We Have the Technology

[tap]

I'd like to thank the guys over at Denali Skis, and the local skiers who were extremely accommodating guinea pigs, for hosting and enabling some data acquisition beta trials last weekend. We've been working on a new approach to real time data collection that produced some really cool results. In a nut shell, we instrumented the pylon of the boat enabling continuous measurement of applied load and load vector direction. I'm now sitting on more data than I know what to do with. Our primary goal was simply to see if we could make it work. I'd say for a first effort it was wildly successful. I'm still working on sorting out my post processing methodologies, but here's a teaser sample of one of my 34 mph/28 off passes. The graph is on a time scale basis, not distance. The green is angular position in degrees of the load vector vs. time (it gets a little wacky when the load drops off but is pretty good as long as there's some load on the line). The blue is applied load in pounds. The course is plotted for time reference only.

 

 

 

There is a tremendous amount of information that can be learned from this type of data. It allows you to be completely objective in dissecting your abilities. Caldwell was nice enough to crush a 39 off pass on one of his new 2017 model skis while we were recording, so we spent a couple hours just staring at an overlay of my 28 off pass with his 39 off pass. It was both humbling and encouraging at the same time. We spent about an hour just looking at the gate approach alone. There were some pretty big differences and not at all what I was expecting. Needless to say Caldwell definitely practices what he preaches in regards to the GUT theories. I walked away with about a dozen clear opportunities for improvement, some were extremely obvious and some rather subtle. We're still sorting out ways to improve the data collection process and tidy up the post processing, so I'll keep it brief for now. But I'll say it's already proving to be extremely insightful.

 

Here's the same pass as above zoomed into 1 ball to 2 ball with an added overlay of an extremely fluid open level skier running 34mph/32off. (not Caldwell this time). As you can tell, there's a pretty big difference in how fast the open level skier gets on the line coming out of 1 ball, he's much smoother at getting on and off the line, he has a higher peak load, gets off the pull much sooner, and is sitting pretty for 2 while I'm still pulling long. I'm the blue/green data, the open level skier is the gold/bronze.

 

 

 

@adamhcaldwell @AdamCord

[Gloersen]

@tap - looks like peak load occurs at ~ -20 degrees for both of you? However open skier gets to -20 earlier.

 

Both RFF or was open skier LFF with a quicker 1B turn? Both B2 setting or was open skier "C" something?

 

Of course there are all sorts of plausible reasons for the differences; the trick being how to decode the observed data of the better skier into one's own...

 

Cool data!

[Mick04]

I would love to see it in trick mode. Actually, with the same skier, but A,B,C & Trick mode overlayed.

[Jody_Seal]

We did a lot of very similar testing in the early day's of speed control. collecting electronic information from various instruments installed in the boat, including a in line prop shaft load torque instrument, a potentiometer on the steering wheel, two accelerometer's , a instrument on the pylon that measured deflection in load and foot pounds, A radar gun and a old magnetic style timer device, RPM signal and even fuel flow!! All going through a data communication box and then processed through an old brick lap top with in house data acquired programs..

Funny the graphs above are nearly identical to that of what we acquired at the time. our load #'s seemed a bit lower then what is presented but hey these guy's ski a bit different now a day's.

Cool info!

[disland]

It would be super coll to see a video with the load graph superimposed so you could see the skier stack and the respective load level.

[DW]

@tap : great work to all, congrats. @disland : Dartfish does the video / data overlay you are interested in, used frequently to compare (in my case car racing) different athletes participating in same sport.

[AdamCord]

@scotchipman I believe @adamhcaldwell peaked at about 750lbs at 39...not bad for a 175lb guy!

[Razorskier1]

The amazing thing about @adamhcaldwell generating that much load is that he is moving very, very fast and efficiently (far more so than say, me). It's one thing to generate 750lbs because you are skiing wrong, completely another to generate that kind of load while moving fast!

[tap]

@Gloersen I'm pretty sure he was right foot foward (same as me), no idea on letter/number.

 

@Jody_Seal I had heard there was some cool work done in that regard. Does any of that data still exist, and available for disclosure? It'd be cool to compare. I debated on how best to attach the insturmentation, we found a means to make the gauges exteremly portable so I can jump from boat to boat with minimal setup. The possibilities are endless, once the base acquisition system is setup it's pretty easy to keep tying in other sensors. We talked about tying into the cam or crank sensor... maybe some day we'll get around to it.

 

@disland We video'd most of it, just need some more time to go through it all.

 

@scotchipman There's a reason his pylon is always coming lose. The peak load is cool but somewhat expected if you've ever seen that guy ski. What was way more interesting is the speed he carries through the swing and how early he gets up on the boat. Once you have angular position plotted you inherently have angular velocity as well.

 

For now it's just an experiment in what's possible, and to see if it holds any merit as a traing tool. In that regard I think we're onto something.

[Horton]

@tap once the methodology is defined what would you guess the hardware cost would be to replicate your system? Is this something you are considering as a commercial product?

[tap]

@Horton Hardware all up is cheaper than a new ski. No plans to commercialize, at least not a hardware solution. The reality is everything is readily available off the shelf, the barrier is in the knowledge to make it all work and interperting the data. If anything, I think it makes a lot more sense as a service than a product. With the time it takes to review and analyze the data I can't see anyone doing it every set out. Most people don't even video all the time. Now if a ski school or other setting of the nature was offering it I think that could be pretty cool. Ski all day, review data at night. Once you know where your problems are it still takes some time to improve your technique. For example, I've looked enough at my own data now to know that I don't get across course near as fast on my toe side pull as I do heal side. I now have a specific area of focus for improvement, but it's still gonna take me months to become a better skier.

 

Once I get the bugs worked out it'd be interesting to see if anyone wanted to be measured. Since it's so portable there's definitely some options available.

 

The biggest value I see is in comparison to "gold standards". If you could have your data overlaid with a pro skier whose style you were trying to emulate, that would be sweet.

[Wish]

There are some pros I would not want to try and emulate so if I get to choose who..that would work. :) Great work @tap I have a sneaky feeling a lot of the data will be used by Denali. ;) Looking forward to hearing more. And more then happy to be a guinea pig.

[tap]

No no @Wish ... just happened to randomly be in Charleston... nothing to see here. :wink:

 

If you think those guys don't take advantage of every bit of data out there then you clearly don't comprehend their level of obsession.