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Over the weekend, found two large tubes of 291i hidden in a locker on the boat, both about 5 years out of date, fit for the bin I suppose!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Over the weekend, found two large tubes of 291i hidden in a locker on the boat, both about 5 years out of date, fit for the bin I suppose!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Over the weekend, found two large tubes of 291i hidden in a locker on the boat, both about 5 years out of date, fit for the bin I suppose!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

 

[winch2]

Keep it simple, keep it small, don’t be flash, don’t buy endless kit - and GO!

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

Thats what I asked for and thats what on the face of it he gave me. So is Sikaflex a wet sticky material that doesnt dry out?

 

[fredrussell]

Sikaflex and all the other ‘modern’ ones dry out. Arbomast BR stays ‘wet’. At a guess I would say that 99.9 % of through hulls installed in the last decade or two have been installed with sikaflex or something very similar.

 

[lustyd]

Sikaflex and all the other ‘modern’ ones dry out

Technically they set, which is very different to drying out, especially since they take on water to do so. They do have rated bonding strength though, measured in KG/cm2. Sika 291i was 18tons/metre square. Anything non-setting will be struggle to achieve that sort of figure.

 

[RunAgroundHard]

An adhesive sealant is unsuitable for equipment that is mechanically fixed in place. The adhesive properties are just not required, never have been, and in the past sealant only was just used for fixings like the OPs.

The article below demonstrates states the usefulness, suitability and reliability of modern butyle tape as a sealant.

Bedding Deck Hardware With Bed-IT Tape - Marine How To

So far, in my experience, after trimming off excess post tightening of fasteners, there is no further creep, extrusion or running of butyle tape on hatch bases, u bolts for safety lines, cleats, granny bars, cowling bars. I have not used butyle tape on my rigging chain plates., which are eye bolt styles with a machined flange, they are sealed with an adhesive sealant, as that is what was available a few years ago.

Modern butyle tapes are a very useful product for sealing on a boat, being effective, low cost, reliable.

 

[lustyd]

An adhesive sealant is unsuitable for equipment that is mechanically fixed in place. The adhesive properties are just not required

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.

 

[RunAgroundHard]

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.

It doesn’t make them unsuitable, I agree. It could also be stated that adhesive style sealants are better on rougher, or surfaces that are not as flat as desired as the grab factor might make the seal more durable. In my experience, renovating an old boat, I found a lot of gel coat damage was caused when removing bolted window frames sealed by an adhesive sealant used as a repair solution to leaking frames. I grant that gel coat damage or poor layup of gel coat may have contributed.

However, the point I am making is that there are a multitude of sealing options available to us as DIYers and we shouldn’t immediately assume that an adhesive sealant is best. I think, based on my renovation experience of just one boat, that adhesive sealant was the default choice in the past. My renovation time would have been reduced significantly by not having to deal with bond breaking challenges.

 

[fredrussell]

Technically they set, which is very different to drying out,

I know. I was replying to someone that used the phrase “dry out”, so I used their phrase.

 

[potentillaCO32]

I know. I was replying to someone that used the phrase “dry out”, so I used their phrase.

My process is to use sika/ct1/ob1 below the waterline for eveything. Whether bronze or trudesign type composite.

Above the waterline for deckfittings i tend to use butyl tape if i think i might have to remove it in future or suka/ob1/ct1 if unlikely to be removed or i want it stuck like feck.

As a p.s. i put a keel on a boat using sika before bolting it up and a year later had to remove it for a deeper keel that was available. The sika was so strong you could quite happily sailed without bolts. All the sika had to be cut away with wire. These adhesives are incredibly good in the right environment

 

[Rhylsailer99]

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?

Amazon.co.uk is that any good?