Re: [PSUBS-MAILIST] Underwater pod on surface vessel/ was NEW LOGO STINKS!!!

["Sean T. Stevenson" <ststev@uniserve.com>]

I think you missed a square root term:  Surface vessel theoretical hull speed = (1.34 x LWL)^1/2

-Sean


On Fri, 13 Jul 2001 08:24:36 -0700 (PDT), Lew Clayman wrote:

>--- VBra676539@aol.com wrote:
>> Gave them almost a knot increase at cruise speed. More importantly, what does 
>> that have to do with the Subject Reference of NEW LOGO STINKS!!!?
>> Vance
>
>It has nothing at all to do with that any more... the pod thread is a spinoff.
>
>Surface vessels are limited in speed by a surface effect, perhaps unfamiliar to psubbers as it
>does not apply underwater - surface waves plowed up by the bow cause a bow-up pitch once the boat
>exceeds "hull speed" which is generally quoted as 1.34 x waterline length in feet = hull speed in
>kts.  A surface vessel which does not plane (skip like a stone) begins to encounter sharply
>increasing wave resistance at that speed and many cannot go faster without burning huge amounts of
>fuel, or cannot generate the needed power even at their maximum output.
>
>Extending the effective waterline length by adding a pod at the bow would have the secondary
>effect  of slightly increasing the limiting speed (and with it the whole speed vs fuel curve,
>including the optimal cruising speed for fuel efficiency) but a cleverly designed pod might also
>lessen the amplitude of the surface wave and with it the drag due to waves at all speeds, letting
>you go faster than the optimum for cheap...  Cf the bow extensions on large cargo vessels: less
>drag, better efficiency.  In other words, if you imagine a graph with speed as "x" and fuel usage
>as "y" then a very good pod would stretch the curve to the right and down, both good ideas.
>
>Does anyone know the form of the bow pod, it's overall dimensions, and the length of the vessel w/
>or w/o pod?  That'd help understand what's happening a little better.
>
>But in any case you've got me thinking now - a sailboat with a deepish and bluntish bow and a
>window in the forefoot (bow, underwater) might be just the ticket for me.... at least to start
>with... ok, two windows, one to either side... 
>
>-L 
>
>
>
>
>=====
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> Sanana na hutcha heah." 
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