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Fin tuning - how can it be so critical?

HortonHorton Posts: 30,230 Administrator
Most short line skiers accept that a fin move of .003” or .005” is enough to make a real performance difference. In my mind, this is especially true of DFT. Most of us accept this to be true but if you step back a second and ask how can this be true it is really seems impossible. I mean how can this be real? Any theories?

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Comments

  • PatMPatM Posts: 788 Crazy Baller
    Higher the speed the more it is affected by small increments? Magnification. At a slower speed the movements are not effective. And by slower speeds I don't mean 30 vs. 34 or 36 mph. I mean 10 - 15 mph. I don't know I bury people for a living.
  • DanoDano Posts: 152 Baller
    edited January 9
    I’m just a hack of a skier spend most of my time [email protected], but here is my experience. I spent last year adjusting my fin. Tried large moves like .1”. And small of .0005 the bigger moves could definitely feel the difference in the way the ski felt, but really had no impact on the buoy count. Front binding adjustments were the single most noticeable and effective way to change the ski’s behaviour. This year I have my boots where I like them already, the fin will be at factory recommended settings and I’m leaving the tools at home so I can focus on just having some fun.
    KRoundyCalisdad57
  • kurtis500kurtis500 Posts: 92 ★★★Triple Panda Award Recipient ★★★
    @horton "Most short line skiers accept that a fin move of .003” or .005” is enough to make a real performance difference. "

    A human hair is .004 and people are saying they can feel that?
    KalebP
  • lpskierlpskier Posts: 3,080 ★★★Triple Panda Award Recipient ★★★
    I’m not agreeing with the width of a hair, but you can definitely feel any .005 fin adjustment.
    John Wilkins- Si non pro sanguine quem ludus ne. #iskiconnelly
  • kurtis500kurtis500 Posts: 92 ★★★Triple Panda Award Recipient ★★★
    edited January 10
    @Horton what measurement or alteration can be moved .004 that goes from well behaving to misbehaving? Is the ultimate tool of measurement ‘feel’?
  • JASJAS Posts: 305 Crazy Baller
    Would be interesting to see what the Adams think about Than’s assumptions and calculations? Would be easy to setup a blind test to evaluate an elite skiers ability to identify fin changes. I think everyone would be interested in results
    Than_Bogan
  • Bruce_ButterfieldBruce_Butterfield Posts: 1,865 Member of the BallOfSpray Hall Of Fame
    @Horton if 0.005” makes the difference between “well-behaving” and “misbehaving” you are on the wrong ski.
    I'm Ancient. WTH do I know?
    Than_BoganghutchReallyGottaSkiMattP
  • kurtis500kurtis500 Posts: 92 ★★★Triple Panda Award Recipient ★★★
    @lpskier what .005 adjustment can you feel? And what other factors do you calculate when making this adjustment.
  • HortonHorton Posts: 30,230 Administrator
    @kurtis500 I guess "feel" is all encompassing so yes but it is about performance that can be measured by ball count.

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  • wettek69wettek69 Posts: 104 Baller
    edited January 10
    Just to throw in a hand grenade, how much is fin adjustment a placebo effect? "The experts say if I move my fin .005 this way, my ski should feel different. Wow, yeah, I can really feel the difference" Sorry guys, and this is just MY OPINION, not being good enough of a skier to need to adjust my fin, I find it hard to believe moving a fin the distance of a human hair can make that much of a difference. Again, this is just MY OPION, so don't flame me for questioning it.
    What next, do we start putting index marks on handles to adjust hand position, or visual spirit levels (preferably filled with gin) on the decks of our skis to adjust hip position 1 degree forward or back?
  • HortonHorton Posts: 30,230 Administrator
    @wettek69 learn to run 35 off or shorter and then tell me it does not matter

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  • kurtis500kurtis500 Posts: 92 ★★★Triple Panda Award Recipient ★★★
    edited January 10
    If a ski adjustment is made at one (air) temperature then thrown into the cooler water at a change of say 25F, what does that do to the fin? Plug in the fin length and area into a CTE calculator. Find both linear and volumetric expansion rates....it’s a set of calculations....scientific calculations.....then see how much of a .002-.004 tolerance is left after just the temperature change. Making an adjustment in the morning versus one made in afternoon heat and thrown in the same water temp will yield another number.

    If a tight tolerance like that is required then why are theses made of aluminum. Aluminum will warp more than most other metals. These factors must have been calculated in somewhere if aluminum is the choice

    @horton maybe rethink the carbon fin just on CTE versus aluminum alone.

    Hmmm
  • kurtis500kurtis500 Posts: 92 ★★★Triple Panda Award Recipient ★★★
    edited January 10
    @the_bogan

    Your number of .01 is 2-3+ times the size of what was brought up. Just mentioning so nobody is confused
  • wettek69wettek69 Posts: 104 Baller
    @horton I did make it quite clear it was MY OPINION only. I was not debating it it, if you reckon you can feel a massive difference with a .005" adjustment, go for your life. You may have a slightly different body position on the day or just be skiing better (or worse) or the .005" might be making the difference.
    I don't need a bad attitude for making a comment.
    Bruce_ButterfieldBuxrus
  • HortonHorton Posts: 30,230 Administrator
    edited January 10
    @wettek69 ok sorry for being grumpy. At shorter ropes, if very small fin movements make a big difference or not is not up for debate. That is the point of the original post. Those of us who have been doing this for years generally accept it to be true but frankly it's bizarre how sensitive fin adjustments are.

    Sensitivity can be different depending on other factors but generally speaking if you take a good setup and you change any dimension by .010" the change is far beyond placebo.

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  • JASJAS Posts: 305 Crazy Baller
    @horton I took @wettek69 comment to allude that with every fin change there is a mind set. Do you think there is a great enough disconnect between these to differentiate between fin change and change in skier impute?
  • wettek69wettek69 Posts: 104 Baller
    @horton No worries mate. As I said, I am far away from needing to adjust my fin, I was merely commenting as an "outside viewer". With the technology in skis these days, I would not have thought .005" adjustment on a fin would be enough to offset the effects of tiny changes to body position, slight change in foot position in a boot due to a sore toe, or even a full belly from breakfast. .005" is .125 of a millimetre, .01", .25 of a millimetre. It really is literally a hair breadth difference. Just the difference in feel different people have on a vernier can be worth a couple of thou either way.
    Cnewbert
  • scokescoke Posts: 704 Crazy Baller
    @wettek69

    Your opinion and position is very curious to me. Could you share more details about your experience?

    What starting speed and line length? What’s your height and weight?

    Thanks mate.
  • The_MSThe_MS Posts: 6,092 Member of the BallOfSpray Hall Of Fame
    Fin adjustments don’t work. If anyone had a new Pineapple 🍍 don’t bother tuning it, just sell it to me
    Shut up and ski
    OTFschafer
  • WayneWayne Posts: 557 Solid Baller
    A few thoughts and questions that this tread provoked. @Horton how do ski manufacturers quantify ski performance? We look at bouy count but some time last year I started to think that bouy count is really an assessment of the skiers ability to use a particular ski.

    Recalling threads I’ve read on this forum I believe skis are more subjectively evaluated for performance that objectively. Bouy count is a byproduct of ski performance, skier ability and environmental conditions. Skier ability and environment conditions are really noise factors that will have an influence on the skis assessment.

    Here me out now, as I’ve been trying to develop something for a while and I’m kind of stuck so it just sits in the back of my head. In the automotive industry we’ve been able to objectively assess vehicle performance since the car was invented. 0-60 MPH, cornering acceleration, fuel economy and so on are objective measures. However it been only over the last 10-15 years we’ve had methods to assess driveability objectively. For years engineers provided an “expert opinion” on a 0-10 scale of how certain driving events felt. Across the industry most experienced engineers would have subjective ratings for the same event that were with in a half a point of each other if they evaluated things independently. I think the same holds true for skis but we’re stuck in assessing things subjectively and using a byproduct of the actual ski performance (bouy count) as the measure.

    So what objective things can we measure to assess the performance of a ski? I really feel this would give evidence on how small, or large, adjustment increments should be and it would tell us if a ski is overly sensitive to a particular adjustment.

    PS for all I know ski manufacturers are already doing this and just keeping it a secret. I’ve really been interested in being able to put measurement devices on a ski and capture real time data. I’m just not sure what all would be useful or practical for the budgets of a ski company let alone the average skier.
    Than_BoganCnewbertDaveD
  • HortonHorton Posts: 30,230 Administrator
    edited January 10
    saying fin settings are not critical is like saying...


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  • wawaskrwawaskr Posts: 327 Crazy Baller
    And of course all this discussion is assuming the bio-mass on top of the ski repeats all the physical positioning and movements identically the same each ride - correct?
    Matt
  • Than_BoganThan_Bogan Posts: 6,877 Mega Baller
    @wawaskr Not sure if that was sarcasm, but of course not. Humans have terrible repeatability. That is independent of whether they can feel small forces.
    Nathaniel Bogan -- GUT Padawan
    Horton
  • HortonHorton Posts: 30,230 Administrator
    edited January 11
    @wawaskr No the skier is always a factor.

    For any ski, fin & bindings combination the ideal setup compensates for some amount of skier inconsistencies and inadequacies. Every skiers is going to have a different mix of inconsistencies and inadequacies. That is why two skiers on the same ski with similar high scores may run different settings. That is also why the settings a Pro skier uses is often far from ideal for a lesser skier.

    On the other hand an experienced skier knows or should know when they have executed "good enough" to expect the ski to do certain things. Experience means you know your level of inconsistencies and inadequacies. If you execute the way you think you should and the ski does something unexpected then either your expectations are misplaced or the ski is set up wrong.

    As an example: In my case I expect to be able to consistently turn off side and be in a strong position to the wakes. If ski is does bad things ( loose tail, tip rise, slow finish, whatever ) at apex of off side I am getting out the tools. On the other hand if I am struggling at On Side the spot light is on my skills first because that is where my I need the most technical work.

    To put it more simply - if I can not run my opening pass ( 32 off ) early and easy almost every time then something is wrong. That is the first place I will judge a ski and set up. It is not pass where the more minuscule issue arise but is a good starting place. When 32s are perfect I will work at 35 until it feels the way I want.

    So is the skier an inconsistent factor? Yes but with experience that accounted for.

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    Than_BoganDanothagerskialex
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