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Old 02-01-2011, 10:21   #1
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Keel to Hull Joint

Hi to all,some opinions would be wellcome, The lead ballast joint on my Cheoy Lee os 47 was showing signs of age so have raked out what i can of old bedding compound ,leaving what looks like a f glass gasket ,from what i understand the hull would have been lowered onto precast lead ballast using compound on both sides of gasket to take up imperfections between hull and lead, approx 5 yr ago i raked out joint and filled as best with sikaflex. This haul out i noticed it needed repairing as after pressure washing some blasted out.any suggestions on different repair method or stick to sika.Thanks.
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Old 02-01-2011, 10:29   #2
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What does the yard expert say or recommend? It's hard for anyone to say without being there. This is not something you want to make a decision on from guesses by people who are not there to see it in person. If the yard does not already have an expert there to examine it, then you will need to hire someone like a surveyor to see it in person.
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Old 02-01-2011, 10:30   #3
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Just gotta ask is this superficial or is the joint working and causing the seem to open. Can you take up on the bolts from inside. If you relieved the bolts and lifted the hull I would think 5200 the best. If it is superficial then epoxy and cabosil would be fine.
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Old 02-01-2011, 10:46   #4
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Just an opinion... I would use a polysulphide (Like boatlife) instead of a polyeurathane (like sika & 5200) It should remain flexible longer and still create a watertight seal. The joint is not held together by the caulk, so using a bonding substance is not necessary. You just want to seal it, and you don't want it hardening and cracking. Polysulphide should accomplish this.
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Old 02-01-2011, 10:49   #5
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The reason the seal is cracking is because the keel is moving in relation to the hull. Stuffing the crack with sealant may be putting a Band-Aid over the real problem that your keel may be too loose.
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Old 02-01-2011, 11:01   #6
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The reason the seal is cracking is because the keel is moving in relation to the hull. Stuffing the crack with sealant may be putting a Band-Aid over the real problem that your keel may be loose.
That's certainly a possibility, and I agree with your statement about us (forum people) not being there to see it in person and therefore cannot give definitive advice.
I'm certainly not a professional, so don't take my advice as facts, but i have this opinion based on doing a bit of research recently on this subject for my own boat.

With that said... It's not too difficult to tell if its just dried caulk falling out, or if the keel joint is widening; if the keel bolts are failing; or if there is water coming into the boat from the keel. If you cannot tell the difference or assess these things confidently, then I would totally recommend having a pro look at it.

Otherwise, if it's just caulk falling out... its a perfectly normal 'problem' on boats with external ballast/keels. It's not a structural issue, and not usually even about the keel having movement. It's just old caulk... Stuffing the crack with sealant is precisely the method used to 'fix' this.

If you are having other issues like mentioned above, then you will need to drop the keel, fix whatever the problem is, then completely rebed the joint. In which case, I would still recommend polysulphide for the sealant :P
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Old 02-01-2011, 11:11   #7
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... Otherwise, if it's just caulk falling out... its a perfectly normal 'problem' on boats with external ballast/keels. It's not a structural issue, and not usually even about the keel having movement. It's just old caulk... Stuffing the crack with sealant is precisely the method used to 'fix' this.
If you are having other issues like mentioned above, then you will need to drop the keel, fix whatever the problem is, then completely rebed the joint. In which case, I would still recommend polysulphide for the sealant :P
Cracks along the hull-to-keel joint are common in fin keel sailboats with an external ballast fin keel. Most fin keel sailboats develop, to a greater or lesser extent, a crack at the cosmetic fairing putty at the keel-to-hull joint. If the crack gets big enough to see daylight through or you have a leak at a keel bolt, you should check for proper torque of the keel bolts. Regardless, it's good practice to tighten keel bolts to the proper torque specs every 10 years. I doubt the material you mention contributes in any way to the structure of the boat. Rather it's a layer of fairing putty put there to streamline the joint. Repairing it is a beautification project only and, for the rabid racers, a perfectly faired keel can mean a nanosecond of improved performance on the race course. Separation at the joint has no bearing on water getting into the boat, unless it gets past the sealant at the keel bolts and into your bilge.

If you decide to fix the crack and the loose filler, grind off or chisel away any poorly adhered filler and replace it with flexible sealant like 3M 101 or Boatlife Life-Caulk (both polysulfides) , or a polyurethane adhesive sealant such as 3M 4200 or Sikaflex 291.
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Old 02-01-2011, 11:37   #8
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Gord is correct. I assumed that Carl is looking directly at the bare joint without fairing.

Here's a photo of mine, where you can see both the joint that has no caulk in it, and the cracked fairing compound over top.



The course of action I decided to take is to remove all the fairing compound, dig out any caulk (if there is any) and completely clean and remove anything else. Then caulk the actual joint with sealant (personal preference), then re-fair the keel over top of that (to make it pretty).

The cheap thing to do would be to just removing the cracking stuff, and fair it back out. Or even remove all the fairing compound and just caulk the joint and paint it My choice is to take it down to the joint and seal it, but either way it is entirely superficial.
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Old 02-01-2011, 11:49   #9
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Just an opinion... I would use a polysulphide (Like boatlife) instead of a polyeurathane (like sika & 5200) It should remain flexible longer and still create a watertight seal. The joint is not held together by the caulk, so using a bonding substance is not necessary. You just want to seal it, and you don't want it hardening and cracking. Polysulphide should accomplish this.

I did mine this way last year. It still "cracked' ,and no the bolts are not loose. I just didn't want water to work it's way into ther joint. But if you take a tour though the yard a keel-to-hull crack is common.
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Old 02-01-2011, 11:50   #10
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I don't disagree with other posts on this matter--you need to determine whether there is anything structural going (probably not) on first--keel bolts up tight while weight on the keel and then checking for gaps in sealant. That resolved, I have eliminated the crack in a couple boats I have owned by grinding the seam back (you need to do this anyway to see what is in there) a bit and then sealing the whole thing with carbon fiber tape with some hard fairing compounds in the epoxy. Not a big job. Has held up well.
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Old 02-01-2011, 12:32   #11
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As David M suggests you need to confirm whether this is cosmetic or structural. If it is cosmetic by all means just slap something over it from time to time. But if it is structural and the keel is flexing, you'll need to drop the keel, clean out the joint, fix the problem, and rebed the keel.

If you rebed it with 5200 or a similar permanent adhesive, that's actually strong enough to hold the keel even without any bolts, so it is a rather permanent repair. Which has the mixed blessing of making any future repairs nearly impossible until you figure out a way to slice the 5200.
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Old 02-01-2011, 12:35   #12
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exactly like caamecrazy photo, no movement at all as said in thread blasted part of joint out with pressure cleaner. good idea to fair over sealer with epoxy ,will the epoxy adhere to sealant ok.
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Old 03-01-2011, 16:34   #13
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exactly like caamecrazy photo, no movement at all as said in thread blasted part of joint out with pressure cleaner. good idea to fair over sealer with epoxy ,will the epoxy adhere to sealant ok.

Epoxy will bond to polysulfide just fine, I don't know about the other stuff. You can even find 2 part epoxy-polysulfide adhesives out there...

Like Don said, the sealant is simply to keep the actual joint dry (even if it doesn't leak), the more water you keep out the better. You want it to be non-permanent so that I can be redone at some stage (hopefully many years later). I'd say the Fairing compound will give-way long before the polysulfide.... I think the biggest reason fairing compound starts cracking is that water is getting to it. It's not entirely waterproof... It needs a good coat of primer on top to seal it before you put the bottom paint on.
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Old 14-02-2011, 09:54   #14
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Gordan, You mention to have the bolts tightened to the proper torque. How do you find out what that is for a particular boat. Dave
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Old 14-02-2011, 10:01   #15
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Gordan, You mention to have the bolts tightened to the proper torque. How do you find out what that is for a particular boat. Dave
Bolts are tourqed by size and material, not by boat type.

Bolt Torque Chart | Portland Bolt
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