Cat rig "luff & swoop" behaviour

[Ambler]

This query arises from experience with my previous cat-rigged dinghy, which had a shroud-supported mast. I'm thinking it's probably common to any non-wishbone catboat with the mast positioned forward (of the center of the hull's lateral resistance?) The problem was as follows:

If I had to leave the sail untended for some reason, in any sort of a breeze, I'd bring us head to wind & let go the sheet; but left to its own devices the boat would fall off the wind until the boom fetched up on the shroud, then the sail would fill and suddenly we'd be sailing again, out of control - heading up with a sickening swoop until the sail would once more luff head-to-wind; whereupon the cycle would be repeated for as many times as it took me to get back in command of the situation. Not the kind of experience I enjoy, by myself in a small boat with a stiff breeze blowing.

I'm building a B&B Spindrift 12 and I'd love to be able to avoid having this sort of experience with it. But short of rigging it so the sail can swing through 360 degrees (how could I do that?) I can't imagine a way to avoid the problem.

How do others avoid or handle this situation?

[Hirilonde]

I think you will find that if you sheet off for a close reach and leave the helm a lee or even unattended, the boat will head itself up any time the sail fills a lot more smoothly than your previous boat.  I often leave my S9 rigged and tied astern of my Renegade in light air and she does this all by herself.  It would work in heavier air too, but I don't like flogging my sail.

[Tom Lathrop]

[quote author=Hirilond

[Ambler]

Thanks for the replies, Hirilonde And Tom. I've been away for a while and didn't see them till now.

Sadly I only have "half of" a cat ketch so that solution isn't available to me

I think Tom has it right: with tiller abandoned the boat can only be kept head-to-wind, or on some stable heading, by an external force (such as your tow rope, Hirilonde.) In fact during an insomniac night I'd already decided it would be worth while to try a sea anchor dragged from the bow, with the rudder and board raised. Wondered if the sail should be sheeted in but probably best let fly. The boat isn't launched yet - solstice is the "fully rigged" target date - so I can't try it now. But it's the only solution I can think of other than a rig that can rotate 360, or altering the underwater geometry with a forward board that only gets lowered for heaving-to.

I'm not about to try either of those, but on the latter I seem to remember reading that Thor Heyerdahl carried out sailing maneouvres on the square-sail Kon-Tiki raft by simply shoving boards down between the logs at varying fore-&-aft locations.

I guess recalling that, betrays my age (sorry, make that "vintage" .....)

Cheers, Alexander.