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West Wight Potter Mailing List maintainer
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Lars,
Thanks. I stand corrected on the story of the Edmund Fitzgerald. Thank you
for giving us the correct details. Others folks wrote me too and made me
wonder about encroaching senility.
You friends with the 38-footer are describing something other than
recovering from a turtle, I think. I think your friends are talking about
Case 1 and Case 2 that I describe below. I was talking about something
different. So I'll clarify my post.
Wind usually doesn't knock a ballasted boat down past 90 degrees or so,
because the sail dumps the wind when the profile is reduced. However,
confused seas and breaking waves CAN and frequently do knock boats down past
90* and even past 120-140 degrees during fierce gales.
Case 1.) If a boat is rolled over, and if the sails are not rigged (ie
during a storm), the momentum of a heavy keel will keep her rolling past
180, completing the roll to 360, and voila! the boat is back on her feet.
If the sails are rigged, the drag from the sails probably will prevent the
boat from completing the second half of the role and she'll stay inverted at
180*
Case 2) I you knock a properly designed, ballasted off-shore monohull
cruiser as far as 120* from vertical, the weight of the keel/ballast (plus
forces from hullform stability) will be sufficient to reverse the knock down
and set her back on her feet. 120* recover from a knockdown is in the loow
end of the generally accepted range for a safe open-water cruiser.
In both cases, your friends are correct. But the question focused more
specifically on the differences between righting a turtled dinghy vs a
turtled keelboat that's sitting complacently, upside down in the water.
Case 3) If a boat is floating upside down with the keel to the sky, it will
be pretty stable in that position, with the keel's CG positioned precisely
above the center of bouyance of the hull. With a wide beam, it will be quite
stable in the inverted position, especially if the sail is hanging below the
boat like a sea anchor. (Isabelle's racing boat had a fine, pointy bow for
low resistance and high speed, and a wide flat aft section for planing with
humungous sails)
In the latter situation, you need something like wave action or a stocky
norseman :^)) to roll the boat over enough so the keel's CG is outboard of
the center of bouyancy. Once the CG is far enough outboard, the wieght of
the keel exerts a moment arm sufficient to right the boat.
At least that's how I understood the stuff I've read. I'm no expert, just a
motivated student, so I'll accept it graciously if someone corrects me.
If anybody needs more explanation than that, they'll have to go research it
themselves, because that just about exhausts my knowlege of the topic.
Fair winds, Judy B
PS. Lars, I'll betcha $10 I'm mostly correct about case #3. Looser buys the
drinks. ;^)
> -----Original Message-----
> From: Lars S. Mulford [mailto:mulford@bellatlantic.net]
> Sent: Wednesday, February 16, 2000 6:43 PM
> To: ecpa@onelist.com; wwpotter@tscnet.com
> Subject: Re: terrifying the uninitiated...
<<snipped>>
> Judith Franklin Blumhorst wrote:
>
> > In a keel boat, you depend on waves to roll the boat
> > over enough so that the keel weight does the job of righting
> the boat. The
> > heavier the keel and the narrower the hull, the less wave
> action you need to
> > perform the task.
>
> Judy:
>
> This isn't necessarily true and I don't think you can hold all blue water
> cruising designs to this. The 38' Hans Christian owned by
> friends of ours who
> cruise the coast and points beyond disagree, saying that the
> sheer weight of the
> keel is what has recovered them from situations like this. Wave
> action can
> help, but it can also hinder. Making a blanket statement that
> keel boats depend
> on waves to right the boat is not altogether accurate.
>
>
> > If I recall correctly, the theory is that Fitzgerald rose up on
> a wave, dove
> > down the backside, poked her nose through the front of the next
> wacve and
> > hit her bottom, smashing her hull to pieces. Lake Erie is very
> shallow in
> > places, causing huge waves when gale winds are blowing across
> an open fetch.
> > A very dangerous place to be in a storm. .
>
> A couple of problems with this. First, the EF went down on Lake
> Superior, not
> Lake Erie. There are several theories as to her demise, with one
> of the most
> accepted being:
>
> She had bottomed out and was taking on water gradually, losing buoyancy
> throughout the storm. And then as she crested one wave and the
> stern lifted,
> her bow dug into the next and she suffered a catastrophic lose of
> bouyancy by
> hatchway failures and she went straight to the bottom, breaking
> in half when she
> hit the bottom from extreme force.
>
> The EF does not sit in shallow water.
>
> --
> "Sea" ya!
>
> --Lars S. Mulford, President
> East Coast Potter Association (ECPA)
> Come visit us at http://members.tripod.com/~SpeedSailor
> s/v Always P15 #2125, lateen rig, sailing greater Chesapeake region
> "Forgive, and live. Life is worth the challenge of living." --LSSM
> "Love is good; Love hurts; Love sustains; Love remains." --LSSM
>
>
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