I'm putting up a wind turbine. The turbine will be at the top of a 30' 1-1/2" pipe tower. I have a 30' RV extension cord (10ga/3 conductor) that I'm going to cut the ends off of and use as my down-pipe wiring. The wind turbine itself has a foot or so of 10ga stranded wire hanging down on the inside of the tube from the bottom of the turbine (three wires). They say that this wire can support 55# of downtube wiring (total, on the three wires), which is probably right, but I have my doubts that a crimped connector will hold that weight. The extension cord supposedly weighs 12# at its full 36' length, including the ends I'm going to remove, which are probably a pound of the total. Full weight of the 30' that will be dangling will be about 10#, but it has to be able to deal with twisting forces a bit too.
So, I know about the underwriter's knot, and how to tie that for three conductors. But I won't have any kind of stop in the pipe to hold the weight. The best I can do is tie the two sets of three conductors in a way that the wire is holding the weight, not the connector - like an underwriter's knot does. But what I'm looking for would be some kind of knot that's like an underwriter's on top of another underwriter's. Anyone heard of something like that?