[PSUBS-MAILIST] Fw: Elementary 3000 new paint

[hank pronk via Personal_Submersibles]

Sean,I went with a angle of 15 degrees off vertical on the land, I did that thinking if the angle was closer to vertical there would be more force generated by the hatch pushing into the land.  This force would help support the reinforcing ring against the sphere.  I struggled with this because I did not want the angle so close to vertical that the hatch could get stuck in the land.  I also kept the reinforcing ring high in the sphere so that the bulk of the material was in line with the sphere.  I did that so there was not unsupported material at the bottom of the ring.  I considered machining the top of the land ring smooth with the sphere for continuity but opted to keep the extra material for brute strength.  All of this is based entirely on my gut feeling.  How is that for an engineering principal. ;-)   Hank 

    On Saturday, February 13, 2016 8:12 PM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 

 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.Sean


On February 13, 2016 7:21:10 PM MST, Private via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
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?

Thanks,

Alec


 On Feb 13, 2016, at 8:45 PM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 
 At what angle is the interface? I ask because as the shell compresses,
 that shell stress will act through the interface on the hatch, and at
 some critical angle, will actually act to push the hatch out of the hole
 - at least to the extent that the hull shell deflects / gets smaller
 under pressure. This is dependent on both the interface angle, the
 friction between the two mating surfaces, and the strength of your hatch
 dogs. Ideally, you want the hatch to lock in place un! der thestress and
 provide that continuous load path through the hatch dome, instead of
 being pushed outboard by the deflecting shell. In the latter case, the
 deflection will be minor and probably not represent a sealing problem,
 but it will cause the shell to behave as if it doesn't have that
 continuous load path through the hatch carrying the full shell stress,
 necessitating greater reinforcement around the hole. That said, your
 hatch land may already be sufficient reinforcement - that's why I was
 hoping for a closer look.
 
 Sean
 

 On 2016-02-13 15:17, hank pronk via Personal_Submersibles wrote:
 Sean,
 Yes the hatch and seat are conical. The hatch dome is in line with the
 hull so the load path is a smooth line. 
 Hank

 

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