I found a 100 ft clothesline looking on the web:
http://www.clotheslinesource.com/clo...lothesline.cfm
or one on amazon for 200 ft:
http://www.amazon.com/03871-ECLIPSE-.../dp/B000UGM6G0 If fact it looks as if there are several sellers on amazon.
It looks like an interesting project. I wonder if you could use those tube turners for this.