look how little angle you get out of the ball.

[kfennell]

here is a screenshot from last nights filming session, we went up a little higher so that we could see what the skiiers path looks like. I think he was skiing -32@34 in this picture.

 

I am sure that most will be surprised at what the cross course angle really is...

 

[andjules]

Very cool perspective. Thanks.

[kfennell]

Thanks,

 

Oh yeah thanks to Kris Richter for modeling, and feel free to check out the equipment used here (work in progress).

[Kelvin]

What line length was that. It would be cool to overlay different lengths.

[oldjeep]

Guessing you meant this:

http://www.usaerialimaging.com/

 

[kfennell]

I did, thanks! Better at flying then typing!

[kfennell]

@Kelvin I think it was -32 or -35 It was his third pass of his second set and he sometimes skis into 39 I think. I have tried to friend him on facebook to ask.

[6balls]

Yes very telling. I always find the comments about how much angle a ski gets etc to be a bit funny cuz I'm always taking too much. Have seen overhead shots like this before and always trying to finish more on that line instead of over-rotating.

[ToddL]

Kevin,

 

The absolutely ideal shots would be from directly above the boat's path, exactly the rope's length trailing the boat's progress, looking straight down. If only you could obtain that position and then match the boat's speed through the course... If only...

 

However, you could approximate that point where the skier's path and the boat's path intersect, say between 3 & 4 balls, and hover over that for a few shots.

 

Your images and some scheduled skiing (LL, -15 24MPH, -15 34MPH, -28, -35, -39 (Trent), etc.) could produce some new data for analysis...

 

 

Regarding the image above, I think it just looks like an efficient path from buoy to buoy. No need to over ski out of the buoy and risk losing speed while waiting on the next turn...

[kfennell]

@6balls me too on my new N1XT, I heard the term trying to ski back through the gates after 1 and it applies...

 

@toddl I can get that angle, or any angle, but but sure why it matters where you are seeing it from?

[ToddL]

@kfennell - the math/physics/analytical purists will always point out that conclusions are skewed by the angle of the camera.

 

For example, every photo of a skier taken from the shore is questionable since you can't confidently overlay the buoy line as a point of reference...

 

Obviously, overhead at any angle is a substantial, significant improvement. But why not grab the ideal angle and shot if you are able? That's all...

[evolski]

The photo shows a perspective that is different that we feel when we ski. I once has a chance to ice skate a course, buoys were sticking through the ice - and the perspective was that course seemed very narrow and a long distance between the balls, just like the photo above - the following spring I remembered the ice skating perception and it made a big difference in my performance.

[Wish]

@evoski In what way did it make a difference?

[mwetskier]

if you study the skis path closely you will notice how wide the track is at the finish of the turn and how it narrows out as the skier heads across the wake. the reason for this is because the skier initially turns his ski at an angle that is much steeper than he will actually travel. the skier is constantly being pulled down course at 34mph so in the early part of the turn the ski is sliding side ways much more than accelerating across course. as the cross course speed increases the track becomes narrower so the ski slides sideways less and tracks more cleanly along its ' linear ' direction. so no matter how sharp you turn your ski the actual path will be determined by cross course speed combined with down course pull from the boat.

[BraceMaker]

Looks like there is a "hook" off the ball that straightens out, wonder how much of that can be eliminated and how much of that is necessary.

[Zman]

I like the house still under construction, but the boat house looks complete. The only way to go.

[mwetskier]

@Zman -yeah its nice to see someone have their priorities straight.

[kfennell]

Everyones house here is like that! @zman where did you see the pic of it though?

[6balls]

Most of us think we back-side the ball when really dialed. Look at the boat gates as reference and that the skier continues buoy-width and has not completed the turn at that point despite being well past the ball...and then think about your short-line timing. Hmm...especially if this was 32 off or even 35 off. Don't get greedy when early at short-line.

[LeonL]

Another thing that I noticed, is the boat a good bit off center, or is it the angle of the photo that presents that perspective.

[kfennell]

I think it must be the angle? If you look closely you can see the prop wash is right in the center of the 5 ball gates.

[The_MS]

You cant judge a 200 by the prop wash.

[kfennell]

Good because that is a 196!

[A_B]

So little angle yet so much force to achieve it.

[mwetskier]

@kfennell -so your saying you cant judge a 200 by a 196?

[The_MS]

Then you may have a centering issue but it could be the viewing angle.

[OTF]

Regardless I think he missed the gates

[Zman]

@kfennell There was a pic with yur OP

[gator1]

Doesn't look like a pendulum to me. Doesn't look like a sinusoidal curve either. Looks like a straight line starting and ending with a semi-circle. Like the guy is skiing point to point. Just like those gate videos of AM. Could it be both pendulum and sine wave are wrong descriptors of the path? Let's discuss.

[mwetskier]

looking at the earlier part of the skier path that is not confused with white water i cant see a single section that looks even remotely ' straight '. to me it looks like one long decreasing-radius arc blending at the finish of the turn into the next long decreasing-radius arc. the only straight sections i can even imagine in a successful slalom run are the glide before turn in and the ride out the other end to the drop point.

[SkiJay]

Here is some food for thought @mwetskier‌. This is Andy Mapple at -32 and -38. There are some pretty straight lines at -32 and even straighter lines at -38. What I'm seeing at -38 is: turn, straight, edge-change, straight, turn, straight, edge-change, straight, etc.

 

[gator1]

@skijay. Yep. I was particularly struck by that gate vid of AM some months ago. I always imagined a arc from edge change to turn. Not so. Looks straight as a die to me. Has some very interesting implications geometrically, especially when rope doesn't reach bouy.

[mwetskier]

@SkiJay -how in the world can you tell from that go pro video whether the ski is on a ' straight ' path of not? without at least two clear points of alignment theres no way to tell if your going straight or not.

[SkiJay]

@mwetskier‌ There are three points. The GoPro and the tip of the ski are two fixed points, like the sights on a rifle, and there are the trees on the horizon. When the trees in the distance appear stationary relative to the sightline from the GoPro through the tip, the ski has to be travelling straight at them.

 

It may not be laser-straight, but like @gator1, I'm surprised by how straight it is. I would have guessed that the pre-turn would have been more of an arc.

[mwetskier]

@SkiJay -i was referring to two points of alignment *plus* the point of view which i assumed was implied. in my work i sometimes have to analyze detailed mechanical movement in order to best serve a client and due to the individual nature of ergonomics each clients needs are usually unique so sometimes i have to use software that breaks a video into individual ' frames ' of around 30 per second. except for the gate glides I can't find any three consecutive frames in that video that triangulate identical site points which means theres no moment longer than 1/15 th of a second when the skier might be going in a straight line. i am looking as closely as my software lets me but i cant see the straight lines in this video that you guys see and like dave nelson says its better to believe data over perception.

 

a second consideration is for a skier to be going in a straight line the down course pull of the boat and the skiers side ways movement both have to be perfectly coordinated. so if the pull of the boat is constant then the skiers speed also has to be constant but i dont think we see that very often. if the skier is travelling at any angle to the boat path the physics say he should be either accelerating or decelerating which means his speed will not be constant but the boats speed will be so the combined path must be an arc of some sort. it may have a very large radius and look kind of straight but i dont see how it can be truly straight.

 

my own theory is that skiers at that level are very good at controlling there speed thru controlling the radius of the skis path by varying their own body lean plus the angulation of the ski. i think no matter how much speed a skier is carrying the sharper the radius the more the ski will decelerate along its current path. on really short lines i think guys like mapple and smith have learned how to choose a path that will carry them across and out bound without scrubbing too much speed or gaining too much speed which means that maybe its all about timing.

[Dusty]

Not really sure what sort of 'curve' it is but I do know that adding parametrically, a straight path (down course path of boat) with a circular path (rotation of skier around the pylon) you get an approximation of a sine curve. I have a video of Marcus Brown and some others taken from a helocopter reasonably direct overhead and you can defintely see the sine curve-like shape of skier paths. Even directly behind the boat, you are getting dragged boat speed down course- and shouldn't the smallest change in direction (straightest path) be there at centerline?