Bedding windows..help

[JDAM]

Whats the best compound for bedding new ports.

The yard recommends a Sika flex product, while the window manufacturer recommended GE II exterior silicone. The GE II is available at Home Depot at half the price.

[aflanigan]

It depends on what type of material your ports are made of, and what mounting desing (flanged or clamped).

See this article by David Pascoe on rebedding portlights:

http://www.yachtsurvey.com/WindowRepair.htm

"To reset the glass, use a silicone based window glazing SPECIFICALLY designed for this purpose. Do not use plain old silicone sealer."

[GordMay]

Actually, Pascoe recommends a hybrid window caulk of Silicon-Epoxy.
Gord

[GordMay]

Window repairs, from Catalina Yachts:
http://www.catalina38.org/windowleakrepairs.htm

What Sealant Do You Need? - by Don Casey
“For an adhesive seal of plastic components, select a silicone/polyurethane hybrid.”
http://www.boatus.com/boattech/casey/35.htm

[HeartofGold]

I have a related question to ask of anyone who would like to throw in their 2 cents worth. I have just replaced my windows and port frames (newly remanufactured) and will need to mount the plastic frames in the port openings. I painted the coachroof with Awlgrip, and I am looking for a porper bedding compound for the plastic frames. No portion of the window will come into contact with said bedding compound as they are suspended in the frame.

Someone else recently suggested that I bed plastic parts (such as Harken bases) in 4200, but that seems a little too permanent for this application

Any and all suggestions are welcome.

Doug

[aflanigan]

See Gordmay''s post of Don Casey''s sealant article above.

"However, the solvents in polysulfide sealant attack some plastics, causing them to harden and split. Specifically, you must not use polysulfide to bed plastic windshields or plastic portlights--either acrylic (Plexiglas) or polycarbonate (Lexan). Don''t use it to bed plastic deck fittings either, including plastic portlight frames. Plastic marine fittings are typically ABS or PVC, and polysulfide will attack both. If you know that the plastic fitting is made of epoxy, nylon, or Delrin, you can safely bed it with polysulfide. Below-the waterline through-hull fittings are in this group, but when there is any doubt, select an alternative sealant . . . For an adhesive seal of plastic components, select a silicone/polyurethane hybrid. An adhesive sealant maintains its seal even when stresses pull or pry the bedded components apart. The sealant stretches like the bellows joining the two sides of an accordion. This accordion effect can be especially useful for plastic portlight installations where the portlights are captured between an inner and outer frame. Although silicone has amazing elasticity, its lack of adhesion means any expansion of the space between the frames is likely to cause the seal to fail."

Allen F.

[Silmaril]

The bedding of choice that the "Pro''s" use is Dow Corning 795.

It is not a "Fast-Set" however, it needs to be clamped and kept dry for 7 days, at above 60deg F. You also need to let it "breathe" so you can''t put the windows in and duct-tape them in place.

The stuff is great, has tremendous elasticity, is water proof and has great hold. It is a bit tricky to work with, but the results will last a decade or more, and it absolutely, positively, will not harm your windows. Comes in a rainbow of popular colors, as long as you are a dog and can only see black or white.

I''ve done a couple of hatches, and will be doing my side cabin lights with it.

This stuff is the only way to go. Just don''t be in any particular hurry for about a week.