Sikaflex 291i replacement

[Never Grumble]

Over the weekend, found two large tubes of 291i hidden in a locker on the boat, both about 5 years out of date, fit for the bin I suppose!

 

[lustyd]

Over the weekend, found two large tubes of 291i hidden in a locker on the boat, both about 5 years out of date, fit for the bin I suppose!

They’ll work, just don’t use anywhere important. They cure with moisture from the air so add some if it’s struggling!

 

[steve yates]

I'm not labelling people, nor saying it's not appropriate. I am saying that modern solutions are vastly superior, require less or no maintenance, and provide a better seal. It's the reason new products were created in the first place.
There is plenty of evidence if you care to look. Butyl never sets so in flexible situations will gradually seep out or get squeezed out if any pressure is applied. It's even recommended to trim any back as it comes out and tighten fixings over time. I'm not sure how you've managed to avoid seeing this as it's all over the Internet on forums, blogs, videos etc. with people relaying their experience of the stuff. It's not even like the results are a surprise, it's literally how the product is described.

Its exactly the fact that Butyl never sets that makes it appropriate for sealing fittings that flex. Trimming away excess is purely cosmatic, exactly the same as cleaning off any Sika that oozes out
I have never heard of any evidence that Butyl does not work but have read of it keeping fittings leak free for 20 years plus. It is also very very easy to remove or replace when fittings are changed, which is a definite plus.

 

[Mark-1]

Over the weekend, found two large tubes of 291i hidden in a locker on the boat, both about 5 years out of date, fit for the bin I suppose!

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?

 

[Boathook]

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?

Try it and report back

 

[potentillaCO32]

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?

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.
With ct1, as long as you screw the top back on, it is good to go even after a few weeks.
However, i don't know if the bond is as strong or long lasting as sika but it seems to work pretty well for me. I may be wrong but i seem to find the black coloured ob1/ct1 works better than the clear.

 

[Mark-1]

I think one of the advantages of ob1 and ct1 over sika seems to me a much longer shelf life.

It says 18 months on the tube so on that basis well past use by date BUT bing copilot says it cures only with moisture and is therefore totally stable until it cures. That sounds plausible to me but copilot couldn't provide a link so .

However, i don't know if the bond is as strong or long lasting as sika but it seems to work pretty well for me. I may be wrong but i seem to find the black coloured ob1/ct1 works better than the clear.

I'm certain you're right that the clear OB1/CT1 is far worse. I used clear on my shed window and boat windows and it disintegrated, I assumed due to UV. I tried brown on the shed and it's lasted about 6 years so far.

Try it and report back

As luck would have it it's for a mast plug that I don't want to rivet, so I can safely experiment at a risk of having to buy a new plug for a tenner.

 

[lustyd]

If i open sika and don't use it all within a couple of weeks it all cures within the tube

could be the difference between 291 and 291i (in the old days) as the i (i-Cure) was a faster curing mechanism using moisture so it was designed to do this.

 

[Mark-1]

However I'm told, and have read, that 291i has been discontinued, though it still seems to be available.

Yeah, still seems to be available, Force 4 in Chi have loads of it today.

 

[winch2]

Ive read several of these threads now and Im still none the wiser and after my experience last yr fitting an outlet pipe.. slightly miffed. 40 yrs ago we used a horrible sticky black mastrick which remained "wet" and sealed and stuck for ever. I asked my boatyard for a dab of same to seal a skin fitting I was doing. Fellow filled my pot with a black sticky substance. Fitting the gland I noticed that it started to dry, then roll and detach from the fitting....acting more like a rubbery gasket material, useless.
Is there anything available now like that old wet mastic or are the halcyon days of sailing a dry boat well and truly over?

 

[fredrussell]

…Is there anything available now like that old wet mastic or are the halcyon days of sailing a dry boat well and truly over?

Arbomast BR should do it, but why you’re not using any of the modern adhesive sealants is beyond me.