These photos (22,23) show how I'm doing the body line detail on the bottom of the fender, I made from a strip of fiberglass sheet left over from a bathroom remodel, and some pieces of wood to fill in the corners, and used epoxy to secure the parts to the fender. If I were building a "real fender" of course I would use metal for this, but for a mold master the fiberglass and wood is very easy to work with and sand to nice corners. On the original Retro fenders I made this body line from 1/4" x 1 1/2" steel, bent around the corners and tapered with a grinder. I used a woodworking belt sander to round the corners to the roughly finished curve in 23. I'll fair this in with filler to match the look of the TJ front fender body line, shown in photo 24.
In photo 25, I'm showing with a 12" wide paint edge guide as a straightedge that I've made the surfaces slightly concave. This was to make it easy to get perfectly flat surfaces with the filler - there aren't any high spots in the metal since it's concave. For making a "real fender", I'd have made the surfaces flat and used minimal filler on them, but for the mold master it doesn't matter how much filler is on there, as long as I get perfect surfaces. I'll use this paint edge guide to trowel on the filler instead of small plastic spreaders. This more rigid and wide tool makes it easy to trowel on a pretty flat surface which will require minimal sanding.
Recall that I didn't finish weld the seams when I welded all of the sheet metal together, today in preparation for smoothing the surfaces with filler, I've backed up the seams with duct tape, shown in photo 26. With the tape is in place I can lay filler on the outside surfaces and the tape will provide enough support for the filler. Don't do this on "real" parts on your Jeep! - this shortcut is only for making the mold master.
I'm using Pro Gold Easy Sand filler (27), my friends at Elmira Auto Paint recommended it as being the easiest sanding product on the market. I don't care a durability here, since this is a "use once" mold master. They say this sands as easily as drywall mud... we'll see. The next post will show photos of the fender with filler...