Keel Fairing

[BarryL]

Hello,

So, after the soda blaster guy finished removing the old bottom paint, the keel looks like this:



It looks a little better after sanding, but needs a lot of work.

I know that I need to add material to fill the low spots, shape the leading edge, etc. Then I need to fair it smooth, and finally paint it.

What material do I use for filler? This is not structural, just for shaping. Is automotive bondo ok? If not, what sort of inexpensive low density stuff do I use? After the keep is smooth, I will apply a barrier coat.

Should I apply a barrier coat first, then apply filler, then barrier coat it again?

Soon it will be warm enough to start work!

Barry

[sailingdog]

You can use thickened epoxy. Don't use the colloidial silica or microballon filler. I'd recommend using the chopped fiberglass filler. Sand through the gelcoat and apply the thickened epoxy to the fiberglass. After it cures, wash it down with water and a scotchbrite pad to remove the amine blush, sand it fair, and then apply the barrier coat.


One question—is the grey and red/brown coloration remaining bottom paint??? If so, then the guy did a really lousy job. If it bottom paint, you'll need to remove it all, down to the gelcoat. BTW, it looks like there is some crazing or alligatoring of the paint or surface. Is that in the gelcoat or just in the remaining paint??

[ewebster]

I am just now researching the products and methods for the same project on my boat. It seems that each finish product will have its own recommended steps, products, and procedures to ensure proper adhesion and longevity. I am considering Awlgrip for the topsides and they have a whole set of "directions" available. Haven't researched bottom paints but don't skimp as the labor is the big expense! Bondo absorbs water as does raw fiberglass resin. Find something else! Check online at Anzam Yacht Refurbishing for a great article on how-to Painting Topsides. It has some wisdom that will apply tothe bottm as well. Good luck....

[sailingfool]

Absolutely the only way to go for keel fairing is West Systems epoxy products and fillers WEST SYSTEM Epoxy , 410 Microballons in your case. There is a lot of info on their site and you can order a relevant book or video from their Instructional/video page.

Also be sure to get a 3M long board and velcro sanding pads for sanding, see 3M Marine Hookit Fairing Longboards 4-1/2 inches wide x 30 inches long . Very expensive but you want to do this job only once and do it correctly.

[sailingdog]

SF-

I'm not a big fan of microballoons for this purpose, as the microballoons are hollow and can absorb water. However, the longboard sanding blocks are a godsend to getting the keel fair.

[BarryL]

Originally Posted by sailingdog

One question—is the grey and red/brown coloration remaining bottom paint??? If so, then the guy did a really lousy job. If it bottom paint, you'll need to remove it all, down to the gelcoat. BTW, it looks like there is some crazing or alligatoring of the paint or surface. Is that in the gelcoat or just in the remaining paint??

The white is gelcoat. The The light gray is what is left from the previous barrier coat (Interlux 2001). The dark gray is metal keel showing. The red is antifouling paint.

Thank,
Barry

[sailingdog]

In that case, he did a pretty crappy job IMHO. Either he should have left the barrier coat alone or he should have cleaned it all off. Is the crazing in the gelcoat??? or just the paint?

[BarryL]

Originally Posted by sailingdog

In that case, he did a pretty crappy job IMHO. Either he should have left the barrier coat alone or he should have cleaned it all off. Is the crazing in the gelcoat??? or just the paint?

I think the guy did a very good job. There was about 20 years worth of paint on the hull, on top of the original barrier coat. I don't know if the barrier coat was properly applied. The pic at the bottom is the original bottom paint. You can see where large chunks fell off. In other parts the barrier coat adhered very well and the soda blasting didn't touch it. In other places the barrier coat came off.

The alligator effect is places where the barrier coat came off in small strips. The gelcoat is fine.

Barry

[jimmyb116]

I am doing just this starting Friday except I will sand the bottom paint off with a large porta cable random orbit sander. And then fair the lead keel and bottom and re-bottom paint. I am going to use west system for the barrier coat and fairing compound, I have used this system before with good results. Best of luck its a messy job but worth it in the end. I second the 3M long board great tool.

[KeelHaulin]

Barry-

Go to the MAS website; they have a formula for mixing fairing compound. If you only use glass strand it might be too tough to sand smooth. When you mix the filler you are going to whip in a bunch of air anyway so I don't see a huge issue with the microbaloons or silica. The thoroughly mixed epoxy will prevent water penetration into the filler materials.

Sand the fairing compound within 24-48 hours after it sets. If you don't it might be tough to get it to sand flat to the hull. Don't sand off all the paint that is still on the keel; it is more difficult to get the new paint to stick to the lead than the old paint. Scrub the areas of the lead where it is exposed with scotchbrite and immediately apply some barrier coat paint (or epoxy).

On the rest of the hull; be sure that all of the anti-fouling is removed. If there is some barrier coat paint I don't think it will matter much since you will be applying a new barrier coat anyway. If you are going for a racing bottom finish you will probably want to sand the barrier coat smooth before topcoating with a smooth finish anti-fouling paint.