Sikaflex 291i replacement

[MJWB]

Got a leaking chainplate. It's not a bar through the deck with what I call a capping plate. It's on a Westerly and is more like what I would call a pad eye like fitting that goes through the side deck and is then double bolted to the mounting fittings inside the boat.
Was thinking of using Sikaflex 291i to bed the fittings and seal into the holes as it has a bit of flex for when the standing rigging is tensioned. However I'm told, and have read, that 291i has been discontinued, though it still seems to be available. The replacement seems to be Sikaflex 591. Has anyone got any experience of 591?

 

[Hacker]

You could use EBT+.

 

[lustyd]

Any 291i still available should be out of date as it was discontinued in 2023 from what I can see.
The 591 is “more sustainable” but hopefully still works, although that’s never a good sign

 

[potentillaCO32]

Butyl tape?

 

[MJWB]

Butyl tape?

Doesn't feel like the right solution tbh. Not sure why I think that.

 

[VicS]

Any 291i still available should be out of date as it was discontinued in 2023 from what I can see.
The 591 is “more sustainable” but hopefully still works, although that’s never a good sign

They are different types of material.
291i is a polyurethane, 591 is described as a "silane terminated polymer".

 

[MJWB]

They are different types of material.
291i is a polyurethane, 591 is described as a "silane terminated polymer".

I daresay the so what of all this is......
Is 591 suitable for all purposes 291i has been used for? I don't know.
Other practical question in my mind is whether 591 is more of a sealant than an adhesive, or the other way around? Not being very knowledgeable about these substances I assume it's more of a sealant.

 

[UK-WOOZY]

Never knew until reading this it was discontinued. 591 is the replacement apparently.. sucks.

Iv used CT1 in the past. Or got 3M 4200 the past two weeks for a through hull

 

[Boathook]

I'm using arbomast br, the butyl in a tube. Where possible i also counter sink the holes so that a bead forms round the thread.

 

[Hacker]

If you merely want to seal then arbomast or butyl tape will do. If you want some adhesion as well then you need a proper adhesive sealant.

 

[potentillaCO32]

Doesn't feel like the right solution tbh. Not sure why I think that.

I thunk for flexuble sealing of chainplates butyl might be better than sika. You are not trying to bond them.

 

[lustyd]

There are always butyl enthusiasts in threads like this. I'm not sure what keeps them going when the evidence shows quite clearly that modern products are better for the task. Butyl gradually seeps and squeezes if any pressure at all is applied, it's a terrible answer to the problem that was used because at the time it was all that was available. It's like the varnish enthusiasts who try to convince others to spend their winters sanding and coating every year

 

[potentillaCO32]

There are always butyl enthusiasts in threads like this. I'm not sure what keeps them going when the evidence shows quite clearly that modern products are better....

Why are some so judgemental and keen to label people. My boat is a fine mix of ct1/ob1/sika and epoxy. But for flexible sealing i have not seen anywhere saying that butyl tape is not appropriate.

 

[lustyd]

Why are some so judgemental and keen to label people. My boat is a fine mix of ct1/ob1/sika and epoxy. But for flexible sealing i have not seen anywhere saying that butyl tape is not appropriate.

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.

 

[Boathook]

There are always butyl enthusiasts in threads like this. I'm not sure what keeps them going when the evidence shows quite clearly that modern products are better for the task. Butyl gradually seeps and squeezes if any pressure at all is applied, it's a terrible answer to the problem that was used because at the time it was all that was available. It's like the varnish enthusiasts who try to convince others to spend their winters sanding and coating every year

So what is the modern equivalent of butyl ?

I don't want an adhesive sealant.

 

[lustyd]

Adhesive sealants are the modern solution. They’re harder to clean up but since you don’t have to keep redoing it thats not such an issue.

 

[mrangry]

My deck fittings are all sealed using butyl tape/sealant and had no leaks for a number of years. It is dynamic and ideal for fittings that give slightly. I am not trying to convert anyone, just giving my experience.

 

[Hacker]

So what is the modern equivalent of butyl ?

I don't want an adhesive sealant.

In that case my vote would be Arbomast br. It does contain butyl but does skim on the surface whilst remains flexible underneath. We use it for planking (garboard and stem/stern) when building wooden boats.

 

[Never Grumble]

I never realised this either and the other month picked up from a well known chandlery a tube of what I thought was 291i having just found it I see it is 591. I've always used 291i to secure my hull skin fittings ... I wonder if 591 is suitable?

 

[lustyd]

I never realised this either and the other month picked up from a well known chandlery a tube of what I thought was 291i having just found it I see it is 591. I've always used 291i to secure my hull skin fittings ... I wonder if 591 is suitable?

TruDesign recommend it so yes.