Covering the Link Trainer ailerons

Suomeksi

The wing refurbishing of the South-Karelian Aviation Museum’s Link Trainer has moved on to the covering stage.  At first we set on to covering the ailerons. One aileron was original and the other built at the Aviation Museum Society’s Tuesday Club to replace the missing aileron. Stripped of its covering, the repaired original aileron and the rebuilt aileron were covered with a special cotton fabric for covering, bought from Switzerland at Craftlab.

The covering was commenced by setting the aileron on the covering fabric and drawing the shape of the aileron on the fabric with a felt pen. The fabric was cut with a wide margin, taking into consideration the actual space for working. The fabric was folded around the aileron, so that the lapels met at the trailing edge. The lapels were fastened together with wig pins, at the same time tightening the fabric on the aileron. T-headed and long wig pins are very handy for this purpose. The pins were acquired from a Chinese on-line shop.

After the lapels of the covering fabric had been fastened to each other with pins, we were facing with tightening the fabric with water. Water tightening is the first phase to make the covering fabric tight. In the process the warp and weft already shrink somewhat, i.e. the fabric pre-tightens around the aileron. For water tightening the water was boiled. By boiling the water it will be disinfected, so that organic impurities won’t infect the fabric, which could cause the fabric to mould. Well, in this case the boiling wouldn’t have been necessary, because we aren’t dealing here with an airworthy device. After the water had cooled down, the fabric was thoroughly soaked.

After the fabric had dried, the proper tightening was commenced. It will be done with nitrocellulose lacquer, which causes the fabric to become as tight as a drumhead. As a lacquer we used NC-Speed nitrocellulose lacquer and as thinner Ohenne 8. Red iron oxide was mixed into the tightening lacquer as a pigment. It is customary to colour the tightening lacquer, so that you can keep track of which areas have been dealt with and which haven’t.

25 % lacquer.

50 % lacquer.

The tightening coats of lacquer for the covering fabric will be applied in phases by starting with diluted lacquer and ending up with undiluted lacquer. The Link Trainer’s ailerons were applied at first with two layers of 25% lacquer, followed by two applications of 50% lacquer, one application of 75% lacquer and to finish it all an application of undiluted nitrocellulose lacquer. The lacquered surfaces were sanded between applications for the fuzz, which was stood up by the lacquer.

After the application of 50% lacquer, the fastening pins of the covering fabric were removed. At the same time the extra fabric lapels’ surplus to the trailing edge were cut off with a Stanley knife. This was possible, because the covering fabric was glued firmly enough to the trailing edge of the aileron, the ribs, and other parts of the aileron structure. The trailing edge will be sanded smooth, and a serrated cotton strip will be glued to it to strengthen it.

75 % lacquer.

In this connection it must be noted that in case of an airworthy aircraft, the covering fabric would have been sewn to the ribs of the aileron, the same way as the fabric would have been sewn to the wing ribs. In not covering the ailerons and the wings we decided to cut corners, so in this case skip sewing the fabric to the ribs. This had been the case with the damaged covering fabric we stripped off the wings.

The tightening lacquer for one aileron is ready and waiting for to be painted beige. The other aileron will receive a few more applications of lacquer, before its fabric will be as tight as a drumhead.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.