Tension, Cont'd

There has actually been quite a lot of work done around these topics 'with regard to physical determination' as you put it. With regard to "to measure is to know' I couldn't agree more. However the challenge is that the physics and mathematical formulas that outline these principles are exceedingly complex - far too complex for this kid anyhow. Happy to post some links if you are desirous ...and want to be sent to sleep.

Some of the most recent, revealing and interesting work has been performed by Grunde Løvoll of Norway (unfortunately his paper is in Norwegian)

There's also an excellent theses by Mike Hendry’, “Measurement and Simulation of Fly Casting Dynamics”, from the University of California Davis in 1999. Wich I've only read bits of.

Of course the man to ask to talk to is our own Bruce Richards (and Noel of course) - what Bruce doesn't know on the subject probably isn't worth knowing.

Anyway. Tension is present throughout the system and must be in order for a loop to form and propagate forward. My current and somewhat limited understanding is: The tension in the line at the top and bottom of the loop is related to the centripetal force (http://en.wikipedia.org/wiki/Centripetal_force) required to balance the v.^2/r ( keplers 3rd law)

http://www.phy6.org/stargaze/Skepl3rd.htm) forces of the mass in the line that that is traveling around the loop and frictional drag losses. But I'm not an engineer and could be way out here.

Earlier I stated that I believed tension in top and bottom legs would be the same - I now see that this is incorrect - as there will be frictional loses as the line passes around the loop face as it propagates forward.

However, You are not simply "throwing a mass of line" as Michael states. The simplest way to demonstrate this that I know off is to perform either one of the following simple experiments. A good one for students too

Take 90 ft of fly line - bunch it up and try to throw it 30 meters. How far will it go? - Line mass remains the same as in when it is cast.

Alternately, take 90ft (or whatever) of fly line. Lay it out on the grass behind you then try to pull and throw it forward in javelin fashion. How far does it go. Again mass is the same.

As pertains to this particular discussion - A big part of the magic that allows us to create a loop and thus cast a flyline, is the tension present in the system; primarily present due to the fact that out line is tethered - even when shooting. Of course there are many more magical properties that allow this to happen - but your topic is currently tension :-)

Well.... if I have that 90' of line straight out on the grass behind me, I can easily throw the whole thing....IF I DO IT WITH A FLY ROD. To do it in javelin-throw fashion using my hand/arm is impossible. REASON: I can only get my hand holding the line to move at a maximum of 2-3 M/sec.,(Average throuhout my hand stroke only about 1M/sec) so the velocity of the line is no greater even though the mas has not changed. Using a 9' fly rod, I can generate a tip and therefore a line velocity several times greater because of the lever effect of the long rod. With lack of velocity and the mass remaining unchanged, I cannot get enough tension to yield sufficient momentum.

If the line is bunched up, then even using the fly rod, I cannot throw it very far : REASON: Almost all my effort will go into straightening out all that slack lying on the ground and very little if any energy will be left to throw the line. You are correct in that the mass is unchanged except that the mass of any amount of line left unmoved on the ground as I take up slack would have to be subtracted. Again, with all that slack, I'll never get enough tension to impart my energy to the fly line.

Jason Borger has worked with Grunde Lovol of Norway .... he has sent us one of his papers translated into English. A few months ago, I included it in one of our attachments. I'm aware of Gordy Judd's work. Seems he's been trying to disprove some of the conclusions derived from work with the Casting Analyzer.

Bruce....

A couple of questions have come up during the deliberations of our Master Study Group. Wonder if you could help :-

1.) Do you think that the TENSIONS in the upper (fly) leg and the lower (rod) leg remain equal as the loop unfurls ?

2.) Has this actually been measured ?

3.) Is it the momentum of the unrolling / traveling LOOP or that of the lower (rod) leg which is responsible for, "pulling" the fly line out of the rod guides and tip top when shooting line ?

4.) Can you give us the specific reference to Mike Hendry's, "Measurement And Simulation of Fly Casting Dynamics". (We're told the work was done at the U. of Cal., '99.)

Gordy