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RE: [PSUBS-MAILIST] My PSUB Explorer

Alan,

The problem with stock trolling motor props is they have an extremely fine pitch. So lets say you put 10 trolling motors on a surfboard, it would still only go about 2-3 knots no matter how big the trolling motors were. I'm no fisherman but I understand that's the idea is to move the boat slowly. A small boat wants to troll slowly, and so does a large one. So the large trolling motors will simply move a heavier boat at the same slow speed... visualize a big rig truck with a huge diesel engine but only 1st gear. 

What is needed is a prop with greater pitch, and of course less diameter or the motor is going to exceed its maximum current draw.

After hunting high and low for an appropriate prop, I finally found and purchased one that I think will work, but it is as yet untested since my boat is still under construction. I was able to buy a spare rotor for a pretty fancy industrial fan. Its expensive... the rotor only was about $300. It has 10 removeable blades, of a design that allows the pitch to be statically variable, and from which I plan to make 2 props with 5 blades each. Each blade can be rotated on the hub. You can't rotate them underway, you need tools. But its something I should be able to experiment with to find the right pitch for the boat. I picked the diameter on the basis of a calculation that would have the motor drawing its nominal amps at a pitch of about twice the stock prop. 

Given the expense of these props, I would not encourage anyone to get one until the first guy (me) has found out whether they really work. And of course on many non-streamlined boats, a slow prop is just what you want, and a fast one would not speed you up at all.

rgds,

Alec 

-----Original Message-----
From:	Alan Winick [mailto:subguy33@yahoo.com]
Sent:	Mon 9/23/2002 7:51 PM
To:	personal_submersibles@psubs.org
Cc:	
Subject:	Re: [PSUBS-MAILIST] My PSUB Explorer

Brent:

Thanks for your idea. That would certainly be one
solution, albeit requiring some refitting. Can you
think of a different prop that might fit my current
motors? What about something zany like stacking
another 2-blade prop at right angles for a tandem
effect?

Alan
--- Brent Shaw <drydivenz@yahoo.com> wrote:
> alan
> 
> Just my thoughts
> 
> you could upgrade power by simpling installing 74 lb
> thrust motors and upgrading battery power to 24
> volts
> for main power. The shaft threads are the same so
> motors can be changed over. Motors from
> www.trollingmotorparts.com are around $170 and
> controllers around $150 or maybe not quite than
> easy.
> 
> Brent
> 
> --- Alan Winick <subguy33@yahoo.com> wrote:
> > Brent:
> > 
> > 44 lbs each, port and starboard. Two-blade
> Minn-Kota
> > prop.
> > 
> > Alan
> > 
> > --- Brent Shaw <drydivenz@yahoo.com> wrote:
> > > Hello alan
> > > 
> > > How much thrust are the current motors?
> > > 
> > > Brent - nz
> > > 
> > > --- Alan Winick <subguy33@yahoo.com> wrote:
> > > > Hello!
> > > > 
> > > > My name is Alan Winick and I'm sending a photo
> > of
> > > my
> > > > submarine Explorer to the site. I dreamed of
> > > > building
> > > > a sub since I was 11 (about 35 years ago).I
> > > > completed
> > > > it in 1998 after many years of planning,
> > including
> > > > several visits with George Kittredge and
> intense
> > > > study
> > > > of numerous vehicles. Busby was my bible!
> > > > 
> > > > Explorer is a single place, one-atmosphere
> sub.
> > > It's
> > > > 8' LOA and weighs in at 2300 lbs. Design depth
> > is
> > > > 250'
> > > > and deepest dive to date is 120'. Viewing is
> > > through
> > > > 7
> > > > flat ports in the conning tower and a plexi
> bow
> > > dome
> > > > fabricated for me by Greg Cottrell. Propulsion
> > is
> > > > three air-compensated Minn-Kotas running off
> two
> > > > series 27 marine gel batteries carried inside
> > the
> > > > hull. Cabin atmosphere is air refreshed with
> O2.
> > > An
> > > > O2
> > > > analyzer and CO2 scrubber are carried.
> > > > 
> > > > Although Explorer is active, it spends most of
> > its
> > > > time on exhibit at The Maritime Aquarium in
> > > Norwalk,
> > > > CT. I am deeply involved in science education
> > > using
> > > > the submarine as a teaching tool.
> > > > 
> > > > But on to my question. I need more thrust. I'm
> > > > sure the motors are powerful enough and
> suspect
> > > that
> > > > I
> > > > need props more suited to my application than
> > the
> > > > stock ones supplied with the motor. Maybe more
> > > > pitch,
> > > > blade area? Anybody? Thanks.
> > > > 
> > > > Alan 
> > > > 
> > > > 
> > > > 
> > > >
> > __________________________________________________
> > > > Do you Yahoo!?
> > > > New DSL Internet Access from SBC & Yahoo!
> > > > http://sbc.yahoo.com
> > > 
> > > 
> > >
> __________________________________________________
> > > Do you Yahoo!?
> > > New DSL Internet Access from SBC & Yahoo!
> > > http://sbc.yahoo.com
> > 
> > 
> > __________________________________________________
> > Do you Yahoo!?
> > New DSL Internet Access from SBC & Yahoo!
> > http://sbc.yahoo.com
> 
> 
> __________________________________________________
> Do you Yahoo!?
> New DSL Internet Access from SBC & Yahoo!
> http://sbc.yahoo.com


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