----- Original Message -----
Sent: Thursday, February 17, 2005 8:22
AM
Subject: Re: [PSUBS-MAILIST] Dan, you got
me wondering about my prop.
Bill,
What you have will probably work fine. A
trolling motor's design isn't that much different from a sub thruster.
They both go relatively slow in the water. Where you really see the difference
in props is in a power boat prop. Something that cruses on the
water.
Just go on with what you have. I'm sure Minnkota
has the prop and motor matched quite well. You may find that the
trolling motor may run at a little higher amperage pushing a more resistant
sub then it would on a surface craft. But, this is off set by the fact
that your probably going to use the thruster far less then it was designed for
and seldom at full thrust giving it time to dissipate any extra generated
heat.
What I would do is, when your doing you first wet
test of your sub, have an amp meter to monitor the current draw of the
thruster. If your over the rated amperage you can either reduce some of
your props diameter, or take some off the trailing edges to remove it's
surface area or flatten it out to reduce it's bite in the water. Be
careful if you trying to change the pitch so you don't crack it. Also be
careful when remove material so the prop stays balanced.
My uneducated guess is, Minnkota did the work for
you. You'll probably be fine with it as it is.
Dan H.
----- Original Message -----
Sent: Thursday, February 17, 2005 2:16
AM
Subject: Re: [PSUBS-MAILIST] Dan, you
got me wondering about my prop.
Hi Dan.
You wrote below......
"The surface craft needs a faster prop speed just to travel through the
water and additional
speed to produce thrust. The slower moving sub needs
less prop speed to
screw through the water and additional speed to
produce thrust.
By now I'm sure most of you are thinking, but the surface
boat uses a
different pitch prop. True! A faster moving boat
uses a prop that has a
long lead, more pitch. For one turn of the
prop it is designed to screw
farther through the water then a slower
moving boats prop. This is taken
into consideration with propelling
a sub. Any slow moving craft has a
flatter prop then a fast moving
craft. If the pitch of the prop were all
the same the fast boat
wound need a zillion RPM and a subs props would be
turning extremely
slow."
You got me to thinking. I have a two man wetsub
and a 74lb thrust minnkota motor with the 11 inch Minnkota weedless wedge
prop.
Is that prop going to be ok for use on my sub
since it is designed for being a surface craft trolling motor? Do I need a
prop
with a different pitch?
When you were explaining about how a surface
craft needs a different prop from a sub it got me to thinking if I might
need
to get another prop for my sub.
Kindest Regards,
Bill
Akins.