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Old 15-08-2010, 14:07   #1
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Do I Need a 'Barrier Coat' ?

I have a mahogany rudder on my boat that time, and water has attacked. I've put on numerous coats of West System epoxy to seal all the cracks that have occurred. Now that that is done, I need to put a layer or two of bottom paint on it.
Do I need to put on a barrier coat on the rudder to protect the epoxy or just sand lightly and paint the rudder and get on with my life? It's the first time working with this stuff and I'm still a bit green.
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Old 15-08-2010, 14:11   #2
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If its an epoxy with no cracks or dings that would allow water past it then no problem. If it is not sealed 100%, then I would apply three coats of an epoxy barrier coat and then apply the anti-foulant paint. Interlux 2000 barrier coat works very well at adhering to most all clean surfaces.
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Old 15-08-2010, 14:27   #3
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The epoxy surface will also have a bloom on it which will need removing before any other coatings will adhere to it. A pan scrubbing pad with soap and water will do with a bit of elbow grease. Do not skimp this stage or your paint will peel off.

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Old 15-08-2010, 14:31   #4
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Aloha,

A picture would be good in this case. If its a wood rudder without a fiberglass skin then you don't need a barrier coat or an epoxy coating. Just paint it. Cracking will occur when you haul out due to wood shrinking when dried out. Once your boat is back in the water those cracks will seal up again.

Of course I don't know your boat but if its like an H-28 solid wood rudder then the paragraph above applies. If it is a plywood rudder with a fiberglass sheath then David's answer is better.

kind regards,

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Old 15-08-2010, 14:34   #5
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The resin used in fiberglass in the long run needs an epoxy barrier coat. Epoxy is a true moisture barrier.
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Old 15-08-2010, 14:41   #6
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My rudder.

It's a simple solid mahogany rudder from my Laguna 26. As one of the post said, it was left out of the water for a few years and the wood had a chance to dry out--hence the small cracks in the wood. I've put a good 5 coats of epoxy (sanding lightly between coats)in it so far. I covered it to well above the water line and am covering the rest with several coats of urethane to protect what I didn't do in epoxy.
I take it from the last post that I need to take the shine off the epoxy and then paint it. At least I hope I understood what he wrote.
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Old 15-08-2010, 14:51   #7
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Then its good to paint.
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Old 15-08-2010, 15:42   #8
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Quote:
Originally Posted by mestrezat View Post
I take it from the last post that I need to take the shine off the epoxy and then paint it. At least I hope I understood what he wrote.
Yes, it will have a waxy finish, remove this then paint.
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Old 18-08-2010, 15:05   #9
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Continue with the epoxy coating, on the out of water areas. This is very important if you are going to get the true benefit of epoxy, which is encapsulation. Without encapsulation, the wood will change physical dimensions with it's environment (wet/dry cycling). This will eventually cause the wood to open more checks, splits and shear the plastic coating (epoxy) from the surface of the mahogany.

To avoid this, you must encapsulate the whole rudder blade. This will lock down the moisture content and stabilize the wood. Fully encapsulated wood doesn't experience wet/dry cycling, so the wood will remain pretty much as it is when coated. Naturally, dings, nicks and other damage to the coating should be fixed promptly or other issues will occur.

Once you've got the whole rudder embalmed in epoxy (at least 10 mils, which is a minimum of 3 coats of normal viscosity resins), it needs to be coated with varnish or polyurethane to protect the epoxy coating from UV damage.
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Old 18-08-2010, 16:27   #10
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Coats

I put about 7 coats on the lower 2/3s of the rudder so it is well covered way above the water line(then put on the bottom paint-2 coats) and then put an additional 6 coats of poly on the upper 1/3 overlapping the lower epoxy. Seems to have covered it well but I guess time will tell. This year, I plan to bring the rudder home versus leaving it attached to the stern.

Please keep in mind, I'm in a lake way up in the Colorado mountains--about 8,000 feet. The season ends at the beginning of October.
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Old 18-08-2010, 20:31   #11
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Aloha,
Get some paint on it and go sailing. Your season is short!
regards,
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