Is there a formula for figuring the strength of a furled leader?
Using a 10/8/6 step down you would have 6 strands at the tippet end…say you are using 2# material…I have a feeling it’s more than just multiplying 2 x 6 …you know …“the sum is greater than the parts”.
I have been told that the 6/0 unithread formula I use is approximately 10 lb test (6 strands at the tip). I have broken a couple trying to get flies on large tippets out of trees and that seems about right, but have not performed any sort of test to verify that.
I have not done any major testing, but, I did take one of my furled leaders that was made from 4 pound test flurorcarbon to a friends house to have him test it for me. He has the meter to test breaking strength on line because he is constantly testing his leaders/tippet for his salt water fishing. He does this to make sure everything he is using is correct in case he should catch a record saltwater fish.
We put a screwdriver in his bench vise, slipped the tippet loop end of the furled leader over it and the butt end loop on the furled leader on his meter. We then just kept a steady pull on the furled leader until something gave and that was the loop on the tippet end of the furled leader. According to his meter the tippet loop on the furled leader broke just a little over 12 pounds. The furled leader would still be usable since the tippet loop is all that broke. One could just make another loop in it and continue to use it.
I am suppose to assist him next week with teaching a fly casting clinic at the college where I am employed and I will make arrangements with him to do more testing at his bamboo/graphite rod building shop and can let you know what the out come is if you want.
Don’t want you to go to any trouble Warren.
Hhhmmm…I would have thought it might be at the least 4 x 6…though the Shorb loop could be a weak link???
Warren…I know you’ll understand…that Coats nylon we use .005 diam. could be 1# test and that might create a furled leader weaker than some of the tippet I use.???
Now you got me wondering about breaking strength! 
It has been quite some time ago when I done this and I may need to do more testing.
I am not a rocket scientist, thank God, but, when you make a furled leader, there are only 3 wraps around the peg at the end of the furled leader where you will make the Shorb loop. I know that when the loop is made it will be incorporated into the furled part that is made up of 6 strands, but, maybe that 3 strand area is the weak link in the system. The furled leader loop broke in the loop and not above the shorb knot. As the Shorb loop is pulled tight, in my mind, it is using the end of the furled leader which only contains the 3 loops. I doubt that makes any sense, but, I can see it in my mind, but, cannot put what I see into words! For my fishing, I only use either the 4 pound test fluorocarbon or 2 pound test fluororcabon. I figure that one will break around the 12 pound area and the other at 6 pounds.
If my friend is home this weekend in his shop, I am going over and break a bunch of furled leaders! 
I will let you know what I find out.
There are other parts of the furled leader that have fewer wraps than 3. The first transition section – 1st dowel peg – only has one loop on it. I have never had a furled leader fail at that first transition. If you’re having problems with the tippet loop, try using a short piece of 3x or 4x tippet between the furled leader and the fishing tippet. Always tie/loop the tippet to the 3x/4x tippet, instead of directly to the shorb loop.
Whatever the case, the tippet material should always be weaker than the furled leader material. If using thread leaders, I don’t go any heavier than 3x tippet. If using fluorocarbon (4 lb), I’ve used 10-20 lb Maxima tippet with no problem. BTW – with the fluorocarbon/Maxima combo – I always (almost always) use the Bimini twist for the tippet loop.
troutgeek…“1st dowel peg”…do you mean the one Kathy Scot calls #2 ?
Sorry – got ahead of myself there. It’s my 1st dowel, per how my board is set up. I think that is the same as Kathy’s dowel #2. My first and last “dowel” locations are actually hooks.
Got it…interesting point about the one loop.
I don’t want to highjack my own thread but it sort of relates…when one ties the knotted loops at the beginning and end…I’ve wondered if it makes any difference how big we make those loops? If the Shorb loops are a weak spot maybe making the knotted loop fairly long so that little knot is actually “outside” the shorb loop would be ideal…of course you wouldn’t expect there to be a problem at that larger end anyway.
I tied some up for a friend using the 14, 12, 10, 8, 6, but I used Uni 0/3 plus Kevlar.
I guess it worked:
It is an interesting discussion. Here’s what I think. 6 strands of 2# material equally loaded will break at 12#. Incorporating the material into a twist or weave will cause stresses and the break point will be less than 12#.
Here’s is what I think is the fly in the ointment. The #test is not always 2# to begin with. “Line Class” materials like Ande are designed to break at or below the stated poundage because your record attempt is voided if your line samples break over the limit for the line class. Other materials frequently break well over the “nominal” pound test of the line because the manufacturers, like Berkley, build in a little cushion. For instance I have heard of 6# breaking at 7.5#.
I would like to see what that fall off is from the true # test for straight strands (material not furled) to the # test for the same number of strands incorporated into furled leader. But, since the label is not a true idicator of the exact breaking strength of the line, samples of the line should be tested before furling to see what is going into the leader.
Just a thought…
I always hoped a furled leader was stronger than the tippet if I always used the right ratio and didn’t use too heavy a tippet. Am I wrong?
I don’t think you are wrong…and it’s those thoughts that got me to ask the question…e.g. I frequently use 3x Seagar fluorocarbon which if I remember correctly is rated 8.5 lb…all of a sudden I got to thinking the 2# furled leaders I am making might not be strong enough in that situation.