G/Flex, Flexypoxy for Keel Hull Joint? - SailNet Community

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  #1  
Old 06-21-2010
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G/Flex, Flexypoxy for Keel Hull Joint?

I've removed all the sealant in the keel hull joint (I'm not dropping the keel this year.......that requires cutting out the floor and pulling the mast -- negatory) and was originally planning on sealing it with 5200

keel is cast iron, flanged (as in it's through bolted into the bilge, not cast in j-bolts)

after some reading/research and speaking with West Systems -- I'm now considering a few options:

1. only seal joint with 5200 (caulk immediately after final wire brushing of iron)
2. seal joint with 5200, grind back 2-4" above joint on the hull and 2-4" below joint on keel and glass over sealed joint using glass laminted with G/flex Epoxy
3. seal joint using thickened G/flex Epoxy, grind back 2" above/below joint as well
4. seal joint using thicken g/flex and laminate over it with g/flex glass

also interested in pettit's flexypoxy -- also looks good -- but I called both West's and Pettit's tech support line, at West got someone knowledgeable -- an engineer and at Pettit got someone with ****** who didn't seem to know much more than the product spec sheets, so I'm leaning towards West

my gut says 5200 + gflex glass, but I'm considering an all G/flex solution, keel is a fin and I know it moves some so obviously need something flexible


anyone have real world experience with either G/flex or Pettit's Flexypoxy?

Pettit Spec Sheet: http://www.pettitpaint.com/fileshare...ds/1707628.pdf

G/Flex Info: G/flex Epoxies

Thanks!
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Old 06-21-2010
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I don't believe a keel/hull joint should move. The surfaces of the keel top and mating surface should be a perfect match. Many builders use epoxy putty of some type to fill in any gaps when the keel is attached. Builders like Hinckley will work hard to make the 2 surfaces a perfect match by planing the lead until it is perfect. Then a layer of sealant is applied most of which will squeeze out as the nuts are tightened. But they are a rarity. Once the keel bolts are torqued properly there should not be any movement. If it moves a little, over time it will get worse. But I don't think a proper job can be done without dropping the keel. Sealant is designed to keep out water but not to fill gaps that shouldn't be there.
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Old 06-22-2010
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If the keel is iron, you really need to coat it with some sort of protective coating, rather than just wirebrushing it and mounting it as it seems you're planning on doing. Usually, this involves priming the cast iron and then putting an epoxy coating over it of some sort. If you don't do this, and the cast iron starts to corrode, it will cause damage when it expands by 10% when it rusts.

You will need to bed it in some sort of sealant. 5200 could be used. I wouldn't use an epoxy in this situation, except possibly to fair the joint.
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Old 06-22-2010
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You're right, the keel isn't supposed to move -- but I'm pretty sure it does a little as that's where the crack in the old sealant came from, I've re-torqed the keel bolts so hopefully that keeps it a little tighter but it's a 43 year old boat, so I'm sure there's some give there -- obviously the best solution would be to drop the keel and use epoxy to match the bottom of the boat to the keel, but that's not happening this year

the old sealant had pretty much given up the ghost (no idea how old), it just pulled out of the joint for the most part in tact or at least in long strips, so I'm going to replace that and possibly add some insurance with a layer of glass around the joint (it's what beneteau and hunter do in this situation....seeing as they make a lot of bolted on fin keel boats seems like a good idea), after speaking with a tech at West the glfex sounds like a good idea as the epoxy to use in that glass

dog I agree, I think some epoxy before 5200 is a safe bet....at least I can wire brush through the epoxy to remove any flash rust once I apply it and be sure that there's a healthy bond there, the only issue is I can't get all the way into the joint with a wire brush, not even on my dremel but I can at least get into the first half of it
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Old 06-22-2010
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I've used 5200 for that application with good results.
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Old 06-22-2010
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Jimscal,

how did you treat the joint before applying 5200?

Thanks!

Brian
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Old 06-22-2010
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There is a lot at play here. Bedding the keel to the stub- 5200. The joint will always have some movement in that fiberglass and iron or lead expand or contract at different rates. Any hard fairing compound that bridges the joint will have a tendency to crack in this area which is different from separating. Guys near me have ground out a 2" wide trough along the seam with a dremel. The laying in a layer of glass tape with gFlex epoxy and then add a layer of Gflex/ silica fairing compound. Sand to a fair surface, barrier coat and you are good to go for several seasons.
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Old 06-22-2010
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POR 15 and 5200. I wouldn't glass over the joint.
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Old 06-22-2010
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Sandusky -- I was thinking about something similar, g/flex's flexability/strength is particularly interesting for this type of application -- I'm leaning towards 5200 the joint but grind it back back in a slight V maybe 1/8" deep 4 inches up the boat and 4 inches down the keel and then glassing over with two thin layers of cloth saturated in gflex, it's kind of a compromise, the joint it self is still sealed with an adhesive sealant, and that sealant is protected with a layer of flexible glass

anyone else have any experience with G/flex?
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Old 06-22-2010
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Quote:
Originally Posted by brianontheroad View Post
Jimscal,

how did you treat the joint before applying 5200?

Thanks!

Brian
Just scraped and sanded the joint, applied the 5200 with a caulking gun, and smoothed it over to create a fillet. Lasted for years.
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