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[PSUBS-MAILIST] KEN MARTINDALE (was Big Motor..)
----- Original Message -----
From: "Michael B. Holt" <mholt@richmond.edu>
To: <personal_submersibles@psubs.org>
Sent: Saturday, September 16, 2000 12:44 PM
Subject: [PSUBS-MAILIST] Re: Big motor for PSUBS...ATTN: K. MARTINDALE...
[ Captain Nemo wrote: "(snip) ...I just look for as much thrust as I can
get, and figure I can always drive slower;...(snip)... But I can see where
more precise information could be desirable.]
Mike Holt wrote: "I'm have the formula from Busby (page 397) in a working
Visial Basic program. If you want it I'll email the EXE to you. It will
duplicate what Busby says in his book, but beyond that I offer no
guarentees."
I'd like that, thanks! And I think it would be cool copyrightwise, because
to my understanding, the reproduction of a small part (one page) of a book
on a limited basis for the non-commercial and educational dissemination of
information is acceptable under "fair use".
I see this Busby copyright issue is generating some heat. I don't want to
step on anyone's rights, and I sure wouldn't want mine stepped on, either.
I'd like to see a copy of this formula; and I think it's legal under the
law. But Phil, if you think it aint Kosher for whatever reason (law,
respect, or whatever), let me know and I'll pass on the idea. I do respect
property.
"(It did tell me that the Nautilus in the book would need 4400 HP to move at
15 knots.)"
Yow! I haven't seen Busby's book, but that must be one BIG Nautilus: maybe
the SSN 571?
"I'm working through a table-load of books about ship design, trying to use
the classic formulae to determine horsepower. So far I've tried four
appraoches, on a spreadsheet, and the accuracy is not good. I have two more
formulae to test. More, as it happens."
Yeah Mike, I see what you're saying. For my purposes, I kind of bypassed
this aspect of it. My sub was an experiment to see if I could design and
build one; and then I went off on an "ornamental tangent" making it look
like the Disney Nautilus. It was never intended for serious travel; if it
worked at all that was good enough for me; and so figuring the exact
performance relative to thrust and horsepower didn't seem necessary at the
time. Plus, in the case of my boat, I think the many extreme variables in
hull geometry would make the calculation process especially complicated and
hard to do accurately. (I mean, it's probably a matter of comparing motive
power output, propellor efficiency, and resultant useable thrust; versus the
size, shape, mass, displacement / buoyancy, and drag coefficients of the
hull; and the unusually ostentatious exterior features of my hull would
probably make that process extremely difficult to determine with any real
accuracy.) So I just got the biggest E-Motor I could find, and tried it.
Turned out to be about the same speed range as most boats this size; no
surprises. Soon I'm going to install more thrust, and that might give me
another knot or so if I'm lucky. And for me and my Nautilus, that'll be
cool. But I've got other projects in mind, too; and for a bigger boat
(where, say, long-range performance is critical, and changing the propulsion
system isn't as simple as pulling an M-K lower end unit out and installing
another one in the same mount) the ability to accurately determine
powerplant performance becomes increasingly important to the design phase.
So yeah, I'd like to know the formula, and would be interested in learning
everything I can about it.
[ The first guy who comes to mind that might be able to answer your question
is KEN MARTINDALE. Whatayathink, Ken?]
"Ken, go for it. I'll take all the expertise that's offered. Mike Holt"
Ken seemed pretty knowledgeable about E-Motor output in terms of voltage,
watts, and horsepower the last couple times we talked about my M-K 4HP
(which probably isn't 4 horse power); so I figure he can help. I'll
re-write the SUBJECT window of this E-Mail so it catches his eye...
Thanks for the input, Mike. Let me know what you come up with regarding
this formula, will you?
VBR,
Pat