My Understanding of Leader dynamics

[gkieser]

I mentioned a leader formula for casting into wind in another thread and was asked to elaborate on leaders etc. This thread is just how i understand them. I am not sure if this is 100% scientifically correct, but to me understanding the transfer of energy in this way helps me to understand what types of leaders will help me best in my fishing. I am posting this with trout streams and lighter weights rods in mind but the logic should be transferrable to all types of fly fishing.

We concentrate a lot on the perfect rods and lines for our stream fishing, and i guess this is rightly so since these are far more expensive than your leaders. Your leaders do however have a significant impact on your ability to fish effectively on small streams.

In my mind, the prefect leader for dry fly fishing is simply one that can help to turn over a fly and present it delicately and accurately in the prevailing conditions. For most of us, we have a single rod to fish the streams with a single fly line (as mentioned these are expensive things). Your leaders are something that can be easily changed at far lower cost and effort, and in my opinion the versatility of them is something that we should all take advantage of to make our rod and line achieve the goal when conditions are against us. This is far easier than carrying two different rods in case the wind decides to change direction half way through the day, or even worse, like often happens on the elandspad, where the wind will change direction regularly throughout the day.

I started to understand leaders more after MC wrote his article on French leaders in a Piscator a few years ago (some of it posted on flytalk in this thread. The article was about the Pascal Cognard range of leaders which were made of different diameters of line tied together in different lengths. Some lengths got shorter and shorter as the diameter got thinner and some got longer as the diameter decreased, with the former being used for windy conditions and the latter for more windless conditions.

So here's the Science as i understand it:
As we cast out our line, energy is transferred down the line, into the leader and into the tippet and ultimately to the fly. As energy moves down the line, some of it is lost to the action of straightening out the line, so the further it has to travel, the less energy is being transferred forward. In order to keep up the momentum of turning over the leader, the leader is tapered thinner and thinner so that the amount of energy moving along it is "squeezed" into less and less space. This means that the ratio between diameter of the leader to amount of energy in the leader is maintained at a rough constant (for a constant taper), and so the lesser amount of energy in the end of the leader is concentrated enough to turn the thinner leader over.

This is the problem i have with a tapered leader bought in a store. The taper is (and i am guessing here) constant in order to transfer a standard amount of energy. This is usefull in normal conditions, but won't help you in all conditions, and for me it is therefore important to try and alter the energy transfer for different conditions.

If, in a drastic example, you used 0.37mm mono and tied it to 0.20mm mono, at the point where the energy moves through the knot, the energy moving through the line gets concentrated into the smaller diameter, and should therefore accelerate the turnover of the 0.20mm piece and the fly should come crashing down on the surface. At the same time if we started with 0.20mm and went to 0.37mm, the energy moving through the knot suddenly gets dispersed and the leader will start to turn over a lot slower, and could possibly collapse and i think this is how the popular reverse tapered leaders used by some guys at the moment helps with delicate presentations. At the same time, instead of reversing the diameters, you can lengthen each piece of line as you step down in diameter, meaning more energy is lost before you step down in diameter.

Here's some examples:
1) Leader for delicate presentations in windless conditions:
0.37mm - 100cm
0.32mm - 40cm
0.30mm - 50cm
0.25mm - 60cm
0.22mm - 70cm
Tippet to suit your casting ability.

This leader will lose more energy as you go from thick to thin (as the energy needs to travel further and further before reduction in diameter), meaning the fly will turn over with less and less energy and you will get a delicate presentation. Try cast this into a strong wind and you will battle.

2) Leader for casting into the wind:
0.37mm 100cm
0.32mm - 60cm
0.30mm - 40cm
0.25mm - 30cm
0.22mm - 15cm
Tippet to suit casting ability

This leader has more energy moved from piece to piece as the pieces get shorter and shorter, so the line speeds up as it gets closer to turning over the fly. This would help a lot in very windy conditions but if you cast this in a dead calm, it would be impossible to land a fly delicately on the surface.

Please don't use the above formulae - they are just illustrations out of my head and not actual tried and tested leader formulae - they just illustrate the point, which is that you cannot get everything you want out of a store bought tapered leader because it would be half way between these two examples, and good for neither application. I suppose you could use a tapered leader and change your tippet length, but to me sometimes you want a long tippet when casting into the wind.

I still fish religiously with the leaders in MC's article, mostly the two that he recommends, which are the Degressive Short (for windy days so my most used) and the Medium River for delicate presentations on calm days. With the understanding of the energy transfer i have been able to modify the degressive short formula by just cutting out the middle sections to allow a powerful leader to turn flies over in our very strong western cape winds.

Although i use those formulae because they work for me, the understanding on how to taper leaders as explained above should give you the know how to be able to taper a leader exactly how you would like it so that it suits your own casting style. The pascal cognard formulae are a good place to start though. If you find you are using a degressive short but you are slapping it down too hard, you can increase the length slightly in one of the pieces and try again. If that then collapses, then shorten it slightly, and you will eventually get to your ultimate leader setup for the different conditions.

Hope this helped and didn't confuse anyone. If anyone else has any more thoughts on leader dynamics, please share - these thoughts are just my understanding of how it works, which works for me and possibly not for others.

[Korrie]

Hi Grant
it is always interesting to read your posts.
Very well described.

[Korrie]

Grant
Your post took me back to Matric science: Kinetic energy, velocity, speed, momentum, mass etc.

[gkieser]

Grant
Your post took me back to Matric science: Kinetic energy, velocity, speed, momentum, mass etc.

Hehe - then i think i should probably apologise to you!

[KevinE]

Thanks Grant, that was very interesting. I may go back to experimenting with home tied leaders again. You can buy factory tapered leaders with similar charateristics to your degressive leader. The Umpqua ones that I use are called weight forward leaders and work well for casting into wind. But obviously you have more flexibility when tying your own.

[BuzzLiteBeer]

Thanx Grant. Your understanding is good enough for me so I will adopt it.
And boil it!!

[Rendier]

Cheers Grant. I still use the degressive medium leader when I fish streams - not that often anymore

[wernerm]

Thanks Grant, will try these formulas to see if the theory works in practice for me.

[shector]

Grant
Your post took me back to Matric science: Kinetic energy, velocity, speed, momentum, mass etc.

Hehehe, its exactly what it is Korrie.

[nicholas]

Great info Grant, question if i may.......why do they not make tapered leaders this way? secondly all those Knots!! does it not increase your chance of break offs and will it not cause Drag.....now i am assuming the answer to the last two questions is No because yourself and MC advocate these leaders and that in itself is validation enough for the set up,but i cannot help but ask.