Ski course & rope length-Waterski magazine

[moski]

I’m trying to hunt down that picture. It was small article along with picture showing a boat, rope on pylon stretched out to a ball and it shows all different line lengths. Of course it showed 15 off rope past the ball and of course 43 off rope way inside the ball then all other line lengths too.

It was in the waterski magazine, maybe 2005 - 2013. I could be off on that. I’m searching thru my waterski magazine abs so far no luck on finding it.

Anyone have that or a picture like that?

 

Waterski magazine is awesome. Sucks that it’s no longer.

 

Thank you

 

[lundberg]

Something like this?

 

[moski]

Thank you that does help. But It was more of this view. Showing where rope handle at different line lengths are at the ball. How far they go past ball, some line lengths meet ball and how far short line is. Crazy awesome that these pros can do short line length. Looking to show my brother few things and would like to show him pictures.

 

I sure wish growing up we had boat and close lake nearby.

 

I’m still searching thru waterski magazines. Wonder is Todd Ristorcelli on here? That was cool picture if I can find it. Miss those waterski magazines.

 

 

 

[lpskier]

Having skied just about all my life, I am astounded by this graphic. If I understand it correctly, the skier must travel a greater distance the shorter the rope becomes. This thought never occurred to me even though I (thought I) had a good grasp of the concept of swing.

[dbutcher]

Assuming that shorter lines do cause greater travel distance, is that because the skier has to get higher on the boat to get outside the buoy? The buoys don't move - they are always the same distance apart. Does that also explain why shorter lines generate more skier speed?

[LeonL]

@dbutcher I'm sure your assumptions are correct. Also @lpskier I'm sure that you understand correctly.

[dchristman]

Mmmm... not so fast. I'm pretty sure this has been discussed at length (pun) before, but this is the only thread I could find so far https://www.ballofspray.com/forum#/discussion/11143/slalom-rope-angles

 

@lpskier I believe you are deceived because you are considering the skier's motion only from the frame of reference of the boat.

[Than_Bogan]

The skier actually has a great deal of control over the path taken, because they (indirectly) select the angle of the rope at each moment in time.

 

However, both some analysis I've done and some overhead shots suggest that the skier does indeed *prefer* a path that is longer as the rope gets shorter. The easiest way to see this is that the skier travels the same distance across, but increasing distance in the downcourse direction. They are basically taking a less direct route to the ball.

 

And at very short line lengths, deviation from the easiest possible path gets much harder really fast. So probably nobody will be choosing their own crazy path -- it's just too difficult.

[lpskier]

@Than_Bogan Exactly

[MichaelGoodman]

@Than_Bogan Than just curios have you ever figured out the amount of distance

the skier has to travel versus the boat given a optimal skier path.

[IGski]

I see a future BOS T-shirt showing this.....

[dbutcher]

I think the original question was "at what rope length does the handle no longer reach the buoy". That would be 11.25m or 38 off. It is just a subtraction issue. All the needed measurements are in the AWSA rule book. The turn balls are 11.5 meters (37' 8 3/4") from the center of the course. 12m or 35 off has 1/2 meter more rope than distance from center. The next shorter length is 11.25 (38 off), tow bar to handle. That is .25 meters short of the turn ball at 90 degrees. So every line shorter than -35 doesn't reach the turn ball. Everything longer than 35 off has line to spare. 32 off (13.0 meters) has 1.5 meters more rope than the distance to the buoy. And so on.

[Than_Bogan]

@MichaelGoodman I've never even been able to determine what metric should be optimized to call it an optimal path, much less actually optimize that magic metric!

 

So: No. :)

[Adam Caldwell]

I am trying to ski a shorter path at the shorter lines.

 

A longer path is possible on longer rope lengths, but not possible on shorter.

 

Yes, relative to the boat, the skier travels on a greater arc-length. But this does not necessarily mean a greater physical distance traveled relative to the course.

 

It just means that the skier has a greater deviation of acceleration/deceleration relative to the boat to be able to travel a greater arc-length without skiing a longer path relative to the course.

 

At longer lines you can get away with skiing a path closer to a square wave. This isnt possible at short-line. You have to ski closer to a sin wave, which ultimately is a shorter distance.

[Alberto Soares]

@adamhcaldwell - I don't see how is possible to ski a greater arc-length without skiing a longer path with a higher average speed

[Adam Caldwell]

@Alberto Soares - Shorter lines require a significant increase in rotational velocity around the pylon to maximize the distance in front of the buoy that can be used to decelerate & turn the ski in property timing with the boat and proper position at the ball.

 

You have to get clear on what "average speed" means. Average rotational (or angular) speed, and average tangential speed are very different. To me, "average speed" is a completely meaningless metric to try to analyze this sport with.

 

Instead of considering the "average speed" - think about time spent near both Min and Max rotational (angular) velocity. This is how its possible to run a longer radial distance around the pylon without necessarily riding a longer physical path through space.