New here/wanna mold a BIG hood

General Composites Discussions Composites Talk
#1

Hello guys, like the title said I’m new here. I got a Firebird with a hood thats about 5’x6’. I’d like to replicate it in CF. So I got a few questions.

First; Is it possible to hand lay CF? Will it look ok? It’s pretty big, which has me wondering about infusion. Can I pull epoxy that far?

Second; How straight does my plug(original hood) have to be. Can I finish a CF hood? Sand, Buff? I got this really big sticker on my hood. And I figure I’ll have to cut the hood apart for the bottom(frame) mould after I mould the top. Rendering it junk anyway.

Third; What should I put my blank(hood) on for initial mould? Is formica laminated plywood ok?

Fouth; Would black fiberglass be a smarter choice? I want it nice enough as to not have to paint it. Are U.V. resistant epoxys avalible to me for glass or CF? What are the vices to not having an autoclave for CF?

Also If I managed to pull this off. I’ve never owned any CF before so: I wouldn’t have a CF hood that’s so strong it it sheers of my hood catches in a crash, doesn’t fold/buckle and slices through my windsheild and head? Would I? I plan on using just a initial layer of CF and the rest glass. How many layers are good? Strong enough not to cave at 80mph and as light as possible. Should I leave nothes in the underside hood frame for impact folding?

#2

I could answer with a couple pages of info, but the best advice would be to just practice making some small parts.

#3

I hear ya. I should get as much practice as possible. I’ll read up as much as possible too. Thanks.

#4

yep start small I am, I have just sprayed partall to make a mold and just got a run in the partall that did not come out now I need to start over clean off the part and start spraying again thank god this was a small part.

I rushed it and didn’t let it dry enough between coats.

Mark44

#5

the first thing to do would be to take the hood off and send it to a bodyshop to be painted, both on top and underneath.

take the time to read on about other similar projects. start with lots of small stuff, you will learn lots of stuff.

the hood u used will not be junked, the worst thing that might happen is paint might chip off somewhere.

you can hand lay carbon, however its a bitch to get it to stick in corners like around the edges of the bonnet. you can use some tricks for that. basically it depends on the flange around your mould… one trick is to spray a layer of clear gelcoat and when it becomes tacky, lay the carbon on it so it will stick and not move. and then lay your resin. if you make OEM-like subframe , then for the top skin , 1 layer of carbon and 2-3 layers of woven fiberglass is strong enough. another 3-4 layers of thin fiberglass for the lower subframe , glue the two together, and you are king.

if you get bubbles around the periphery of the bonnet, you can drill them open with a dremel, fill them up with resin and then sand and clear coat the whole thing.

but nothing beats experience. be prepared to throw away a lot of stuff, you wont learn otherwise.

hope i helped.

#6

yep, i’ve been doing this for about 8 months or so and I still have junk parts i end up tossing. Sucks for sure.

#7

In reference to having the hood painted. Be carefull what paint the body shop uses. It can react with the resin. Especially the solvents. I learned the hard way that acrylic paint and epoxy dont mix well.

Theres a reason most tooling surfaces are polyester or epoxy. Takes the “will there be a reaction” factor out of the picture.

#8

i THINK i used epoxy to paint the mould. i know for sure i got epoxy clear coat yesterday…

#9

Would urethane automotive paint be okay?

#10

duratec black hi-gloss works great for plug surfaces

#11

No, you don’t understand my question, duratec(as you know) is polyester, I was asking jrl if urethane paints react to toooling materials. Urethanes do have some advantages, such as shelf life.

#12

After having a bad reaction with Acrylic paint, Ive been hesitant to use anything other than poly based finishing products. Never tried urethane on a plug. My only experience with them is finish painting.

I believe that Duratec came out with a shelf life extender, or something to that nature. Although Ive never personally tested it or seen it.

#13

When I made a mold of my hood which was sprayed with base/clear, the tooling gelcoat reacted badly with the clearcoat.

Doing a search, I later found out that most of the time, it will react badly (my post should still be somewhere here on this site). I was hoping the wax and pva would be enough but it wasn’t…days and days were wasted getting the hood stripped and smooth again.:mad:

#14

Fastrr,
I read the “instant email update” of your post and thought it was pretty damn relevant to this thread:)

You didn’t have problems, I did. My hood was painted 5 years prior to the mold making. So, to the original poster, do a test on a small, inconspicuous part of the hood. Your mileage may vary.

#15

so in the end, epoxy and polyester paints = good , acrylic = bad?

#16

Mine was a 2 stage poly urethane

#17

Polyester has been the standard for plug finishing for a long time.

In terms of spraying poly, a pressure pot is the way to go. Gives you much more spray time.

#18

[QUOTE=REZCAR;18277]When I made a mold of my hood which was sprayed with base/clear, the tooling gelcoat reacted badly with the clearcoat.

I assume you were using polyester tooling materials? I wonder if the same would apply to epoxy? I was thinking of taking some moulds off the wife’s car and I’d hate to destroy the paint!

#19

Do you have a photo of your pressure pot set-up,I’ve never used one of those.

#20

Wish I did. If you call Duratec, they can transfer you over to their lead tech. He will give you all the details in how to set one up, including which gun to buy, needle size, and what pot set up.

My old boss was to cheap, so we stuck with the HVLP gun. Spray, clean gun, repeat, is no way to paint a plug.