THE AMATEUR AIRCRAFT CONSTRUCTORS GUTDE

ByArthurW. J. G. Ord-Hume - Part 4

Workshop Requirem ents-C ontinue d

Before the amateur undertakes the construction of an aeroplane there are two factors which he must consider. The flrst is where to build it and the second is what tools will he require for the task.

Dealing firstly with the question of a workshop, the average constructor will have to make do with a garage or perhaps a large spare room. It should be remembered that quite a large proportion of the work involved will be detail work and the manufacture of small parts for assembly and that in the early stages, at any rate, only a small space is needed.

However, once the constructor is at a stage where a fuselage or wing has to be assembled and finished, it is obvious that more space willbe needed.

For the Turbulent, a space is required at least twenty-flve feet long and eight feet wide as the wing is built in one piece. The fuselage, of course, may be constructed in a somewhat smaller space.

The ultraJight with a two-piece wing may be readily constructed in an ordinary garage.

The workshop will require a good sturdy bench for woodwork and metalwork. At least two trestles will be needed to support structures during assembly. It is recommended that trestles should be used rather than boxes since they are stouter and can easily be levelled and aligned.

For woodwork and gluing, the temperature and humidity of the workroom should be reasonably constant. This means that adequate ventilation must be provided without draught. Furthermore, freedom from damp must be ensured.

In the case of a garuge with a concrete floor, any gaps at the bottom of the doors can be sealed with strips of felt.

To keep the workroom at a reasonable temperature during winter, it is worthwhile investing in a 'black heat' electric space heater. This unit, mounted near the floor, will circulate warm air throughout the room for the consumption of very little current.

Whilst on the subject of electricity, it is important that any electrical installations in the workroom should be properly earthed. This is particularly so in a garage with a concrete floor. Should power be required for operating an electric drill or spray plant, make sure that there is a 15 amp. power point at hand. Under no circumstances should equipment be run from an electric light socket. Even lead lamps should be earthed through a three-pin power plug. If there is any doubt concerning the electrical wiring, consult the local electricity authorities who will send, free of charge, an inspector to check and give advice.

If a spare room is to be used for aircraft construction, take the precaution of checking to see that the completed components may be removed from the room either by window or door. This may sound elementary, but the author once saw a partially-completed ultra-light aircraft broken up as there was no means of removing it from the room in which it was built! Finally, the workroom should be well lit. In addition to adequate fixed lighting, a lead lamp is an advantage when one has to tackle a job in an out-of-the-way corner of a fuselage.

Tools for the job

It is not easy to list just what tools are required for the construction of an aircraft. Whilst an enthusiast may proceed with only a small selection of tools, it is desirable to have a reasonably larger selection with which to work. The right tool for the job means an easier approach to the job-and that means a quicker, better result.

You can file away the bars of a prison window -but a decent hacksaw with the right blade makes it a lot quicker !

It is therefore intended to set out a list of tools which will suffice to do the job. All the undermentioned items are relatively cheap and are obtainable from all good tool stores.

Centre punch; cold chisel; small pin punch; large pin punch; scriber; pair of engineers' dividers; 12" steel rule, graduated in fractions and decimal inches; 50 centimetre rule (as alternative to above); straightedge, at least two feet long; medium sized ratchet screwdriver; 'Watchmaker's' long-shafted screwdriver; 4 oz. hammer (cross pane); I lb. hammer (ball pane); pair tin snips; pair long-nosed pliers; pair side-cutters; woodwork chisels f;" and 1|" wide; l]" smoothing plane ('Record' or 'Stanley'); spokeshave; six 6" clamps; selection of files (coarse, medium, fine and needle); tenon saw; hacksaw and selection of blades (18,24 and 32 teeth per inch); hand brace and set of drills; carborundum stone (for sharpening plane iron); assorted taps, dies, reamers and spanners (B.A. and B.S.F.); vice, 3" jaws for metalwork; vice for woodwork; 12" double-ended sail needle; pair large scissors; pair pinking shears.

A recommended addition to this-and one which will soon pay for itself in time and energy saved-is an electric drill such as the Wolf Cub. To this can be added the circular saw kit which makes a splendid unit for cutting small timber.

Furthermore, a fretwork machine, although not essential, could well be utilised for such jobs as cutting out plywood for wing ribs, bulkheads and so forth.

A small paint spray plant is also an advantage, but, since it may well represent a Targe outlay, it is not essential. A local garage may well agree to loan equipment.

A small, hand-operated guillotine will save much time in cutting out metal fittings.

We will now deal with some of these tools and their uses as applied to aircraft construction.

The centre punch is used in sheet metal layout work for marking, by means of a sharp in- dentation, the centre of a hole. This indentation provides an accurate location for the point of the drill to start the hole. It is important to keep the point of the punch as sharp as possible to ensure maximum accuracy. The angle of the point may be between 60' and 90', the latter being a stronger point for use on steel.

The scriber and dividers are also used in sheet metal layout. The scriber is a conyenientlyshaped piece of hard wire with one end ground to a sharp point. Used rather like a pencil in conjunction with a rule, guide lines may be made on metal for cutting and so forth.

The dividers are used for describing arcs on metal as, for instance, the radius of the end of a fitting.

The cold chisel may be used for roughly cutting out a metal fitting. For general purposes the chisel is ground to a cutting angle of between 60' and 70'. The harder the material to be cut, the greater the angle and vice versa. The chisel should be as sharp as possible without being so sharp that the cutting edge dents in use.

The cold chisel cuts metal by means of shearing. The material should be clamped in an upright position in a vice so that the surplus material, i.e., the portion to be removed, protrudes. The chisel is held so that the lower angle of the cutting edge is parallel to the vice jaws. In this way, the chisel and the vice jaws act together as a shear producing a clean cut. To facilitate this action still further, the chisel should be held at an angle to the material so that a slicing cut results.

If the head of the chisel is held too low, the shearing action is lost and the material is bent or torn off. If the head of the chisel is held too high, the chisel will cut into the vice.

Pin punches are used for peening over the ends of bolts which have to be secured in this manner. By driving the end threads of a bolt down to the nut, the nut is effectively prevented from working loose. To do this, a heavy block is held in contact with the head of the bolt, the punch located on the end of the bolt. The punch is then struck several sharp blows with a hammer. The head of the bolt must be supported with a block during this operation, otherwise the structure surrounding the bolt may be damaged'

The rule is a precision device used for measuring the distance between two points either in inches or millimetres. The rule is not a screwdriver, paintscraper or general purpose prodder' It should be kept specifically for the use for which it was intended.

Similarly, the straightedge should only be used as a straightedge. These two last mentioned tools are among the most misused in the workshop and cannot be expected to give accurate results if they are not treated properly'

An essential tool to the carpenter and aircraft constructor is the smoothing plane' For aircraft use, a good l$" ot 2" Stanley or Record brand with adjustable blade is recommended' This will cost about two pounds. To go with this, the constructor will also need a carborundum sharpening stone (a special flat stone is available with two grades for grinding and honing plane irons or blades) and a device for ensuring the correct honing angle for the blade'

To sharpen a plane iron, remove the blade from the plane by slackening off the spring wedge and undoing the large screw attaching the back iron to the blade itself. Using the honing angle device, the blade may then be honed on the "u.borrrrdum stone. Lubricate the stone with plenty of oil to prevent its clogging' If the blade is chipped or badly worn, it will be necessary to regrind the blade. The honing angle device can also be used for this purpose in conjunction with the coarser of the two sides of the stone' After regrinding, reset the honing angle device (the correct angle of the cutting edge of the blade is 40") and hone the blade on the smoother side of the stone. After this process, the blade should be stropped to remove burrs on the cutting edge'

In reassembling the blade to the back iron, care should be exercised to see that the blade protrudes not more than about ll32 of an inch from the tip of the back iron.

In use, avoid planing coarse wood or timber with knots in it-the blade will become blunt and chipped quickly if you do so. Keep your plane for aircraft woods. Always make sure that the blade is sharp. After use, either retract the blade by means of the thumb-screw or lay it on its side. Never lay the plane flat down for fear of damaging the blade. In all cases, before putting the plane away with other tools, retract the blade.

Never attempt to remove surplus glue squeezed out of a joint with a plane. Dry glue is very hard and should either be filed off with a rasp or preferably wiped off with a clean cloth whilst still wet.

To get the best out of a plane, never try to remove too much wood at one go. It is better to skim it off thinly with several strokes. Failure to do this will clog the plane, tear the grain of the wood and expend a good deal of energy on the part of the oPerator.

When scarfing up plywood in particular, it is important to remove the thinnest possible layer of wood at a time. This will give a good, clean sharp edge to the ply.

With a plane, you can always take more wood off: you cannot replace it if you have removed too much.

The spokeshave is virtually a smoothing plane made for planing curved surfaces. It is held firmly with both hands and drawn across the wood towards one at an angle of about ten degrees. This produces a slicing action, thereby giving a cleaner cut.

As with the smoothing plane, the spokeshave has a blade which is adjustable and may be set in any desired position. Do not use the spokeshave where an ordinary plane will do the job.

For clamping up glued joints, the constructor willfind the'G'clamp an invaluable accessory of which he cannot have enough. 'G' clamps are made in various sizes from one inch to eighteen inches in capacity. The sizes most used will be 4", 6" and 8". Clamps are rather expensive and, as a general rule, six 6" clamps should suffice.

In use, the jaws of the clamp should be prevented from making contact with the bare wood by means of pieces of scrap wood. It is possible to apply great pressure with a clamp and this will cause the wood fibres to be compressed and damaged if scrap wood clamping pads are not provided. For most purposes, it is only necessary to tighten the clamps lightly to apply the correct pressure for glue setting. Overtightening the clamps on a glued joint may well damage the wood and squeeze too much glue out of the glue-line.

The file is used primarily for metalwork, but it may be used with equal success on hard rubber, fibre, wood and so forth.

The most common files and those which are necessary for the amateur to possess are the flat, half-round, round, rat-tail and needle.

These flles are manufactured in various types of cut. The cut refers to the kind of teeth on the flle. The majority of files are double cut, having two sets of chisel shaped grooves opposed to each other diagonally across the faces. Single cut flles are used mainly on wood or soft metals.

Double cut flles are provided in three types of cut: the bastard or rough, the second cut, and the smooth cut. The flat file is available with one edge devoid of teeth. This is termed the 'safe'edge which may be faced against the portion of the job which is not to be filed.

The file should always be used with a handle as, if the file should slip in use, the tang may well injure the palm of the hand. All files have teeth which point forward. This means that the file only cuts on the forward stroke. On the return stroke the flle should be raised to prevent blunting the teeth. However, when flling soft metal such as aluminium, thp file may be drawn back in contact with the metal as this will help to unclog any metal caught in the teeth.

As the blade of a file is hardened, it is very brittle. A file should never be thrown about, hammered, used as a lever or used as a hammer.

File with a steady, even stroke using as much of the length of the blade as possible. Maintain enough pressure to keep the file engaged in the cut to avoid damaging the teeth by slipping, clamp the material being filed tightly in the vice to avoid the material vibrating or the file teeth chattering in use.

To clean the teeth of a flle which have become clogged, use a file scratch card and brush in the direction of one set of teeth at a time. To prevent the teeth clogging when filing soft metal, rub chalk into the teeth.

When using a smooth file to finish a job, chalk in the teeth will produce a polished finish without scratches.

The hacksaw is used for sawing metal, fibre, wood and many other materials. It differs from the ordinary saw in that it has a replaceable blade held in an open frame. The teeth on the blade are smaller and are set somewhat differently to those on an ordinary saw.

To get the best results out of a hacksaw, care should be taken to select the right sort of blade for the material to be cut. Generally speaking, coarse teeth cut faster but are more easily broken than flner teeth. In selecting the right blade for the job it should be remembered that at least two teeth should be in contact with the iob at any time. The more teeth in contact means less chip clearance and quicker clogging.

In assembling the blade to the frame, any one of four positions relative to the frame may be selected, since the blade is attached to a square shaft set in each end of the frame. For example, if it is desired to cut a two inch wide strip off a long sheet of metal, the blade may be fltted in the frame so that, with the frame horizontal, the blade edge is vertical thereby permitting the cut to be made without the frame fouling the material.

In all cases the blade should be assembled with the teeth pointing forwards. Tighten the blade flrmly in the frame to lessen the risk of breakage. In sawing, pressure should be applied on the forward stroke and the saw raised slightly on the return to avoid rounding the teeth.

Where space permits, use the whole length of the blade at about sixty strokes per minute.

If it is desired to make a wide cut in a piece of metal, it is possible to fit two blades into the saw at once.

The tools of fabric work and their uses will be dealt with in detail in a later article on aircraft finishing.

Engineering Drawings and their Interpretation

The engineering drawing, commonly referred to as a drawing or blueprint, is prepared by the designer to convey instructions and information to enable the constructor to make or assemble the detail concerned with speed and accuracy.

The drawing will show all pertinent dimensions clearly, thus eliminating the need for any calculation on the part of the constructor. It will also state the speciflcation, gauge or size of the material to be used, the type of flnish (..9., flle, machine, grind), the number required per assembly (e.g., six per aircraft) and the protective treatment to be applied to the completed part (varnish, paint, plate or anodise).

Therefore it can be seen that the drawing fulfils several purposes, each one assuring that the parts to which it refers may be produced exactly as the designer intended.

The illustration of a part on the drawing may notnecessari1ybefu11-size.Particu1ar1ywith large parts it is neither convenient nor practical for them to be drawn full size. It is often more convenient to make the drawing smaller by a stated ratio. For example, the part may be depicted one quarter or one half full size. This proportion of reduction is referred to as the 'scale' which is always indicated on the drawing.

If the part is drawn full size, the drawing states 'Scale:Full Size' or sometimes'Scale 1:1'. Similarly half size illustrations are sometimes i written 'Scale l:2' and so on. The scale of a I drawing is usually to be found in the title block, I that is the bottom right-hand corner, or prominently displayed elsewhere on the sheet.

Concerning the actual drawing, various types of lines are used for certain purposes.

The outline of a part, provided that it is visible to the observer in that view, is represented by a continuous solid line. Any part or recess not normally visible to the observer from the angle in question is indicated by a line of thin, short dashes. The centre line or datum line of a part is shown as a fine line or alternate long and short dashes with both its ends clearly extending beyond the object. This is further identifled sometimes by the symbol CIL or bears the selfexplanatory inscription 'Datum' and is the line from which layout dimensions are made. A continuous thin line is used for projection or dimensioning lines.

The draughtsman can illustrate a component in one or more of several manners.

For general work, the First Angle projection or orthographic projection is used which is arranged so that each view represents the far side of the adjacent view. This method consists normally of three views-the front elevation, plan and side elevation-to which may be added additional views such as base plan, rear elevation and opposite side elevation if they differ from the normal views given. The orthographic projection allows the clear and accurate representation of dimensions.

The Third Angle projection is a variant of the First Angle projection. This, too, is an orthographic projection but it is arranged so that each view depicts the near side of the adjacent view.

The drawing will not show an additional view unless it is essential to assist in its comprehension. If the detail consists of a complicated piece, an auxiliary view may be justified. This is a view looking on a portion at an angle other than ninety degrees. The angle of the view is generally indicated by an arrow or is drawn directly on the centre line of the portion concerned as shown in the normal orthographic view.

It is often desirable to show the section of a part. This is achieved by hatching at 45' to the edge of the drawing. Adjacent parts in section are defined by hatching at right angles to the main portion of the section.

A symmetrical object may be illustrated in both elevation and section by drawing one half as the outside view and the other in section about the centre line. An object may be sectioned at any convenient place to show detail which would otherwise be hidden. In this case, one portion of the detail may be shown as a section, or the section superimposed on the elevation.

Sometimes it is desirable to show a part pictorially by use of the Isometric projection method. In this straight lines are either at 30" or 90" to the horizontal. It should be noted that the isometric view illustrates 'the object in question without perspective.

Popular Flying, JulylAugust, 1957

There are basically three types of drawingdetail, assembly and general arrangement drawings. A detail drawing will show one separate part of a unit, for example, the rib construction for a wing. The assembly drawing will show the entire wing with the ribs and other details shown with their relative dimensions. The general arrangement drawing might show the entire aircraft in three or four views (as an orthographic projection) or might show the layout of a service or installation such as pitot lines in the wing.

Certain abbreviations are used on drawings. Below are listed those which are most likely to be met with by the constructor.

Annealedann. Diameterdia. or d Approved - appd. Materialmtl.

Centre lineCIL Not to scaleN.T.S. Chamfer -Chamf. Radius -Rad. or R. Countersunkcsk. Machine or grindf. Cylinder - cyl. Specificationspec.

The designer may call for two parts to be made from the information on the drawing, one left hand and one right hand, where the difference lies in the bending up of a flange or some similar detail such as the angle of a bend. He will therefore call for one pair'handed'indicating one left and one right hand piece.

Dimensions in inches are shown either as fractions of an inch or decimal inches as, for example, Lf," or 1.75". It is usual to take the smallest unit of measurement (one inch or one millimetre) and use it for all dimensions on the drawing. For example, a dimension might be 129 inches or 1,493 millimetres rather than the division of feet and inches or metres, centimetres and millimetres. It is practice to omit the 'inches' or 'millimetres' symbols from drawings where the same terms of reference are used throughout. Therefore we have 129 or 1,492. Reference to the title block will state what terms of referenbe are used on the sheet-inches or millimetres.

When a radius is shown, the dimension is written'R-+' or']R'where an inch is the term or reference. The same applies to the diameter of a circle which might be written as either 'D-105' or '105D' where the millimetre is the term of reference. Diameters are also sometimes referred to by the symbol 95 which is used with similar notation.

There are two systems of production of a drawing. In both types the design draughtsman produces the original master drawing, usually in waterproof Indian ink, on either tracing paper or varnished tracing ctoth. This master may now be used to produce either blue-prints or dye-line prints. With the former the paper surface is entirely blue and the drawing appears in white or colourless lines, The blueprint is possibly the easiest type of drawing to read-the information contained on it is clearly visible even when the sheet is oily or dirty. However, exposure to direct sunlight or to water will cause the blue to fade, thereby making it difficult and eventually impossible to read.

The dye-line method of reproduction results in a white sheet upon which the information appears either in black or grey-brown. It is widely used in the aircraft industry in place of the blueprint.

In both cases, part of the technique of the printing of drawings from the master involves the washing of the print in water. Since paper expands and contracts with heat and moisture, the drawing may only be used as an illustrated list of relevant data for the making of a part. On no account should measurements be taken directly off the sheet. Relevant dimensions will be written on it, thus eliminating the need for this.

Bearing in mind that paper is a poor medium for accurate drawing, the designer will often produce a drawing on a large sheet of metal or plywood. This is particularly the case in the aircraft industry as a drawing on metal may readily be cut out and used as pattern, template or part of a jig. These drawings on metal are often used to show the relative position of details in a section of an aircraft. For example, the outer skin of a bulkhead will be shown together with the inner skin and various internal members. One rnight describe these drawings as X-ray pictures of the portion in question. They are known as loft-layouts or loftings and are used in conjunction with detail and assembly drawings. They are reproduced photographically from a master tracing on to sensitised alloy sheets which are then developed.

With a little forethought and practice, the constructor should be able to interpret any drawing if he bears the foregoing points in mind.

by Christopher Dearden PARTlOF3PARTS

Comeafill the cup, and in the flre of Spring The Winter garment of repentance fling: The bird of time has but a little way To fly-and 1o ! The bird is on the wing.

OMAR

I(HAYYAM.