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Thanks Brian. That's how I came up with the 1/8 inch measurement.
I figured the steel ring on my 20 inch main window can shrink in
cold deep water by about 1/32 '' or maybe a little more, and the plexi can
grow from it's room temperature size to when it's in the sun at about 80
degrees, by about 1/16 to 3/32. When I go deep, or cold like here in Calif. the
temp can easily get down to 45 degrees. The plexi will shrink at the same time
as the steel, only more, and more slowly due to it's mass ( 3 inch thick )
The 1/8 inch diameter under sizing of the plexi will give me about 1/64
inch of space when the plexi is at it's largest.( in the sun ? ) and the
gap at depth in cold water shouldn't be any more than 1/16 when both pieces have
reached temperature equilibrium.
The other two smaller widows at 12 inch are only 2 inches thick, and the
gap on those could maybe be a little closer.
I won't be using an ''O'' ring on the widows, but instead plan on bedding
the plexi in polyurethane. Of the windows I've seen on tourist subs and some of
our groups subs, I just like the look of that type of seal. It is probably a
judgement call, but I think it's gonna seal better, due to the fact it's got 7
inches of contact against the plexi edge,( 2 '' flange, 3 '' thick, and 2 ''
face seal under the keeper ring.) where an ''O'' ring has 1/4 to 1/2 inch
contact, plus the fact that the plexi will actually come in contact with the
steel, which can't be good.
Still, I'll be taking Jon's advice and read the book. It never hurts to get
more info, especially when it's from someone so respected as Stachinow.
I'll get some newer pictures up on Frappr soon, and you guys can see more
what it's looking like.
Anyway, thanks for the advice, and have a great holiday. Frank D.
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