Hello all,
 I wrote late last year and asked if assistance could be give to make a mould for a F3 defuser. race car. and that a couple of attempts  had been made with a sad ending, and too the rubbish heap they went.

I have made a mould off the old defuser using glass etc.  and I thought I would use this as a mould for the defuser however, my troubles began when I used foam and carbon fiber to form the underneath ribs and when it was pulled down with the vacumm bagging process the ribs become out of shape under pressure.

I am no expert  with this process and I would appreciate assistance?.
Do you have to have  a split mould top and bottom to form the mould.

I would appreciate your comments, I will take a photo tomorrow and post it until then
Thanks
Sam

As Scottracing said, but i think id create the ribs as L-shaped plates (maybe T-shaped even), as the ones you already have.
That way you can use pop rivets to attach the ribs to the plate (as done today).
I recon after some use, running over the curbs and such the edges of the ribs will get alot of beating.
That way you can easily replace the worn ribs.

Also keep in mind what is over/under the diffuser, if exhaust, turbos or engine is close by, you might consider high temp resin.

If you are going to fix the fins on after then I would look at either a methacrylate adhesive, countersunk rivnuts (with thread lock) or back fixing floating K-nuts.