Re: How much Flotation? And Where?
Tue, 4 May 1999 21:52:10 EDT

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West Wight Potter Website at URL
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In a message dated 5/4/99 4:35:10 PM Pacific Daylight Time, writes:

> Question #2: If a boat had a lot of addtional flotation, particularly
> low in the boat as in the bilges and under the cockpit floor (places
> where Bernie is proposing to add it), could that make the boat MORE
> prone to turtling and more difficult to right once inverted. It seems to
> me that if the boat was on it's side and was entering the cabin,
> flotation in the bottom of the boat would actually _encourage_ the boat
> to continue over into the inverted position whereupon the flotation
> would make it very stable upside down.
> Would it be wiser to place flotation high in the boat, like behind the
> cockpit seat backs to encourage a "right side up" attitude?
Hi David,

I think you're on the right track here. A few books I've read have said that
positive floation should be located as high up as possible. If you can't put
it on the cabin roof (who can spare any of that precious headroom?!?) they
recommend putting half on each side at the widest beam right under the deck.
That way, half of the total foam exerts a righting moment if the boat is laid
over 90 degrees on its side and swamped. If it's upside down, it will be
easier to right it if you can just get it tipped over a little.

As to how much, sea water weighs about 64# per cubic foot. My P19, weighs
about 1275 and fully loaded with gear, weighs probably 1800#. So about 28
cubic feet of foam should easily dispalce enough water to keep the boat
afloat. Bruce at IM told me they put in more than that in the new boats (32
cubic feet maybe, I forget). In fact, less than 28 or 32 cubic feet will do
the job, since fiberglass is less dense than water (the boat itself displaces
water). I'm assuming the crew is wearing PFD's or has them on board and
therefore requires no added flotation.

When I bought my new/old P19, there was much more than 32 cubic feet of
styrofoam in it. I measured the volume at the back under the cockpit, and
under the quarter berths (where the newer boats have sizable shallow lockers
for storage) and figured out how much was in there. Then I removed quite a
bit from under the vberth until the total was a little over 30 cubic feet.
More than that just takes up valuable storage space without adding any safety
to the boat.

Judy B

Judith Blumhorst, DC
HMS18/P19 Fleet Cap'n, Potters Yachters
1985 WWP19 #266 Redwing
Sailing on SF Bay, CA
(5-35 knot winds, 2-4' chop, 2-6' swells, and currents up to 6 knots)
Visit <A HREF="">Judy B's
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