Antifoul has become wet (sticky) over Sikaflex sealant. Hot weather?

[HandmadeMatt]

Hi.
My boat's on the dry. I cleaned and prepared the hull. I sealed some places on the keel joins with Sikaflex - 291i and let it dry for 24hours (it's been hot so it should have been plenty, it certainly felt dry.)

I then painted the hull with antifoul and it dried nicely. I've then been away on holiday for two weeks and upon returning I have discovered that the antifoul is wet and sticky just on the patches over the Sikaflex.

Could it be the hot weather?
Will this be a problem?
Will it resolve on it's own or do I need to do something about it do you think?

Opinions please.
Thanks.

 

[KellysEye]

I would not have used Sikaflex it should be underwater epoxy it sets as hard as steel, available at any chandler.

 

[ninky]

Are/ were there gaps where the keel joins the hull? That doesn't sound great and not sure you want flexible sealant to rectify this...It's only for light bonding. Some info on silkaflex here (was it the 291 you were using?) that says service temp -40 to +90, so don't think that would be the issue. http://usa.sika.com/en/solutions_products/download/doc_download/download_industry/Sikaflex.html

 

[James_Calvert]

I use sikaflex.

Sometimes I've antifouled before it's set. It then tends to stay quite soft until the next lift out. The antifoul also stays alittle sticky but I've not noticed any difference in the antifouling performance.

You probably don't need to, but if convenient, I'd run a another brush of antifouling along the joint before you launch.

 

[HandmadeMatt]

Basically the boat has a flexible sealant around the keel hull joints already and has been in service like this for many years. In scraping and preparation I dislodged some of it so I was just replacing it. The guy in my local chandlers said that this was the best stuff to use and that it was fine to antifoul over so I am a bit miffed.

 

[KellysEye]

Sikaflex is not an intended to be used as an under water product, but fine as a sealant for teak decks with sea water flowing over them occasionally. The chandler should know better and told you to use underwater epoxy, perhaps you would like to tell him so he doesn't mislead anybody else.

 

[James_Calvert]

Sikaflex is not an intended to be used as an under water product, but fine as a sealant for teak decks with sea water flowing over them occasionally..

But it does work - as a thick flexible paint film, which needs renewing occasionally.

A hard epoxy filler might be ok if it doesn't crack and permit subsequent corrosion, but not to patch a flexible filler that's already in place.

 

[Arrival VII]

Hi

I had a similar issue with Sikaflex, but I found the problem was not with Sikaflex and the antifouling, but with the primer I used on the keel in the first instance which was a Primacon Type primer from Blakes (yes I know Primacon is an international product). It appears the two products are incompatible. My solution was to use a Silicon Sealant which has worked well for years and years.

Using epoxy is fine as long as you have zero movement between keel and hull, if that is not the case the epoxy will crack.

My keel is has a flange on the top which is married to a recess in the hull, Dow Corning Silicon (despite instructions saying don't use underwater) is superb. When I originally tried using epoxy is cracked pretty instantly. Interestingly people like Jeanneau and Beneteau seem to use a Silicon based product in this area.

 

[HunterWanderer]

Sikkaflex is great for the keel to hull joint but you do have to let it cure completely before overpainting with a solvent based paint such as antifouling. 24 hours isnt enough to ensure a complete cure as it relies on moisture to cure not just temperature.
Just remove the sticky paint with a scourer and lots of water and detergent. Then leave for a few days then repaint with antifouling. Should then be good for years.

 

[HandmadeMatt]

Thanks HunterW.
It's going to be messy to remove it. Ce'st la vie.
I might consider leaving it as JamesC says he has done and then re-do when she comes out for this winter.
I've got to varnish the decks and paint some trim and then she's ready for the water so I was hopping to get her in this season.
We'll see.
Thanks again everyone.

 

[KellysEye]

>A hard epoxy filler might be ok if it doesn't crack and permit subsequent corrosion

Underwater epoxy doesn't crack, as I mentioned it sets as hard as steel.

 

[James_Calvert]

>A hard epoxy filler might be ok if it doesn't crack and permit subsequent corrosion

Underwater epoxy doesn't crack, as I mentioned it sets as hard as steel.

But on a joint between cast iron and fibreglass, a hardsetting filler may crack. Fibreglass flexes under load. Cast iron doesn't. And in those circumstances, sika flex works fine Nothing wrong with the advice given by the chandler to the original poster, I know it works.