Hatz Biplane Association

the upper and lower surfaces just end at the trailing edge area....they do not meet and there's no (vertical) line indicating a flat surface.

John,
I just built my end rib and is is significantly different from the end rib on the plans. That end rib is for the lower wing and it lays over on a much steeper angle than the 1.5 degrees of the upper wing. Because of this it is drawn much thicker and it has a cutout for the wing walk. I traced one of my wing ribs and cut well outside the line. Then I set my wing at 1.5 degrees bolted to the center section, and placed the big rib where it belonged. From there it was a lot of marking and sanding. I used the plan just to get the cutouts.
I just realized that I never answered your question, sorry but I have no idea.

That helps a lot Ed...thanks. So the one on the plans is for the bottom and, the cutout is for the wing walk; certainly makes sense. So for the upper, I'll 'wing' it. Just looked at Scotts page...can't tell but looks like the front is beveled. Well, I'll make it up as I go along. Thanks again.

Ed and John:

What I did is make the bottom cutouts for wing attach bolts as did Ed in a blank of 1/4" ply. Then I clamped this to the end rib of the center section with its bottom edge flush to the bottom of the center section. I simply traced the outline of the center section onto this blank, placing a piece if 1/16 ply on the top of the center section end rib to simulate the thickness of the tank.

When I join this rib to the leading and trailing edges of the wing panel, I will then bolt the spars to the center section as Ed did and raise the wing panel up to the designed 1.5 degrees. I'll space off the end rib from the center section about 1/8" at the same time. Doing all this will result in the end rib of the wing panel being parallel to that of the center section, with the wing panel dihedral set at 1.5 degrees. I must also note that I have cut the root ends of the main and rear spars at an angle of 1.5 degrees to allow for the dihedral as well. The leading and trailing edges will butt up to this rib, and the spars will only contact the rib at their upper edges at the root end due to the cutouts. Shimming may be required to make proper contact with the spars, but shouldn't be a problem.

Hope all this makes sense.

Since I'm waiting for the wood to be delivered and I have free time, I've decided to build a mock-up with cheap wood from Lowe's (for wing forward/aft spars, CS spars and both CS and wing end ribs). That'll give me a chance to 'practice' drilling the holes and using the drill bits I bought, as well as verifying the fit and alignment between the wing and center section. Thanks again for the help.