Re: what is your bananafish?

Dang, I love it when Engineer types do their jobs :).

Jim

Yocum Daniel GS 21 CES/CEOE wrote:

>There's two ways of moving on the surface of water. The first is
>displacement and is the most stable the second is planing and the least
>stable. A displacemet hull pushes or plows a wave and the ship rides in the
>valley of this wave that is why its speed is limited since it can only push
>so big a wave. Now a hydo-planing craft rides up out of the water, as the
>water line approachs the screw the craft becomes increasingly uncontrollable
>and susceptible to distablizing forces, watch a speed boat race. Now,
>engineers have come up with compromises. For the planing craft they
>developed hydro-foils which allow it to climb up on legs with wings for
>feet, a mercury image. Fo displacement craft there are several ways to to
>'ride' out of the wave trough. In the age of sail the Americans piled on
>incredible amounts of sail and shifted the center of effort to the stern
>which lifted the bows to help it 'climb' the wave. Now the bulb at the bow
>I believe (I am not totally sure) has more to do with 'cutting' the water to
>allow for a bigger wave thus higher speed not directly limited to hull
>length. It's actual effectsare that it helps when getting up to speed and
>alleviates power to displacement problems. You get more bang for your
>engine buck. Now, bulbs on the keels of sailboats are to increase final
>stability to allow for more sail area.
>
>
>Daniel
>more than you ever needed to know.
>
>-----Original Message-----
>From: Scottie Bowman [mailto:rbowman@indigo.ie]
>Sent: Wednesday, December 18, 2002 11:32 AM
>To: bananafish@roughdraft.org
>Subject: Re: what is your bananafish?
>
>
>
> '...1.333 times the square root of its water line length ...' etc.
>
> Which is, I understand, one of the reasons for the 'bulb'
> extending beneath the prow of so many modern ships.
> (Something about drag reduced by an exact number of
> waves - ? 3 ? - at the waterline.)
> Yet I don't THINK destroyers or their like carry such
> probosces. Wrong?
>
> Scottie B.
>
>
>
>
>
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Received on Wed Dec 18 15:31:38 2002