Real difference between boats.

[Horton]

A couple of weeks ago an engineer proposed to me that the biggest difference (for the skier) between the Malibu, CC and MC is the combination of Engine, transmission and prop. With a 07 CC I give my real stats and then tell the driver to add 30 revs. With a Malibu I only ask for 10 revs. With the MC . . ?

 

Does anyone know the real details like  - this boat 4 blade prop 1:1.5 trans  . . .  That boat . . . .

Please spare us the “BrandX Boat Rocks and is the only boat” crap. The point is when you go to ski with a different brand what is the deal.

[boarditup]

Sort of....

 I sell a lot of props for inboard boats (www.boarditup.com).  Each owner, hull, engine, and tranny combo seems to perform best with a certain prop for most people.  However, there are subtle differences between each combo.  There is a profound difference between identical model engines.  Some have 20 hp more than rated, many have less.  That accounts for the differences between prop preferences.  On PP, that can me a differnce between PP settings for resistance, KX, and PX to have the same feel between two identically equipped boats.  The boat's owner also has a set of expectations that the prop has to meet.  Some like blistering hole shot while others like to max out the top end while others like the best speed holding at a set speed.

As for your question between the various boat model comparisons, that would be a lot of data to evaluate an then you have the differences I spoke of to account for.  Hard to do and I wonder if there is a good way to get it done.  You could go to several tournaments over a period of time and take a survey of the drivers and skiers before and after and compile the results - subjective, but it should average out.

Great question - good thinking.

 Karl

[Old MS Accout]

If PP is dialed in, you should not be dealing with any problems. Wind and crew wt are the only factors. Now site to site a boat will require a plus or minus, but it should be standard from skier to skier when you know what the base line change is. I ski behind a 07 196, a 06 RLXI and a 94 PS190. On our lake with no wind, all three boats are 00 for adds to come in. Now at 35/38 the driver needs to boost it a bit, but that is going to happen.

Your problem is that you do not want the boat to know you are there. in your case it does and it is fighting back.

When you ski in a tourney you dont get the option of telling the driver to add 20 rpm. They figure it out after your opener and adjust from there. But if a boat is properly dialed in, it should not very alot from skier to skier.   

[Horton]

for starters I would like to just see a compairison of props, trans and hp (maybe boat weight)

[Roger]

You're not giving your "real stats" if you have to have 30 revs added for an actual. You should be giving your pulling weight, not your real weight. For example, I weigh about 187lbs right now, but give 175 as my weight in tournaments. This achieves actuals with no wind and zero entered. We have a Women 3 skier in our club who weighs 130lbs, but has to give 110lbs or gets burned. It's your pulling weight that you should give the driver. Adding or reducing rpms are to compensate for wind and such.

 

For CC I use Normal KX (no switch on any). For MC I use Normal. For MB I use ++.

 

There is one MC down here (South Florida) that I will use + or ++ on next time I get it, it just feels too soft compared to the other MC's I've drawn here.

CC uses 4 blade prop and 1.26 tranny.

MC uses 4 blade prop and the powerslot version used to use 1.5 tranny. I think current models use 1.29 (can't remember exactly, but it's close to what CC uses).

MB uses 4 blade prop and 1.0 tranny. This is the reason it feels different than the other boats (IMO). It is not able to create the torque a geared tranny is and therefor pulls longer resulting in a chase the handle kind of feel. ++ causes a harder, but shorter pull which I feel makes the boat closer the the other two in terms of the feel of the pull.

YMMV

 

[Horton]

MS I always tell the driver to add revs for the first pass. Sadly I pull more then should and I do not want the speed going up as the rope gets shorter. With the CC I will take 30 to 40 revs. With the Malibu I will take 10. Don't want to mix that up!

[Director Darwin]

Roger: 

We have a Malibu LXI on our site w/ the 383 Hammerhead 400hp w/ a 3-blade prop.  Softest boat of all 3 we had at our tournament.  As stated previously, HP ratings can vary significantly in identically equipped boats.  Baselines can vary as well and effect the feel due to how that particular engine's power curve flows.  I drive all 3 in 8-10 tournaments a year.  I'm amazed at the different baseline settings identical boats need to pull actuals.  Therefore, there is really no "magic-bullet" settings for each brand of boat.  It's a crap shoot if you've never skied behind the boat before or the PP has not been set up appropriately for that boat.  I typically like the feel of CC's but the boat I drew at Nationals was the strongest I had skied behind all year.  The driver agreed when I commented about it.  He said it was probably a good jump boat!

[Horton]

Roger,

I have been told to no re-rate myself and to do it with Revs because . . .  errrr because someone smart told me to. Thought that it had something to do with how PP does diffent stuff with extra weight vs. extra revs.

[Horton]

By the way I skied behind a promo Malibu this week and the pull is like a Brick $**t House. If I practiced behind it I would like it but gosh. I practice really fast and the darn Malibu was working me with acutal times. 

[Director Darwin]

John:  Propping a Malibu correctly is paramount.  Chad always gets a special prop for his boat and it works well.  Of course, the Malibu you skied behind could have had a more powerful engine than normal or the SSB could have been configured wrong:  hotter first segment / slower second segment = actual.  Next time you ski behind that boat, try KX-.

[Old MS Accout]

I used to be a Normal and 10 guy and swore by it. But then I ran into boats with engines that I had no experience behind. It would freak me out to much to be dealing with that stuff so I turned it all off. My typical times in tourneys this summer are usually like this. 28 off opener, 16.90. 32 off, 16.92. 35 off, 16.95 and 38 off 16.97 if I am lucky. I have not had a 28/32 0r 35 over 95 this spring at a tourney.     

[Horton]

I agree with MS. I never mess with KX/PX because it is just not the same from boat to boat.

[Director Darwin]

I agree with MS. I never mess with KX/PX because it is just not the same from boat to boat.

Neither is the engine. 

I don't typically play w/ KX either (don't use the switch) but if you are practicing behind an unusually strong boat, it can help even things out.  When it comes to tournaments, I agree.  Not worth the guessing.

[Horton]

Date      :           6-27-07

To        :           National Promo Team

From     :           Dave Doidge, Nat'l. Coordinator

Sub       :           "Zero Off" Speed Control

Dear Team Members,

This is to inform you that 2008 Correct Craft National Promo Team boats, including wakeboard models, will be factory-equipped with the new Zero Off speed control system.  Zero Off is a GPS-based system.  Some product information is available on the internet at ZEROGPS.COM. 

We are arranging for Zero Off to be installed in a very limited number of National Promo Team boats in order to begin exposing the system to tournament skiers and drivers.  This will likely be limited to just one promo boat per USAWS Region.  Zero Off can be installed side-by-side with Perfect Pass; with one system turned "off" the other system functions normally.

2007 Ski Nautiques equipped with Zero Off have been tested and approved for all USAWS sanctioned events.  An updated 2007 USAWS Approved Towboat list is posted on the Promo Team website.

More information will be forthcoming, but for now we wanted you to be aware some rumors you may have heard are true; Zero Off will be the exclusive system for all our promo boats next year.  Please contact your Regional Coordinator with any questions or comments. 

As always, thanks for everything you do promoting Nautiques at tournaments across the country.

[turkey]

Interesting. The "put in real weight & add/subtract rpm" comes strait from USAWS as the proper way to retain gate pull and SSB (PX also if used).

Now that Johns goated me onto his site I'll clean this up. PP used skier factor to fine tune the pull up into the gates, the "softening" for SSB and for PX. Was talking to Wayne Canfield a few weeks ago where he commented that the recommended way to provide numbers to a driver was real weight with an RPM offset. My imperssion is that this is the convention in our area, however I canont speak for USA or other areas. Now I'll need to take him to the woodshead about this user name. . .Tony

[turkey]

So with the wining over, the discussion John & I had that started this was on hull shape and tranny-prop configuration. A few years ago we were baselining boats for tournaments & found it necessary to drop 20-40 rpm on Malibus to prevent from pulling hot times. The perception at the time was Malibu was a cleaner hull which allowed the boat to run. My own thoughts were that the 1:1 tranny & smaller prop also contributed due to less drag over the gear reduced & larger props used by CC & MC. Several years ago Malibu was the only ski boat the could touch 50mph, with the others hitting ~45. A few extra Hp may have contributed, but generally hull configuration is the limiting factor (i.e., drag resulting from wetted surface area, length/width ratio, transom V angle, pockets, etc). The same engines we put in a ski boat would push a cleaner sport boat over 70mph. Hence my rational that Hp plays a subordinate role.

 

So with all this rambling, how do we account for ski pull variations within brands? Variations in manufacturing (hull), installation (shaft & rudder alignment) are possible root causes. PP has worked a number of "factors" over the years but is in contention with USA on their desire to lock into a configuration, and the boat manufactures' design evolution. GPS offers a more direct solution due to kicking out the middle man (RPM). Then it's a matter of defining (us as skiers with USA), and establishing (implementing via some control) appropriate acceleration to return to a set speed & provide all skiers with the same "pull."

 

Tony

[Roger]

Horton said: "I have been told to no re-rate myself and to do it with Revs because . . .  errrr because someone smart told me to. Thought that it had something to do with how PP does diffent stuff with extra weight vs. extra revs. "

 

There are a lot if interesting comments in this thread, I'll say that.

Here is my response (and I'm certainly not the expert or law on such things).

 First, you are right that the kx and px and gate factors are dependent on the entered weight. However, if you pull less than your real weight, wouldn't you want that? KX (how aggresive the throttle responds to your pull) would be a bit less as would PX and the gate factor if entering a lesser weight. Opposite for entering a greater weight of course.

Second, as a driver I can say that I'd much rather start every skier off on the opening pass with the same offset (zero on no wind days). In my experience, many skiers give their real weight (or lie about it), but do not give any offset nor is there any provision on starting dock boards for a starting offset. Therefore, I would (and do) get something other than an actual on these skiers. When a skier gives me their pulling weight, I can get an actual or very near it every opening pass. If a skier says 190lbs and a +30 offset and I have a +10/-10 wind, I have to start at +40 and remember the offset I started at (not that big a deal for me, but I know some drivers that would struggle).

I have been to three driver clinics and have never heard anyone say the skier should put in a weight and an offset. I'll have to do some research on that one. I'll let you know what I find out.

 

[Director Darwin]

Roger - I have two skiers at my site that do just that.  They both weigh in the 175 range but ask for a -10 offset.  This keeps the KX in the proper alignment but allows for a more consistent time.  Neither of these guys pulls very hard so their "skier weight" and actual weight don't match. 

I've had several skiers request this at the starting dock and I'm always willing to abide.  Afterall, you can lie to me but you can't lie to the computer!

[DW]

Hull configuration and wetted surface certainly play a large role in the drag influence on a ski boat, they are high drag due to lots of wetted surface mainly caused by the hook at the trailing edge.  Therefore it takes a lot of HP to make them push through the water and thus relatively low top speeds.  The engine is subordinate to the prop, since the prop is what delivers the HP to the water.  The variation in props and there is a lot, is most likely what causes the variation in settings across similar boat brands, the difference in hull style is what causes a difference between brands.  My experience is both are first order contributors.  The next order differentiator is most likely the actual engine power configuration and variation amongst hulls of same brand boats.  On the trans issue, it's all a matter of where the boat is operating relative to the power band and thus how much power or torque a skier is pulling against, and the prop's ability to deliver that power to the water (slip or lack of).  It's all a matter of what's left after you subtract out the amount needed to propel the boat at that speed to compensate for skier load.

Comment on level of HP, a 100 hp increase on a boat yeilded an 11 mph difference in top speed (Malibu) and a simple prop change results in a 2 mph change in top speed, so you can see a prop can be as effective as a 20 hp change.  If you look at top speeds of a early '90's boat with the 265 hp Mercruiser, say 44-45 mph and then with a 320 hp Monsoon at roughly 50 mph, the two power level v. top speed trends are pretty consistent.

[Roger]

Turkey said: "Interesting. The "put in real weight & add/subtract rpm" comes strait from USAWS as the proper way to retain gate pull and SSB (PX also if used). "

 

I can find no reference to this on the USAWS website, can you point me to it please? In addition, I asked one of the best senior slalom drivers on the planet (pulls Open, had the world record tied, pulls Big Dawg, etc.) about it and the response was "Never had a skier give anything other than speed, weight, KX, and PX.

Then I sent an email to one of the clinic hosters who was on the speed control commitee until last year. He responded the same way, "never heard of that."

 Neither of them is aware of the USAWS information you site...