Thread: Sika super grip

I wouldn't use a 5 minute epoxy, for any serious boatbuilding. It is prethickened so only sits on the surface and the fast cure makes that problem worse.

Also the 1 to 1 epoxies are much weaker than the ones we use for boatbuilding. Though a good manufacturer (System 3) has one now.

The thing about epoxy is that it is a complete package. That you can use it to coat all the surfaces too to knock the maintenance on the head.

As far as the sika goes ... I would be interested to see the tensile and shear strengths of the material itself. The flexibility as susceptibility to tearing with triaxial loads (corners) or where the design doesn't allow enough chance for it to "come and go" it tears away easily.

One example of the "come and go" problem is when sikaflexing between fake planking on a ply deck. you must put a tape down first - so the sika doesn't stick to the ply underdeck as well - as the sika will tear from the bottom corners as the timber goes through its cycles of drying and soaking.

What is exactly happening is that if you put the release tape down first the sika is only stuck to the edges of the plank ... so it has the whole width of the join to take up any swell and shrink.

But if you don't put the tape down then in the corners where the planking meets the deck the sika in that corner has no capacity to stretch because it is glued to the two adjacent surfaces down in the corner - there is no gap.

I would also suspect that the sika would end up being more expensive than the epoxy with one tube costing $15 to $20.

The epoxy or any glue is affected this same way ... but because sika relies on lots of elongation to take its maximum load it is vulnerable in a way that less stretchy (higher Young's modulus) materials are not. The less stretchy materials can put load across a join even with very small gaps like the corners spoken of above.

I would also be suspicious of its behaviour when confronted with high local loads. Masts, spars, rudders, centreboards ... and the parts of the hull structure that they load up.

So not saying it won't work ... just that you might find some unexpected problems.

Michael Storer

I have checked out the Sika Technical documents and I guess it is quite different to the PU sealants other people (including myself) have used as glues as it is calling itself a construction glue rather than a sealant and there is no info there about expansion and contraction rates, or the Young's modulus, though I there is much more info like that on the TDS for SikaFlex 11FC for example. It may be a more a replacement for the Titebond or Gorilla glues.
Sika Australia Pty Ltd | Australia

I think I may experiment with it or see some real life road tests before I trust my world record speed puddle duck build attempt to it. I get these funny ideas in my head sometimes. It probably pays not to take me too seriously. Here are some examples of my earlier work.

Duckworks - The Ollie Punt ...and other Half-Sheet Boats - Part 1
Duckworks - The Jolly Olly - Part One

P.S. 5 Minute epoxy might not be so bad for things like emergency repairs as it does not stick too permanently (especially the cheaper stuff) and after a bit of heating from a hair dryer comes off relatively cleanly, unlike say gaffa tape which can be difficult to remove cleanly before attempting a propper repair.

Lashed out and paid the $14.95 for a standard construction glue cartridge to test it for myself and did a quick test at lunch time. Seems to be not quite what I expected It is clear when it comes out of the tube. It foams up like Vise (gorrilla glue), quite badly. Nowhere in anything that the company wrote about it did it say that it would foam. It only said it would not shrink or sag and may expand depending on the amount of moisture in substrates?. I made one join with a short piece of end grain butted onto a flat rough sawn board and one lap join with a slight gap completely filled by the glue. No clamping apart from the weight of the bits of wood - I would expect ordinary constuction glues to hold reasonably in these circumstances

9 hours later both joins fell apart to bare hands because the join was basically nothing but foam.

At the same time I tried one lap join with MDF and pine clamped together and it failed with the added chore of fixing one leg to my saw horse but the glue separated from the MDF. .

Tried to see what it would look like with fibreglass cloth embedded in it. It basically bubbled off the fibreglass. and finished with a separate layer of stuff simillar to heavy duty clear PVC over the top of the fibreglass cloth..

The blurb said it would dry clear but it dried with so many small bubbles in it white was a better description. The only thing I have not tried yet is a lightly clamped join between two bits of timber, which given what I have seen so far I would expect to work as well as my Vise boat building glue, which it seems to be behaving most like so far. I would normally expect to have glue test solid before I did a waterproofness test and fail afterwards.

So far not happy mr Sika. This glue is clearly very little like what it claims to be. It may very well be good at doing something other than it claims but that is beside the point.

Hi Guys, these were some basic test I did a week or so back using PVAs and Mr Sikas 30min goo.https://www.woodworkforums.com/f198/s...-tests-119072/

Thanks Claw Hama
Saved me the trouble of doing the clamped wood on wood test- no boil test yet though.

Overall might be a reasonable quick fix and may be waterproof but not really suited for anything structural, even if it does turn out to be waterproof. In particular, due to the foaming the gap filling was woeful. Sure the gaps were full, but full of air. From now on I will take the manufacturer's line with a 5 kg bag of salt. Boatmik might convert me to an epoxy user. Liked the explanation of 5% too little or 300% too much. The other trouble thing I don't like about epoxy is how expensive it is in small packs and how the price per litre drops in bulk amounts. The thing that is stopping me buying a big amount is that if I did I may find ways to use it. (too many things to do too many opportunities)

Nice table top by the way.

Thanks titchy
I will follow your glue progress too, its handy to know how all these things work in practice rather than manufacturers theorys and contrived tests.