Re line strength of a knot...
Any knot in a line will weaken the line.. be it a fishing line or a rock climbing rope
It is therefore std procedure that when choosing a line or rope, it is done so taking into account the type of knots going to be used and how much the reduce the effective working load of that rope.
So lets apply that to a ledger rig, and tie in a knot X that is rated at say 60%
Your requirements is a strength of say 20 lbs, so you will choose a line of 35lbs.
The effect of a given knots lower rating has no effect on the end use.
Knots of very high rating enable very light lines to be run.. eg a FG on very light soft bait rig.
So I have been advised by local knowledge , tie up the dropper rigs with 60 or 80 lb ....
So I opt for 80lb. and lets say the knot(s) are 60%
That give me a strength of about 50lb off the top of my head...
Thats a pretty big snapper.
So applying that to the real would .. today over the bar...
And yep we broke off 3 hooks.. on about 55 to 65 cm snappers.
And we broke those simply because those snaps teeth went right thru the fulro rubber sheath, and thru the doubled trace , between the back bone and hook..no knots in between.
So in essence in the real practical world of what dropperloops is used, at the end of the day it is the sharp teeth (or reefs etc) that will determine the weight on the line.
A lot is made of knot strength with very little if any thought put into the application of fishing.. unless maybe someone has applied these basic principle in the past to climbing rock faces.
All the videos above are simple droper loops .. the one on the machine just introduces an extra strand inside the knot.
The last shows several ways to tie the same knot... the peg board is what I describe in my post above..
Taking the alpine loop is just another way to tie it .. just making it real simple
An alpine loop is a world wide std knot recognized by military, and civilian riggers, go to knot, be uit used as a loop or joining knot. Adding more loops around the back bone doesnt weaken the knot.. it spreads the load on the line away from the main pressure points