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EricinToronto 04-21-2012 06:38 PM

Questions about barrier coat on steel keel, and sealing keel joint
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Hello everyone,

I have a 1973 Grampian 26 (Wind Dancer - Hull 604) we keep in Lake Ontario. I am in the process of applying a barrier coat of epoxy to the steel keel. We - my boat partners and I - noticed when we bought the boat that the keel was 'bubbly' in certain areas - the previous epoxy was ruptured in small patches, and flaking off. Nothing too serious, but it looks like something we didn't want to leave too long. So we decided this year to scrape the steel keel clean and re-apply a barrier coat.

About 80% of the epoxy looked fine, but there were patches where the expoxy had been compromised and was letting water in, to rust the keel. A grinder and some 36 grit disks - as per Don Casey's instructions in 'This Old Boat' - got us to bare metal in about a day. We still need to remove small dime-sized patches of epoxy, brush and clean with solvent, and we should be ready to put on several barrier coats.

While I have epoxied a bare fibreglass hull before, I wanted to get some second opinions about a few specifics of this job. Here goes:

- I understand that we want to apply the epoxy to bare, clean metal wherever possible. But we have a specific area in the middle of the keel, where the keelbolts are, that has a thick coat of epoxy that appears to be good. This extra-thick layer runs between the keel and the fibreglass hull. My plan was to apply the epoxy to this existing coat, sanding and cleaning the older epoxy layer to get a good bond with the new. I am concerned about removing what appears to be a good coat, and potentially messing up the fibreglass/whatever sealing work the previous owners did.
My question: can I apply a new coat of epoxy over sanded/cleaned epoxy and get a good seal? Or will I get water infiltrating between the two layers? Do I need to sand down to bare steel and bare fibreglass?
- There was a strip of sealant added where the steel keel and the fibreglass hull meet. In most places, it was compromised and allowing water to seep in. My understanding is that I need to removed the old sealant, clean/scrape the surface and apply 3M 4200 or Sikaflex 291.
My Question: Do I clean the area and seal the joint, then epoxy around (not over) the sealant? Or can I epoxy over this sealant?
- Don Casey recommends Interprotect 2000E for this type of barrier coat. Any experiences with putting a coat of 2000E on a steel keel, or West System epoxy?

Thoughts on POR-15 to inhibit rust?

Any advice in dealing with the stell keel / fibreglass hull join? Any advice or cautionary tales appreciated.

Pictures of the keel joint and the thick epoxy around the keel attached for reference.

SloopJonB 04-21-2012 09:43 PM

Re: Questions about barrier coat on steel keel, and sealing keel joint
I've cut & pasted a reply to a similar question about sealing iron keels.


Originally Posted by matjay
From the research I've done it seems to me the best approach is to sandblast the keel white, then immediately apply a base layer of epoxy. Any recommendations as to what to use for the base layer? Is something like WEST systems alright, or is a zinc enriched epoxy necessary?

A - Sandblasting is correct - any grinding method will not clean ALL the pitted areas fully and future failures will start there. Just use regular epoxy resin as a seal coat - nothing fancy, just get it on right after blasting and a solvent wipe. You can't even leave this step overnight. West is only more expensive - 4 times as much as the industrial no-name resin I use. Stone fabricators - counter tops etc. use a lot of epoxy - check around and you'll save $hundreds.

Moving on to a filler, again is WEST ok? and how many coats is recommended?

A - Again, West only costs more. Get a cement bag of industrial talc for about $20. It makes the most beautifully sanding filler you have ever experienced. Mix it to peanut butter consistency with epoxy and you probably won't even have any pinholes to fill after sanding.

Many people claim to use a notched squeegee or trowel to apply the epoxy, and then fill in between the created lines? is this necessary?

A - This makes it MUCH easier to get an even coat. Unless you're an experienced plasterer, using a plain trowel will give you a very uneven thickness. You do NOT want to sand through to metal, ever, or you will have to start over there. You want a reasonably thick finished coat - 1/8" min. is my preference - in order to ensure the metal stays buried.

Get an autobody longboard sander - they look kind of like an old smoothing plane, about 18" long and take pre-cut strips of sandpaper. This will help you fair up your keel - mine ended up looking like it had been templated.

I finished mine off with 3 coats of epoxy resin and 3 coats of Interprotect (there was still discussion as to the best sealer at that time). Now I'd just use Interprotect for all coats.

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