<html><head></head><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_1447268820803_2705"><span id="yui_3_16_0_1_1447268820803_2962">Hank,</span></div><div id="yui_3_16_0_1_1447268820803_2704"><span id="yui_3_16_0_1_1447268820803_2703">I did a quick calc on a sphere of nominal dimensions made of epoxy / fiberglass.</span></div><div id="yui_3_16_0_1_1447268820803_2704"><span id="yui_3_16_0_1_1447268820803_2818">With external pressure it had a depth of 4347ft, with internal 3785ft. I should have posted</span></div><div id="yui_3_16_0_1_1447268820803_2704" dir="ltr"><span id="yui_3_16_0_1_1447268820803_2963">the results in psi, but you get the picture.</span></div><div id="yui_3_16_0_1_1447268820803_2704" dir="ltr"><span id="yui_3_16_0_1_1447268820803_2964">The big thing to me would be that if you ruptured it by hitting anything, or so it failed, you would go down</span></div><div id="yui_3_16_0_1_1447268820803_2704" dir="ltr"><span>like a lead balloon. </span></div><div id="yui_3_16_0_1_1447268820803_2704" dir="ltr"><span>Alan</span></div><br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1447268820803_2648"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1447268820803_2647"> <div dir="ltr" id="yui_3_16_0_1_1447268820803_2646"> <hr size="1" id="yui_3_16_0_1_1447268820803_2788"> <font size="2" face="Arial" id="yui_3_16_0_1_1447268820803_2645"> <b><span style="font-weight:bold;">From:</span></b> Alan 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> Thursday, November 12, 2015 7:23 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] buoyancy<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1447268820803_2651"><br><div id="yiv7791184910"><div id="yui_3_16_0_1_1447268820803_2650"><div id="yui_3_16_0_1_1447268820803_2702">Hank,</div><div id="yui_3_16_0_1_1447268820803_2701">in general, from memory, the fibreglass products I put through my</div><div id="yui_3_16_0_1_1447268820803_2700">pressure program, had similar external pressure resistance to the internal.</div><div id="yui_3_16_0_1_1447268820803_2649">However the carbon fibre had better tensile strength than compressive strength.</div><div id="yui_3_16_0_1_1447268820803_3130">If your tanks are rated to 3,600psi they probably have a 4 x safety factor ( you could </div><div id="yui_3_16_0_1_1447268820803_3131">check that), so may crush at 14000 psi or 28,000ft. </div><div id="yui_3_16_0_1_1447268820803_2699">looks like a big safety margin. I am putting in a positive comment here but</div><div id="yui_3_16_0_1_1447268820803_2698">obviously that would need verifying.</div><div id="yui_3_16_0_1_1447268820803_2697">Cheers Alan<br clear="none"><br clear="none">Sent from my iPad</div><div class="qtdSeparateBR"><br><br></div><div class="yiv7791184910yqt5714830815" id="yiv7791184910yqt60110"><div id="yui_3_16_0_1_1447268820803_2696"><br clear="none">On 12/11/2015, at 2:33 am, hank pronk via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br clear="none"><br clear="none"></div><blockquote type="cite" id="yui_3_16_0_1_1447268820803_3134"><div id="yui_3_16_0_1_1447268820803_3133"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;" id="yui_3_16_0_1_1447268820803_3132"><div dir="ltr" id="yiv7791184910yui_3_16_0_1_1447248265971_2399">I was thinking about using CNG (compressed natural gas) tanks for buoyancy. The type 4 tanks are carbon fibre and rated for 3,600 psi and very light. My idea was to keep the tanks full of compressed air so they can withstand the sub depth rating plus a safety margin. I am liking trawl floats may be better now because they are rated high enough and not air filled. The CNG tanks are much cheaper and conveniently shaped. Hmmm not sure now.??</div><div dir="ltr" id="yiv7791184910yui_3_16_0_1_1447248265971_2399">Any thoughts or concerns anyone????</div><div dir="ltr" id="yiv7791184910yui_3_16_0_1_1447248265971_2399">Hank</div></div></div></blockquote></div><blockquote type="cite" id="yui_3_16_0_1_1447268820803_3137"><div id="yui_3_16_0_1_1447268820803_3136"><span id="yui_3_16_0_1_1447268820803_3135">_______________________________________________</span><br clear="none"><span id="yui_3_16_0_1_1447268820803_3138">Personal_Submersibles mailing list</span><br clear="none"><span id="yui_3_16_0_1_1447268820803_3140"><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org" id="yui_3_16_0_1_1447268820803_3139">Personal_Submersibles@psubs.org</a></span><br clear="none"><span id="yui_3_16_0_1_1447268820803_3142"><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" id="yui_3_16_0_1_1447268820803_3141">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a></span><br clear="none"></div></blockquote></div></div><br><div class="yqt5714830815" id="yqt40161">_______________________________________________<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"><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"></div><br><br></div> </div> </div> </div></body></html>