ZO - New Words & the Missing Variable...

[ToddL]

I recently re-reviewed the ZO setting descriptions from the ZO manual. This got me to thinking that we haven't been interpreting those words correctly. Here is my take on what ZO published.

 

From page 35 of Zero Off – RevQ User Manual:

A – Slower engine response out of the buoy, but the boat will tend to move ahead as the skier approaches the buoy.

B - Moderate engine response compared to A and C.

C – Faster engine response out of the buoy, but the boat will tend to hold back as the skier approaches the buoy.

1 – Requires the lowest amount of load before the system initiates an rpm spread. This provides for a softer pull behind the boat.

2 – Provides for a moderate pull behind the boat as compared to 1 and 3.

3 – Requires the highest amount of load before the system initiates an rpm spread.

 

There is no load variable in ZO (no force switch on the rope). Thus, "load" is simply a convenient term to describe the amount of speed reduction created by the skiers' force against the boat.

 

We can restate this as:

A = throttle response is delayed the most once the load trigger is met (feels like the slowest ramp up*)

B = throttle response is delayed a little once the load trigger is met (feels like a moderate ramp up)

C = throttle response is not delayed once the load trigger is met (feels like an extreme ramp up)

 

1 = speed reduction trigger threshold is easily met with the least amount of force from the skier (doesn't let you pull the boat speed down far)

2 = speed reduction trigger threshold is met with moderate force from the skier (moderate ability to pull the boat speed down)

3 = speed reduction trigger threshold requires the most amount of force from the skier (let's you pull the boat speed down the most)

 

Thus, the extremes of these settings are:

A3 = requires more speed reduction before triggering, so late trigger (3); and the corrective response is delayed (A) = This skier has time to pull the boat down a lot and the boat has to recover a lot and it gets a late start in doing so. The consequence of this is that the corrective throttle response may feel soft, giving the skier time to get into a good leaning position; however, the corrective throttle will likely still be occurring into the next buoy.

 

C1 = easy to trigger, so early trigger (1); and quick, immediate response © = This skier doesn't get to pull the boat down as much and the boat starts to recover almost immediately. The boat is completely back up to speed the earliest. The consequence of this is that the corrective throttle response may feel hard, and the skier must be ready immediately for the "hit"; however, the corrective throttle response will be complete earlier, probably well before heading into the next buoy.

 

[Note: One would have intuitively assumed that A1 was at one end of the extreme and C3 was at the other. This is not the case. (I wish ZO had reversed the letters. Rumor has it, they realized this reversed polarity, but thought that switching it would create more confusion than leaving it as is...)]

 

If there is no skier behind the boat, all ZO settings will pull the same way. Meaning... the missing variable in many of these explanations of ZO settings is the timing and amount of lost speed due to the skier's force.

 

The amount of load generated by the skier will cause these extremes to feel very different from one another. Thus, the heavier skier with a slam-dunk style will cause the greatest perceivable variation between these two extreme settings. The lightest, smoothest possible skier will make the settings less perceivably relevant.

 

If you create extreme force against the boat, then the boat must take equal corrective action to recover. The settings allow the high-force skiers to balance the nature of that recovery with what feels best to them. Thus, the less you "hit" ZO the less ZO has to "hit" you. However, if you must occasionally hit hard, you want your ZO setting to result in timing that matches your style..

 

* Ramp up - I have seen some charts which depict the throttle as a progressive increase at different rates. I think this is not the case. Consider this fact. If ZO were to instantly jump the RPMs by a set amount, the feeling on the handle would not be instantaneous. The ZO manual says nothing about different throttle response curves. However, if the throttle reaction in ZO is "on/off", it will feel like a curve. The boat is already moving, and in instant change in throttle will not be felt as an instant change in speed. There is a lag for the mass of the boat to respond to the change in the thrust from the prop against the fluid nature of the water.

 

But I do not think it matters. The key concept is that the area of the curve must equal the amount of speed lost due to skier force.

 

If the system responds more significantly (more significant throttle increase) then the necessary duration will be shorter.

If the system responds with a shorter duration, then the throttle increase must be more significant.

Thus, whether we draw the pictures with rounded corners or square ones, the primary concept of the area under the curve should be exhibited consistently.

 

Most charts only show only half of the total equation - the boat's response. We should consider the flip side under the ideal speed horizontal line (skier's force). Then, we should consider the combined result of these opposing forces (actual speed fluctuation).

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It would be nice to show a few scenarios (cranked turn and hard dig early, smooth progressive effort with patient start of the skier's lean, skier leaning late and too long) - each with the same area above the curve. Then, (and here's the tricky part) draw up how the two ZO Extreme settings would apply upon these three skier events. If the areas above the curve on the skier events are equal, if the areas below the curve on the two ZO settings are equal, and if the skier's force areas are equal to the ZO response areas; then the resulting curves would show how each combination would play out given the rule that ZO must fully recover to ideal speed between each buoy pair. Any mathematicians out there want to tackle these charts?

 

 

[Roger]

I don't agree with the C1 description. I use C3 because it is effected the least by the skier. If you don't think that is true, have a heavy skier ski C1 and then C3. You will hear a lot of throttle change with C1 and almost none with C3 indicating to me that the boat is slowed more and accelerates more with C1. C3 sounds the closest to PP from the drivers seat.

 

IMO, you should ski the various settings to determine the one you like and then just ski...

[skibug]

OK, here we go again; but i will play now that I have 2 season under my belt with ZO.

 

I agree with almost everything written here; but, the desciption of the C1 setting is that opposite of what I feel. Meaning that C3 is the heaviest "hit" at the earliest point and C1 is a softest "hit" at that same early point for the "C" settings. I feel C1 stays on me longer and I am less free at the ball. I do not ski C3; but, I skied both C1 & C2 for a while (now B3). I can compare C1 to C2 and conclude that I was "hit" harder by C2 but freer at the ball; C1 was less of a "hit" and not as free at the ball. I ski B3 now because I feel it is the blend I need to allow my ski to finish; be in a strong / leveraged position against the boat; and get the support (RPM) I need at the hook up. "3" is the hardest "hit"; but "B" lets me get in a better leveraged position against the boat so it doesn't break me on the hook up and still gives me the immediate RPM support so I don't sink or fall back.

[ToddL]

Thanks, Roger & Skibug! I agree when possible, a skier should try a variety of settings until something just feels right.

 

It is interesting that what you feel and what ZO wrote are backwards on the numbers. I can't claim to understand this, yet.

 

One possible theory: Since "3" lets the skier pull the boat down further (ZO's explanation), then the "Hit" must be more extreme to recover, but recovers quicker because of the extreme action. With "1", the ZO system attempts to initiate recovery right as the skier starts to lean on the boat, but the recovery is more subtle and takes longer.

 

So, I guess the ZO manual was missing a consequence of the trigger points:

1 - If the trigger point is shallow (meaning takes less skier force to start the recovery), then the reactive throttle is a small RPM reaction which then requires longer to recover.

3 - if the trigger point is deep (meaning takes a lot of skier force to start the recovery), then the reactive throttle is a large RPM reaction which then recovers more quickly.

[Dirt]

Great post. I have very limited ZO experience but when I experiment with it, I always seem to end up with C2 or C3 feeling the best (most similar to 2000 MC 1 1/2 to 1, PP Classic normal). I am interested in any other opinions on what setting feels most like PP.

Does Stargazer feel much different than Classic?

Anyone mess with the PP switch?

[Than_Bogan]

Cool charts! I hope to study them more at some point. (I am a total math geek in case anyone forgot.)

 

One thing that can be hard to remember, but ends up affecting this considerably: Ultimately, the system must actually get the correct time!

 

This means that any time it delays in making a correction, it will eventually have to use more throttle to make it up. I believe this is why 3 is the one that actually feels "hard" and 1 feels "soft." Specifically, by reacting sooner, 1 does less correction in total. BUT if this correction isn't enough, then it will end up gassing at some very bizarre time to make it up. So a skier who is heavier and/or pulls very hard may find that 1 feels completely awful. It initially doesn't do enough to correct, but that only delays the make-up to an even less convenient time.

 

And this is also why A can feel like you are being gassed into the buoy (though this one depends more on your ski style).