Never use silicone sealant on a boat???

[Jaguar 25]

Once read on this forum that you should never use silicone sealant on a boat. Never quite understood the logic of this. On the opposite end of the spectrum a boat fitter told me to only use Sikaflex if you don't ever want to take the item off again. Recently I removed a cockpit speaker that had been fixed in place with Sikaflex and I had to pretty well destroy it to get it off.
What is the best advice related to fixatives and sealants?

 

[The Q]

Once read on this forum that you should never use silicone sealand on a boat. Never quite understood the logic of this. On the opposite end of the spectrum a boat fitter told me to only use Sikaflex if you don't ever want to take the item off again. Recently I removed a cockpit speaker that had been fixed in place with Sikaflex and I had to pretty well destroy it to get it off.
What is the best advice related to fixatives and sealants?

Using sealant On Sealand might upset the people who live near Chester.

 

[Spirit (of Glenans)]

Don't use silicone anywhere near where you might want to paint or varnish.

 

[AntarcticPilot]

Sikaflex has several different incarnations, some of which are serious adhesives; others set to a rubber consistency.
Silicone is deprecated because once it's on a surface, it makes it very difficult to put anything else on the surface, and it's nearly impossible to clean it off.

 

[Jaguar 25]

Wow, there are some really witty people on this forum!

 

[Tranona]

In general terms there are 2 types of sealant. The first is non setting, such as butyl and polysulphides which are often used for bedding fittings that may need to be removed later such as windows, deck fittings and through hulls. The second is adhesive/sealants which as their name implies set hard as well as seal. There are numerous formulations of this type of which Sikaflex is one of the most common - almost a "generic" term like hoover. Generally not good if you need to remove the fitting, although in many cases cutting through helps. Silicone is generally not recommended as it does not adhere well to some materials such as metals, plastics and wood.

 

[Jaguar 25]

I use butyl for sealing all my deck and cabin top fittings. I recently used Sikaflex when I refitted the wooden guides around the companionway, hopefully I will never remove these again. (Now the wood is oiled instead of varnished so a simple rub down and re-oil as and when necessary. It had taken me¹ a few hours to remove the multiple coats of varnish that hadn't peeled off of their own accord!). Also used Sikaflex to fix the wooden battens to the cabin ceiling that the headlining panels are screwed to.
But, have used silicone sealant to seal the flange on my gas bottle compartment in the cockpit, seems OK and will use it to seal a temporary plate over the hole where my cockpit speaker used to live.

 

[AngusMcDoon]

Once read on this forum that you should never use silicone sealant on a boat. Never quite understood the logic of this.

On a GRP boat any trace of silicone will prevent any subsequent GRP repair from bonding without grinding the whole contaminated area away. You can't see it and can't remove it.

 

[vyv_cox]

As has been suggested, silicones inhibit the cure of many paints and sealants. Every now and then posts complain that Sikaflex or something else has not 'gone off' after several days. This is almost certainly because the fitting or whatever was previously sealed with a silicone sealant.

On top of that the single pack stuff as sold for bathrooms has poor adhesion to most substrates and poor mechanical strength, with the result that in typical yacht service it will soon leak. Two-pack cured systems can be very different and are used for most industrial glazing, for example

 

[lustyd]

Of course, if you're using it for the bathroom on a yacht then most of the above is irrelevant since the requirements are much the same as sealing a shower at home

 

[justanothersailboat]

Bathroom silicone seems to me to be worst-of-both-worlds in that it starts to leak and peel off nastily after a relatively short time, but even when it looks all gone, it can still screw up future work. I've found silicone on deck this winter while making repairs and improvements and am hopping mad about it as it vastly increases the amount of damage I need to do to make relatively simple tidy ups. Silicones are a big family of materials and no doubt there are better ones, but the bathroom stuff is what you'll see anywhere the bodger *ahem* "unskilled optimist" has been at work and it's always a problem.

 

[Scubadoo]

Surely a clean up with something like Acetone will remove any trace of silicone.

 

[vyv_cox]

Surely a clean up with something like Acetone will remove any trace of silicone.

No. Silicones are not soluble in acetone. There are solvents specifically intended for the job but even they are not totally effective

 

[AngusMcDoon]

There are solvents specifically intended for the job but even they are not totally effective

It's best just to avoid it on a boat in the first place.

 

[justanothersailboat]

What will a solvent that can eat silicone do to my GRP?
Theory suggests acetone should be mostly ineffective, but some people report it can help. I may try anyway.

 

[Rhylsailer99]

I made the mistake of using silicon for a top solar fan, and afterwards noticed that the silicon was in a lot places it shouldn't have been.

 

[PCUK]

Wonder Wipes remove silicone well.

 

[lustyd]

I made the mistake of using silicon for a top solar fan, and afterwards noticed that the silicon was in a lot places it shouldn't have been.

Yes silicon should only really be in the panel there, you'd want to use silicone for sealing

 

[Seashoreman]

No Nonsense Sealant Remover 100ml | Silicone Remover | Screwfix.com
I have used this to clean up silicone from a hatch.
It seemed to visibly dissolve the stuff but have no idea if any traces were left.

 

[GunfleetSand]

Spent quite a while trying to work out how a fairly cheap compass had been fixed to the boat. After a while found it had been stuck on with Sika. Took the gel coat with it despite slicing with a knife.

Unless I want something perma fixed I’m using CT1 as it’s a good balance of paintable, removable with careful knife use, strong (have a hand rail stuck on with it will report back in 2-3 years on longevity, v solid for now) sets in damp conditions.

Silicone still has a place in sealing joints but not sure in a marine environment how long that holds, but as above, might be something you want stuck but not forever