Polyester filler over epoxy?

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bigwow

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Having just laminated Bigwows new transoms on with epoxy, it went off fine but that might be because I put on 8 layers all at the same time, I’m having problems with the filler. Even after 24hrs the filler doesn’t pass the fingernail test, and at this rate will take for ever to fair off. Anyone any experience of using polyester filler over suitably abraded epoxy?
Thanks
 
You might be able to help the process by working over the area with a hot air gun. Keep the gun moving so as to avoid damaging the filler.
Good luck.
 
G'day John,

First of all there is not much that will bond to epoxy, other than more epoxy or epoxy primer.

Having said that, your poly resin should have been touch dry after 45 minutes and gloss hard the following morning. in cool climates you can apply up to 2% catalyst, any idea what ratio you used?

Meantime don't panic, it may take 5 or 6 days, if still soft, start to panic.

Avagoodweekend......
 
Too much use of hot air will soften the epoxy which might not be what you want.

I dont think that polyester actually sticks to epoxy very well in any case

The other way round works because the polyester of the hull that one sticks epoxy to is well-cured and free of odd chemicals when you go to stick epoxy to it.

Fresh epoxy can be letting off chemicals - like the amine bloom that can cause problems for even epoxy to stick to new but fully-cured epoxy.

I think there are three solutions

1. Wait several days

2. Scrape off as much as possible, mix up new polyester filler with _fresh_ hardener and apply - the new catalyst in the new filler will help the older filler cure.

3. Scrape off as much as possible, wash and abrade, then go and buy a bucket of microballoons , and mix with epoxy resin/hardener and use as a compatible filler .

Option 3 is the one I would prefer ...
 
Good morning oldsaltoz
I used epoxy resin so could not alter the mixing ratio, The laminating, with epoxy went fine, off in 24 hrs, it’s the epoxy filler , I’m mixing epoxy resin with micro balloons, that is taking forever to go off.
 
Epoxy should be allowed to post cure if you are going to fill with polyester and as you are outside this couldtake a long time the best "fix" would be
Scrape off Polyester filler and abrade with course wet and dry using fresh water then fill with epoxy fillers using resin and microballoons
to overcome temperature problems make a polythene tent around the area and heat using a small fan heater
In my book you never put overcured resin probucts over undercured unless you want disasters,.
 
In that case you could try heat but it is unlikely that you you will get a 100% cure now
When laminating you had the benefit of generated heat from multiple layers ,your filler wouldnt have had that benefit
what was the hull tempereature like the day that you filled it ? substrate temperature can be all important.
 
G'day John,

When I read
<Anyone any experience of using polyester filler over suitably abraded epoxy>
I assumed you had applied poly resin and filler.

Don't panic, the epoxy will cure after time, max 7 days. You could shorten this with heat lamps, just keep an eye on the surface temperature, 40* Degrees C is fine but not over 50. That's a 1000 watt about 1.4 meters off the job.

Avagoodweekend......
 
I don’t think I made clear what I’ve done up to now, I haven’t yet used any polyester filler, I was asking about the feasibility of using it as it goes off in under 1 hour, which would make this job about 2 weeks quicker the way it is going at the moment.
Progress so far:-
I laminated the transoms on using Epoxy resin slightly thickened with colloidal silica, 8 graduated layers, this was off after 24hrs
Hole was drilled in the top and the void was filled with 2 pack foam
After washing and abrading the laminate
I mixed some filler, Epoxy resin with Filite, which I’m used to using with Polyester resin, but it was too rough so I scrapped it off and mixed some more with micro balloons and silica, this can still be indented with my fingernail after 2 days.
It is at this point that I was asking if polyester filler would be an alternative.
Sorry for the confusion

pic of what I'm adding
porttransomwithhandrailsfitted1.jpg


The rough bit on the top step is where it is rebated for joining.
 
G'day John,

Would advise not to use poly resin over epoxy, fine the other way round though.
Your epoxy will cure.

I also note'
<<Hole was drilled in the top and the void was filled with 2 pack foam>>
Is this a 'closed cell' foam? or will it turn to mush if it ever gets wet?

Nice job by the way, well done.

Avagoodweekend......
 
Yes it's closed cell foam and will only take on water if it's crushed first, if it ever gets crushed the foam getting wet will be the least of my problems.

By the way I'm not Avingagoodweekend it's piddling down yet again.
 
Microballoons or microfibres can be used with epoxy or with polyester resin but I note that you have not used any polyester resin, just the filler.

I'm not familiar with the Filite or filler you talk about using but epoxy can be a real pain to harden properly if you don't apply heat. Maybe there is something in the filler you have used that isn't good for epoxy but this seems unlikely.

In our climates, you should be doing this in dry sunny conditions. If you can get direct sunlight on the epoxy that can be ok in the afternoon but it may go off too quick if it's the middle of the day.

Currently, I'd suggest getting a fan or infra-red heater and pointing it direct at the epoxy for at least 3 hours and by that stage it should be fairly solid. Protect the area from wind will help the heater work.
 
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