Streamlining Round Tubing By Marshall B. Standing, EAA 11383 135 Sheridan Way, Woodside, Calif.

FIGURE 1

I

HAVE USED this simple method of streamlining round tubing on the lift struts of my Stits "Skycoupe" and have experienced no problems. After priming the tubing with zinc chromate, give it a coat of polyester resin such as used in fiberglas work. It is preferable not to use "boat" resin as it contains wax which comes to the surface to prohibit oxidation of the resin while it is setting up. The wax will cause weak bonds between the various layers of resin, so use laminating resin which does not contain the wax. If you can't find laminating resin and you have to use boat resin, be sure to dissolve the surface wax with acetone or lacquer thinner before applying a second layer. Never use a finishing resin to laminate with as it has so much wax that you will never get a bond between the layers.

FIGURE 2.

Next, cut a piece of fir, mahogany, or what have you that is the length of the tube and shaped like A in Fig. 1. Cement this to the tubing as shown. I used plastic body filler (a polyester resin paste) available at automobile parts stores. After the paste sets up, cement two pieces of Vs in. hard model airplane balsa per B in Fig. 1. The resin paste can also be used for this. Round off the trailing edge and give the whole works another coat of laminating resin.

Now take some 5 or 7 oz. glass cloth and form it over the trailing edge per D in Fig. 2. A simple way to do this

is to cut the glass to a width such that the edges will miss meeting by about one inch at the leading edge, and lay it out on a piece of wax paper (Fig. 2, item E). Brush in a coat of laminating resin, and drape the cloth and wax paper over the balsa form. Press out the inevitable air bubbles, and use some clothespins (Fig. 2, item F) to hold the wax paper tight while the resin sets up. The wax paper will pull off after the resin sets and leave a smooth surface.

FIGURE 3.

Form the final layer of glass cloth over the leading edge of the tube (Fig. 3, item G), again using wax paper to achieve a smooth surface. After the resin is completely cured, any rough spots can be sanded out. If there are any low spots or if the weave of the cloth shows, spread on some of the body filler and follow this with sanding.

STREAMLINING ROUND TUBING

You can close in the ends by one of several methods. I cemented on hardwood plates that had been pre-cut to the proper shape . . . this was done prior to laying on the glass. Another method is to simply fill the ends with some more of the polyester paste. £>

Beautiful in its own right, this Piel "Super Emeraude", CF-WGD, also has the distinction of being the first foreign registered homebuilt aircraft to be based in the United States. The builder is W. G. Duncan, EAA 18073, who now resides at 7343 El Domino, Buena Park, Calif., and formerly lived in Canada. The airplane itself exhibits superb workmanship, but the Canadian registration had to be transferred to the fuselage. SPORT AVIATION

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