[PSUBS-MAILIST] Group Help Request

Sun Oct 27 18:20:30 EDT 2013

Alec,

I've gone round and round for the past two weeks in depth on the issues of propulsion and have come full circle back to the trolling motors. I was on hiatus for the discussion mentioned by Vance ref contact with the manufacturer as I would have remembered that.

So, I'm with you on the prop and nozzle. While the 101's may indeed have plenty of guts for the job as is, the Kort data shows a 30% improvement in Bollard thrust at low speeds for any given prop diameter. That and the added benefit of protecting the prop, are significant enough reasons to forge ahead. This is actually good news, less work by not mucking around with the guts of the motor.

You guys are the builders with recent hands on, I'm behind in the trial and error business because I cant get started tinkering yet. But as you well know, I developed CAD capability for this purpose only, so time to put it to real use. Where I need help is deciding on materials and manufacturing processes. I can give you guys the cutting files needed to whittle a Kort out of a block of solid titanium, but that would not be practical. That's my limitation and where hands on experience counts.

Now these nozzles are reverse foils with coordinates in percent of length. I can generate a NACA 4415 on my airfoil generator and transfer that to the model.  I can give us accurate 3d models and eventually CNC cutting files for whatever the group wants on these Minn Kotas, nozzles and attachment hardware. I can do both Nozzles, Marin 19A, and or 37, with the latter being optimized bi-directionally.

Finding something off the shelf would be ideal, but I suspect given the nature of the business and the quote I recieved it would likely prove problematic.

You need a new square tip prop to optimize the duct. I've had custom props made for my boat in the past, so that should not prove insurmountable. I should be able to do the prop as well. 

Can we post pictures on this forum?, I forget. It would be helpful to point things out. If I could post pictures of the various exploded diagrams, I can point to where I want dimensions with red arrows. Eventually, I'll start a web-page.

So for now, I need some detail on the shaft and prop as is., what have you done with that washer and where it is in the drive, as well as any other modifications.

I think this is a decent group effort project, and one that can pay dividends in the end.

Joe

________________________________
From: Private <alecsmyth at gmail.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Sunday, October 27, 2013 2:29 PM
Subject: Re: [PSUBS-MAILIST] Group Help Request

Hi Joe,

Thanks for doing this. I have a Minnkota 101 here that I can measure for you, but I also have some suggestions for your consideration.

Oil or air compensation are both easy and trouble free, so I really don't see much value-add in the magnetic coupling. Or in a hard case. Ditto reverse, my trolling motor thrusters with 13 years on them have yet to wear out the reverse washer, and it's not like I don't use reverse.

Where I do see real room for improvement is with props and nozzles. The stock props are very short pitched, so if you put several 101s on a small sub for main propulsion, I suspect you would not get the cruising speed that their combined horse power would otherwise achieve. In other words, it would be like putting a big engine in your car but only having first gear.

Emile shared with me that the nice kort on his stern thruster is off a diving scooter. I researched those briefly and indeed they're in the ballpark of trolling motor prop diameters, and some appear to be true korts. Since kort nozzles are hard to make, ID'ing one that's a good match would be really useful. While looking at scooters, I noticed some have variable pitch props. By variable I mean adjustable with tools, not adjustable underway. That could prove a big performance booster for our application.

In summary, I'd encourage a focus on the prop and nozzle, as I've found the standard seals and reverse to be perfectly satisfactory. My trolling motors leaked for the first time in 2012, after 12 years of use. I've left the oil in them for years at a time. When I finally serviced them last year, there were cheap rebuild kits readily available. 

Do you need the measurements of the inside bits too? 

Best,

Alec

On Oct 27, 2013, at 8:29 AM, Joe Perkel <josephperkel at yahoo.com> wrote:

All Psubber Alert.
>
>A handful of members in conversation off list are coming to the conclusion that perhaps a best solution to the thruster issues discussed, is to improve on what has been demonstrated to already be viable. That is Minn Kotas as demonstrated by Snoopy, Idabel, et al. Parts are readily available and inexpensive. Case in point here,.. http://www.northlandmarine.com/MinnKotaQuickRef.htm
>
>Hank has graciously offered his efforts in modifying several he already has on hand, and I am willing to put in many hours of CAD work to come up with working drawings, with an eye on this armature in particular,.. http://www.northlandmarine.com/MinnKotaArmatureAssy92-100-216.htm
>
>The goal would be to add a mag coupling, Kort nozzle, and true reversibility to a package that is compact, (4" dia) and field serviceable / replaceable. The end product result would be open source to the PSUB community.
>
>Immediate problem that needs a solution.
>
>I need a lot of information and detail in order to proceed. Particularly what I need is dimensioned section drawings of appropriately sized models. Unfortunately, Minn Kota does not make this information readily available as demonstrated here,... http://www.minnkotamotors.com/service/ascs.aspx
>
>We need help accessing this information otherwise the effort is hobbled from the start. If anyone can help in this regard it would help tremendously. 
>
>Joe
>
>
>Sent from Yahoo! Mail for iPad 
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