Hatz Biplane Association

First off I want to say a belated THANK YOU to Melin Smith. I met him for the first time at Brodhead this July. I looked forward to many more informative times with him in the future but now with his passing I am turning to the rest of you for good information.

I have studied the plans for the CB-1 and the Classic Hatz. The basic differences I find are width, length, seat postion, brake position, recommended engine size and recommended gross weight. The similiarities are tube size and spar dimensions. I can't find any substantial differences that justify the greater gross weight. Knowing that the CB-1 spar analysis is for the 1400 pound gross weight plane I have concerns about boosting it up by 21 % and not increasing the strength to make up for it. Maybe I'm missing something. Please share your thoughts. I am ordering materials and want to feel justified in making the correct decisions.

BW

If I recall, the CB-1 spar analysis showed the weakest point being the C/S rear spar. The Classic fuel tank has an aluminum top skin that attaches directly to the spars. I would think that might improve the strength, but I'm no engineer and no one has done an analysis on the Classic.

To look at it another way, as far as I know there has never been a structural failure of either model Hatz and I know several folks have put them through their paces to one degree or another. I realize none of this has any hard numbers to back it up, but I would feel perfectly fine choosing either model. If you want to do hard acro, build a Pitts.