Deck Prisms

[Thaddeus J. Van Gilder]

So, what is the best thing to bed the glass with?

-Thad

[mhoffman]

Autos and glazers in greenhouses use butyl tape- pretty cheap, easy to work with, flexible..
Just my thoughts.
Matt

[Jim Budde]

Probably a lack of nautical knowledge on my part, but why a prism on a boat?

[Concordia..41]

Jim, this isn't a real one - just a glorified paperweight, but the explanation is real:

Deck Prism (http://shop.store.yahoo.com/lonesailorshipstore/deckprism.html)

Plus it's the first one that came up in Google :D

[Bob Cleek]

Since a prism is a pretty hefty hunk of glass, the bedding compound isn't so critical as with windows, which can crack when the wood around them swells and the bedding isn't flexible enough to compress and relieve the stress. Still, as with glass, I'd favor silicone caulk if it is covered with a trim ring to prevent UV breakdown. Otherwise, just about any polysulfide compound should work. Putties that harden up, like white lead, used to be the standard issue, but they do harden up over time and have to be rebedded when they crack and loose their ability. If you are interested in prisms, BTW, check out the Toplicht catalog. They have three or four different styles or real prisms, not the touristy paperweights like Mystic Seaport sells! Amazing catalog, that Toplicht. Too bad some entrepreneur in the US doesn't open up a franchise and publish the catalog in English!

[Figment]

The reason that glaziers use butyl rubber tape is that it remains flexible indefinitely, which is critical when joining materials glass and metal of such wildly different thermal expansion coefficients.

I think this bodes well for it's application with the moisture expansion and contraction of a wooden deck.

[Thaddeus J. Van Gilder]

I am actually using a prism from ABI. bronze rectangular frame, and an acryllic prism....

If the acryllic sucks, it is the same size as the one sold through classic marine, soI could just switch it out.

[Cedarhill Boatworks]

Acrylic is much more optically clear than glass. An acrylic deck prism will throw a lot of light. They are easy enough to make actually. Any plastics supply house will sell you blocks of clear acrylic for pennies. Shape the block on a table saw and then sand and polish smooth. I have a pair of them that my father made years ago. They turn the dark and dreary quarter berth area into a very bright little space.