Leader limpness

[Lou Bruno]

I'm reading up on leaders. Does the leader material diameter change with its limpness (hardness?) So, the harder the material, the smaller it's diameter. Is material limpness related to material hardness.
Any relationship to limpness with mass?

Lou

[Paul Arden]

Hi Lou,

Hardness/limpness can be independent of diameter. That bit I do know!

Cheers, Paul

[Graeme H]

I'm not a proper expert on these things but as far as I know (based on what I know about physics), the mass is of higher consideration that stiffness, but there should not be any sudden changes in stiffness within the system. By that I mean the butt section of the leader should be of similar stiffness to the thinnest part of the line and there should not be an impediment to bending.

It seems I can get by with limp leader materials as long as the taper of the mass is consistent. When I'm making leaders, I don't want the material to get stiffer than any section above it, but I haven't experimented enough to give you better answer.

Cheers,
Graeme

[Paul Arden]

I have some very stiff tippet materiel that I was given to test. It's 40lb Hatch Flouro. I've found that the stiffness is a problem. Apart from the difficulty it presents when tightening knots, it causes the loop to open unexpectedly as the leader turns over. (I would not normally use Flouro incidentally).

Cheers, Paul

[Lou Bruno]

Paul

So, would a harder material create more mass, therefore, we should use a smaller diameter?

BTW, I'm not a fan of flurocarbon.
Cheers
Lou

[gordonjudd]

Hardness/limpness can be independent of diameter. That bit I do know!

Paul,
I don't know how hardness would enter the picture, but if you are saying limpness is related to the bending stiffness of a leader section then as noted in Wikipedia:

The bending stiffness ( K ) is the resistance of a member against bending deformation. It is a function of elastic modulus (E), the area moment of inertia (I) of the beam cross-section about the axis of interest, length of the beam and beam boundary condition.I

The area moment varies as dia.^4 so that will be the dominate factor in determining the bending stiffness of a given length of leader material. As Graig Spolek noted in his article on leader stiffness:

Increasing the inherent stiffness of the material by 10% increases the leader stiffness by 10%. Increasing the diameter by 10% increases the leader stiffness by 46%!

Dr. Spolek measured the Young's modulus of different leader materials and found that the nominal modulus of nylon leaders is around 300,000 psi (2 GPa) as shown in his graph below:
http://imageshack.com/a/img922/462/J2LdiV.jpg

Gordy

[crunch]

Paul

So, would a harder material create more mass, therefore, we should use a smaller diameter?

BTW, I'm not a fan of flurocarbon.
Cheers
Lou

Solid Nylon line density is somewhere 1.05...1.10. Fluorocarbon has higher density. I have read densities 1.7 to 1.9 but fluorocarbon line is a polymer which has other ingredients which lowers the density to about 1.5

Esa

[Lou Bruno]

Gordy

As you posted...Increasing the diameter by 10% increases the leader stiffness by 46%.

Didn't realize that, any chance making the article available?

Would you know of there being a relationship of leader stiffness and leader hardness?


Being that the mass profile of a leader is considered the most important factor in leader turnover, any increase in diameter increases it's mass...direct relationship?

Lou

[Lou Bruno]

Gordy

Thinking about this some more. It's the leaders mass PROFILE, not only the leaders mass that is important in leader turnover.

Esa reminded us that flurocarbon is more dense then nylon. I'm assuming the denser an object the harder and stiffer...to many assumptions perhaps.

Lou

[Graeme H]

I was thinking a bit more on this overnight.

If we took it to the extreme and had a rigid rod of minimal mass within the leader, it would cast terribly. So I have to revise my original thoughts and say stiffness is important. Too stiff is a problem.

I haven't found a material that has the required mass and is too limp to work though.

Cheers,
Graeme