cast iron ballast keel

[starbacca]

Has anyone had any luck sandblasting and sealing a cast iron keel? Is it worth the effort?

[Raka025]

I sure hope it is worth it Starbacca, or I have a bigger project ahead of me than I anticipate. Here are a few previous posts that go over the subject:http://www.woodenboat.com/forum/showthread.php?t=53590
http://www.woodenboat.com/forum/showthread.php?t=91858

Good luck and have fun with your project.

[ucb4ume]

I used to own a Cal-20 that had a cast iron bulb keel. It was a production fiber glass boat built by Jesen Marine in 1964. I owned it from 1984 through 1989. The boat lived in salt water in Long Beach, Ca. all of it's life. I pulled it out of the water for maintenance about once every other year.

The keel was "sealed" in fiberglass at the factory, but each time I pulled the boat out, I had to do some repair work on the keel where water had gotten behind the fiberglass.

We had a large fleet of Cal-20s in S. Cal. at that time, so we saw a lot of different kinds of repair on the keels. A lot of people would sandblast the keels in order to get a good surface for fairing. Keep in mind that if you sandblast cast iron, it will start to rust almost immediately. You must put some kind of protective coat on the bare metal within minutes of sandblasting. After sandblasting and priming, most people would fair the keel with epoxy and microballons.

You might google the Cal-20 fleet web site and see if anyone has any pointers for you. There are a lot of old Cal-20s out there. I'm sure they have delt with this issue many times.

[Jay Greer]

Yes, I have done it on many boats. After sand blasting, the most effective anti rust barrier to put on the metal, immediatly, is Dev-Con-Z. The product is a liquid galvanize that is 95% pure zinc. I recommend two coats to insure full coverage. After that I usually seal over the surface with epoxy resin. Any voids can then be filled with red micro balloons, sanded and given another coat of resin and a sanding prior to appying bottom paint.
http://www.rshughes.com/products/078143_12030.html
Jay

[Raka025]

Jay - I talked with a boat wright in CT who is originally from England about getting my ballast off, finally. He made the suggestion after sandblasting to build a nice fire under it and heat it up to drive out all the moisture that migrates in the porous steel. Then prime once cool enough to paint, as it cools, it will wick some primer in deeper.

What do you think?

[Jay Greer]

Well, I have never done what your boat wright suggested. I would be concerned with the soot and possible resin deposits that might result from building a fire under the iron keel. I would rather see a propane burner applied to it. Remember that the keel will begin to oxodize immediatly after it is sand blasted. It might be better to heat it first and then sand blast.
Jay

[Concordia...41]

James knocked Sarah's down with a needle gun. Took him most of the afternoon, but he was able to see what he was doing and we had the ballast keel back on, so he was doing it in place. It's not like we had the keel off for a couple of years and could have done it then or anything... :rolleyes:

We immediately sealed it and went through several rounds of building and fairing. I'll try to remember what he used. It was a really wicked two-part industrial stuff. He has a steel boat so had good connections and good experience. I really will remember the brand (or remind me and I'll call him).

The fire idea may have merit, but it seems problematic to dig a pit (or raise the keel) and keep all four tons of it supported all the while stoking the fire :confused:

The iron would be a good conductor of heat, but it'd heat from the bottom up and how long exactly does someone roast their keel before it is done :confused:

Then as Jay says it seems like there would be soot to contend with. :confused: I guess I just don't get it...

Congratulations on your progress though!

-M

[Raka025]

I am just throwing the idea out for comments as the logic and history as related was rationale.

The boatwright did say that they often did it with the paint still on. So sandblasting after the firing would be most logical. As far as the mechanics, at least in my situation, would be to build a cinder block furnace around it and not dig a pit. The frame holding the ballast is 5" welded pipe, so it is not an issue unless a little fire would melt the welds?

I think the issue that he saw trying to resolve was that cast iron absorbs water and even after sandblasting and priming, rust can start from within.

I'll get you pictures if I do it.

Jay - how much primer would you guess would be needed a Concordia keel?

[Jay Greer]

Since you are going to apply two coats, I would think a gallon should be enough.
If you have any left over, I should be easy to sell. This primer is the most effective I have ever used. It will stop hull bleeders as well.
Jay

[Canoeyawl]

Cast Iron does not absorb water

[Jay Greer]

There can be small voids in the surface do to inperfections in the pour.
Jay

[Raka025]

Cast Iron does not absorb water

Semantics.

It does rust though? Rust tends to be porous and retains water? Cast iron is not a sponge but, as Jay pointed out, imperfections in the pour can hold water. Water + oxygen + iron = oxidation.

The build the fire under the keel was a comment of the way things had been done in the past, it most likely was done prior to sandblast equipment? The other example Richard gave was a guy who recently sand blasted his keel, primed it, brought it back inside the garage and rust started to bleed through in short order. It may not have been primed correctly, the magic primer that Jay mentioned may not have been used...?

The other part of the comment by Richard was that they immediately, after a little cooling, added tar/pine tar or whatever they used to seal the metal so the pores that were in the iron would lose the water and fill with tar.

I thought it was a topic worthy of sharing.

[Raka025]

Since you are going to apply two coats, I would think a gallon should be enough.
If you have any left over, I should be easy to sell. This primer is the most effective I have ever used. It will stop hull bleeders as well.
Jay

Is it that expensive that I would want to sell a pint or a quart that is left over?:confused:

[Jay Greer]

The product runs $209.00 per gallon. So, I would imagine that you would want to sell any surplus left over. You might contact the supplier and see how quart prices compare to a bulk gallon. That way, you might have one quart left unopened when the job is done. Remember that this product will stop fastening bleeders as well.
http://www.rshughes.com/products/078143_12030.html
Asking a sales rep first might be a wise option.
Jay