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Slalom Water Skiing - the sport explained

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JeffS

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Lakeliving asked for a thread about competition water skiing...so here it is.

For starters - a drawing of a competition course with measurements between buoys.



In its simplest form, it's just a course that includes boat guides, some entry and exit gates, and 6 balls that you have to ski around, in order without missing. Sounds easy enough? Yeah...no. 

In this post, I'll give you the basics of the slalom course and what skiers do to make it a competitive sport.

In later posts, I'll tell you a bit about the boats, the equipment and the skis...which is pretty cool stuff in my opinion...especially since all I am anymore, is a driver.

On a ski boat, the ski rope is attached to pylon afixed to the floor at the approximate center of the boat. When the boat is tracking properly through the course, the distance from the pylon to the buoy ball is 38'. 

Skiers can start with a line as long as 75'. And the speed of the boat is variable from 24.9mph to 36mph. Scoring is a combination of how many balls the skier completes and how fast the boat was going. Complete the course at 75' of rope and a particular boat speed, and the next step is to shorten the rope.

Slalom ropes have colored sections that are looped together to form the proper line lengths. The first drop is 15'. This is called 15-off. At this point, the rope is now 60' long. There's another drop at 22'. Cleverly called 22-off, the rope is 53 feet long. The shorter the rope the faster the skier has to move from one side of the course to the other because the pendulum is shorter. The geometry required to get through the course changes dramatically at each line-length-change.

As skiers advance, the line shortens like this.

15-off. Rope is 60' long.

22-off. Rope is 53' long.

28-off. Rope is 47' long.

32-off. Rope is 43' long.

35-off. Rope is 40' long.

38-off. Rope is 37' long.

39.5-off. Rope is 35.5' long.

41-off. Rope is 33' long.

43-off. Rope is 31' long.

And as skiers advance more...the boat speeds up. Scoring is heavily dependent on boat speed. Running 6 balls at 32 off and 32mph may get you more points than running 38 off at 30mph. Once you select a boat speed though, there's no going back. And most competitions have mins for boat speed, or constant boat speeds i.e. - the entire competition for men at 34.2mph and for women at 30.4mph.

Once the rope is set to 32-off or shorter, the skier has to swing almost perpendicular to the boat in order to clear the ball. No matter how short the rope gets...the ball is still 38' away. At 38-off, the rope is shorter than the distance between the tow pylon and the ball. The skier has to be perpendicular to the boat and use their height to get the ski around the ball.

Speeds across the lane can break 65mph very easily. And I've seen a skier complete the course at 36mph and 41-off...with the announcer claiming he was breaking 70mph across the lane. That's just insane to watch.

That's the basics. Scoring is simple. Speed first...in order to beat another skier who's skiing at 36mph...you have to ski at 36mph. After that...it's line length and ball count. "36mph, 3 balls at 41-off" might be a winner in a particular tournament. 

Next up - the driver, the boats and the equipment. Just a heads-up...driving is way harder than it looks. 
 
That's all really interesting.  Watched it on TV lots of times, but didn't know much about it.  Learned more reading your post than I ever knew about the sport.  Thanks!
 
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Don't forget to tell Lakeliving, being a tall guy, that he has a natural advantage at those short line lengths ;-)
 
Yeah, I saw him kneeboard though.
 
Now the boats.

Competition tow boats are purpose built to do one thing. And I can tell you from experience, they suck at everything else. They are all direct drive, with a big V8 in the middle of the boat...a straight shaft out the bottom and a very finely machined (translation...expensive) nibral prop that is underneath the boat. The prop is not behind the boat. 

The prop wash creates lift on the bottom of the boat. Combined with the flat bottom, these boats produce very little wake at certain line lengths. See this picture.



That's my son Zachary...lovely shot...I know. My wife got lucky with that shot. We're not that good at photography. We just got lucky. But more importantly, look at the wake he's about to cross. My tow boat is pushing through the water at 32mph in that shot. There is virtually nothing but 2 small bumps that he has to cross.

A proper tow boat can bring a skier up on plane in less distance than the length of the line he's holding on to. It's nearly instantaneous speed. They are amazing...if you ski. If you don't, then you need to know some good sources for kidneys. If you end up in rough water in a competition ski boat, you need to have your kidneys replaced after every outing. The whole hull is designed to sit on top of the water at the rear, and push water out flatly in the front. 

There are only a couple of models of new proper ski tow boats. Malibu makes the Response. Mastercraft has the ProStar. Correct Craft has the Ski Nautique and there are a couple of other regional players. It's sad really - these boats are getting hard to get. I have a Malibu, as does Zachary's coach. We like them. They are beasts.

The boats have a GPS controlled marine-version of cruise control. Called a StarGazer or PerfectPass. These are extremely precise and let you set the speed in 2/10ths increments. The driver doesn't have to control throttle anymore. The boat does it for the driver. No matter how hard the skier pulls through a pass, the boat will hold speed.
 
Here is a nice video from our home-town tournament - the Malibu Open.

It's actually one of the biggest ski tournaments (excluding championship tournaments) in the world. And it's in my own back yard. Very cool in my opinion.

http://youtu.be/a0he0jqplXw
 
Great information! Thanks for the lesson Jeff. I can't believe the speeds reached between markers. Wow! I have a long long long way to go Tom before my height would have any real advantage. I would be the guy showing up on two skis and running a 15' On (get it-extra rope length!)

And I'm not sure how to take Dan's comment on my knee boarding. He's probably jealous :p

My neighbor on one side of me has a ski centurion, and on the other side of me they have a G series Benny and an older mastercraft. I have to say, it was fun watching my neighbor try and pull his ski boat in the lift after getting rid of his stern drive four winns. looks like a slow speed handling nightmare.

I'm going to spend some more time on the ski's this upcoming season and see how long it takes me to get down to one. And when you say those boats pull a ski'er up within the length of the rope, are they starting on two, then ditching one or starting on one? I would image one as my father in law can get up on two ski's in leterally 10 ft behind our boat. I'll have to try and find a video later.

Come on spring!
 
The driver and the ski. Last post unless someone has questions.

The ski boat has the engine in the middle, and right below the engine are tracking fins. All of the weight is in the exact center of the boat, and steering is controlled by a rudder. Swing the rudder all the way over and you can actually get the boat to pivot on its center point. As momentum shifts, it will slide out, but it handles totally different than anything else on the water. These fins are very necessary for a slalom skier.



 

The boats control their own speed now. But the driver has to anticipate each turn that the skier is going to make. It's a hard pull, and the driver has to correct the boats track exactly as the skier is coming around the ball. If the skier can pull the boat off a straight line, the geometry will be messed up going in to the next ball. The rope is connected to the pylon in front of the motor box though, so the pulling doesn't happen on the stern. it happens on the middle of the boat. So the boat doesn't get pulled off yaw - it's more that the boat gets pulled to one side or the other of the boat guides. The boat guides are set 8' apart. And the boat is 7-1/2 feet wide, so there are only 3 inches on either side of the boat that the driver has to hold in order to be centered in the boat path. A little bit tricky. Screw up, and it can cause a significant spill for the skier as well. They don't much like that. My son won't ski behind a boat that is not driven by me, his coach or a couple of other known-experienced drivers. 
 
lakeliving said:
... and an older mastercraft. I have to say, it was fun watching my neighbor try and pull his ski boat in the lift after getting rid of his stern drive four winns. looks like a slow speed handling nightmare.

I'm going to spend some more time on the ski's this upcoming season and see how long it takes me to get down to one. And when you say those boats pull a ski'er up within the length of the rope, are they starting on two, then ditching one or starting on one? I would image one as my father in law can get up on two ski's in leterally 10 ft behind our boat. I'll have to try and find a video later.
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That's getting up on 1 ski in the length of the rope. 

And slow speed handling is really very excellent if and only if you know what you're doing. You can't steer in reverse - and at slow speeds there is always prop-walk...which is the nature of the boat to turn rear-end starboard in reverse. With the giant fins on the bottom, the boat goes in a straight line like there's no tomorrow. To turn at slow speeds going forward, you have to give it a touch of throttle to get the boat to change direction. Just a touch. Tiny bits.
 
And the ski.

Oh holy hell...the ski. Competition skis are silly-crazy-you-said-what? kind of expensive.

Like $1,000 - $3,000 plus boots which are about $250 each. And that's not a case of skis. That's one ski. 

They don't like to ride flat. You can't just get up on the ski and travel around behind the boat. They have such flex, they just bounce around a slap themselves everywhich way if you ride them flat. They are designed to live their entire lives on one edge or the other. 

There are 2 fins on the back. One perpendicular to the ski like you would expect, to give you directional stability. The second fin is like an aileron. 



 

It takes a lot of professional setup, and that little 2nd fin does a whole lot of work. The ski should be set up so that the individual rider's ride angle puts that second fin level through the water. The skier wants it neither lifting nor pushing down as the skier is tracking. What it allows, is when the skier gets a back-foot-low ride angle, it produces lift and helps recovery. And when going in to a turn, the skier can rock forward on the ski ever so slightly which will give that second fin a downward angle which is like brakes. It pulls the ski deeper and creates drag if the skier needs to slow down. The movements are so small though - and that's what makes slalom skiing so hard. Full weight, being pulled by 300hp boat going 36mph through water...and your movements and body position changes have to be tiny.

 

And that's all I have to say about that. 

 

Unless someone has questions.   :)
 
Andy - Just giving you a hard time.  I was pretty sure you never water skied before since you just started kneeboarding not long ago.  I'm sure you would be a natural at it though!

JeffS - Thanks for taking the time to post all this.  It has been a really interesting read.  Quick and to the point with lots of good info.  Unlike me  - I tend to go on and on.  All I can say is my posts would be shorter if I had more time! 
 
Memories.... way back in the day I had a Mastercraft and we had an Accufloat slalom course in front of our house. Skied like crazy for about 4 years, best I could do with any consistency was 22 off. My attention turn to trick and barefoot. We actually had Bob LaPoint ski with us (or show us how it's done) one afternoon. My neighbor owns Pleasure Craft Marine and lots of guys and girls would come through trying the latest in ski boat power back then.

Remember when Sammy Duvall broke the 200 foot ski jump barrier? That was an awesome jump at the time. I have no idea what lengths are being jumped today but I'm sure well over 200. I think even Sammy made a 220 jump before his career ended.

Great information you posted!!

Steve
 
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Very Interesting.  Thanks for taking the time to post JeffS
 
This looks interesting..  Wouldn't want to fall, especially when there is a boat close behind.

 
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Maybe that is why the average life expectancy was so 45 back then!! Talk about unsafe!!! And no spotter while running down logging rivers. Wow. The risk manager in me is freaking out! If you make it to the end alive you win!
 
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Not to be a spoiler 

BUT

Here at The Lake we have extreme skiers as I mentioned in the previous 

Can you Believe? threadFor those of us who don't ski and those who may not be at this level

It comes at a huge price

Many here tell me they lived on the water 

Perfecting their sport to the pro level

Unfortunately their legs , knees and etc have taken a huge toll

Most say that they were young and foolish 

None say, it is worth the pain their in now

Once again I don't ski

But many of my friends have in the past and many younger ones do at present

Their love for the water costs them like any sport 

Gymnastics, football, baseball, hockey etc all pay a price

Not A Warning.... But Some Food For Thought !!

94687663.jpg
 
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This thread about skiing got me looking at skis for the kids on Craigslist.  I just picked up two pairs of combos for the kids this weekend.  67 inch HO Sports for my 15 year old and her friends.  And a pair of Obrein kids skis (very fat front tips) for my 11 year old.  $20 a pair.  They have the normal scrapes and scuffs from normal use (they won't be Christmas presents), but all the rubber boots are in great shape.  The kids will have a ball with them this summer!

This is a good time of year to buy some used skis...
 
Sounds like some good finds there Dan. I've been hitting the treadmill and splitting wood by hand to get in better shape so I am in better shape this coming season. If I can get to where I can start on one and do a couple turns to spray water I'll be happy. 
 
Before I get the "pics or it ain't true" from someone, here you go.  Almost felt bad about the price, so I didn't even ask if he'd take less. 

If JeffS hadn't started this thread, I doubt I would have run across these.

 
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lakeliving said:
Sounds like some good finds there Dan. I've been hitting the treadmill and splitting wood by hand to get in better shape so I am in better shape this coming season. If I can get to where I can start on one and do a couple turns to spray water I'll be happy. 
Click to expand...
Then go look for some skis now!
 
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