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Bene505 03-21-2010 04:05 AM

rubbery material at hull-keel joint - what to replace it with?
Working on the boat yesterday I got to get a closer look at the rust around the keel to hull joint. It only appears where I did work last year.



There appears to be some type of rubbery material up in the joint.

Any clues what it is? My marina neighbor said that something like Silkaflex (?) is used there because of the expension and contraction of the 2 diffferent materials due to temperature changes.

Any clues what to use to replace it?

More pictures:


bartvdv 03-21-2010 06:43 AM

Do you have water entering bilge via keel bolts?
This could be galvanic interference between keel fin and keel plate/bolts.

To be sure i would lower the keel (turn the keel bolts open from inside).
Then remove all caulking on top of your keel fin and caulk excessively with new silkaflex.
Pull keel fin up (tighten keel bolts equally from inside bilge).
Now is sure watertight again!

Then paint it again.

sailingdog 03-21-2010 07:02 AM

That looks like bare metal. IIRC, the Bendytoys used iron for the keel material...and having exposed metal like that is bad.

When you did the work last year, did you drop and re-bed the keel or just work on it as it was? If you didn't drop the keel, inspect the bolts and re-bed it, you should probably do that now.

donradclife 03-21-2010 08:33 AM

Is the keel lead or iron?

Bene505 03-21-2010 09:21 AM

The keel is iron. I wire brushed back down to bare metal yesterday to see what's going on.

I do have some rust around the keel boats -- It may be becasue I left water in the bilge all year. With several compartments, all the water in the bilge doesn't get pumped out. And rain from the mast gets in too. Since being on the hard, I made rain catchers that catch the mast rain water, and I use a shop vac to get it completely dry.

Stainless bolts, by the way. I plan to follow Beneteau's recommendation to pick a random bolt each year and check it. (Normally Beneteaus have galvanized bolts.)

So it is Silkaflex?


sailingdog 03-21-2010 09:31 AM

I'd use sikaflex but it is probably 5200.

Bene505 03-21-2010 09:36 AM


Is 5200 rubbery? The stuff I pulled out yesterday was like a (rough) string of rubber.


Gene T 03-21-2010 10:29 AM

Don't panic. I just went through this with my boat and did a lot of research on the issue. This is normal for anyone who owns an iron keel. Use 5200 or 4200 (probably better as it sets faster) on the joint. The keel will work as you sail so you may need to do it every time you haul out. It is just the curse of the builder and is one of the one weak points in the design. You could get the yard to move the keel block to the aft of the keel, thereby opening the gap up a bit more. You could then get some sealant in there further and it should last longer.


sailingdog 03-21-2010 11:36 AM

Yes, it is pretty rubbery, but not very stretchy. :D

Originally Posted by Bene505 (Post 583297)

Is 5200 rubbery? The stuff I pulled out yesterday was like a (rough) string of rubber.


Bene505 03-21-2010 11:47 PM

Dog - it was definitely stretchy.

I'm going to give Sikaflex a try. It's what Jomsviking recommended on the AS site.

West Marine doesn't have it in stock, so I'll look into getting somewhere else, tomorrow.

Meanwhile, I covered the exposed iron with.... ((drumroll please)).. duct tape. Add that to the list of uses for the stuff. It may have surface rust by the time I start wire brushing it again, Maybe with a duct tape covering it there will be less rust.

I was planning a West Marine rant when I drove away thinking "Why don't they stock the things in their catalog?" I also note that they don't have navigation lights for the size of our boat, and other things as well. And you have to really look to find the diesel fuel treatment (and they only had the biocide, not the stuff that takes water out of the fuel). (end rant)

Sikaflex. Now I just have to figure out what type & what size. 20 oz tube, I'd think, for resealing all the way around the keel with new sikaflex.


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