SikaLastomer®-710 for keel to Hull union/joint

[ritchyp]

Hi,

I am stripping back the antifouling on my 36 Foot yacht. It has been painted over so many times, it looks a mess and was heavily fouled when hauled back in October.

I've had no water Ingress during the 2 years I have owned her. Anyway, when the boat yard pressure washed her immediately after she was hauled, I noticed something hanging/sagging d from the joint between the keel and hull. Somebody had used clear marine grade silicone which in my opinion was a bodge. Comes as no surprise as I have making good bodges that I have discovered over the last years. The original sealant that is sandwiched between the 2 mating surfaces is like tyre rubber. I need something that will cure like harder rubber but obviously retain some elasticity. I tried Ronseal 145 on my chain plates which were leaking when I got the boat. Useless so I used the appropriate Sikaflex and had success.

This SikaLastomer-710 looks good so I wanted to run it by folks for a nod of approval or a suggestion for a better product to use in this job

Cheers R

 

[ritchyp]

bump

 

[Ademist]

Can’t say it would be better, but we have used CT-1 on our keel to keel joint (our keel is in two parts, which can flex relative to each other) and it has remained in place for 4 years now without obvious change.
We used it after the recommendation of a marine surveyor to friends with the same boat.

 

[HunterWanderer]

Did mine many years ago and still fine. I used a 60 grit sanding disc on an angle grinder to get down to bare metal then sprayed with zinc primer as there were still crevices. I sanded the metal again to just leave the zinc in the crevices.
I also sanded the gelcoat back to get clean surface.
Then put on 2 coats of west epoxy to both surfaces.
When cured, sanded off the runs and roughed up the surfaces used "Stixsall" from Toolstation.
I find it easier than 710 as you can smooth it off with white spirit. ( dont do that with 710 as it chemically affects it and will never cure, painfull experience!) and use it in lots of different situations above and below the waterline. ( e.g. I used it at the top of the rudder at the joint with the shaft)

 

[wallacebob]

Re CT1, I have used it successfully in the past. I found my keel joint seal detached at lift out. I re-read CT1 label; overpaint only with water based paints, not alkyds. So , antifoul is alkyd and affects sealant. I’m using Puraflex 40 (sika product) from Toolstation this time. Says it’s safe with alkyds. I do recall being told to let sealant fully cure before overpainting, to allow volatiles to evaporate. I don’t think these sealants have volatiles tho’.

 

[alahol2]

I've had CT1/OB1 on my keel joint for many years, overcoated with A/F, It is still sticking tenaciously.

 

[ritchyp]

I've had CT1/OB1 on my keel joint for many years, overcoated with A/F, It is still sticking tenaciously.

That sounds interesting to me. Is your antifoul oil based? I read the comments above about not painting over it with alkyd based paints. Perhaps if it was allowed to cure fully before overpainting, it will be okay?

My yacht is in a cradle with a wooden block under the keel so the union will be under compression. I will be having the boat lifted to reposition it so I can strip the old paint and apply new where there are currently supports and bits of plywood. I intend to apply the CT1 while there is no weight on the Keel, just to be sure.

A separate question here. I am planning to move my boat to Southern Spain initially so it will be in the English channel for a month and then on its way to the Med in May. Any advice on which antifouling paint to use as I have read and been told that you need different types of antifouling for different Marine environments. Geographically, the Med is not that far away and not within the tropics so I wonder if the Med really has to have a specific type of antifouling at all?

I know there are already posts about this but I'm just interested to get as many thoughts as possible.

 

[alahol2]

That sounds interesting to me. Is your antifoul oil based? I read the comments above about not painting over it with alkyd based paints. Perhaps if it was allowed to cure fully before overpainting, it will be okay?

I've mainly used Tiger Xtra antifoul and used xylene as thinners. I would have thought you could put a hull primer on top of CT1/OB1 and then coat it with any antifoul. The longer you can give the CT1/OB1 to cure the less likely you are to induce failure.

On your follow up question... very little fouling seems to occur in the early season (before July/August) so I'd be inclined to choose an antifoul suited to your Spanish destination.

 

[ritchyp]