Ok, heres the deal. I'm working on some widebody style fenders for my car. I need to know what you guys would suggest for making a mold of the fenders. What should I use to build up the fenders to make the mold? I thought about using styrofoam, or I could use bondo or plaster to make the original "positive" mold, then use fiberglass to make a "negative" mold of this. From the negative, I could make as many of the specific fender I want.

What I want to know is what way would work best. Using bondo or plaster, or using the styrofoam? I think plaster would be easiest to work with, but I've never done this before.

 

i know that hottub companies us ldf that glued together style of particle board available from most hardware stores, i have in the past used styrofoam, but beware the fibreglass tends to eat through styrofoam so try covering it with something first,
plus make your origingal negative, very thick, and very smooth you dont want trouble when removine the two pieces, so lots of suran wrap and vaseline, to ensure that the negative will remove from the new fender
just a few tips from my experience, also do the whole thing in small sections, when the fibreglass dries it wastes allot of ressin if you dont have it all used up,
better to take your time, and practice.

 

Try the blue foam board used for building insulation. It's pricey, but comes in thicknesses fron1/2" to 2". It bends nicely and can be sanded to shape. You can also glue up multiple layers for depth. Very easy to work with. Some brands will not melt when you apply the resin.

 

First make the part, fender or whatever. make it as you would like it to turn out, finished smooth. bondo, fibreglass either will do. next build a wooden box large enough for a front fender to fit in to with no top. at home depots they sell foam in the cans. great, good stuff is the name, one of them. apply a release to the part (fender) axle grease works well. spray a couple of cans of foam into the wooden box evenly and while the foam is still 'wet' push the part into the box making sure to cover the parts sides. let set them remove the part leaving a 'negitive' in the foam.
that foam is pretty tough and can withstand the resin. to make a part using the mould first coat the mould with a release, then gelcoat, cloth ( carbon or seaglass)
then resin. atleast 3 layers thick of cloth and resin.

 

Yahoo is a wonderful thing.

http://search.yahoo.com/search?p=mak...gle=1&ei=UTF-8

http://www.fgci.com/howto/ht003fiberglass_mold.html
http://www.fiber-tek.com/Bulletins/moldmaking.htm
http://www.fgci.com/howto/ht006estimating.html
http://www.fiber-tek.com/Bulletins/fiberglass_part.htm

 

you are correct sir...

 

Rx7carl took my local supplier that I would recommend Fiberglass Coatings Inc- fgci.com-.
If you use styrofoam you need to paint it with flat EXTERIOR house paint before you put any resin on it. A couple coats will do it. And any of the foam you would use will cut cleanly with a hot wire cutter. If you want the good stuff fgci has sheets of foam made for this work that can handle the resin, or look at their website and then try to find a 'glass supplier close to you.

 

yeah, the stuff in the cans is construction grade and can withstand a poly resin(s)
All the stuff a composite supplier sells is expensive. most rolls of cloth are 90 inches wide and a carbon fabric is around $ 28.00 dollors a yard, 36 inches X 90 inches adds up fast. just don't be affraid to try to produce car panels, fenders, hoods, etc. and remember the whole idea of a composite part is to save weight, just as strong as a stock metal panel but far lighter. and don't be discouraged if the first attempt fails.