Advice on keel/hull leak

[JamieB]

We have a slow leak coming from under a GRP ‘step’ where our furthest aft keel bolt is located (pic attached). We had the keel remover three years ago to inspect keel bolts and re-bed the hull/keel joint. It was found to be in good shape and a load of new sealant was applied (after removing old) before bolts were torqued to correct load. It appears this is a slow leak coming through where the trailing edge of the keel meets the hull.

I’ve been thinking about how to resolve this - and am clearly not keen to drop the keel again unnecessarily. One idea I had was to install a vacuum bag around the offending spot in the bilge and vacuum epoxy through from the outside using a second bag to fill the void. I was assuming an initial pre-vaccum could help remove any residual moisture. Given the small size of the leak I’m thinking it’s only going to need a few 100ml of epoxy.

Does anyone have any thoughts on this as a concept? Any thoughts greatly appreciated.

 

[JamieB]

 

[Tranona]

You would perhaps be better posting this on the PBO section of the forum as that gets far more traffic from people who might be able to offer advice. Some details of the boat might also help.

 

[KevinV]

In my humble opinion and experience you'll never get anything to seal properly in a now contaminated joint, and you have salt water sitting on the bolt. The only sensible thing is to drop the keel and do it again, properly.

 

[JamieB]

In my humble opinion and experience you'll never get anything to seal properly in a now contaminated joint, and you have salt water sitting on the bolt. The only sensible thing is to drop the keel and do it again, properly.

Thank you Kevin, much appreciated

 

[JamieB]

I like this approach a lot. Fluorescein is also a great idea. Thank you very much.

 

[Keith 66]

Firstly, that photo shows two cracks in the grp one each side at the rear, these extend under the sealant & washer under the keelbolt nut. You are clutching at straws if you think vacumn bagging epoxy in there is going to work.
Epoxy does not like contamination & thats in a bilge, sea water, oil, antifreeze etc. Cracks at back end of keels are common often caused by running aground as the keel rotates upward at the rear.
Your only option is to remove the nut, washer & sealant & have a grind at the area with a powerfile to remove the gelcoat & see whats happening. You will then likely have to grind away the broken glass & redo it properly.

 

[barca nova]

deleted duplicate

 

[barca nova]

I have had two boats now which have a GRP stub keel with a lead bottom half bolted on. In both cases the joint, presumably bedded on sealant etc, has a 30mm wide rubber strip bonded on the outside with butyl rubber adhesive. Boat built by Bowman. No leaks whatsoever in 14 years and of course this approach is flexible to a degree. When blasting the hull for coppercoat I replaced the strip myself and it was very easy to do. And certainly worth trying before again dropping the keel.

 

[JamieB]

Thank for all for your great ideas. I used Fluorescene to trace a tiny leak from a crack around the very aft keel bolt to the keel hull joint. I’ve removed the loose material and relaminated around the bolt and have a bigger washer plate. Next job is to refill around 1ft of the aft end of the hull keel joint (I raked out to trace the dye) with Sikaflex. I recall it needs to be completely dry to get a decent bond. Any thoughts on how to dry this area on a boat on the hard in winter. Anyone tried clingfilm around cradle legs and heater inside this zone? Also do you think it is a good idea to use the Sika Marine Multi-primer to get best adhesion to the existing sealant further fwd?

 

[barca nova]

Thank for all for your great ideas. I used Fluorescene to trace a tiny leak from a crack around the very aft keel bolt to the keel hull joint. I’ve removed the loose material and relaminated around the bolt and have a bigger washer plate. Next job is to refill around 1ft of the aft end of the hull keel joint (I raked out to trace the dye) with Sikaflex. I recall it needs to be completely dry to get a decent bond. Any thoughts on how to dry this area on a boat on the hard in winter. Anyone tried clingfilm around cradle legs and heater inside this zone? Also do you think it is a good idea to use the Sika Marine Multi-primer to get best adhesion to the existing sealant further fwd?

Hairdryer. Dont try hot air gun - I made that mistake on an earlier boat and ended up with a patch of srface burnt grp. In any case you can get both epoxy fillers and butyl rubber sealants that will adhere to damp surfaces and seal them

 

[JamieB]

So the strip is stuck to the keel joint ‘smile’

Hairdryer. Dont try hot air gun - I made that mistake on an earlier boat and ended up with a patch of srface burnt grp. In any case you can get both epoxy fillers and butyl rubber sealants that will adhere to damp surfaces and seal them

ok great thank you

 

[yotter]

Is it not more normal to use an infared heater for this purpose.

 

[barca nova]

Is it not more normal to use an infared heater for this purpose.

in my wife's view - yes! ;-)