Low & Slow Issue 15 1972 by US Hang Gliding & Paragliding Association

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s&elfl THIS ISSUE: An answer to several hundred requests: {For your study and enjoyment) Self-Soar ~ssoc. here presents the complete 1909 Biplane Hang-glider Plan by A. Powell Morgan. r (BEWAR.E: Class l only) FRONT COVER: W.A.AJlen photo of A.Powell of Pomona.CA. at the 1972 Self-Soar Otto Med at Pl.a.ya dcl RC"y. Art Powell won the praise availa~le for showing best the virtues of an improved 1909 biplane hang-glider ---see this is{>ue. BACK COVER: Photo by W. A. Allen of Ron Klemm·cdson in A-S-Whoope'!. Ron won; top biplane hang-glider praise during the self-soar aspects of a northern California. Otito celebr,;1,tion, 1972. As soon as you celebrate Otto this Otto Sea.son, please send in photo and story to LOW & SLOW at Self-Soar Association: ,

59 Dudley Ave .. Venice, California. The intei="n'ati.oii.al committee on self-soaring ~ight analysis combined with the committee on sclf-soariit",g safety to give us a first draft. of definitions on self-soaring clas.~ifications. Sec Low & Slow II !or the c!ass descriptions.

. Reports of your- local sel£-soarJg are welcome. . LOW & SlOW will publish all that it has ceived. Issues will be coming out about weekly for- a while so your questions are ore rapidly answered. We h.avc an average staff load o{ 7 people right now to do this.

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Copyrightrc-'\by Joe Faust. 1972 i You may have life membership in Seli"!-ioar Association by application using the special form ~bat you will find in a coming issue; no membership fee; services rendered through mail and at meets. All issues of LOW &: SLOW are available singly at $1 or in sets of: twelve is.sl ues 1 consecutively numbered a.t $6 in these sets: l- J2. If 13-24 i, #25 will be out Sept .• 1972. I These issues a.re periodical news issues serving a self-soaring interest. Send all personal and businlss correspondence to Self-Soar Association, 59 Dudley Ave .• Venice. GA 902.91

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PREFACE. PREFACE.

CONTENTS,

Gliding flight is a comparatively new field for modem aeroplane, namely the warping or twisting :he amateur to delve in., but the time has arrived of the ends of. the planes to secure lateral stability .vhen it is being extensively taken up both as a when a gust of wind strikes one end of the machine. cu ... n1rn l. In this manner the Wright's continued their ,port and a means of experiment. The Framework. Assembling and finishing the wood. !I ~!any ,very costly aeroplanes have failed to fl.y experimenti. until every move had become a matter of habit and to balance and guide an hr9.ause of man's total inexperience in the art of CHAPTER II. :lying. All of the great aviators now before the aeroplane was almost an instinct. Covetjng the planes, Laying out the fabric and A gasoline engine was then fastened in the maworld, whose machines are the result of their fastening it ................................ . :,wn genius learned to fly before succeeding in ri chine and connected to drive two screw propellors motor driven machine. ' at the rear. Dec. 17, 1903 the machine flew for a Cn,n1s1, !II. The Wright. brothers spent no less th,rn lhre,, f<:w seconrls. The h·aps and hount!s. with which aviation has Trus~i·nR'. Fa~;h:nin~~ thf' ti1.? roJs rtn<l tn1t.•in~{ the years on the sand dunes ne,t1· the coa,-.t (It ,'i, ,n 11 · glit.lcr... . .......... , ....... . :r; Caroli!1a making gliding /lights. They ar,pruached since pr<.,gre~:sed both in the hands of the \\Trights and others is a matter too well known to be rethe difficulties in a methodical manner, working . CHAPTER l\'. out. each problem and determining which 1\'as the peaterl1 Gliding Flittl,t '!'Ii,~ f,ri1h·iplt·~ involve,1. In':itructions There is therefore no excuse necessary to be best means of accomplishing a certain re:;u\t. :ind pr..:c:lutinn·..... . ............. . 44 .· To control t~e tendency to pitching, they de- made for Lhis little book, coming as it does at this time and it is sincerely hoped that it may interest " 1scd an el~vat1on rudder and· attached it to the CHAPTER V. front. of thetr machine. The next step was to de- and lead many to experiment first and build their Rcm::..rks 55 te~mme whether equilibrium should be main- aeroplane afterward so that whrn their machine tamed by shifting the centre of gravitv <>r i( there ·is compkte it may be practical anrl not intencled ~·as not a better method and they intr~ducecl what to operate ir. some " lift-yourself-by-your-bootI/1s probably the most valuable feature of the straps " manner.

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81-Pl,ANE C:J.IDER

lll-PLA:S:E GI.IDER

The framework is composed entirely of selected an active supporting surface of 152 square feet spruce, straight grained and free from knots. which is sufficient to carry the weight of an ordinary man. A machine having a larger surface will Spruce is very dense and tough but yet one of the THE FRAMEWORK. support the sanie weight when moving through the lightest of woods. A gliding machine, more often popularly termed air at a slower speed, but larger surface means an The dimensions given arc for the finished pieces a glider, is simply a motorless aeroplane, operating increase in s.omc of the general dimensions. An after they have been planed up. The usual method increase in surface by lenglhcning the planes will by force of gravity to carry its passenger sailing of finishing wood for aeronautical work, so that through the air from the top to the foot of a slope. make the machine much harder to keep on an even it has a hard glassy surface and offers little rekeel, while increasing their depth in the direction ~istance to the air is first to give it a thorough The glider described herein is the type developed of flight will require greater agility on the part of brushing over with hot glue and water. It is by Octave Chanute and may be considered as the the operator to keep the centre of gravity in the rubbed down after drying, using fine sand paper. parent of the biplane machines with which the world proper position. A larger machine also means The wood is then given a coat of thin shellac. has, lately become so familiar. The machine is more weight and a heavy ll}achine is hard to make This is rather a tedious operation :i.nd instead known as a biplane since its supporting surface a landing with. On the other hand a light glider is dangerol!s and some may pref er to first smooth up the wood by is in the form of two superimposed trussed planes sand papering and giving it a coat of spar varnish. vertically above eac!J, other and having a tail in will not stand any rough usage. The corners of all the woodwork are rounqed off the rear for the control of direction. The cost of the glider, provided the construction so as to reduce the resistance offered to the air. There is always a tendency among experimenters is accomplished by the intending owner is so low to depart from the design and dimensions of a.ny as· to place it within the reach of any person of Horizontal beams. The principal members of machine or apparatus offered for construction. ordinary means. The expenditure for raw mathe planes when smoothed up should measure This, since it develops originality is a good indica- terials varies greatly. It is usually a little less than 20 feet long, 1! inches wide and i inches thick .. tion, but most of those who will undertake to build $10.00 and should not exceed $15.00. A finished Four of these beams are required. In some lumber a glider are attempting something altogethet new glider is worth from $50.00 to $100.00 depending yards, twenty foot spruce free from knots is very am.I so any radical change from the instructions I whether or not more than one is made at a time. hard to secure and so instead, two 20 foot pieces in this little booklet are unadvisable. I may be spliced together at the centre as shown in Housing. One of the first considerations is It is better at first to benefit by the experience' Fig. 1. of others. The glider here described is considered usually the housing and storing of the glider, but II as the standard " of the biplane type. It has the machin(l linder consideration is so designed that Th tri , f t d has the sam •i 0 • • 11 k k dd " e sp11c ng s p IS 5 ee 1ong an ... 9. it may be quickly ta_~e~I)_art or . noc _e_ o~-- t'1011 .. s the-be ms. save for a distance-of and lie-put·away in tlie cellar, under tlie porcli or cross-sec a a • . ~~~~~~~~~~ in some other out of the way place. CHAPTER I.

BI-PLANE GLIDER

down-to-t-inch-thick. Six-holes are-bored-throug-hthe splicing strip and the beams so that they may be fastened together by means of, six ti: inch round headed stove bolts. The holes are Iocateci so that .the space between the two centre bolts is six inches while t~ others are located one foot apart. A large washer having a small hole in the centre is placed under the head of each bolt as well as the nut.

iusfratedin F1g. 3~ -Th.etwo in the centre are two feet apart and the others respectively 4 feet 6 inches and 9 feet on either side. The struts on the upper plane are place<l so that the projections ,come above the horizontal members. Those on the lower plane are placed just the opposite, that is so that they come on the under side.

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Struts. Each pair of horizontal beams are held parallel to each other and three feet apart by si.x horizontal struts. The form of these struts 1~ illustrated in Fig. 2. They are three feet long and t x 1t inches in cro~s section. A notch lt x t inches is cut in each end so as to form a projection l t x ! x t inches. The location of the struts in the plane is il-

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They are fastened with one or two small wire nails and then secured by means of a clamp. Two dozen clamps arc required. They arc bent out of a strip of sheet brass one sixteenth of an inch thick, 31 inches long and 1 inch wide. The ends are rounded and a t inch hole located and bored in each as in Fig. -1. The clamp also serves to protect the under side

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of the beam from the action of the nuts on the ends horr,l ancl finishr,J or can he procurrrl at a foundry. an outside diameter of one inch and one quart,·,·. of the eyebolts. The method of fastening 1.hc They arc prcfrrnl ,ly made 11f aluminu1n which metal is at once light and strong ln1t brass or even It is one inch high ahove the base. Two t in; ', clamp is detailed a little later. iron maY liL· used if it is ncct•ssary to avoirl expense. holes are bored I I inches apart in the bnse. T\•," smaller holes } inch in diameter arc hore<l 1";; in,_·,, Thcr~ arc other methods of joining the stanchions nearer the ends of the base than the lar~cr !wk-·.. The wooden pattern is made from the dimensions indicate(! in Pig. G. It is thoroughly smoothc·l up by rubbing with sanr\ paper an,1 then gin~n a coal of shellac. ,\II parts, should have fl. very slight taper towards the top so that the pat tern may be withdrawn easily from the sand mould. I

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Stanchions. The planes are separated by twelve stanchions, four f~t long and J of an inch in diameter.

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If the interior of the mould is coated with lampblack, the castings will require no other finishing than boring the holes. 1/01\.. ...., Two dozen of these sockets arc required. Six Fm. 6.-Stanchion socket. are fastened to each of the four horizontal members by mel'-ns of round headed wood screws which pass 1' to the beams but the use of the socket is recom- through the smaller . holes· in the base. Tlw FIG. 5.-Stanchion. mended because it is the strongest method and sockets are located exactly opposite the enJs • ;( also permits the glider to be readily taken apart. each strut so that when the stanchions nre in They are rounded and s_moothed up so that the The base of the socket is 3t inches long_,__1 t inches _place,_they_will be_sep_arated by the same distai.1rcs ends will fit snugly into the socket illustrated in wide and t of an inch thick. The cup has an but all lie in a plane at right angles to that in Fig. 6. These sockets may be-p1,1rchased* already internal diameter of seven eighths of an inch and which the struts arc. v, I

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BI-PLANE GLIDER

Bl··PLANE GLIDER

A t inch hole is bored 'through the horizontal. ieam directly under each one of the l inch holes n the base of the socket. These holes penr.:t an iyebolt to pass through. The eye bolt is illustrated n Fig. 7. The stock is t inch in diameter and :hould be at least two inches long under the eye.

the under side directly opposite the holes in the strut clamp. A nut placed on the under side as in Fig. 8 will then hold the clamp tightly against the under· side of the beam and secure the position of the strut.

19 20

Ribs. Forty one ribs support the cloth forming the surfaces. They are each one half an inch square in cross section and four feet long. They are fastened to the horizontal members one foot apart, flush witH the front and projecting

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them an increased carrying capacity and add to the gliding power. The best method is to steam· the ribs and then bend them so that when they dry they will retain their curve and not tend to push the horizontal I

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The diameter of the eye is one half an inch. These eye bolts are obtainable already threaded and ready for use with a nut and washers, but can be procured somewhat cheaper in blank form and threaded by the purchaser. Four dozen are necessary, two for each socket. The eye bolts pass through the socket and beam, coming out on

one foot in the rear. One or two small wire nails I ::i are used to fasten the front ends and then a clamp :i: placed over them and screwed down with two.No. 5 i round headed wood screw:s, one half an inch long. 1-_---1 .. J A small brad awl should be used to make a hole Fro. 10.-Rib clamp. before starting the screw and so avoid any possibility of starting a split in the wood. beams apart. Only a very slight curve should be The clamps are bent out of sheet copper strips, given and the amount of curvature should be the 2t inches long and i of an inch wide. The ends are same for all the ribs. rounded and a hole bored through which the screws Some designers construct gliders having flat may pass. planes, intending that the pressure of the air underThe surfaces of the planes arc curved to give neath the fabric shall produce a natural curve ~

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but such a method is exceedingly poor practice and results in a very incllicient machine. The ribs must be perfectly rigi,l and th<: fr.:.mc of the whole machine strongly trussecl so that it cannot possibly be distorted by the air ;ircssurl'. The following extract frum the report of the Smithsonian Institute well illustrates this point. " This new launching piece die! its work effectively and subsequent disaster was, at any rate, not clue to it. But now, a new series of failures took place, which could not be attributed to any defect of the launching apparatus, but to a cause which was at first obscure; for sometimes the aerodrome, when successfully launched would dash dciwn forward and into the water, and sometimes (under apparently identical conditions) would sweep almost vertically 1,1pward into the a;r, and fall back although the circumstances of flight seemed to be th~: same." The cause of this class of failures was finally found in the fact that a.• soon as the whole machine was up-borne by the air, the wings yielded under the pressure which supported them, and were momentarily distorted from the form designed and which they appeared to possess. "Momentarily," but enough to cause the wind to catch the top, directing the flight downward, or under them, directing the flight upward, and to wreck the experiment. When the cause of ~the-difficulty-was found--the-cure was-not-easy.for it was necessary to make this great sustaining ·surfaces rigid, so that they could not bend."

The report in question refers to the experiments conducted with Professor Langely's model aerodrome. Some cxperinwntcrs claim that the parabolic curve gives the greatest lift with the least power require,! for propulsion but it can be safely doubtC'd. The \\'right machine is probably the most efficient in existence. Their curve is very nearly the arc of a circle and is not of the parabolic form. Four per cent is about the proper curve to give the planes of a glider. This is about two inches for ribs four feet long. After fastening the front end of the ribs, curve them up in the cantre by pressing down on the loose and at the rear. Then nail the rib to the rear beam. with a small wire brad and screw on the clamp. The nails prevent the ribs 'from slipping longitudinally while the clamps serve to prevent them from moving sideways or pulling off when 'the fabric is under the pressure of the air. Fig. 11 is a plan view of the top and bottom planes. Twenty one ribs, each one foot apart re used on the upper plane. Only twenty ribs required on the bottom surface because an pening two feet wide must be left in the centre or the body of the operator.

Arm pieces. The operator is supported in the chine by two strips of wood passing under his pits. Th~ arpi__p_i~ are 3 feet long, 1 inch 'de and lf inches deep •. They are fastened ·to the horizontal beams by

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means of a -h inch round headed stove bolt. The aTstaric:e betwetin" should be just wide enough to be comfortable and is variable with ~he breadth of the operator between his shoulders. Thirteen inches is about the proper distance for ~he average person. The upper.. side of the arm pieces is rounded so that they will .not be quite so uncomfortable as they would be if left square. It is

25 26

Bl-PLANE GLIDER

glide in the direction in which it is started or head ~-The----horizontal-plane-is-fitted-together-with-half--onTnto the wind. The horizontal rudder steadies. and half lap joints. It is first fastened with nails the machine longitudinally and prevents the ma- and then reinforced with brass comer braces. chine. from suddenly diving or pitching. Neither of the rudder planes are movable. The separat~ parts composing the framework are illustrated in Fig. 13. ..c-..--i!L·-:M I I !'

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Corner braces are also used to strengthen the vertical plane.

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not a good plan to pad these pieces by wrapping The cross section of all the sticks is the same, them with cloth for it will impede the movements namely one inch square. The t11·0 long beams, of the body in balancing. A, are 8 feet 11 inches long. The two uprights, H, Rudder. The rudder is composed of two planes each 3 feet 10 inches long from the vertical members at right angles to each other and in the rear of of the directional plane. The horizontal plane the main surfaces. The vertical portion keeps the is made up of six horizontal strips, two of them, C, machine headed into the wind and causes it to six feet long and four, D, two feet i.i length.

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The rudder beams are stepped into sockets on the body of the machine so that the rudder is detachable.

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A short cross bar 2 feet, 11 t inches long and Iix i inches in cross section, is ia,tcnc,l ucl ween the two centre struts of both planes at a pnint eight inches forward of the rear \,cams. These cross bars carry one of tile sockets mentioned above as also do the rear horizontal beams. The cross bar and sockets in the upper plane slwul,l be directly over those in the lower plane but in an inverted position.

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The construction of the sockets is illustrated in Fig. 17. The smaller one is fastened to the cross bar and is bent out of a strip of rtJ inch sheet 1 brass 4! inches long and t of an inch wide. The · larger socket is the same length and thickness but is lt inches wide and is fastened to the horizontal beam. Two of each size are required. The ends __ are.rounded and a fa- inch hole bored in each so that a fa- inch round headed stove bolt may be used to fasten the sockets to the framework.

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A hole is bored in the centre of the top of the nailer sockets so that a bolt may be passed through 1e rudder beam and cross bar to prevent the ,rmer from pulling out. The two sockets in each plane must be in perfect · .ignment and lie on· a line drawn at right angles ) the horizontal members through the centre of 1.e planes. In Fig. 15 it will be noticed that four bolts pass :uough each plane near the corners. The bolts re fo inches in diameter ,and serve to fasten the iano wires which brace the vertical and horizontal ,lane to each other. The complete framework of the glider without he tie wires and the ribs on the lower plane will .ppear as in Fig. 19.

COVERING THE PLANES,

The surfaces of a motor driven aeroplane are. usually made of some material which is practically air tight. The Herring-Curtiss Co., use Baldwin's rubberized silk, while most of the foreign aviators prefer a balloon cloth known under the name of " continental." Ordinarily the surfaces of a glider are not covered with any preparation to make them air tight and is not necessary, but since it will considerably increase their efficiency it is offered as a suggestion to those who are able or care to undergo the expense.

Aero varnishes for this purpose are obtainable in the.market and may be applied with an ordinary brush or by immersing the fabric. One gallon will cover approximately 100 square feet of ordinary <:ambric, although much depends upon the weave. The more open or coarser the goods, the more varnish it will require, while fine fabrics take the least ·amount. Varnish is expensive and is not considered in the estimate of cost made at the beginning of the book. 32

.BI·PLANE GLIDER

The surfaces are formed of cambric or muslin stretched tightly over the ribs. Thirty yards of material, one yard wide will be sufficient to cover the machine, including the rudders. Seven strips 4 feet, 6! inches long are cut and sewed together along the selvages so that a surface 4 feet 6z inches wide and a little over 20 feet long is formed. Twenty one strips, 4 feet 6! inches long and 1! inches wide are cut and sewed to the surface at right angles ~o the long edges and one

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that the result is a two inch hem, composed of two thicknesses of cloth save for one inch back from the edge where it is made up of four thicknesses. This reinforcing is necessary to avoid ripping and tearing the cloth out from under the tack heads when it is ul'ider pressure during a flight.

the top plane just described but are one foot less than half as long.

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F10. 20.-Method of hemming. up edge of cloth.

foot apart, between their centre lines. The edges of ·these strips are turned under t of an inch on each side so that they form a reinforcement 1 inch wide which will come directly above each rib.

"'" of cloth hemmed, and reinforcing strips Fm. 21.-Section sewn on,

The bottom planeu. The cloth on the bottom Reinfor(mg. The long edges of the surface are then doubled back and hemmed, turning under t planes is made up of two sections, divided by the ·of an inch and forming a 3 inch hem as illustrated space in .the centre of the lower plane which the iti the upper part of Fig. 20, This 3 inch hem is :operator' occupies. These sections are. made. and tnen aoubled back one inch and sewed again so reinforced .fo- exactly the same. manner as· that, for

The cloth is tacked over the front horizontal beam and then stretched tightly over the curved ribs and fastened with tacks at the ends. Fasten the comers of the cloth first and smooth it out before driving the tacks in the ribs. Ordinary brass headed upholsterer's nails are used but they should not be long enou,gh to pass all the way through the ribs. A strip of felt i of an inch wide and four feet long is laid on the cloth directly over each rib so that it comes between the head of the tack and the cloth. This· precaution may seem unnecessary to some, but it greatly reduces the liability of having the cloth tear when. under pressure. The tacks along the ribs are spaced about 4 inches apart A heavy weight''held against the under side -of· the rib by an assistant; when the tacks are driven m will provide a firm foundation to hammer ·".gainst. A .very good method of fastening the cloth to foe ril::is is to sew a pocket on the under side of the surface and into which the ribs · may be slipped. The rear ends of the ribs may be fitted with metal tips by tapering the end down t1ntil it is round and measures 1 an inch in diameter. !.. l inch brass ferrule such as that used on fik_handles · is then forced on, ~

CHAPTER III.

BI-PLANE GLIDER

TRUSSl?-.G.

The rudder planes are covered on both sides. The fabric is stretched tightly over the frame and then tacked along the ~dges. The edges should be turned under before tacking so that there is no possibility of the cloth tearing out. The cloth at the ends of the planes should be securely fastened to the struts by means of tacks. This will relieve the ribs of some of the strain and correct a tendency for them to pull in towards the centre.

The strength of the glider lies in its proper trussing with piano wires which when tightened up should so brace the framework that it will support without appreciable sag or strain, a heavy man hanging from the arm pieces and the ends of the planes resting on a pair of carpenters' horses. Two methods of trussing the ?lanes are illustrated in Fig. 22. The machine is divided into five cells the vertical boundaries of which are formed by the stanchions. The first method illustrated ,s the one used in this c::ise for ihe glider. ft is so111e\\·haL simpkr than the second a~ Joes not require the use of any turnbuckles. Each wire is fastened to one c,i lhc cvebolls nn the horizontal beams and then run cliagun;dly across to the sockot on the opposite bc·am in the uLhcr plane,· considering front and rear to lJc opposed. Four of these diagonal wires, reJJrcscntctl by j in Fig. 23 brace each of the four large cells. The middle cell cannot be trnssetl up in this ma11m'r because the wires would interfere with the uody of the operator. So the rectangnlcs formed uy the two centre struts with the upper horizontal 37

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Bl·PLA:s!E GLIDER

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beams and the two centre rear stanchions with the rear horizontal beams of the upper and lower planes, are braced by means of wires runnin~ across their diagonals. The rudder is stiffened and trussed to the planes by sixteen wires. Two of these F and H ru,i" from the top of the vertical rudder plane to the lower sockets in the rear, H, feet from the ends of the planes. The corresponding pair E and G run from the bottom of the 'rudder to the top sockets of the same stanchions. Four wires A, B, C, D steady the horizontal plane and run fr~m its comers to the sockets in which the rudder beams are stepped on the frame of the glider itself. The remaining eight, indicated by I in the illustratio11, brace the horizontal and vertical planes of the rudder to each other. Fig. 24 illusj:,rates .the method of anchoring piano wires. The wire is first passed through a short piece of i inch copper tubing about i of an inch long, then through the eyebolt. The end is doubled back passed through the tube again but now in a reverse direction. By bending the extreme end of the wire over in the form of !,I. hook and shoving the tube down close to the eye bolt, the wire is secured and cannot pull out. The other end of the wire is fastened in the same 'manner but before the end is bent over into a hook, the wire must be first pulled tight.

lll•PLA:-E GLIDER

After fastening all of the wires their tension may be regulated by turning the nuts on the lower ends of the eye bolts. It is very necessary that the frame should be perfectly true and not warped or twisted. Otherwise the machine will be very hard to balance and manage when making a glide. Especially must the rudder be true with the rest of the machine.

Fm. 2.4.-Method of anchoring wires.

Since there are no eyebolts about the rudder which could be used to tighten or loosen the truss wires, a turnbuckle must be included in each wire for that purpose. Turnbuckles. The construction of these turn-buckles which are very simple and inexpensive is

BI-PLANE GL!DEfl

Dl-PLA:-IE GLIDER

illustrated in Fig. 2,>. They are made of a bicycle spoke and nipple by cutting off one end of the spoke and using the part which is threaded. The encl of this piece is bent bi!ck and twisted into an eye. ,\ piece of ti; inch sheet brass ·} x i inch has a hole bored in its centre. the diameter of which is such that it will just< admit the spoke nipple. The nipple is prevented from passing all the way through by the &houlder on one end. A piece of sheet iron ! inch wide and 3 inches long has a

formed by the stanchions with the horizontal beams. This method is used on almost all aeroplanes and is considered the strongest but ·the first method is plenty strong enough for an ordinary glider. If after. trussing, the machine is found to be warpe<l. or twisted. it must be trued up. By sighting along the horizontal beams and tightening or loosening the necessary wire any cUr\'alure may be easily corrected. The second method of trussing is considerably harder to true up than the· first, since when one diagonal of a rectangle is tightene,1, Lhc other must be loosened. But since it makes an excec,lingly firm and rigid structure, it may lie well recommended to those who care to undergo the addc,l expense and labor involved by the extra turnbuckles and wires.

.r~l ~,.,,o o) ~ l.i=j ~---· -3.!L---~~

HEAO

!!POK£

,HIPPLE

FIG. 25.-Bicycle spoke turnbuckle.

similar hole bored in its centre. The ends of this strap are rounded and bored so that the piano "·ire may be passed through. The turnbuckle is then assembled and connected as shown in the illustration. The tension of the wire is regulated by turning the spoke nipple while the spoke itself is held rigid. The second method of bracing illustrated in Fig. 22 requires that a turnbuckle be included in the diagonals of every rectangle, except those

To take the glider apart, first remove the bolts holding the rudder beams in the sockets on the machine. Then unfasten the wires which bra~c the rudder to the machine by loosening the turnbuckles until the spokes and nipples unscrew aml come a·part. The rudLlcr may 11011· Le rcmo1·cd from the machine. Next take off all the nuts on the eye bolts in the lower plane arnl pull the cyel>olts out of the sockets. The two planes will thL·n come apart. Remove the stanchions l>r pulling them 1!l!t of the sockets. The two plan0s arc then lai,l one 011 top of the other an<! will •>ccupy n:ry little ruom.

CHAPTER IV. GLIDING.

The first words which may well be said upon this subject are to emphasize caution. But by this I do not wish to imply that gliding is exceedingly dangerous. Neither do I by caution mean timidity but rather judgment and common sense. Canoeing is generally considered a safe sport, but who would think of canoeing on the ocean in a storm. It is exactly the same extreme to glide from a very high object, or experiment in a high wind. The atmosphere near the earth is a mass of whirling <,1.nd swirling currents which are constantly rising and falling and become very pronounced in a high wind. Even in a comparative calm these- eddy currents exist but of course not to a dangerous degree. Evidence of this may be seen by watching the little dust particles floating in the air and made visible by a sunbeam coming through the window of a quiet room. Although the sense of feeling cannot detect the smallest air current, these little particles are whirling around and constantly changing their direction. When the wind strikes some natural object 44

B!-PLA:s!C GLIDER

such as a tree or a stone, the streams of air divide, part of them passing to the sides and part going over the top. The air begins to divide some ,l_istance before it reaches the object and the result is a rising current on one side and a falling eta-rent on the other. These currents are the bugbears of aviators for when one end of their machine passes into such a current that end rises or falls depending whether or not the current is risi11g or falling.

.,,

...........

----:-··""' ..

.,-

,.,

B!-PLA~ll GLIDllR

height where he may look down on the water. In some places the water is covered with smooth

glassy streaks which run in various directions. These smooth streaks arc evidence of rising currents of air at those places. The rough spots which suddenly sprea4 out and run across th-0 water are caused by descending currents. Therefore it is not good judgment to attempt gliding over ground broken by trees or Qther natural objects or when the wind is blowin~ over 1:3--1.5 miles per hour.

---------·

.. ------- -------

.... ,--

·Hi

..... -

- ------o:,

Fm. 26.-Top view showing how streams of air tlivid~.

QROUHO

Fm. 27.-Showing how air i:,urrents pass over objects.

0.ther rising and falling currents are caused bv the sun passing behind clouds. Portions of th~ atmo~phere are thus chilled and commence to fall while others upon which the sun is reappearing are heated and rise. Balloonists constantly er,counter these changes in temperature and the gas in the bag expands or contracts so rapidly that it often requires a skillful pilot to prevent disaster. These rising and falling currents caused by changes of temperature may be clearly seen on the surface· of a lake if the observer is stationed at a

Do not under any consideration jump off from a height which rises prominently from surrounding objects. Otto Lilienthal, the brilliant German investigator and engineer who made over two thousand gliding flights specifically warned experimenters against starting glides from prei.ipitous cliffs or huildings. There are two excellent. reasons for this. First, because when jumping from such an elevation, a gust of wind re!;)ourtds from the· sides and strikes the machine

Bl-PLANE GLIDER

so that it requires great skill to counteract its influence. Second, because, the operator and machine are suddenly suspended high in the air. VELOCITY AND FoRcE OP

Miles per

I Feet

per

Wrno.

Pressure per square

~~~ minut~l--foot 1 2

88 176

.00.3

3 4 5 6 8 10 15 20 25 30 35 40 45 60 80 100

264 352 440 528 704 880 1320 1760 2200 2640 3080 3520 3960 5280 7040 8800

.045 .08

u·> }

.125} . 18 .32 .5 1.;tl5

2. 3.125 4.5 6.125 8. 10 .125 18. 32. 50.

Description Barely observable. Just perceptible. Light breeze . Gentle, pleasant wind . Fresh breeze. -Brisk blow. Stiff breeze. Very brisk. High wind. .High ,~ind. Very high wind. Gale. Great storm. Hurricane. Tornado.·

(JJ

Be satisfied at first by running against the wind on level ground and making short jumps; After 'some practice,· operations. may be transferred to

BJ•PLANE GLIDER

lH·PLA:,;E GLIDER

4!1

a gentle slope· and the length of the glides con- force exerted against the aeroplane causing it to siderably increased. If the experimenter thus rise. A sky-rocket is caused to ascend by the reaction proceeds slowly without impatience, there is no danger in gliding. It is said that the Wright of gases formed by burning powrlcr esca!Jing brothers never so much as turned an ankle in the downwards through a small hole. The aeroplane, hundreds of flights they made, before building a by means pf its curvature directs the air downwards and so rises itself. power driven machine. The planes pass so rapidly on to new anrl Action of an Aeroplane. - Before starting to undisturbed bodies of air, and stay over one hocly glide it is perhaps well to understand how the ma- for so brief an instant, that there is no time to completely overcome the· in·crtia of the air ancl DIRECTION IN WHICH force it downwards. This may lie likened to a .l.tROPlANE 18 MOVINQ skater moving swiftly over very thin ice which i-...----------- -~------would not bear his weight were he stan,lin'g still, but since he is moving so rapidly, that any one portion of the ice <locs nut have time to bend tu the breaking point, is supported. H0Rlt0'1TAL LINE

FIG. 28.-Action of aeroplane.

chine opl;lrates and supports its passenger. The illustration shows the cross section of an aeroplane moving forward through the air in the direction indicated by the arrow. The front edge of the aeroplane is elevated so that the surfaces form an 11.ngle with the horizontal. The front edge enters practically still air and causes it to follow the curve of the planes and leave at the rear in a downward direction. Since the action and reaction of two fore~ are always equal and opposite, there· is a

Equilibrium. A gli<lcr will remain in pcrfcd equilibrium only so long as the centre of gra,·ity of the machine ancl operator fall in the same vertical line as the pressure exertc,l 1,y the «ir. Ii th\! former is forward of lhc latter, the 111:.1<:hine \\"ill incline forward and ll':t\'el ,lownwar<ls. l i the centre oi gravity is to lhe rt•ar of the ccntrv oi upward thrust excrtecl by the air, I he h,·a, 1 ,,f the machine will rise, while it' it is tu cith<"r the rig;ht or ldt side, the machine ·.,·ill lean or turn 11wr respectively to the right or Ii-(:. The centre of pressure nn tl1c, !'lane is snm,'\\"hat in advance of the actual ,linwnsional C<'lltrc of

·.~,_

Bl-PLANE GLIDER

the plane. This is due to the curvature of the plane i:md also to the disturbing action upon the air of the front edge. To make a glide, carry the machine to the top of a slope. Have two assistants hold the ends of the lower plane. Get in underneath and stand up between the arm pieces. Grasp the front horizontal beam of the lower plane and lift the machine until the arm sticks are snugly under the arm pits as in the illustration. If necessary have the two assistants prepared to run a short distance with the machine, but as soon as you are in motion you will be relieved of all weight and surprised at the lift exerte.d. After gtitting the machine snugly up under the arm pits, face the wind, elevate the front of the m.i.chine slightly, run a short· distance and leap into the air: If you are in. the right position you will sail to the foot of the slope in free flight. To lancl, push yourself towards the back of the machine, so that the glider tips upward slightly in front. It will then rise slightly but loose its momentum and slowly settle so that you drop gently on your feet.

Balancing is accomplished in flight by moving the legs and body towards that side which is highest. Shifting the centre of gravity by swinging, the ! legs forward or moving the body in the same •

nl·PLASE GLIDER

direction, will naturally cause the centre of gravity to assume a forward position, and being a force exerted downwards, tile machine will dip and descend. A reverse movement of the centre of gravity will cause the front of the machine to tip up and ascend. But if the upward slant is contin uc<l too long the glider will loose its forward velocity and settle. The tendency is always to place the weight of the body too far to the rear. ~Her a little experience the experimenter will learn how to dip his machine to acquire velocity for a rise and to otherwise handle it. Fig. 29 illustrates two lines of flight in their successive stages. At 1 the operator is running along the top of the hill and the dotted line from 1 to 2 represents his course immedjately after leaving the ground. In case the weight is back slightly too far and is not shifted much during the glide, the machine will follow the· upper line indicated by 3, 4, 5 and land at 6. If instead, at 2, the body is moved forwarq, the machine will travel down as shown. by 7 and approach the earth. Having attained considerable velocity at S,. the operator moves back and the machine rises, travels upwards as at 9 and then settles about at the point 6. This latter line of flight is to be preferred since the machine does not rise quite so high in the·air and moreover has more velocity: so that the operator may rise if necessary. · If during a flight a gust of wind strikes the ma-

....,

BJ-PLANF, GLIDER

twenty six feet long. When the machine is moved rapidly forward, the action and reaction of the still air on the lower side of the moving surfaces, REMARKS, lifts the aeroplane from the ground and supports In a little booklet such as this it is even im-'" it in the air. The curvature of the planes is that possible to cover the subject of gliding flight fully segment of a parabola, whose depth is one ninth much less power driven aeroulanes, but a short its 1ength. They are spaced one vertically above description of such a machine built by the author, . the other and about four and one half feet apart assisted by Mr. Harold Dodd and Mr. Safforrl in the middle. The ends converge slightly to make Adams will no doubt interest many since it has the machine less. affected by cross gusts. The been used successfully as a glider in towe,l flights. longitudinal curvature 9£ the planes is maintained The machine was attached to an automobile by spruce ribs half an inch square and spaced nine by means of a long piano wire bridle. It rises at inches apart. Their front ends are ingeniously a speed of between 15 and 20 miles per hour a111l fastened in brass sockets on the front horizontal remains in the air as long as the auto keeps moving members and their rear ends project about a foot at this rate. The gr~unds used by the author in over the rear horizontal pieces. The. fabric a his experimcr1ts limited the flights to about 800 feet. close woven muslin is put on over the top an,! The automobile in one flight traveled about bottom of the ribs and. is fastened hy grommets 50 miles per hour, but the machine soared on a to a wire running through the rear c111ls of the perfectly even keel and without any pitching. ribs, and by strips of felt fastcne,l ,!own to the Just as the author was about to descend, the towing ribs with upholsterer's tacks. wire broke, but the aeroplane glided so gently tn "The stanchions arc six feet apart except the the ground that it was impossible to tell w,herc middle two, which arc only eighteen inches apart. it first touched. The horizontal picc<.!S of each surface arc parallel The following description of the machine is an anrl four foet distant from each other. All are of extract from an article written by ::'>Ir. R. S. Br0\n1. selected spruce, shaped so as to give the greatest "The two supporting surfaces of the :wroplanc strength with the least resistance to the air, and are five feet wide in the direction of flight aml the least weight. All the many rectangles of the 55 structure are brace<! diagonally with steel piano wire. In every one a small turnbuckle is inserted to aJjust the length. The nuclei of these tumCHAPTER V.

BI-PLANE GLIDER

chine from the front, it will accelerat_e i~s vertical motion in regard to the earth. 1:hat ,_s, if the m~chine is already rising it will nse higher an~ if descending will fall more quickly. A ~ust of wmd from the rear will cause the machm? to drop suddenly and so always glide into tlw wmd.

lll•PLA~E GLIDER

buckles consists of bicycle spokes. By this wiring a perfectly rigid truss is formed. "Ten feet to the rear of the main body, there is a horizontal tail, which halves a vertical rudder of about the same area. This vertical surfa<;e is movable and turns the aeroplane to the right and left when moved by rotation of the steering wheel. As can be seen in "the accompanying illustration these rudders are strongly supported from the principal structure. " At an equal distance in front of the supporting planes is the elevation rudder. This consists of two horizontal plane surfaces, six feet by two. These turn about a horizontal axis transverse to the direction of flight. Thus 'the angle which they present to the wind can be altered at the will of the operator. This is accomplished by pushing and pulling.on the steering wheel. Through the middle of the horizontal surface runs a triangular ~ertical plane. This is designed to prevent the turning of the machine by a gust striking the rear vertical rudder, for if it strikes both vertical surfaces, one in front a11d one behind, the two neutralize each other and no turning takes place. " On the ground the machine runs on three twenty-inch pneumatic tired wheels. .These were especially made for the purpose, with seamless rims and heavy motorcycle tpokes. Two are set in regular forks of tubing under the rear edge of the lower plane, while the third wheel is con-

DI·PLA!'.g GL!DllR

siderably in advance of the body proper. When running on the grnund pri.!paratory to rising, tlw machine is carried on these little wheels. " The operatorn seat is in front of the supporting lll·PLANE GLIDER planes, and as the photograph shows is carrie,1 60 on two braces from the front wlwel. Sitting in installed, will be supported between the ·two main the seat, th~ aviator can clirect the aeroplane from planes and connected to a laminated spruce si<;le to side by turning the steering wheel before propeller, siic feet in diameter." him. This steering wheel is mountccl on a post Those who of until late have not been associated hinged at the bottom, and by pushing- or pulling with aeronautics cart scare;ely realize the steps by on the wheel the aviator is enabled to control his which aviation had progressed and the trend height above ground by ineans of the elevation towards building machin~s. rudder which is connected by a wooden rod to the The aeroplane ;orker can no longer be classified steering post. with the seeker after perpetual motion. It is " 1vlid-way between the two main surfaces and therefore to be lamented that so many of these at the front of each end is a small plane. These arc ~achines partake of freak construction. Originality tilted at positive and negative angles to the wind, by means of cords connecting them with a pivoted 1s always to be fostered but must bear some degree bar moved by the pilots ·feet. In flight, if one' of proportion. Only a very few favored people in comparison c .1d rises, the a via tor presses down the end of the . to the rest of civilization have been enabled to see bar on the rising side. -This causes the ' balancincr an aeroplane in flight. Many times less are those plane ' on the high side, .which is the name give~ who have had the privilege of examining a successto the movable planes just described, to form a ful machine. negative angle with the wind so that the hi"'h side is forced down. The other balancing plane a~sumes an equal positive angle, so as to force up the lower side. Thus the machine is again brought to an even keel. After a little experience, this action becomes almost automatic, so that no difficulty . is experienced in keeping the flyer level. "The motor, which at present has not been