Re: [PSUBS-MAILIST] Thruster Design

That would mean building the thrusters from scratch, or rebuilding the back end of the M-K 101s. Either way, it will be more expensive to buy and build, especially for those without a lathe. That said, I'd MUCH prefer dry thrusters, and aluminum doesn't cost all that much in small quantities. The only real question will be which motor to use. Us low voltage types won't get much benefit from fist sized 1 hp motors that run at 240 Volts. Considering the power head price on the minn-kotas, maybe a stainless cup could be designed that would support the motor, the interior coupling and the chassis O-ring all at once. I do like the idea of keeping them dry. They run better in air.

Cliff,

Great job and interesting paper! Could you supply purchase information for the book and software? A literature search brought up MIT’s open source coursewares offered over the web for their course Hydrofoils and Propellers. Included in those materials is a variety of programs written for Mathcad and MatLab, one of which is specific to the problem at hand. Will play with a bit if I get a chance and see what information it provides.

Will you be considering a magnetically coupled prop for this solution? Would negate the need for compensating oil or air pressure.

R/Jay

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Cliff Redus
Sent: Saturday, October 31, 2009 8:37 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Thruster Design

Vance/Frank

I will tag with you guys on this when I get farther along. The paper references a book "The Wagenigen propeller series, MARIN Publication 92-001, May 1992. I sent and email to the MARIN company to see if they would end me a PDF. They sent a note back that the report is really a book and it comes with software they use for sizing ducted props. I have ordered the book and software. After I have had a chance to digest, we can discuss a game plan. My guess is we would size the ducted prop for the max power the Minn Kotta can put up. Per the paper, we will need to decide if we want a ducted prop optimized for forward thrust or optimized for equal thrust for forward and reverse. I would vote for optimize for forward thrust. I am going to need to do a tear down of a Minn Kota so that I can measure parts so that I can create a 3-D model of the 101 in Inventor. Then we will need to run the software to select the prop. We would then need to decide on how the fabricate the nozzle and mounting of the motor and nozzle. Frank has some thoughts on how to fabricate nozzle using FRP layup on a SS ring. We have a lot of options in this. Another approach would be to use a CNC machine and fabricate off the Inventor 3-D file with T6-6061 aluminum and anodize. This might be a bit pricey but we would have high tolerance of the shape of the nozzle which would improve our bench testing of thrust. I would also like to come up with a common off the shelf wet connector and whip that we could use. We also need to see what kind of oil has worked best for minimizing friction in the housing. I think Peter and Carsten have some expericne with this.

Latter Cliff

Great works are performed not by strength but by perseverance.
Samuel Johnson