Replacing Keel Bolt

Scott Pett · Post by **Scott Pett** » Sat Oct 01, 2005 6:39 pm

Having spent the last couple of hours separating one keel bolt from the bottom of the boat and now having also spent about two seconds inspecting the remains, it would seem prudent to replace it and probably the others, now that the time is right.

Judging by all the rust I guess the original was steel, maybe galvanized once upon a time.

The question is: Should I replace them with galvanized steel ones or switch to A4 Stainless?

Has anyone got any experience/opinions of this job and a potential supplier in the Solent/South Coast Area?

Cheers,
Scott

Bill Walden · Post by **Bill Walden** » Sat Oct 01, 2005 10:41 pm

Scott,

Keel bolts? What exactly are we talking about here? Does your boat have a "Jersey" keel?

Either way, Stainless is not a good choice for underwater applications as it is prone to crevice corrosion

Bill.

Ben · Post by **Ben** » Sat Oct 01, 2005 10:49 pm

I'm no expert but I think stainless is more likely to cause electrolytic damage to the wood around the bolt, that is why anode bolts are galv?

The chandlery at Emsworth Yacht Harbour has a range of galv bolts, can check on sizes at lunchtime one day as its very near work.

ian e · Post by **ian e** » Sun Oct 02, 2005 9:01 am

Whatever you do dont fit stainless under water. Stainless where protected by say the wood that it is going through is liable to corrode in an unpredictable way, this is known as crevice corrosion.For instance the outside of the bolt can to all intents and purposes look ok but the inside can have magically disappeared........ leaving no strength at all. In the same way you should resist the temptation to paint stainless steel as stainless remains stainless if air remains around its outside this particularly applies for instance to a boarding ladder dont be temted to antifoul the part of the ladder that is under water.

Scott Pett · Post by **Scott Pett** » Mon Oct 03, 2005 9:25 am

Many thanks all...

Bill - She doesn't have a Jersey Keel.

The bolts referred to are the ones coming up through the keel and hog and presumably protect the glue joint. They are coachbolts and are spaced about every two to three feet except where the crane lifting points are installed and each has a large washer and nut set in a counterbore in the top of the hog with the heads (outside the boat) being round with the remains of a square underneath.

The two or three buried in the central engine stringer will be "interesting" to remove.

I've seen the unpredicatable corrosion on stainless fittings - they seem to hollow themselves out - usually the affect was worse at the waterline with few problems above or below.

However, the Stainless fitting vendors on the web are suggesting that the marine trade use A4 stainless steels underwater - perhaps only for GRP hulls!

Other vendors only seem to supply Coachbolts in BZP (Bright Zinc Plated) which is about a much use as a chocolate fireguard as it will scratch off as the bolt is pushed through the keel.

I will take a trip to Emsworth I think (thanks Ben) and take the relic with me for comparison.

Sounds like Galvanized is the safest way to go, although the only rot I've found in the hull so far is where the galvanised Anode bolts went though the transom

Cheers,
Scott