<html><head><meta http-equiv="content-type" content="text/html; charset=us-ascii"></head><body dir="auto"><div></div><div>Hi all,</div><div>tested another 2 props today. Both 2 hp yamaha 3 bladed. One was a</div><div>plastic 7&1/4 x 4, the other aluminium & similar but with rounded ends </div><div>to the blades.</div><div>They both worked much better than the Vetus prop I tried yesterday,</div><div>the plastic prop being the better.</div><div>By comparison the plastic yamaha prop had 60.62 lb. thrust from 1624 W </div><div>while the Vetus had 45 lb. from 1694 W. Quite a difference; 26.79 Watts per</div><div>pound of thrust as apposed to 37.66 for the Vetus. </div><div>David, again it showed to be a lot more economical on power to run the</div><div>motor slowly. At 11 lb of thrust it used 12.9 Watts per pound of thrust and</div><div>rose up to 26.79 Watts per pound of thrust at full power.</div><div>So if the batteries are low, go slow. </div><div>Cheers Alan</div><div><img src="cid:0CC57FBD-8A4B-4CEE-AB1B-DAC5B0C1B5D2" alt="image1.JPG" id="0CC57FBD-8A4B-4CEE-AB1B-DAC5B0C1B5D2"><br></div><div><br>On 6/12/2018, at 7:34 AM, Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div></div><div>Hi David,</div><div>the extension ladder worked but was a bit of an effort pushing it out</div><div>with weight on it. I will grease it before the next prop test.</div><div>As for thrust to watt ratio; I measured this at intervals from 18V to 44V.</div><div>18.2V, 13.2W per lb. of thrust.</div><div>26.8V, 19.5W per lb.</div><div>33.6V, 24.4W per lb.</div><div>38.4V, 29.9W per lb.</div><div>44.6V, 37.6W per lb.</div><div>So definitely a loss of economy as you open the throttle. The Vetus prop</div><div>is designed to work in a tunnel & I didn't have one on it. It will be interesting </div><div>to see how the other props fare in this respect, & if these figures differ much</div><div>when I put a kort nozzle / prop guard on them.</div><div>Alan</div><div><br></div><div><br>On 6/12/2018, at 3:58 AM, David Colombo via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="auto">Hi Alan, l never thought of using a ladder as a test rig. Was the thrust to watt ratio the same base at different speeds?<div dir="auto">David</div></div><br><div class="gmail_quote"><div dir="ltr">On Wed, Dec 5, 2018, 2:03 AM Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Just did the first test on my latest brushless thruster version.<br>
I started with a Vetus bow thruster which is normally housed in a tunnel, but<br>
to simplify things I am testing several different propellors without nozzles first.<br>
I have a 10mm prop shaft & the various off the shelf props need either drilling<br>
out or sleeves made to fit them.<br>
I was getting 38.5 lb. thrust from 1,152 Watts & 45 lb. off 1,694 Watts, which<br>
is comparable with some commercial thrusters but not with others. Some <br>
manufacturers are quoting thrust per Watt figures I find hard to believe.<br>
Will see how the other props work.<br>
Testing came to an end when the automatic pool cleaner (which I had just<br>
moved to the end of the pool) came down & knocked my prop off while I was <br>
jotting down notes. First swim of the summer finding the shaft pin. The prop<br>
was held in place more or less by the force of the prop thrust & a tight fit.<br>
Picture below is from left to right; load cell mounted on the vertical stationary<br>
side of black test jig, motor controller, 48V rectifier with oil compensator on<br>
top, grey load cel display, servo tester to control speed & laptop with Vesc Tool<br>
program displaying data. <br>
The oil compensator is just for the testing, a much smaller & different system<br>
will be on the sub.<br>
Alan<br>
<br>
<br>
<br>
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