Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

12" White Stickers
BallOfSpray $5 Donation
BallOfSpray $10 Donation

We Have the Technology

taptap Posts: 105 Crazy Baller
edited December 2016 in Technique & Theory
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


  • GloersenGloersen Posts: 1,099 Mega Baller
    edited December 2016
    @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!
  • Mick04Mick04 Posts: 62 Baller
    I would love to see it in trick mode. Actually, with the same skier, but A,B,C & Trick mode overlayed.
  • Jody_SealJody_Seal Posts: 3,301 Mega Baller
    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!
    Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise.

  • dislanddisland Posts: 1,477 Mega Baller
    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.
    Dave Island- Princeton Lakes
  • DWDW Posts: 2,317 Mega Baller
    @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.
  • AdamCordAdamCord Posts: 936 Open or Level 9 Skier
    @scotchipman I believe @adamhcaldwell peaked at about 750lbs at 39...not bad for a 175lb guy!
  • Razorskier1Razorskier1 Posts: 3,425 Mega Baller
    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!
    Jim Ross
  • taptap Posts: 105 Crazy Baller
    @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.
  • HortonHorton Posts: 30,608 Administrator
    @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?

    Support BallOfSpray by supporting the companies that support BallOfSpray

    Barts★ Connelly ★ DBSkis ★ Denali ★ Goode ★ Follow ★ Hobe Lake ★ MasterCraft ★ Masterline ★ 

    McClintock's ★ Performance Ski and Surf ★ Reflex ★ Radar ★ Rodics OffCourseStokes

  • WishWish Posts: 8,269 ★★★Triple Panda Award Recipient ★★★
    edited December 2016
    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.
    >>> 11.25..a different kettle of fish. <<<
  • taptap Posts: 105 Crazy Baller
    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.
Sign In or Register to comment.