RE: [PSUBS-MAILIST] Propane sub

[CWall@swri.edu]

Wade, I agree with you about attention to the prop design, and yes, I
understand what changing one out involves, although I think you have
overestimated the difficulty of the effort, and in any case it's not someting
that would have to be done- that's what the compromise prop would be for. 

I anticipate being able to do the changeout without tools- don't forget, you
don't need to torque down a low horsepower prop if you don't have reverse loads
 to contend with- I can get it done with splines, a castellated nut, and a
safety pin.   And this is purely an optional feature anyway- I anticipate using
 a single prop initially, and all this hassle goes away.

Craig Wall
---------- Original Text ----------

From: "Wade Carson" <wacarson@interchange.ubc.ca>, on 11/10/00 8:34 PM:
To: Incognito2@CTC@SwRI26[<personal_submersibles@psubs.org>]

Craig,
If you are looking to optimize your range, I would suggest that you give
quite a bit of thought to the propeller.  It seems to be a common problem
that people will spend a great deal of time optimizing their drivetrain and
then throw any old hunk of metal on the back.  I'm in the process of
designing a propeller for my sub with an input of 1/2hp (human power) and a
similar size of hull.  I'll let you know how it turns out if you like.  I'd
also question your comment about variable pitch props.  I've seen some
really simple designs for them and it seems that with your operational
characteristics, it would make life much easier and you wouldn't have to
carry around a bunch of different props and a big wrench or get your feet
wet.
By the way, if that's your plan, I hope you never take your sub more than
swimming distance from shore in case you drop a critical piece during the
switch (ie. wrench, two props, a key, and a nut and only two hands)
otherwise you might be glad that Carsten is sending his $20 to the USCG.
And please don't tell me you will have thought of this and have an extra
wrench on board because you'll find that your friend borrowed it to fix his
car (that's if he didn't borrow both of them).  I've switched propellers in
a test tank (no waves there) with full SCUBA and it was tough.  I can't
really picture doing it at sea.

Wade