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  #11  
Old 01-25-2011
CoachBillL CoachBillL is offline
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Default Diagram please!

I must agree with haschu33: the force of this analogy escapes me completely. For one thing, a propeller blade has to be shaped just so to work at all, does it not, and not at all like a human arm? And are not the propeller and the arm moving in completely different ways? If someone who gets it can show how it works in a drawing, that might be very helpful.
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  #12  
Old 01-25-2011
Lawrence Lawrence is offline
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Quote:
Originally Posted by terry View Post
The optimal way to maximize propulsion while minimizing work is
Enter through the Mail Slot, then
Extend at shallower angle.
I think that is a pretty important post.

I don't think I've seen the above stated previously as official TI method, although I think it answers many of the questions on this thread and certainly confirms a view I arrived at myself after trying and failing to swim with a 'steep and deep' entry.

As to the propellor analogy, I think the point is that by entering steeply but then flattening the arm as it extends forward, the trajectory of the arm is a curve, the convex side of which faces the pool bottom. As the arm travels along this curve, the water beneath is pushed backwards, rather like the way the curved face of a propellor blade pushes water away from itself as it moves.
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  #13  
Old 01-25-2011
jcphil jcphil is offline
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Default Thought on backward displacement during spearing

It seems to me that as you spear towards the initial target, there wouldn't be much rearward water displacement because a soft wrist would have the fingers lower than the hand. If, however, you want the spear to flatten out after initial entry, you would do it by raising the fingers. This action would put the hand in a position where it would cut through the water at an angle that would generate a force down and to the rear in order to move the hand up and forward.
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  #14  
Old 01-25-2011
terry terry is offline
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In the end, it's interesting to present and ponder various scenarios. Analogies only improve your grasp on a concept, not on the water. Their value is in reinforcing your conviction that a particular technique is better than its alternative -- and your resistance to being led down a primrose path.

If one doesn't do that for you, come up with another.
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  #15  
Old 01-25-2011
terry terry is offline
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Quote:
Originally Posted by kueli View Post
And now it is 16:56 and sunny in Madrid. And I am off to the pool. To chase my Chesire cat ---that misteriously subtle and ellusive perfect angle...
This would be a good time to be in Madrid. At 16:56 this afternoon in New Paltz it will be nearing dark. However I swam 11:40-12:40 and had a wonderful practice. It's not sunny today. We had snow last night and this morning and the sky still looks as if we could get more. Tomorrow will be an x-c ski day.
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  #16  
Old 01-25-2011
terry terry is offline
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Quote:
Originally Posted by CoachBillL View Post
For one thing, a propeller blade has to be shaped just so to work at all, does it not, and not at all like a human arm? And are not the propeller and the arm moving in completely different ways?
Is not the forearm shaped - to a modest degree - like an airfoil, rounded on the leading edge, which presses the water back, and flatter on the trailing edge?

And I do think its indisputable that the arm does displace water backward - as well as in other directions - as it enters. The water that was occupying the space your arm enters through has to move somewhere. If the arm enters steeply more of that water will be displaced toward the rear.
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  #17  
Old 01-25-2011
terry terry is offline
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Quote:
Originally Posted by Lawrence View Post
as it extends forward, the trajectory of the arm is a curve
Well put. I frequently describe the arm's path from entry to target as a gentle arc.
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  #18  
Old 01-25-2011
Janos Janos is offline
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Hi all,

Perhaps the engineer had in mind an analogy that featured the driveshaft acting in concert with the propellor blades. Whereby, the shaft is the core of the body (including the extended leading arm), and the catch arm is the propellor blade. Admittedly, in my analogy, the blade would be two thirds along the shaft, if one was to be pedantic. Which of course we are not on this forum. :-)
I could of omitted the leading arm, but that is my main point in posting this. The recovery to leading arm movement, is to me, once balance has been mastered, one of the most crucial aspects of TI. It has been mentioned before that recovery arm movement can aid propulsion, but in my experience, I don't think it can, if one wants to swim in a 'pure' TI way. What it can do, is hinder any chances of the swimmer becoming 'fishlike'.
Whatever way the arm enters the water, if it causes drag, you will be slowing down. The arm must enter and extend, without causing loss of propulsion, before hip drive, to achieve the optimum position for the hip drive. Perhaps this is where the swing analogy fits in. In this position your leading arm will be partially extended, and your catch arm will be primed (front quadrant position).
If your recovery arm enters too close to your head, or is too wide on entry, or
disturbs the water too much, the loss of momentum will lower your stroke count and will continue to do so until you recover gently, and place the hand in the water, slide it smoothly forward, and then apply the power. Shinji does it correctly. He takes his arm out of the water, his elbow is steep, but his forearm isn't, and after high elbow recovery,extends shallow entry forearm into the water using shoulder, and then drives with the hip. I think it is also very important to recover with the high elbow as far as it will go, and then articulate the forearm into its most efficient entry position, and in doing so, whilst moving all the time, try to recover over as long a distance as you can, when trying to reduce stroke count. Incidentally, I believe the smoothest stroke can be achieved by kicking after the hip drive has engaged,and not using the kick as a precursor.

Kind regards

Janos
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  #19  
Old 01-25-2011
CoachBrian CoachBrian is offline
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Terry,

I think I understand the propeller analogy. However, when I swam last night, I did not feel it. As haschu33 said, if my arm entry is acting like a propeller pushing water backwards, I should have a feeling of pressure on the downward/backward facing part of my arm.

I swam looking for that sensation, experimenting with different spearing angles,arcs, and pulling efforts, but I only felt water pressure on the front of my arm.

Perhaps there is a bit of fluid dynamics that is currently beyond my comprehension?
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  #20  
Old 01-25-2011
haschu33 haschu33 is offline
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Quote:
Originally Posted by terry View Post
In the end, it's interesting to present and ponder various scenarios. Analogies only improve your grasp on a concept, not on the water. Their value is in reinforcing your conviction that a particular technique is better than its alternative -- and your resistance to being led down a primrose path.

If one doesn't do that for you, come up with another.
Well put!

Haven't got a another one.
Conviction is good, path also. So, no need to worry...
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