Good to hear you used 3 hinges

But if that gap is anywhere near 1/2 inch then that is way too large. Ideally you want to just be able to slip a piece of paper through the gap. At the most the blade of a butter knife. A gap that is larger than that will certainly result in flutter and you'll loose the surface in mid flight.

If I were you I would definately get some help putting this together instead of going at it on your own. They could've prevented many of the problems that you've run into while building your SE.