Hi guys first post on this excellent forum,
Can i put a thin coat of polyester gel coat on my mould surface to stop print thru then when thats set do my CF layup with SP 115 epoxy ? or will the poly react with the epoxy and muck up ?
For vacuum bagging by the way
Thanks…Matt
works fine.
Wait for the gel coat to cure a bit longer before bonding with epoxy.
in the company’s product guide, it says let it b-stage… i ve done that with no problems, though i let it totally cure (at least a day) cause the carbon sticks too much on the gel, and i can’t move it around…
Some are compatable, some not, although it could be that they are not because of not waiting long enough between coats…
There are also specific PE gelcoats on the market which are listed for use with Epoxy.
ok thanks guys, what does PE stand for ? also what are these gel coats called for epoxy ?
just took another piece out of the mould and its done the same as the last one, it looks like the carbon hasnt been pressed flush with the poly gel coat where the strands cross over each other,
gonna do another piece later or tommorow and maybe try something different again, problem is the clear epoxy isnt thick enough to use as a first coat so that the finished part is nice and smooth with no print thru so i have to use clear poly gel coat which i dont know if its causing the funny effect with the carbon if you get what i mean lol
Matt
Like?
PE = Polyester Matt. 
Scott Bader do some Epoxy compatable gelcoats, look at ‘Epoxy Bonding’ on this list here:
http://www.scottbader.com/assets-datasheets-composites.html
This is one of them: http://www.scottbader.com/downloads/UK_PDF_Datasheet_Files/Gelcoats/251PA%20-%20Feb07.pdf
Is it possible you could post up some good quality pics and a write up of exactly what you have done and what the problem is? If you can there will probably be someone on here who can help.
Don’t worry just proceed. 
I make it in the past many times.
OK guys heres the pictures as requested, these are 2 new pieces that i pulled yesterday and its done the same again, you can see in the pictures its as though the carbon hasnt fully pressed down onto the gelcoat,
and these are the 2 pieces that im trying to currently do,
the only thing i can think of thats causing this is the poly gel coat ? the resin used for the lay up is SP115 epoxy
used peel ply, release film and breather, used more than enough resin on it as the peel ply and breather cloth soaks up loads of excess
help lol
Matt 
probably your gelcoat isn’t compatible with the epoxy you;re using, (weird I know) but I had the same problems few months ago
I agree and have had this happen to me also. The resin and gel coat you are using are incompatible.
That is the exact look you get when the two don’t mix.
ok, so i need a new gelcoat lol
anybody recomend one please for see thru carbon parts ?
preferably without shipping from the us cos it costs a ??? load lol
Matt
I have stopped using PE gelcoat with epoxy laminates. I tried it a few times with no success, just an expensive waste of carbon fabric. What i do now is choosing a fast curing epoxy resin (20min), lay a thin film on the mould, pay a lot of attention to the film while curing because the film tends to break and leave spots without resin (this is due to the wax on the mould i assume). When the film gets to the tacky stage i start laying up with carbon and epoxy. Very good results.
hrmm… I thought you had to let the PE pratically fully cure before you could apply epoxy to it or you’d end up with what you have there.
PE gelcoat will never fully cure on its outer surface. Only if you use topcoat resin. I wouldn’t go to this route ever.
which epoxy is that you use now with the 20 min cure ?
this is doing my head in now lol
Matt
Ooops… i meant pot life, not curing time… :o :o
Epoxy 481–> http://www.fibermax.eu/shop/product_info.php?cPath=26&products_id=211
with hardener 172012–> http://www.fibermax.eu/shop/product_info.php?cPath=26&products_id=212
You have to work really fast though.
duratec VE topcoat will probably be your best bet for a surface