This extract is from the Sailplane and Gliding Magazine 1932
CLUB CONSTRUCTED MACHINES
THE FINISHING TOUCHES
It is quite safe to say that the a d ding of the finishing touch es to a club-built machine is as important, if not more important than any other part of the building of the machine.
A machine, when once finished, must be made and protected in such a way that it can withstand the hardest of handling and the worst of bad weather. Hence in many cases, the "finishing touches" of a machine must of necessity be done before the machine even begins to take shape. This applies especially to the metal parts. All metal parts should be thoroughly protected from the effects of weather. As soon as they are finished, and before they are mounted on the machine, they should be covered with a good coat of protective lead paint. This is one of the easiest and cheapest ways, and in the long run, the best method.
All bolts which are used for mounting such metal parts on wooden parts of the machine should be greased, ancl when fixed should be given a good coat of the same protective paint.
The main spars of the maehine should also be protected before the machine is covered. By far the best way of doing this is to give them a coat of ordinary size, followed by a coat of varnish. This applies especially to the aileron spars and tail plane spars. It is desirable that the inside of the cockpit should be flnished in a similar manner.
The covering of the wings, comes under the heading of "finishing touches." So far as is known to the writer, there is only one really; satisfactory method of covering sailplanes, which overcome all difficulties and, when done forms a lasting job.
The fabric which is usually used is light, and must be handled with care. It should be glued on to the rlbs and spars with cold water glue. No stitching should be done. Tape is unnecessary except on the underside of the wing.
A point here is worth considering. It will be found in every machine of continental design, that the leading edge three-ply is taken from the top of the front spar, round the nose of the wing and is attached to the bottom edge of the front spar. This is done, first to add to the strength of the spar and also to help in the covering of the machine. The fabric should be first glued to the top side of the front spar and allowed to dry.
Next the fabric should be stretched back and glued to the trailing edge, which should be of wooden construction. As the upper surface of the wing is convex, glue should be worked through the fabric on to the ribs from above. This method gives a far finer job, than first gluing the ribs and then stretching the fabric back to the trailing edge.
The underside of the wing, however, presents fresh difficulties, as it is generally concave in outline. Here the ribs must of necessity be glued first, and the fabric stretched back and glued to the underside of the front spar. If the fabric has been stretched in a proper way, it ought to be standing clear of the ribs.
In order to get this fabric glued down to the concave ribs, strips of thin three-ply, 3/4 inch wide should be cut, and should be given a coat of beeswax, or clear furniture polish. These strips should then be very lightly pinned down to the ribs, the fabric being brought down on to the glue on the ribs evenly along the whole length of the rib.
'When the glue is dry, the three-ply strips can be pulled off, leaving the fabric firmly glued to the ribs. The beeswax, prevents the strips from becoming attached to the fabric.
The writer can vouch for this method as that generally followed, and as one which gives absolute satisfaction.
When the machine is completely covered, it ought to be rigged, ready for the finishing coa ts of dope and varnish. Two coats of clear dope are sufficient for the light tabric generally used.
When these are dry, the whole machine should be given a good coat of size, incl uding the wings, fuselage, and in fact, every external part of the machine. The size will dry in 30 minutes. and then the first coat of clear varnish should be applied.
Clubs are advised to obtain the very best carriage varnish they can find, and to apply the firs coat with a brush to ensure evenness. This coat should be allowed to dry and harden.
If a super fine finish is desired, and it is it well! worth while, another coat of the same varnish applied with a spray will give a really marvelous polished effect.
The result will be a machine with a fine glossy surface, in natural colours. which, in the writer's view is by far the best looking finish that can be obtained.