In article m, mmc wrote:

Don't know if anyone else has pitched in on this. A ballasted keel mono hull
sail boat wants to right itself the more it heels due to the ballast and
leverage. Monohulls get knocked down at sea and stand back up on thier own,
unlike thier multihull counterparts. I guess if a sailor is real lucky and
the hull is lying across the wind and you get a good gust it could push the
boat upright but if the sails are still set, it might just keep going over
and back into the same predicament.

Wind doesn't capsize keelboats, waves do. Wind may knock it flat, but
nowhere near enough to capsize. Once the boat has been knocked flat the
wind no longer has any effect, as soon as the gust has passed the boat
comes back up-righ.

If a keelboat does capsize, and, as I think you're saying, the wind
against the keel is enough to right the boat, all a strong wind can
do is knock the boat down again, not capsize it.

Of course, anything that's not ballasted is a going to experience
things differently.


The flotation at the masthead is an idea that Hobie came out with way back
when, necessary to keep the boat from "turtling" when the mast fills with
water. With a Hobie, turtling would be a huge PITA, with a larger multi
nothing short of a crane is going to make things right (or upright haha).
There's a thing called "righting moment" when talking about mono hulls which
is the point the hull has to attain in order for the boat to recover from
turtling. On my Traveler 32' the righting moment was 165 degrees,

I think you mean the angle of vanishing stability. The "righting moment"
is completely different, it isn't a point, it's a measure of force that
is calculated by multiplying the distance between the centre of gravity
and centre of buoyancy by the boat mass.

Your AVS may be 165 degrees (that's very high). What that means is that
when the boat is tipped that far from upright it is as likely to fully
capsize as it is likely to come back upright. The correlation of this is
that, as you say, tipping from inverted by more than 15 degrees would
cause your boat to right.

meaning if
the boat completely capsized, it would recover on its own once the hull
rotated 16 degrees from exactly upside down. Like when the next wave pushed
the boat sideways and the resistance offered by the rig caused the hull to
rotate on it's long axis.

Justin.

--
Justin C, by the sea.