Keel to Hull Joint Cracking

[Guzzy]

Hi, As a newbie to yacht ownership I'm hoping for some advice.
I recently bought a 1978 Seamaster 928 as a winter project with a view to getting her ready for next year. There is a rusty crack around the joint between the keel and the hull. Inside the keel bolts have been sealed over with fibreglass and some kind of sealant. The boat has been standing in the yard for at least 10 years and the glass covered bolts were covered in foul smelling oily water which I've now cleaned away. I don't know why the bolts have been sealed over - is this normal? I was thinking of grinding away the glass fibre to get to and inspect the nuts and test for tightness etc. If all seams OK then I was planning to grind out the crack above and below and seal it with some type of flexible sealant e.g. Sikaflex. Does anyone have any advice for a novice sailor?

 

[Tranona]

You are thinking along the right lines. Encapsulating the heads was common when the boat was built. Pros and cons, but resist exposing them as almost certainly the bolts (or more likely studs and nuts) will be sound.

The rust around the joint is likely to be from the exposed edge of the iron keel and is quite normal. The thing to worry about is water leaking through that joint and getting at the bolts. However, this is unlikely and suggest you rake out the seam, clean up the exposed part of the iron then treat with Fertan followed by a flexible sealant. When you haul out next time check it and if you have evidence of water in the joint - usually heavy rust stains running down the keel it may be time for getting an expert opinion.

 

[jwilson]

As above: don't grind, you'll damage the GRP surface. Scrape out loose filler, treat the rust with fertan or similar, and put on a coat of primer then polyurethane sealant like PU40. If you have rust satins running down the keel like https://keyassets.timeincuk.net/inspirewp/live/wp-content/uploads/sites/19/2014/02/IMG_1594.jpg but worse, and these vertical streaks are definitely in line with the keel bolts locations, you may have keel bolt corrosion, which is a bigger problem but fairly rare on GRP boats.

All iron keels sooner or later get rust on the top hull mating edge - resealing and repainting every so often is routine maintenance.

 

[Guzzy]

Tranona and Jwilson,

Many thanks for your replies - That has allowed me to sleep easier. I now have a plan to get this done before the winter sets in. I've attached some photos of the keel and the bolts inside.
Many Thanks.


View attachment 72892

 

[Champagne Murphy]

There looks to be some black stuff around the edge of the encapsulating GRP. Is that the sealant that you speak of? Or is it exudate from the encapsulation/hull joint?

 

[Guzzy]

I thought that the black stuff was sealant as it seems to be flexible in places but brittle in others.
Could it be the sealant being forced out due to rust build up around the keel and bolts causing pressure?
Do you think it would be best to cut away the fibre glass on one of the bolts for an inspection?

 

[Champagne Murphy]

I thought that the black stuff was sealant as it seems to be flexible in places but brittle in others.
Could it be the sealant being forced out due to rust build up around the keel and bolts causing pressure?
Do you think it would be best to cut away the fibre glass on one of the bolts for an inspection?

I really don’t know although my keel bolts (Sadler 32, encapsulated from birth) don’t show such signs. Others here will have a better idea but if in doubt I would ask a good boat builder or GRP specialist ahead of a surveyor unless I knew he was the dog’s.

 

[vyv_cox]

I thought that the black stuff was sealant as it seems to be flexible in places but brittle in others.
Could it be the sealant being forced out due to rust build up around the keel and bolts causing pressure?
Do you think it would be best to cut away the fibre glass on one of the bolts for an inspection?

It appears to me that the covering over the bolts has been added at some stage and is not original. I think I would have a look underneath one. It is worth establishing whether they are bolts or studs with nuts, carbon or stainless steel, and whether any rust is coming up them. Do not be concerned about any carbon steel washers under the bolt head or nut, as these commonly rust but do not necessarily indicate a leak. Most people find that even with carbon steel bolts the shank is in good condition, even if the head looks heavily rusted. Stainless studs in GRP boats are invariably in good condition, as the keel itself is anodic to them.

 

[Champagne Murphy]

As Vyv says, the GRP on the bolt tops looks to be a different colour to the hull colour so it looks like an afterthought. If you grind one away and its fine then it should be easy enough to re-cover but to a better standard. Before that take pictures of the revealed bolt and keep a maintenance log. When/if you ever sell the boat a surveyor then has it for reference.

 

[Guzzy]

Many thanks for the advice I will let you all know how I get on and what the bolt / nuts look like when I uncover them.

 

[Tranona]

If you are going to expose them suggest you clean them up, assuming they are sound and if mild steel paint them rather than covering up. If stainless leave them uncovered. Ideally keep the bilges dry from then on!