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Hi All, Thank you for the good data to chew on guys. When I was working on different dome and flat viewports in the past, I didn't know about the hard neoprene type gaskets, and that it was considered a good option in some applications. I was interesting in another way to seal a dome or flat viewport that wasn't glued in, in such a way that it was hard to remove for maintenance and/or replacement. I now wish to use the hard gasket type seals in several applications. Do you think there would be any advantage to adding a small raised lip to the inside of the hard gasket in the dome or flat viewport seating flange? I was thinking it might be useful to keep the gasket from extruding in towards the interior. But since there is so many square inches of surface area on the exterior of the dome and/or flat viewport, much of it pushing down. I figure that there is far more pressure being transfered down to the domes or flat viewports seating surface then is being applied to the very small surface area on the outer most edge of the gasket. The configuration I was thinking of would have a small gap between the lip and the dome, say 1/8", and the gasket would be cut to fit tight against that lip. this way the gasket wouldn't have room to move and the dome wouldn't be affected by the lip. That grove that would be created would get condensation water running into it and might be a little hard to clean, but there might be a way to install a very soft gasket type seal in that groove to deal with that issue. To add a small lip in the interior of a flat viewport seat would be a little different and would need to be in my opinion, shorter to as to not ever touch the flat acrylic viewport under full rated pressure. So in that configuration one might want a thicker hard gasket. The viewports seat being distorted from welding, I believe is a very good point. This is why I was thinking about a way to make a poured type gasket, and in some way coat, wax, etc. the viewport so you can remove it after the gasket has cured. Then clean the viewport and install it for the final time in the orientation it was when the gasket was formed. Perhaps the orientation will not be a issue. This way you have a custom gasket that is not glued to your acrylic. This is what I was thinking about doing for my front lower viewport on my K-250 that has a lightly pitted seating surface. I'll smooth the seating surface out a fair bit with epoxy paint, but even if I get it smooth, there could well be some welding distortions to deal with. One could use a couple light coats of PVA mold release agent sprayed on, and if the paper or plastic protective coating is still on or could perhaps be reapplied on the flat acrylic viewports, then that might be a good way to go. For the domes you could add some things like that as well. Your resident pipe dreamer ;)' Regards, Szybowski From: kocpnt@tds.net To: personal_submersibles@psubs.org Subject: Re: [PSUBS-MAILIST] O-Rings & Acrylic Ports Date: Sat, 30 Aug 2008 11:02:54 -0500 Hi All,
I have to agree with Jay & Frank,
I will be using Sika-flex as advised by Greg who made the window. Even
though my ports are VERY heavy there is no way to have absolutely no distortion
from welding.
Using Sika-flex as a setting bed will mitigate this problem. I plan on
placing a very heavy bead in the base corner of the seat and pulling the window
into place with a retaining ring. The excess will be squeezed out and is messy,
but I plan on having my sign guy make some adhesive backed masking to cover only
the portion of the port that is not covered by the seat.
Then I can wipe away most excess, then remove the masking. This will not
risk scratching or cutting the window acrylic.
Best Regards,
Jim K
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