Fin Shape

NandoNando Posts: 439 Crazy Baller
When I took my boat to storage, I looked around at a few others and considered how much tracking fin and rudder shapes have evolved over the last several years. Conversely, the shape of the fins on our skis has changed very little. In the 80s, I tested a bunch of different shaped fins for EP and we never really found an improvement over their standard "modified D" shape. Around that time, Connelly shipped their skis with the "tournament fin". After my first set on a new Connelly, I always replaced that thing with a standard fin, with great improvement in performance (and they sent me a stock of the "regular" fins and metal, rather than plastic, wings that were a significantly different shape). Others have come up with fin designs over the years (remember EP's tubular wing? cutouts on the trailing edge? the flat-bottomed Maha and Saucier fins way back when, and, of course, carbon fins, but we're talking shape, not materials here), but nothing seems to be an improvement that gets adopted.

Anyway, my question is, is there performance to be unlocked with new fin shapes? Maybe something really radical like the keels of America's Cup boats? We spend so much time tweaking our existing fins to .001s of an inch, is there a more fundamental change that could be a significant improvement?


  • Than_BoganThan_Bogan Posts: 6,053 Mega Baller
    Adam Caldwell has a massive pile of Crazy Ass Fin Shapes that he has tried. I'll leave it to him if he wants to comment on whether any of them are any good.
    Nathaniel Bogan -- GUT Padawan
  • HortonHorton Posts: 25,801 Administrator
    @Than_Bogan just another hoax

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  • NandoNando Posts: 439 Crazy Baller
    The question was mainly intended to get Adam (or one of the other techies on the site) to weigh in. Wonder if he has anything as weird as my short fin with a 0.75" tube in place of a wing that I had a bike mechanic weld up. I was young and stupid and had no idea if it would work- I just wanted to try something different. At least I didn't hurt myself...
  • A_BA_B Posts: 4,003 Mega Baller
    I cut a bunch of differing shapes from sheet aluminum years ago. Tried to find the right amount of straight edge in the back and curve on the leading edge. Seemed to always gravitate back to a standard fin shape. About the weirdest fin I used was a thing we called the Whale Tail. Had an extension behind the normalish looking fin that was a just an added square section with a wing way back on it. Held a ton of angle. Think I have it laying around somewhere. Gold color.

    My thought is that Kris Lapoint has probably tried about everything under the sun, and if he ain't using it, no one else would either.
  • adamhcaldwelladamhcaldwell Posts: 432 Open or 55K Rated Skier
    My personal favorite was one that I never actually never rode....surprisingly, it was a wise decisions to only witness it in action from the rear-view. I think @AdamCord is still suffering the consequences of that one.
  • Bruce_ButterfieldBruce_Butterfield Posts: 1,330 Mega Baller
    Yes, there is a lot to be learned from fin shapes. Its actually very surprising that we notice a few thousands of movement, but when making very significant changes in shape, the results can be subtle.

    I've tried many different shapes and its all trial and error to get something to work, and it can take a long time to really figured it out. One of the better examples is that I used a slot fin for half a season a number of years ago. I loved the way it made the ski turn like it was on rails, but it took several months before I realized that I just wasn't as consistent on it as a regular fin.

    Probably one of the better "alternate" fins is known as the AMF. Its more triangular with a straight back and more holes in the leading edge. It is typically run forward, short and deep. It helps keep the tip down and the completion of the turn on both sides.

    The thing to keep in mind is that a particular fin shape may work better on a particular ski or for a particular skier.
    If it was easy, they would call it wakeboarding.
  • DWDW Posts: 1,863 Mega Baller
    Another reason for potential lack of optimization is that trial and error is the methodology used to develop the shape and is not only dependent on ski design but also influenced by the skier. Engineering tools to aid in the development process are not only costly but also not mature or very available. Examples would be CFD analysis and for the marine or multi medium environment (water and air) are not really very well refined yet and available water tunnels are not really that available and most would require scaled down versions for analysis.

    Interestingly, many times a first or early attempt at optimization hits the 95% mark early in the cycle and then the other 5% ends up being a litany of small trail and error attempts. Humans are very good at coming up with good solutions for mechanical things very quickly.

    In other words, keep trying and have fun doing it.
  • HortonHorton Posts: 25,801 Administrator
    I have made over a thousand fins.... a few hundred by hand. Interesting thing about the standard shapes - they are sort of organic. The curves are compound but simple. They are easy to recreate freehand. I have always assumed that they originally evolved from a shape that was just easy to make.

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  • eleeskieleeski Posts: 3,655 MM Trick Skier / Eccentric Person
    There have been many wild fins. Some specific fin mods have worked quite well on specific skis. It's like tuning the ski by fin selection (more effective than .001 movements). But not every wild fin works with every ski. The stock fin is a good starting point. Enjoy the experiment.

    One interesting aspect of fins is the flex. @Horton 's carbon fins were fairly conventional in shape but very different in flex (at least the one I liked best). I carried that to an extreme and made a nearly floppy fin. Felt great but didn't make buoys well. Again, fin flex is something to tune with consideration to the ski and the skier.

    There is the "exotic fin du jour" popularity trend. Schnitz fins, backwards fins, Pac Man fins, Donatt's big hole fin (the current fave around socal) and many others have gotten their 15 minutes of fame. Valid small improvements but still "it's the skier, not the ski".

    The only fin mod that has stood the test of time is the wing.

  • HortonHorton Posts: 25,801 Administrator
    @eleeski you should flex a Pac-Man super. soft flex

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  • BRYBRY Posts: 578 Crazy Baller
    edited December 2015
    @nando There is this Schnitz guy who knows a little about fins Pretty sure he was working with various wings long before Australia II in 1983. He has various shapes and multiple wings for sale.
    Chet Raley has also played with fins/wings I have seen Chet put some really whack wing configurations on his ski and still go deep 39 or run it.
    I bring these guys up as you can go buy their stuff currently. Too many to name for so many years have tested shapes and appendages (wings, tubes, ect) yet seem to come back to the standard shape. Additional fins like anti-drift fins and side force enhancers never seemed to catch on. Schnitz and Chet are in Palm Beach County, and KLP a couple hours up the road in Orlando. Hop a plane, take a lesson from each and they can give you all kinds of fin info.
  • JordanJordan Posts: 1,027 ★★★Triple Panda Award Recipient ★★★
    The funny thing about fins is that so many skis are essentially built/designed with a conventional fin.

    If you take an existing ski, start filing bevels and adding and shaping bondo etc. until it skis great, then make a mold from that. It's no surprise that the new ski works best with a conventional fin.

    There might be some crazy fin design that could go with a crazy ski design and together they are better than anything previously thought of....but how do you get there?
  • ToddLToddL Posts: 2,733 Mega Baller
    Let's say that Brand "X" comes out with the new Schnizzle Ski with the new Fizzizle Fin that is radically differently shaped but somehow optimized/balanced for that new ski design. Their stock numbers would be for that fin on that ski only. OK, so no biggie.

    But if the sport ended up with the Fizzizle as a second universally-accepted fin shape that is different from the traditional fin shape, then I'd assume ski stock numbers would not apply to that fin. If this new universally-accepted fin grew in popularity, then ski manufacturers might have to publish two sets of "stock" numbers. "Are those the standard fin stock numbers or the Fizzizle fin stock numbers?"

    Heck @SkiJay might even have to write a new edition to his book because likely the fin tuning actions might not apply in the same way to a different fin shape.
    -- The future of skiing depends upon welcoming novice skiers regardless of age to our sport.
  • SkiJaySkiJay Posts: 2,232 Mega Baller
    Actually, @ToddL, when a different shaped fin is used, the numbers change, but same principles still apply. Creative shapes can often work quite well, but they're usually less versatile. I have a drawer full of different fins, and for what it's worth, I think the "standard" fin is as popular as it is because it's seemingly dated design is actually a stroke of genius.

    Not only does it allow us to adjust it in any conceivable combination of longer, shorter, deeper, shallower, forward, and back—it can do all of this without changing its basic shape. It's ability to retain its basic shape is what allows us to adjust one fin-related behavior without affecting the others at the same time. The current fin is sheer brilliance in its simplicity, predictability, and versatility. ... Your ski should be your dance partner, not a wrestling opponent
  • DragoDrago Posts: 1,258 Mega Baller

    None of these changed my life ('cept for that black one on the left when the magnet changed its leading edge shape , and the stainless one that fell out of the fin box as I went through the wake (re-entered the world on the shoreline after my rag doll gingerbread man impersonation). Never tried the Klem fin.
    *always video testing of new fin shapes
    SR SL Judge & Driver (“a driver who is super late on the wheel and is out of sync”)
  • MSMS Posts: 4,926 Mega Baller
    I think someone should start up a new fin company, maybe introduce some carbon into them.
    Shut up and ski
  • NandoNando Posts: 439 Crazy Baller
    MS, that sounds like a money-making opportunity for the right individual...
  • mmosley899mmosley899 Posts: 524 Water Ski Industry Professional
    @Drago I think I have all those shapes too!
    Mike's Overall Binding
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  • MattPMattP Posts: 5,973 Mega Baller
    @MS are you trying to send @Horton into a psychotic flashback?
  • thagerthager Posts: 4,318 Mega Baller
    @MattP It could only help!!
    Stir vigorously then leave!
  • adamhcaldwelladamhcaldwell Posts: 432 Open or 55K Rated Skier
    edited December 2015
    Years ago I pulled @AdamCord into 38 on this fine specimen.

    @Drago, Not sure about you, but my consensus on multiple stainless steel fin shapes and thicknesses = horrible.
    Craig Aitkenmbabiash
  • CsSkisCsSkis Posts: 107 Baller
    @adamcaldwell I think that I am guilty for putting that thought into @AdamCord's head. I had cautioned him that the edge change might be a little "aggressive" and the drag might be a little higher. However, I had been hoping that after some R&D that the fin could be reduced in total area (relative to current fins) and that by rotating the tip of the fin foreward or aftward would allow for tuning tip/tail. Basically, you wouldn't have DFT, depth and length adjustments, only fin rotation angle.

    In this case, as shown in the picture, I would imagine that the ski preferred to go straight. However, I never heard the rest of the story. Only that he "survived" the experience. Any more to the story/experience?
    Chuck Illi
  • AdamCordAdamCord Posts: 613 Open or 55K Rated Skier
    @CsSkis I think that fin actually ripped the fin block off of the ski, and possibly also cracked the ski. Not for the faint of heart :#
  • CsSkisCsSkis Posts: 107 Baller
    @AdamCord Yikes! I guess that I am glad that you are still speaking to me!!
    Chuck Illi
  • DragoDrago Posts: 1,258 Mega Baller
    I thought it was all about total surface area? @adamhcaldwell , the Mapple shape on my Stiletto/ schnitz very-stiletto-like shape worked decently.not so much on anything after that.
    SR SL Judge & Driver (“a driver who is super late on the wheel and is out of sync”)
  • KRoundyKRoundy Posts: 196 Baller
    I think the reason things have stayed the same for so long is inferred in the story above. Hydrodynamic forces can be incredibly powerful. The current shape is essentially the most surface area that humans and our equipment can handle. Anything larger would just tear stuff apart and anything smaller will turn the slalom ski into a weird-looking trick ski. SkiJay makes a great comment too about the adaptability of the design. (Still hopeful that my book comes soon, I can't wait for it to appear in my mailbox!)
  • DragoDrago Posts: 1,258 Mega Baller
    @adamhcaldwell I'm glad I sparked that tangent.great stuff.
    Every heard a big guy say their should just be one setting?
    To digress, I recall a certain boat, that has since been completely redesigned: everyone though it was a "beast", super powerful, so they tried to detune it with a softer ZO setting. I always felt that they were going the wrong direction , because the prop was slipping something awful, especially when the owners also tried to detune it with a (non-approved) "softer " prop.
    Also explains why that stainless fin worked on my Stealth and Stilettos.
    SR SL Judge & Driver (“a driver who is super late on the wheel and is out of sync”)
  • thagerthager Posts: 4,318 Mega Baller
    In 80s I bought a Mastercraft Pro without a fin. Found a normal shaped aluminum fin that I cut the back 1 1/2 inches off squaring it off to imitate the original. Fin was short and deep. Ski was one of the most consistent turning skis I ever owned. Many PB's on it.
    Stir vigorously then leave!
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