>If you know how your fittings were bedded, I'd like to know, to compare with >the technology extant when this book was written. There have been many >advances in marine corrosion prevention since 1978, I expect. I would think so. To answer your question, generally, I use two different types of bedding compounds, depending on the expected "permanence" of the installation. For more permanent items (like a new teak toerail I'm about to install on a 32 foot boat), I will use a polyurethane sealant, most likely 3M 5200. This stuff is incredible. After it cures, expect to have to get out the chain saw to get it off. I have not yet tried it, but 3M makes a less "adhesive" polyurethane called 4200. This would presumably be quite good, as well. For items that I may want to remove in a couple of years (to re-bed, or whatever) (like the eight new ss portlights I'm installing), I will use a polysulfide sealant, like the 3M 101. Polyurethane would make it too difficult to take them out for repairs. I will rarely use a silicone sealant, but for some kayak uses they might be more appropriate. With some of the poly's, you have to be careful about compatibility with plastics. Some of them will eat right through some plastics. For providing a barrier between dissimilar metals, I would imagine most of these would work. My understanding is that the bedding compounds used 25 or 30 years ago (when the boats I work on were built) were quite different. Somewhere, I have some purportedly "technical" explanations of what they were and how they were applied. I read this stuff in passing on the marginal likelihood anything useful might appear, but quickly forget the details. My general impression is that much less thought went into the subject at that time. For example, I am told that the factory that produced my current project (a very highly respected yacht mftr) glopped on the same "compound" on every application in huge quantities. The damn stuff oooooozes out of the hull/deck joint even now (well, not now that I have fiberglassed over it, but before that), and is malleable and largely useless. Leaks at that joint were notorious. 3M 5200 is like some sort of miracle substance by comparison. Leaks? Hah! Unlikely. Yucky to work with, though. Mark *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Tue Apr 11 2000 - 19:18:29 PDT
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