Re: Main and Jib Trailing Edge Flapping
They don't "flap" under 25 knots? If they did, I'd say they may be blown out (depending on age) and you should go see your sailmaker. But if you see a lot of "belly", that could be an indication to do the same. Normally you'd tighten halyards and outhaul (main) to flatten a baggy sail, but that will only accomplish minor flattening.
Have you moved jib leads forward some? that could tighten the leech, though possibly too much if indeed the leech is all stretched out.
Personally, in 25 knots, just about all of my main and jib would "flap", I'd be feathering just to keep the boat on her feet. Although, typically in heavy air it's the forward part of the sails you carry the luff in, especially the main.
The more I type, the more i think you may have blown-out sails with too much draft and stretch for breeze of any strength. But a sailmaker, I ain't. Invite one to come out for a sail and listen.