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Re: [PSUBS-MAILIST] alternative dome forming



Alan,

I'm not sure I understand that last paragraph. Pentagonal arc segments of 4" thickness were formed into the original Johnson Sea-Link pressure hulls and made many hundreds of dives. They were not abandoned, but rather superseded by new techniques that allowed hulls to be fabricated without the visual discontinuities.

Ultimately these hulls were made thicker, but only after many dives to 3000 feet did that requirement become evident. The hulls suffered some unpredicted axial fractures around the penetration plates. There were no catastrophic failures, aside from the nerves of a few people who had the sweet ever-lovin' bejesus scared out of them at depth.

Vance



-----Original Message-----
From: Alan James <alanjames@xtra.co.nz>
To: personal_submersibles@psubs.org
Sent: Mon, Apr 5, 2010 8:46 pm
Subject: [PSUBS-MAILIST] alternative dome forming

Following  on from my previous post, where I sugested it may be possible to form a dome
by stacking & glueing several rings of acrylic on top of each other, I contacted my
acrylic fabricator & put the idea past him. He thought that it was entirely feasable &
considered the joins invisible unless I was looking straight through them. He said he had
100mm thick cast acrylic sheet wich would require 3 sections &  2 joins for the size I need.
He also had a large 2 axis router comming in June & beleived the finishing of the surface
to be easy. His only apprehension being the annealing time in his large oven; Once to set
the glue & anealed again after the machining. The all up cost shouldn't increase much more with thickness,
just diameter.
Will add that early domes used to be fabricated from pentagonal sections but were abandoned
because stock cast acrylic sheets that the pentagons were formed from back then weren't thick
enough to attain the depths that Stachiw was wanting to acheive.
Alan