help on making fiberglass molds

[Memorytwo]

I would like to make a fiberglass hood for my Jeep.
what i want to do is add a small cowl or power bump so i can use an old style carb air cleaner. (theyre cheaper than the panel filters, and the V8 jeep has the TB at top anyways.)
And i want to taper the windscreen edge so it hides the wipers and is a bit more aerodynamic.

I would like to make a quick mold of the hood, with out damaging the hood, or painting over it etc. I would also like the ability to style the hood with such previously mentioned mods.

I had an idea of using minimal expansion homedepot "great stuff" foam, as a mold medium. I was thinking about covering my hood in painters tape or yellow masking tape, then spraying great stuff over it.

I prefer having about 2 inches for the power bump, and enough room to sculpt the aerodynamic taper. if expanding foam works, how thick would i have to let the foam be to have rigidity. and what should i do to prevent the resin from eating the foam. also i hear that expanding foam will continue to expand when i cut into it? is this true? how should this be resolved.

I also need this mold to be used on the existing hood, and be able to have the mold "finished" and off the hood within a weekend.

I know this is alot of contraints, but i dont see the point of getting a junk hood just to toss away. Also i dont want to damage my original hood, in case i want to donate or sell it.

Thanks in advance for your help.

-Andrew

[kane66]

Google is your friend......
Simple methods for molding fiberglass and carbon fiber

Ok I hate hearing that to but really there is tons of information on line about making fiberglass molds. What you might not realize is that lost of fiberglass molds are actually made out of fiberglass. The process usually goes something like this apply quick release. I think painters tape might work.... put I think the pro's use wax. Then spray that with gel coat, then apply fiberglass. Let harden and pop it off. and there you go one mold.

Don't use spray foam unless you want a mess.... it's good for attaching to thinks then carving, but it would make a flimsy mold.

[Tony Raine]

honestly, i would get a scrap hood. that way you can take your time and get it right, instead of having to rush.

gut the scrap hood (all the bracing underneath), but leave the hinge mounts and catch for the latch. mold your fiberglass on top. remove the fiberglass hood, cut the scrap hood up until its just a basic frame with all your mounts, then rivet the fiberglass hood to it. smooth to taste. keep in mind i've never done this before, but i have seen people mold generic fiberglass cowl add-ons to stock steel hoods.

[composite-aero]

Hi I just joined today and seen your post on the hood you want to make a mold off of. I am an experienced fiberglass mold guy. Before I help you let me know if you are still working on this project as it was posted october last year. Thanks Jason

[Ryland]

jeeps have plastic or fiber glass hoods already, right? so the idea of buying a used hood and modifying it is going to be the best and lightest way go to, and it will fit right.

[Memorytwo]

i dunno about the wranglers but i believe the ZJs, the model Jeep i have, are steel.

[rav]

None of the jeeps ever came with fiberglass hoods. Cherokee's came with a header and hatch that was fiberglass.
Ravi

[Bicycle Bob]

Another mold-maker here. You can wax a hood and pull a mold off it with no damage. You can also wax it and build up your modifications in something temporary before pulling the mold. You do want a smooth, shiny surface on any finished molds, and it is usually easier to do most of the work on the original shape.

[aerohead]

Is it possible to just relocate the cleaner somewhere near and run a snorkel to the carb?

[composite-aero]

ok what exactly are you asking?