Making an air scoop (or, What to do while the wife is out of town PART I
I thought I'd share the process I used to build a brake scoop for the Mirage. Lots of folks query me about how I do this, so now that I'm building a set of simple scoops, I thought I'd show it all from start to finish.
I wanted to insert brake (or internal fresh air) scoops on the front of the Mirage. After looking over everything that I had to work with as far as the nose of the Mirage, and the fact that I had already cut out the holes for the vents some weeks ago, I purchased floral foam from Hobby Lobby and carved/sanded the shape of the scoop (keeping in mind the fact that it had to be about 1/8" smaller all the way around to account for the thickness of the fiberglass that I was going to lay over it.
The foam comes in a variety of sizes, and for this project, I chose the brick-sized blocks, and then hot-glued them together as needed for the size needed. In this case, I had to glue two bricks together to get a large enough block to cut a complete scoop out of. Important note: plan as much ahead as possible on where you will be cutting material off for the final shape, and then avoid those seams with the hot glue. Hot-glue material does not sand at all (it's like a tough plastic), and if the glue is exposed in the final shaping/sanding, it will create ridges where it did not sand down to the levels of the adjacent foam surfaces.
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These are the bucks. Notice the fine ridge or line on the left buck about one-third of the way down from the wide end. This is where the hot-glue caused an issue (noted in text above) with sanding the parts to the perfect shape. This had to be trimmed with a sharp knife.
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Once the foam buck was completed, I laid fiberglass over it up to about 1/8" thickness. Floral foam works well in this environment in that it sands extremely easily (almost too easily), and it is resistant to the resin's solvent action. The down side is a dust mask is highly recommended when sanding it.
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After the glass kicked, I cut the scoop in half, and thoroughly cleaned out the insides of the scoop from all foam (easily done with a small paring knife and some 80 grit sandpaper). After the foam was cleared out, I brushed a fresh mix of resin-only onto the insides of the scoops. This resin coating creates a very clean smooth look to the interior of the scoop. Normally, when I fabricate a scoop, I simply pry/push/break up/dissolve the foam out of the fiberglass shell, and lightly sand the inside of the scoop (as best that my fingers will reach) without resorting to bisecting it, but this time I wanted to see if this additional process could be done without adding a lot of additional work (it was a success) or hassle.
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Once sanded, the resin glaze is put on the inside:
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With everything on the inside of the scoop looking good, I bonded the two halves back together again, taking care to v-groove only the round hose-attachment end so that it would remain the same diameter after the additional bonding glass was added to the joints. Again, the shaping of the foam, and the fabrication of the scoop took about three hours this afternoon.
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Continued on part II.
