<html><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_1438894454011_5454"><span>Sean,</span></div><div id="yui_3_16_0_1_1438894454011_5453"><span>Thank you, just a thought, it would be 16 lb </span>heavier, but very easy and quick to fabricate. I could build it and clamp it to Gamma's hatch and do a depth test without risk to other parts.</div><div id="yui_3_16_0_1_1438894454011_5453">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 Thursday, August 6, 2015 9:32 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br> </font> </div> <br><br> <div class="y_msg_container"><div id="yiv0094294359"><div><div dir="ltr">These sorts of problems tend to require some FEA, as the straight shell calculations only account for the circumferential stresses and not the bending introduced into a hatch lip. That said, 0.875" is reasonably thick, and if you model such a dished head, faced off normal to the centre of curvature, turned to eliminate the acute outside edge and grooved for an o-ring, then the minimum distance between the corner of the o-ring groove and the outer shell surface will give you a reasonable approximation of the shell thickness to use for calculation, but then means that the hatch will be significantly heavier than it needs to be.</div>
<div dir="ltr">A deeper dish leads to less bending stress (and less extraneous material) but increases volume and decreases bearing area. There's probably an optimum tradeoff.</div>
<div dir="ltr">Sean<br clear="none">
</div>
<br clear="none"><br clear="none"><div class="yiv0094294359gmail_quote">On August 6, 2015 10:05:31 AM CDT, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv0094294359gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex;">
<div class="yiv0094294359yqt6876249441" id="yiv0094294359yqt10772"><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div id="yiv0094294359yui_3_16_0_1_1438873234788_2375">Hi Sean,</div><div dir="ltr" id="yiv0094294359yui_3_16_0_1_1438873234788_2375">I was thinking about making a hatch from a single piece of dished material instead of the typical dome welded to a ring etc. I have a tank head that is 7\8 thick 516-70 . I was thinking about cutting a disk from it at the apex and simply machining a flat land with o-ring groove. Is this a good or bad idea and would you be able to calculate the failure depth if I measure the depth of dish and dia.</div><div dir="ltr" id="yiv0094294359yui_3_16_0_1_1438873234788_2375">Hank</div></div></div><div style="margin-top:2.5em;margin-bottom:1em;border-bottom:1px solid #000;"></div><pre class="yiv0094294359k9mail"></pre><hr><br clear="none">Personal_Submersibles mailing list<br clear="none">Personal_Submersibles@psubs.org<br clear="none"><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><br clear="none"></blockquote></div></div></div><br><div class="yqt6876249441" id="yqt96391">_______________________________________________<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>