How to series by Jim Leininger
I make road race seats using metal molds. Here's how
to do it:
1. Bend flat sheet metal for the main base (the part you sit on). You can make a cardboard template, then take it to a heating/air conditioning business. They can bend up metal quick and cheap (even galvanized will work). Be sure to bend the forward corners with two 45 degree angles, for comfort. You'll be using the bottom side to lay fiber glass into.
2. Cut the UPPER REAR SECTION out of an old cruiser style or dirt bike style gas tank (whatever shape suits your tastes). Draw the shape of your tail section onto the tank, then cut out with a moto-tool and the little stone cutting disks (available at most hobby shops). Do NOT use tin snips. The inside of the seamless gas tanks are very smooth (good for molding).
3. Spread the sides of your "gas tank piece" to fit the back of your seat base. I MIG welded mine, but you could have it spot welded at a body shop.
4. Cut a piece of metal to fill the "bum stop" (front face of the tail piece). I leave a little extra on the front edge of the "gas tank piece" and bend a lip on the "bum stop" piece. This can be spot welded, spot brazed or even riveted.
5. Use body filler and your finger to fill the inside joint, at the upper and sides of the tail piece. I hope you see, you'll use the inside of the "gas tank piece" and "seat base/bum stop" as a mold.
6. Sand very smooth, then wax it well. You can use fiber glass cloth, and layers of woven roving, until it's thick as you need. Pop it out of the mold after it cures for a day.
7. Finish sand and paint. I sometimes cut an oval out of the back center (base/bum stop panel) to clear the original fender. Plan for that when you lay up the glass use extra thickness to insure stiffness. It's too much work to customize the mold .. just carve out the finished glass and add a layer or two if needed to close the hole.
These molds tend to stick a little, so I only get a few seats out of them .. but you can make complete new mold in about 2 hours . so who cares! Also . I upholster them myself using naugahyde (vinyl leather grain) and Zap glue (from the hobby shop). Triple fold a finish strip, using the super glue and set it aside. Glue on the bum stop face, then add foam and the base upholstery (wrap over the bottom edges and glue). Glue on the triple folded piece (over the edge of the tail piece) last, for a finished look. Lasts forever!
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