A24 Replacing Keel Bolts on Zethar by Geoff Marks.

A weep from the aft keel bolt.

This post was copied from the old web site and describes the steps taken by Geoff Marks removing and replacing the aft keel bolts on "Zethar" in 2002/3. 

For illustrative purposes only, professional advice was taken before starting and during the job and you should do the same.

The weep meant a breach in the hull to keel join but this was easy to find as the place was marked by a small patch of rust and cracking in the antifouling at the after end of the keel on the starboard side. The gap was revealed with a scraper.

The rest of the join was good and there was no other cracking, not even on the port side aft. The offending gap was cleaned and left to dry out. Zethar had been epoxied in 1986 and a skin of epoxy covered the hull to keel join, so this was disturbed that as little as possible.

The bolt was removed using an open ended spanner with a three foot (1 metre) length of pipe for leverage. Although it was tight at first and for the first few turns the bolt undid easily enough. 

The drawn bolt was in good condition for close to 30 years old.

The bolt before cleaning. A length of new 1 Inch dia BSW
(British Standard Whitworth) threaded bar is included in the
pictures for comparison.

After cleaning.

There was cracking found in the grp under the plate washer.

It seemed that there was foam under the grp and
after more cleaning it looked like the hole was lined.

The lined hole meant there was some support
beneath the grp which it was hoped would
make a repair easier.

A professional was employed who had all the experience and tools needed and soon had the grp cut away. Underneath was a solid block of what looked like cement which explained the lined hole. This gave a solid foundation for the repair and solved the potential problem of keeping the bolthole clear of resin. The 'cement' block turned out to be a mix of resin and micro-balloons which are a grey powder before mixing.

A resin and glass mix was used for the repair to make a solid block to tighten the new bolt down onto. Because of the thickness of resin needed it was applied in two stages. In the first glassing the mix was pushed out under the edges of the grp and the block was covered.

This was left to cure completely before the second glassing was done.

The second glassing was a bit more complex as it was necessary to keep the bolthole clear and get the level of the resin correct so that the new plate washer would seat properly. This was done by replacing the old bolt and the new plate washer (made of 10mm thick mild steel) and wrapping them both in release tape topped with a smear of silicon grease.

You can see that the plate washer is flush with the resin. This is because the resin was squeezing out unevenly around the edges of the washer so making it flush was much tidier. The thickness of the resin was built up at the forward edge to get the washer square with the bolt. The washer and bolt were removed the next day and the resin left another 24 hours to cure.

The laminator did an excellent job!