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[PSUBS-MAILIST] Underwater pod on surface vessel/ was NEW LOGO STINKS!!!
--- 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
=====
"Balee haih-aih ha-hutcha see,
Sanana na hutcha heah."
- Marvin Gaye
=====
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