[andreabax]

Hi all,

as I'm approaching the warmer weather I'm planning on how to repair the keel of my just purchased boat (a Granada 24).

On the very bottom the fiberglass was opened and there is some superficial rust. I opened it a bit more to reach all parts with rust and now I have a few questions on how to best proceed.

What I have in mind is:
- Remove all rust with either sandblaster or sander
- Clean all surfaces with acetone and let it dry
- Apply epoxy + epoxy filler and let it dry
- Sand it with 120
- Apply few fiberglass layers with epoxy to restore it (hopefully it will stick to the existing one)
- After that paint cycles as usual

Would that be correct or do you suggest to proceed in other ways?

Cheers
Andrea

 

[night0wl]

Assuming this is an iron keel.

Once you sand off the rust and get to bare metal, you should treat it with an inhibitor. POR-15 is what was used by my dealership when the rust spots appeared on my keel. It was handled under warranty.

You have the added complexity of re-glassing over your keel that I did not.
The procedure was this
1- strip off all old bottom paint
2- grind rust spots on keel back to bare, clean metal
3- immediately treat bare metal with POR-15
4- epoxy coat and fair the entire keel and hull with Interprotect 2000
5- two layers of PCA gold ablative.

 

[sailingfool]

After prepping, I would cover with two coats of straight West Systems 105 epoxy or similar, I find that finish much harder than Interprotect. I've finished lead keels with Interprotect, but for iron, you want the hard stuff. Then add a few layers of epoxy and glass, and fair the result.

 

[deniseO30]

More photos would help. It seems you have an encapsulated keel since i see glass being peeled off. Do you have keel bolts? Anyways.. what I've learned is the glass is the structure that is part of the hull and keel weight is cast to fit or poured into the hollow.

 

[SHNOOL]

I thought you couldn't do glass over epoxy... (I'm learning so don't take what I say as gospel)... but I thought only laminating resin, with fiberglass.

Epoxy over glass, but not glass over epoxy... Someone please clarify for me...

The picture seems to show fiberglass over a steel keel. I'll add that it looks like a very thin fiberglass layer too.

 

[Faster]

Yeah.. not enough glass there to be a true encapsulated keel..

Looks like a 'sealing skin' over a bolt-on keel. As such it won't be structural and you can grind it back to good adhesion and repair in kind. Sealing the steel/iron with epoxy immediately after cleaning it up is important.. as Neil Young said, rust never sleeps...

Not familiar with that design, but it looks like the rest of the line are typical fin keel/spades, so the odds are this one is too.

http://sailboatdata.com/viewrecord.asp?class_id=3916

 

[SloopJonB]

I thought you couldn't do glass over epoxy... (I'm learning so don't take what I say as gospel)... but I thought only laminating resin, with fiberglass.

Epoxy over glass, but not glass over epoxy... Someone please clarify for me...

The picture seems to show fiberglass over a steel keel. I'll add that it looks like a very thin fiberglass layer too.

You can do glass over epoxy and vice verse. What you are probably thinking of is secondary bonding - glassing onto a fully cured surface. Epoxy is far stronger than polyester in that circumstance.

 

[SloopJonB]

Hi all,

as I'm approaching the warmer weather I'm planning on how to repair the keel of my just purchased boat (a Granada 24).

On the very bottom the fiberglass was opened and there is some superficial rust. I opened it a bit more to reach all parts with rust and now I have a few questions on how to best proceed.

What I have in mind is:
- Remove all rust with either sandblaster or sander
- Clean all surfaces with acetone and let it dry
- Apply epoxy + epoxy filler and let it dry
- Sand it with 120
- Apply few fiberglass layers with epoxy to restore it (hopefully it will stick to the existing one)
- After that paint cycles as usual

Would that be correct or do you suggest to proceed in other ways?

Cheers
Andrea

I'm cutting & pasting an old reply on this topic.

Quote:
Originally Posted by matjay View Post
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?

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 - twice 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.

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

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.

Quote:
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?

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.

 

[paul323]

Looks indeed like a thin layer, too thin for true encapsulation. I'd also guess there are keel bolts.

I would grind away until you hit a solid glass/iron bonded area. Grind/sand metal until shiny, wipe lightly with acetone and then paint a layer of epoxy on *immediately* to seal the metal before any corrosion even starts.

Then you have a few moments to rest, in the confidence the metal is stabilised, and you have a good adhesive layer! You can then start layering on the glass cloth to build up the skin to full thickness; you may want to try something like twill weave around the curves, biaxial cloth to build up thickness. Depends on size, shape, thickness. Remember the cloth has the strength, not the epoxy, so don't flood it - squeeze out excess epoxy where possible.

When that is done I would sand and fair, then apply a barrier coat, then the antifouling.

Good luck!

 

[Sailormon6]

That doesn't look like an encapsulated keel. It looks like a cast iron keel that is faired with some kind of epoxy, to smooth out the roughness of the casting. My advice is that you not strip off all the old material down to the bare metal. Only remove the loose material. Any material that is still firmly attached after being in and out of the water for "X" years isn't likely to come loose anytime soon. You can find the loose material by tapping all over the keel with a steel hammer. Loose material will produce a dead sound. Firmly fixed material will produce a clear ringing sound. Mark the loose areas with chalk. Chip it away with a hammer and cold chisel. Use a wire brush attachment on your electric drill to clean the exposed surface of any more loose material. Immediately afterward, spray the surface with a rust reformer, just to seal it until you can cover it with epoxy. Cover the areas with an epoxy filler. I used Marine Tex. You'll probably have to apply it in about three coats to build it up. You might have to use a 4 1/2" grinder to grind down the high spots, because Marine Tex is very hard. Then you can finish smoothing it with a sander, and apply any good antifouling paint.

The most important final step took me twenty years to figure out. I had to repeat this process almost every year, because each year I saw big areas create big bubbles that lifted the fairing material from the keel. It appeared that something was causing gas to build up and collect in pockets under the fairing material. I asked myself what could cause that, and concluded that it had to be electrolysis. I installed a zinc to the keel, and never had the problem again.

 

[andreabax]

Hi everyone,

thank you for your comments. It'll be a hard job but sure I'm much more prepared after these!

It's indeed not incapsulated, so luckily the glass is not structural.

I'll keep you posted!

Andrea