Which Silicon Sealant is best?

[Teddy]

I need to find a silicon sealant (high modulus) to seal a horizontal hatch. It must be able to handle being wet (rain) without going mouldy. The boat builder uses Fosroc 33HM, which is only sold by the limited suppliers in boxes of 20!!

Any tried and tested ideas would be most welcome.

 

[CharlieAlpha]

For me it would be SIKAFLEX 291I SIKA MARINE SEALANT & ADHESIVE (white)

 

[dingdongs]

Pu 40 from toolstation. Com and its cheap and for marine use.

 

[macnorton]

Silicon RTV.

 

[Alpha22]

CT1. Everytime.

 

[lynall]

Pu 40 from toolstation. Com and its cheap and for marine use.

Good stuff, used it on my boat, land rovers, building work!

 

[jfm]

For me it would be SIKAFLEX 291I SIKA MARINE SEALANT & ADHESIVE (white)

That's a polyurethane not a silicone but actually I agree with you- polyurethane sounds better for Teddy's job than silicone

 

[Poignard]

CT1. Everytime.

Good stuff certainly but is it a silicone sealant?

According to the data sheet it's a hybrid polymer. Is that the same?

 

[Actionmat]

I used Sikaflex all over my boat and it works well, it doesn't even smell. You'll get a very neat job if you apply quickly, then smooth it and clean off the excess with a finger dipped in white spirit.

I haven't used RTV in a tube, I've only seen it at work used as a mould making rubber.

 

[piratos]

For me it would be SIKAFLEX 291I SIKA MARINE SEALANT & ADHESIVE (white)

Hello,

Agree that silicon wont work, but after bad experience with Sikaflex I now only use Pantera,

http://www.panteraproduct.de/images.../Produktinformationsblätter/MS3000-60_WEB.pdf
´
It is used same way as Sikaflex, and it can be sanded, painted and only problem is that once cured you shouldnt change your mind..

Two years ago my boat was craned back in the water after the winter on the hard, when it was noticed that water was pouring in from the thru hull sender of the echosounder (actually that was sealed with Sikaflex) - boat was lifted, Sikaflex scraped off, and resealed (while still wet by the way) with Pantera, and back in the water. The man who sealed it told me that inofficially it can even be used under water !

 

[jfm]

Hello,

Agree that silicon wont work, but after bad experience with Sikaflex I now only use Pantera,

http://www.panteraproduct.de/images.../Produktinformationsblätter/MS3000-60_WEB.pdf
´
It is used same way as Sikaflex, and it can be sanded, painted and only problem is that once cured you shouldnt change your mind..

Two years ago my boat was craned back in the water after the winter on the hard, when it was noticed that water was pouring in from the thru hull sender of the echosounder (actually that was sealed with Sikaflex) - boat was lifted, Sikaflex scraped off, and resealed (while still wet by the way) with Pantera, and back in the water. The man who sealed it told me that inofficially it can even be used under water !

It's important to distinguish bar-talk and urban myth from fact though. That Pantera has a cured strength (325psi) commensurate with changing your mind if you so wish. It is not a "don't change your mind" product like Sika292 (550psi) or 3M's 5200. Rather, it has a cured strength broadly similar to ordinary Sika 291(260psi) or 3M's 3200.

If, and I emphasise if, the echosounder sender was sealed using a sika marine adhesive like 291 or 292, and not one of the 100s of other things Sikaflex make, your leak was almost certainly a fault/failure of something other than the Sikaflex