Material for the core of a fiberglass part

[srh3trinity]

I am thinking about trying to fab up some fender vents. Any thoughts on what material I should use as the core to work off of and start laying glass over? The vote would be integral to the part. I wanted to try this first as I believe it may be easier than making a mold.

[joeelutz]

There is a high density foam for that. Just be careful, some foams desolve when exposed to resins, like the pink foam insulation.

[srh3trinity]

I have heard about floral foam. It is hard to describe what I want to accomplish, but the piece will be pretty thin. I need to go see how thick of fiberglass mat is available.

[jlcustomz]

You could just masking tape up the area(s) you want to shape the vent on, spray foam insulation carefully in the area a little at a time making sure it doesn't fall before drying. then shape it to the finished shape you want. Then cover that part with plaster of paris to make a reasonably decent mold without taking too much time. 20 minute sheetrock mud is mostly plaster of paris,available at homestores. If you make the final part without any type of mold, it will eat your time up in bodyworking it & be a lesser quality part.
That's just my thoughts for one method for a mostly one time use method. I made a mold for my 2010 camaro nose to hood graft with sheetrock mud, scrap lumber , & free slightly out of date urethane caulk. I reused the mold to start making an underhood cover which I will post about later.
https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/noimg.gif
Sometimes the best answer is not the one you asked for.

[srh3trinity]

Good input, I figured my initial way would result in a lot of body work. The parts are small and flat, but will have a mild radius to follow the body line. I will have to make four altogether.