[PSUBS-MAILIST] Water jets

Sun Oct 26 16:14:26 EDT 2014

Hi Hank,Graham wanted to rotate his jets separately so he couldget a roll / flying type motion. So he would need to havetwo separate intakes that rotated identically to the vertical outletsto acheive that without getting the forward motion & addedinefficiencies. I wonder what sort of roll you could get with aconventional set up.You must have tried that Hank / Alec. Do you get much of a tiltwhen you have your vertical thrusters working in differentdirections?Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Monday, October 27, 2014 8:57 AM
 Subject: Re: [PSUBS-MAILIST] Water jets

Alan,
I did not think of that, but your right.  You could put a shroud over the inlet that is inline with the discharge so then the pump is pulling and pushing.
Hank--------------------------------------------
On Sun, 10/26/14, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] Water jets
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Received: Sunday, October 26, 2014, 3:50 PM

 One
 problem I can see is that if you have your Jet
 suckingwater in
 from the front & you pivot your outlets to get
 verticalmotion,
 then you will get forward movement from the suction
 ofthe inlet
 at a similar rate.Also I
 did a bit of research on jet propulsion a couple of
 weeks back&
 what I read said it was inefficient compared to conventional
 propulsion.Alan
        From: Alec Smyth via
 Personal_Submersibles
 <personal_submersibles at psubs.org>
  To: Personal
 Submersibles General Discussion
 <personal_submersibles at psubs.org> 
  Sent: Monday, October
 27, 2014 8:11 AM
  Subject: Re:
 [PSUBS-MAILIST] Water jets

 I
 don't think water jets are necessarily inefficient, but
 if there is considerable piping around of the water before
 it exits through the jets, that's what I was referring
 to. However, even that was not meant as criticism, it is
 just a normal trade-off. It is surely less efficient than a
 conventional direct-coupled prop, but you also get
 entanglement-resistance and maneuverability.  

 On Sun, Oct 26, 2014 at
 10:11 AM, Marc de Piolenc via Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 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

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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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