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6

 What was not mentioned in my last article is that all work on the plane itself was prefaced by construction of a very large worktable, 16’x 8’, made as flat and level as I could manage. All four wings and the fuselage will be built on this table and then it will be dismantled. Here is a (not very good) picture:

R-80 Tiger Moth – Wing Spars

 

 The front spar is a wooden I-form spar. It consists of two spar caps, top and bottom, with a web of 1/8” plywood in between. The spar is built by gluing the web pieces into grooves which are already cut into the spar cap stock. When the glue has hardened, stiffeners and reinforcements are glued to the web along the spar on both sides.

The rear spar is a wooden C-form spar. It is similar to the main spar, except that the spar caps are glued to the face of the web, top and bottom, rather than the web being glued into a groove. The rear spars are not as high as the main spars, the web is only 1/16” and the caps are smaller. They are also strengthened with stiffeners and reinforcements.

With the ribs finished, and with visions of wings fluttering in my head, I next had to turn to the heart of a wing, the spars. The Tiger Moth wing has a main spar at the point of highest camber and a rear spar about 2/3 of the way aft from the leading edge. The two spars are separated by about 20” in a wing whose chord is 45”.