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From: Robert Gainer (no email)
Date: Mon Aug 02 2004 - 09:43:56 EDT
Joe,
I did not have the lines to your boat so I just picked some numbers for the
area of the water line, beam etc that are probably in the ballpark. For what
you are doing it won’t make much of a difference. The formula is .35 times
the area (in square feet) of the waterline squared then divide that by the
beam (in feet).
Beam 10 feet, area of water line 150 sq ft so, 150 * 150 = 22500 * .35 =
7875 / by 10 = 787.5 foot lbs. or 1/2" up at the bow by moving 787.5 pounds
one foot aft.
I hope this helps,
Robert Gainer
>From: "Joe - G4XRZ" <>
>Reply-To:
>To:
>Subject: [world-cruising] Re: moving batteries to another spot
>Date: Mon, 02 Aug 2004 12:39:13 -0000
>
>Hi Robert
>Please can you clarify the formula ?
>
>is it ... "to trim 1" is .35(A(squared)/B)" ?
>(as per my brackets ?)
>I am using a rough conversion of actual area to wl area of (wl-l *
>wl-b)*.7 to 0.8 depending on design (without getting the paper out
>lol...). With that I seem to match your figures.
>
>Joe.
>
>
>
>--- In , "Robert Gainer"
><robert_gainer_2 at h dot dot dot > wrote:
> > Tom,
> > The approximate formula for moment to trim 1" is .35A(squared)/B.
>Where A is
> > the area of the water line and B is the beam at the water line. A
>is
> > squared. So if your WL length is 52 feet and your WL beam is 13
>feet I get
> > an approximation of 7,000 foot-pounds to trim 1". And that is ½"
>at the bow
> > and ½" at the stern. So 1,600 pounds moving 15 feet is 24,000 foot
>pounds
> > and divide that by the 7,000 foot pounds to trim 1 inch and you
>will trim a
> > total of 3.4 inches. Again divide that into trim at the bow and
>stern so the
> > bow will go up, 1-3/4 inch and the stern will go down 1-3/4 inch.
>For the
> > nitpickers out there the center of flotation is a little aft of
>the center
> > of the boat so the bow will trim up a little bit more and the
>stern will
> > trim down a little less. The difference is about 5% more at the
>bow and 5%
> > less at the stern. Check my math, and I am guessing at your
>dimensions.
> > All the best,
> > Robert Gainer
> >
> >
> >
> > >From: "Je Ne Se Pas" <thomas dot stuifzand at c dot dot dot >
> > >Reply-To:
> > >To:
> > >Subject: [world-cruising] moving batteries to another spot
> > >Date: Fri, 30 Jul 2004 21:59:14 -0000
> > >
> > >Hi All,
> > >
> > >We are having currently 6 x 8D as the house battery and we are
>about
> > >to upgrade to some serious batteries (840 pounds).
> > >
> > >The new batteries weight approx. 1600 pounds and will not fit in
>the
> > >old spot.
> > >
> > >The current batteries are about midship and about 1 foot in from
> > >starboard (not the best place you would think).
> > >
> > >We have space just after the engine room, right on the center of
>the
> > >boat. beam wise we would move only a few feets, but length wise
>we
> > >would shift a lot of weight about 15 feet further aft.
> > >
> > >Now... we are talking about a 35 metric tons 60 foot boat here,
>so in
> > >my opinion it should not make to much a difference, but I would be
> > >really interested in your opinion.
> > >
> > >Thank you, Tom
> > >
> > >
> >
> > _________________________________________________________________
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>cid=3963
>
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