please burst my bubble before it explodes with enthusiasm:
bearing in mind that i've never even seen a proa or a balestron rig much less sailed one, my understanding is that the performance of the latter on an unstayed rig is less than optimal because the jib shape suffers from poor halyard tension when the mast sways forward.
one possible solution would be to use gravity to provide a constant tension instead of a winch and a cleat, which provide a constant length.
the simplest instantiation is just a weight attached to the halyard after it turns through the upper block and hangs next to the mast. this would take a LOT of extra weight though.
easy to ameliorate this problem a bit though by attaching the weight to the halyard with a block and tackle. still, it's extra weight.
is there a weight already on board that could be leveraged? how about the mast itself??
lead the line from the B&T through a hole in the deck and down to another turning block at the bottom of the buried mast, and then back up to an eyebolt on the undersurface of the deck. pull the mast partly out of its socket with the B&T. halyard is now loaded by the weight of the mast times the ratio of the B&T.
see balestron.pdf in the files section.
is that enough tension?
visionarry's mast is 100 kg according to an old post i found here.
the I and J of its foretriangle are 10m and 3.75m as judged from a picture i found in harryproa.com's gallery.
so the jib is sized somewhere between that of a j/105 and j/120, which use halyards rated to 5000 kg according to westmarine.com.
what fraction of that do they actually pull? no more than half i would hope. if it were as low as a fifth then a 10:1 block and tackle would be enough.
a 10% displacement of the tip of the mast at full righting moment, per rob's e-mail below, results in 38cm slackening of the jib, if my trig is correct.
so a 10:1 B&T means the mast moves up and down 3.8 meters. yuck.
however, if we use a "racing" mast instead, it will be stiffer AND heavier, both of which work to reduce the extra bury needed.
plus, the 10% displacement is at the tip. visionarry is fractionally rigged. what matters here is how much the hound moves.
let's say a racing mast moves 6% at the tip, and we use a 3/4 rig, that's only 4.5% then at the hound, which is 17cm of slackening and 1.7m of mast travel.
also, with the mainsail in place and tensioned, to what extent do unstayed masts move fore/aft versus side-to-side? i would guess the former is smaller than the latter.
i think one could engineer the numbers to work, but am worried about practicalities.
am i way off base here?
ben
> Love crazy ideas. Look forward to hearing about it.
>
> No idea of the actual amount. Usually pull it up until the mast is slightly
> bent forward, then when the main is sheeted on the stretch in the halyard
> and jib luff keep the hounds near enough directly above the deck. Then the
> mast bends, the distance to the hounds reduces and the mast bends aft at
> which stage the loads on the jib halyard are dictated by the breeze and the
> mainsheet tension.
>
> Because of the mast bending and straightening, it does not 'whip'. As the
> loads increas, the mast bends more, as they decrease it straightens. Both
> maintain tension on the halyard.
>
> The mast is designed to flex between 8 and 10% of it's length at hull flying
> load. Less than this for a race boat
>
> Hope this helps, but suspect it won't. Any other questions, let me know.