Need help making a CF/fiberglass hood! - Third Generation F-Body Message Boards

1983Fbody · 09-09-2005, 02:43 PM

My first attempt at using the hood as a "male" mold came out bad, the fiberglass piece came off warped and flimsy. I didn't have problems with smaller parts (bumper cover, fenders, etc.). This time around I plan on making a much thicker hood piece out of scrap fiberglass pieces then using that as a female mold. I'll also be using carbon/kevlar instead of fiberglass which should be much stiffer and less likely to warp. I've done a lot of reading on the fiberglass websites and found some helpful stuff I still have some q's-

What should I use to stiffen the undersides? I planned on making some small tubes by wrapping cloth over some cardboard tubes, then cutting them in half and molding them onto the bottom of the hood "skin" for strength.

If I make the hood with two pieces (top skin and bottom reinforcement part) like the stock hood, how could I bond them together?

Any ideas how to make the mounting points for the hinges, latch, spring, etc.? I thought of just using the steel pieces and riveting them onto the 'glass hood.

Well that's about all my questions/concerns as of now I'm still researching the subject before making another attempt. Thanks in advance!

-Ben

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Mathius · 09-10-2005, 12:31 AM

Chris (TPI383), used to know a guy that did CF, I remember him trying to see if there was interest for a group purchase or something. He might be able to help you out.

Mathius

83 Crossfire TA · 09-10-2005, 03:10 AM

Part of the issue here is materials and shapes. Curves and shape adds rigidity. Fiberglass is usually flexible, so if you make a great big basically flat piece out of it you’ll get something that will flap around and have no shape.

You can change materials (CF is VERY rigid, but brittle), add shape, you could change technique (glass cloth/woven roving laid on a bias between layers and even with something to take up space between layers will be much more rigid), add thickness, or make a female mold so you can add reinforcement to the back side (if you want a really pretty piece this is not as easy as you’d expect because where the reinforcement touches the outer skin you will see a “pull” in the final finish, especially as temperature/weather changes.

As far as making that female mold… I’ve seen people make frames and use plaster to make a big heavy piece that basically can’t flex. I’ve also seen taking a cast of the original with a FG piece with a lot of ribbing/bit frame added to the back of it.

Underhood reinforcement: hood manufacturers used to put hardwood blocks in the attachment points if it was a “bolt on,” I don’t know if they still do. As far as ribbing, there’s a few options, like balsa wood stringers that you glass over the top of (Corvette floors are made rigid that way), there is a special foam that is used to do the same thing in the boat industry (though a lot of that is balsa also). Looking at the glass hood on my WS6 piece, it looks like it was made by a chopped strand technique (and not a thick enough gel coat you can see the chopped strands through the paint) done in 2 separate molds, one to do the outer skin and one the reinforcement underneath, and then the 2 pieces were bonded together with an adhesive. The thing is super rigid (stiffer then all the steel hoods that I’ve ever dealt with), but it’s pretty heavy, probably about the same as a comparable steel piece (though you couldn’t get steel to bend like that).

my89 · 09-19-2009, 05:01 PM

"My first attempt at using the hood as a "male" mold came out bad, the fiberglass piece came off warped and flimsy. I didn't have problems with smaller parts (bumper cover, fenders, etc.)."

I know this thread is really old, but I am interested in trying to make a fiberglass bumper cover with a few minor customizations. Could you post a few pictures or explanations on how you made yours? This would be my first fiberglass project so I'm trying to learn as much as possible before buying anything. Thanks for the help.

HCR13 · 09-20-2009, 02:37 PM

wow, way to revive an old thread... you're probably not going to get an answer since the last time the OP signed on was Feb of 2008. Do a search and then just make a new thread requesting assistance, most people might just skip this one.