RE: [PSUBS-MAILIST] Thruster Design

Cliff,

Look forward to receipt of the files.

I can understand your reasoning in keeping the Kort nozzled thrusters simple.

R/Jay

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Cliff Redus
Sent: Saturday, October 31, 2009 12:28 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Thruster Design

Could you supply purchase information for the book and software? The vendor sent me 5 pdf files with info on the software and cost. To keep from clogging up list, I will send you these files off list.

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

To me the concept here is to come up with low cost but powerful thruster that a psubber could build. The big boys all use the magnetic couplings to isolate the motor in a 1-atm housing and the prop and its support bearings at ambient conditions. This takes out the rotating seal which is a major failure point for thrusters designed for deep operations. If we went with a magnetic coupling, we would have to jettison the Minn Koata housing and design a new one, size the bearings ... This is more work than I want to do. I like the idea of staying with an off the shelf Minn Kota unit minimizing the mods. Yes you would give up some efficiency loss due to viscosity of the compensating oil but in exchange you get a simple build. We can always put a bit more battery power in the boat to compensate for efficiency loss. Beside, you are adding back some efficiency with the Kort nozzle.

Cliff

From: Jay K. Jeffries <bottomgun@mindspring.com>
To: personal_submersibles@psubs.org
Sent: Sat, October 31, 2009 8:16:03 AM
Subject: RE: [PSUBS-MAILIST] Thruster Design

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