I want to simulate periscope lenses using the "exposed film" method wherein you glue rectangles cut from old film leaders onto the periscope heads to give a flat glass effect. Rectangles I can do, but what about the oval vison blocks in a Sherman, Pershing, M41, or M48 cupola? Has anyone successfully cut out ovals and used them this way?

KL

Note: Replacing the cupola with one of the clear replacements and masking the glass is not an option.

Hey Kurt, what I did was get some brass tubing with the inside diameter you are looking to make a radius cut of. Cut one end so you end up with a half circle, sharpen the outer diameter with a file and sanding stick so that it's got a fine edge. Only make the tool about an inch and half long, when the tubing is that small it will deform easily when you tap it with a mallet. Place your film on a piece of hard rubber and tap one side of your oval, measure to the other side, spin the tool 180*, tap again. Now make two straight cuts and you have your oval. It takes alittle practice, but works well for me.
Hope this helps ya!
Regards, Ed

I tried this about ten years ago for a build, and found it to be not worth the effort. I used the tool shown below, and cut ovals with the smallest oval. I still had to reposition it as the oval wasn't wide enough. The probelm wasn't in the cutting, it was in the mounting. It just never looked clean enough.
I finally resorted to Krystal Cote (of whatever it was called back then) for window openings, tinted with a pinpoint of green food dye. A little of that stuff goes a long way. If you still want to try it, I'd suggest you drill two holes in brass shim stock and cutting out the portion between them. Then you can make the stencil the correct length. I've made other little jigs this way and it works pretty well.
The tool: