thanks for making me think harder han. i now realize it won't work. crap! :( i thought i was on to something.
i don't think it's for the reason you describe though. the mast stops bending, not because the forestay tension goes down, but rather because the more it bends the more force it produces to counteract the tension, eventually reaching a balance.
here's my understanding of the problem:
in the normal way of doing things, with the back end of the halyard cleated to the mast, more air pressure on the jib increases the tension in the halyard and forestay, which bends the top of the mast forward, shortening the distance between the hounds and the jib tack. since the forestay remains the same length, it sags.
i had naively thought, that if a constant tension was applied to the back end of the halyard instead, and the jib was set to fly freely with no forestay, that the mast would never be pulled more forward, and the problem would be solved.
indeed i still don't think it is pulled forward with more air pressure in such a system. the problem though, is that the halyard is lengthened instead, because the whole mast is lifted up out of it's bury. more halyard for the same distance between the hounds and the tack creates sag. just as with the normal system.
thanks for pointing out the camberspar. first i heard of it. can't find a website for bierig, but a description can be found here:
http://www.freedomyachts.org/viewtopic.php?f=16&t=8583
i understand the benefits of a wishbone boom in controlling twist, but so far i'm not understanding how it controls sag. will keep thinking...
ben
>Ben, it is too crazy.
>
>Don't forget the mast stops bending forward BECAUSE the tension goes down. When you find a way to keep forestay tension up the mast will bend further and further.
>
>Perhaps you should research the CamberSpar by Bierig sailmakers when you worry about headsail sagging.