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A wacky theory about A/B/C


Than_Bogan
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Since I optimize parameters for a living (I specialize in making computer code run faster), it's probably no surprise that I'm a bit obsessed with this whole ZO parameter thing.

Today I had a thought that I found interesting, and figured I'd share it on the off chance that somebody else found it interesting.  It has to do with how A/B/C relates to line length.  As far as I know, this has nothing to do with 1/2/3, but perhaps someone will see some connection there.

(Before reading this, be sure to read the ABC/123 thread and see scoke and clemsondave's charts about what these parameters mean.  Otherwise you'll be pretty confused.)

The physics of slalom skiing dictate that, as the rope gets shorter, the skier's speed across the wakes increases.  Since the geometry of the course hasn't changed, a skier covering the same distance at a faster speed does so in less time -- i.e. the duration of the pull is shorter.

This then means that ZO has less time to work with during the pull phase.

If I can assume that the delay in correction that comes with B and A are constants, this then means that the correction is happening closer and closer to the next buoy as the rope gets shorter.

And so that leads me to theorize that the letter that allows the best performance may be closely related to line length.  At a long line, things are happening slower, both entering the pull (where a little delay might be beneficial to get body position set) and in the duration of the pull (so that a setting with a delay will still have enough time to get the job done).  Thus A might have some advantages for a longer line (although the meaning of "long" is contextual and can only be figured out from experience).

But as the line gets shorter, a delay in correction eventually may mean the boat is adding RPM as you are trying to release, resulting in that "pulled into the ball" feeling that is totally awful.  And so B might become preferable as things got shorter, and then finally C when even shorter than that.

Has anyone had any experiences that might help confirm or deny this theory, or set some initial guidelines on which rope lengths are likely to go well with each setting?

I'll start:  I've noticed that many of the best skiers I know use C, while less advanced skiers often prefer A or B.  So that fits with my theory.

For me personally, I've found B1 feels clearly the best for me at -28 and -32, but I'm starting to question if I'm getting picked up too late out of the turn at -35 and -38, and am considering that C may be better to maximize my performance (since presumably I can manage to run my easier passes on any setting with a bit of practice).

So, mostly out of my ass, my first draft would be that A is best through -22, B is best for -28 and -32, and C is best therafter.

I reserve the right to decide that the above is complete nonsense after further input...

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I would expect the underlying reason that you see more skiers using A, at longer lines, is all about precision. A skier that hooks up early, or never gets free of the boat would earn a small buffer of forgiveness to get properly set if there is a little more time before the boat adds rpm.

 

It's not crazy at all, especially if it works for you. You are well within your rights as a skier to ask for a different setting every pass. 

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HO410: "I would expect the underlying reason that you see more skiers using A, at longer lines, is all about precision. A skier that hooks up early, or never gets free of the boat would earn a small buffer of forgiveness to get properly set if there is a little more time before the boat adds rpm."

I'm pretty sure that's true, but I think it's still consistent with my theory.  Any optimization is always about tradeoffs.  The advantage of A is that it's foregiving at the start of the pull phase.  THAT part seems like a plus for any skier.  The disadvantage of A is that it's going to be fighting you *later* in your pull.  For a skier on a longer line, that disadvantage is almost irrelevant, so why not take the advantage?

For a skier on a shorter line length, that disadvantage is starting to get more severe, and the advantage of being more foregiving at the start of the pull phase is simultaneously becoming less important.

To be clear, I'm not saying line length is the only factor in choosing A/B/C.  The idea I'm getting at here (which I repeat may be completely wrong) is that any given skier may want to move further down the alphabet as the line gets shorter.

I'm not thinking I'd ever change settings from pass to pass -- that seems a huge overkill given that the setting should be less important on easier passes anyhow.  But I am thinking two things:

1) This could mean that choosing a setting based on how your early passes feel might be a mistake.

2) This could be a tolerable starting point for picking a letter for someone new to ZO.

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Chef - yeah, ironically what I also want to do is never have to pick any parameters and just ski.

In fact, one of my main interests in this is a vague hope that overtime we and ZO can understand *WHY* these parameters *seem* to be necessary, and then figure out how to improve the speed control algorithm so that they are no longer necessary.  It's not as if human drivers had tunable parameters...

That said, since I know you in real life, I can say that you fit right into all of my theories about ZO settings.  I believe that 1 is generally advantageous unless the skier can pull the boat off enough to seriously lose acceleration.  So at your size [which you've revealed repeatedly on this forum, so no harm there], I'd expect 2 to be the best choice.

And when you were maxing out with a few balls at -28, my new theory from today would have suggested A.  So there you are: A2.

As you start getting though -28 a lot and aiming to run -32 in a tournament, it's a possibility you may find B to give you a better chance??

I'll be sure to keep you abreast of my experiments around going down the alphabet to try to make -35 and -38 easier.  That may be informative.

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Thanimal - I think I made this point in one of my posts - "how ZO affects the skier is dependent upon line length" or something close to that.  I've believed this for some time.  No one I'm aware of takes advantage of the rule that allows the skier to change the setting before each pass.  When working on a shorter line, I drop from B2 to A3 - this allows me to get into position before the boat picks me up.  But in tournaments, I've been playing with going to C2 at 35 or 38 - I seem to get better spacing before the buoy.  This is really no different than fin set up.  If my ski feels great at 28 it will probably suck at 38 and vice versa.
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I will talk to some folks this week about this. I know some people that are shorter line skiers than I am skied A2 last year and moved to C2 this year. My big issue is obviously lack of practice time behind a boat with ZO to figure out what the right setup is for me as I improve.

 

And don't worry about the reference to my size. I am trying to change it but am not there yet.

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Let me throw something else into the mix. Your choice of letter is also dependant on how you set the fin up. BAM!

I pulled Arora on C1 instead of A2 without him knowing it. He ran right up through 38 and liked it, but felt that the ski died a bit much and turned in too soon. So he's running B2 right now, as opposed to A2, where he'd been at.  I'm convinced with a little work on the fin, C1 or C2 is where he should be. 

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I went the opposite way, at the suggestion of someone in the boat. I've spent significant time at C3, then C2, then I've been at B2 for about 3 months, then switched to A2 2 sets ago which feels pretty good right now. I don't know how much water temp plays into it (our water is around 95 right now) One of these days I'll spend a bunch of time running 32s and try them all....I just don't know when.

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