[PSUBS-MAILIST] Group Help Request

Mon Oct 28 01:04:30 EDT 2013

Joe,
I think it would be really difficult to fabricate a Kort nozzle on a CNC machine. 
The nozzle portion could be mass produced by making the first by hand, then casting a silicone mold
around it & pouring a glass reinforced resin in to this. The fins & motor attachment method could be also 
made like this & attached to the kort nozzle. 
Alan

________________________________
 From: Joe Perkel <josephperkel at yahoo.com>
To: "personal_submersibles at psubs.org" <personal_submersibles at psubs.org> 
Sent: Monday, October 28, 2013 2:33 PM
Subject: Re: [PSUBS-MAILIST] Group Help Request

Jon,

The short answer is I dont know. But look at that Dutchman and his simplistic ingenuity. Thats what Im hoping for out of this group as far as materials and processes. Im ready to draw up whatever the result. Consider that there are intrepid builders of all sorts of things worldwide. Hovercrafters build large scale ducts for thier craft as a example. I'll take a look there tomorrow.

How about half a kort??? A plug of some kind (construction grade foam perhaps?) to build up a FRP shell over then mate two halves Revelle model style??? Can this shape be hot wired?? What to use as a guide? I have ideas and questions, but I need the shop wizards of the world to come up with the process.

As for The other things, Im ready and willing. I like the thruster because with my family and work time constraints, its not too much to chew on. I can commit to small projects for now, bigger later as time goes on.

What would you like to see done apart from the thrusters?

Joe 

From: Jon Wallace <jonw at psubs.org>; 
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>; 
Subject: Re: [PSUBS-MAILIST] Group Help Request 
Sent: Mon, Oct 28, 2013 12:33:12 AM 

What is the cost of having a true Kort nozzle machined by a CNC?  I think a 30% improvement in thrust for $30 would be great but I suspect machining a Kort is going to equate to many hundreds of dollars, if not reaching beyond a thousand.  When I look at the Snoopy underwater videos it is difficult to imagine a kort nozzle really making any difference in the operational experience given that the motors are operating very slowly and pushing Snoopy around at about 2 knots (estimated).  The props are designed for power, but that's what we want underwater.  True, a kort nozzle would increase that power but what is the return on the cost?  In other words, on a road with a speed limit of 30mph and no passing zones it doesn't matter whether you have a 1.6 liter or 5.4 liter engine under the hood does it?

Like Vance, I
 don't
 want to rain on the parade and I do "get it" that the challenge of coming up with a "home-built" alternative can be rewarding.  I just think that production cost will be the determining factor on practical use.  Like going from T-Rex back to minn-kota, I can't help but wonder if the ultimate conclusion will turn out to be that the stock minn-kota's are good enough for 99.99% of our applications.

I can think of many things that your CAD experience could offer to the group if you are interested in providing some designs.  For example the K350 plan modifications that have been talked about by a few people.  We could really use help in that area.  

Jon

On 10/27/2013 6:20 PM, Joe Perkel wrote:

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
>
>
>

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