AWAY / Translation - rotation

Walter & Group............

 

I will be away from my Group MailList Controller for a couple of days

Gordy

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From Walter Simberski :

Gordy - not sure if my previous email got through regarding translation and its contribution to the cast. I

received a notification that it had not been delivered yet.

 

One thing to consider is that it isn't just the tip speed that determines how fast the fly line gets moving.

The haul contributes directly to fly line speed without affecting the tip speed.

 

Another thing to consider is that if we have line looped over a pulley and then pull one end of the line there

is a direct one-to-one corresponding movement of the other end of the line, i.e. for every foot that I pull on my

end the other end moves one foot. If we fix one end of the line and move the pulley instead then the other

end of the line moves twice as far as the pulley.

 

Thanks

 

Walter

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Walter: 

 

True.  I was trying to keep it simple with some of the discussions by talking about casts with no haul.    Gordy

 

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From Sam Doyle:

 

I believe another good way to describe the comparison between translation and rotation is Joan Wulff's loading move and then power snap.  The loading move is the translation.  The power snap is the rotation.

 

Sam

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Sam......

 

We must be careful, here.  Remember, that maximum load is timed with maximum tip velocity produced by acceleration and that almost all acceleration of the rod tip occurs with rotation.  Almost all rod bend (loading) also occurs with rotation or an admixture of translation and rotation.

 

This means that the, "loading move" must be largely the result of rotation.  It can certainly begin, however, during either translation alone or with translation in combination with rotation.

 

There are those who take issue with Joan Wulff's concept of, LOADING MOVE and POWER SNAP as two diffenent, "moves".  Joan is the first to put that to bed as she describes the seamless entry of one into the other.

 

We can still reconcile her concept with the new things we've learned by studying casting mechanics with tools she didn't have when she wrote her books ....... no need to throw out her concept as, "old stuff".

 

I see her, "LOADING MOVE" as starting with translation, then smoothly flowing into a combination of translation and rotation, with rotation increasing the load.  This, in turn, seamlessly flows into pure rotation as the smooth, constant acceleration yields maximum rod bend (load) and tip speed as her, "POWER SNAP".

 

The hand movement rapidly decelerates (we call this the STOP) .  In the 0.1 sec between this interval and RSP (The momentary rod straight position) the rod tip is moving at its greatest velocity.   At RSP, the loop begins to form.   THE STROKE IS COMPLETE. 

 

Following this, the rod bends briefly in the opposite direction.  We call this, "COUNTERFLEX".  This is followed by brief bend in the opposite direction to counterflex.  We call this, "REBOUND".

 

IT IS DURING COUNTERFLEX AND REBOUND AND AN INTERVAL BEYOND THAT WE DRIFT.

 

Gordy

 

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From Steve Hollensed:-

 

 

 

Hi Gordy,

 

I find the discussion concerning the benefits of translatory movement in the casting stroke very interesting.

 

I have wondered if the physics concept of impulse applies to this. If we agree that a cast with translation (vs. all rotation) means that power is applied over a longer period of time, then I think it must.  What do you think? Only milliseconds might make a difference.

 

Impulse is simply the change in momentum. The general equation for impulse (change in momentum) is equal to the product of the force applied and the time the force is applied. So...apply a force over a small time period and you get a small change in momentum. Apply the same force over a longer period of time and you get a greater change in momentum. This is the concept that explains why follow through is important in golf, baseball, and even boxing.  For example, the longer the baseball is in contact with the bat, the greater the change in momentum. This essentially translates to the speed of the ball. (momentum = mass x velocity) 

 

Another interpretation of this is that you can get the same change in momentum by using a smaller force over a longer period of time. Is this why we say it is easier to cast a long line with a long stroke?

 

Just a question, but it is based on the assumption that casting strokes that have a high degree of translation will take more time through the casting stroke than those that are mostly rotational.

 

Steve  

 

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Steve...

 

YES ..... I do see the spreading of force over a longer interval as needed for the SMOOTH, CONSTANT ACCELERATION found with efficient casts.   I think that may well be another use for TRANSLATION .

 

You physicists do tell us that the word, IMPULSE means change in momentum ....... doesn't quantify the rate of change, however.

 

Unfortunately, in common, "speak", the word, IMPULSE implies something which happens suddenlly........ giving the impression of a jerking kind of movement.  Of course, that is just what we are trying to avoid with the smooth application of power needed for good casting.

 

Gordy

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I need to prepare for possible storms out in the Caribbean which may come this way.   Let's wind up the discussion for today with a comment fromm Lewis Hinks of Nova Scotia :

 

 

Whew!!!  I need these visual images to help me understand and will use those in my teaching. Thanks again.

 

Lewis

 

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