Thursday, November 1, 2007

Vertical stabs completed

Build hours: 272
The top rib and forward spar were positioned. The lightening holes were left out because the weight removed is negligible (see weight calc below), stiffening is minimal and warping during flanging is almost guaranteed!
Weight calc = Holes * pi * radius^2 * thickness * lb/in^3
lbs = 14 * 3.14 * .75 * .75 * .016 * .1
lbs = .04
ounces = .63!

Top rib installed.
Here the skin is clecoed into position for the final riveting. The skin was vacuum formed instead of "carpet formed" as described by Bill Spring and Morry. We hated to break tradition but after seeing the Sonex guys form their wing leading edges on YouTube?? we had to try it. A short video clip will be added later when the horizontal stab skins are made but we had so much fun forming the vertical stab skins that we couldn't stop:)!
The process was - make a rough pattern from poster board, cut out a skin blank, tape the rear edges together, wrap with 4mil plastic, seal one end and stick the shop vac hose in the other and seal. Finally, hit the switch, and before you can say oh crap, the skin is formed and ready for fitting. The process is easy and repeatable.
1) Cut your skins with the grain running in the same direction. The skin is stiffer and will form a different leading edge across the grain than with the grain.
2) The empennage skins do not require a mandrel since the skin stiffness stops the bend with a nice radius.
3) Clamp the skin on the vertical stab spar as plumb and true as possible checking alignment from every angle possible! Then, mark a line approx. 1/8" up on the bottom edge with a guide against the fuselage (just like Norm would do on This Old House:)). This will give the skin a good fit with the least amount of effort.

And here is the final product. The top rib has not been riveted so that the refuge from installation of the dorsal fin (coming next) can be dumped.

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