Re: Screw size and speed

[Paolo Velcich <pavel@mail.nauta.it>]

Alec...could it be possible to have an address for that industrial fan/blades...
I'm already interested on testing trolling motors for DPVs and always interested
in existing spares like props, blades and so far.
Thank you in advance for your kind help

Paolo Velcich
industrial designer

*******************************
KORUM DESIGN
Viale Tricesimo 5/6
33100 - UDINE - ITALY
Tel. (+39)0348-2611707
e-mail: pavel@mail.nauta.it
http://www.nauta.com
http://www.polarexpeditions.org
*******************************

asmyth wrote:

> Trolling motors have no gear reduction, hence the high rpm. You can get lots
> of different props for them but they all have something in common, which is
> a very small pitch. That's because they are designed for trolling, and
> although I'm no fisherman, I think its safe to say that... trolling = slow.
> The people who buy a BIG trolling motor use it to move a rally big boat just
> as slowly as they would want to move their small boat -- sort of like buying
> a big diesel which only has 1st gear. So if your sub is a conventional
> design (slow), the standard trolling motor prop should work fine, but if
> you're looking at something streamlined and fast, bolting on an infinite
> number of trolling motors would still not make it go any faster than:
>
> trolling motor rpm * pitch * slip factor  (which I'm told is 3-5 knots)
>
> I've found and ordered a variable pitch prop for industrial fans, with the
> intention of hacking the blades and building a high-speed prop for trolling
> motors. But as you can imagine, my prop diameter will have to be even
> smaller than the original.
>
> -Alec
>
> > -----Original Message-----
> > From: owner-personal_submersibles@psubs.org
> > [mailto:owner-personal_submersibles@psubs.org]On Behalf Of Michael B
> > Holt
> > Sent: Friday, July 16, 1999 5:40 PM
> > To: personal_submersibles@psubs.org
> > Subject: Screw size and speed
> >
> >
> > I've been looking at the pictures of the Hunley.   It had a 30-inch screw
> > that turned at . . . a low speed, I would think.
> >
> > I see other small subs with a pair or more of smaller, higher-RPM screws.
> >
> > It's my understanding that it's fairly easy and inexpensive to buy what
> > seems to be large trolling motors as power.
> >
> > But is there an operational reason small high-speed screws are used?
> >
> > Why can't a large low-speed screw do the same thing?
> >
> >
> >
> > Mike Holt
> > --
> >
> > ___________________________________________________________________
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