[PSUBS-MAILIST] Group Help Request

[Marc de Piolenc]

Aw shucks, Sir...

I forgot to mention that you can probably get a Kort nozzle with 
adequate strength generated using 3-D printing, after designing it in 
some suitable CAD or CAE package. Might be a good deal cheaper than CNC 
machining.

To estimate the thrust on the shroud, just guess at what you're getting 
with an open prop, and figure that the shroud will have to take equal 
thrust.

Best,
Marc de Piolenc
In the tropical paradise known as Mindanao

On 10/28/2013 3:31 PM, Alan James wrote:
> 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?
> --
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-- 
Archivale catalog: http://www.archivale.com/catalog
Polymath weblog: http://www.archivale.com/weblog
Translations (ProZ profile): http://www.proz.com/profile/639380
Translations (BeWords profile): http://www.bewords.com/Marc-dePiolenc
Ducted fans: http://massflow.archivale.com/