Brent,
You made me think of an old engineering practice to see where
stresses were in a structure such as an arch. They would cut a model silhouette
of the arch out of thin acrylic and then apply stresses to it that would model
the anticipated loads. When the plastic arch was viewed with Polaroid
lens, the stress patterns would be revealed in the plastic. From various
samples we fooled with and associated images, I would expect that you would see
residual stresses in Karl’s failed ports and there would be quite a few
around the bolt holes.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Sent: Wednesday, September 03, 2008 1:08 PM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Delta Sub Front MBT Windows
Hello Jay,
I was talking to Greg Cottrell about this same matter several weeks ago, and he
was kind enough to give me some of his take on it. He also thought/knew
that the Delta's main pressure hull viewports having holes drilled thru the
acrylic to attach them was pre-spec as you said and have them grandfathered
in. He also said that they wouldn't be allowed to change them now if they
wanted to keep ABS certification. Unless they had loads of money to get the
whole sub re certified. That didn't make total since to me. I would
think they could just deal with the viewport assemblies and how they are
installed, as well as do some new calcs for that. But not have to redo all the
calcs and what not for the whole boat.
The main pressure hull view ports and the front main ballast tank acrylic
windows all have the attachment holes drilled in the acrylic from what I've
seen. The windows in the front most part of the sub are part of the free
flooding front MBT, much like the much thinner acrylic dome over Idabel's large
front dome, that acts as the front MBT. Where do you think Karl got part of
that idea from. ;)'
We can also see in a couple of the pics below that the Delta has five small
viewports mounted in it's front main pressure hull head.
I was talking with Karl about the two viewports he had fail, one on Idabel and
one on C-BUG, that had holes drilled in the acrylic to attach them, that I had
read about, and had wondered if the holes were the cause of the failures.
He said no, they failed for other reasons that had to do with the metal
structures that were around them not supporting them evenly. He has since
changed the design of the lower front flat viewport. This doesn't mean
that drilling holes in acrylic is a good idea, in my opinion. It's just a
interesting piece of data to add to are data.
http://www.frappr.com/?a=viewphoto&id=2384531&pid=10409653
http://www.frappr.com/?a=viewphoto&id=2384531&pid=10409648
Your resident hippy dreamer ;)'
Regards,
Szybowski