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[tonyH]

I'm planning on using Araldite to stick wood bits into a fibreglass hull. I'm going to seal the wood with dope or sanding sealer, so is it best to glue first then seal or seal then glue?
Thanks
Tony

[chas]

I always glue then seal, it should give the strongest bond.
Chas

[coch y bonddu]

Personally I would not even consider using Araldite glue to stick wood to fiberglass


Dave

[SailorGreg]

Personally I would not even consider using Araldite glue to stick wood to fiberglass


Dave

... but loads of us have done it without any problem. Not sure what Dave's issue is, or what he uses, but for the stresses and strains of model boats Araldite (and other epoxies) seems to work fine.

[tonyH]

It's the first time I've used a fg hull for years
, so I am back on a learning curve again! What would you use then Dave?

[coch y bonddu]

Defo fav is Zap once it is on it is on.......Never liked araldite found the bond break far to easy


Next is Gorrilla glue


Or I will set timber in Isopon P40 the Fiberglass reinforced variety and not the car body filler


Dave

[DaveM]

I was always under the impression that the bond between a polyester resin-moulded hull and an epoxy adhesive wasn't very sound and that it's preferable to use a polyester-based compound like P40 - or polyester resin itself. I guess you could thicken it with micro-balloons. That said, if you seal the wood first then the sealer will inhibit anything bonding with it.
DaveM

[tonyH]

Thanks chaps for all that. I'd actually started with a couple of frames with Araldite and a 1/4inch fillet of P40 so I'll carry out the same method for the rest and heavier stuff like the rudder tube (It's a 20-25lb boat) and then Zap for the deck-edge stringers.
Tony

[Colin Bishop]

Bonding to cured polester resin by most commonly available adhesives depends on a mechanical rather than a chemical bond so it is vital to clean the polyester to remove any remaining traces of mould release wax and then roughen up the surface with a coarse abrasive.
Colin

[tonyH]

Hi Colin,
In this case it's all on the inside of the hull so there should be little or no release agent so a decent roughening should be enough.I'm pretty certain that I used Laybond for putting in formers etc in former times because we used it for putting gripper on concrete floors - so it was free AND it used to stick like S to a B

[Colin Bishop]

Yes Tony, you are right of course about the release agent so just roughening should be all that is needed.
Colin

[RST]

I must have missed something.  Since when was epoxy no good on GRP?  Never had any problems with Araldite, for anything really, but whenever I stray into other makes, or the "snot" purportedley being sold as expoxy for £1-2 and it's a different story (I do like Devcon though).  On GRP just de-grease and thoroughly rough-up and dust down.  I know some prefer the polyester "filler" types.  I've used them plenty, but they're more messy and smelly -they have their uses.  I quite like using rapid CA these days to hold the join, but chamfering the joint edges so it can be filleted with something thick afterwards, or even covered with rovings or tissue mixed in with epoxy.  Works fine for me anyway.

[Colin Bishop]

Quite right RST, there should be no problem with epoxy on polyester surfaces if properly prepared.

The standard treatment for repairing yachts suffering from 'osmosis' entails stripping the original polyester gel coat, drying out and then replacing with epoxy resin. It is a mechanical bond but quite OK in that application. I had it done on my 1:1 scale yacht years ago.

Colin

[nemesis]

I always use Gel coat to stick frames, battery boxes engine mounts et all, never had a failure. nemesis