<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div style="RIGHT: auto"><SPAN style="RIGHT: auto">Hank,</SPAN></div>
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<div style="RIGHT: auto"><SPAN style="RIGHT: auto">I was standing in Frank Busby's kitchen one day many years ago discussing this same question. He had returned from Finland on a mission to carefully document two deep diving subs being built there for the Soviets (Finland agreed under threat of economic sanctions to allow the inspection). The two subs in question had very large stern props driven by hydraulics that turned very slowly. They were later named Mir 1 & 2. Frank compared the concept to ice breaking ships that use huge props that turn very slowly. It's quite efficient because there is little energy wasted on turbulence and cavitation.</SPAN></div>
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<div style="BACKGROUND-COLOR: transparent; FONT-STYLE: normal; FONT-FAMILY: arial, helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 16px; RIGHT: auto"><SPAN style="RIGHT: auto">Also, in the realm of human powered subs, the winners have all had large diameter low aspect ratio props that look for like aircraft props. </SPAN></div>
<div style="BACKGROUND-COLOR: transparent; FONT-STYLE: normal; FONT-FAMILY: arial, helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 16px; RIGHT: auto" class=ms__id5838><SPAN style="RIGHT: auto"></SPAN> </div>
<div style="BACKGROUND-COLOR: transparent; FONT-STYLE: normal; FONT-FAMILY: arial, helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 16px; RIGHT: auto" class=ms__id5838><SPAN style="RIGHT: auto">But there are trade offs- gear reduction will use a little power. Belt reduction a little less. There is more drag on a big prop when it is not turning (unless you feather it).</SPAN><SPAN style="RIGHT: auto">Fouling a big prop is more likely unless you put it in a big cage. But if the goal is lower shaft speed then it can be a good way to go.<VAR id=yui-ie-cursor></VAR></SPAN></div>
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<div style="BACKGROUND-COLOR: transparent; FONT-STYLE: normal; FONT-FAMILY: arial, helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 16px; RIGHT: auto"><SPAN style="RIGHT: auto">Greg</SPAN></div>
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<DIV style="BORDER-BOTTOM: #ccc 1px solid; BORDER-LEFT: #ccc 1px solid; PADDING-BOTTOM: 0px; LINE-HEIGHT: 0; MARGIN: 5px 0px; PADDING-LEFT: 0px; PADDING-RIGHT: 0px; HEIGHT: 0px; FONT-SIZE: 0px; BORDER-TOP: #ccc 1px solid; BORDER-RIGHT: #ccc 1px solid; PADDING-TOP: 0px" class=hr contentEditable=false readonly="true"></DIV><FONT size=2 face=Arial><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> hank pronk <hanker_20032000@yahoo.ca><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> Wednesday, September 4, 2013 6:58 PM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> [PSUBS-MAILIST] prop size<BR></FONT></DIV>
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<DIV style="BACKGROUND-COLOR: transparent; FONT-STYLE: normal; FONT-FAMILY: tahoma, new york, times, serif; COLOR: rgb(0,0,0); FONT-SIZE: 16px">I have a two part question,</DIV>
<DIV>Is it beneficial to increase my propeller size to increase efficiency. I was under the impression from my boating days that a large slow prop is more fuel efficient. It should increase battery range and slow down the shaft speed, helping the seal.</DIV>
<DIV>I have a much larger prop left over from boating and I am thinking of using it on Gamma</DIV>
<DIV>The next question is,,, is there anyone here with the ability to calculate the new rpm for my given prop size and motor hp.</DIV>
<DIV>Hank<VAR id=yiv835097061yui-ie-cursor></VAR><BR></DIV>
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<DIV style="BORDER-BOTTOM: #ccc 1px solid; BORDER-LEFT: #ccc 1px solid; PADDING-BOTTOM: 0px; LINE-HEIGHT: 0; MARGIN: 5px 0px; PADDING-LEFT: 0px; PADDING-RIGHT: 0px; HEIGHT: 0px; FONT-SIZE: 0px; BORDER-TOP: #ccc 1px solid; BORDER-RIGHT: #ccc 1px solid; PADDING-TOP: 0px" class=yiv835097061hr></DIV><FONT size=2 face=Arial><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> Jon Wallace <jonw@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> Wednesday, September 4, 2013 6:18:15 AM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> [PSUBS-MAILIST] There's gold in them-thar waters<BR></FONT></DIV>
<DIV style="RIGHT: auto" class=yiv835097061y_msg_container><BR><BR><A href="http://www.usatoday.com/story/news/nation/2013/09/03/florida-family-gold/2757357/" rel=nofollow target=_blank>http://www.usatoday.com/story/news/nation/2013/09/03/florida-family-gold/2757357/</A><BR>_______________________________________________<BR>Personal_Submersibles mailing list<BR><A href="mailto:Personal_Submersibles@psubs.org" rel=nofollow target=_blank ymailto="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</A><BR><A href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel=nofollow target=_blank>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</A><BR><BR><BR></DIV></DIV></DIV></DIV></DIV></DIV><BR>_______________________________________________<BR>Personal_Submersibles mailing list<BR><A href="mailto:Personal_Submersibles@psubs.org"
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