Cast iron keel maintenance.

[rbenyoung]

I have an accepted offer for a 1996 Oceanis 400, Today was the survey. The haul out revealed a keel with extensive barnacle growth. The surveyor said the required maintenance included sand blasting keel to bare metal applying epoxy barrier coat and bottom paint. My questions are is this expensive at a yard and how often is this required? My previous boat had a lead keel so
I am not familiar with iron keel issues.

Thanks

 

[Chief RA]

I had a Clipper Marine 26 with 600 lb cast iron keel. I found that maintenance was easy as it could be scraped down, sanded down or whatever and it was no problem. I only put ablative paint on it and no problem as cast iron does not rust much except on the surface. Chief

 

[DougM]

If you have the time and the equipment, it's not that difficult. It seems that there is a common defect in the coating of the cast iron keels in that the original coating begins to blister due to improper preparation by the supplier. I did the keel on my 323 last year after 8 seasons. The keel is either ground or media blasted to bare metal, and must be recoated immediately, before any oxidation begins to appear. Taking off the old coating with a grinder can be done but takes awhile to do it properly, and depending on your yard policy, they may not allow you to do it. There is no lead involved, but it's a dirty job. Steps must be taken to contain the old coating dust.

To recoat, I used several coats of Interprotect 2000 following the manufacturer's recommendations, followed immediately by 2-3 coats of bottom paint. The first coat of bottom paint as I recall was put on within a very short time window to insure a good bond between the Interprotect an bottom paint.

I believe others have had success doing small area repairs using Primocoat on the bare cast iron, then bottom painting.

 

[Captn TJ]

Soda blasting, 5 coats of barrier paint and anti fouling is the usual prescription for a badly fouled keel that is rusting. On going maintenance however can be limited to simple touch ups with barrier coat provided the initial work was done properly.

We've had cast iron keels on different boats for about 30 years and simple touch ups was all that was required. On the other hand we sail in the Great Lakes.

 

[SoSound]

We owned our 1990 boat for about six years. It had never been properly barrier coated until last spring. We just had the bottom paint redone when the diver told us it needed it. Last spring at haul out we were advised that the rust on the keel was becoming a more serious issue, so we had it stripped and barrier coated. We were out at the same time as another Beneteau which had been properly coated when new which had only a few VERY minor spots on the keel which needed touch up.

Stripping and coating the keel did not add that much to the cost of bottom paint project, but it did add a lot of time. It's a DIRTY/NOISY/HOT job and I wouldn't want to do it myself! Painter guy tried using sanding disks (yeah, right), then hard abrasive disks (have fun!), and finally went out and bought himself a needle gun (NOW you're talking!). It still took him a couple of days to do the job, and he's used to working in a tyvec suit, inside a plastic tent… I was glad I was paying somebody else to do it, and thrilled that they didn't charge extra for the effort required!

 

[SoSound]

A couple of pics of our project in progress last May.

After about a half day of needle gun:


The before pic:

 

[Gunni]

You are going to need to fair those pits with filler as part of your surface prep.

 

[GeorgeC1]

You are going to need to fair those pits with filler as part of your surface prep.

Why bother? Is there a reason other than cosmetic?

 

[Gunni]

Why bother? Is there a reason other than cosmetic?

It's your lifting foil. You need nice smooth laminar flow across your underwater foils if you want to get the speed, and pointing performance your boat is capable of.