Damping / Casting mechanics

Hi Gordy,

I liked the message from Bill Keister because it comes close to what I think the casting stroke is - work done to cast the line. As I understand it, Bill?s definition is: Stroke starting when the rod makes the first movement in the direction of the cast. The stroke ends when the rod reaches RSP in the direction of the cast. This means that the stroke encompasses creep (a fault), translation and rotation which are both means of applying force to the fly line.

Here are some similar ways (3) to look at this:

Casting Stroke:

1 - Commences when line tension near to the rod tip increases in order to make a cast. Completes when line tension near to the rod tip in the direction of the cast becomes practically zero.

Stroke can also be expressed in terms of force or velocity as they are proportional if the line mass is considered constant.

2 - Commences when force applied to the line near to the rod tip increases in order to make a cast. Completes when force applied by the rod tip to the line in the direction of the cast becomes practically zero.

3 - Commences when line velocity increases in order to make a cast. Completes when line velocity is greater than rod tip velocity in the direction of the cast.

The ?direction of the cast? is that represented by the line?s inertia.

All of these are intended to represent the same thing. From the instant that the rod does work on the line until the instant that it ceases to do work on the line to make a cast is the casting stroke. What any of the parts are called (rotation, translation, creep etc) and whether the ?stop? (if there happens to be a stop) is part the cast (sometimes yes and sometimes the line is launched and gone before the rod stops) matters not, only forces that contribute to the cast are part of the cast. Much has been said of the increasing speed of the rod tip as it unloads. This is exactly what might be expected when the line has launched and is travelling in a different direction to the rod tip allowing the tip to unload and increase its speed, counter-flex etc with little influence from the freely flying line until tension is established in approximately the opposite direction to the travelling line.

Comments welcome!

Best regards,

Ally Gowans

See my web sites http://www.letsflyfish.com and http://www.flyfish-scotland.com

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Gordy,

You and Soon captured the essence of this topic. Your renditions below hit home for me!!!

Basic essential that initiates the foundation for the cause, with the effect of the variables that could influence!

Well done!

All the best

Gary Davison

Gulf Coast Spey

Gulf Coast School of Fly Casting

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From Juergen Friesenahn :

Hi Gordy,

I agree with Bruces statement, that a rollcast needs more power, than a OH-cast of the same length.

Less mass and linestick has to be compensated.

But IMHO:

- the stroke after D-loop formation/at Keyposition is the same.

- the rollcast after D-loop formation/at Keyposition follows the same rules as the OH-Cast

- And of course, you can overpower a rollcast, causing a concave tippath resulting in a tail, when arc is too small.

Photo: Me in a practice session, overpowering a rollcast with a quite soft speyrod and a 65ft head.

Clearly seen the dip in the tippath and the too high rodstop for this path causes a tail.

- But this only happens, when you accelerate the rod nearly in the vertical plane.

U usually cast roll/spey slightly off-vertical, so the vertical-dipping element in the cast decreases, as more you go off.

But this cast was done nearly vertical, and so this component becomes very prominent.

If I would have gone a bit off-vertival, the cast could have functioned (not pretty, but no tangles...)

Best

Juergen

P.S.: will meet Bruce in 2 weeks at EWF in germany.

Looking forward to this.

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Juergen...

I placed your picture in an attachment.

We must also remember that when casting in an off vertical plane, gravity on the loop plays a different roll and may help prevent the actual tail..... or at least the collision.

Gordy

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From Jim Laing :

Gordy,

I have archived Soon Lee's comments on loop size and straight line path.

When looking at Grunde's drawing of the actual casting study, it appears that movement of the rod after RSP is critical to loop size, or is it?

On longer casts, with higher linespeed, that brief moment between maximum load (initial stop) and rod-straight-position is what I think is most critical to the cast, and also determines loop size (not initially - but later as the loop is unrolling). When I slow it down and use less line, I see it differently...

I have attached a drawing and seek response on the importance and impact of tip path immediately after RSP through max counterflex regarding loop size and parallel legs. After Studying Grundy's drawing and reading Soon Lee's comments, I thinking max counterflex is significant and has impact, especially on slower casts...

Jim

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Jim... I placed your drawing in the second attachment.

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