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Re: Tightening hull to deck joint
I think you have figured out correctly how boat was put together. The toe rails would have gone on well after the deck and hull were joined. The butyl tape never sets up, so that can be "squeezed" later when rails are added.
One problem boat builders had, was that it took two guys to install all those bolts. One outside, one inside. Later Mirage switched to an external flange and then one guy could put in and tighten all bolts.
If you find some bolts leaking and loose, take them out, add a sealant that remains pliable, like Lifecaulk or ??? and push bolts back in. Then have one person hold head while other tightens nuts underneath.
Water probably enters from deck, so check along edge of toerail to see if there are gaps in places. If there are, one option is to mask the deck about 1/16" from edge of rail, then try to run in some thin silicone. Regular marine silicone may be OK with caulking gun, but you can get a product for sealing car window glass from auto suppliers. It is quite thin and will run in. Tolleys Creeping Crack cure is similar, but probably too thin to work in this case. After it has set, cut along edge down to deck, then remove masking tape. This should hopefully prevent water from entering and getting to the bolts.
Last edited by FreeAgent; 06-19-2017 at 11:20 PM.