<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1414376814794_30654" dir="ltr"><span>Marc,</span></div><div id="yui_3_16_0_1_1414376814794_30654" dir="ltr"><span>didn't want to have to Google again.</span></div><div id="yui_3_16_0_1_1414376814794_30654" dir="ltr">Wiki.....<span style="color: rgb(37, 37, 37); font-family: sans-serif; font-size: 14px; line-height: 22.3999996185303px;" class="" id="yui_3_16_0_1_1414376814794_31084"> Classic prop-drives are generally more efficient and economical at low speeds, up to about 20 knots (37 km/h; 23 mph), but as boat speed increases beyond this, the extra </span><a href="http://en.wikipedia.org/wiki/Hull_(watercraft)" title="Hull (watercraft)" style="text-decoration: none; color: rgb(11, 0, 128); font-family: sans-serif; font-size: 14px; line-height: 22.3999996185303px; background-image: none; background-color: rgb(255, 255, 255);" class="">hull</a><span style="color: rgb(37, 37, 37); font-family: sans-serif; font-size: 14px; line-height: 22.3999996185303px;" class=""> resistance generated by struts, </span><a href="http://en.wikipedia.org/wiki/Rudder" title="Rudder" style="text-decoration: none; color: rgb(11, 0, 128); font-family: sans-serif; font-size: 14px; line-height: 22.3999996185303px; background-image: none; background-color: rgb(255, 255, 255);" class="">rudders</a><span style="color: rgb(37, 37, 37); font-family: sans-serif; font-size: 14px; line-height: 22.3999996185303px;" class="" id="yui_3_16_0_1_1414376814794_30668">, shafts (etc.) means waterjets are more efficient in the 20-50 knot range (up to 90 km/h; 60 mph). </span></div><div id="yui_3_16_0_1_1414376814794_30654" dir="ltr"><span style="color: rgb(37, 37, 37); font-family: sans-serif; font-size: 14px; line-height: 22.3999996185303px;" class="">Alan</span></div><div id="yui_3_16_0_1_1414376814794_30654" dir="ltr"><br></div><br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1414376814794_30658"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1414376814794_30657"> <div dir="ltr" id="yui_3_16_0_1_1414376814794_30656"> <hr size="1" id="yui_3_16_0_1_1414376814794_30660"> <font size="2" face="Arial" id="yui_3_16_0_1_1414376814794_30659"> <b><span style="font-weight:bold;">From:</span></b> Marc de Piolenc via Personal_Submersibles <personal_submersibles@psubs.org><br> <b><span style="font-weight: bold;">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Monday, October 27, 2014 1:24 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Water jets<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1414376814794_30669"><br>A blythe generalization that is essentially meaningless.<br clear="none"><br clear="none">As Pazmany used to say: poot some nombers to it!<br clear="none"><br clear="none">Marc<br clear="none"><br clear="none">On 10/27/2014 3:50 AM, Alan James via Personal_Submersibles wrote:<br clear="none"><br clear="none">> Also I did a bit of research on jet propulsion a couple of weeks back<br clear="none">> & what I read said it was inefficient compared to conventional propulsion.<br clear="none">> Alan<br clear="none">><br clear="none">> ------------------------------------------------------------------------<br clear="none">> *From:* Alec Smyth via Personal_Submersibles<br clear="none">> <<a shape="rect" ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br clear="none">> *To:* Personal Submersibles General Discussion<br clear="none">> <<a shape="rect" ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br clear="none">> *Sent:* Monday, October 27, 2014 8:11 AM<br clear="none">> *Subject:* Re: [PSUBS-MAILIST] Water jets<br clear="none">><br clear="none">> I don't think water jets are necessarily inefficient, but if there is<br clear="none">> considerable piping around of the water before it exits through the<br clear="none">> jets, that's what I was referring to. However, even that was not meant<br clear="none">> as criticism, it is just a normal trade-off. It is surely less efficient<br clear="none">> than a conventional direct-coupled prop, but you also get<br clear="none">> entanglement-resistance and maneuverability.<br clear="none">><br clear="none">><br clear="none">><br clear="none">> On Sun, Oct 26, 2014 at 10:11 AM, Marc de Piolenc via<br clear="none">> Personal_Submersibles <<a shape="rect" ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br clear="none">> <mailto:<a shape="rect" ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>> wrote:<br clear="none">><br clear="none">> There is nothing inherently inefficient about waterjets. There are<br clear="none">> commercial fast ferries using them and getting very good thrust per<br clear="none">> horsepower - better than any supercavitating propeller could do at<br clear="none">> the same speed, certainly.<br clear="none">><br clear="none">> Lousy design will of course produce poor results, and jets are much<br clear="none">> less amenable to rule-of-thumb construction than open propellers.<br clear="none">> But whether it is "well known" or not, good design will produce good<br clear="none">> 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">><br clear="none">><br clear="none">> Graham,<br clear="none">> In the world of marine jet drive it is well known that jet drive<br clear="none">> takes two times the horse power to do the same job. Jet drive<br clear="none">> is well suited to a craft that needs a shallow draft. I think<br clear="none">> you will find it very complicated to control and it will be very<br clear="none">> inefficient. I have been down this road, I love the concept but<br clear="none">> abandoned it. If you go forward may I suggest you start with a<br clear="none">> jet drive. It is not a simple part to replicate. The impeller<br clear="none">> tolerances are critical. I have a jet unit on the shelf I could<br clear="none">> donate to your project. The jet is from a jet ski. I would<br clear="none">> consider a single rear motor on a full gimbal.<br clear="none">> Hank ------------------------------__--------------<br clear="none">> On Sun, 10/26/14, Graham Bayliss via Personal_Submersibles<br clear="none">> <<a shape="rect" ymailto="mailto:personal_submersibles@psubs.__org" href="mailto:personal_submersibles@psubs.__org">personal_submersibles@psubs.__org</a><br clear="none">> <mailto:<a shape="rect" ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>> wrote:<br clear="none">><br clear="none">> Subject: [PSUBS-MAILIST] (no subject)<br clear="none">> To: "'Personal Submersibles General Discussion'"<br clear="none">> <<a shape="rect" ymailto="mailto:personal_submersibles@psubs.__org" href="mailto:personal_submersibles@psubs.__org">personal_submersibles@psubs.__org</a><br clear="none">> <mailto:<a shape="rect" ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>><br clear="none">> Received: Sunday, October 26, 2014, 7:39 AM<br clear="none">><br clear="none">> #yiv9417249292<br clear="none">> #yiv9417249292 --<br clear="none">><br clear="none">> _filtered #yiv9417249292 {panose-1:2 4 5 3 5 4 6 3 2 4;}<br clear="none">> _filtered #yiv9417249292 {font-family:Calibri;panose-1:__2 15<br clear="none">> 5 2 2 2 4 3 2 4;}<br clear="none">> #yiv9417249292<br clear="none">> #yiv9417249292 p.yiv9417249292MsoNormal, #yiv9417249292<br clear="none">> li.yiv9417249292MsoNormal, #yiv9417249292<br clear="none">> div.yiv9417249292MsoNormal<br clear="none">> {margin:0cm;margin-bottom:.__0001pt;font-size:12.0pt;}<br clear="none">> #yiv9417249292 a:link, #yiv9417249292<br clear="none">> span.yiv9417249292MsoHyperlink<br clear="none">> {color:blue;text-decoration:__underline;}<br clear="none">> #yiv9417249292 a:visited, #yiv9417249292<br clear="none">> span.__yiv9417249292MsoHyperlinkFollo__wed<br clear="none">> {color:purple;text-decoration:__underline;}<br clear="none">> #yiv9417249292 span.yiv9417249292EmailStyle17<br clear="none">> {color:#1F497D;}<br clear="none">> #yiv9417249292 .yiv9417249292MsoChpDefault<br clear="none">> {}<br clear="none">> _filtered #yiv9417249292 {margin:72.0pt 72.0pt 72.0pt<br clear="none">> 72.0pt;}<br clear="none">> #yiv9417249292 div.yiv9417249292WordSection1<br clear="none">> {}<br clear="none">> #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">> -----Inline Attachment Follows-----<br clear="none">><br clear="none">> _________________________________________________<br clear="none">> Personal_Submersibles mailing list<br clear="none">> <a shape="rect" ymailto="mailto:Personal_Submersibles@psubs.__org" href="mailto:Personal_Submersibles@psubs.__org">Personal_Submersibles@psubs.__org</a><br clear="none">> <mailto:<a shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a>><br clear="none">> <a shape="rect" href="http://www.psubs.org/mailman/__listinfo.cgi/personal___submersibles" target="_blank">http://www.psubs.org/mailman/__listinfo.cgi/personal___submersibles</a><br clear="none">> <<a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a>><br clear="none">><br clear="none">><br 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