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RE: [PSUBS-MAILIST] thrust vs displacement

Pierre,

Solo's displacement will be 3,300 lbs, thrust 148 lbs. As for speed... I've really no idea! I remember toying around with some formula that gave me about 6 knots, but didn't even record it because my confidence level in the result was absolutely nil. As I recall it was based on displacement and ignored the shape of the boat altogether. I would think when you get to that sort of speed the shape would become much more important than things like displacement or wetted surface friction, and Solo ought to be exceptionally clean compared to a traditional manipulator-oriented boat. But frankly I don't know how to do real hydrodynamic modeling of vortexes and such. I chose my motors for their voltage and current draw, and speed is just the dependent variable for me. In any case, due to the density of water speed should be accomplished through shape and not horsepower. If Solo were to do 6 knots on two little trolling motors, I'd feel more than a little pleased. It sounds unrealistic.

One important consideration is that stock trolling motors props are of very fine pitch. What that means is you could put 10 trolling motors on a surfboard and it still would not do more than a couple knots... certainly nowhere near 6 knots. I'm making variable pitch (statically variable) props so I can experiment and find the correct pitch to optimize speed.

Sorry, I'm rambling.

rgds,

Alec

-----Original Message-----
From:	Pierre Poulin [mailto:pipo305@hotmail.com]
Sent:	Sat 2/15/2003 8:56 PM
To:	personal_submersibles@psubs.org
Cc:	
Subject:	Re: [PSUBS-MAILIST] thrust vs displacement


Hi!

My sub have a displacement of 1092 lbs. It will have 2 motors of 28 lbs of 
thrust each (total: 56 lbs). What speed should I expect?

Alec, what is the displacement, total thrust, estimated speed of Solo?

Anybody else have a displacement/thrust/speed ratio that they now?

Thanks a lot!

Pierre Poulin

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