The line being used for the main beam comes in spools 300 feet long, and has a tensile strength rating of 330 pounds. When you start running a line across a slew, 100 – 150 feet can go pretty quick. One trotline I saw awhile back must have been close to 200 feet long.
Lets talk about running the main beam line of a trotline. With the spools having 300 of line, your probably going to need 3, 4, 5 or even 6 spools of line for a SHTF stockpile. This of course depends on how many trotlines your going to be running. Some of the slews that I fish in are probably 75 – 100 feet wide. With 300 feet per spool, I would only be able to run 2 or 3 lines across a slew. If I was running a trotline across the main river, 300 feet would probably only get me 1 trip across the river.
About every 6 – 8 feet on the main beam I tied a loop knot. In the loop knot I put a barrel swivel. The first 8 – 10 feet of line is for tying around a tree. From the first loop knot to the end of the line, I probably put about a dozen swivels on the trot line. To put this into perspective, for each 300 foot spool of main line, your going to need about 2 dozen heavy duty swivels.