<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div dir="ltr" id="yui_3_16_0_1_1414350070247_10750"><span id="yui_3_16_0_1_1414350070247_10749">One problem I can see is that if you have your Jet sucking</span></div><div dir="ltr" id="yui_3_16_0_1_1414350070247_10752"><span id="yui_3_16_0_1_1414350070247_10751">water in from the front & you pivot your outlets to get vertical</span></div><div dir="ltr" id="yui_3_16_0_1_1414350070247_10754"><span id="yui_3_16_0_1_1414350070247_10753">motion, then you will get forward movement from the suction of</span></div><div dir="ltr" id="yui_3_16_0_1_1414350070247_10754"><span id="yui_3_16_0_1_1414350070247_10810">the inlet at a similar rate.</span></div><div dir="ltr" id="yui_3_16_0_1_1414350070247_10754"><span id="yui_3_16_0_1_1414350070247_10856">Also I did a bit of </span>research on jet propulsion a couple of weeks back</div><div dir="ltr" id="yui_3_16_0_1_1414350070247_10754">& what I read said it was inefficient compared to conventional propulsion.</div><div dir="ltr" id="yui_3_16_0_1_1414350070247_10754">Alan</div><br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1414350070247_10840"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1414350070247_10839"> <div dir="ltr" id="yui_3_16_0_1_1414350070247_10838"> <hr size="1"> <font size="2" face="Arial" id="yui_3_16_0_1_1414350070247_10837"> <b id="yui_3_16_0_1_1414350070247_10855"><span style="font-weight:bold;" id="yui_3_16_0_1_1414350070247_10854">From:</span></b> Alec Smyth via Personal_Submersibles <personal_submersibles@psubs.org><br> <b id="yui_3_16_0_1_1414350070247_10853"><span style="font-weight: bold;" id="yui_3_16_0_1_1414350070247_10852">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br> <b id="yui_3_16_0_1_1414350070247_10842"><span style="font-weight: bold;" id="yui_3_16_0_1_1414350070247_10841">Sent:</span></b> Monday, October 27, 2014 8:11 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Water jets<br> </font> </div> <div class="y_msg_container"><br><div id="yiv1468909789"><div><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="yiv1468909789gmail_extra"><br clear="none"><div class="qtdSeparateBR"><br><br></div><div class="yiv1468909789yqt8964487987" id="yiv1468909789yqtfd35260"><div class="yiv1468909789gmail_quote">On Sun, Oct 26, 2014 at 10:11 AM, Marc de Piolenc via Personal_Submersibles <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote class="yiv1468909789gmail_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 clear="none">
<br clear="none">
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 clear="none">
<br clear="none">
Marc de Piolenc<br clear="none">
<br clear="none">
On 10/26/2014 8:41 PM, hank pronk via Personal_Submersibles wrote:<br clear="none">
<blockquote class="yiv1468909789gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br clear="none">
Graham,<br clear="none">
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 clear="none">
Hank ------------------------------<u></u>--------------<br clear="none">
On Sun, 10/26/14, Graham Bayliss via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.<u></u>org</a>> wrote:<br clear="none">
<br clear="none">
Subject: [PSUBS-MAILIST] (no subject)<br clear="none">
To: "'Personal Submersibles General Discussion'" <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.<u></u>org</a>><br clear="none">
Received: Sunday, October 26, 2014, 7:39 AM<br clear="none">
<br clear="none">
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#yiv9417249292 Hi I am near the end of my build<br clear="none">
of my k350 and have started to look at new designs I am<br clear="none">
interested in building a flyer sub and have come up with a<br clear="none">
design which will include a vectored motor drive this will<br clear="none">
enable my flyer to hover and stop where ever I want. I have<br clear="none">
designed a motor unit which will drive a fan type propeller<br clear="none">
as an intake this will force water to the rear of the unit<br clear="none">
where it is compressed then it is forced into ducting<br clear="none">
which will take the water to four nozzles on the side of<br clear="none">
the craft. The nozzles are able to turn three hundred and<br clear="none">
sixty degrees both side are independent of one another so<br clear="none">
rolls will be achievable. The reason for a vectored motor is<br clear="none">
you only need one motor source and one power pack this will<br clear="none">
ease the maintenance and increase the enjoyment of using<br clear="none">
your sub. I am interested in the clubs thought of this kind<br clear="none">
of design. Graham<br clear="none">
<br clear="none">
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