A Stitts Skycoupe Restoration Project

The Stitts Skycoupe is also known as Stitts SA7 D

Friday, February 24, 2012

Work Session 2/23/2012 - One wing taped

Nice warm weather allowed us to open our pots of dope and start taping the Skycoupe's wings.
On hand were Skipper Jim, Terry, Jack, Kent, Tim, Andy, and Chris.

With the expert guidance of Jack Phillips and Terry Gardner, the left wing is now nearly complete. We used three different widths of tape: 2", 4" and 6". The leading and trailing edges are done in 6" tape, the 2" tape covers the ribs and other critical edges subject to chafing, and the 4" tape was used on a few sections where 2" was too narrow and 6" was too wide. They are pinked on all edges (to prevent separation in flight should an edge come undone, very clever idea) and affixed to the surface with PolyBrush, mixed 3:1 with reducer. An iron at 250F was used to form the tape around edges, and a second coat of PolyBrush was applied over all tapes.

The order of tape application is critical, always considering the wind forces that would tend to pull them off. Tapes are applied in the following order on the wings:

1. trailing edge, 6" wrapped from bottom to top around thick trailing edge

2. 2" tapes over ribs, starting on the leading edge of the lower surface and affixed up to the trailing edge. Another 65" of virgin tape was rolled up to the trailing edge and taped temporarily. Two patches of fabric were cut and affixed around the wing strut attachment hardware that protrudes from the lower wing surface.

3. when all rib tapes are complete, the wing was flipped right side up and the remaining 2" tape was affixed from the TE to the LE, with some excess allowed to droop over the LE.

4. the rib tape overlaps by an inch on the LE and is then covered down the span with the 6" tape.

It all makes a lot more sense when you see it. It helps to have 2-3 people doing the work - two to brush on the PolyBrush and another person to lay down the tape, using pencil lines previously drawn to maintain straight alignment. Since the wings have a wide 5' chord, it really helps to have one person on either side. PolyBrush dries fast, so you can not wait too long to lay the tape down. And as Jack says, once it's on, don't mess with the coating - let it dry. Blobs can always be 'melted' off later with a bit of MEK.

One more point - before applying tapes, it is important to draw pencil lines where they will be applied, then brush on an extra coat of PolyBrush and allow this to dry completely. This prevents the coat needed for the tape to be absorbed into the fabric.

We were all pleased with the results, and if I ever figure out how to get the pictures I took off my $#$%#^&%!! new-fangled android phone, I will post them here, danged technology!

Above: Kent and Jim trim the pinked 2" tape prior to affixing along the rib lines of the upper surface of the left wing.

The wing's lower surface, tapes in place.

The wing's upper surface, tapes in place.

Below: Jim, Chris and Andy admire the work of the day, with nearly all tapes in place.

No comments:

Post a Comment