<div dir="auto">Hi Alan,<div dir="auto">Some quick maths shows that for a hatch 0.5m diameter, just 2PSI pressure difference is a force of over 1000kg. I doubt gas struts would be very useful in that scenario!</div><div dir="auto"><br></div><div dir="auto">Cheers,</div><div dir="auto">Steve Fordyce</div></div><div class="gmail_extra"><br><div class="gmail_quote">On 31 Dec 2017 9:48 am, "Alan via Personal_Submersibles" <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br type="attribution"><blockquote class="quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div>Ian, Tim,</div><div id="m_2207003101678918832AppleMailSignature">yes I was thinking about a cam type latch dog as you described.</div><div id="m_2207003101678918832AppleMailSignature">The automatic pressure relief valve that Emile has would automatically</div><div id="m_2207003101678918832AppleMailSignature">reduce any pressure in the hull to the equalisers spring closure pressure,</div><div id="m_2207003101678918832AppleMailSignature">maybe 2psi; then if you forgot to manually press this valve to fully equalise,</div><div id="m_2207003101678918832AppleMailSignature">any internal overpressure would be released as the hatch dog incrementally</div><div id="m_2207003101678918832AppleMailSignature">released the hatch.</div><div id="m_2207003101678918832AppleMailSignature">I guess the only reason for this law is to prevent damage from the hatch </div><div id="m_2207003101678918832AppleMailSignature">opening explosively. Perhaps gas struts would be suitable to stop this!</div><div id="m_2207003101678918832AppleMailSignature">Tim, I have a design for opening from the outside. There could be a grip</div><div id="m_2207003101678918832AppleMailSignature">on the seaward side of the overpressure valve to equalise from outside.</div><div id="m_2207003101678918832AppleMailSignature">I am feeling like I have some solutions now. </div><div id="m_2207003101678918832AppleMailSignature">Thanks, Alan.<br><br>Sent from my iPad</div><div class="elided-text"><div><br>On 31/12/2017, at 11:23 AM, irox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>> wrote:<br><br></div><blockquote type="cite"><div><div style="font-size:13px;color:rgb(0,0,0);font-family:arial,sans-serif">Although it doesn't have be to the same vent/mechanism as the hatch over pressure safety.<div><br></div><div>Also, there is a requirement for opening the hatch from outside, to add more complications (if you're strictly following regulations).<br><br><blockquote style="padding-left:5px;margin-left:0px;border-left:#0000ff 2px solid;font-weight:normal;font-style:normal;text-decoration:none;font-size:10pt;font-family:arial,sans-serif;color:black">-----Original Message-----
<br>From: T Novak via Personal_Submersibles <u></u>
<br>Sent: Dec 30, 2017 1:16 PM
<br>To: 'Personal Submersibles General Discussion' <u></u>
<br>Subject: Re: [PSUBS-MAILIST] Hatch Closure Mechanism
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<u></u><u></u><u></u><u></u><u></u><u></u><u></u><u></u><u></u><u></u><u></u><u></u><div class="m_2207003101678918832WordSection1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Just to add a complication to the project, you will need to have the vent accessible by someone on the outside too, in case the sub has surfaced but the operator is incapacitated.<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Tim<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"><u></u> <u></u></span></p><div><div style="border:none;border-top:solid #e1e1e1 1.0pt;padding:3.0pt 0in 0in 0in"><p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Personal_Submersibles [<a href="mailto:personal_submersibles-bounces@psubs.org" target="_blank">mailto:personal_submersibles-<wbr>bounces@psubs.org</a>] <b>On Behalf Of </b>Alan via Personal_Submersibles<br><b>Sent:</b> Saturday, December 30, 2017 12:51 PM<br><b>To:</b> Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>><br><b>Subject:</b> Re: [PSUBS-MAILIST] Hatch Closure Mechanism<u></u><u></u></span></p></div></div><p class="MsoNormal"><u></u> <u></u></p><div><p class="MsoNormal">Thanks Hank,<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">will have to think on this one. I want to let a novice dive my sub, so<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">the system needs to be bullet proof.<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">If I have some sort of lock mechanism I would need to be able to bypass<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">it if I needed to escape at depth. The pressure at depth would be apposing <u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">the manual operation of the overpressure valve. You could flood the sub first<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">but normally the hatch is un-dogged prior to the hull equalizing.<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal">Cheers Alan<u></u><u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal"><u></u> <u></u></p></div><div id="m_2207003101678918832AppleMailSignature"><p class="MsoNormal"><br><br>Sent from my iPad<u></u><u></u></p></div><div><p class="MsoNormal" style="margin-bottom:12.0pt"><br>On 31/12/2017, at 1:49 AM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>> wrote:<u></u><u></u></p></div><blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"><div><div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif">Alan,<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif">You could have a lock that prevents the hatch mechanism from opening that is activated by turning the hatch vent. I always vent before I one the hatch anyways.<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif">Hank<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif"><u></u> <u></u></span></p></div><div id="m_2207003101678918832yahoo_quoted_4704983245"><div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">On Friday, December 29, 2017, 11:09:03 PM MST, Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.<wbr>org</a>> wrote: <u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a"><u></u> <u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a"><u></u> <u></u></span></p></div><div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">Just doing some evening reading of the GL rules & noticed this rule about hatches....<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">"the closing mechanism is to be designed in such a way that opening of<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">the hatch is only possible after pressure equalisation" <u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">I am wondering what options there are for achieving this.<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">Has anyone had experience of the hatch opening with explosive force due<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">to internal over-pressure not being equalised.<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">Alan <u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a"><u></u> <u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">Sent from my iPad<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a"><u></u> <u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">______________________________<wbr>_________________<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a">Personal_Submersibles mailing list<u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a"><a href="mailto:Personal_Submersibles@psubs.org" target="_blank">Personal_Submersibles@psubs.<wbr>org</a><u></u><u></u></span></p></div><div><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Helvetica",sans-serif;color:#26282a"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/<wbr>listinfo.cgi/personal_<wbr>submersibles</a><u></u><u></u></span></p></div></div></div></div></div></div></blockquote><blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"><div><p class="MsoNormal">______________________________<wbr>_________________<br>Personal_Submersibles mailing list<br><a href="mailto:Personal_Submersibles@psubs.org" target="_blank">Personal_Submersibles@psubs.<wbr>org</a><br><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/<wbr>listinfo.cgi/personal_<wbr>submersibles</a><u></u><u></u></p></div></blockquote></div><u></u><u></u><u></u><u></u></blockquote></div></div>
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