Keel paint

[baldbaby2000]

My keel on my Mac 25 is blistered. It seems bad enough that it's probably slowing it down. I don't want to do a lot of work. I'm thinking of taking a wire brush and sander to it to smooth out the big chunks, then prime it and paint with canned spray paint. Does anyone have any thoughts on the best type of paint to use.

Maybe next season I'll bottom coat the boat and keel.

[craiglaforce]

I don't have any experience fixing blisters but I've read that any reasonable fix is a lot of work. I would go back to last fall and hit the blistered areas with a sander. let dry in a covered area like a garage or at least covered with a tarp over the winter. now I would paint or fill the blistered area with a two part epoxy like West. Then follow with a good waterproof epoxy bottom paint and then antifouling layer.

Wire brush and a can of spray spray paint? - no.

You might want to visit a marina and see if they will quote some sort of fix if you don't feel inclined to do the work yourself.

[kmclemore]

I strongly recommend the following book on the subject.... I'd dare to say it is the definitive manual on blistering of glassfibre, as well as the proper construction and repair of boats. I'm fortunate to know a bit about glassfibre, having worked for Lotus Cars, Ltd., for whom I did a considerable amount of custom moulding in their Elan, Europa and Esprit lines.

Click HERE for the book, "OSMOSIS & Glassfibre Yacht Construction" by Tony Straton-Bevan.

The book, in fact, has an entire chapter devoted to the causes and cures of osmotic blistering in GRP, and another whole chapter on how to avoid it.

Cheers,
Kevin

(other reviews/notes about this book are HERE and HERE)

[Frank C]

My keel on my Mac 25 is blistered. It seems bad enough that it's probably slowing it down. I don't want to do a lot of work. I'm thinking of taking a wire brush and sander to it to smooth out the big chunks, then prime it and paint with canned spray paint. Does anyone have any thoughts on the best type of paint to use. Maybe next season I'll bottom coat the boat and keel.

Removing & repairing your keel is a pretty big deal, since it's a fiberglass covered steel plate that weighs about 600 lbs. The real answer will be a lengthy process to remove it and re-encapsulate it. I've read of other Mac 25 owners' keel repair jobs, and it's tricky business to get it out, and then reinstall it. By the sound of it, yours may also need maintenance of the pivot pin and winch.

Your temporary fix might be just fine to get you onto the water for this year, and I doubt it matters what kind of paint you choose. However, if the pivot pin is suspect, you could lose the keel completely ... that could make the boat a write-off. Check on a forum of Mac 25 owners for better answers ... maybe this one at sailboatowners.com, or this one at macgregorowners.com.

[baldbaby2000]

I'm pretty sure the keel is just painted cast iron. When I scraped on it I only saw pieces of rust come off. No resin that I could see. How long does it take to rust out a keel in fresh water? I usually keep it in the water during the summer.

[Duane Dunn, Allegro]

That's surprising. Even my 1970 Venture (early Mac) keel was resin encased. I'd poke around a bit more and deeper to find out what you are dealing with.

[BobCardz]

My 25 was pretty rusted... I smoothed out the keel as much as I could with a rotary wire brush on my sander and then took a grinding disk on the same sander and smoothed it more. Use trilux antifoulant to painit. My boat was red so the white looked pretty cool under it.

Dont use copper based bottom paint on a cast iron keel.... It will only lead to more corrosion. Trilux will cost more but is made for painting metal surfaces left in the water.

If you're dry sailing it... I guess a barrier coat and hull paint will do.

[Tom Root]

That's surprising. Even my 1970 Venture (early Mac) keel was resin encased. I'd poke around a bit more and deeper to find out what you are dealing with.

Hmm, I have seen resin encased, but the two I have owned where totaly bare. I faired them, and ended up sealing them! DON'T use the rubber stuff called "dipit" (?) or Plastidip, the stuff you use for coating the handles of tools. It was expensive, and more labor intensive than resin, and it did not last very long. It was just an experiment anyway, but the first time the keel dragged on a cross brace on the trailer, it tore it all up! Then, since the leading edge was exposed, the action of going through the water ripped big patches of it off! I could just imagine this was like a "water brake" as resistance was increased by water filling up cavities created by the rubber, so not a good idea at all!

A good rust converter applied 1st really helps though, and I do not see any degradation on my keel of my '76 Venture 25' even though the rubber idea totaly failed!