<div dir="ltr">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. </div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Oct 26, 2014 at 10:11 AM, Marc de Piolenc via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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.<br>
<br>
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.<br>
<br>
Marc de Piolenc<br>
<br>
On 10/26/2014 8:41 PM, hank pronk via Personal_Submersibles wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Graham,<br>
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.<br>
Hank ------------------------------<u></u>--------------<br>
On Sun, 10/26/14, Graham Bayliss via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<u></u>org</a>> wrote:<br>
<br>
Subject: [PSUBS-MAILIST] (no subject)<br>
To: "'Personal Submersibles General Discussion'" <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<u></u>org</a>><br>
Received: Sunday, October 26, 2014, 7:39 AM<br>
<br>
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#yiv9417249292 Hi I am near the end of my build<br>
of my k350 and have started to look at new designs I am<br>
interested in building a flyer sub and have come up with a<br>
design which will include a vectored motor drive this will<br>
enable my flyer to hover and stop where ever I want. I have<br>
designed a motor unit which will drive a fan type propeller<br>
as an intake this will force water to the rear of the unit<br>
where it is compressed then it is forced into ducting<br>
which will take the water to four nozzles on the side of<br>
the craft. The nozzles are able to turn three hundred and<br>
sixty degrees both side are independent of one another so<br>
rolls will be achievable. The reason for a vectored motor is<br>
you only need one motor source and one power pack this will<br>
ease the maintenance and increase the enjoyment of using<br>
your sub. I am interested in the clubs thought of this kind<br>
of design. Graham<br>
<br>
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