We build carbon paddles and use a epoxy resin as weight, weight weight is critical.
To date we put a layer of clear 2K paint in the mould, let it dry and then laminate over it carbon first which becomes the layer you see when we demould.
We have been doing it this way for years but welcome any other ideas on an alternative to 2K paint.
Thanking you in advance.
I always thought such a procedure could only be used with heavy gel coat. Very interesting
Do you use a 2k poliurethane paint?
Yes we do use auto 2k clear coat which some use to spray carbon with, we just spray it directly into mould then laminate over it.
Gel coat is simply too heavy besides the adheasion problems with poly gelcoat and epoxy even though Scott Bader does have a poly based gel coat which works with epoxy, but in white only.
Try Duratec 904-040. It’s a solid polyester top coating resin that is sprayable through a 2.2mm primer gun. For a better result mix it 50% with duratec’s high gloss additive. Initiate with MEK9 at 1.2%, (that’s what I do) then spray. Make sure you can spray it within 5 min or so to make sure none of it kicks in the cup.
Will it work with epoxy? I’m not sure,you’ll have to talk to duratec about that. But I’m sure it, work way better than 2k urethane clear coat.
In what way?
This is interesting I have been trying to configure ways on changing my process from polyester gelcoat surface/polyester infusion resin to doing a polyester gel coat surface/epoxy used for my carbon parts.My biggest concern is a flawless finish.
I’ve stopped using gel coat about a year ago, reasons? 1.It adds weight…(about 1kg to a hood), 2.Spraying gel coat leaves orange peel which can be seen in the wave of the carbon as bumps, 3.In case of air trapment it shows like bubbles under the gel coat 4.Gel coat shrinks in high temperatures, leaving texture,. The way I’m making my parts is just raw carbon on the mold, after demolding few coats of clear, block sanding and re-clear, it adds hours to the job but it depends what you’re after. Also most of the supercars carbon divisions do not use gelcoats 
- Use better gelcoat. They are available up to at least 135 degrees C Tg. This should not leave print.
Same deal as up top ^ No gelcoat ever, been this way for years…we use to spray duratec, PPG clear, etc…etc…now, nothing, no clears, no gels, nada…
Now we just ensure the mould surface is the best possible result we can achieve and frankly, out of 10 parts - 8 are about perfect. It’s all in the surface quality guys, moulds are polished weekly.
They don’t last as long because the surface is wet sanded and polished wearing down the surface coat but in the end, we spend way less time finishing the parts off and because they can be a tad larger, the idea of spending hours upon hours wet sanding and clear coating gets tiresome. Plus, the guys get really proficient at making moulds when you are turning them over yearly.
I think these have 2 hits of clear on it, wet sand in between just to level it.
I have a rookie question, how do you stick the fabric to the mold if you doest no use clear gelcoat? sometimes molds have rare forms and fabric is hard to flat into it.
In a short time I will try my first infusion.
Respectfully.
Antonio
I spray a light mist of glue. make some tests beforehand, some spray glues work and some don’t
what suppliers of spray glue would work for it? so far i have used 3m 77 for other application.
this is all very interesting… i have been dabbling in my own carbon project since last summer with very little progress due to tight contours of my mold and different glues and many other things… so over winter i took a break and just recently started up on my project again… Ive been using an infusion glue (not sure on name at the moment) but ive noticed if the glue is alittle heavy in areas it seems like the epoxy doesnt like to adhere correctly or just bubbles in the area then brakes up in chunks after curing, this is my current issue and up for ideas that might cure my issue im running into… i thought maybe laying clear coat down first might help but after reading some of this it seems like clear should be done in the final steps instead of before. currently my process is wax mold, spray pva, infusion glue, carbon sit in, peelply,infusion mesh, then 1200uv epoxy ran threw then once epoxy reaches catch pot i turn off vacuum and let it sit under pressure over night… sometimes ill run a heat gun to the mold just to make sure i dont get any micro bubbles. any thoughts??