Fiberglass over epoxy adhesive (help)

hi.. i realize my post is out of place as this has nothing to do with boats but please help if you can
(the other fiberglass forum i found is not accepting new members at this time)
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so i'm building a loft in a bedroom and in order to keep a lowish profile on the railings, i've fiberglassed them for added strength..


the railings were attached to the post in a mortise/tenon style using a slower setting epoxy (30 minute working time.. 24hr full cure as per the label/instructions)


the railings were attached then left to set for over 24 hrs prior to doing the glass.. my problem is now, the glass won't harden in the areas near the joints (where the epoxy was used)..


it's been over a day and a half and it's still un_sandable in those areas..


the resin i'm using for the fiberglass is fibre glast's #83 polyester laminating resin.. the room is slightly cold so i've added a little extra mek (1tsp per 12oz as opposed to recommended 1tsp per pint)


it seems as if the polyester resin is melting or reacting in some way to the epoxy which is preventing it from curing..


so, anyway.. what do i do now???
thanks

[here's a link to a picture of the problem area..]

https://www.dropbox.com/s/z1kuwy5ocxm88bw/glassQ.JPG

 

If I understand what you are doing, the answer is clear. Polyester should never be used over epoxy as curing will be exactly what you are getting. Epoxy over cured polyester is fine but not the other way round. You have to take off the poly/glass and use epoxy resin, which you should have done in the first place. Sorry for the extra work but now you know.

 

tom,

thanks so much for the reply

you know, I'm just one of those people that always learns things the hard way

so, i have managed to cut back/remove the glass in the problem areas (roughly 1/2" all around the seams of the joints)…

i possibly messed up again but i did use some acetone to get the goopy stuff out and i'm nearly down to bare wood again.. (fwiw, most of the glass is fine right now.. it's just these joint area where the epoxy is)

since i have all the supplies to finish with the polyester resin, i'm wondering how bad of an idea this sounds to you --

finish most of the railings/post with the polyester while avoiding the joints then use an epoxy resin in those areas only?

if i understand correctly, i should be able to overlap the epoxy onto the polyester a little (maybe 1/4 " or so) and it will cure just fine?


i wish i could start over knowing what i know now but i can't.. those joints are done and aren't coming apart.. removing all the glass seems an impossible task at this point as well so i'd like to keep most of what i already have in tact (literally, 98% of the project is a-ok.. it's just these joint areas)


or maybe, i should just do an entire second coat using epoxy instead of polyester?

thanks so much

 

I venture to say that the glass at the very ends of your rails adds nothing to the strength or stiffness .. its the middle part that is aided by the glass. You can just leave the ends unglassed, feathered down neatly. Overcoat with epoxy resin to fill the weave of yr glass and then varnish over the epoxy (epoxy doesn't stand up longterm to UV so must be protected by a topcoat.)

 

thanks for the advice..

and that's the state it's in right now.. goo gone, bare wood exposed for approx 1/2" from the joints then feathered into the good glass..

i have some epoxy being shipped as we speak so it seems as if I'm good to go now.. (besides being a day behind now )

thanks for the help guys

 

Good enough. We don't learn anything from not making any mistakes:idea:.

 

Hi you already been told that the poly and the epoxy are not compatable so thats cool . The hand rail its self how do you intend to smooth it ?? You should have done the whole job round the other way glassed the hand rail and then epoxyed the joint . Epoxy is ok over poly but poly is no good over epoxy !! of simpler still do the whole job in epoxy !! then everything is compatable .

 

Tunnels recommends epoxy. 2013 definately will be a different year than 2012.... He deserves positive feedback for that.

But indeed, some epoxy resins inhibit cure of polyester resin placed on top (not even taking into consideration the adhesion factor). But not all epoxy behaves that way. Some epoxy resins are known to accept polyester topcoat over them, and when scuffed up good, the adhesion is enough for the job.

In this case I would just use epoxy.

 

Not just a pretty face

Thank you, thank you, thank you ,!!
No i have not changes my mind about epoxy its wood its being used on and its a stair case and hand rail .
These were areas i had a set way of doing everything and epoxy rails and posts in place for sure !!, all fitted together like a chinese puzzle and no screws or fastenings any where . Intricate joins that were pressed in place very dry then wet and vertually impossible to remove and never came apart
When i did wood flooring steps and stairs were my specialty and its amazing the amount of floor layers that cant get steps and stairs right and look natural looking . I use to premake everything on my work bench at home just 2 mm over size and then hand fit to a paper width of clearance till they just neatly fitted in place with the riser at the back and the nosing hooked over the top !! then glue and weight them down in place and leave for 4 hours . Gorilla grip and a hot gue gun ,i used to stick with blob of hot glue in each corner and gorilla grip fast cure the rest !! Start at the top and come down to the bottom . Anyone tried working with shredded Bamboo !!
Again Bamboo floors i speciallized in . making T and G Floating floors run in differant directions and mixing and matching colours
I blunt fine disc in a grinder is the only thing to use is slow and dosent bite and Bamboo has no grain just stringy as hell

 

You could use a tie coat and get a better bond with polyester over epoxy, but why?

 

Yes, there are ways to improve or avoid the bonding and cure issue but why get involved with inferior methods when the best way is clear and simpler.

 

Agreed . . .