I’m very new to this forum and I’m starting a new thread because I just couldn’t find where there has been consideration of torque when twisting the two separate leader legs. Here is a thought and I’d really like some opinion before I try this. Seems there is a generally accepted standard as to 10% length reduction and then testing by twisting to the breaking point of the material being used. What if the twisting was done with a small power screwdriver that has a built in torque clutch. Mine is a Milwaukee model 0490-20 in 4 volts. It has a clutch setting that ranges from 1 to 21 with 21 being lockup for drilling. According to the operator manual, the #1 clutch setting will shut the screwdriver off when 3.3 inch-pounds of torque is reached. Now this is a screwdriver and not a drill so the clutch settings are much lower than on a drill. The higher you make the setting, the higher you set the the screwdriver shutoff. Therefore, the screwdriver shutoff can be incrementally set in steps ranging from 3.3 to just over 21 or 22 inch-pounds. So here is how I see this working. I twist the leader leg down to the 10% mark. At that point I have a stopper or barrier of some kind to keep the screwdriver from being pulled any closer to the holding peg. Then I keep twisting until I reach my preset torque level. After all, isn’t it the torque stored energy that causes the two legs to furl?
When will breakage occur?
That I don’t know yet. However, other posts would seem to indicate that you can pretty well see when the twist is tight enough so maybe I will not have to experiment too much. Ducksterman, you are an old hand on this forum. Do you recall anyone approaching the twisting of the legs from the torque perspective?
I do not DD. At least what you are thinking of. It will be interesting to see what others have to say.
You said…“Seems there is a generally accepted standard as to 10% length reduction and then testing by twisting to the breaking point of the material being used”
I’m not sure that is an accurate statement.
It’s all about tension… it can be applied a number of ways. Let’s use the hand held powwer as the example as I believe that’s what you are talking about. BTW I know someone who can get up to 17% reduction doing hand held power and applying the correct tension. 10% is an easy target and puts out a nice leader.
But what the folks are doing is applying what is felt to be adequate tension while twisting up to 10% reduction and stopping… during that twisting the energy is being stored . They have applied enough tension that they are close to the breaking point without pigtailing at 10%.
I think you might consider this. Use your torque idea to determine the breaking point of a given material and leader formula and then set future torque so as not to allow breakage before you got to your desired reduction.
In mechanical engineering (unlike physics), the terms “torque” and “moment” are not interchangeable. “Moment” is the general term for the tendency of one or more applied forces to rotate an object about an axis (the concept which in physics is called torque).[3] “Torque” is a special case of this: If the applied force vectors add to zero (i.e., their “resultant” is zero), then the forces are called a “couple” and their moment is called a “torque”.[3]
For example, a rotational force down a shaft, such as a turning screw-driver, forms a couple, so the resulting moment is called a “torque”. By contrast, a lateral force on a beam produces a moment (called a bending moment), but since the net force is nonzero, this bending moment is not called a “torque”.
This article follows physics terminology by calling all moments by the term “torque”, whether or not they are associated with a couple.
Thought I’d clear things up…
There were a “couple” “moments” in my life when I did get “torqued”! : )
I twist both legs to the 10% and allow the leader to furl and the leader works great so I see no reason to twist them any further than the 10%. I am not sure what you would gain from twisting beyond 10%. I would think one could twist too far and the leader would kink up “big time” when you do an steady pull to free up a snagged fly and it either breaks off or comes lose. Just a thought with nothing to back it up except “horse sense”.
Interesting question…
In the proposed method of twisting until 10% and then twisting more until the torque setting of the screwdriver is reached i think you’ll end up with a shorter leader then you expected. All the “extra” stored energy will be used to furl the legs, so they’ll get shorter.
As for the 10%, that’s about the best you can get with nylon monofilament with some safety margin. For polyester thread (guetermann tera 180) it’s possible to get about 30% reduction. This leader is stiffer and gives some trouble putting shorb loops in it, so i’m thinking of settling for 20-25% with this material. Don’t know yet what is possible with fluorocarbon.
Karel
Warren P;
Thanks for clearing that up. Ohiofly had me "DEEP" in thought. lol lol
Well this has been an interesting journey in the search of the mechanics for making furled leaders. I will not go into the wealth of scientific literature that I found only because I recognize that I would lose almost all readers and that is not my intent. Here, in a nutshell, is what I’ve found.
When we twist the fiber strands of each separate leg of the leader, we are creating stored energy in a bundle of fibers. When we twist too hard during this phase, for the amount of pull that we are applying on the long axis of the leg, the twisted bundle tries to untwist and that is what happens when we get a “Pig Tail”. My European and English cousins will probably appreciate more readily that this twisting of a number of strands into a bundle to store energy was used centuries ago in siege engines, such as the giant crossbows (Ballista) that used two bundles or the medieval catapult (Onager) powered by a single bundle of twisted ropes.
There are all kinds of calculations that can be generated using the form and function of a helix for bundles but I will not do that. Let us just say that the stored energy in each leg stays there until we either make a mistake and our leg untwists or we place the two legs side by side and then release the stored energy. When we control the release, the two legs will each untwist providing the energy to twist the two legs together known as the furling phase in making the leader. Using Kathy Scott’s method, you anchor one end of the leader and apply a weight to the other end to keep the leader from pig tailing. She notes and many of us have experienced that the total leader then twists one way and then the other for some time. Once that twisting has subsided, the control weight is reduced to just the weight of the S-hook. When the leader finally stops twisting, it has then reached a point of equilibrium where the stored twisting in each leg and the furling twist counterbalance each other. Now I ascribe to Kathy’s idea of letting gravity do the furling for me but I know many use power furling. You just would have to be careful and not over furl which would create more stored energy but in the opposite twist.
So, I think I have answered my own question. I can apply torque, that numerous engineering documents recognize as a mechanical term, which twists the fiber bundles in the two legs of my leader. I then can either use some longitudinal controlling force to allow the leg to shorten to, say 10%, of its original length OR I can twist the bundle down to a predetermined length and then stop the shortening and continue to twist until I reach a desired inch-pounds of applied torque. I would suggest that the second process would result in a more consistent stored energy given the same leader material over replications in leaders.
Again, I would appreciate any comments or corrections that anyone might have.
As the extra stored energy will cause the leader to shorten more(the first time you won’t know how much), i’d go for determining the length of a testleader using your method to find the % of reduction you got and use this percentage to calculate the untwisted length you’ll need for future leaders. Suppose this percentage will be different for different materials.
Karel
You are right and my next step will be to try this out. I’ll post back with everything I do such as material used, peg positions, strand pattern, 10% length, final pound-inches, and anything else I can think is of importance.
I think something is being overlooked here. How how taught are the threads/lines when the legs are laid up? That can change the Torque required to twist up the 10%.
(The Devil made me put this in!!!)
Jack,
Without rereading what he’s suggesting…I believe he is twisting to 10% then setting the torque…for “extra energy”…(The Devil made me put this in!!!)
DD why are you after “extra energy”?
Suppose trying to get some tighter furls in. Just a warning, don’t try to get to 30%, you won’t like the leader. Don’t ask how i know.
Karel
You are exactly right, tighter furl. I am also looking at that repeatability or consistency that I mentioned from leader to leader.
Hi Jack,
You are correct but this is why I want to include the torque part. When we lay out the legs, since there are different segments, we probably will not have the strand tightness being very consistent. At least I know that I am not consistent. Now there is a measurement device that measures cable tension. I see it used to measure the tension on control cables on bicycles. I doubt that one is made, however, to measure down to 4 pound fluorocarbon line or smaller threads. 
Shoot, DD, you played right into his hands:rolleyes::rolleyes:
But to forget about the tongue in cheek.
The more you do Kathy’s way the more consistent you will get. Jack basically does it Kathy’s way and you can bet his leaders are very consistent.
I say give your method a shot and let us know what you think.
Aren’t these supposed to be just plain old simple furled leaders?
I use Kathy’s Simple Furled Leader method and after several 100 leaders you will become very consistant.