Originally Posted by ontherocks83
I get the windward part as it seems logical, but can you explain how that happens in a following sea? Do you mean boats like Island packets are more easily capsized in big following seas?
Sailing downwind, in a following sea, the waves overtake you whatever. Suddenly the big one raise you to its top where from you start sliding forward/downward at downhill speed. The efficiency of a keel is function of the length of its leading hedge (Not its surface) but it's also function of the square of the speed of the sailboat!
Suddenly as you race downward your keel becomes far more efficient & turns hard your sailboat to port or starboard depending. Now the full surface of your full keel moves SIDEWAYS DOWNHILL against the water
... Guess what ? It's like applying full brake under the water
while being push by the top of the big one above the water !
Moitessier thought that he had been rolled bum over head
, but this happening so fast, I think he couldn't analyse it clearly.
I personally think that his Joshua was going downhill at full speed on the slope of a freak wave, his keel became far more efficient because of the sudden increase of Joshua speed, so doing the keel turns Joshua 90° where the top of the freak finished the job by rolling SIDEWAYS Joshua. In any case ('cause I could be wrong in my analysis) all Moitessier's stuff that could stick to the ceiling where up there after the joy ride
With a fin keel -as you luff- the area of your keel is much smaller for the same upwind efficiency & therefore will represent less of a brake force as the sailboat & keel slide downward/sideways; this doesn't mean that the fin keel sailboat won't be rolled sideways, but this will happen far less often
PS: Pardon my English
for I'm an almost bilingual frog...