Deck Fitting Re-Bedding
My old sailboat's construction is mostly solid fiberglass panels, not constructed like the newer boats with a core of lightweight material between two fiberglass skins. Re-bedding a solid panel is straight forward and easy. The fiberglass skin panels need additional work.
After taking the fitting off the boat the fitting and the fiberglass needs to be cleaned with solvent like xylene to get all the old bedding material off them. New bedding will not seal if it is not well cleaned.
With a skin panel deck you next need to drill out the mounting holes and make them over sized. They need to be bout twice the size of the mounting bolt. Then with a bent tool like a allen wrench dig out some of the core between the skins. Vacuum out the partials and the masking tape the bottom hole.
Next fill the new cavity and hole with epoxy, this seals the soft core material so it will not wick water in to it if the bedding leaks. After the epoxy is hard drill the proper mounting bolt size hole in the new epoxy plug. Now when you bed it can get a good seal and the panel will not crush when you snug the fitting down.
A polyester sealant like 3M 4000 UV works well but it is incompatible with some plastics. Test any sealant first to make sure it is compatible and is OK.
Put the sealant on the clean fittings and a little in the hole and mount. Do not tighten the fitting all the way down right off. If you let the sealant cure one day and then snug it all the way down you get a gasket like seal that is more waterproof.
Make sure you test fit the fitting and bolts in the new holes before you put the sealant on and try tightening it down. Also use large washers on the underside to dissipate stress over a larger area on the fiberglass under skin. You are in for a major big redo and cleanup if the fit is not good and up put the sealant on and try to mount a bad fit.
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