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Flextail: Uneducated ramblings

Than_BoganThan_Bogan Posts: 6,436 Mega Baller
edited June 2015 in Skis Fins Bindings
I'm quite intrigued by the flextail, in part because there's a little bit of a forehead slap here of "how did I not even think of that!"

As is typical with proprietary engineering, the published information doesn't really say a lot about WHY it works. So I am left to MSU (make shit up).

I think I understand one part fairly well, so I'll start there: While in the actively turning phase, the force acting on your ski points roughly inward toward the centerline. Thus the tail flexes inward, which causes it to more resemble the very arc you are trying to make. It seems borderline obvious that such a shape will turn "better" in some way, whether it's holding better or a tighter radius or maybe both. Fwiw, this is a lot like what a fish looks like making a fast turn. (I can see why Fishtail wasn't the name of choice, however...)

Next, let me move back to the preturn phase. At this point, especially on a short line, the force acting on the ski is pretty close to straight down the ski. That means that the tail isn't flexing much. So during this phase this feature seem to be "off," which is totally fine.

Finally, there's what it does when making your way across the wakes. Here I find myself a bit confused. I DO get the fact that this ski can be longer than "normal," because of the turn-radius improvement. So that is a help in holding a good angle. Maybe that's all we're getting during this phase (and that's still great). But as far as the flextail itself goes, it will be flexing away from the boat. Is that what we want? Or is it more like that doesn't matter much because we're using the whole ski against the water and the fin is not terribly important? I think the latter might be true because when we think fin adjustments we almost never talk about what is happening behind the boat: the fin seems much less important at that stage.

One thing that seems plausible is that the flexed fin is effectively asking the ski to add angle. I.e. if you are going from even to odd, it is trying to turn to its right. I can't decide if that would be a good thing or a bad thing?

Anybody actually know anything they can share -- or care to join me in wild uninformed speculation!?
Nathaniel Bogan -- GUT Padawan
Ed_Johnsonandjules
«13

Comments

  • addkerraddkerr Posts: 170 Baller
    Its cold and windy so I shall join the ramblings :).

    @Than_Bogan, you say that behind the boat the tail will be flexing away.

    In Goode's words:
    "The Flextail also features an integrated finbox that serves as an extension of the backbone, increasing strength and responsiveness."

    With this rigid backbone, surely there will be no flex or little behind the boat flexing away. Acting like the tails we are used to?

    Unless I have completely misunderstood you haha
  • Chef23Chef23 Posts: 5,957 Mega Baller
    Just from the title I knew this was going to be a @Than_Bogan post.
    Mark Shaffer
    Than_BoganAndreandjules
  • Than_BoganThan_Bogan Posts: 6,436 Mega Baller
    edited June 2015
    @addkerr What is different behind the boat vs. in the turn? (That's a serious question not some debate tactic.) In each case there should be plenty of force on the ski/fin in the lateral (left-right of ski) direction, and the flextail flexes in the same way that a fish's tail does, so I'd expect it to flex when the force is across the ski like that.

    I guess the ski is rolled up on edge behind the boat, so to a certain extent the force I'm talking about is trying to push the tail "up," which would be resisted by the backbone. But isn't that true in the turn as well? In fact, from watching video, it's always a little surprising how little the ski is truly on edge behind the boat.
    Nathaniel Bogan -- GUT Padawan
  • addkerraddkerr Posts: 170 Baller
    @Than_Bogan
    I understand now, yes so as the ski is going across course with the flex of the tail acting like a rudder of some sort, steering the nose of the ski more before the buoy in theory, so more angle?

    One question I do have is does this flex happen to a max point constantly or is it reactive to what the skier inputs?

    This ski sounds more sophisticated than I first imagined.
    ToddL
  • klindyklindy Posts: 2,280 Mega Baller
    @Than_Bogan your assumption (if I understand it correctly) about the tail flexing the same in either the lateral (left-right) direction or longitudinal (up-down) direction would be true if the 'backbone' is equally strong in both directions and the forces are the same. I don't know about the forces on the ski but the backbone is much 'taller' than it is 'wide' so flexing laterally would be much easier with the more narrow dimension of the backbone and the cuts in the tail if the ski. Even though the effective cross section of the is very small in the 'cut' section, the backbone is quite tall so longitudinal flex (creating more rocker) seems fairly minimal.
    Keith Lindemulder
    AWSA Vice President
    AWSA Southern Region EVP
  • gregygregy Posts: 2,581 Mega Baller
    @Than_Bogan I think across the wake it goes back to @gator1 idea. "There are TWO angles of attack of ski to water." the ski twisting allows it to lift.

    The discussion from last year.
    http://www.ballofspray.com/forum#/discussion/11368/ski-roll-angle-more-not-necessarily-better/p1
  • Than_BoganThan_Bogan Posts: 6,436 Mega Baller
    I don't see any feature of the Flextail that allows twisting or rocker flex. I would expect the ribs to only allow extra left-right fish-tail style flexing.

    Or maybe I'm not getting it at all!
    Nathaniel Bogan -- GUT Padawan
    ToddL
  • GloersenGloersen Posts: 908 Crazy Baller
    edited June 2015
    add rule 8.03 C to your consternation; is the fin fixed or does it by design intentionally move?

    Of course innovation in some instances should outweigh archaic rules.
  • ozskiozski Posts: 1,651
    Give it a year or two and we will be able to tell the spin from the real "on the water" benefits...
    'Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.'' Boat 2005 Nautique 196 6L ZO - Ski - KD Platinum

  • DefectiveDaveDefectiveDave Posts: 479 Solid Baller
    The flextail seems like a good idea to me. Given the @Than_Bogan comment about the fish-tail type nature of the ski (which seems spot on) the ski should be in a more efficient shape when making a turn. So it's pretty intuitive how that would benefit the skier in the turn.

    With respect to how it could be beneficial in the cross-course phase, I think the concept should be just as valid. The reason being that you are never really traveling a "straight line", but are in fact accelerating and following a curved path through the water heading towards centerline. Granted it's not as extreme of a curve as the turn itself, but those slots are only 1mm wide and they can only allow so much lateral flex before the flex becomes structurally constrained.

    I have no idea how big of a difference this should make, but it's an interesting concept. I think there is a lot of similarity (with respect to what they are trying to accomplish) to the D3 RockerBlock and Mapple Torque skies. Time will tell and I'm interested in seeing the results.
    Than_BoganSkoot1123
  • klindyklindy Posts: 2,280 Mega Baller
    Than_Bogan if you cut 3 slots on each side of your ski between the back binding and the fin to within 3/4" of so of the centerline of the ski do you think the tail would twist or add rocker under load?

    Granted the "backbone" should eliminate that or certainly reduce it but the mechanics of the smaller cross section of the ski certainly changes the dynamics of how the tail of the ski can flex from the forebody. If adjusting the fin to 0.001 of an inch "makes a difference" so does this ski design.

    It's innovation for sure! I'm not suggesting it's good or bad...just likely different!
    Keith Lindemulder
    AWSA Vice President
    AWSA Southern Region EVP
    Than_Bogan
  • Than_BoganThan_Bogan Posts: 6,436 Mega Baller
    @Gloerson I don't think that rule is a concern. It specifically refers to stuff attached to the fin being able to move, not the ski flexing under load. Indeed, every ski ever made has flexed under load, so that is implicitly legal. I'd only be concerned if there were a rule that specifically stated ranges of legal flex vs. load in certain directions.

    @ozski True, of course, but then again in two years this ski will be nearly obsolete anyhow. But more importantly, in engineering it's always great if you have an idea WHY the tech works so that you can draw those things forward into the next design. So I'm just naturally curious about the why part.

    @DefectiveDave Very interesting point. But I also think there are times when your path is fairly straight and yet the forces across the ski are very high. But now I'm a little confused and need to ponder the physics a bit. If the path is (briefly) straight, then is it necessarily the case that there is no net force acting across the ski?? That sounds both obviously right and obviously wrong...
    Nathaniel Bogan -- GUT Padawan
  • HortonHorton Posts: 27,615 Administrator
    edited June 2015
    I am not in the inner circle at Goode but I have pretty solid spies. Last I heard the ski is torsionally very stiff at the tail. The tail “rudders” but does not twist. There is enough strength torsionally and longitudinally around the centerline of the ski so that the only major effect of the 6 cuts in the ski is to allow the tail to move side to side.

    Nickname for the ski I heard today "fishbone" => also not from the Goode inner circle
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  • GOODESkierGOODESkier Posts: 1,107 Crazy Baller
    edited June 2015
    @Than_Bogan the one I skied this winter (65.25") felt a lot like my bigger ski behind the boat (fast-stable-easy-early). And like a little ski in the turn (agile-easy-smooth-little resistance). I normally have to work harder on a 65.25 ski to get down the rope and have been skiing a 66.75" XT, not the case on the flex tail. I would say I ran my cleanest 32 and 35 on the ski during the off season for me.

    I will let the people at GOODE explain the changes in rocker and flex in this ski just so I don't get that info out incorrectly. In my head, the advent of the flex tail allows us, the skier, to capitalize on characteristics in flex and rocker that we couldn't before, due to the new flex tail aiding in the turning of the ski and reducing effort. I relate this to snowmobile trail riding, when Yamaha introduced power steering. That was a game changer as it allowed engineers to design a front suspension that was extremely efficient and active, but would have been terribly difficult to steer without their new power steering system. It really does ski amazingly well.

    It was neat being in on the ground level seeing the ski go thru many proto-type phases and hearing the why of each change/modification. Dave Goode is truly the engineer, manufacturer, tester, marketer, etc...... for his company. He spends many long nights building molds and skis so the ski can be ready for testing at the lake. He is one hard working guy from concept to market.

    I am excited to see my 66.5" Flex Tail in a few days. @Horton I am calling mine the "Flexy Thing"....... not an inner circle GOODE name either, but the names that were tossed around were pretty fun at times!
    2003 Nautique 196 LE Star Gazer & ZBox - GOODE NANO OneXT 66.75" - Powershell 5 (LFF) - Tournament PB: 2 Balls @ 39.5' OFF (34.2 MPH) on 7/18/2015 at BIG DAWG BROHO!
  • gregygregy Posts: 2,581 Mega Baller
    edited June 2015
    There so little ski left in the area of the 6 cuts its hard to believe that they could be as stiff as a regular ski torsionally. I wonder how much the 6 slots have to do with the turning of the ski - equalizing or relieving pressure on the tail maybe so it can come around. Like holes in the fin.
    Than_Bogan
  • ALPJrALPJr Posts: 1,861 Mega Baller
    If my memory serves me well... I recall a ski in the late 70's that had slots cut in the tail between the rear toe and fin. Possibly a Cypress Gardens.
  • Chef23Chef23 Posts: 5,957 Mega Baller
    @scotchipman if Goode is measuring material length along the bottom their skis are going to run shorter than past Goode's. 66" measure cord length is longer than 66" measured material length.
    Mark Shaffer
    supersonicus
  • DefectiveDaveDefectiveDave Posts: 479 Solid Baller
    edited June 2015
    @Than_Bogan,

    In the case where the path is briefly straight, I would argue that it is not necessary that there is no net force acting across the ski. If there is indeed no acceleration, then it would only be required that the net forces on the skier be zero. So for a spherical skier in a vacuum, the sum of the force vectors from the ski and the rope would be zero, hence no total net force for the system.

    Taking it a little further, the case where there is no net force is a trivial subset of the possible solutions in which a skier is traveling in a straight line. The solution space actually includes all scenarios where the force vector aligns with the direction in which the skier is traveling. I tried to resolve this mathematically to bound those scenarios but reached a brick wall guarded by gorillas.

    It is definitely possible to ski in a straight line during the cross-course phase, but I can't yet determine if it is probable. The world may never know.
    Than_Bogan
  • ozskiozski Posts: 1,651
    The option to plug those gaps on one side or another for offside / onside tune does have some appeal for me...
    'Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.'' Boat 2005 Nautique 196 6L ZO - Ski - KD Platinum

  • buskibuski Posts: 114 Baller
    "People will even notice less spray coming from the ski in the turn."

    Seems like a junk ski?
  • WishWish Posts: 7,795 ★★★Triple Panda Award Recipient ★★★
    edited June 2015
    I'm trying to visually think how this flex would work. I can't get away from this visual. Is this the idea? Or is it flexing in the opposite direction?


    >>> 11.25..a different kettle of fish. <<<
  • Than_BoganThan_Bogan Posts: 6,436 Mega Baller
    @wish I don't quite understand your drawing. Where is this view from and what part of the course? If this is an overhead view of someone turning 1/3/5 then I believe the flex you show is correct. But in that case the blue line confuses me.
    Nathaniel Bogan -- GUT Padawan
  • 94009400 Posts: 604 Crazy Baller
    Based on @Wish's sketch. The flex allows the tail to not ride so deep in the water, therefore reducing drag??? Am I close?
  • GOODESkierGOODESkier Posts: 1,107 Crazy Baller
    Best explanation is to get one and ski.........
    2003 Nautique 196 LE Star Gazer & ZBox - GOODE NANO OneXT 66.75" - Powershell 5 (LFF) - Tournament PB: 2 Balls @ 39.5' OFF (34.2 MPH) on 7/18/2015 at BIG DAWG BROHO!
    [Deleted User]
  • klindyklindy Posts: 2,280 Mega Baller
    edited June 2015
    The mechanics of a rigidly mounted fin on the tail of the ski means the tail will want to track straight (the path of the ski). Since your "driving" the fire body of the ski with your weight, edges and rocker, etc. it will start a change of direction. So the tail (allowed) to flex left/right will tend to follow like a trailer does behind a car/truck. That has the effect of making the turning radius tighter.

    Of course that ignores some hydrodynamic stuff and other physics but generally correct
    Keith Lindemulder
    AWSA Vice President
    AWSA Southern Region EVP
  • Ed_JohnsonEd_Johnson Posts: 2,109
    edited June 2015
    If you saw CP's turns, there sure was no Lack of Spray.....Can't wait to ski it !!!!

    Although, I did bite on all the hype on the Nano "Twist," got one of the first one of those, and that Damn thing nearly KILLED me.
    Special Thanks to Performance Ski and Surf and the Denali Adam's !!!
  • WishWish Posts: 7,795 ★★★Triple Panda Award Recipient ★★★
    edited June 2015
    @Than_Bogan your geek status just dropped a pinch. ;-) Pic is of ski in water on high edge ...side view.. Take you pick on where in the course.
    >>> 11.25..a different kettle of fish. <<<
  • HortonHorton Posts: 27,615 Administrator
    @wish art school?
    Looking for a healthy snack? Try SuperFat

    Support BallOfSpray by supporting the companies that support BallOfSpray

    Barts ★ Connelly ★  DBSkis ★ Goode ★ Hobe Lake ★ HO Syndicate 

    MasterCraft ★ Masterline ★ MOB ★ Performance Ski and Surf ★ Reflex ★ Radar ★ Stokes

    [Deleted User]MattPTexas6
  • WishWish Posts: 7,795 ★★★Triple Panda Award Recipient ★★★
    edited June 2015
    @Horton phone, fat finger, an app called Doodle Buddy and done in less then a minute. All that considered it's a damn good drawing. :)
    >>> 11.25..a different kettle of fish. <<<
    Ed_Johnson
  • WishWish Posts: 7,795 ★★★Triple Panda Award Recipient ★★★
    @OB ... The T1-2 box I get. The cuts all the way through a ski....not so much.
    >>> 11.25..a different kettle of fish. <<<
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