Sticking metal to plastic. Epoxy or Sikaflex?

[Kelpie]

I'm installing a windvane on my Wayfarer, and when fitting the little plastic bracket to the masthead the head sheared off one of the self-tappers just before it drew tight. I reckon the bracket isn't going to fall off, but it's a little wobbly. It only has to carry a 20 gram windvane after all!
I'm just going to stick the bracket to the aluminium mast to stop the wobbling, but I was wondering what to use- sikaflex or epoxy?
Thanks!

 

[Csail]

I would use Araldite.

 

[VicS]

It rather depends on what the plastic is. I think an epoxy such as Araldite will prove to be too brittle and won't withstand the differences in thermal expansion and contraction of the two materials. It rather use something that remains flexible.
Araldite does adhere well to many plastics unless the surface is properly prepared.

If only the head has sheared off can you not remove the fitting and get a grip on the remaining part of the screw with mole grips and remove it, reposition the fitting or drill another fixing hole?

 

[vyv_cox]

It can be quite difficult to get anything to stick well to aluminium due to the protective oxide film that forms upon it. I have managed to get Araldite to stick fairly well to it but I'm not sure about that here. As VicS has said, thermal effects might be quite significant at your masthead, and although the fitting may be light, the wind effects when heeled in a good blow are not.

If you can't get the broken screw out with a mole wrench or something similar I would cut off the broken stub and reposition the fitting slightly to avoid it, using a new screw.

 

[seumask]

I've had sucess with sikaflex in this sort of situation before, make sure you use enough and let it squeez out round the sides so you get a bit of support from the edges as well. I particularly like the fact that sikaflex has some give in it and wont detach at a small knock.

 

[jenku]

Duct tape!! /forums/images/graemlins/tongue.gif

 

[noelex]

I would be surprised if a glue will hold adequately given your description and I would try to redo the mechanical fastening as suggested.
If you must glue it Sikaflex 291 or even better 3M 5200 would be the best choice.
Epoxy is not good for plastics.

 

[RAI]

A super-glue might work, that Pasco stuff is pretty effective.

 

[Maurice55]

I would agree with Noelex, stick another screw in it if you have space and you will be sure.......

 

[psmonarch]

Drill a wee hole and pop rivet the thing in, they're dead easy to get off again if need be by drilling the heads off and strong enough to hold.