<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1447268074733_2945"><span>Hi Guys,</span></div><div id="yui_3_16_0_1_1447268074733_2945"><span>The idea was to keep the tanks at a high pressure all the time, they are </span>automotive quality so I think quite reliable. But having said that, I agree, the risk of loosing buoyancy from one tank is real. Fabricating a buoyancy tank is an option I have not looked at yet. </div><div id="yui_3_16_0_1_1447268074733_2945">Hank</div> <br><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 Wednesday, November 11, 2015 11:24 AM, Alan via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br> </font> </div> <br><br> <div class="y_msg_container"><div id="yiv7209746580"><div><div>Hank,</div><div>in general, from memory, the fibreglass products I put through my</div><div>pressure program, had similar external pressure resistance to the internal.</div><div>However the carbon fibre had better tensile strength than compressive strength.</div><div>If your tanks are rated to 3,600psi they probably have a 4 x safety factor ( you could </div><div>check that), so may crush at 14000 psi or 28,000ft. </div><div>looks like a big safety margin. I am putting in a positive comment here but</div><div>obviously that would need verifying.</div><div>Cheers Alan<br clear="none"><br clear="none">Sent from my iPad</div><div class="yiv7209746580yqt8661643902" id="yiv7209746580yqt44249"><div><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"><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div dir="ltr" id="yiv7209746580yui_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="yiv7209746580yui_3_16_0_1_1447248265971_2399">Any thoughts or concerns anyone????</div><div dir="ltr" id="yiv7209746580yui_3_16_0_1_1447248265971_2399">Hank</div></div></div></blockquote></div><blockquote type="cite"><div><span>_______________________________________________</span><br clear="none"><span>Personal_Submersibles mailing list</span><br clear="none"><span><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a></span><br clear="none"><span><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a></span><br clear="none"></div></blockquote></div></div><br><div class="yqt8661643902" id="yqt97241">_______________________________________________<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></div></body></html>