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Horsepower (was: History)
On Tue, 20 Jul 1999 09:45:58 -0400 "Allan Gaines" writes:
> Would it have required THAT much?
As I said in a subsequent post, the hull would require about 30 HP to
move it at hull speed. If it were a surface vessel.
>Judging by the tv movie
>"HUNLEY" on TNT, the sub was propelled by eight men turning
>hand cranks using upper body strength. How much power can
>one man generate? Seems like I've heard 0.75 of one horse-
>power maximum. [This is from memory, so it may be wrong.]
>That times 8 would be 6 horsepower. And according to what
>I've read, the sub could move at about 4 knot.
You're right. I've spend my nose is design books too long.
On page 397 of Busby, there's a formula for approximating
SHP to drive a submerged body. I don't have the capability
to write it out correctly, but:
SHP = 0.005 * speed (knots) cubed * displacement (long tons) to the
2/3rds
Staggering through it for the first time since about 1980, I figure the
Hunley would take a bit over 1 HP to move it at 4 knots. I've not done
anything beyond adding and subtracting on the TI-36X since . . . well,
it's been a while.
I'd think 1 HP would be sustainable from six men in those conditions, but
only for a short time. Any bike riders out there who can comment?
Back in about '76, I wrote this formula in CBASIC and sent it to Frank
Busby; i never heard from him. If I had a programming language here,
It would be fun and useful to build a program that would do all the
math in Busby's book.
It's amazing how much of that I lost by not using it.
Mike Holt
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