Getting up to speed with ZO

[adam]

Do you think it matters what the driver does between the time he/she pulls up the skier and when the system takes over?  Here is a cut and paste from the ZO FAQ section under How does Zero Off work (Technical)?
"Simply pick your desired speed, and shove the throttle handle wide open. ZeroOff will take care of the rest. "  That is not how I drive, but some of my drivers have been doing that.

 PP with a servo motor does not result in a 1-1 correspondence between the throttle location and the throttle application between startup and speed lock.  This is because the servo is totally unwound at idle and as the boat accelerates to speed, the servo winds up some of the thread on the spool reducing the amount of throttle actually being applied.  This allows PP to have some throttle to work with to control the speed  during the pass.  If the throttle wasn't pushed down enough, PP would not have enough throttle "room" to operate.

 ZO on the other hand, does seem to have a 1-1 correspondence between the throttle position and the throttle application between startup and until ZO takes over.  Since everything is fly by wire, there is no need for stealing the throttle to have enough later to apply it, but ZO does use the final throttle location during the pass as a ceiling for how much throttle the system is allowed to access. If the throttle is not down far enough and ZO hits this ceiling, it will beep about 4 times or so.  You just have to make sure the throttle is down far enough to allow ZO to operate.  One interesting thing I've noticed is that the RPM number on the recreation screen seems to control when ZO locks on the speed.  One day while getting frustruated navigating through the screens to go from rec mode to tournament mode, the RPMs were adjusted down to around 2200 accidentally.  At 33.7 in recreation mode, we could not get the system to engage period.  After serveral attempts, we aborted the set and later decided to up this number back to 2800 after scratching our heads for a while.  It worked fine after that.

Now to my point.  Since ZO is 1-1 on the throttle until it takes over, at the point it takes over and if the boat is still accelerating like crazy as if the throttle is wide open(as their site recommends) the boat will overshoot the gate speed and be fast at the 55's.  ZO doesn't seem to aggressively get the speed to a certain point before the gates for some reason.  Testing my theory without a skier by driving the recommended way, the boat was 35.2 at the 55's and still 35 at the gates.  Then I accelerated as I normally do and backed off to near the right RPM's for the set speed and pushed the throttle down an inch or so after ZO takes over to give it room to work and it resulted in a 34.4 at the 55's and the gate. 

I have been struggling mightily this season behind ZO.  My 35's are only about 60%  with some OK days and some really bad days.  The last three sets(two different days) I had, I was 1 of 4, 1 of 1, and 1 of 4 at 35 attempts in perfect conditions.  I was ready to give up skiing.  I felt like I was flying at the gates and skiing behind a freight train.  I was struggling with my gate timing and ended pulling too much through gates and was flying at 1 ball and would be done by 4 ball.  We know how much ZO likes it when we pull and it seems to stay pissed through the rest of the pass.   Then I started looking into how the system was being engaged.  Yesterday I skied two sets in a fair amount of wind after asking my driver to not use the full throttle method.  The first set I ran 4 at 38 (I pulled between 3 and 4 and got slack at 4) straight up the line and was 2 out of 3 at total 35 attempts.  The second set wasn't as good at 38 but I was 4 out of 4 for 35 attempts.  Everything felt slower and more controlled.  Well, obviously I think it matters how the system is engaged.  I don't think following the ZO recommended approach is good. 

These are just my findings on our boat.  Hopefully, this will help someone else struggling with it.  I will caveat my findings though.  We have an 09 Malibu with ZO and our lake has a slight dog leg on one end and is a straight shot at the other.  I only took 2 appraches with the hammer down method and two with the ease to speed lock and press down method.  Both without skiers.  The ease to speed method seemed to achieve a more consistent speed.  I'm not sure I believe the speed being reported on the hammer down method because from the boat it felt faster than 35.2.  I will also say that ZO on our boat has acted strange and incosistent this year. 

Adam 

   

[Roger]

Can't tell anything from no skier pulls. Go back and enter the course with both pull-up methods at the same loop and have the driver write down the 1 ball times. That will tell you something (typical ZO 1 ball times at 55kph are 1.79). I have not noticed the boat running past engagement more than about 50 feet with a skier, so unless you have a very short setup, it seems unlikely you're going too fast at the gate to me. I have pulled a ton of skiers at three tournaments so far this year and I always scan the 1 and 3 ball times after every pass. I have never had a fast 1 ball time yet; for 55k, they are nearly always 1.79.

Edited to add: The tournaments were at Okeeheelee (2) and Miami (1), both of which have very long setup areas, hence the question about your setup length.

New this year is a difference between CC and MC. With the CC, you can come up to engagement speed and then push the throttle the rest of the way down at any rate you like. With the MC, if you advance the throttle quickly after engagement, the boat surges forward. ZO has said this is due to a change in the MC's ECM module and they're working on it.

 

[scoke]

 

 

where is the "none of the above" button?

 

edit: I was supposed to be the first post but Roger got one in there.

 

 

[baumer]

From what I understand we still need to engage ZO then push the throttle past that point just a little.

My Favorite part about ZO is having two distinclty different pulls behind two different boats with the same settings on ZO, hmm. Adds an element of spurprise and keeps things interesting to say the least.

Both Systmes have their quirks i guess.

[adam]

Roger. 

Since it is speed based, why would it matter if a skier was back there?  Wouldn't it still stabilze to the same speed after lock with or without a skier or with a big or small skier for that matter.  When I asked the driver to ease up to the speed and then push the throttle down another inch or so after it locked(usually about 150' before the 55 meter buoys), the speed felt slower at the 55 meter buoys and the gates.  It was kind of in line with what I found without a skier.  This weekend I'll check it again just to make sure.  I'll have the driver use the hammer down method from both ends of the lake and check what the ZO indicated speed is at the 55 meter buoy and monitor it until the boat reaches the entrance gates.   Then I'll have the driver use the ease up method and compare the indicated speeds. 

Our lake(Lake Holly) is around 2000' and has a slight dogleg at one end.  I have never noticed any times that are far off from actuals on any of the buoy times including 1 ball.  I'll check the 1 ball times as well just in case.

 Adam

[Roger]

Adam, it matters because of the drag of the skier on the boat and the fact that it's not just the GPS that controls the throttle, the ZO head has accelerometers in it. The "feel" of the boat going slower may be more the result of the difference in sound than actual. That's why I want to see the 1 ball times. They will tell all; if the boat is indeed coming in fast, the 1 ball time will be closer to actual (1.77).

[adam]

Roger,

OK.  I'll check the 1 ball times as well.

[LeonL]

I think there are good reasons for going with the "ease in" throttle method.  (Just as long as the additional "one inch" is applied after engagement.)  If the full throttle method is applied there will be an inevitable and perceptable "settling in" that the skier will feel.  If it's during the pull out or glide it will be a problem for him/her. 

[RichardDoane]

The "hammer down" position is only when towing jumpers, you should only add a little throttle after engagement when towing slalom is what I've been told.

 

Adam - what setting are you skiing with ?  I had been skiing on B2, and doing well, but changed to C1 this weekend with better results.

 

 

 

 

 

 

 

 

 

[Roger]

Adam,

What were your results from the weekend? One ball times?

 

[adam]

Roger,

Sorry for the delay.  I've been in a class this week.  We tried both methods over the weekend.  I almost always get a 1.77  1ball time.  Sometimes, I can get 1.78 using the easy up method.  The ZO indicated speed at the 55 meter buoy was around 34.7-35 with hammer down and 34.4-34.5 on the easy up method. 

 Adam

[Roger]

That's interesting. I have driven various tournament boats in tournaments this year and I don't recall ever getting a 1.77, usually 78 or 79. Anyway, 1.77 is actual, so nothing to help there. The speed difference you quote on the two start methods could be real or not, can't be sure since I don't know how fast the meter response is. However, if you feel that the boat is faster and the indicated speed is faster, then maybe it is. I'm driving a tournament this weekend with a shorter setup area; I'll record what sort of 1 ball times I get (one end is short, the other is long). I'll also pay attention to indicated speeds during the run-in to the 55s.

 

 

[adam]

Roger,

That sounds good.  Let use know what you find.  I have never seen a 1.79 1 ball time.  BTW, our course setup is not that short on either end. 

Thanks.

Adam

[LeonL]

I almost never see 1.77 on a Nautique.  I sometimes see 1.77 with a MC however.  Software is different, so????  Haven't driven a Malibu yet this year.  Will probably drive one ('09)at a tournament this weekend. 

[D Wolters]

1.78 with a 09 Malibu, every time

[scoke]

Theory:

No matter what method you use to get the boat to speed, Hammer down or gently ease in, the speed when the boat hits the gates will be exactly the same per boat/lake.

 When the skier makes their move for the gates, the speed obviously drops but then quickly re-establishes itself. Once the speed is established, the boat will add rpm to get up to the pre-set gate speed. My 2007 Nauti it's 34.8ish and 36.7(?, I quit looking when I realized it was the same every single time regardless of skier).

The boat knows where it is in relation to the course at all times. It knows it has to be at the preset speed for the skier to turn in consistently.

A couple of iterations ago, the gate speed was 34.2 and 36.0 while SG was literally up to +1.0mph hotter. Now ZO is 0.6 (+/- 0.1) hot on the gates every time.

Take video of the dash with someone else driving is an option. The video doesn't lie.

 

[scoke]

 

Interesting as I just watched 5 videos of the dash of the Nauti.

 36.7 was the speed for the majority. 36.6 once and 36.5 twice.

 The speed is obviously elevated from 36.0 as you can see it creep then settle in.

The question is, how hard you pull out affect the + or - 0.1mph you want at the gates? is this enough to make a difference?

 If you have the same consistent gate and practice it, it doesn't matter.

 

[Roger]

For 55k skiers at the tournament in Ft. Lauderdale last weekend, I noted 34.7 to 34.9 as the gate entry displayed speeds. 1 ball times were mostly 78 with a few 79s.

For 58k skiers, entry speed displayed was similar to what Scoke saw.

Boat was 2009 SN 196.

Note: These speeds were taken at the entry gates. The 55 meter speeds will vary depending on how the skier pulls out. Two handed gate skiers start pulling out before the 55s usually and 1 handed gate skiers and start just about anywhere from a boat length before to a boat length after so not sure the indicated speed would mean much at the 55s.