Covering a Lightplane Fuselage

Covering A Lightplane Fuselage By Bob Whittier, EAA 1235 P. O. Box 543, South Duxbury, Mass. HIS ARTICLE will seem to cover details which are would be to choose a piece 20 ft. long and perhaps 48 T "old hat" to the experienced aircraft mechanic and in. wide. You would measure about 1 ft. inward from amateur aircraft builder. It has been written as a result one end, and the same amount inward from the diagon- of a growing number of requests from newcomers to our ally opposite end, and make an almost-diagonal cut to get sport and magazine for fundamental how-to-do-it infor- the two side pieces. Or one piece of cloth 36 in. wide mation on aircraft fabric work. So it is hoped that the might give enough cloth to cover one side and the bot- old-timers will indulge us this attempt to be of assistance tom. to the many enthusiastic newcomers! If one is uncertain, it is possible to use lengths of The subject in the photographs is the fuselage of a brown wrapping paper of appropriate width to make pat- 1935 model E-2 Cub, rebuilt by the author a short time terns, or to make miniature patterns to scale from the ago. Therefore the procedure to be described is applic- blueprints or model, and juggle them around on rec- able to aircraft in both the antique and amateur-built tangles drawn to scale and representing contemplated fab- classes. In the job to be described, Grade A cotton air- ric lengths and widths, to find the most economical size. craft fabric was used and the information given is primari- But it must be remembered that some waste is in- ly applicable to that type of covering. Other fabrics used on evitable. Don't try to economize to the point where no small aircraft include Irish linen, Ceconite, fiberglass margin for error and working is left. Usually about 2 in. and a variety of Dacron and, of course, some of the details margin is considered the minimum desirable ... it de- of working with them vary. However, the basic procedures pends on the size and curves of the area involved. Left- of fitting, cutting, attaching and doping are similar over scraps have their uses, such as for doubling patches, and the steps shown here can be of use to a person who etc. has chosen one of these fabrics. Before starting to apply fabric, the fuselage must be To start at the very beginning, it would be well to prepared. Naturally all the framework must have been explain that Grade A fabric and others are available in cleaned up and suitably primed for protection against rolls of varying width, beginning usually with 30 in. and corrosion. Make sure that nuts located underneath floor- running usually in 6 in. increments up to as much as boards, such as those which hold rudder pedals in place, 72 in. and even more. One notes what widths are handled have all been properly tightened and cottered. Gas by the firm from which one is buying materials, and de- tanks, baggage compartments and control cables must be cidas what width might be the most feasible and eco- in place and safetied. It is usual to attach wire to the nomical for the fuselage under consideration. Practically rear ends of control cables and wrap it around the tail all fuselages taper from front to tail and this must be post at some suitable point where the wire will clear the taken into consideration. fabric. Pull the cables tight enough so they won't flop Suppose a fuselage measures 28 in. in height at its (Continued on next page) forward end, from upper to lower longeron. A strip of 30 in. fabric would seem the best, for it would allow a 1 in. margin at top and bottom for sticking to the longerons; close but adequate. But if the fuselage is only 12 in. high at the tail, that means that a long triangular piece of cloth would be trimmed off from tail all the way forward to the vicinity of the cockpit. So long and narrow that it probably could not be used to very good advantage in covering a control surface, interior of cabin, landing gear vee, etc. So it is a matter of using common sense. One way to make better use of fabric would be to use a piece 30 in. wide and perhaps from 30 to 35 ft. long for a fuselage that is 20 ft. long. After one side has been cut, the piece is reversed and held onto the other side for trim- ming, the trimmed piece working out to be a very long and very narrow scrap of varying width. Another way Fig. 1 SPORT AVIATION IS COVERING A FUSELAGE . to use nitrate for initial attaching of fabric to frame. At- (Continued from page 15) taching goes easier and quicker, and may be more secure. about as the fuselage is turned over and touch the wet With bits of tape or suitable clips, affix the section fabric or become caught on structural projections. of fabric to the frame with an equal amount of margin A pair of good saw horses that won't readily slide on all sides. If there are prominent sags or wrinkles, out from under the ends of the fuselage are needed. Re- work them out — but there is no need to worry about member, the tubes usually will rest on the horses at an small ones. Brush dope copiously along 2 or 3 ft. of tub- angle due to fuselage taper. In the accompanying photos, ing, press the cloth down into place and rub firmly with a pair of strong boards was bolted to the front of the a finger to remove air bubbles and doubled spots in the fuselage by the engine mount bolts, and served as legs cloth. Then brush dope onto the outside of the cloth so when the landing gear was removed. that it is thoroughly wet. If the cockpit is to be lined with doped fabric — At all times try hard to avoid applying dope so lib- about the easiest, cheapest way of doing a good "up- erally that it dribbles down across the fabric or drips holstery" job — work is started by clipping a piece of onto it. If this happens either on the inside or outside, fabric to the outside of the fuselage as in Fig. 1. This the dope involved will dry hard long before the fabric makes it easy to cut the cloth to correct shape to fit on as a whole is doped, and form hard little buttons that will the inside of the framework. Suitable notches, perhaps show through the final coats very clearly. Such spots are a bit undersize, are cut to let the fabric clear fittings not only unsightly but because they are brittle, can cause as it is wrapped onto longerons. It can be held temporari- early failure of the fabric at those points. When applied ly in place with bits of masking tape, with C clamps, or in normal thicknesses, dope remains quite plastic and any available kind of spring clips. this is what enables the fabric-and-dope skin to give un- Often the inside of a cockpit is studded with brackets der the bumps of service. and other projections having to do with the controls. When the first strip to have been doped in place is Holes, notches and slits must be cut in the fabric as com- dry, apply dope to tubing opposite it and as before attach mon sense dictates to fit around such obstacles. Try to the fabric by doping and rubbing. Dope dries quite rapid- keep the holes as small as possible, but do not worry if ly and you can usually work right along, alternating it seems essential to make a fairly large one such as from side to side or top to bottom. However, don't rush can be seen about the throttle control support bracket things; if you go too fast and a doped section is pulled at the top left longeron in Fig. 2. All such slits and holes loose because it has not set firmly, you will have to go back. Though the fabric may not come completely off a section of tubing through premature pulling, it could move just a little and somewhat weaken the developing dope-fabric-tube bond. Before long, the inside piece we have started with is all fastened in place as in Fig. 3. In this particular Fig. 2 can be covered neatly with doped-on patches which will be unobtrusive when doping is finished. Fabric is usually sewn into a sock to fit onto the fuselage of a large or fast airplane. It is cut to approxi- Fig. 3 mate shape with top, side and bottom pieces. Aircraft supply shops sell "T-pins", large common pins with easy- to-push T-shaped metal heads. With these pins the vari- ous pieces are fastened together where seams are to be, usually but not necessarily along the longerons. The "sock" is then sewn up on a machine and pulled on from the tail. But for small, slow airplanes it is common to attach fabric by doping it directly to the longerons. If it goes about 50 percent around the longeron the dope will hold it on quite all right, and as pinked tape goes over seams anyway it further binds sections of fabric together. The best way to appreciate the bonding power of pinked tape is to pull some off of an old airplane! Butyrate dope is not as "sticky" as is nitrate dope and in cases where it is intended to finish the plane with the more durable and fire resistant butyrate, it is still common Fig.

Load more