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FK Hull Keel Seem

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bigelowp
Master Marine Consultant

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USA
1813 Posts

Initially Posted - 03/03/2007 : 13:31:17

As I begin work on the bottom of my FK/TR I have a couple of questions regarding the keel. Being a typical 1980 FK hull, the keel is not encapsulated and I believe it is "bare" metal bolted onto the hull. The first question is regarding spot priming. I will not be racing (or at least prepping the bottom to racing quality smoothness) but have been chipping away on layers of bottom paint with most coming off easily. The paint on the metal portion of the keel either does not come off or when it does it comes off to the often pitted metal. Should I be spot priming the metal keel before applying bottom paint? If so, what should be used -- is it as simple as Rustoleum primer or is something else called for? Second, their is a hairline crack along the seem between the fiberglass and metal keel. The crack covers @25% of the seam and is primarily on the leading edge. I have checked the keel bolts -- and then had them checked by a professional -- and they seem to be alright. The yard thinks that because the previous owner was careless (clearly so looking at the condition of the boat and keel bottom) and because the boat was sitting on the hard for several years, the hairline crack is cosmetic only. My question is should I be faring it? If so, with what -- it is truly hairline and the bottom paint might even fill it -- but I would not want to rely on bottom paint especially as I will be using ablative paint. As always I welcome any comments/criticisms/suggestions.

Peter Bigelow
PO - C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 03/03/2007 : 14:41:18

I'll offer a couple of suggestions--others might have better ones...

For the cast iron, I'll recommend a "rust reformer" rather than a primer--in my experience, it does a better job of stopping or preventing rust. It's only effective on bare metal--rusty or clean. Rustoleum makes one version, or used to. It has an acid in it, so keep it off your skin. (It's not that dangerous--mostly just turns your skin black.)

And then the Catalina Smile... If the crack is truly a hairline, then most any caulk might be just fine--5200 might be best. If it's 1/8" or more, I might suggest Marine Tex--it's sorta like automotive "body putty", and would also work for filling larger pits in the keel. Keeping the seam sealed is a good idea--it could help retard the corrosion of the keel bolts.

Edited by - Dave Bristle on 03/03/2007 14:43:55

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 03/03/2007 : 17:50:09

I got this stuff at Home Depot labeled "Rusty Metal Primer" did NOT require clean metal to work. It is red. It worked really good on my Coronado 15 trailer. It bonds really well to rusty metal and converts it chemically. I would use it. Paint over with your favorite bottom paint.

The "Catalina Smile" is the well-known crack you are speaking of at the leading edge of the fin. It is generally not serious, only cosmetic. If it is more than a hairline I'd second the Marine Tex epoxy.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 03/04/2007 : 10:33:49

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JimB517
 I got this stuff at Home Depot labeled "Rusty Metal Primer" did NOT require clean metal to work. It is red. It worked really good on my Coronado 15 trailer. It bonds really well to rusty metal and converts it chemically.<hr height="1" noshade id="quote"></blockquote id="quote">
Sounds like another version of the "rust reformer" I was talking about--so that's two votes for it. The Rustoleum version is sorta like milk that you wipe on. It dries clear and hard, but turns any bare metal (rusty or not) black, and seems to stop the rust progression cold. It's intended to be painted over.

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/04/2007 : 11:16:15

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Bristle Sounds like another version of the "rust reformer" I was talking about... It dries clear and hard, but turns any bare metal (rusty or not) black,...
<hr height="1" noshade id="quote"></blockquote id="quote">I think the common ingredient is phosphoric acid. It converts any iron oxide (rust) it can get at into iron phosphate (or something like that), which doesn't seem to react with much of anything. I would keep in mind this iron phosphate (or whatever) is a thin fragile layer, and easily breached. I usually protect it with a few coats of epoxy resin before painting. On my swing keels, I also wrapped the keel in a couple layers of fiberglass cloth to resist minor abrasion, such as craptrap lines, small shells on seagrass, enthusiastic pressure washers, etc.

-- Leon Sisson

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thaind
Navigator

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Canada
145 Posts

Response Posted - 03/18/2007 : 10:29:56

I had a similar problem with my 78FK. I sand blasted the area (Keel only not Fiberglass) treated with one of the phosphoric acid treatments Leon reffered to, and used a fibrated marine acceptable Bondo TM to fill. Treated underwater area with the Interlux 4000 barrier, and then bottom paint.

I suspect that the problem in my case was caused from the inside out. The PO had drained the galley sink into the bilge??? Whether it was this or not, the plywood stiffener/thickener had become wet, frozen in the winter and expanded creating numerous leaks on bottom of bilge into plywood, and causing instability with keel/boat junction, hence the crack around much of keel junction. The keels are realy rough and there is a lot of filler in this area from factory. I perforated from the bilge into the ply fiding numerous wet spots, let it dry and vent for a few months in my school shop, and saturated/sealed the area with one of the realy thin epoxies. I had to soak the area at least four times as it soaked into the wood. That was two winters ago, and it has all remained intact.

Edited by - thaind on 03/18/2007 10:31:07

bigelowp
Master Marine Consultant

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USA
1813 Posts

Response Posted - 03/26/2007 : 22:00:09

Thanks for everyone's input. I found the Rustoleum -- the "Rust Reformer"m is a spray on paint -- clear going on then fizzes and ends up matt black. I also bought the Rustoleum "Heavy Rust" primer, which brushes on and is red. I did the worst and what appeared to be critical areas with the spray and brushed the rest. I am using 3M 5200 quick dry in the very fine crack. My game plan is to use ablative paint. The first coat, which will go to the top of the boot stripe -- will be black with the second coat which will be lower than the first coat to leave a three inch boot strip -- will be blue. The good news is, worst case, I can do a quick launch so no one needs to see the final result if it does not look good!

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