Polyester Resin Fixings

[Barreller]

Has anybody got any experience of fixing into wood using polyester resin? I need to bolt down a 150mm oak frame to a glulam (softwood) beam and would like to use threaded fixings (Fischer). I know how well they work into masonry or concrete, but do they work in timber?

Steve

 

[A_n_g_e_l_a]

Well, seeing no-one else has much to say let me offer these thoughts. I've only used polyester resin for canoe building (lots of..). One thing I noticed is that the unreinforced resin is very brittle - almost glass like. That would be the last thing you needed in a joint in wood under load.

My inclinations would be to explore the use of Araldite - an epoxy resin. I haven't checked but it has probably got a better Young's Modulus value, (a measure of elasticity), than polyester resin.

There is a glue for every purpose - it's just a case of finding it! Good luck.

 

[SketchUp Guru]

I would also suggest using epoxy. If you mix in fumed silica to make a thick putty, you'll have an exceedingly strong point for a fastener. You could seat the threaded insert or you can fill an oversized hole with epoxy and after it cures, drill and tap for the bolt or you can lubricate the screw lightly--spray on cooking oil works--and put the screw into the epoxy immediately before it kicks off.

I prefer drilling and tapping for that sort of thing. Especially if the location of the hole is critical.

This method is frequently used on boats to provide mounting points for cleats and standing rigging attachments. Very strong.

 

[inventor]

These folk
http://www.epoxy-info.co.uk/epoxy_rods_connectors.htm
have a system for repairing broken joists using steel and epoxy. They say it works in glulam too. They'll have the right stuff if anyone does. I've not used their system, but I have heard a structural engineer recommend it.

 

[Barreller]

Thanks for the suggestions guys. I'll post the conclusion but am not sure that the Young's Modulus of Araldite is that good. It always seems brittle to me. You have started me thinking though. West System might hold the answer.

Steve

 

[Steve Maskery]

I've no idea if this system is of use, but when I made the chair in my avatar, the seat structure was bolted to the laminated back by burying in to the back 4 nuts called BigHeads (www.bighead.co.uk). I asked for a few as samples and they obliged. They work like a standard embedded nut, but a washer welded to the back make it virtually impossible for them to pull through, making a very strong mechanical fixing.

I'd certainly use the system again for anything suitable, very pleased with the results.

Cheers
Steve

 

[RogerS]

Steve

I needed to glue a 20mm threaded stud into the endgrain of an oak beam. Technical support in Araldite recommended Araldite 2011 which you can get from Buck and Hickman's website.

He also answered the question posed elsewhere and that was that the recommended gap between the stell and the hole was 0.2mm for max strength. IE I should drill a hole 20.5mm diameter.

He also said clean the hole and steel with ethanol (or similar such as mail varnish remover).

Can't recommend their tech support highly enough

 

[SketchUp Guru]

He also said clean the hole and steel with ethanol (or similar such as mail varnish remover).

You Brit's varnish your mail? :shock:

Sorry. I'll get me hat. :lol:

 

[Barreller]

Thanks Roger. I'll try that.

Steve

 

[Barreller]

Just to close the thread I actually used lots of long coach bolts for the job.

Leaving that aside many thanks for all the advice which I am sure I will use in the future.

Steve

 

[Racers]

Hi, Dave R

We all have butlers who varnish our mail so we don't get our hands dirty.

Pete