<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_1418600242974_5747" dir="ltr"><span id="yui_3_16_0_1_1418600242974_6214">Hi Hank,</span></div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr"><span id="yui_3_16_0_1_1418600242974_6216">I guess you would be getting the same thrust in both directions, but</span></div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr"><span id="yui_3_16_0_1_1418600242974_6077">you would be doubling the pitch of the propeller by doubling up, & there may</span></div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr"><span id="yui_3_16_0_1_1418600242974_6213">be a lot of turbulance between the propellers.</span></div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">There are propeller calculators that take a number of input variables like hp, revs, boat size,</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">intended speed, diameter of the propeller & pitch. You leave one input out & it calculates</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">that for you. You could call the two propellers one (add the two pitches together) & see what </div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">diameter it calculates for you at a given pitch & play around till you get the most efficient</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">diameter / pitch combination; then use the diameter but halve the pitch.</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">I don't think I made a lot of sense, but if you go down that path I will explain a bit better.</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">However given that submarines operate better with bigger diameter, lower pitch propellers</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">it probably isn't a good idea going to two smaller higher pitched propellers.</div><div id="yui_3_16_0_1_1418600242974_5747" dir="ltr">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_1418600242974_5750"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1418600242974_5749"> <div dir="ltr" id="yui_3_16_0_1_1418600242974_5748"> <hr size="1" id="yui_3_16_0_1_1418600242974_6076"> <font size="2" face="Arial" id="yui_3_16_0_1_1418600242974_5751"> <b id="yui_3_16_0_1_1418600242974_7216"><span style="font-weight:bold;" id="yui_3_16_0_1_1418600242974_7215">From:</span></b> hank pronk via Personal_Submersibles <personal_submersibles@psubs.org><br> <b><span style="font-weight: bold;">To:</span></b> personal_submersibles@psubs.org <br> <b><span style="font-weight: bold;">Sent:</span></b> Monday, December 15, 2014 10:38 AM<br> <b id="yui_3_16_0_1_1418600242974_8349"><span style="font-weight: bold;" id="yui_3_16_0_1_1418600242974_8348">Subject:</span></b> [PSUBS-MAILIST] props<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1418600242974_5760"><br>Hi All,<br>If I build a thruster with an extra long shaft, then put two props on back to back, one prop reversed. Will the thruster perform equally in both directions?<br>Hank<br>_______________________________________________<br>Personal_Submersibles mailing list<br><a ymailto="mailto:Personal_Submersibles@psubs.org" href="mailto:Personal_Submersibles@psubs.org" id="yui_3_16_0_1_1418600242974_7938">Personal_Submersibles@psubs.org</a><br><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" id="yui_3_16_0_1_1418600242974_7937">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br><br><br></div> </div> </div> </div></body></html>