Sikaflex questions will be answered. Maybe...

[Greenheart]

I've used Sikaflex 291i over recent years and am satisfied that it is a good sealant with some adhesive quality. But for attaching my keel-band without screws below the waterline, I'm going to give Sika 292 a try, since it is primarily an adhesive.

Of course, the 300ml cartridge I've ordered is lots more than I'll need, and I already have some unused 291i left over, even after redoing round the bath, so I'm thinking I'll do some tests to determine how marked is the difference in their strength.

If anyone has been idly wondering about the relative effectiveness of Sikaflex 291 and 292, please suggest applications which I can attempt to replicate using...I dunno...bucket of water, some old rope and offcuts of ply, GRP etc.

Granted you can probably read Sikaflex's laboratory-test conclusions on their website, saying how fabulous their products are, but here, only your own imagination is the limit.

Pre-emptively, please don't suggest that I try gluing my fingers to something well away from my keyboard.

 

[VicS]

I've used Sikaflex 291i over recent years and am satisfied that it is a good sealant with some adhesive quality. But for attaching my keel-band without screws below the waterline, I'm going to give Sika 292 a try, since it is primarily an adhesive.

Of course, the 300ml cartridge I've ordered is lots more than I'll need, and I already have some unused 291i left over, even after redoing round the bath, so I'm thinking I'll do some tests to determine how marked is the difference in their strength.

If anyone has been idly wondering about the relative effectiveness of Sikaflex 291 and 292, please suggest applications which I can attempt to replicate using...I dunno...bucket of water, some old rope and offcuts of ply, GRP etc.

Granted you can probably read Sikaflex's laboratory-test conclusions on their website, saying how fabulous their products are, but here, only your own imagination is the limit.

Pre-emptively, please don't suggest that I try gluing my fingers to something well away from my keyboard.

You will find figures quoted on the data sheets for both products when tested by standard test methods. I think i would have more faith in figures obtained by such means done under laboratory conditions than from some amateurish methods involving buckets of water in a boat park somewhere.

 

[Greenheart]

Amateurish??? Outrageous!

You have a good point of course Vic. I just thought some side-by-side tests with photos to demonstrate my methodology and the results, might help instruct readers such as myself, about the stickiness of each type.

The subject of Sikaflex pops up often here, and it's often the same theme - someone has bought 291i, believing it has the adhesive properties of 292. I suppose 291i dominates chandleries because it is a good sealant...

...rather than for any gluing ability. I couldn't find 292 for retail sale anywhere, but I doubt I'm alone in needing a strong slightly elastic seawaterproof adhesive - although whether 292 is sufficiently better than 291i to justify tracking it down and paying almost double for it, I aim to test and find out for myself.

Ultimately my best test may be the reason I bought the 292...the tough job of holding a narrow section of brass on the GRP keel-line of a big dinghy.

 

[Iliade]

...but I'd be more prepared to accept that I could only achieve similar results to some amateurish method involving buckets of water in a boat park somewhere and not the superb results which can be achieved in a lab. :0)

 

[Mister E]

The lab tests would normally be done in very clean conditions with new material and perfect preparation. Unless you can replicate those conditions for what you want to glue then it is probably best to try and replicate the conditions you will have.
Thus your tests could be valid for your application as you need the stuff to work.
Just stick some brass on some old GRP in different states of clean preparation. Then leave to cure for different times before dragging through sand and mud to see if it lifts.
The Data Sheets should be a good starting point and give an idea of the preparation expected by the company.

Check out Puraflex 40 from Toolstation as I have found this works really well as a sealant adhesive.

 

[PaulJ]

A word of caution....... whichever you decide on, if it is to be used below the waterline, check how the sealant reacts with your proposed antifouling. Last year I took the keel off my boat in order to check the keel bolts and then re-seat/seal it. After the keel was back in place there was a largish groove all gound which I filled/faired with Sikaflex 291i. It was allowed to cure for a few days and then I primed and antifouled over the joint. The antifouling, or possibly the primer, reacted with the Sikaflex and in the area of the the joint there was just a sticky mess where the antifouling refused to dry. I had to dig the sikaflex out of the groove and do it again with a different sealant....... I used Saba which did not seem to react with the antifouling. In places the sealant was quite thick and, though it felt ok to the "fingernail test", I think it is possible that the Sikaflex was not fully cured. However a test of the sealant/antifouling combination you propose to use could save you a lot of trouble!

 

[Greenheart]

Check out Puraflex 40 from Toolstation as I have found this works really well as a sealant adhesive.

I might do that Mister E...since Toolstation sends me about five emails per day, their Puraflex should certainly be easier to locate than Sika 292 was.

For my own purposes, I'm not looking to test which product to use - I'm already commited to trying Sika 292 - I just thought that with loads left in the cartridge, I can spare enough to do some simple and possibly illuminating tests.

PS, antifouling isn't an issue I'm relieved to say...she's only a dinghy. But it sounds like thickened epoxy would have been more suitable for your keel-groove problem, Paulj.

 

[Plevier]

Check out Puraflex 40 from Toolstation as I have found this works really well as a sealant adhesive.

PU40 is good stuff but I would categorise it as a Sika 291 style product.
For real adhesion, try Stixall, also from Toolstation.

PU40 and Stixall are both made by EverBuild, which is now part of the Sika group. PU40 used to ocme in plastic cartridges but the last time I bought it, it came in a metal one just like Sikaflex does and it said "made in EU" on it, previously it was made in UK.

 

[VicS]

PU40 is good stuff but I would categorise it as a Sika 291 style product.
For real adhesion, try Stixall, also from Toolstation.

PU40 and Stixall are both made by EverBuild, which is now part of the Sika group. PU40 used to ocme in plastic cartridges but the last time I bought it, it came in a metal one just like Sikaflex does and it said "made in EU" on it, previously it was made in UK.

PU40 is a polyurethane sealant similar to Sikaflex 291. Whether or not it is as good an adhesive I dont know. I have not seen iny data and I have not used it

Stix All is a silicone copolymer similar to CT1. How good n adhesive it is I dont know ! I have only used it for one job and I have not attempted to break the joint.

 

[Greenheart]

The more I read, the more I'm persuaded that these products' real-world versatility is an obscure area.

I'm tempted to line up Stixall and PU40 alongside the Sikas, for a big parallel test.

 

[rogerthebodger]

You will probably find the PU40 is now the same as Siks 291 just with a different label. I do know that sika 221 is the same as sika 291 just with a different label. My local sika man told me that.

 

[Mister E]

The more I read, the more I'm persuaded that these products' real-world versatility is an obscure area.

I'm tempted to line up Stixall and PU40 alongside the Sikas, for a big parallel test.

That was what I was hoping would happen. Things stuck together and then dragged through sand, maybe even pressure washed. It would be interesting to find out what stuck the best in some sort of destructive testing.

 

[ghostlymoron]

UK is in the EU at the moment.

PU40 is good stuff but I would categorise it as a Sika 291 style product.
For real adhesion, try Stixall, also from Toolstation.

PU40 and Stixall are both made by EverBuild, which is now part of the Sika group. PU40 used to ocme in plastic cartridges but the last time I bought it, it came in a metal one just like Sikaflex does and it said "made in EU" on it, previously it was made in UK.

 

[Plevier]

UK is in the EU at the moment.

Indeed. The made in EU label does not exclude its being made in UK. Perhaps in the future they will have to be more explicit.

 

[Greenheart]

Well, I haven't yet done any comparative side-by-side tests of different types of Sikaflex...

...but I've committed myself to the bigger test, of using Sika 292 to hold my new brass keel-band on.

I reckon it looks good and seems sturdy, although I'm afraid that the Sika may release its adhesion suddenly, without warning.

So I'm inclined to relent on my no-screws approach, and use half a dozen of the very smallest (10mm) to prevent the glue having to take all the strain. I'm also thinking that the Sika, being so rubbery, might stay tight round the screws, preventing the leak recurring...

...leaks from the screw-holes in the GRP were the reason I chose Sikaflex for the job.

Perhaps it seems nuts to have planned relying on Sika alone if I end up reverting to belt & braces, but the belt on its own caused one problem (leaks) and the braces may not be sufficient on their own...so I'm thinking both may be a good combo...

It may not be obvious, but the brass strip is two or three millimeters off the hull, and the slight pliability of the Sikaflex may be pretty good for impact-resistance.

Any thoughts/advice? Thanks.

 

[laika]

please suggest applications which I can attempt to replicate

Do you have an old pair of shoes? And a ceiling?

 

[Plevier]

Indeed. The made in EU label does not exclude its being made in UK. Perhaps in the future they will have to be more explicit.

In fact I got that wrong. The label actually says "made in Europe" so bravo for Sika, not conflating Europe and the EU! They have both outcomes covered.
Whenever someone talks about our "leaving Europe" I wonder how many tugs it will take to shift us.

 

[Greenheart]

Do you have an old pair of shoes? And a ceiling?

Thanks Laika. But I wasn't trying to test Sika's adherence on leather and plaster...more interested in whether chaps think I should compromise the watertightness of my hull by drilling holes in it, or whether I should compromise the life-expectancy of the keel-band by avoiding drilling holes in the hull.

When I attached the keel-band on Sunday, I did also use some spare Sika 292 to glue a piece of epoxied iroko to a chunk of plastic drainpipe, and to a couple of steel spanners. Not accidentally...just to see how resistant it'll be to separation. I put it down in the shed somewhere and haven't found it again yet, but I'll report back.

I used Gorilla-brand duct tape to mask the hull when I attached the keel-band, and I was slightly dismayed to discover that the Sika 292 hadn't even begun to adhere to the tape. I mean, I know the tape was there to prevent adhesion to the hull, but I intended it to be sacrificial, and I'd hoped the Sika would be a stickier opponent.