dollar to cover postage and the most versatile

is suitable for l'he

DAVE KILBORNE

Researched and Colver Instru· mcnts in conjunction with Wills Wing, Inc., the Colver variometer is a dual range audio and visual vario· meter that offers ail the features that the best It is a must for optimum 0

•

DAVID CRONK

GARY THOMPSON

STEVE WILSON

JOHN McVEY

Audio and visual for total flexibility. Dual sensitivity for even the most marginal or extreme conditions. Super sensitive audio for the quickest possible response to lift. Damped visual for easy reading and a slighr effect although it is still quicker than the best sailplane vario· meter. Proven circuit in production for over 2Y, years. Entirely self contained with no exterior bottles or flasks. Visual may be separated and mounted separately to adapt to ,my design. Audio may be turned off for visual use only. Shock resistant. Streamlined for minimum drag. Extremely lightweight -- only weighs 33 ozs. Built in mounts can be attached to any control bar. Low power usage insures long battery Iife. Can be adapted for use with two visual guages. Distrilmtcd exclusively by Wills Wing, Inc.

Visit your local dealer for a demonstration or write to:

Price

THE BELL SOARING HELMET IS AVAILABLE THROUGH YOUR LOCAL BELL DEAL.ER. Distributed world wide by Eippor-Formance, Inc, Torrance, CA 90501

A to 1 MPH 2!\0-260'/Min MPH 40 + MPH Excellent Excellent Excellent

Area

AIR Keel Exc,~llent Excelkmt Excellent

Root Batten Cord Dry Weight

figures

170 Ft" 5.28 12'0" 19'0" 11'1" 30'4" ;37" 401bs.

190 Ft2 5.38 12'0" 20'0"

11'1" 32'0" 27" 41 lbs.

approximations and derived from pilot extrapolation and comparison to other claimed figures. characteristics and target hitting potential without loss of L/D or sink rate the Sun Swift was chosen unanimously Team.

To order your harness or for more information write or call:

SUNIJIRD GLIDERS 21-420 CHASE ST. 7J CANOGA PARK, CA 9U04

(2U) 112-3117 1o

Please specify pilot height and weit1ht when orderinti by mail, A minimum $20,0C) deposit must accompany all mail orders, ONLY $65,50 f,o b Canoga Park, Californians add 6% sales DEALERS INOUIRIES INVITED

•

STEP IO"'RAc::r1cE

All English leather with ankle for support and comfort. shock absorbant sole to cushion hard landings. Rugged tread design for maximum traction. lace anchors that cannot hook in wires. leather tongue boot waterto the very top. Sole to hook and hold harness stirrup. with soft leather for a per-,

Send American shoe size to:

sizes are slightly

TUR.1'sJS

%>AFE:ry CH!CCKS

FOK'. TI-\E: ltvTERMEDIATE PILDT RID&1:;;:; HA~G RATll'-JGe,

ll,l-U9T'RATE-D

• FL,IGHT LOG 5H\2£,TS

Walnut Street Price

fHiH

822WKJ\T l.LJ\J\V OHJ\NC; , CJ\. ~J2(ifil frlr,1)i1rnw 17141\JD! 0/01 Momh1H of Nc111glicler Man11fact11rers l\ssociation

Manufacturers of DUALITY kites

anrl components DEALER INOUIRIES INVITED

A TTEIVTION BUYERS 11s {I /l/{l/11/flll /11/'i'( of (f/i(l/itr glickr

!111rcl1w1r!' 1111<1 11,jt\\'llrc \\'/' 11·ill he /i{l/!/1]' /0 !/110/1' i/111111/ ii I' /!ii('('\ Of 11'1' umT ()\' /1.,1\D a large i11r1·11tor1' of .11a11c!-

11111' .\/)('ci/ica1io111·.

11nl /!/Ir/.\ ail// 111111,!ic1

ll'ri!c m

87107 PHONE: (505} 344-3444 SEA WORLD photograph used SEA WORLD® is a registered trademark

In Yosernite it is not unusual to see people their necks looking up1 ward. The 3000 cliffs that surround the seven mile long, two mile wide valley dwarf the tiny 200 1 pine trees below. But there are times when everything in the valley stands still. Hikers stop, go to the river banks, roll to the side of the and every motor vehi-· cle stops where it .can so that the mes-· merized rublic can look up toward 1he 3150' cliff where l1c1ng iders are launching and dotting the The spectr1tors can't really attach the reality of a human being to the tiny ;:ind graceful in the hut you can, because you are banking your glider across the Vt'rtical of Clacier Point. You're still breathing hard from that first t;ike.-off from the of the world. It'~; how the ground just seemed to drop away from you I 01 1 50', 200', and finally over half ,1 mile. But now you arc caught up in thP sheer natural beauty that envelopes you from all sides. Yosemite Falls fractures the rays of the morning sun as it wakes (rorn its resting behind Half Dorne creating a million little rainbows for which the hang glider pilot has the exclusive vantage point. Yourdist;rncc1 frorn the valley floor miniaturizes the trees, buildings and cars. are too small to he seen. All the intricate maneuvers you had planned for the high di titude flight wert' left on take off as you spend your 14 minutes of fligh1 looking ,1t the I ivi ng painting from an that few people a re privileged to nv,..,,,,,,,rwn You notice that you dre talking to yourself and to keep from shouting out loud how you feel. Five minutes into the ii ight your face starts to ;iche because you can't c;Jop smiling. Now, over the landing area at 2000 the air is so smooth that you can for the first tin1e really check your kite's handling, and you begin lo wonder how many 360' s you could spiral off before landing. People n to appear beside the housps ,rnd cars. You don't want to come down, but the lack of thermal lift in the early mom i ng rnakes it a neces· In foci, you are rapidly approaching the tops of the your landing ap·proach mc1y be your but you can't I The meadow is about a quarter mile square, so with the cool early morning sink in the rneadow 1 you

moo'

just pull it in at treetop level and come in for that final ground skim to a landing so soft that your feet do1/t even leave footprints on !he thick long meadow grass. Two little old rush out to ask if they can take your picture to show thP folks back and you are still so naturally from the flight that you couldn't care less. up your kite, you see your friends landing around you and you can the same thing in their faces that you feel in your own. Nothing needs to be so you just stand there grinning at each other Your flight in Yosemite was the result of a lot of hard work and the

support of petition like the two little old ladies. The support came from both fliers and alike and we can all be proud of the efforis put forth. Dean Pasd1,1ll 1 the Glacier Point ranger, and a glider pilot, is one of our leaders for the cause of flying in the National Parks. Through his program of moderate regulation, there have been over 1500 flights off Clacier Point to date, and the worst injury was when one person had five stitches in his knee after he took off straight into a tree. (Quite a feat if you take a look at the excellent takc .. off The fact that the main controversy centered around the ble of Yosemite to flying last JULY, 1976

it Lli

Pvidt!n! l hat

ing them out of thl' rninirnizes the Pxposun.· of the 1r1padow to The record for itself, but still have lo be cautious of any could be a very for visitors and a kite go in from 2000

one th,it the

cre;1te minimum im 111eadow and the nesting bi1·ds of the The t1kc,.off and landing sites have c;irefully studied to insu little i ble is

th,1t as on

The occurs when the spGC·· lators 1ush into the meadow to the descending pilot,;. The I balthe rneddows is delicate dnd c1tors, ,is in near icipants, and in doing so lmrnp out and group c1round the kites I Ii out in th

media

meadow liefon, nglht•contml bar nd then ng it down on the h. !his combined with the tlw kitr,s ,rnd mov··

in Yosmnito National Dea11 f\1scl·1all, record, A do1e11 from the 31:'iO' cliff.

!his is rernents to fly ,il Yosemite arc so stiff. If you want to !al«· chances wilh your own lif<:\ don't do it when:' ii us lo lose flying at our most beautiful site. of the rules and that

of us !hat to kill ourselves or for othc!rs. If you only fly bdore B:30 what do you do for the rest of the Yost>rnite has d t1·ernendous number of recreational activili<~s !hat are avail.ible to Pveryonc from the weak c1t heart lo rnosl To mention ,1 few lake or river fishi touring, float or noe, raft, mountaineering frorn (Lloyd Price, the di

flies an Icarus V), horseback rid and you 11 your 11, join the rnounta i nccri ng from ll· 0 to 11 on El Beach the river until 1 :OC\ raft down the river mirror to El until :00, go trout fishing to catch your sup per Pri or Dean Paschall cm lei I you the b<ist then go back up to your neilrlhe oi tinel Dorne lo cook the trout u11der tl1P million stars that flood the Yosemite at n Then as you st1·etch out in you1 ng you can watch the shooting stars that decorate the black patch of the pine trees. hJr those who want to more in, the area around Yosemite offer·s eel lent wi lderne,;s flying. There's Red

Mono

of ways to YosPmite Val whdher· you round out your strenuous climb up Half laze around the riverbank. Chances re, thougl\ nothing c.111 the of your arly morning fli Clacier Point.

STABILITY OF

TAILLESS GLIDERS

Ill ..A ~ ~~~

BY STAN HALL " Tailless aircraft may indeed have a future in hang glidin g - if we adopt the concept with our eyes wide open." Mitchell Wing ---- Photo by WA Allen

A few sprin g afte rnoon s ago I stood w i th a few fr ie nd s atop Northe rn Ca l iforn ia's Mission Ridge, wa tching Dr. Howa rd Lo n g launch h is new M itche ll Fly in g Win g hang glid er. It wa s an impressive sight, in deed, one which moved Steve Patm ont, stand in g alongs id e, to remark, "The taill ess air .. craft may have at last found its pla ce -in hang gli ding''. I consider Steve's remark most perce ptive because we' re beginning to see more and more ta il less aircraft in our c hosen sport. And to date, t aill ess airc raft have sca rcely demonstrated a c lear potential for th e future anyw here else, mainly because th ey have so me undesira bl e tendencies. In spite of these tendenc ies, tai ll ess aircra ft may indeed have a future in hang gliding - if WE! adopt the concept w ith our eyes wide open . The tai l less airc raft has a number of things go in g for it that are not readily appa re nt in kites or in aircraft w ith tai ls. O ne, they are muc h more responsive to weigh t-shift in changing the speed and pitch angle. Two, not havi ng a fu selage or tail th ey can be built ve ry li ght in w eight, al though not as li ght as kites. Three, properly designed, they enjoy a portab ility that chal lenges the kite. And finally , tail less aircraft have better perform ance fo r less wing area th an kites , although

not as good astailed aircraft hav ing the sa me wi ng area and aspect rati o. These adva ntages bring w ith them, however, a number of potentially se ri ous problems which need be co nsid ered with a criti cal eye. And those problems are w hat t his artic le is all abo ut; ce rtainl y not with the intent of deflectin g anyone away from the con ce pt, but to remind th ose who are not fa mili ar with th e taill ess ai rcra ft that it is a different k ind of bird , o ne req ui rin g more than casua l respec t from pilots, builders and des igners ali ke. A nd i n thi s connection I am remind ed of an appropriate wa ll plaque I o nce saw in the pilot's lo unge of an airline. It read, "The sky is not inh ere ntly dangerous but, l ike the sea, is terribly unforgiving of errors in jud geme nt' '. This little homily could have been i nsp ired by th e tai ll ess aircraft because such airc raft are cons id erably less forgiving in flight than aircraft with tai ls - which are not parti cula rl y forgiving, either. The " problem" , and I use the term with but a pinch of rese rvation , invo lves the pitch and yaw stability at or near th e stal I. What is sta bility, anyway? Exp res sec! in its simples t term s, pitch sta bility merely means tha t when forced to fly fast, the aircraft shou ld have an inherent an d unmi stakeable te nd ency lo

sl ow down when th e pilot releases the contro ls or moves his weigh t b ack where it was before he started speeding t qj , Conve rse ly, w hen the ai rcraft is forced to fl y slowly, it mu st show a tende ncy to speed up aga in w hen tht>. pi lot lets go th e contro ls or moves forw ard to th e original posi ti on. Wh ere the speed stop s changing and se ttle s down to some sta bl e valu e, you have "trim" speed. "Yaw Stab ility" means essen ti all y the same thin g exce pt th at it refers to stabil ity in the turni ng direction instead of the nose- up, nose-down di rec tio n; o nce yawed in one direction or the o th er, th e aircraft should return to straight ahead, wi th no help from the pilot and with n o dawdling aroun d. Why is stability so important? W ell , without it, th e pi lot wou ld have to constantly sh ift hi s weight or apply th e controls so as to maintain some reasonably co nstan t speed and directi on . It wo ul d be like balan c in g a bamboo po le upright in the palm of yo ur hand, mov in g artfully thi s way and that to keep it from fa llin g over. And this wo uld take all the fun out of flyin g, not to mention the performan ce of the aircra ft. In turbulent air this cou ld also resu lt in some rather unsettling loss of control. An aircraft should be able to return straight ahead JULY, 1976

and to its prop er trirn speed all by itse lf, with no help from the pilot. And if it is stable, it will. Well, you ask, in the case of stabili ty i n pitch, w here do t he speed-up, slow-down forces come from? The speed -up forces de ri ve from the fact that the center of gravity (e.g .) of the aircraft is fo rward of its aerodynarn ic

center . ";\erodynam ic Cen ter"? What's that? The aerodynam ic cen ter ("a .c." in shorthand) is sort of the e.g. of the aerodynamic forces and mome nts -· and a "moment" is simply a torque. Back in the o ld, old days we didn' t employ the concept of Ae rodynamic Cen ter. It hadn't been inve nted yet . We used " cen te r of p ressure" in stead . You hear a lot of Cente r of Press ure in the shops and on the hills these days, but the te rm is rea lly pre-WW II. Du ring those ancient days we exp ressed th e fo rces on the w i ng in te rms of the amo unts of lift ;rn d drag th ere were and where the ce nter of pressure was, because the cente r of p ressure was where the forces were assum ed to act. Si nce the center of pressure norn1al ly moves forward as the speed increases and aft as it decreases the problem of determining the loadi ng on the w in g was made difficult because you had to know w here the center of pressure was every minute. So, we shifted gears and l oo ked a t ce nter of pressure from anoth e r po int of view, in terms of Aerodynamic Cente r - which is a fixed po int on the wing. It is muc h simpl er to assume that the force s on a wing are app lied at the a.c. and that Gl=lOUND Sl<IMMrn

the moments (the torques) are twist ing aro und that same po in t. The so--ca ll ed Ce nter of Pressure is still there and, if it is e ither forward of the~ a.c. or aft of it, both the lift and drag force s wi ll pro, duce a mornent aro und it. Thus it is just as accurate to say that the force s on a w in g corn prise lift and drag forces actin g at the a.c. plus mome nts about that center as it is to say that the Iift and drag forces alone are acting at th e center of pressure and si nce they are, they also produ ce a twisting moment on t he wi ng. Six o f one, ha lf a dozen of the other. The w ing doesn't know tf1p difierence. As sta t ed ear li er, the speed-up (nose-down) forces co me from the fact that the e.g. of the airc raft is forward of this ce nter and the we ight of th e ai rcraft can be thou ght as rotating th e nose down, around it. Strictly spea ki ng, all rota tions actua lly rota te around the e.g., not lhe a.c., but to impro ve the understandi ng, let's say they operate around the a .c. Easier to visua l ize that way . If the e.g. is fo rward of t he a.c., you ask, won't the aircraft si mply go in to a dive and stay th ere? It sure will, unl ess it has the inhe re nt property of wanting to overcome thi s effect w h en th e speed ge ts pastthe trim speed . In mder to provide the aircraft w ith th is pro perty you need a force heh ind the a .c. to ba l ance o ut the weight which is ahead of it, and it must begin to overpower the weight effect as soo n as th e tr im speed is exceeded. O n a conven tio nal aircraft thi s is what the hor izo nt al tail does. The re is

a down -was h of air co ming off the win g trailing edge and this do wnwa sh pushed down on th e tail, and the faster you go the hard er it pushes, u nti l the no se co mes back up . As t he nose comes up and the speed decrea ses, t hi s down -force also decrea ses , and if th e airc ra ft is properly des igned the nose wi ll ge ntl y bo b u p and down aro un d the trim speed as the e.g. and th e down load on the tail fight it out to a draw. Wh en they stop fig hti ng, you have trim.

A t a ill ess aircraft has no tail, so wh e re does the nose-u p tend ency come fro m ? Wel l , a tai ll ess a i1·craf1 re all y doe s have a ta i I. If the w in g has no sweepback but is stra ight like on Al Bac k strom's ''P l ank'' and Jim Marske' s "Pioneer" and "Monar·ch" taill ess aircr aft, the tail is at the trailin g edge of the w in g itself, and th is co mes about by the fact th at nea r the trailing e d ge the airfo il is "reflexed" (bent upwards a litt le) and that pa rt of the w in g acts exac rl y like a long, nar row, very shor t-co up l ed horizontal ta il with buil t-in " up e levato r". Since the reflexed pa rt of th e wing is be'ii ind th e a.c. the fo rces back there tend to bri ng the nose up as the speed is increased. Wh e re i s the tail on a sw ept wi ng? At the w ing t ips, that's where. If the airfo il isn't refl exed like o n the strai ght w ing (and they often are) in ord er t o get "up elevator" the w ing at the t ip has to be twi sted, trai l ing ed ge u p. Si nce th e tip is we ll aft of the w in g's a.c. it does the sa me job as a ho ri zontal tail or refl exed airfoil; it provides a down load

Fledglill~J

Photo by Eva11 Hall

al some distance behind the aerodynamic center. In tailless aircraft with swept.back wings, th<) fact thal the wing is swept leads to !hose problems in the pitch and yaw directions I mentioned. As the angle of attack increases (as you slow down, for example, or hit an upward gust) the air over the wing starts flowing more and more toward the tips. For this and other, less well understood reasons, at sorne angle the air aft of the e.g. begins to separate from the su and stalling de-· velops. When this happens that part of the wing where the stalling is, drops its

UFM Ea1;y Risei

load and the nose, instead of pitch down like it's supposed to, pitches up. Wrong direction. Wrong, wrong, wrong. The tips themselves may not be stal· led because of wing twist, but areas inboard of the ,rnd outboard of the center are stalled, and you are left with a most unstable and probably uncontrollable aircraft. This phenomenon was demonstrated in fashion at Northrop Aircraft during the early days of WW II. Test pilot Max Constant was making flaps-down stall tests in a manned, powered, 1/4 (or so) scale model of the

giant XB-35 Flying Wing, which was in construction. As he came back on the control column, the control rather lhan building up as they would have in a tailed ai gradually decreased. Suddenly, the control col· umns came straight back into hi stornach, with such force that he was incapable of pushing it forward. Since lhe column also pinned him in the cockpit, he died in the ensuing crash. A loss to aviation. But as is so typic.d of such something fundamental was learned; the controls rpversc,d because of stalling near the tips. later we (I was working there at a pneumatic ram the time) alongside the control column of ;i modified version of the ill-fated aircrafl so that if the phenomenon repeated itself in subsequent flights the pilot could quickly open a valve and the ram would force the control column forward. Whether ii was ever US(!d, I don't know. But I do know that in every tailless aircraft with a swept wing there lurks the specter of instability al high lift coefficients (low Ever si nee that ace ident engineers have been very sensitive to the bi! ity of tip .. stal I ing and controls force reversal in swept wings. The design of the XB-35 itself was pretty far along when Max Contant's accident occurred and making major ,."""''"~ was not considered feasible. The problem was eventually solved by non-aerodynamic rneans by incor porating a fully hydraulically powered control system which, besides supplying the grmt power needed to operate the control also prevented any control feedback to the pilot. In fact, that's how fully powered ,1ircraf1 control systems, which are in common use today, were born. Even so, the pilots of the Big Wing took care to stay well above the stall speed at all limes, even though they could, if they acted quickly enough after the onset of stalling, likely bring the nose down via the powered control system. rlw i nstabi Iity of swept wings al low speeds can be remedied somewhat by the installalion of chordwise "fences" atstra pointsalongthewingspan, and by I he i nstal Iat ion of leading edge slots.

fJiioto by Ed

JUl_Y, 197E3

as wPII. Rolling and yawing motions and stabilities instabil are di uu1c111111,, 1, increased to increase this ratio. lnstabil is also cimH:.,1x,n11 increasing the sweep Both these effects are shown in ure 11 which I lifted from NACA TechI Note No. I 09 1 "Effect of

Wings al low written in 194h

nd Bernard Memorial Aeronautical doubl 1l1c1t after HJ ill available outside the technical forencc libraries. As in tailed or other the of the e.g. relative to plays a vital role in stabilknows that But few how crit-

ventional,

and in lice to say that I he i nsta bi I iti es develop a result of tlw same flow of

I see ta i II ess the design of 011e 1 with vertical tip stabilizers and rndders. These omissions are usually i red by the worthwhile lives of saving and dr,1g. How wing needs sorneth to stra one of tlw ,1dv,rntages put forth when lhe swept ""'"'''"" firs l came out was I hat when it yaws the upwind ex poses more frontal area to the oncornwind than the downwind and lhus the ,iircraft tends lo al itself with the wi like a weather varw. Sornetirnes it actually works that way, but more ofte>n than not the air·

craft simply to crab sidewisl' and stay there because there isn't difference in frontal area to do lfw job. of course 1 costs rnance. In addition 1 should the aircraft a stalling situation while skrdclmg sidewise some exciting manl'UVers, most involuntary on the of the pilot, are considered a bil Many of the tail swept craft of would back and forth, from ide to without ever settling down and flying straight. In this was one of the sewral that eventually killed the Northrop prog· rarn. The X[L35 was supposed to in its production version, a bomber. But it wouldn't it still long in yaw for the bombardic>r to line up his This pmblc'm was I.lier solved hy sl,wi11g the output of a very se11si live yaw rate gyro into servo motors which, through other motors, operates in differential fashion. by the time the problem got solved the military CllS· tonwr had decided to up on the

swep1. Mention was made earlier in this article that al or near the stall, swept ali,o have stabil yaw. Actual ly 1 there ,HP lateral ling, as in the t1ileron scnst>)

:.:;uncJunce

GROUND SKIMME:fl

F'lioto tiy Flcttina Gmy

f-iqrnCJ 1 Surnrnmy ol ll1e ef!E,c:I ol aspect ratio and sweep· hack on pitch stabilily at trm slall. f'osition of ci1Tlos delincs aspect ratio and swuep. (l'rorn NAC/\ TN 109'.J)

airplane and buy the ned B-l6 instead. Solulion always seem to come too late a phenomenon I daresay upon further reflection is also shared by accidents. But back to the hang glider yaw problem. Swept wings need fixed vertical surfaces to increase the damping in yaw and to return the ai to straight a when and if ai does yaw. By "damping" I mean those forces which lend to prevent the aircraft frmn yawing in the first place. Damping comes from aerodynamic sources and by the manner in which the mass of the wing is distributed along the span. Figure 2 shows how airfoil-shaped surfaces at wingtips can lift in an outward direction and cause the aircraft to rotate back to straight ahead. If rudders are incorporated in these surfaces the fixed portions of the total surface should normally the larger. of tailless aircraft The des have always had trouble figuring out where to install the surfaces and how big to m,1ke them. Some put them on the wingtips, as Figure 2 shows. Fauvel has pl them half Wily or so out on the wing on some of his aircraft ,1nd at the aft end of the pod on others. Marske has gone to the tips on some of his aircraft and to the center on others. Backstrom has done the same, although his later aircraft seem lo favor the tail end. Kiceniuk puts them al the tips, etc., etc. After 70 years or so of trying, nobody has yet found the "ideal"

place to install vertical surfaces which yousomeideahowfartlw ience of tailless aircraft has advanced over the ye,1rs. In all fairness, however, the most likely reason there appears to be no consistent sel of rules on how big to make the surfaces and where to locate them is thatthe ta i I less aircrilft is an engineering prima donna. Each ai has to studied on the basis of its own, individual dynamic needs and characteri and there are an incredible number of vari,1bles involved. Not an easy task This is also true of tailed aircraft, except that I is a weillth of datil avail,1ble on such aircraft and simple equations can be written to be the solution(s) In considering all these factors ii is undoubtedly sufficient to say that a tail aircraft musl have fixed, vertical surfaces installed somewhere, aft of the e.g. On extremely light aircr,1ft such as hang gliders my vote would be to put them at the tips. However, one must con-· sider that urfaces thus positioned act also as endpl,1tes to lhe wing, w·hich increases the riltio. As indicated earlier in this ilrticle the higher the ratio of wings the more vulnerable lhey become to pitch instability. Nothing in tailless aircmft is simple maybe the building of them. Little has said here about tailless aircraft without sweep. And there won't be, because there are very I ittle hard data available on such aircraft of the quality avililable on swept wings. Maybe in the future. One might logi-

F'igure 2. Weatr1ercock action of end moment around c.g (adapted from NACA

set to give outward lift ancJ stabilizinq

2E3

837)

cally conclude, however, that they don't uffer from the s,1me kind of pitch instabilities experienced by lhe swept wing simply because their wings aren't swept. Y,1w stability, however, would seem to represent a somewhilt more difficult problem because there is no sweep to at least lend sorne, if only token assistance to stability. only "problems" of s ifi .. cance in a t,1illess 1 unswept wing would seem to relate lo the extremely small permissible range of the center of gravity which is norm a I ly the prime re,1son for sweeping to increase it. That, and the fact that assigning part of the wing the task of stabilizing the aircraft in pitch reduces the efficiency of the wing as a whole. And in this context it shares the same problem with its swept-wing I

In conclusion, let me reaffirm rny confidence in the tailless hang glider. In spite of some of its shortcomings which are not likely to do us bodily harm if we use our heads I do indeed see a future for the tailless aircraft in hang gliding. I see a future for kites and gliders with tails, too. The only element which could slow the development of all these configurations is the rather disturbing attitude I see growing amon some of our newer · they are unwilling to analytical in solving their design problems, probably because of im· patience and because they haven'tthe technical background to do so. And they are similarly unwilling to take the lime and trouble to take ,1dvantage of the staggering amount of aerodynamic and structural intell that has been carefully developed ilnd collected si nee that fatefu I day at Kitty Hawk. instead, to go by intuition and "gut feel" looking for the sim solutions. The trouble much frustration, and downright danger, come frorn having too many sin1ple solutions and too few simple problems. The ,1II too prevailing idea seems to be, throw something together, outlandish clairns for LID and the pl,1ns and the kits on the market. we ain't goin' no-· where with this approach. There is lime. Take it. See you on the hill. JULY, 1976

For nearly four years now, Seagull Aircrnit has been innovatinn, designing, and building the finest bang gliders in tho world, Look at tho high performance gliders on the market today, mid you will see concepts by Seagu 11 years ago, Seagu 11 con, ceived, perfected, and produced the distinctive truncated conical shape, machine bent spars, cambered keels, cambered sails, applied tape1ud leading edge pockets, the first practical high aspect wing, coated cables, control bars, adjustable lrim, and the on, All ,Seagull gliders exhibit positive recovery withoul exteinal or "add,on" devices, There are no "instant" gliders from Seagull, Every glider produced for sale had been under development for over a fll 11 year, and the time spent is evident in the finished product, Each glider type continues to be refined during production, and lhese refinements may be incorporated into older gliders, You will never own an obsolete {Jlidcr from Seagull Aircraft, If you are serious about your flying, you should be flying Seagu IL

Seagull Aircraft offers superb gliders for all flying, from soaring, to full,on competition, Whatever your flying 1meds, your glider,

3021

Airpor1 Avenue, Sanlil Monica, Calitornia 90405 (213) :.394,1151

deal of progress in the last year in our li""'""''""""n" of how to certain fl char;ic, [eristics and pc1liilitics into gliders. We net)d also to corr1c lo c1 belier of !IH! best way lo achieve mc1ximum slruclural nd i n t n o n l \ ; To do we, need to know whc1t constitutes structural The th that tlw kite stays in such ,1 way that it reL1ins the that were into it. rd<!rs lo the concept of wlmleness or ,,n,nrilr,,t,,11"~'' 11c for d 1T1mnent 1 c111 oak tree a ncl wi I low tree sic!<) side in a trenwndous hurric1nc. The 0,1k tr,)e is much stiffer and also but tlH' willow tree! is able to lwnd much fmthc1, without A~. tlw wind increases, the willow Ire(' bends lo relieve the forces where the oak trPe st,rnds solid. Tlie wind forces can so great 1ha1 I snap the oak !we while the willow slill lwnl the wind. the wind subs !he willow bends lo nnciJ,,,,,, while the oak tree lies

the willow lr<:<' has maintained whilE' the 0,1k trC'c has nol. In Lake's lent article on Ai and nJC· lural ilun· 1 (Crouncf Sl<irnnwr, 1976) he describPs the manner in which "infl ructlHal failure rPsults from f>\/!'OCCl\,,n lifting fore(' ied nst tlw mass of glider and pilot or inst ,1 low lirw." fl<' then on to caku, latcthatfor gliderflyingatanai of andwith norm,d stall of 16 it is thE)oretically for suddc1 n to induce against glider and The quPstion how do we a glider to withstand this kind of force? rhe idec1I solution, it seems, would he to build glider 1rnpoi,srl>le to induce th is kind of cle:s111n1r1t, into the glider an automatic sys1cm for ex,c:e.,;s11,1 e I force. It was with this ap· in mind that Wills Inc. to use the and more flexible 1 Y2 .049 6061 T6 drawn seamless in tlw main framP spars of even our its stnJClural i

In our resc<1rch and in the us<: of gliders mounted to we found that a stronger and less flexible .049 tubing would break 011 hard irn, However, when a kite was used with morP flexible 1 '01'' .05B tubing, even the most severe' i111pact did not re~;ult in any structural failures. We w<.'re, in even able to increase the sizP of thP kite from 1 to I feet without any of the structural weaknr2sst~s we encountucd in tlw stronger, less flr)xibl,· tubing. On April 25th at Dunes, we lo determine 1he strucl ura I Ii rn its under load of one of our production gl tl1c! 1OOA. was 10 increase the load of the kite until we we:re able to produce! a struct1Hal failure. WP then lo use this data lo det,·rmine the recommended slruclural limits 1o on tl1t' plc1c;1rd to lhe yet unofficial HM/\ guideli1ws. In winds up lo mph on a ~;and we firs! launched four and then fivt' peonst the glidC>r so11wwhat in Note 1he increased deflection of the load is incre,1sc>d We !lien launched briefly into the air, and discovered that under a load of C's the deflection of the leading was so great that it a Ilowed the rear port ion of I he sa ii lo deflect rPteasm12thc load nst it and dfoct s!al

'"'""'r,nr1 in these tc'sts, we rnust use the John Lake in his article. Our maximum in these tests was 4S so we havP one parameter of the fon,wla. We must now use 11w infor, ma!ion we have to de1ermine the 01hcr parameters. Our told us th,11 at mph maximum the maximum amount of we could aloft in the kite was between fiw and persons (895 and I CViO lbs. The kite would fly with fivl~ but would not fly with the full weight of six. Using this information, we can estimatP ilw n1axi111u111 load the kite will lift with an ai of 45 mph It is about 9'i0 lbs. , we know it will lift more and th is load this is lent to a wing A,·r·nrd,ino to the formula:

fJholo Photo nc,,,c:nrmnr" reloa:;ed, the 1uhinq ret11mmJ to norrnal witl,0111

GF10UND SKIMM[ll

maxirnurn lift

Deflection of 1 Tube to Yield One End Fixed Tuli1• She, Wall

Maximum Oe{Jection

forn• Applied

to Yield

I V2 I Vi I V2 1 5/ii

.(l3 .049 .05cl . 05 B

3 7" 34"

1% .ms Hi .049 .Ol5

31" 7"

.049

.O"iB

711

16 lbs. 22 lbs. 25 lbs. 50 Ibs.

l l"

lbs. 30 lbs. 29 lbs.

40 lbs.

46 lbs. It is interesting to note here that the amount of deflec· tion is independent of the wall thickness and is only determined by the tube diameter. The amount of force to deflect thB tubB is dependent on both.

(/)

0 IL

0 dl 0

Maximum /\irspc)ed (mph) (X)

This compares with tl1e G forces tlrnt can be achieved with a flexible airframe versus a rigid airframe. The rigid airframe curve comes from the equation: (X)

(

stall speed )

(Y)

The SST flexible airframe equation was derived to approximate actual data and is represBnted by: (.94) (Log10 [XI" IYJ. Since we know lhe flying spE!ed and the maximum lif1, we can now compute the stall of 1he ki le in this C situation: [

]

4.22

Solving for X we get the stall X I .B9 mph. When testing the stall speed of 1he glider wi1h the norrnal wing load we> found it to be 12 mph. Therefore the frame of the glider has distorted under a load of 4. G's to decrease the lift and to causl! the stall to increase from 12 mph to 21.89 mph! Whal does this mean to a pilot? If you are flying along at

4''i mph and you hit the maximum gust your kite lo suddQrtly lw at just c1bove stall speed, with a rigid airfrarne kite that stalled at I mph, you would be subject to I 4.06!C'S. With an airframe that flexed to increasP the stall to 16 mph, you would be subject lo 7. 9 C's. But with an airframe that flexed 10 in crease tlw sta 11 to mph, as in this case, you would only be able lo reach 4.22 Gs. Since the kite has been tested to 5.6 C's in our actual flying tests withoul breaking, lhe kite would nol break in this situation. How does this work when designing a kite? By consulting the chart, it is easy lo see that 2 11 .035 tubing is slronger than 1 Vi .049 tubing since ii takes 29 lbs. of force to bend it to yield while the I V2 .049 takes only 22 lbs. But the yield deflection is only as compared lo 37" for lhe 11/2 .049. t,er·et<ire, when the kit<' is hitting a severe gust, the frame is 11 nol as flexible with the 2 .035 as ii is with thc, 1 V2 .049 and cannot deform its shape as much lo increase the stc1II by reducing I ift. 11 is easily possible that at 2 7 11 deflect ion of the lc~ading the forces rnay well exceed 29 lbs while ;it deflec1ions of 37 11 the forces are well less than 2 lbs. fhus wilh the tubing, even though the yield forces are greater, the stall speed is much lowl~r so the C forces are 1r1uch, much greater. The forces could greatly exceed the yield strength causing a structural failure. An historical example is the case of lhe Viking ships that were able to survive he,wy seas and storms while other bo<1ts fell apart. The Viking boats were able to do this because they were able to bend and flex to conform to the waves. Another more extreme exarnple would be to in1a glider with wings that arc so flexible that they arc able to bend all the way up and touch before they break. In this case it would be irnpossiblc to break the glider since increased loads would induce increased bend with subsequent loss of lifl. At some maximal loact the wings would bend all the way up until they touch and would be exerting no lift. When the force was removed, they would resume their normal position maintaining the structural integrity of the craft. It is interesting to notP th;it the glider's strength in this case derives from its flexibilty, and that a rigid glider would actually be weaker. A glider built of heavier and less flexible tubing that was unable to deform far enough to relieve itself of excessive lifting force would have to break at some point, and would also deliver greater forces to the pilot in he;:ivy turbulence in exactly the sarnc way stiffer springs on a car make for a harsher ride. The important thing to remember is that no amount of structural strength can guarantee the safpty of the pilot. his own judgment can do that. Even if it were possible to design c1n indestructible glider, we arc all doomed to live in very fragile bodies and the violence of nature can be appalling. A pilot whose neck was broken in violent turbulence which smashed his kite down upon his head would not ca re Iha I his kite was in condition after he died. Even in a glider the pilot is the last factor in determining whether the flight will be successful or final. As we fly higher and larther, we owe ourselves an increased respect for the forces of nature as embodied in the wind. JULY, 1976

Due to the advanced we are unable lo covm the mee:'i in this issue. See the August CS for

and

coverage.

Our good brolhers to the South in Australia and New Zealand have never understood why we haven'! used battens in kites. They have doing so for several years. But all of a sudden it the in thing to do, and alrnost every manufacturer is putting forward his version of the new miracle Battens. So, what do they do, what don't they do, what's good and bad about them? They have at least three basic functions, and the examples of battened kites take advantage of all three. Briefly, this is what they do: 1. tighten the trailing of the sa i I at higher They support roach. 3. They allow more control over sail shape. In more detail: when a kite's increases the trailing edge of the sail tries to move forward As it moves, it allows the sail material to become slack, and the sail starts to flap. It sort of folds up on itself. A batten which runs from the leading edge to the trailingedgewill notallowthe sail to move forward and the sail is thus kept "clean" and full at a higher speed. Just to prevent a lot of letter writing, I admit that the above explanation is very simplistic and bes only the outward effect of speed and not what really happens. Actually the sail u goes a series of corn pl icated changes with various areas deflating and sl material and camber moving around. But the end problem and result is just about the same. That's why a Quicksilver or a 747 doesn't flap in a dive. A batten does not have to be very stiff or tapered to serve in this applica-

tion. The Nimbus is an example of a kite that uses battens for this application only constdnt dimension, flexible · sail tensioners if you will . Battens can used to support roach (which is the sail that is outside the straight I ine between the end of the keel and the end of the ledding edge). batten used to support roach needs to be stiffer but not as stiff as you might think, use as long as the batten is not broken and is tight in its pocket, the sai I material must stretch for the roach to sag. The Kestrel is an excellent of a kite that uses battens to support roach. 3. Battens are used to control or aid sail shape, and here is where the plot thickens. Everybody knows an airfoil is better than a flat plate but nobody knows which airfoil Airplane wind tunnel research is of little value because they have rigid airfoils, and they operate at vastly different speeds and wing loadings than kites. Our best help probably comes from sailboats, which do operate in the same wind ranges and much closer wing loadings to our kites. Fortunately there has been sorne research in wind tunnels lately on battened sails for catamarans, and their conclusions us some starting points as to whPre lo locate the maxim urn depth of the airfoil and how deep it should Sail shape obtained in four primary ways. 1. Sail billow a "How much billow you got?" 2. Internal Camber. (or Broadseaming) The individual panels of cloth are cut in long curves

and when sewn together, form a sculp'.. lured shape. A sail I ike th is wi II not lay fl at on the floor. L External Camber. The sail along the leading edge is cut in a curve, and when put on a straight tu be, produces fullness in the sail 4. Induced Camber. A straight cut sail is put 011 a straight tube, which is then pulled out of a straight line by or deflexers, or some other ng, o nee again putting fullness in sail. Most kites use only the first of these. Some kites like the Phoenix and the Dragonfly, use thP first and last. A few of them like the II IV, and the Albatross ASC 21, use the first three, and a very few, mostly experimental k use all four camber methods. The tendency in modern kite ign now seems to be moving away from the use of billow to produce camber, and toward the other methods. Most of the top manufacturers are now experimenting with, and test flying kites with from zero to one degree of billow, and are having excellent results. Why go into all of this? Because each type of sail shaping puts different requirements on battens and the batten for one sail design will probably not be right for another sail. Mo 1 of the differences and similarities between battens can be described using two measurements. I. Flexibility (or stiffness) 2. r:lex Pattern or Taper Ratio There is unfortunately 110 widespread general method for measuring batten flex and taper; every sail maker and batten maker has a different way of bing their battens. ,JULY, 1976

lhc

in to acco u nl batten lo know in advance and flex pattern

niere is no what the will be. has lo make sort of half-educatc~d guess, ,rnd start the kite. c;rn,ful ohserva .. ion, or even studyin pholc,1{r,1pl1s, the will be blc to decide how to either to stiffen 01 or decrease the taper. Battens h;ivp been rnade of

fi al urn nurn, ing, eic. Al

arid lhin.

I derivt'S its s,iil sha1w fro111 inter nal a11d PXt<·mc1I c,mibPr, \dpPrHI flexible b<1t1e11s. M<1xirnu111 i<; lo· c;ited dppmxirn,ltPly 40% of thl' cord lr;11gth.

and locate i1 where ""'-r,,nf of the cord battens were used in the I, the kite would have its maxi111um camber much further hack than Mr. Price wantPd and the sail would not dPv<··llon quite! the lif1 it now does. Th,! bcilterb in the 7 would move the camber clear up nst the leading

rs! three. fairly comes in lots of sizes because is lots of sailboat sail mak Prs, and it is also the heaviest. r dSS····foarn sandwich battens arc lighter, but more It is strong, but !he inalc· if mistreated. Wood batlens

The CW 7 derivi•s its fullrH«;s from luff rnrve (exl!;rrldl supported liy batten•; uniform flexibi

one. down to some fairly irnilar an lorn Prin! of Al .. and ,l CW by the author. 1 gets its sh;:ipe from both internal and external camber, the fullness is sewn into the sail where it in this about 40 percent of the cord The battens used on th kite well nd more flexible toward the front than the rear Ii The on the other fullness from luff curve nal which max .. much further forward. Its (2x4 I in flex I the CFlOUNIJ SKIMMEf1

'.l?

the most exotic racing sailboats' sails use wood battens with excellent results. Wood has the advantage of being cheap and worked. By spending the at a training site with a handful of wood a Polaroid camera, and some sandpaper, you can have some fun and really tune in your sail shape. We have been talking about what battens do, and it would be only fair to

fi1w tuned with the tension adjustments. A good to start is at a bout the minimum tension ne<::essa1·v up the little crosswise wrinkles around the batten pocl<(::ts. a batten takes a lot of tension to get a good shape in tlw it is probably too stiff and should be shaved. On the other hand, battens that flex excessively under no tension need to be stif-

so they say all their cloth is their best If you want colors in a sail you haw to some con1promises, and one of them is in the directional stability of the cloth As an a pocket for a batten six feet long can change as much as one-fourth of an inch in just month's flying, and % will noticibly change the tension that batten is under. The use of son1e sort of shock cord or as d tensioner is proli11

Roach supported by battens dlectively locate washout al the tips.

note some of the things they don't do. Mostly, it is important to under·stand that battens by themselves won't work miracles. Battens c1dded to a poor or worn out sail will only a poor, worn out sail with battens, not a mod·· em high performance glider. Battens used effectively allow the sail designer to distribute area as he wishes, moving it more toward the tips or placing it evenly along the span as he ut:.'.,,11e~. Proper use of baHens allow the designer lo shape his sail for slow speed performance and be confident that the resulting kite will also fly fast and clean. While the flex and taper of a batten are most important, the tension that a batten is under also plays a significant role in determining its overall perfor mance. Tightening and loosening the battPn increases and decreases the in iii a I camber "set." This "set" added to the camber caused by the pressure of flying, determines the fi na I, flying configuration. So the sail shape can be

fer. If you look at the top of the sa ii (in flight) and !he battens forrn littl ridges, they are either loo tight, too flexible or both. Little valleys at the battens ly indicate are too stiff. The best way to tension battens is with string, each batten can be individually adjusted, and the adjustments changed to suit a changing sail. The problem individually tied battens really add to the time necessary to se1 and break down the kite. Some use pins to tension the battens; fast, but not in all Generally, a batten that is place by a pin through a hole will prove less than in the long run. Sails with weather, Even the best cloth changes, r in mind that the sail cloth makers do not make their best cloth in any color but white (at least that's what sailmakers will tell you. The sail cloth people will disag· ree but they also Ii ke to sel I their cloth,

ably the bes1 compromise reasonable tirne and proper batten performance. It is a little harder to initially the tensions, but once done they self adjusting, and besides, you won'! arrive at the flying site and discover that you1· batten pins are in a pair of pants at home. Battens can be a pain. They arc" awkward to stash, and you always have to worry about some spectato1· stepping on one in the set-up area. I looked up once, just in time to see some little toddler cruising off across the parking lot playing with a "really neat stick" he had just found, one of my 1ip battens. But, when you feel th,11 extra lift, enjoy the improved stall habits that let you turn a blown landing approach into a Bob, Wills like bulls eye, marvel at the smooth quiet when you pull in the or just the plain old beauty of a ly nice battened kite, it's worth it all. Anyway, birds have battens, sort of. JULY, 1976

necessary 10 maintain the light force should he necessary pulling the bar toward the pilot. In other you will need to vt,ry sligh1ly force thc nose down in ordc:r to main· tain I rYr! of stalls . lncide11tally 1his w i 11 he very close to your best L . If no bar pressure i required lo main1ai11 this I the reflex m;iy not be ualc. If excessive bar pressure is requir·ed 1 there probably is rnore r('flex than necessary, and yom r rnancc will be reduced. If the reflex needs correclion 1 make the approp· ria1C' and re .. find the proper e.g. as it proli,1bly will c when rellPxisch;i at1·1 r11iofstall and reevaluale your gliders 1 ability lo fly hand oW' wilhout change in air When satisfied with the .g .. fly 11 al 1 % of stall r1nd check 1

Tom rif'ntcd hang gl id(:r manlHPrs us<' reflex tuning proe<'clure lh;1t al lows their to hibit both pp1·forma and without izing the test pilot dur· re. Neither this publ icatio11 encour·· conslruction or lc'sting of hang gl i<h, pilot owrH!ts Howewr 1 we re very conu•rned ,iboul having arkqu,1tP information available for those for one n,ason or nother wil I and or conslruct their own machint's. rr: outlined in this col The unm is descriptive of tfw l<>chniques usPd the Scott Air Craft II is in no way u r,intecd lo be di asler howev<'r w,' h,wc• found ii to l.w very uccPssful des tool ReflPx and cen i11tern•l,1ted, but in actual ar<' par,it<, that sirnil,ir fl am uate reflex will causc the glider to pitch down at h 1· rc;iling tlw illusion that llw CPnter of gravily far forward. Actually if the .g. wt>rP loo far for .. ward th<> glider would pitch down at all Disastrous conseqm'ncPs rPsult from i ua!(' fm once lhe 110s<> down inade· quatc it rn,1y be virtually im· possibll' to bring it back up to l<~v<'I fl . In other your flight i,.; almost certain to tcrminatt) in a dive. The fi I of the testing in volves finding the cenler of gravity 1 bPc,iuse wi!hout the proper c the effects of improper refl will be masked the ive bar prcssmP necessary to n1dintain levt>I (I The first i the running test. Using level m very slight down .. hill run with IIH) gl allowing it to float up and pressure 011 the swing scat 1

C:lROL.JI\JD SKIMMEll

or harness your exerts a force on the glid(~r c1 downward pitching of the nose indicates that the center of gra is too fadorward and i1 must be moved back. On the other hand 1 if the g I i d r h c c o nw s t a i I h c a v y I t h e C<'n1e · is too for to the rear ,rnd it rnust be' moved forward. Adjust the e.g. c1nd IIH' rnrrning tests until the glider level with slight we i11 the seat or harness. The second step involves a downhill runn test where. your entire body b(, pu1 on the glidc>r. II is im nt lo star! close lo th(! hollorn of I hc, hi 11. If thP gl ide1· pitches forward you rnay rc.ich level ground and prC·· vent the nose from digging in too sevPrely. Whl'n you are s;itisfied that the is neutral rnove on 10 stt>p three Choose a slightly higher launching point for three 1 where you c;rn actually bly 110 more than five or ten feet off the grou11d 1 to the proper .g. position. When you are salisfied with the ing e.g. test 1 install an air sp<•ed indic;1tor 1 and dc,t<:'r111i1w the! pproxirnate tall 1

For the next flyat11 %ofstall . For example, if your glider slallsall rnph 1 rmthisslepall 1t mph This is the refined setling for the center· of . This will be your ap proximate s for minimum ink rate and your glider should fly "hands off' without peed change. In other words it should fly level at this and the center of gravity should now he correct. Now we shall in to learn about the actual rdlex capability. From an intermediate hill fly at I % of stall (fcH example 1 st,111 speed i 1 mph. I x l % i 1 mph.). At this flying note the bar pressure I 1

you are satisfied that the center of gravity is correct and th,11 the proper bar pressure is necessary at I % of stal I When completely satisfiPCJ with the fly at I % of stall Lighl bar prnssure should be rered to maintain . We l1iollly rncornrnend that you not e d 135% of stall , until you are fully satisfied tl1,1t both the centcr-ofgravity and reflex are properly ad· justed. When fully sati fied with th vily and llyi11cr,:ascyourair ,noting tha1 thP faster you fly the rnore bar pressure (pulling in) i required to 1he glider at that . Wfwn you release the bar 1 the glider should slow to 11 <10 of stall and then fly level. This ure is being successfully used by Scott Air Craft Co. and is offered to you i 11 a 11 attern pl to provide for your If you have ideas for im ng the of hang gl iding 1 ple;ise scnd them to me for inclusion in future arti so that all pilots may benefit from the knowl each of us rnay h,we. Send your ideas 10 Tom Caul c;1c)Scott Air Craft Co I JOOO BellPvue Red mond Road 1 Bellevue, Washington

9BOO'i. '.39

ll1/'>1n1>"\A/J/'1/J

"1'"""" '" colors lo the west where !he sun sel a half hour The wind had lessoned late nfternoon when ,ill the other ki had leaving had lo be folded and him alone in comm,rnd of the elt'rnents. Then· Wt'l"t, gusts now to it fun. was well, in the· winds earl it h;id taken constant alertness to thrust and parry the suddt·n wind-shifts. Now lw wc1s tirc>fL Ann had the Ii o cnnper ,rncl the ,Homa of was to flavm th('. gusts. When she appe,ired at the door, slie didn't fi11d it too hard to him lo call , He let llw hand and foot bars the and tail assumed the neutral position. Un tlw tack he lowered himsc,lf to tlw c1nd the no craft. What WilS he rid It had to he a fl ircraft but aiter centuries of no successful orn has been built yet, That's where you in What rnakes us think now is IIH? tirne? Well, in the first like the family thc1t was certain that the 1Pnth child was the "We now know

it!" And in the sc,cond

sport where earlier ·olh·wnn!c but didn't achieve iL

in a wind. lide from ,l Tow.launch or rake off from level. GF<OUND SKIMMER

·1 /

nthal u pend,,cJ ;1 craft from the h'.1\.1m.n\AI

bul could support We now know that wind essential for lilt The S<'crels ofanirnalfl ar(:wellk11nw11 1 & 2) ly ;i few of tlw less complicatl'd nwclianisms of animal flight are nPeded for a ng ornithop· rn"r,rw,r1,1

dc•signed and built

;1 new sport can he IJOm,

of challenging the winds that call a halt to conventional When gusts really strong, ev()n the gull<, in Jon.alhan flock abandon the SC'arch for food in favor of the sport of riding the stuff Like silil white-water car10eing 1 or ski it's man against nature 1 but no need to be cold or wet! Our purpose lwre is to a few of tlw most pointers that havP been learned about ornithopters 1he "h;ird way"). In designing your omithopter, our chief advice would be lo in mind the most i rn po rt a n I ,w,nr,.,I,, of SUCC(:Ssfu/ de" It Simple\ Stupid). KISS ~hape or plan-form, many models are in na lure or in literature. No, none of the n:,t·Pntt,rl versions have been successful; each has had at least one vital cirror of concept or construction, Some of thern were never even tried, bu1 by now we have IQdrned whilt not to do. An ornilhopter is essentially a device for exerting force on thin air, Successful ornithopters have been built. 3) de· scribes some of the best built by Pro· fessor Erich von Holst but concludes that lo scale them up to man is not the way to go, Nor is it wise lo follow too the methods of to fly through

Tlw birds, tlw and lhc inS('Cls do not need to lriarn to fly any more than does the maple · when the is fabricated by nature in the proper manner ,rnd the power is applied at the point, then the rnain flying actions arc automatic. If the is ii will fly rhe pl;in form of some of the or nithopters taken from and other I iter.itu re a re shown in 1 ; sonw from nature ,He shown in Note that most have one feature in cornmow the spar transmit forces lo (or arP near the leading point of .ittachrnenl of powPr is marked P. This results in a downward twisl of the du the powered of the, fl<1pping and directs thrust cornporwnt of power forward (111 tlw case of the maple the power is ied the force of and the structure of the causes it automatically to line up witli the stiff leading into the relative Nature and man's experience tc,ach that flexibility of the trail of the wing is conducive to successful propulsion. Much thinner wing lions are found in nature than in dircraft. This is probably highly desireable and possibl<, when the attached to the for NASA have shown that only flexibly attached to the heavy parts of the air" craft have the effect of reducthe effects of gusts. !he power required for wing aircraft is a different hall gilrne than for fixed except for Cravity power ing down hill) is sirnil,ir for the only for control in the ornithopter. But for 41

Fi(J 1

steady flight, high RPM !H'S, if used at all, would best be used only to rump a cornpressor, which in turn would supply power to a linear actuator. Some have advocated the smooth power of steam for ornithop·ters. The Stelzer patent, Fig. 1, proposed a novel piston pow<,r caused to fire each timC' tlw wing was in the right position. And no! before! Too many ornithopters have shakC'n themselves to kindling (on the ground) when the cycle was timed at the convenience of the engine, not the natural period of thP wings. Human power has the advantc1ge of easy attachment and availability. As long as the man is going along for the ride, he might as well get some exercise and makP himself useful Studies of the relative cost of gasoline vs. hamburgers are inconclusive. If muscle power is to be used use all of it! Unlike the bird, a man's most powerful muscles arc not in his breasts, but in the thighs, the the back, the arms. This suggests that a rowing type motion would be ideal. In Fig. 3, we show one possible mode of application of muscle power. Remen1bcr th,11 we're only talking of Stage 1, with the craft suspended in 4. the wind; we don't yet plan for The arrns pull while the legs thrust; also there may lw occasions when the return of the wing to the top should be faster than natural wind pressures

Fig

-Various plan-1orms of omithopters.

-Wing shapes 1rom nature

would do it. using means with pushes as well as pulls can be transmitted to the That's not the way birds do it. Lifting of their wings is by a I, but a pull on top of the main hone, the humerus, by means of a muscle that comes from the breast up and over the wing bone. The must be individudlly controlled to counter gusts that may come from either sidi!, as well as to facilitate turning. H,rnd and foot power, d at· tached as in 3, could be applied equally to both wings or prirnarily to one or the other by rnoving hands and feet off center of the bar. Properly fashioned wings may be able lo extract energy frorn gusts. It has been estimated that as much as 70 1!1<, of the energy of the wind is in the gusts and only 30% in the straight-ahead direction. would--be fliers used to argue about "aspiration," by which r:ig. 3

-Man powered con\rol of flappino win\:)s.

they meant a wing that could even sail into the, wind, not be blown back from it. (No, that wouldn't be perpetual 1110tion or get! something fm noth and therefore impossible. It would only be Pxtracting energy from unruly gusts.) No one has pub I ished complete instructions on how lo accomplish this feat, and the birds ain't telling. In 1921, a Prof. Katnnayr of Vienna published results showing that gusty winds produced surprising reductions of dr<lg. Others confirmed his results 11 and partially "explc1ined them, but no orw has made practical use of them Whether or not we can get a free ride "into the wild blue yonder," using "aspiration" or the l<atzrnayr effect, there is fun and technical challenge to bt> had in constructing the first workable ornithopter. The best reason to explore flapping flight is simply that it hasn't been done ypt. The man who responds to thc11 kind of challenge will have the best chance of success. Flap

Happy!

Bibliography

·1. Colin J. Pennycuick·

Animc1I Flight," Institute of Biology No. 33, 66pp 2 Encyclopedia Brittan night (Natural) 11 3. Karl Anatorr1ie und Flugbiologie der Vogel" (Anatomy and rlight Biology of the Bird" ,JULY, 1976

·1 he iirst a1111u<1I lnstruclcir•,' CC'rtilic.1tio11 Clinic i•; 110w lli•;tory. All lho,c who <1ttP11ded ,1gree ih,11 it was c111 outst.inding ,11n although .i bit soggy in thl' wP,1tlier dcp,Hlrnl'lll. lhis w;i,, the first Certification li11ic to lw held in the U11itcd Stales. rhe monu mental t,1•;k of organi1ation was umJertakC'n hy IP(' Stt•reos, lxarnincr for I le w<is assisted IJy J.111 Steve McCork Whitehill ,rnd I )pan /\ldingc·r. J,rn deserves I th,rnks tor th(' m,111y rnar1y hrnir•·, she put in Mldngi11g to get tfw i<1cilitit",, •,clH'd11li11g tlw dC· tiviliPs 11d gl'rwrally orchestr,1ting ih{' in· unwrc1lll<' del.1il fitty i1v;fruclors attended the linit which W,1', l1eld over the first WC'('kPnrl in I .it I orl Crnnkite in lhP Colden C.itP I\J.11io11,1I f~ecrP<1tio11 /\red. Dorrnilmit",, dining h,dl, ,rnd 111t)Pling rooms in'P of ch,11w' thC' I\J,1. WPn' lion.ii l'ark St'rvit e. rlw Ranger,, .1nd nte11de11t jerry Schober Pnthu,,i,i~,lic,illy to J;m's request i11 l,Hl, ,1ll th,1t w,1s initially .isked for w.1s ;i mPt'l· ing -,p,H<' for di ussions. The N.ition,il [',irk Snvicc ilw L1ei I itic's hc•c,wsc' of tlH· 11,iture ol the progr,1111 and its .ip· to the park. !hey lt'l'I th,11 h,111g gliding h,1, .i low t;nviro1rnwntal im· p.icl, ,md l>cc,iu,,e t .ire intcn',t!'d in h\'lpi11g us to pro111ott' in ;1 sclfdtcd ',port lhl'y t'11,1blcd the org,rni; lo tl1t' cost of the clinic down to $ I 00 (tlw rn,I of the food). l he kitclw11 was staffed hv DC'1111i T.itP, rol Droge ,rnd Midge Aldinger with ists from Mewhin11y ,rnd Je,inic 11;111. Thi, group, who don.ited their time ,incl made tlw meal, ;i rc,il h of the clinic at Fort Cronk· itP 011 8·00, .1lthough quile a trouhlefind the

would come a car with ,1 kit<' on tlw top, hc,1ded in tlw oppo·

cmoUND Sl<IMMFJ::i

site direction! In ,iny cast', the persistent instructors did !ind lht· IY1C'Ct location, ,ilthough ,1 lot or people werP wondering wlwtlwr or not it w.is .ill ,1 hig April fool's ,rnd rP,illy no! IIH'rc ,ii .ill. night was spent cl ih(' goal,, of lhP co11rsc ,1nd thP lcrns Pn( 01mlC'rt'd hy Cliding In· stn1cl(Hs over c:otfrc, ancl ,ipplt:s. Joe Adler gave -111 i11sl rnction I idP prcscntal ion which is intPnded ,is ;i complement for his hook "11.rng !light," followed by a short Li I k Ii y I) c ,1 n I' as ch a I the "f I y i 11 g r,1 st.itioned at Yost>rnile. Dean exp· lai1H:d that rc",ervations <1re required to fly ,it Yo•,cmit<', a11d that flying is restricted lo lwc·lve fl per ,ill to take, place lwforc 10 /\.M. !\ 11,rng IV r,1ting is also n'quin'd Bill welcomed ilw group on heh,ilf of tlw Colden C,1tc Nation,11 Rene.iii on /\n'd, and WC' lirold: up early lo 11ight'•; i11 prc'paralion for

and early at 7:00 n with a iant,1stic lm,,ild,isl of sausage, eggs, 1>,111c,il«!s, cold n·n·.il, fruit, coffee ,rnd ounge Jtriu'. rl1e i11structors divided into groups of IO and Wl'l1t out to the hill lo dt·rnonslr,lte their lc,iching techniqut·s <1nd oh•,t'rVP t'ach otlwr in ,iction. Unfor. lu11dtclv, ii n to mist almost i111nwdi<1lely, <1r1d t1111wrl inlo ;1 cold rain within hout ,rn hour and a h.ilf. Mos! of lhc groups ,,tuck it 0111 011 the hill until <'veryont' had h,1d a chance to play the role of instructor, then beat h,1sty retreat hack to amp for.i hot shower and the written part of the exdm. The t'Xdm was extremely and you could literally f1c;u .i pin drop whilP tlw test was ii<'ing ,1d111inisk1nJ ·1 hclestswerecollecled and redistrilJuted aftt'r lunch for and discussion. You can bet that llwre wer(! so rnc sti rn u I ati ng cl iffen'11cc;s of opinion on •;ornc of the questions, and it was a re,11 I ming c•xperie11cl' for everyone in· volvecl. the tirnC' ,ill the answers had !wen cussc'd c111d dis< it was 4:lO,

time for a group rnl'Pling followed by din· ner, d t,ilk hy l:lill 011 i11struclior1, and ;i short hreak. SaturcL1y 11ighl, of crnirsc, was p.irty time. W,ilt Nielson brought s<~vcr<1I c-1st'S of liC'er ;ind sold them d1 cos!, movi<'s wen! show11,and cvl'ryone gc,11c'r,illy rclax<'d after ;1 h.ird day. Su 11 di il·OO, and alter another f,rntastic breaki,1st the instructors split inlo two group,. One w1•1111Jc1ck on the hill lor further practice .iml i1v;truclion i11 lc,1ch .. ing technique's, the other in the 1T1e<?ti11g roorn to discuss tht~ I lerns or ,idv,rnu,d inst111c1io11 ,rnd the' i sua11n· of r,1ti11gs. The groups got logelher again ,1ftp1· lunch whl'n llill laylrn ,1 second L1lk on tl1c psycho of instruction. 1),111 talked ;1bout the prol>lcrns involved in ,rn nd told the how to h,rndl(· IIH' prc•ss i111lw c;1<;(' of a serious cr,1sh. ),ick I !,ill g,1VP a short pn?,,enl,ition of I Lmg Ciliding lir,I /\id ,rnd tlw Instructor's I irs1 /\id l<it. )<111 C1 talked bout the currt•nt insurance sil11;1. tio11. 11 seems that Trident h,1s fo1111d d rier will lo write ;i pol It c,111 lit' written lor $1,000,000 pf'r occurrenct' and will cover the the site or tlw pilot lialJility. 1lowevcr, Trident rnust hav(! 2,000 g11ar<1nlc<'d pol icy holder,, lie forP !hey can write tlw policy. Those inlPrcstcd in insur,rncc are to wrilc to Jan c/o Ch,111dellP S,in fr,mcisco, I 0 Hillside Blvd., Calilomia. Vidt:o t.irws had Ileen l,1ken of most of tlw activities over the weclwnd by I of Los the ins1 rue· tors h.id ,1 ch,11Kc' to sec the tap(!S ,1fter Jan' talk. Thi served as the wind-down period, .ind soon all the p,irticipdnl'i de· parted, fpel th.it they had e11 very Pnlightn1i11g and educational ('f1C('.

!\ sPcond Region Instructor' Ccrlific1lion Clinic will lw held in early Watch Cmun1/ Skimmer for further dt'· lails.

Ill

In this concluding segment of "Pitch St;1bility and Control" we will consider lhe flexible wing Rogallo and how it is dfec:lcd [Jy "high" angles of attack, i.e. st,11 and "low" angles of altack, i.e. dives. (Recall that the wi of attack is the ;rnglv ,it which the meets the air.) The behavior of a Rogallo ind dive and the question of recoverability has been frequently discussed within the pages of this magazine. A person would have to be quile naive to say that the St,rndard Rogdllo, in cerlain configur,1tions, does not have div(! recovery problems we need only page lhrough past CS accident reviews to see how many injuries and chiths c1re dive related. A person would h;we to he even more naive \o s,1y th at c111 Standard Rog a 1los have a dive recovery problen1. Why tl1en, do some Rogc1llos have this problem and others do 1101, and (urthcrmore, what is the problem/ Much of tlw time the difficult part of solving a problt!m is defining lly whc1t tlw problem is. In this cc1se we can s\c1le withoul question, that sorne Rogc1llos have not recovered frorn dives. But this is pretty general statement, ,1 dive is anything frorn flying (ast to a totally collr1pscd sail in a vertical dive. We need to be n1ore specific. This kind of dive is often referred to as a full luff" dive, with a strong implicalion thr1t the (.ict the sail is u11inflc1ted c1nd luffing is the reason for non-rC'covery. As <1 step toward understanding the problem le1's review the factors affecting the glider in a f u 11 I u ff" di vc. In a full luff dive ii is assumed the entire sail is unloaded and flapping. This is equivalent lo saying there is no lifl or altemalively that the resultant aerodynamic force (see Part I) is only drag." This situation is illustrated in Figure ·1. [), is the drag on the rlapping sail and DI' is the drag on the pilot. DI' for a seated pilol (the most adverse position (1·orn a divl' recovery standpoint) in a glider in a "full luff" dive c1t 40 rnph is

about 20 lbs. The value of D, is somewhat more difficult lo determine and accordingly is rnore controversial. If we ignore the incrc'ase in drag due to the flapping of the sail and use this understated value for D,, the dr,1g on the sail at 40 mph would be about 20 lbs. or roughly equal lo the, drag of the scc1ted pilot. I fowevc1· 1 dS illustrated in figure 1, the "moment arm" or IJ .. is about three lirrn's the arm of DI' ... accordingly it is difficult to im,1gine d situ<1tion in which c1 pilolcd Standard Rogallo would not exhibit d positive pitching monwnt in a "full luff' dive. Wfwn you considt'r that the aclual dragon the luffing sail is roughly lo 3 timcs laqwr than the assutncd value (sl'P figure 2) lhe possiblily of

No Ju[

inc1

rig.

Typical drag curvo !or

pamwing.

a 7ero or ive pitching moment in a full luff dive becomes even more remole. Hewitt Philips has calculated thP dive trajectories of piloted Rogallos assu rn i ng drag values similar to the preceding (see Sept., Nov. Crouncl Skimmers). Tlwse trajectories take into c1ccount various values of pitch damping and inilial nose down pitching, and in no instance suggest the likelihood of the extended, apparently stable, type of "flag dive" so often observed. Assessing this evidence we must conclude that the "full luff" dive, as described here, is in itself not the root of tlw

problem. I Comparison between pilot dra~J ancJ drag of

flapping sail.

Other possibllities must be considered. For the divP to be ,JULY, 197(:)

stable lher<i would havP lo he an to 1hr' dive or pitcl1 down as ii hecanw up rnon.: shallow. l'fw lo up c:ould ht' CcH1sed by the li1i onset of luffing in the sail, as but what cou Id c.i use the glider to tt nd ! o down tot lw onset of I uili llcwitt Phi II i psi 11 rden'nU' 7(1\ut 111) n,~""'" ;i11swPr 1 stating th;it if a Standard llo nn,.,,,,," vc1lur: of the 1

co 11 / cf /Jig/J

;)/ SOil](>

would continue lo pilch nos<' down unli I the sail to luff ,ind the resulting incrr:asc in and associated ivP pitch rT1omcnl was just sufficicnl to hal,rnn1 tl1e rwgativc pitch due' lo !he Cn1o. The n'still suhle dive:. l lw ity !he f,1ct 1hc11 the t lw ore ti e,il of dl!dck re substantiated inlo !he f)l!U1J1nir, ion (';Pe Ref. 7) ,111cl tl1e value of Cmo is a s111all v,due of will -rr:sull in a second st;1ble !rim of c1t1,1Ck. Assuming tl1c1I ,1 value of the Ilic cu wh,it I foaturf:s could cause ,1 '""""''"" in low ;.ispecf ratio "st;111dc1rds" ,rnd "cut--l«)els" and what chdr;icleristics could be indicative of a prob1crn with such ;1 Ch;ir(lclcrislics. In all hut rcflc!x in !he kcPI is ,rn absolute ""'' '"''" val1H' o(

in fl incrcnH)lll i11 Ctno, fl igh1 Characteristics A gl id<'r that w,1 n b to go faster l he fastr,r you you have to "hold ii h,H:k1' to it from faster dive should nol be flown A glider that to un 11 trirn 11 lurbu nr,,t,1.nrn, ;\ stand,ird glider without or whose sail does rdully examined. to low ratio

gliders with aspPct r;itios ,,,,, ''""""'I sail forms ;rn• hies ..

value of Cm., (see Par! 11 1 Feb. tlH!se have much bPtter pilch slabil cl1aracleristics lhc1n standards or uJt-kePls, Becwse of the !he likelihood of dive with u,.:.,,µ,,,,:u h ratio glider is small, This i not or i11fl,1tpd i<:)ading liut ly bec;n1sc of the increased carPful, YOU the< onsurncr c1ncl must riot dssurm' that all high aspect ratio gliders have pitch st.1bil NASA found that cylindrical wings, i with little GFlOUND SKIMMFH

twist or· have val uc~s of Cn10 with increasing aspect ralios. these ex l1ibit quite poor pitch stability. A high aspect ratio glider witl1 ,1 negative Cm, will stabilize in a steeper dive than standards with sirnil,ir stability problen1s 1 hec,iuse the (stabilizing) drag 011 the sail will be! quited bit lf'SS, J\ discussion of the dive recovery prolilern c.innot conclude without discussing dive recovery devices arid techThe two "dive devices still us('d on standard gliders, the should be effective in increments in Crno and in a sense make the pitch stability of low aspr,cl ratio gliders more like those of tin, high ralio gliders. Perhaps ilw "hot shots" that scoffed a1 these devices in the past and now fly high aspect ratio gliders with excellent pitch stability characlt,ristics can now appreci,1le their in11 ten1ion. "lrw1·ticil thrnsting has been as a ble rm'<rns of recov('ri ng from "non recover a hie" dives, n a stanilard glider of co11ventional weight and i/e, n analysis by Hewitt Phillipsof the dfectiverwss of inertial control thdt the glider would r·otate about per foot of pilot movc•ment. It should bt" noted !hat this ;rnalysis assumes thc glider to fw in fnic~ fall and in a vacuum tl1e actual rotation would prob,1hly be so111Pwl1;it less in the re,11 situ,1tio11 but could conceivably he bcndici,il if done ,11 nrrw,cr>1,1 the right rnonwnt 1 lly in c1 h aspect ratio glider with relatively low pitch damping. rhc flight chc1racteristics of ;1 flexiblP wing glider i11 dives is obviously complicated the st,illing of this unique i,; equally, if no! more rhe type of stall and lhe of the wing that '.itc1lls first have important effects 011 !he co11trol,1bility of the glider When the stalling of a it is convenient lo talk about "lifl" and lift coefficients." No doubt you have fward that "a typical Rogallo stall,; al a lift copfficiPnt of i1bout I O,, ." What does that 1nean? Recall the discussion of lift and in Part I ,ind the fact that from considerations the gre,iter the lifl to ratio the more efficient 1lw airfoil, it is convenient lo think of ,111 airfoil ,is a "n1c1chine 11 for converting energy into lift is the w,iste of !his "machine." The 1r1,1ss of tlie air and the velocity al which the airfoil moves through the air determines the amounl of Pncrgy availc1blP lo tlw j/rnachi11e 11 di any particular mo11w11L lh(! heavier 1,1,·,nc:,>r1 lllC' ;iir and the the velocity of the airfoil the greater 1he ;rn1ount of energy available to it. The area of the determines how much of the available energy will bl' 11 JI scooped up and actually used by the airfoil, The lift coefficient is simply a measure of how efficiently the airfoil converts 1hP available energy "scooped up11 by the airfoil into lift The lift coefficient change with the ''angle of attack" 011 the Within certain limitations, which we shall soon d the the /\of/\ the rnore efficient the "machine,, is at th<:' lif1 coefficient. A(!rodynamic:ists put it all tnc,ntl1'H lorn1 of an equation this r'qualion with an calculation of the lift coefficient is seen in ·3. Oh! One thing I nearly forgot to mention ... Like all mach this ,,rndc:hine" if pushed loo hard will break down. This 1

breakdown is c;illed stall and it occurs when the of attack, and ;issocic1ted Iifl coefficient, becomes too Aerody11amic;1Jly, stalling is caused by 11 separc1tion 11 of the ilirflow frorn the top surface of the wing . . w,.1tch a stalling hawk and you will occasionally see a foather 11e,1r the trailing edge of the center of the lop of its "pop 11 up. This is due lo separ,1tion of the ai1·flow over the root (center) section. Rectangular wings (Quicksilver, hawk) typically stall at the root. Tapc>1·ed wings typic11ly stall near

the tip. 4) Because stalling means a breakdown in the 11 lift machine 11 and an loss of lift and increase in drag, stalling near the lips a tapered wing can cause control problerns. Despite large amount of twist and camber low aspect ratio Rogallos appi:lrently stall more out-· board than inboard. This results in a slight tendency to "pitch-up" near stall, i.e. these gliders are slightly unstable ratio gliders of moderate nose nPar stall. Most higher angle do nol <1xhibit this tendency. Fortunately the severity of the stall in most high and low ratio Rogallos is quite moderate and predictable. Closr)r examination of the lift C'quation (fig. 1) lends further insight into stalls. Lt>l's assume that a p;nticular still ls ,)ta lift coefficient of 1.0. Everyth else being equal the the load on the wing tlw faster the stalling the greater the wing area, the slower llH, stalling speed. This is true of wing segnwnts .is well, and is the reason that rnany current hdV(i "roacl1cd" tips ro;iching the lips tPnds to lower the load on any tip sPgment thereby irnprovi11g the> stall charac!('1·istics of tha1 section of llw wing. lr1 the landing area of Country one afternoon, I ovel'i1ea1·d one pilot tcll another, "What dn you rne;in would you rather h aspect ratio gliders arc uns,1fe spin in on ,l high performance glider or divP in on ,\ standard?" I would avoid a glider that had <·itlie1· but the comment does have a point speed kills in hang glid Tlwre are two ways to unwillingly atlain the rll)C<'ssa1·y speed, too much wind or too little pitch st.ibil Fortunately tlw typical "high" aspect ratio glidc1·s 1 soon to 11 bcconw the industry's 11 new have' unquc0 sliona· bly excellent pitch stabil Tlw dccept.inn' of these im· proved and the ion of the now obsolete "st,rndard" and "cut keel should result in a nificant decrease in re>l;ited to inadcqu.itt' pitch stability. However, every sweet apple has an un .. palatable core if in ques1 for perforrnance, sweep, billow, tw and washou1 an' reduced to inadcqur1te ;:nnounts even the high ratio "conical" Rog,1llos will suffer frorn possible pitch stabil problems. 11

Hg. 4. Stalling regions on various wing shapes.

Bibliography for Part Ill

HAWK WING

I 1. Hoerner, Sighard F. 1 rluid Dynamic Drag. Published by the Author. Bricktown, New Jersey, 1965. 12. Nielson, J.N. and Burnell, J.A. ''Theoretical Aerodynamics of Flexible Wings at Low v. Engineering Method for Parawing Per· December 1, 196S. forrnance. Vidya Rep. No. . Dornrnasch, Dherby, and Connolly, T.F., Airplane Aerodynamics, Pitman Publishing Corpora .. tion, New York, I %7. 14. Perkins, C.D. and R.E. Airplane Performance Stability and Control. John Wiley & Sons, New York, 1949. 1 S. Roskurn, J Flight Dynamics of Rigid and Elastic Airplanes. Published by the Aul hor Lawrence l<a n.. sas, 1972. 11

.JULY, 1976

VFHY <CIChlC:11'll/l.C Mino iw\kt rhclPr P<l::>\\y de1Pct:, ch,1n~~Ps of /. \nche~:,/ second Thi\ 1s more '1tdfiuent for th0'rma!lm1J or calibr;1Hnq kitC' ,;ink rat('s

/\LW /\ YS IM~'1El)l/\'l'EI. Trdn,,parent ]/ 4 l 01 suspended 8" in front of dt d pomt dbove on(~\ line of J\ir chrunber~ (? q11r1r1) rn1M'niel\tl1J c,,ri,.!CI on one\ Visual rnforr(1I to a movln\J control lMr 1:, clirnlnr11ed

No vle( t1onic L:1~J. No disturbance of 11w quid by (!lcctro11ic noises PHICED ! P\':i d1Nmo\ linl'r (twailr1bl(: nt qrocerv storc,,;)

$:,?SO (C1lifomi<111s ;;dd

tdx). Crnnpletc sunple ins1ru(·tions st1pJ)li('d

sus1wnded ff' i11 front of May <tl\o lle mounted wi1h a

l'11r·rmts 111<0 -cor1wnwnl detennination of !he followin:J ,w1·,cilwi11d Vi:~lodty cmd direction Minimum sink Ii- Maximum

by Wi lvrn B,1ker

Mork IV is cmc:J Martin of Colifomia Gliders.

Det.1ill·d m,1pc, o1 c,ich lot.it ion

Cornpkil' !lying i11,:11w:1ic,1\',

Phntogr.iph', of flying ,,ju,,,

oncJ

T!w book tor

wos nomed Gl'1der of the Month Pacific Trodewinds of Howoii. Colifornio Mork IV trodilion lhot mokes the Wind Wind ihe mork of to come.

MH1 novice pilot ,dike

Original Ml work by Je,rnctte Boe,! irk

SI Nil

Ci\SII, Cl\! Cl< OR MON LY

JO·

SONOI TI\ SOI\RINC IJOX 261

SONOIT I\, I\RILONI\

For informcrtion, ond brochure write Colifomio Gliders 11661-D Sorrento Rd Son CA 92121 452-0351

In our effort to Rating program, we are continuing to 3 and publish the names of all the Hang 4 pilots. To correct an error in the April it should be noted that Hang ] numbers 645 b8 were erroneously listed as I fang 4.

6fl6 f>B7 (,ilil fiB'J

Roger CA flrian Vern Mike Nelson, (,'JO ALrn l,innPIJOse, AZ 691 Pete M. EmgP, CA 692 Al lfoffrnan, NV f,9 l David Ellsworth, CA r,94 Rich,ird Wingrove, TX h'J5 llill llouston, NM 6% Ddve Clardy, CA 697 Scott lloata, MN 69B Tom Crengacy, CA (,99 llill Johnson, CA 700 Rich Iverson, CA 701 Mark Davis, 702 Arthur Sparks, CA 701 Richard Wilson, CA 704 David Cowen, CA 705 Michael Slotton, CO 706 Scuff Wood, WA 707 Wal Lice A11derson, CA 701l Cary Locke, WA 709 John Nichol,,on, CA IO Kerry D.ivis, CA 711 11arry ApgM, CA Greg Smith, CA 71 l Robert Clary, CA 7 I 4 William Riva, CA 71 :i EddiP f.1deo, OK 7 H, M,irk Hicks, TX I [d Coss, CO 7 lll Kim W,1rd, CA 9 Scott Leftwich, TX 720 Parker M,1cCready, CA Gr,rry Kiefer, TX Cary r it1ger,1ld, CA 723 Tylc'r Mccready, CA 724 [ric Rabenold, TX Ronnie Oakley, KY 726 Mike rx 727 Fr.ink TX 728 fed Young, NJ 729 Scott Matthews, WA 730 Mike Courtney, WA 711 Paul Yarnall, NY 73 2 Lynn Davis, NY 733 Jcrrnes Williams, NY n4 Bob Cianflone, CO 735 Rich,ird M. J,ickson, CA 7:J6 Tore Christiansen, Norway 7V Slt;ve Hill, NM TlB Frank Sterba, CA 7l9 llif Huss, CO 740 Scott A. Whittet, TX 741 Doug Foster, CA 742 Stevc> Sarasin, Al( 74l C. Nevin,Nc•wby, KY 7 44 Jirn Thompson, CA 745 Bernard Yagerl, NJ 746 Rich,ml Ford, IA Donald Gross Ill, PA 74/l Gary McDonald, CA 7 49 David Pederson, CA 750 Jeff Walker, NY 751 Tirn Tomlinson, CA 7'>2 llruce Sommer, CA

7:,\ Stevi; McNcPS(', AK lorn Runyon, CO [mil Rolando, NJ 7S6 Keith llalt?, CA Mike Crawley, WA 7SB Raul Rarnire1, WA 7'i9 Dave OR 760 Dave OR 7(> 1 Robert I Jill, CA 7h2 Jack l'atterson, CA 76 l Bob Cerstcin, CA 764 Alex Shortt, CA 76.S F. Kurt Sh,tf<>r, CA 766 Don,ild W,men, CA l'aul llragg, CA 76B Paul CA 7b9 C,iry CA 770 Ron Cuidry, IX I Patil Mossman CA 772 Rick WA 1

774 Ru,sell Hansen, CA John Chotia, CA 77(, How<1rcl Long, CA Jim CO 77B l',llricia CO Aldon Stever, OR 7fl0 Bruce Wilson, NM 7Bl All,rn Kling, OI I 71l2 Moorc', OK ?Bl MN 71l4 Don Matson, WA 7flfi Alan I larmnerel, AZ ?B6 Dave OR 787 Rick WA 788 W.1ync Hoten, KY 789 Ken Hilrrington, OK 790 Sam Wade, WA 791 flerger, OR 792 Trimble, AK 793 Brent Trimble, AK 794 Cr;i1y l>ear, CA 79S Jack Jones, CA 7% Robert Hedges, Jr., CA 797 Cenc Christidnsen 1 NV 798 Dave Christiansen, NV 799 Leamon Hou~,ton, NV llOO StPVP Lantz, NV BOI Edward Sweeney Jr., NV 802 William Wood, NV IHll Arthur Lane, NV ll04 Robert J,1yme, NE BO:i llill Munrby, MS 806 Randolph Alfred, IN ll07 Kevin Carraher, OH 808 Jim W.VA. £!09 BIO Skip Smith, CA 811 Norman Silver, CA 812 Jcrnathan citch, CA IJ 1l J.C. flrown, UT ll14 Jerry Kitchens, TX !J 1S Jorge LJip1,L1rckiP, PA ll 16 Donald Walter, W.VA. 81 [lob Ceoghegan, 01·1 lllB Jackie Lobb, OK 819 fhomas rriltzke, IA !120 Don Yestness, CO 821 Howard Hall, CA 822 Eric McNett, NY

112:l Dean Paschall, CA ll24 Jim Richardson, CA IJ2!i John Brennan, CA ll26 l!utch W,1IIPrs, WA 827 Terry lorpntson, OR ll2B Alvin Owen, WA B2'J Richard Wade, OR WlO Ronnie Youngblood, TX lrli Mik<' Nelson, TX 832 TX

Bll B'l4 fl.Vi Ldnce OK lr16 ferny l'-1 F H37 Rorr loss, B:J/l M,Hk Mocho, NM Hl9 )Pff Scott, CA B40 Steven Sutlon, CA B41 Fra?ier, CA 842 Martinez, CA H43 D,wc Cronk, CA ll44 Raul Conzales, CA H45 Steve Roth, CA ll46 Rkh,mi flry,mt, CA M7 Ron Trivali, CA l\4B Arthur Philbrook, CA H49 llari Thoe, CA ll50 Glen h,lt, CA HS 1 Mark I lonky, CA ll:i2 Dan Haggerty, CA B53 Steve Roach, CA fl54 Clade Thompson, MT HS5 M,iry Sullivan, MT

BS(, HS7 B5H H59 B60 Dug Lawton, CA 1161 lleard, TX ll62 Morgan, TX ll(d Charles Gillespie, IX 864 Jirn Wilson, MO 8(15 Randy Friederich, CO H66 John Olney, CO H67 Charles Porter, CA B6B Art Barney, CA IH,9 13ill P. Walsh, TX H70 Farl llelm, CO 871 David Ramire?, Ml B72 Brad f"hillip',, Ml 1\73 Don CO 1374 David Al ll7'i Randy Price, Al 87(, Roger l<alkhoven, CA H77 Kenneth l'erry, CA 137/l Mike Wilson, CA B79 l'aul Whitehill, CA 880 John C Schaeffor, CA 881 Ed Holder, CA Bll2 Ron J'ptrie, WA B83 Robert A. Ormiston, CA /Hl4 Per Boo, CA BBS Steve Huestis, CA llfl6 Jack Skyles, OR H/\7 David Koester, OR 88H Steve Bronson, TX 889 Doug Smith, AZ ll'JO Kenneth Hall, VA 891 Jacky Cardncr, IX 892 13ruce Lonnccker, CO

89'.l Raymond Frn<'rson, Ml H'l4 Cerw Wil,,on, CA B9'i Thomas lfoward, C:O H% John Deal, WA 1197 Mitchel W,llrous, NC B9B Clate SandPrs, CA 899 Micl1,1cl Cilcs, CA 900 Ray Benson, AZ 901 Bob ID ')02 Lewis ID 90l Kirn Cir;rudin, MN 904 Lew Lawrence, NM 905 Martin W,iller, NM 906 Milford Donaldson, CA 907 Richard Buerm,rn, Ml 901l Edward Townsr,nd, CA ~09 Patrick Hickm,rn, OR

552 Jay Long, Ci\

ss·i Robert Burns, AK 554 Chesley Webber, CA

Herb Fenner, CA 55(, Kevin Beddoe, CA Fd R11chlow, CA 5'ill Don Burmingharn, CA 55') Brad Dement, IX 560 Peter f lughes, CA 5b I Mike Proctor, TN 5b2 Cary Kcwhler, CA 5Gl Blythe Con Iler, HI 564 Chris Curtis, VT 56', Don Post, Vl 566 Simon Smith, IX 567 Jim Griffis, CA 5bfl Marvin Dellr11nner, CA 569 Marty Alameda, CA 570 c,rl Wright, CA 571 Terry Wadina, WI John Buxton, CA John Lires, CA 574 Curtis Colton, CA Cib Eggen, IA 576 Gary DeVoid, CA Michael Dunn, CA 57/J Ankar Magnan, CA 579 )C'ff J. Magnan, CA 5BO Robert Henderson, WA SB 1 Ed Ledergerber, Switz. !ill2 r-red Waugh, CA 583 Danny Rogers, CA 5!l4 Kr•vin End, WI SB!i Mike Harker, W. Ger. 586 Ken Velrno, CA 5B7 John Wilcox, CA 58B John Levy, CA 5B9 Ralph Amrnendolia, CA Richard Stork, HI Harold Spiv,ick, CA S92 Rick Wilson, CO 593 Cerald Fenn, CA 594 Robert Henderson, WA 595 Hill lately, AZ 5% Jay Oaks, NV 597 Max flartness, NV 598 Ciil Robison, NV 599 Mike Luzier, NV 600 Guy Parks, NV 601 Mikel'arks,NV

602 Steve Sheehan, NV <,m Boh Krc,bs, l'-IV (,04 Larry Bohannon, GA (,(JS William Ellwood, 011 606 J. 1louston Chivers, CO f,07 Dean Aldinger, CA 60B Cliff Ceddes, CA Lang, CA Harbur, CA 6 ·11 Dusty Stopp, CA 61 Daniel L,,valley, KS 613 Mark NC 614 Bill Moffett, r, 1:i Steve lhompson, IN 61 b Larry Clausnitzcr, MN (, 1 Neal Roland, MN 61B Ken Westfall, CA (i I CJ David Beerman, CA 620 Mike Sullivan, MT 62 I Steven Reeves, Ml 62 2 Al Kens tier, CA 62"l Jeff W,1de, CA 624 John Angle, KS Steve Smith, KS (,26 Jerry Clilrk, TX 627 lorn l'eadon, TX (,2B William Dowell, Al 629 Robert Ekstrand, IL 630 13ri,rn Engelhorn, CA 631 Steve Seibert, CA 612 Phillip Sergent, CA r,D Scott Williams, Ml 6l4 Blaise u,wark, WA 6:JS Chuck Dugan, CO 636 Bob Gladics, OR 637 John Burkhalter, l N 6l8 Mike Quinn, CA 639 Ronald Markisenis, NY 640 Jack Britton, CA 641 Richard I . Smith, CA 642 John Davis, CA 64l Joe Miller, PA 644 Jimi Youngblood, 1 X 645 Ed Burris, MT 646 Cary Wi Ison, OR 647 Thomas Romanowski, PA (,4/l Dave Guse, ID (,49 Gary Hoisington, CA 650 Wall Conklin, CA 651 RichFinley,CA 6'i2 llill Armstrong, CA 653 Dick Deeker, CO 654 Tom Brown, Ml 655 John Lasater, CA 656 Larry C,1rci,1, CA 657 Peer Suhr, CA 65B William B. Kennedy, CA 6S9 Mend ii, CA G60 Jerry Felice, CA 661 James Gildea, VA 662 Robert Beckey, MD 661 Al Waddill, CA 6C,4 Rob Milligan, CA 665 Bernard Diamond b66 Roger Cleaveland, CA 667 Dave Hirsh, UT 66B Linda Tracey, HI 669 Jack Walsh, CA 670 Samuel B. Chrisman, CA 671 Loyd Price, CA 672 Mark Bennett, AK

JUL.Y, 1976

ILM. Ea.c.h one c.U-6.tom bu.LU :to any '"''"''-"··"1

U.CAJ>\..~j 11e,L<

w);th and mind.

Blac.k Blue. Ye.,€)7.ow

JVlU,\AA.-rJ,c .. ~.

c.oloM 1

$ Allow

MI. 490

c:olo!tl

des101ns. as well as the famous Kitty Hawk Kites two-color hi crnwT-shirts.

on high

T-Shlrl Color and Visor Color

Size (circlo one) Small, Medium, Largo, X-Larqo First choice: light blue, yellow, beigo (circle one) for T-shirts or visors Second choice: rod, whit(1, orange, tan, 9reen,(circlo ono) I encloso $1.00 postage and handling for each shirt and Design (circlo one) 50¢ for oach visor. NC residents add 4% tax. Total enclosed"' .................. . Fly A Kite ... ... $4.25 (5 color desi9n) Surt tho Sky .. ...$4.25 (5 color desi9n) ORDERS PROCESSED DAY OF RECEIPT Get High Fly A Kilo .. ... $4.25 (5 color dosign) Kitty Hawk Kitcis ...$3.75 (2 color design) Name .............................................................................. . Acldross ....................................................................................... City .......................................... State Zip

Send to: Kitty Hawk Kites P. o. Box a86, Head, NC 27959 $1 for poster I catalog

in recent yeors. Kitty Howk l<ites hos of pilots who the This ond now in nine different lr,rr,ti,">m only finest techniques ond Eoch locotion providE,s on om pie"'''"'~''"'" that we con put you in no to wait our 4··6 weels Our experienced conduct Firsr Flight School at most ro fly or selecrin9 10 the

CAf\OLINA

VIRGINIA Howh KilPS·-,,·Richmond

s:l94

Pons Ashlond. Vo (804) 798,,Y/29

(704)

MARYLAND

(7()LI) 96J 4969

Inc Md (J01) 655,,6818 (Q19) 892,5J94

PENNSYLVANIA CAROLINA Oil

Oob Oil City, Po. U\14)

WASHINGTON. D.C

.27959 Md CJ01) 840,,Q2M

Send $2 for poster/cotolo<J Deoler inquiries invited

NEW YOF4K CITY'S FIRST AND ONLY HANG GLIDER SHOWROOM & N.Y. STATE HANG c:;urnNC, ASSOCIATION INFORMATION CENTER

FREE! 1/2 hour mini-lessons every Monday night 7 3D P.M. Showroom hours: Mon., Wed., & Fri. from 7-10 P.M. 225 East 24th St., Manhattan 2nd floor Phone: (2121 889-T745 AERIAL TECHNIQUES SKY SCHOOL FOR FLIGHT TRAINING, MONROE, N.Y. [Just 4CJ milfJS nor'th of N .Y. Cityl PHONE few appointment: (914) 7El3-6751 Train on BOBCAT II by SKYSPOFlTS

Hike out! Feel the balance of this tuned dirtboat as you become one with a machine of 60 mph. Jibe at slide around Winiamnner's ir1f!r1~r111111,,. acceleration

hike up on two wheels: ma1ne1uve1rat>ililty make nA1"fn,·mc~ron parking lot, or field, racing at over twice of the wind.

Ruggedly built of high-tensile aluminum,

can be

ca1rtopp,ect, and sets up in five minutes. Winjammer ... built to take it, built to win.

Thii SUNDANCE has been the leader in field has ,><,11f,~i,nnlnl'<1•

stop there.

CONSUMEFl ADVISOFW: Usml hang glirJers always should be disassembled before flying for the first time and inspected carefully for fatigue bent or denied tubes, ruined bushings, bent bolts (especially thEi heart bolt), ro·used Nyloc nuts. loose thimbles, or rusted cables, tangs with non·circular holes, and on f'logallos, sails badly torn or torn loose from their anchor points front and back on the keel and l(0ading edges. If in doubt, many hang glidinq businesses to qive an objective opinion on thH will be bring them to inspect.

CAL GLIDER 108. Intermediate truncated glider. Hang 3 with all sign-offs. Must sell, pilot destitute. $550. or best offer. 4) 465-1378. Can we help you qet into the air? Do you want to fly, but are short of funds? We will trade anything to help you fly. Contact Dc0lta Wing Glid ors (213) 7876600. CUMULUS VB 18' months old. Excellent condition guaranteed. Must sell to qo to the new 19' Cumulus. With Supine, $830., without, $790. Phil Sergent, Sharon Ave., Anderson, CA f)6007. (916) EIPPER-FORMANCE 1 Flexi Floater, multi··colored, orange, yellow, red. Excellent condition. (408) 377·4066 or PLIABL.E MOOSE 1 , adjustable control bar, cover, extras. 1 yr. old, U.P. prone condition, strong: P/~" tubing throughout. (415) O'K)'VC>VC:, SEAGULL V. Fled with purple L.E. and rudder Excellent condition. Bag included. $700. Box 386, Nags N.C. ~?79!'i9 441 SKYS POFHS BOBCAT 1T New condition Very clean Includes cover. Bruce Linton, Nor. Wood Apts. 06084. (203) Tolland, 871·1B35. SUNBIFlD Hl'

condition. Flown for

months only. Helmet, hardware included. Pasadena, (213) 792·5538

harness, spare Curtis Colton,

STANDAFm Rogallo 18', 90°. Newly brand new dacron sail. Great buy. $400. WESTERN KESTFlEL. 20' 10', custom air brushed sail. Prone and sHated with Benne1t Supine harness NHw bag. $750. CUMULUS II 1 1 , performance intermediate. $450. Prototype Ultra l1igh flying kite. Call L.arry or Mike (213) 429-4756 or 438-3456. WILCS WING 18', blue and yellow. Good condi· lion witr1 bao, seat, new cables. $350. (714) 558-1861. WILLS 19' Standard Excellent condition, green and oold sail, ba~J. seat $450. Firm. (213) 74,

dealers for UP inc., Sun Sail, Eipper, and Cal Gliders. Full parts dept repairs. Alaska Ultralight Flight School USHGA and GSI Instructors and observers private and group lessons. Seated and ski launch. Over 350 Alaskans completed our school in '75. CALIFORNIA HANG GLIDERS WEST DILLON BEACH FL YING SCHOOL. Northern California's most complete hang glider facility. USHGA certified instructors. Free lessons with purchase of a wing. Stop by our NEW SHOP at 1011 Lincoln in San Rafael. Total service, sales and repairs. Come to Dillon Beach and check out the Fledgling and the Windlord. After the sale, it's the ser· vice that counts. Phone (415) 454-7664 or (415) 669-1162.

Almost new, with box $1300. or best offer. Will demonstrate. SEAGULL IV new, flown 15 times. Seated and prone wires. With bag. $750. or best offer. Call (602) 11. Fla;Jstaff, AZ.

CANADA

ICARUS V, Free·f::liqht kit built by Hxperienced craftsman. to fly with carrying box. $900 or best offer. deliver within reasonable distance. of Fresno, P.O. Box 589, F'resno, CA 93708. 439-4769.

AUROFlA ROGALLO, INC. Dragonfly, SRT 20x16 RT 19x17, Fff 18x16, Seagull Ill amJ IV, glider hardware, sales, vice, and instruction. Box 9·1176, West Van· couver, Canada V7V 3N6, (604) 922-7275.

spoilers, cover, truckrack. OUICKSILVER B Vory qood condition, very stalJle. Flies great $500. (714) 737·8899

COLOr'lADO

ALASKA ALASKA HEU COPTER Hang Gliding tours. Vertical Fliqhts up to 6,000' Write or call for Info. Box 4-2990, Anchorage, AK 99509 (907) 274-4120.

GOLDEN SKY SAILS, featurin(J Sun and Seagull Our well equipped shop specializes in expert and custom work. Huge inventory of parts amj accessories, includinq Chandelle replacement Fast service mail order. Regular, and l1igh-performance lessons. Mountain fliqhts up to 2600' vertical. ailable. Located just west of Denver at the Green Montain. Call or write for free price list or further information: (303) 278-9566. 572 Or-

For more information and reservations, write or call The Delta Wing PO Box 483. Van Nuys, California 91408. Phone 3) 785·2474 or 7B7-6600.

instructions on the student into the the instructor.

Gf:iOLJND Sl<IMM[fi

chard St., Golden, Colo. 80401 IOWA IOWA Glider Co., Central Iowa dealer for Pliable Moose, New and used gliders, lessons, parts, repairs. 2564 Boyd, Des Moines, Iowa 5031 5) 262-5080. KANSAS and Blackhawk Kites. instruction. outfitting and sales for canoe and kayak trips. Stop by and shoot the br<,leze! Pack and Portage Shop, !5935 Merriam Merriam, Kan66203 262-6611 MASSACHUSETTS

est Quality. Kits $335-$455. F~eady to fly $455-$575. Michigan distributor for Complete stock of supplies, instruction, sailmaking. 2275 S. State, Ann Arbor, Michigan 48104. (313) 994-9020. Send $.50 for information packThe Midwest School of and the new Flexi· Cumulus VB, thEi Flier II, as well all other mod<1ls of Eipper, Wills Wings, and the Kostrel available for demo flights. We have complete line of accessories and instruction in all levels of hang including lessons on the Quicksilver B & Our training is t1one at the Warren Dunes since we are located 3/4 of a mile north of the park entrance. Call (616) 426-3100 or write: The Midwest School of Hang Gliding, 11522 Flee! Arrow Highway, Bridgman, Mich. 49106.

Try a FREE practice run at Aeolus Flight Training Center, Groton Hills Ski Area, Groton, MA Aeolus instructors can teach you to fly easily, and are certified by USHGA and Open Saturdays and Sundays. Weekday instruction by appointment. To enroll, contact AEOLUS HANG GLIDER, INC., Box 184, Littleton, MA 01460. 486-8278.

WINDSURFING Become involved in an incredible water-wind sport. . discounts on wind· surfers given if you live outside of Michigan. Con· tact our certified school for more information. E.T.C., 12173 East D Ave., Richland, Ml. 49083.

MICHIGAN

NEW ,JERSEY

full fivEi lines of tow Discounts now \Jiven on the amazing Cirrus 3, new, your choice of colors. For complete information call (616) 629-4481, or write to 12173 East D Ave., f=!ichland, Ml 49083.

INC., Autborized dealer Gliders and in stock cable and tubing. Send forrsmnnllatc. of information to: SKY ACTION INC. 16 Weir Place, Ringwood, NJ 07456. NEW YORK Hang Glider Shop, representing eight major

manufacturers. instruction with USHGA and GSI certified featuring Bennett Phoenix training kites. Complete hang gliding and towing accessories and repairs including tube New and used kites. Mark Flight Avenue, Buffalo, New York 1 836-3939 FlOCHESTER HANG GLIDER, lessons, parts, new and used gliders. Dealer for For· (71 381··0075. mance and WINDBORNE HANG GLIDEf1S Electra Flyer, California Gliders, Eipper, Manta, U.P , Zepliyr, Seagull. Parts, accessories, storage, flight instruction. Skateboards too. 159-11 Horace Harding Expwy., Flushing, N.Y 11365. (212) 461-1314. 40 miles north of N.Y.C. Aerial GSI Certified Beginners School with advance trainer kites. Dealers for all Manufacturers. Everything for the beginner, intermediate, and advanced pilot. Dan Chapman, James Aronson, Douka Kaknes, cledicatec! to the hang gliding movement. (914) 783-6751, F1D# I, 49 Mine Rd., Mon-roe, N.Y. 10950.

UTAH Hang Glider parts, repairs and compehrnt instruction. Free lessons when you buy a Manta The Kite SLC, Shop at Nature's Way, 0th So. 9t11 Utah 84102 ) 359·7913. WASATCH WINGS, dealers for Sun Sail and Aircraft. Expert instruction at reasonable

Serving the Midwest for over six years with quality Hang Gliders, equipment and service.

PEARL RD. CLEVE., 0 44101 PHONE: (216) 398-5272

Enclosn check or money order with coupon and snnd to:

In There Avenue South Minnesota 55423

trial, 90406. $6/yr 6301 Knox Ave.

FLASH! "WINGS OF THE WIND" just been nominated !or an EMMY! W.O.W. is hot new California film t11at shows the humorous attempts at flight by beginners to get "up" it stresses the scientific of molorless flight and it offers the viewer a sense of freedom well brief history of the sport. An ideal film for club prernotional and entiirtainment 16mm minutes with sound. $300. GibCo Films, 12B14 Collins St, No. 91607 3) 7RFi-::l~tm, PATCHES & DECALS lems dia. Full color Inside or outside ap1Jlic:ati1:in. 13¢ for Box TEE-SHIFffSwith USHGA emblem $5.50 includ· and Californians add 6%, ing tax. XL. only. 90066 USHGA, BOX 66306, Los per The rate for classified advertising word ol characters). Minimurn charge, $I is charrJed !or each tJrapt1. make checks to Classified GROUND SKIMMER MAGAZlf\JE Box 66306, Los Angeles, CA 90066

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rmmthly in to ultralight flight enthusiasts Inc. Subscription is aw3ilable to ever·yone as

right now and

in touch with this fast developing

MEMBER. I enclose $ 'I 0. 00 11. forei[~nl dues to Cbecome/remJw asl Member in the Unit cJ tate lfang Gliding A n., Inc., effective with the mo t recent issue of SKIMMER. I understand that this accords me a voting privilege, and that 00 of the Member dues are frn' to GROUND SKIMMER. LJSHGA

pr·intl Name

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for· annual dues (c~nter·/r'Emewl as Family Members 00 each, in the United States Hang C,;liding Assn., Inc., the following named per·sons who r·eside in my household. I under'stand that each will receive the same as full Members that they will NOT r·eceive a subscription to

FAMILY MEIVIBE:FL I enclose

Name

PTION. I enclose annual dues for· the following per·scm to Umter/rerrnwl full Member at $10.00 11 .00 foreign) in the United f3t,Jtes Hang Gliding Assn., Inc., c3ffc:lctive with the rnost roci:mt i1,sue of I that this acccwds a votin~J , and that .CJD of tho Mernbor dues are for to GROUND SKIMMER. Name

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check m· rnoney order tCJ: USH Cl630El LO , CA. 90066

Amount

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QUANTITY

UNIT PRICE AMT.

ITEM

... $ .25 .50 1.00 in 5.50 3 00

BOOKS Rick Carrier·, Basic information on

''.''

and conditions for flying in Ar·izona . Finley. A handbook

7.9[5 4.95 2.50

for Southern California, by

Cleveland, 2.00 :3.95 5.95 3.95

by Dedera. 145 pages. Pictornl !-,t,r:>nt,Pr Mccarroll, pilot comments . cJe1::;im1ecJ es1oec;ially for· han1.J for making cornplete 4W' x ''' Basic Handbook of tow-launched hang-gliding Hai·dbound, and modern

8.95 2.95 3.95

Hang Gliders, by guide to hang []liding , , instruction/construction manual . , , . , .. u.11.11.11111'\lt:11, by D, S. Halacy, ,Jr•. 185 pgs, All about 4.95

POSTCARDS .. 10for$1,00. . for flying prone. take-off, Color W,A, Allen , I '.r,nnk•1rc, brin(JS hang,,gliding tO ar•eas With little Color photo by W.A, Allen

Californians,

GROUND SKIMMER Back.Issues pecify by circling the issue number·, available are: MIMECJC,RAPHED COPIES: 1,~,~, ...,,~,, PRINTED COPIES: 19,20,2'1,c:cc.,c:cc:i,c:c•-,,c:c1, 30,31,32,33

for issue) ..... .

Subtotal add 60/o sales tax ... ,, ,, Total

, .$ .50 " ' " " ' " .$ 75

Ap1Jlicaticm Form (#4l Form (# 1 51 USHGA Form (#141 F1ating Program [ # 16) film rental sent upon request

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Cronk: rloxi soaring Pt. rurmin with Dave Mue/1/, 1975 /Jang Gliding Champion

like the tip feathers of birds, this new Dick Boone sail design produces incredible performance coupled with unsurpassed three axis control and stability, The radial tips 0> allow for: • improved 1!4 chord sweep • less sail billow (1/2 °) permitting high penetration without sacrificing good parachuting • reduced induced drag • better washout curve • pre· vention of tip stalls and flat

the VI-B gives you performance you need for winning meets, High speed glide for speed runs, yet VI-B slows down to 200 FPM for aerial slalom and when it's time to land, it's DEAD CENTER on

and has proven it's excellent thermaling and is a breeze because of it's excellent roll areas to another thermal, the VI-B's top Invited

DEL Tl\ WING KITES and GLIDERS, Inc. 13620 Saticoy Van Nuys, California 91408 PHONE: (213) 785-2474