[PSUBS-MAILIST] Water jets

[Marc de Piolenc via Personal_Submersibles]

There is nothing inherently inefficient about waterjets. There are 
commercial fast ferries using them and getting very good thrust per 
horsepower - better than any supercavitating propeller could do at the 
same speed, certainly.

Lousy design will of course produce poor results, and jets are much less 
amenable to rule-of-thumb construction than open propellers. But whether 
it is "well known" or not, good design will produce good results.

Marc de Piolenc

On 10/26/2014 8:41 PM, hank pronk via Personal_Submersibles wrote:
>
> Graham,
> In the world of marine jet drive it is well known that jet drive takes two times the horse power to do the same job.  Jet drive is well suited to a craft that needs a shallow draft.  I think you will find it very complicated to control and it will be very inefficient. I have been down this road, I love the concept but abandoned it.  If you go forward may I suggest you start with a jet drive.  It is not a simple part to replicate.  The impeller tolerances are critical.  I have a jet unit on the shelf I could donate to your project.  The jet is from a jet ski. I would consider a single rear motor on a full gimbal.
> Hank --------------------------------------------
> On Sun, 10/26/14, Graham Bayliss via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>   Subject: [PSUBS-MAILIST] (no subject)
>   To: "'Personal Submersibles General Discussion'" <personal_submersibles at psubs.org>
>   Received: Sunday, October 26, 2014, 7:39 AM
>
>   #yiv9417249292
>   #yiv9417249292 --
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>   #yiv9417249292  Hi   I am near the end of my build
>   of my k350 and have started to look at new designs I am
>   interested in building a flyer sub and have come up with a
>   design which will include a vectored motor drive this will
>   enable my flyer to hover and stop where ever I want. I have
>   designed a motor unit which will drive a fan type propeller
>   as an intake this will force water to the rear of the unit
>    where it is compressed  then it is forced into ducting
>   which will take  the water to four nozzles on the side of
>   the craft. The nozzles are able to turn three hundred and
>   sixty degrees  both side are independent of one another so
>   rolls will be achievable. The reason for a vectored motor is
>   you only need one motor source and one power pack this will
>   ease the maintenance and increase the enjoyment of using
>   your sub. I am interested in the clubs thought of this kind
>   of design.  Graham
>
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