I can't say that I have made any streamers for a long time without lying, but the control line combat guys use a different material. I think it is the landscape fabric. I am guessing that the proper length is measured out on the roll, and then it is cut to width while rolled up, with a fine tooth bandsaw or knife or whatever. The ones I have seen are about 1" wide, and the string is a loose sisal? or something like that, which is a bit thicker than what I would have thought. They go quite a bit faster than the SSC planes, so maybe a wing would not have the power to cut it like the Ukies?