Recommended procedure is to dampen the cloth (moisture cures the polyurethane), and iron on the patch against a flat backing surface. Then you get enough of a cure within a few minutes for the patch to stay in place. 

Thanks David, sounds ideal and I will get some.  It is just the tiniest hole and I think the material got pinched against the mast by the badly bent top batten.  I'm going out for a trial sail of the new yard tomorrow (and to get some photos taken from a friend's boat) but the winds are only 10 - 15 knots and I don't think the sail damage will matter - I am amazed at how tough Oddyssey 111 material is.  If I was crossing an ocean I think it would hold up until I got there, even though I don't have vertical seams to contain any damage.

Does anyone have experience with repairing sails built with Oddyssey 111 cloth?  I have just found a small hole chafed through my top panel - most likely caused by the bent battens pinching a fold of material against the mast after breaking the yard.  I can (and probably will) sew on a small patch of course, but if this was a Dacron sail I'd just put a bit of stickyback material on both sides of the sail and forget it.  I have some offcuts and am going to experiment with contact cement but am interested to know if there is any information out there.  It is, I must say, just a tiny hole and I am very pleased with the way the sail stood up to the considerable strains imposed on it when the yard broke.  The first time I handled the sail I was a bit uneasy about how light the material was but now have no doubts about its strength.