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Have you ever wondered how resin casters get the masters for their parts? Me too. I know some of the masters are heavily (or lightly) modified pieces based on existing kits. Others are completely scratchbuilt. That's a bit beyond my skill level - I knew I should have been paying attention in high school art class - I'm not much of a sculptor.

It may be beyond my ability to completely scratchbuild a convincing replica, but what about a flight of fancy? I was inspired by the Grinnall Scorpion IV, the Morgan 3-wheelers and by a pic in SAE of one of Ricky Couch's creations. It seems Mr. Couch carved a neat little futuristic street rod from a blob of Bondo. Instead of carving from Bondo, I decided to work in clay first - mistakes would be much less traumatic.
Pick a shape and start carving!!!! This is what I ended up with. This is a mix of several colors of clay....looks neat, eh? looks sloppy, but they don't put enough of one color in a package.
After I was fairly satisfied with the shape, I made a silicone mold of it. Instead of using very expensive moldmaking RTV, I used silicone sealant from Wal-Mart. This is the "house brand" stuff, in clear. At aroud $3 a tube it is much less expensive than $33 per pound RTV. It's even less expensive, by volume or weight, than GE Silicone II. Silicone II is great for smaller parts. I hope to be doing an article on making molds with Silicone II in the near future.

I used most of the tube for this mold. Though it's not what I did, I would recommend building up the mold in several layers. It seems to dry faster using the layering method. This mold was one big blob of silicone over a blob of clay - it took nearly a week to cure enough to remove the clay master and it still wasn't fully cured (it was still "spongy" in spots, a sign that it isn't cured).
After the mold was cured another day without the clay master inside, I mixed up some Bondo body filler according to the directions on the can. The mold was filled with the body filler, making sure that all areas of the mold were well covered. This was done to make sure there were as few imperfections (air bubbles and such) as possible on the final part.
After about 45 minutes, the Bondo was sufficiently cured to remove it from the mold. The "overflow" of Bondo left a ragged edge around the bottom.
This shot shows a profile view, with the ragged edge still attached. Body filler is great to work with because, until it is fully cured, it stays a bit rubbery and is easy to trim. The ragged edge was carefully removed with a utility knife.....
....leaving this. There is still a lot of cleanup left to do as my master wasn't really smooth, but I'll admit I'm no sculptor. That is painfully apparent from the front view.....the master, and hence the copy, are a bit lopsided.
Here's a quick "set together" shot with wheels from a Copperhead diecast. The body needs to be sanded to get the shape closer and well as to even out the left and right sides.
So, I attacked the body with 100 grit paper. It sounds awfully rough, but Bondo gets very hard when it cures - and hard to sand as well. At this point a lot of material needed to be removed. The bottom surface was flattened with 100 grit sanding screen. The screen is open and therefore clogs much less than regular paper. The screen also seems to be very aggressive considering the grit.
A coarse file from my stash of woodworking tools was also used to get the body into shape for the first primer coats. There is more work to be done, but the primer coats give me a guide and improve the contrast - making it easier to see what I'm working on. I've often found small mistakes after the primer was applied, mistakes that were missed on bare plastic or putty.
To clean up the passenger compartment, as well as try to level out the lopsided cowl area, I used my homemade "milling machine" to remove excess Bondo. The "mill" uses a Dremel MotoTool and a 3-axis table I picked out of a dumpster at work. The rest of the "machine" is made from scrap wood. It's not perfect, but it works. I hope to have the alignment better in the near future - but that may be a moot point as I'm buying myself a drill press for my birthday. I'll probably use the drill press as a basis for a "mill" instead of something homemade. Then again, I may find a way to mount my Dremel to the drill press to do the same thing.

I used a Dremel 3/8" diameter cutter to machine the Bondo.
Here's the body after much more sanding and the machining of the passenger compartment.....and yet another coat of primer.

The engine is also visible from this angle Well, that and the fact that it wasn't there before.
Here you can see where the rear of the body was cut away to recess the engine. The engine doesn't stand out much visibly, but at this point it's fine. You really can't see the rear suspension (or what there is of it) at all in this pic. Currently it has the differential from a Hasegawa Mitsubishi Lancer Evo, but that will probably change.
Here it is with a set of wheels pirated from a Fujimi Porsche 911. Some sort of optical illusion makes the front tires seem taller to me. Really, though, they are smaller than the rears.

I think I'm going to modify the "dorsal fin" into something more like the headrests on the tonneau from an old T-bird or something. The fin was inspired by the Grinnall.....somehow....but it just doesn't look right.
This shows a bit more of the suspension and such, as well it should since it was taken of the underside of the car.
This shot shows the shape from above.
More to come!!! Follow the development of the "Sprod" as it takes shape!