Sikaflex 291i replacement

[steve yates]

That doesn't make them unsuitable though, just means the item is harder to remove. In the case of through hulls that's often a good thing while for deck fittings it becomes a pain.

Just in case anyone reads this in the future and doesn’t realise, butyl tape is not suitable for through hullls, generally its best used above the waterline, and sikaflx etc below the waterline

 

[lustyd]

Just in case anyone reads this in the future and doesn’t realise, butyl tape is not suitable for through hullls, generally its best used above the waterline, and sikaflx etc below the waterline

Not sure why you quoted my post there, I didn’t suggest that

 

[steve yates]

No you certainly didn’t, I should have made that clear. It was more as I read it I thought it sounded that both were fine & it was just a choice of more or less work in future when changing something. Not sure why throhulls immediately popped into my head but they did. Probably just my brain but it occured to me that if it popped into mine, it could pop into others. I can’t be the only dense or literal person on here.

 

[bluerm166]

SIKA have updated their comprehensive marine applications manual.This and other documents suggest that 291i is not discontinued but is retained in their product stable that now includes 591.
Here is the pdf : https://industry.sika.com/dam/dms/global-industry/0/sika-marine-manual.pdf
It includes comparative selection charts and is generally the 'bees knees'.

 

[wombat88]

For those with varnished clinker boats CT1 is available in cat poo brown and seems to do the same job as Sika 291 which now appears to be unavailable in a feline droppings hue.

I have spent a fair amount of time sticking boats back together and agree that clear versions of anything don't seem to perform as well as their solid coloured versions.

One exception, clear Gorilla tape is excellent and sticks to anything so long as applied dry and warm. Excellent for spray hood windows.

 

[Mark-1]

Hmmmm.... Bing Copilot just told me the 2020 tube of sealed OB1 I took off the boat will be good to use today so long as it is viscous enough that it can still be applied.

Does the panel agree?

Ok, I tried this so forumites don't have to.

I'd bought clear last time which was essential for the application I bought it for at the time but needless for the stuff I did this weekend. So I was starting off from an inferior product IMHO. (Clear doesn't like UV IMHO.)

So out of the tube it was such low‑viscosity it hurt my fingers squeezing it out. It also had a yellow tinge to it which I'm sure is due to age.

It applied ok and has cured ok. I have no idea if it's as strong as it's supposed to be but it seems to have stuck ok.

So my vote would be don't use 5yo OB1 but if you have to you'll likely get away with it. Which is pretty much what Copilot told me.

 

[ducked]

So out of the tube it was such low‑viscosity it hurt my fingers squeezing it out. It also had a yellow tinge to it which I'm sure is due to age.

Dont you mean high viscosity?

 

[Dellquay13]

I think one of the advantages of ob1 and ct1 over sika seems to me a much longer shelf life. If i open sika and don't use it all within a couple of weeks it all cures within the tube.

The Sika rep told my local supplier to keep open sika 291i tubes in the freezer to prolong their life

 

[Mark-1]

Dont you mean high viscosity?

Yes, but it's too late to edit.

Thanks for the correction.

 

[vyv_cox]

Interesting. I am currently replacing two hatches/roof lights in my 2007 motorhome. The original one was stuck down with butyl, still quite soft but took some effort to pull up. The replacement recommended is Sikaflex 521 UV, which is indistinguishable by me from the 291 that I have used for years. It seems there may be a rethink in the most appropriate sealant.

Having said that the old one never leaked but its polycarbonate 'glass' is embrittled and broke off in a storm.