Zero-off A1-C3 settings, for what rope length is it calibrated?

[JJVDMZN]

Let me elaborate on the above question.

 

When you map a course with ZO, it maps the course in relation to the boat position and not the skier's position.

So this is why I'm asking this question.

The distance between buoys being 41m means that somewhere in the 1st 13.667m setting C pulls, the 2nd 13.667m, B and the last 13.667m setting A

 

Skiing at 15off the skier is 18.25m from the boat, and at 43off, 9.75m from the boat which means that the A, B & C settings pulls the 15off skier 8.5m earlier in the course than the 43off skier, that's more than 1/2 way into the previous setting, meaning that settings A becomes B, B becomes C and C becomes A at 15off if you compare it to 43off.

 

As you shorten the rope you get pulled that shortened distance later in the course.

 

ZO would be more consistent (accurate) if the skiers rope length was also entered, obviously this would have to be done after every pass as the skiers shortens.

 

@Horton please move the post to the correct Category if needed

 

Regards,

 

JJ

 

[LeonL]

I believe that you have a basic misunderstanding of how ZO works. No disrespect intended. The boat only responds to what the skier does and when he does it. Then and only then do the settings come into play. If I misunderstood what you wrote it's because my mind works simply.

[MISkier]

ZO does not apply any throttle in anticipation of where the skier is. It only reacts to what the skier does. It responds to the skier's pull whenever they pull. The boat's location in the course is not considered in any way other than the operation of the virtual timing.

 

Rope length is not a variable that requires any adjustment for ZO.

[Than_Bogan]

Not quite on topic, but I believe it could give a better pull (for some definition of "better") if it did do some degree of anticipation. Milliseconds are long for a computer, so if it guesses wrong it will know soon enough and can further correct. But I think waiting for load is not the ideal way to drive.

[MISkier]

@Than_Bogan, I would prefer if ZO did not accelerate and pull the handle away from me before I am ready.

[dchristman]

Predictive!? You want the speed control to have a camera and watch your body position?

 

Say.... I have an idea. How about a person controls the throttle? ;)

[Than_Bogan]

@MISkier Perhaps that was partly tongue-in-cheek, but my proposal does not imply that. There is a delicate balance of doing something too soon and too late. And remember that every action or inaction has consequences later because it has to get the right time on each segment.

 

Control systems are effing complicated. But ignoring information is rarely a good idea in designing one.

[MISkier]

@Than_Bogan, now that I think about it, some sort of "slack sensor" might be helpful. If I get too much slack, ZO could "see" it and magically take just enough away to help me out without ripping the handle away.

[JJVDMZN]

This is what I experienced with my boat, the ZO course calibration was out by more than a boat length, this would cause the ZO to beep before the boat passed the buoys in one direction and after the buoys in the other.

 

I had three skiers that regularly ski behind my boat complain that the boat felt different going through the course, especially in the one direction (pulling them too early).

 

So my thinking was, ZO does wait for pull on the boat, but then reacts to that pull according to the GPS position of the boat in relation to the buoys.

I remapped the course and they were happy.

[MISkier]

@JJVDMZN , your issue was likely that ZO was reacting differently to maintain proper virtual buoy-to-buoy timing, It probably thought it had less (or more, depending on direction) time to react to a pull to return the boat speed to within tolerance. The fact that the virtual timing did not align with the actual course was what your skiers felt.

[JJVDMZN]

@MISkier, yes that virtual timing's pull between buoys get determined by settings A1-C3, if you have a longer rope the boat will pull you at a different place / position in the course than a short rope.

The boat has to pass the 6 buoys in a certain time, so it must pull the skier 6 times at 6 GPS points (different GPS points for A, B & C) in the course to catch up.

 

Do the experiment, map the course 4m early at entry as well as exit, this will give you a 8m variance in the course in the 2 directions, effectively changing your rope length by 8m in the two directions as well as GPS points for settings A, B & C. If you feel a difference in the two directions, then my theory of ZO reacting to GPS points, to catch up your pull, are correct

[MISkier]

The issue was not GPS position, but how much time ZO thought it had to be able to correct the boat to return it to tolerance before the next timing segment. Your mapping error had you effectively skiing the wrong path and pulling on ZO at places in the course where it thought it had different amounts of time to correct the speed to get good times. You'd get the same feel if your mapping was good, but you instead skied and turned a few meters before or after the actual buoys. ZO would think, rightfully so, that you were pulling in the wrong places and alter its response to maintain a the correct virtual timing. The feel of those altered responses would not be what you would normally expect.

[Gloersen]

will gladly stand corrected, however once ZO enters the gates of a "mapped" course it's corrections are solely and purely speed (accelerometer) based. Other than a set point above baseline speed prior to the gates there aren't any position (location) based adjustments.

 

The virtual ABT is just for scoring purposes.

[JJVDMZN]

@MISkier, would it be correct to say that if I'm wide and early at the buoy, I would get the same pull / feel as when I'm narrow and late (especially in setting C as it reacts the earliest)?

[Than_Bogan]

@JJVDMZN Not quite sure what you mean by "same" in this context, but since the control system is almost entirely reactive, it certainly wouldn't be exactly the same speed at every position in the course across different behavior by the skier.

[ForrestGump]

Part of the sensation you feel is in relation to the gate. According to what Andy said a few years back, ZO does a gate ramp(which is position based) in addition to the skier ramp, which is load based. So if you start the gate ramp late or early, ZO will gas out of sync to get an imaginary split and end course time, because the skier is essentially pulling it down in a spot that won't allow it get the next split correctly. My personal thought is it feels harder on the late side(when the course is mapping is off). Sometimes on close lakes you'll find ZO has autoswitched to the wrong lake and it'll feel hard. Regardless the skier ramp is load based and has nothing to do with where they pull. Only when they initiate the load that pulls down the boat.

[MISkier]

@JJVDMZN , I would think the load after your turn might differ between the wide/early and narrow/late. This might affect the amount of speed loss you create for the boat and how much ZO thinks it will need to compensate. This is why you hear people saying to "hide from ZO". The ZO reaction will be engaged with the same delay and with the same relative throttle application curve, but the quantity of throttle dispersed over that curve may differ to respond to the speed loss created by your load.

[liquid d]

haha too friggin funny! dchristman hit it right on the head! Give me Gordon, Tommyrama, Rocky, Les, Jeff G, Becky , Will B or Lyman, or Hambone, with the throttle in their hand ANY DAY!

I'm sure I left out some great ones...but's it's still early!

[Bruce_Butterfield]

I really hate to agree with liquid d, but every once in a while he's right!

 

But the downside to going back to manual drivers is waterskiing would never get into the olympics.

 

{yes that is sarcastic}

[DaveD]

Anyone that thinks manual drivers are better never skied with one of my brothers driving. :smile:

[BRY]

Ha! You guys are funny. There are a handful of drivers that may, just may, be able to be as consistent as PP and ZO. Put my doubts in about ZO though. Even if so there are very, very few skiers who have access to hand drivers like that in tournaments, much less in practice. Definitely not enough that good to cover the tournaments nationwide, much less internationally. I like that I can go to my dock, set the ZO up in my 200 and get what feels like the same ride I get in tournaments. For a tourney in Fl, CA and France on the same day the course is the same size, the ropes the same length and the speeds are the same. So directly comparable scores, as even as it can be with technology we have. And the avg skier can train that.

[JJVDMZN]

Thanks for the feedback.