<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div><span>Mark,</span></div><div style="color: rgb(0, 0, 0); font-size: 12px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>You just made my point. lower bollard pull comes from a lack of power and likely rpm. Sure you can design a sub to have equal bollard pull with jets, but it will have a much larger energy draw. Big energy draw is bad :-) Also eyeball engineering can work well when backed up with real world experience.</span></div><div style="color: rgb(0, 0, 0); font-size: 12px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>Hank</span></div> <div
class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12px;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 16px;"> <div dir="ltr"> <font size="2" face="Arial"> On Tuesday, October 28, 2014 5:44 AM, Marc de Piolenc via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br> </font> </div> <br><br> <div class="y_msg_container">I'll say it again: eyeball engineering doesn't work with ducted <br>propulsors. The Navy's river patrol boats used in Vietnam had water jet <br>units built, so I am told, by the Jacuzzi firm, makers of whirlpool <br>baths! Somebody there must have understood propulsion, though, because <br>the units worked well.<br><br>A ducted unit optimized for low speed and static operation will achieve <br>a
mass flow equivalent to a (much) larger open propeller, and will get <br>better static thrust. Lower bollard pull for the same hp just means the <br>ducted unit was not correctly designed for the application.<br><br>Best,<br>Marc<br>Ducted fans: <a href="http://massflow.archivale.com/" target="_blank">http://massflow.archivale.com/</a><br><br>On 10/27/2014 1:35 PM, Phil Nuytten via Personal_Submersibles wrote:<br>> A quick weigh-n on water jets. Years ago (many) I talked to the pilots<br>> of the Cousteau “Puce de Mer” (Sea Fleas) And the famous ‘SP 350, Diving<br>> Saucer’ about the efficiency of their water jet propulsion units. They<br>> confirmed that they were very ‘weak’ in a comedic way . . .they had a<br>> phrase in French which made the two Sea Flea pilots break out laughing –<br>> my trusty translator also laughed and then tried to keep a straight face<br>> as he said “they are saying that the things that
you ask about are not<br>> strong enough to “ pull a penis out of a bucket of lard”!<br>> Some years later we tried a high volume water pump coupled with a duct<br>> engineered to work most efficiently with the pump. We hooked it up to a<br>> fixed pad eye inside our large test tank and used a spring scale to<br>> determine the bollard pull. Our froggie friends were quite right: using<br>> a conventional prop powered with exactly the same horsepower gave a<br>> large increase in bollard pull.<br>> *From:* Alan James via Personal_Submersibles<br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>> *Sent:* Sunday, October 26, 2014 9:30 PM<br>> *To:* Personal Submersibles General Discussion<br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org"
href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>> *Subject:* Re: [PSUBS-MAILIST] Water jets<br>> Marc,<br>> didn't want to have to Google again.<br>> Wiki.....Classic prop-drives are generally more efficient and economical<br>> at low speeds, up to about 20 knots (37 km/h; 23 mph), but as boat speed<br>> increases beyond this, the extra hull<br>> <<a href="http://en.wikipedia.org/wiki/Hull_" target="_blank">http://en.wikipedia.org/wiki/Hull_</a>(watercraft)>resistance generated by<br>> struts, rudders <<a href="http://en.wikipedia.org/wiki/Rudder" target="_blank">http://en.wikipedia.org/wiki/Rudder</a>>, shafts (etc.)<br>> means waterjets are more efficient in the 20-50 knot range (up to 90<br>> km/h; 60 mph).<br>> Alan<br>> ------------------------------------------------------------------------<br>> *From:* Marc de Piolenc via Personal_Submersibles<br>>
<<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>> *To:* Personal Submersibles General Discussion<br>> <<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>> *Sent:* Monday, October 27, 2014 1:24 PM<br>> *Subject:* Re: [PSUBS-MAILIST] Water jets<br>><br>> A blythe generalization that is essentially meaningless.<br>><br>> As Pazmany used to say: poot some nombers to it!<br>><br>> Marc<br>><br>> On 10/27/2014 3:50 AM, Alan James via Personal_Submersibles wrote:<br>><br>> > Also I did a bit of research on jet propulsion a couple of weeks back<br>> > & what I read said it was inefficient compared to conventional<br>> propulsion.<br>> > Alan<br>> ><br>> >
------------------------------------------------------------------------<br>> > *From:* Alec Smyth via Personal_Submersibles<br>> > <<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>><br>> > *To:* Personal Submersibles General Discussion<br>> > <<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>><br>> > *Sent:* Monday, October 27, 2014 8:11 AM<br>> > *Subject:* Re: [PSUBS-MAILIST] Water
jets<br>> ><br>> > I don't think water jets are necessarily inefficient, but if there is<br>> > considerable piping around of the water before it exits through the<br>> > jets, that's what I was referring to. However, even that was not meant<br>> > as criticism, it is just a normal trade-off. It is surely less efficient<br>> > than a conventional direct-coupled prop, but you also get<br>> > entanglement-resistance and maneuverability.<br>> ><br>> ><br>> ><br>> > On Sun, Oct 26, 2014 at 10:11 AM, Marc de Piolenc via<br>> > Personal_Submersibles <<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org"
href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br>> > <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>>> wrote:<br>> ><br>> > There is nothing inherently inefficient about waterjets. There are<br>> > commercial fast ferries using them and getting very good thrust per<br>> > horsepower - better than any supercavitating propeller could do at<br>> > the same speed, certainly.<br>> ><br>> > Lousy design will of course produce poor results, and jets are much<br>> > less amenable to rule-of-thumb
construction than open propellers.<br>> > But whether it is "well known" or not, good design will produce good<br>> > results.<br>> ><br>> > Marc de Piolenc<br>> ><br>> > On 10/26/2014 8:41 PM, hank pronk via Personal_Submersibles wrote:<br>> ><br>> ><br>> > Graham,<br>> > In the world of marine jet drive it is well known that jet drive<br>> > takes two times the horse power to do the same job. Jet drive<br>> > is well suited to a craft that needs a shallow draft. I think<br>> > you will find it very complicated to control and it will be very<br>> > inefficient. I
have been down this road, I love the concept but<br>> > abandoned it. If you go forward may I suggest you start with a<br>> > jet drive. It is not a simple part to replicate. The impeller<br>> > tolerances are critical. I have a jet unit on the shelf I could<br>> > donate to your project. The jet is from a jet ski. I would<br>> > consider a single rear motor on a full gimbal.<br>> > Hank ------------------------------__--------------<br>> > On Sun, 10/26/14, Graham Bayliss via Personal_Submersibles<br>> > <<a ymailto="mailto:personal_submersibles@psubs.__org"
href="mailto:personal_submersibles@psubs.__org">personal_submersibles@psubs.__org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.__org" href="mailto:personal_submersibles@psubs.__org">personal_submersibles@psubs.__org</a>><br>> > <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>>> wrote:<br>> ><br>> > Subject: [PSUBS-MAILIST] (no subject)<br>> > To: "'Personal Submersibles General Discussion'"<br>> > <<a ymailto="mailto:personal_submersibles@psubs.__org" href="mailto:personal_submersibles@psubs.__org">personal_submersibles@psubs.__org</a><br>> <mailto:<a
ymailto="mailto:personal_submersibles@psubs.__org" href="mailto:personal_submersibles@psubs.__org">personal_submersibles@psubs.__org</a>><br>> > <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a><br>> <mailto:<a ymailto="mailto:personal_submersibles@psubs.org" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>>><br>> > Received: Sunday, October 26, 2014, 7:39 AM<br>> ><br>> > #yiv9417249292<br>> > #yiv9417249292 --<br>> ><br>> > _filtered #yiv9417249292 {panose-1:2 4 5 3 5 4 6 3 2 4;}<br>> > _filtered #yiv9417249292 {font-family:Calibri;panose-1:__2 15<br>> > 5 2 2 2 4 3 2 4;}<br>> > #yiv9417249292<br>> > #yiv9417249292 p.yiv9417249292MsoNormal,
#yiv9417249292<br>> > li.yiv9417249292MsoNormal, #yiv9417249292<br>> > div.yiv9417249292MsoNormal<br>> > {margin:0cm;margin-bottom:.__0001pt;font-size:12.0pt;}<br>> > #yiv9417249292 a:link, #yiv9417249292<br>> > span.yiv9417249292MsoHyperlink<br>> > {color:blue;text-decoration:__underline;}<br>> > #yiv9417249292 a:visited, #yiv9417249292<br>> > span.__yiv9417249292MsoHyperlinkFollo__wed<br>> > {color:purple;text-decoration:__underline;}<br>> > #yiv9417249292 span.yiv9417249292EmailStyle17<br>> > {color:#1F497D;}<br>> > #yiv9417249292 .yiv9417249292MsoChpDefault<br>> > {}<br>> > _filtered #yiv9417249292 {margin:72.0pt 72.0pt 72.0pt<br>> > 72.0pt;}<br>> > #yiv9417249292 div.yiv9417249292WordSection1<br>> > {}<br>> > #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><br><br>-- <br>Archivale catalog: <a href="http://www.archivale.com/catalog" target="_blank">http://www.archivale.com/catalog</a><br>Polymath weblog: <a href="http://www.archivale.com/weblog" target="_blank">http://www.archivale.com/weblog</a><br>Translations (ProZ profile): <a href="http://www.proz.com/profile/639380" target="_blank">http://www.proz.com/profile/639380</a><br>Translations (BeWords profile): <a href="http://www.bewords.com/Marc-dePiolenc" target="_blank">http://www.bewords.com/Marc-dePiolenc</a><br><br>_______________________________________________<br>Personal_Submersibles mailing list<br><a ymailto="mailto:Personal_Submersibles@psubs.org"
href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br><br></div> </div> </div> </div> </div></body></html>