[PSUBS-MAILIST] Group Help Request

[Alan James]

Joe,
I was going to suggest that Marc wade in on this subject, it is one of his fields
of expertise. I believe he has written books on ducted fans etc.
Marc is a very talented guy hidden away in an obscure corner of the Philippines.He may be a helpful
source of information if you want to get this right.
We sure have a multi-talented group here.
Alan



________________________________
 From: Marc de Piolenc <piolenc at archivale.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Monday, October 28, 2013 7:57 PM
Subject: Re: [PSUBS-MAILIST] Group Help Request
 

Quick clarification: a properly contoured Kort nozzle, MARRIED TO A 
MATCHING PROPELLER, will increase static and low-speed thrust. Of course 
it won't increase power, since that comes from your motor. If you just 
put a shroud around your existing prop, you will be disappointed, and a 
shroud that doesn't do the job is overpriced unless it's free! Key 
ingredients for success:

Prop matched to the shroud
Shroud matched to the speed and thrust requirement of the vehicle
Motor matched to the resulting prop

Marc

On 10/28/2013 8:33 AM, Jon Wallace wrote:
>
> 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?
-- 
Archivale catalog: http://www.archivale.com/catalog
Polymath weblog: http://www.archivale.com/weblog
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Translations (BeWords profile): http://www.bewords.com/Marc-dePiolenc
Ducted fans: http://massflow.archivale.com/

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