mrbigg

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anyone know if a 1" diameter aluminum wing tube will be big enough for an 84" span ultimate bipe? each wing will have a 36" long tube and 1/2 inch square spruce spars. I'm thinking that will be big enough with the spruce spars, interplane struts, and cabane, stiffining everthing up. The fuse will be about 1 3/8" thick where the wings meet the fuse. with that fuse thickness, a little over 17" will be in each wing half, is that enough?

Down&Dirty

That should be fine. You might even get away with an even smaller diameter or shorter length. Remember, on the Ultimate (or any similar bipe), a tremendous amount of strength and rigidity is derived from the joining of the top and bottom wings to one another and to the fuselage. You essentially create a solid box structure. So as long as the wing tubes securely join the wing panels together and tie in directly to the structural spars of the wings, they should be plenty strong. Hope I could be of help

Trivia: Walter Pitts had aeronautical engineers determine the minimal spar thickness for his original biplane...they came up with only 5/8", and that's what Pitts used.

mrbigg

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thanks for the reply. i think your right, itll be plenty strong.