<html><head></head><body><p dir="ltr">That would be true if there were no friction, and if there were no forces acting normal to the shell surface; however, such an angle would be very slight indeed. In reality, the same pressure that is acting to compress the sphere is also acting to press the hatch into the hole, and there is friction between the mating surfaces, as well as tension from the hatch dogs. As such, the range of interface angles that will still allow the hatch to carry the full shell stress is somewhat greater. It's a bit of a moot point, since such load carrying ability is not relied upon in design, as reinforcement of the shell surrounding the hole is required by the rules, but is a thought exercise for true optimization of the geometry.</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On February 13, 2016 7:21:10 PM MST, Private via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">Very interesting, I had not thought of that. Would the cone not just have to be angled such that its surface were normal to the outer surface of the sphere?<br /><br />Thanks,<br /><br />Alec<br /><br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> On Feb 13, 2016, at 8:45 PM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br /> <br /> At what angle is the interface? I ask because as the shell compresses,<br /> that shell stress will act through the interface on the hatch, and at<br /> some critical angle, will actually act to push the hatch out of the hole<br /> - at least to the extent that the hull shell deflects / gets smaller<br /> under pressure. This is dependent on both the interface angle, the<br /> friction between the two mating surfaces, and the strength of your hatch<br /> dogs. Ideally, you want the hatch to lock in place under the
stress and<br /> provide that continuous load path through the hatch dome, instead of<br /> being pushed outboard by the deflecting shell. In the latter case, the<br /> deflection will be minor and probably not represent a sealing problem,<br /> but it will cause the shell to behave as if it doesn't have that<br /> continuous load path through the hatch carrying the full shell stress,<br /> necessitating greater reinforcement around the hole. That said, your<br /> hatch land may already be sufficient reinforcement - that's why I was<br /> hoping for a closer look.<br /> <br /> Sean<br /> <br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;"> On 2016-02-13 15:17, hank pronk via Personal_Submersibles wrote:<br /> Sean,<br /> Yes the hatch and seat are conical. The hatch dome is in line with the<br /> hull so the load path is a smooth line. <br /> Hank<br /></blockquote> <br /><hr /><br /> Personal_Submersibles
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