Thanks for an excellent article, Maine Sail
I'll be servicing the winches and replacing the grab and toe rails on my boat in the next few weeks, therefore my reading of your advice is very timely.
The rails show no signs of leaking on this 30 year old boat, so I'll ask the builder how they bedded them originally.
The port glazings have leaked, and the glazing needs replacement. The PO attempted caulking to seal, likely with silicone. I don't think the frame to hull joints leaked, I'll have to check. Butyl tape with bedding spacers sounds like the ideal re-glazing method, just like the high-rise windows use. (Stress between frame and glazing is a major cause of failure there)
A thought on aluminium fittings and stainless fasteners, as raised by casey1999
. Two possibilities spring to mind, First, smear the butyl over the fastener thread length that resides inside the fitting. Second, would Teflon plumber's tape over the threads through the fitting and just a little longer than the thickness of the fitting, provide adequate galvanic isolation? I'm sure the isolation will be there, and that's easy to test using the continuity setting on a multi-meter. Since the cleat base isn't tapped, the tape would be intact. But would it affect the butyl bedding?
Has anyone tried using plumber's tape for this, or might I be the first? (and or foolhardy experimenter, if I have to re-bed mixed metals) For a blind-fastened fitting with SS fastener into aluminium fitting, tape might work; another option might be an anti-seize or low strength thread-locker coating, but the plumber's tape is at least not at all messy.
ps. Don't know of too many fittings that use blind tapped holes...