I was shooting with my Graflex C today and the shutter cloth came free of the bottom roller. Quite a sound. How do I reattach it? What kind of glue should I use? The cloth itself is in good condition and it seemed to have come off cleanly, there is nothing on the bottom roller at all. The more I use these guys the more I learn.

Upon further inspection the news is worse than I thought. The curtain tore just at the 3rd slit. I have a 3x4 curtain from another camera (a super D) that I think I can transplant. Am I correct in thinking that I cannot repair this curtain?

Yes, the curtains should interchange.
To attempt a repair of the torn curtain:
Remove the stay at the tear. The stays are copper, they open easily with a wood chisel and the V of the stay on a solid surface.

Cut two strips of repair cloth of equal size and bond to one side of the curtain. The repair strips should extend 1/2 inch minimum either side of the tear. The maximum curtain thickness Graflex SLR's can handle is .025 inch. Equal amounts of repair material must be applied to both sides of the curtain to keep it winding evenly.

Reattach the curtain stay. Crimp with the smooth section of a pair of needle nose pliers.

Recommended repair material is shutter cloth, bellows cloth .008 thick, nylon, or polyester.

Contact cement works well, non flammable preferred.

Thank you, maybe I will go that route, if I can find some material for the repair.

I removed the curtain pieces today, leaving the top roller in place as of now. Comparing it to the Super D roller it is a little longer, and it looks like the Series C has a larger diameter top roller than the Super D. That may explain the difference in length. The Super D curtain is in very good condition so that is in it's favor. The torn curtain is still quite supple though so a repair may be just the thing.

To do the swap I'd have to remove both rollers and that means removing the pin that holds the mirror lever which I learned is no easy task. A repair would avoid that and I know that the length and spacing would still work. I'm worried that with a swap I might run into trouble with the curtain spacing.