View Full Version : Marine Silicone rubber question

David Usitalo
02-10-2003, 08:28 PM
I'm getting ready to bed my cast iron keel up into the keel and keelson of my 1948 Starboat.
I've settled (almost) on 3M Marine Silicone Rubber at $9 a cartridge. It has the low-adhesion, gasket-forming properties that I want.
Then I discovered DAP Silicone Rubber - same low adhesion, claims to be waterproof - at $3.50 a cartridge.
Does anyone's experience give me caution here? I don't mind getting the 3M Marine, if there's any doubt that the other stuff will work below the waterline.
Thanks for any advice.
David Usitalo

Bob Cleek
02-10-2003, 09:54 PM
Well, since you mention the cost of the crap you are thinking of using, I suppose you are concerned about price. Both products are made for people who don't care about what it costs, I suppose. Neither are appropriate for the use you intend. Now, I suppose they will serve as bedding, by why would you want to spend ten bucks a tube for silicone and use it to bed a keel? Mmmmm? There are very limited uses for silicone around a boat. (I find it good for bedding windows. I've heard it is also highly recommended for augmenting the boobs on a bow ornament. That's about it for silicone.)

The industry standard luting compound for bedding ballast keels is Henry's Wet Patch. Yep... believe it or not. That black gooey stuff in the purple can you get at the hardware store for patching leaky roofs. In my experience, it doesn't fix leaky roofs too well, since if they are leaking it is probably past time to put on a whole new roof, but it is great for luting ballast keels.

What you do is get some Irish felt, or the heaviest and softest grade roofing felt you can find, which is about the same thing, and lay it between the keel and ballast, like a gasket, with Henry's slathered above and below it, then bolt her on. Make sure to wrap a strand of caulking cotton around the keel bolts up against the keel, so they will form a gasket and the bolts won't leak.

True to tell, there's thousands of boats with keels bedded in Henry's doing just fine after years and years and years of use. And, the stuff is cheaper than dirt, so you don't have to skimp when you lay it on.

Todd Bradshaw
02-10-2003, 10:37 PM
The keel on my Starboat was bedded with plain white marine bedding compound. When I got and rebuilt the boat it was already 30 years old. It showed no signs of leakage or damage around the keel and I decided not to mess with it or try replacing the bedding compound with modern goo. I left it alone and actually drilled a hole through the keel, just above the bulb, ran a cable through the hole, lifted the entire boat with a Harken six-to-one catamaran mainsheet system and rolled it over in slings so that I could work on the bottom. During the rebuild, I probably rolled it three or four times and the keel still never leaked after the work was done. I don't like silicone on any boat, especially a wooden one and certainly have no complaints with traditional bedding compounds which are a lot cheaper than goo-in-a-tube and seem to work just fine.

Bob Adams
02-12-2003, 12:04 PM
Come on Cleek, don't mince words, what do you really think? ;)

Gresham CA
02-12-2003, 12:38 PM
Cleek? Mince words? I've never seen those in the same sentence. Bob's right though. Another thing is that paint wont stick to it either.

John Blazy
02-12-2003, 02:02 PM
Got a picture of that augmented bow ornament? Sounds real technical, so a pic would aid in technical enlightenment (for educational purposes only) :D