Hatz Biplane Association

Thanks for that information, John.

In other news, I've finally concluded, thanks to the Forum Archive, that the classic plans are in error. The plans give incorrect dimensions for the spars, which are too tall by 5/32" at the front spar and 5/16" at the rear spar. The spars should be built to fit the centre section end rib, which makes the front spar 5-1/32" at the high point and the rear spar 3-13/16" at the high point.

For anyone else getting to this point, my considerable reading has uncovered several builders who have had to solve this same puzzle and come to this same conclusion. There has never been a failure of a Hatz centre section spar.

Nick

Hi Nick,
I mentioned that I used the Finnish birch ply. This is NOT aircraft grade, although I think it runs circles around aircraft grade. The 6 or 7mm I bought has around 13 plies, all birch. I boiled samples in water and there was no delamination.
Al