[PSUBS-MAILIST] Water jets

Sun Oct 26 20:09:44 EDT 2014

I see what you mean. Pretty paltry ;-]

Seriously, though.

The mere fact of going over 50 knots is ample proof of the value of
'jets. Cavitation is a performance killer, and even supercavitating 
props are going to have a lot of trouble maintaining any net thrust at 
130 knots, though they do manage it with three-step hydroplane boats and 
very alert throttle handlers.

But I've managed to wander pretty far off-topic. Buzzzzzz!

Best,
Marc

On 10/26/2014 10:50 PM, hank pronk via Personal_Submersibles wrote:
>
> Mark, I have coffee with a neat old guy that has a aluminum jet boat
> with 1,000 hp and goes 130 mph that does not sound efficient. :-)
> Hank -------------------------------------------- On Sun, 10/26/14,
> Marc de Piolenc via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Subject: [PSUBS-MAILIST] Water jets To: "Personal Submersibles
> General Discussion" <personal_submersibles at psubs.org> Received:
> Sunday, October 26, 2014, 10:11 AM
>
> 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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>> _filtered
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> 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
>>
>> -----Inline Attachment
> Follows-----
>>
>> _______________________________________________
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>>
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>>
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>
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