Eric mentioned Dolfinite and that is a very good product. We use it on our boat to bed things that are held securely by mechanical fasteners and may have to be removed periodically. So window frames, the big laminated teak block that supports our anchor windless on the foredeck, and other such items we bed with Dolfinite.
But.... Dolfinte dries out over time when exposed to air. Which is why the most experienced shipwright on the Grand Banks forum recommends running a faired bead of Polyseamseal around the outside of a Dolfinite seal, like the joint between a window frame and the cabine side. The Polyseamseal protects edge of the Dolfinite bedding from drying out.
On this same fellow's recommendation, we use Sikaflex to bed/seal window tracks, window glass, and other things where there can be some benefit in a degree of adhesiveness in the sealant.
Knowing nothing about your particular situation I would be inclined to use Sikaflex. I'm guessing your arch has some flex to it and Sikaflex's adhesive properties might help reduce or prevent any movement at the base of the arch that could open up a pathway for moisture to get through if the sealant was totally non-adhesive.
If the radar arch is something you anticipate having to remove or lift every so often to run new wire or whatever then Eric's suggestion of Dolfinite is a good one.
-- Edited by Marin on Thursday 7th of October 2010 06:59:05 PM
