Hey guys!

I need help making custom bolt-on widebody/flares in fiberglass. I have experience with fiberglass and molding making so making the molds and parts is no problem. I'm more trying to learn how to make the initial design (plug) in the first place. I've used urethane shaping foam before but not to this extent.

Can anyone tell me what the most common process and products people use to make parts like this? Foam? Modelling clay? Both? Any help would be greatly appreciated!!

My biggest issue is making the nice edges of the parts where they meet the body and the indents for the rivets/bolts.

This is what I'm talking about:

Chris will move this over to Fiberglas section.... but okay, it's like this... That to me is artwork in design there. I've done some molding and one off stuff but that appears to have been probably done on computer first, then done in clay, etc. Wayyyy.... beyond my skill set but hey, you've got some skills so I'm thinking you'll have to settle for urethane foam cutting and shaping. Building it up and getting what you want on one side for front and rear fenders, yeah, I can see that but it will be replicating the other side for balanced lines that will be the challenge. Large profile/contour gage would be needed, careful measuring, eyeballing, etc. I was building a kit car once that probably twisted as it shrank out of the mold. I made a wooden square kind of cage that I backed into and that gave me reference points on each side from my cage to the body so I could get the thing back in shape to the chassis. When you get the foam the way you want it switch to bondo for final surfacing. For those rivet attachment tabs, I think I would drill them in the foam, then bondo them out smooth into the shape. Once you've got everything layed up on the car.... well, you know the drill from here.....

you could try making a mould of the area of the car where you want the part to be from frp (fibreglass), then to get the shape, simply use some mdf or plywood and make a "buck" to form the shape (if you don't know wat a buck is, search the metalwork forums), get some polyester fleece material like wats used to make trackpants, pull the mould off the car and attace the buck with screws from behind the mould and then stretch the fleece over the whole lot to form the shape, glue or staple it in place and then mix up some resin and paint it on, the fleece will absorb the resin and when it sets up will be hard like frp, you can then sand it and bondo it to make it smooth and the final shape, then use it as a plug mould for your proper part!!
I used to make custom stereo stuff, door pods and sub boxes, dash bits etc the same way
for some good ideas and tutorials check out some of the car audio sites, you will be amazed at how simple it can be!!
krem