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On 23 Oct 2004 12:26:51 GMT, ospam (Stephen Baker)
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

I reckon the guy who said to talk to a spar maker had the right idea.

At least check out a google of

"righting moment" multihull

If you can weigh the boat, each hull singly, that would help. Yopu don't have
to take it apart, just slide a scale under each hull in turn and record the
weights (yes, it can really be that simple.)
From that, and with the 50 litres of WB, a rough RM can be obtained.

This is a really light boat, IIRC.....here we go..... "23ft proa
weighs 200kg unladen."

Sounds scary actually, as a cruiser.

This means that weighing the boat and using that as a righting moment
would be questionable, as the weight of crew and gear would
_significantly_ alter the system. You need to weigh in "cruising
trim".

And how far apart are the hulls, etc?

Also some proas' righting moments when the ama is to the lee will be
the floatation capability of the ama.

What you need to do is place the boat in the water and do some real
righting force tests, under loaded conditions IMO. This was not
uncommon practice as I remember it.

Also wrt multihulls. They release pressure on the mast much more by
acceleration than by heel. Their righting moment should never be
_needed_ ....joking G.

Seriously:
- they load a mast very high in a puff, because they are not
supposed to heel more than a very small amount. IIRC (and it's been a
while) and extra 20% (?) or more needs to be added to the mast/stay
strain for a multi over a mono.
- when sailing at speed on a brorad reach, and _being kept flat_ as
multihulls largely should, their high speed generates significant
apparent wind. This has to be accounted for.
- multis can actually suddenly _increase_ their righting moment as
the weather hull lifts from the water, or as the lee ama of a tri /
proa touches the water.

Also, on a multi, especially a lightweight one, the mast and stays
hold the boat together. So there are many other strains on the rigging
as the boat gets twisted about by wind and waves.

I mucked about designing, building and repairing cats. I have owned
and sailed several, including a Crowther 23' International. It weighed
maybe 450Kg unladen, and had a _heap_ more mainsail than that being
suggested. But it had a huge mast. 150mm * 100mm * 4mm, maybe. I can't
find the specs any more.
************************************************** ***
Have you noticed that people always run from what
they _need_ toward what they want?????

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