The point of tapers in fly lines and leaders

[Will]

OK, so I thought I had this sorted, but recent posts in other threads have me confused.

I’d always thought there were two main ways of looking at things taper-wise:

Roll casts/Speys: where thick line pulls lighter line off the water surface, so Spey oriented lines have back-weighted heads and long front tapers.

Presentation: where thinner line is subject to more air resistance and so slows down quicker than thick line (of the same density). This helps stop the fly line kicking, and with tapered leaders smooths the transition from fly line to fly.

But then Bruce said he’d thickened the tip of the MED to slow down turnover, citing increased mass...

And then James said that the taper in a bull-whip speeds up the tip...

Soooo...

How should I be thinking about this now?

Cheers

Will

[Paul Arden]

Hi Will,

The thinner line has less air resistance and actually wants to speed up. At first when the loop reaches the front taper it does sometimes accelerate. However it also has less mass.

I think Gordy would tell you that less mass means less momentum change at the loop front and therefore less force pulling the line. I think others might say that the mass to surface ratio of the thinner line means that drag forces have a greater effect on slowing the line. Maybe it’s a bit of both.

I would love to hear a clear explanation. In particular I would like to understand why a whip tapers to crack and a fly line tapers to dissipate energy.

Cheers, Paul

[Will]

Yep, I was/am(?) in the mass:surface area ratio camp. But Bruce’s comments have thrown me!

[Lasse Karlsson]

Didn't Bruce sat he lengthened the front taper to delay turnover but increased the mass to ensure it would?
Can't find the reply right now...

Cheers
Lasse

[Paul Arden]

I think that Bruce is comparing to a line that has a head a) not compound front and b) has heavier line behind the compound front, which it would if they both weigh the same at 30’. I think b) is rather important.

I’m in both camps, Will. I don’t think one excludes the other.

Cheers, Paul

[gordonjudd]

I think Gordy would tell you that less mass means less momentum change at the loop front and therefore less force pulling the line

Paul,
I am not the one who came up with that explanation. Rather it is the viewpoint of researchers such as Lingard, Spolek, and Gatti-Bono who have written papers on the subject.

The effects of the tradeoff between the positive acceleration acceleration force on the line produced by the tension at the top of the loop and the negative acceleration due to drag forces on the line and fly were discussed on the old board at:http://sexyloops.co.uk/archivedboard/vi ... 24&t=12479

Thanks to you for getting that valuable resource restored.

I would love to hear a clear explanation. In particular I would like to understand why a whip tapers to crack and a fly line tapers to dissipate energy.

The slowdown of the line due to increased energy dissipation is a red herring concept.

Both the drag losses and the positive acceleration due to the momentum change of the mass going around the loop depend on the square of the velocity so an increase in the velocity is not going to favor one over the other.

It should be noted that the properties of the tear shaped loop that is propagating down a tapered whip is different than the u-shaped loop that is propagating down a fly line. Thus the effects of taper on a whip are much different than the effects of taper on a fly line.

Gordy

[Geenomad]

Maybe it's just me, though I doubt it, but I am wondering why this stuff about angular momentum has been granted asylum in this part of the Board. What has it got to do with Fly Casting, as in how to do it, better?

Cheers
Mark

[Graeme H]

Other thread Mark? But yeah, I agree, the original poster should have put the angular momentum thread in TechAnal.

[Graeme H]

A taper can magnify velocity in a fly line and a whip via the same principle shown in this video. Momentum from a heavy object is transferred into a lighter one, which is then transferred into an even lighter one. To maintain momentum, the velocity increases.

For the mechanism of how the energy can be dissipated through a taper, I'll need to explain that with a tracked video tonight. I'll do that in the angular momentum thread and put a link below later.

Cheers,
Graeme

[Geenomad]

Other thread Mark? But yeah, I agree, the original poster should have put the angular momentum thread in TechAnal.

Yeah I thought about that. But it's both threads really. Same creep into same subject matter and my objection goes well beyond forum taxonomy but will leave it at that. Rant mode cancelled.

Cheers
Mark