Re: [PSUBS-MAILIST] Minn Kota - Thrust

["Karl & Shirin Fuller" <fullerk@voyager.co.nz>]

> > I understand that the teardrop is the most
> > effecient sub design, from a laminar flow and friction loss standpoint.
>
> Actually...
>
> I read, a couple years ago, a paper by some guys in Japan, who did some
> extensive studies of underwater laminar flow, and they found that a
> modified teardrop, with the main bulge moved back to about the half-way
> point, was the most efficient form underwater.
>
> Had something to do the the tip vortex messing up the flow, and that shape
> minimized the vortex much better than a straight tear-drop.
>
> I'm trying to find the paper reference, but no luck so far...
>
> Later,
> Jon

Actually guys,
Evolution has honed some of the most efficient underwater shapes. Take a
tuna for example. They look fast when they are stopped, which is never, they
travel thousands of ocean miles and I've done a few ,as an engineer, on a
perseiner, chasing them.
You will probably find different speeds require  different forms as well,
particularly when looking at the difference between a  mainly surface sub
and one that remains under the water for long periods.
I understand that the reason a dolphin is so fast is that it can change
shape to some degree to accommodate the changing pressure waves. I've chased
a few of those to, not with a net but a snorkel and camera.
I pay my respects to you Paul and Big Dave for your constructive views on
the gun problem and like Carsten, can see it from a another perspective, not
being American. In New Zealand there are guns and there have been mass
killings but the police don't carry guns, but do in their cars. I too think
there is a place for guns but like you Paul, am prepared to do without if it
brings a more sane society. I'm happy to go and have a shoot up with some
paint ball guns, now that was fun !!! Paint ball torpedoes, now that would
be fun to........ !
TTYL,
Karl