Chainplate questions.
Joe, There are knees below in the cabin on those E31's fitted with aluminum chainplates, but not after the conversion to stainless steel. At the hull #47 change over, the stainless ones are oriented on deck parallel to the center line of the boat whereas the earlier aluminum ones are athwart, thus the knees. As a matter of fact the stainless ones are glassed to the hull in the configuration of the teeth of a comb, the spine of which is horizontal, either all one piece of metal or welded that way. Don't think that yours aren't aluminum just because of the black paint. Some of the early E31 sloops with teak anchor platforms were reinforced beneath with 1/4" plate aluminum that the factory painted black. I've seen that done on several of them. As to chainplate corrosion, first of all let me say that I'm rapidly drifting away from any personal technical knowledge when it comes to metallurgy. Actually I'm not much of an expert of anything, truth be told. But I think you are referring to crevice corrosion in stainless steel which it seems pretty likely, would occur just out of sight where it's not only hidden from view but also deprived of as much oxygen as in the open air. I've not heard of that or anything similar to that with aluminum, maybe others smarter than I am can step in here and straighten me out before I go any farther. I have used butyl tape as a bedding material on our boat but not at the chainplates. I can see that working just fine for a cleat or stanchion base, neither of which are prone to as much movement in use as our chainplates can be. The 3M 101 is so easy to use (not that the butyl isn't) that I never even considered anything other given the endorsement of the 3M tech rep I spoke with who really seemed to know what he was talking about. When he told me that it would stick to glass and stainless and would flex with them, I was sold and didn't want to experiment on my own. And while on the subject, my best guess is that yours are aluminum given the date of manufacture prior to our E31's and the presence of black paint on yours below deck. I do have documented that a stainless steel chainplate gave out just below the deck at the worst time possible on E31 hull #60 and almost caused total failure of the rig according to the owner at the time. Her solution was to have all of them removed and replaced with individual ones through bolted to the outside of the hull and that when I mentioned it to Bruce King, he shook his head in disgust. I hope some of the above helps you in your decision making. Cheers, Glyn