Sorry, you're wrong Jonesy. The knots strength comes through the fact you're using double the strength of your main line, as you leader is wrapped around the loop (if you tie it correctly)...
A Little History
In the heyday of big game fishing, back in the 1950's, giant Bluefin Tuna passed by the islands of the Bahamas in huge numbers during their annual migration. At this time the pioneers of our great sport regarded the Bluefin Tuna as the ultimate adversary in the ocean far more powerful and physically demanding than a Marlin of similar size.
Almost every item of tackle and equipment that we now regard as standard equipment in the big game fishing world was first developed to tackle these monster tuna, and by monster we are talking about fish that can top a 1000lb in weight. Bent butt rods, roller guides, lever drag reels, two speed reels, fighting chairs and fighting harnesses all came about because of the desire to catch these massive fish. Even the basic design of the modern big game fishing boat was first evolved in this prolific tuna fishery by such legendary boat builders as Merritt and Rybovich. Here speed and maneuverability were vital to stay in touch with the movements of the fish.
Another small, but incredibly significant, development of this era was a knot that has become known as the Bimini Twist, named after the island of Bimini where much of the history of giant Bluefin Tuna fishing was created. The sheer power of these fish meant that it was essential to eliminate every possible weakness in the tackle and equipment. The knot that was used to join the main reel line to the leader connection was one such weakness and the Bimini Twist was born to help solve this problem.
The Bimini Twist is not a "knot" as such. It cannot be used directly to tie on a swivel, hook or leader and it works by forming a double thickness section at the end of the main reel line. The significant property of the Bimini Twist is that, when correctly tied, the line retains 100% of its original strength. Conventional knots (blood knot, uni knot, etc.) reduce the line strength quite considerably due to their tendency to "strangle" themselves when put under heavy pressure. The doubled section of line that is created by the Bimini Twist is used to tie onto the swivel, hook, leader, etc, and a conventional knot can now be used as double the thickness means double the strength and this more than compensates for the loss of strength within the knot.
The Bimini Twist | Sea Fishing and Sea Angling Online[/QUOTE
Thanks for that mate, hopefully we'll meet up some time and I have the opportunity to show in practice what i am trying to explain. I appreciate that by folding your line and tying onto a double length of line it will be very strong, all i,m saying is you can achieve a doubled section of line without a bimini.