I guess you are right, I was looking at the pure force balance, directly using your arms like a bird, assuming the wing is a beam with a hinge, and the arms are all that hold it down. So is my statement wrong in that regard? Surely during the downstroke you would have to lift your own weight, in that case, like an athlete does on the rings, which would be the force at least temporarily applied in your equation. However, I suppose one would not design the machine like a bird, but like the Delfly drone, so the upstroke on one side assists the downstroke on the other side, and you would only need to expend the energy for level flight. Since birds are not build that way, I wonder how they manage to hold their wings out and soar for hours. Is it just their muscles holding their weight? I have seen some RC bird-like ornithopters fly, and they all were lacking a locking feature to stop the wing mid-stroke, so they could only glide poorly. To hold the wings out straight, wouldn't there be some power still required to overcome the static moment the wing generates at the "shoulder"?