Hatz Biplane Association

I agree there. I just finished my center section. For the life of me I couldn't make the diagonals work with calculated numbers. I'm starting to understand tolerances. Hopefully my plane doesn't fly sideways.

I was thinking I missed something in the calculations as the drag/antidrag wires between the top wing compression tube one and two are different from the rest. I came up with 39.95" pin to pin and 39.55" (on average) pin to pin for the rest. I think I'll order them as different sizes for the four although 0.4" is probably adjustable in the threads.

I made mine to fit the available space since the T-88 on the doublers and the coating on the fittings added up to something. I also didn't start out at exactly 25" on center since I used my plans as a template for the ribs and they weren't 25".

I reconciled all the compression tube lengths except for #1 top wing. I get 25.0 (edge to edge) - 0.75 (spar thickness) - 2 x 0.125 (doubler plate both sides) - 2 x 0.090 (FSTW2 and RSTW2) = 23.82". Plan shows 23.805 (0.015 diff). There is no mention in the discrepancies. Am I missing something? Not that it makes a lot of difference.