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Re: [PSUBS-MAILIST] Big acrylic dome problem
Hi Darek,
I'm not an expert, but all info that I have received says that you cannot
buy acrylic sheet wider that 48 inches or 1219 mm. This means that you will
need to settle for a 39 inch diameter dome if you wish to form from sheet.
I ran into the same dilema as you and had greg cottrell of precision
plastics form a dome for me at about 39 inches in diameter. I am now in the
process of building the seat and a tapered section to transition out to 48
inch hull diameter. The two companies that you mentioned are to my knowledge
the only two that can pour the window for you. I also found out that it
depleted my entire budget.
In either case I am quite sure that ANY lamination or fabrication of sheets
is a VERY BAD IDEA. You will be betting your life on this window, so I feel
that you must follow guidelines established.
Best Regards,
Jim Kocourek
----- Original Message -----
From: "Dariusz Hoffmann" <darekhoffmann@gmail.com>
To: <personal_submersibles@psubs.org>
Sent: Friday, June 06, 2008 12:55 PM
Subject: [PSUBS-MAILIST] Big acrylic dome problem
Hello everyone,
my name is Darek, I'm 27yo, I'm from central Europe
and I always wanted to build a sub.
I am curently on early stages of designing my sub (something similar
to XPC15 by Marlin Submarines, but smaller) and I have a problem with
with a front window. It should be a dome of acrylics 70 mm thick and
1500 mm (59") inner diameter. 125-135 deg. Thats a big window. After few
weeks of sending questions to dozens of acrylics manufacturers I am sure
that it is a serious problem. I found only one company that is capable
of making the thing - blanson ltd. Estimated price £12,000 to £14,000
(about 23600-27600 $). There is another one in UK - Stanley Plastics,
but i think the price would be similar. That price is just too high for
me. It is even higher than the cash i plan to spend on the whole sub!
Right now I am considering making the window myself. Worm forming of a sheet
is not a good idea because of the thickness of a sheet. So there are two
possibilities: molding in a form or creating a cube and machine it to a
dome. Since I have minor knowledge about the polymerization conditions
of acrylics it would be difficult for me to make it this way.
So here's the crazy idea. Take, lets say, 20 thick flat sheets and
join their surfaces
together using the acrylic cement. This cement is not a glue, it softens the
surfaces of acrylics and fuse them together creating one part. The bond
is transparent. This will form a cube. Next it should be taken on a big
lathe and machined into a roller. The roller should be machinned to a
half-dome and then machinned inside to create a dome.
The possible crossviews of the domes with bonds (depending on the
placement on a lathe) are shown here:
http://img377.imageshack.us/img377/8990/xsecdomesgh2.jpg
(Which one of these would grant a better visibility / strength ?)
I read that two parts joined this way will be fused to one part. But I
think that there has to be some loss of strength. What is the exact loss
- I do not know. 10-40% ? Tests on smaller parts should be made..
Thickness of the dome can be increased much, that is no problem for a
lathe...
What do you think about this idea ?
Do you have any other ideas of how to make it / where to buy it ?
Thanks for all your thoughts
Darek
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603-529-1100
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