Winch replacement ,dissimilar metal, CD27

[Warren Kaplan]

I just replaced the old Lewmar 7 genoa winches with new Lewmar 16ST self tailers. On the 1980 CD27 the winch sits on a bronze pedestal and the bolts from the winch to the pedestal do NOT go into the deck, hull or anything else that may give leakage concerns.
The base of the chrome plated bronze winch is just bronze and it is sitting on a bronze pedestal. So far, so good. I could not find bronze nuts and bolts (do they even exist) so I bought new stainless steel hardware. I installed the screws throught the bronze base and through the bronze pedestal WITHOUT any bedding compound at all since I had no leakage concerns. Now that I'm done, I'm wondering if I'll get corrosion problems from dissimilar metals. We all use bedding in screw holes when we worry about leakage, but does that bedding really insulate metal enough (electrolytically) to prevent corrosion when you tighten up those fastening bolts and literally squeeze most of the bedding out anyway? One observation...the old Lewmar 7s looked like they were fastened to the bronze pedestal with stainless steel bolts (for probably 20 yrs) and they looked pretty good to me when I took them out. They just loosened right up with the socket wrench and there were 10 of them on the 2 winches. So, I guess the real question is, can stainless steel and bronze "go together" without much of a corrosion problem? By the way, its no big deal to reinstall the winches with bedding compound. But is it even necessary? If so, what bedding compound would you use here for electrical insulation?
Thanks
Warren Kaplan
S/V "Sine Qua Non"
CD27 #166



Setsail728@aol.com

[Tom]

I just replaced the old Lewmar 7 genoa winches with new Lewmar 16ST self tailers. On the 1980 CD27 the winch sits on a bronze pedestal and the bolts from the winch to the pedestal do NOT go into the deck, hull or anything else that may give leakage concerns.
The base of the chrome plated bronze winch is just bronze and it is sitting on a bronze pedestal. So far, so good. I could not find bronze nuts and bolts (do they even exist) so I bought new stainless steel hardware. I installed the screws throught the bronze base and through the bronze pedestal WITHOUT any bedding compound at all since I had no leakage concerns. Now that I'm done, I'm wondering if I'll get corrosion problems from dissimilar metals. We all use bedding in screw holes when we worry about leakage, but does that bedding really insulate metal enough (electrolytically) to prevent corrosion when you tighten up those fastening bolts and literally squeeze most of the bedding out anyway? One observation...the old Lewmar 7s looked like they were fastened to the bronze pedestal with stainless steel bolts (for probably 20 yrs) and they looked pretty good to me when I took them out. They just loosened right up with the socket wrench and there were 10 of them on the 2 winches. So, I guess the real question is, can stainless steel and bronze "go together" without much of a corrosion problem? By the way, its no big deal to reinstall the winches with bedding compound. But is it even necessary? If so, what bedding compound would you use here for electrical insulation?
Thanks
Warren Kaplan
S/V "Sine Qua Non"
CD27 #166

Warren, I'm not a metallurgist so take my opinion as anything definitive but I've read or have always heard that bronze and stainless are pretty close on the periodic chart therefore there is relatively little activity between them. Below the water would be a definite no-no, but for things that aren't normally submerged I don't think it would be a problem. In fact, don't bronze turnbuckles often come with stainless clevis pins when you buy them? And if they don't what are you going to do about stainless shrouds with stainless eyes in bronze turnbuckles? I've never seen a boat with bronze standing rigging, but I'm sure you've seen a lot of bronze turnbuckles and chain plates around the boatyard. We all put ss bolts through the halyard winches and attach them to aluminum masts and those are really dissimilar metals (and you do have corrosion problems).

However I would use bedding compound. For stainless to work it has to either be exposed to the air or completely sealed from moisture. You do not want any moisture between the pad and the stainless regardless of whether it leaks or not, and you don't want moisture between stainless and bronze because you are artificially creating a "submerged" condition. It may be tight today, but years from now if it weeps just a little you can create problems.

Now the metallurgists may come on behind me here and explain why I'm wrong and if they do, go with their advice. I'm not an expert and this is based on observation, thinking, and things I've heard from I don't even remember where. Does it stand to reason that all these companies would be spending money on bedding compound if you didn't need it?



TomCambria@mindspring.com

[John M]

If you are want to isolate dis-simular metals, try Lock-Tite, or better yet, try a product called Tef-Gel, available thru West Marine.

I just replaced the old Lewmar 7 genoa winches with new Lewmar 16ST self tailers. On the 1980 CD27 the winch sits on a bronze pedestal and the bolts from the winch to the pedestal do NOT go into the deck, hull or anything else that may give leakage concerns.
The base of the chrome plated bronze winch is just bronze and it is sitting on a bronze pedestal. So far, so good. I could not find bronze nuts and bolts (do they even exist) so I bought new stainless steel hardware. I installed the screws throught the bronze base and through the bronze pedestal WITHOUT any bedding compound at all since I had no leakage concerns. Now that I'm done, I'm wondering if I'll get corrosion problems from dissimilar metals. We all use bedding in screw holes when we worry about leakage, but does that bedding really insulate metal enough (electrolytically) to prevent corrosion when you tighten up those fastening bolts and literally squeeze most of the bedding out anyway? One observation...the old Lewmar 7s looked like they were fastened to the bronze pedestal with stainless steel bolts (for probably 20 yrs) and they looked pretty good to me when I took them out. They just loosened right up with the socket wrench and there were 10 of them on the 2 winches. So, I guess the real question is, can stainless steel and bronze "go together" without much of a corrosion problem? By the way, its no big deal to reinstall the winches with bedding compound. But is it even necessary? If so, what bedding compound would you use here for electrical insulation?
Thanks
Warren Kaplan
S/V "Sine Qua Non"
CD27 #166

johnmartin55@hotmail.com