The seat is so far the only real custom build part of the bike. I made it last year when I was for work in Germany.
With the Photoshop render I did, and a very rough model which represents the rear end of the frame and the fuel tank in Alias, I made a three dimensional model of the seat.
The seat itself sits on a 3mm aluminum plate. I decided to keep the base plate of the seat visible to pronounce the long straight line of the fuel tank and the lower edge of the seat.
With some dirty tricks I unrolled the surface of the base plate in Alias and created some curves for the milling.
To bend the big radius at the end of the seat I improvised with this little machine. I had my concerns how it will work with 3mm thick aluminum. But in the end I was surprised how easily and precise everything worked.
The bigger challenge was to shape the foam core of the seat. I could not really afford to 3d mill it, so I shaped it by hand. I made stencils of some sections and started to do the rough form with and automatic kitchen knife. That worked quite well for the first two minutes. Then the knife died.
I finished it with a saw blade of a hand saw. Wasn’t really a nice work. With an angle grinder I did all the free forming. In the end it worked not too bad, but I wouldn’t do it again like this. Next time I would try to get one of those professional upholstery saws.
Anyway, after clueing on a piece of foam in a corner where the angle grinder was a bit too rough the result was more or less satisfying.
Under the foam core is an piece of Alu Dipond. With epoxy I clued nuts on it. So later, it can be screwed to the aluminum base plate with lots of M5 screws.