I'm trying to center my ailerons and not sure what to do. It's a semi-symmetrical airfoil. Holding a straight edge along the bottom shows that the ailerons came mounted a little high - there is a 1/8" gap. If you hold the straight edge on the top of the wing, the ailerons line up. I thought you were supposed to center the ailerons with the bottom of the wing. So should I hold the staight edge on the bottom of the wing, allow the 1/8" gap, and keep the aileron in line with the straight edge, or should I just center the ailerons using the top of the wing, or should I do it on the bottom of the wing and have the ailerons touch the straight edge at their trailing edge? I thought this happened because the ailerons warped with the crazy change in weather we just had, but just realized it's because it seems at some of the hinges the aileron is in line with the top of the wing, and some at the bottom.

Thanks. I've been without a plane for 2 weeks do to bad chain of events (2 crashes) and am about to maiden my Dolphin TOMORROW!!!

Edit: I remember people saying they liked their ailerons maybe up a hair, so I went the line of the top of the wing. Looks good, should be ready for an amazing day tomorrow!!! First low-wing, first tail dragger, and set up with dual rates

can you slap up a quick pic?

Try centering them by looking from the wing tip . place the ruler on the wingtip and then center.

One of the hardware stores I go to gives away wooden yardsticks. Every other time I go there I pick one up. I cut them as I need to for 12, 18, and 24 in. rulers. When I go to mechanically align surfaces, I take 2 of whatever size it takes, and either 2 spring loaded clothes pins or a couple of the little spring clamps from Harbor Freight and put them along the surface, one at the top, one on the bottom. That gives me the best mechanical alignment I can achieve. Now when I make the rod and adjust the clevis for no pressure back or forth when I slide the pin in, I know that the surface remains as centered as possible, and trim inputs should be pretty minor.

I'd center them from the bottom..any aileron droop can act like flaps...My maiden on a 4 Star 60 a few years back was a hand full because I aligned the ailerons to the top of the wing

If the top of the wing curves and the curve continues along the top of the aileron, you will have trouble aligning the aileron by the top. The trailing edge won't be straight back, it'll be back and down a bit, but the bottom will line up with the bottom of the wing, if the wing is flatbottomed.

If the whole aileron is 1/8" off the building board when it's top lines up with the top of the wing, you've got ailerons that are too small. The mfg should have made them with wider chord.

Is the whole aileron, or just the TE, 1/8" up?

With most flat bottomed wings, the bottom of the wing and bottom of the aileron should be on the same line.

I would have rehinged with new slots, making sure they were dead center.

Thicker ailerons would be perfect. Pretty much the whole thing is off.