I've made a start on the hood scoop.
The plug is still a bit rough, but nothing lots of sanding can't fix.
I took an off cut piece of polyurethane foam (surfboard foam) to form the plug.
I printed the side profile at true size of the front, side and top profile and glued the prints to hardboard, then cut 2 of each on my bandsaw.
I used these profiles on each end as a sanding guide, so I could sand until I hit the profiles to make sure the shape was uniform.
I left about 20mm extra on the bottom for shaping to the bonnet and making the trim line.
I mocked up the position on the bonnet then using a 20mm thick gauge block, ran it on the bonnet with a scribe to mark the profile of the bonnet along the bottom of the plug to get the shape of the bottom so it sits snug on the bonnet.
Then I glued strips on the sides and shaped them according to the profile line I traced.
I applied a thin layer of body filler to the foam and sanded it smooth to seal the pores of the foam.
I used good old polyfiller as a filler layer to find any low spots in the body filler as the colours differ to show up areas easily and polyfiller is easier to sand.
Next I'll smooth out the polyfiller top layer and apply the release, then a nice thick gel coat layer and 4-5 layers of polylite resin and chop strand matting to form the mold.
Once I've sanded the mold through the grits to 2000 grit water paper, I can apply release and mold the final part with a white gel coat layer, 4-5 layers of 5oz woven epoxy matting and epoxy resin.
Finish off with some 1.5mm woven stainless steel mesh to stop the troll sucking up leaves, twigs, rodents and small children
I'll post pics as I progress.
Once I have the mold I can pop out copies if anyone wants a scoop for a top mount intercooler.
On the underside of the bonnet I'll make a flat 'flange' surface and I've bought "D profile" automotive rubber to seal down onto the intercooler to prevent air loss into the engine bay.
It will also help the auxilary fan to suck air through the intercooler for when I'm not travelling fast enough or the intercooler develops a bit of heat soak from the engine below.