proppastie
Well-Known Member
Better to fail on the ground than in the air.....and why we test. It looks like classic Euler buckling of the top cap strip......So after my last test where there was buckling of the skin and adding stiffeners I mounted the wing properly upside down and at 15 deg. .... I made shelves so the sand would sit flat on top. (sorry no pictures with sand). at 354 lb (shooting for 698 total) or 50% or 2.5 Gs the top cap buckled....I obviously did not do the Euler calculation for that section like I should have.....it is somewhat discouraging....however a major goal of this project was to learn "Aircraft Stress Analysis" ....One more lesson is that the wing was talking to me......it seemed weak through that section but I did not properly understand what was going on and thought it would be stabilized through the drag spar and boom.....I can fix it..Those large angles at the center carry through should have been extended into the wing.....bad design on my part...and the wing will be heavier yet some more.