Laminating epoxy to aluminium

[seahorse008]

Has anyone here ever laminated epoxy to aluminium? I'm redoing the mast step area on my J24, the mast sits on an aluminium beam which is laminated to the bottom the hull. The old poly fiberglass around the beam was tired and I'm redoing the area with epoxy.

The pro's seem to be using Plexus but its fierce pricey . West System do a #860 etch kit, and I'm using west epoxy so that might seem like the best option, but I was wondering would sikaflex 292 (which I have) be better to bond to the aluminium first? Then laminate the epoxy over that once cured? I'm thinking to use the 205 cleaner and 206 primer for better adhesion of the sika to the alu. The alu beam has a small bit of pitting so using the sikaflex first sounds better to fair the beam

 

[Ross]

It is really more of an encapsulation than a true bonding. You will probably get better results with vinylester resin. Clean the aluminum first with a power wire brush and then any recommended preparation and priming.

 

[Sailvayu]

Hate to say it but the Plexus is the way to go. It will truly bond to the aluminum. You might be able to find smaller quantities if you look for methacrylate adhiesive.

 

[Eddie7045]

I'd agree with Ross. Encapsulating an adheasive

is not a good idea. A good epoxy will bond well to the aluminum. Roughing the surface of the metal and grinding out any spots of corrosion will improve that bond. Avoid sanding outside the area to be bonded. This is a somewhat permanent fix so it would advisable to do it right and not have to cut and grind it out and redo it properly later.

 

[Tsatzsue]

I would think it is like lead. Wire wheel to shiny then wire brush the epoxy into the aluminum. This makes a non oxidized surface for the epoxy to bond to. Brush and tolls will never be used again of course.

 

[dlochner]

There are lots of J24s out there, this is likely not a new issue. Have you checked the J24 Class Association for advice?

 

[seahorse008]

Thanks for all the suggestions guys, the Sika 292 idea was clearly bogus. Had a look around the J24 sites and forums can't seem to find anything. I posted the same question up on the J24 class website anyway.
Ross you are correct it is more of an encapsulation rather than a bond under load. I'm interested to know why you would go for vinylester though, is it the stiffness of the epoxy compared to the alu?
Sailvayu thanks for the tip to find smaller quantity of methacrylate adhesive, following that lead.
Eddie7045 has epoxy on aluminium stood the test of time for you in a salty wet environment? I think eventually the laminiate would lose the bond from oxidisation from what I have read elsewhere on forums. I think that's why West System sell the etch kit which makes the link to the epoxy better.
At the moment I'm planning to either A. apply the etch kit then epoxy and colloidal silica mix to fill gaps, and laminate to that. Interestingly West recommend wet sanding with epoxy after the etch to stop oxidisation. Or B. a low cost methacrylate adhesive, then apply the laminate to that. B for Bulletproof I reckon.

 

[tommays]

While i am and epoxy person is does get expensive and the vinylester is the middle ground compared to basic polyester resin

Having owned two J24s the part does get worked pretty hard and the orginal had quite a bit of cloth keeping it in place

 

[shemandr]

I epoxy'ed a spinaker pole fitting to the aluminum pole with West System without much preparation and I could never get it out again - even when I wanted to. I'm a believer that epoxy bonds to aluminum, but I would do the prep as Rx'ed by West.

 

[Ross]

Remember that nothing too strong ever broke and weight added at or below the mast step is effective as ballast but doesn't get counted. I would make it as strong as I thought it should be and then add two or three more layers of glass.

 

[capta]

You might want to consider waiting until the mast is stepped as the whole area could change shape when it's up and the wires are tight.