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Old 26-03-2010, 10:30   #1
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Question Encasing Steel Keel in Fiberglass

In the process of fixing up a 52 Dynamique. The keel is made of steel
and requires an epoxy tar paint. We have recieved advice to prep the
keel appropriately and then encase it in fiberglass to reduce the potential
for futher problems. Anyone have an opinion on this procedure?

Thanks in advance!
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Old 26-03-2010, 10:46   #2
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Myn guess is that the potential for water to become trapped between the fiberglass and the steel keel would result in all sorts of corrosion and fiberglass probems. Interested to see what the experts here have to say.
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Old 26-03-2010, 11:20   #3
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My keel is faired and epoxyed.. Glass is for structural and there is no need for it on a keel.. The epoxy is a two part system from interlux..
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Old 26-03-2010, 12:15   #4
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A steel keel would have to be totally moisture free and sealed 100% with epoxy. Any water that would get between the sealer and metal would develop iron oxide, which would swell allowing more water to enter. A catch 22 situation.

If it's a bolt-on, you would have to remove the keel to totally seal it. Unless the boat's never been launched.
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Old 26-03-2010, 15:35   #5
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steel keel

A steel keel is no different from a steel boat, and all the major paint manufacturers have epoxy systems for steel boats. They all involve sand blasting first. Encasing steel with fibreglass would be asking for trouble, in my opinion.

Best, Bob S/V Restless
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Old 26-03-2010, 15:40   #6
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Ditto that.

I don't know if I would use the coal tar epoxy, there are other treatments.

I have been using Ameron 302 zinc epoxy. It is mostly zinc, followed by concrete, then epoxy. That is topped with their 370 two part epoxy top coat. So far so good but I have mostly been doing spot treatment over the past three years.

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Old 26-03-2010, 16:17   #7
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When all else fails there's ...

When all else fails you could try International Primocon (or similar vinyl based, aluminium filled, primer).

The problem with steel in sea water isn't really rust as we know it (I think it's related to the small amount of oxygen in the water), it's electrolysis, and the problem with solutions like fibreglass sheathing is that there is no way to check what is going on. I'd even worry about the fibreglass forming one side of a battery if sea water got under it.

I'd go with what has been suggested here (good quality epoxy based primer) but on the outside below the waterline I'd suggest considering following it with Primocon (or similar) applied according to the manufacturer's recommendations.

On the inside I went with primer followed by generic epoxy resin to fill any voids, lows or hollows so that the very slightly salty water that gets into a steel boat flows down into the bilge. I did pour a good thick layer of epoxy into the bottom of the bulge and ran it up the sides a bit. So far this looks to be working OK...

Above the water line I'm trying a product called Penetrol CIP which is advertised as penetrating through the rust to give good protection. It's not advised for below the waterline use (too soft) though. I've found I need two or more coats though, and to allow it to dry properly before overcoating. So far it's not too bad...
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Old 26-03-2010, 16:21   #8
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Keeping epoxy onto metal is difficult enough without any fiberglass. For steel, sandblasting is the regular prep method but I believe you can etch it too (like aluminium).

I kept loosing the fairing on my lead keel and finally got it right using the tips from West System. After thorough cleaning you coat a square foot with epoxy resin and then use a steel brush to brush the epoxy into the lead, after which you continue with the next square foot. I am positive this method will not work with steel.

So ,for DIY on a steel keel, I would use the etching primer.

cheers,
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Old 27-03-2010, 15:35   #9
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Thumbs up

Thanks for all the great advice.

Just to clarify it is a steel keel on a
fiberglass boat. I will post the method
used for sealing once we move forward.
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Old 27-03-2010, 22:40   #10
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Wink Just a note

Steel keels are more common in Europe then the US. I wonder what European manufacturers do/use?
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Old 27-03-2010, 23:53   #11
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If you are referring to a cast iron or steel keel bolted to a fiberglas hull, I would say that sheathing it in fiberglas is going to cause more problems than it solve. I had a cast keel on my Grampian, which was spalling badly when I bought it. So I started chiseling off the filler and found that the pits were upwards of 4 inches deep in spots. I ended up grinding down to raw metal, and filling the voids with 'Muffin Mix' which was west system epoxy with sawdust as filler. ( it looked like muffin mix). This was then smoothed with a disk grinder and final finished with a belt sander. After that was done, the entire keel was painted with Interlux epoxy, two coats. Then the bottom paint. That material held in place for 6 years thru northern ontario winters and summers. I ended up filling some small cracks after the 6th year and it was still going strong.

If anyone wants Im willing to post some photos of the work.


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Old 28-03-2010, 06:34   #12
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Primocon Interlux - NOT

Used it twice, the second time because after the first failure I thought I had not cleaned the steel thoroughly. Cast iron keel.

It may be a good stuff but my choice will be epoxy. I will not use Primocon on my boat ever again.

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Old 28-03-2010, 13:16   #13
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Cascades use fiberglass over steel keels. Mine lasted quite a time before I had to grind down to steel again and reglass. Proper steel prep prior to recoating is the key but can't help you with that procedure as I'm still hauled out and don't know the result of my latest.
kind regards,
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Old 04-04-2010, 04:53   #14
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I own a steel boat. If you want to do the job right, sand blast the keel and use a zinc rich primer. Do not cover it with fiberglass! There is no point in that, it would be a waste of time and money. The Ameron 302 would work as a primer. Follow that with at least two coats of Ameron 235, more is better. Then apply the top coat if you wish, or just stay with the 235. If there is no flaking rust on the keel, I think you can probably get by with a good power wire brushing of the keel and not have to sand blast it, followed by either the 302 or 235. Most steel boat folks prefer the Ameron product line over Interlux and it usually costs less. Ask your Ameron dealer for the contact information of your local Ameron rep. He/she can tell you exactly what to do. My experience with the Ameron reps has been outstanding.

After re-reading this I realize I'm sounding very pro Ameron, so I guess I should also say I have no interest in the company, I just think they make a great product.

Regards,

Thomas
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Old 04-04-2010, 07:42   #15
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Quote:
Originally Posted by Boracay View Post
When all else fails you could try International Primocon (or similar vinyl based, aluminium filled, primer).

The problem with steel in sea water isn't really rust as we know it (I think it's related to the small amount of oxygen in the water), it's electrolysis, and the problem with solutions like fibreglass sheathing is that there is no way to check what is going on. I'd even worry about the fibreglass forming one side of a battery if sea water got under it.

I'd go with what has been suggested here (good quality epoxy based primer) but on the outside below the waterline I'd suggest considering following it with Primocon (or similar) applied according to the manufacturer's recommendations.

On the inside I went with primer followed by generic epoxy resin to fill any voids, lows or hollows so that the very slightly salty water that gets into a steel boat flows down into the bilge. I did pour a good thick layer of epoxy into the bottom of the bulge and ran it up the sides a bit. So far this looks to be working OK...

Above the water line I'm trying a product called Penetrol CIP which is advertised as penetrating through the rust to give good protection. It's not advised for below the waterline use (too soft) though. I've found I need two or more coats though, and to allow it to dry properly before overcoating. So far it's not too bad...
Electrolysis is a chemical change in the electrolyte (water). What you are talking about is galvanic corrosion. Galvanic corrosion will be enhanced by using an aluminum filled primer on a steel or iron keel. An aluminum filled primer will disintegrate and fall off the boat.
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