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Why do fins have holes?

HortonHorton Posts: 28,921 Administrator
edited December 2014 in Skis Fins Bindings
I was asked this yesterday & gave the same answer I was given 20 years ago. That answer is that the holes are pressure relief from the high to low pressure sides of the fin. Is there a better answer?

@AdamCord‌
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Tagged:
Lovell
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Comments

  • bowtybowty Posts: 75 Baller
    @Horton‌ wing mounting maybe?
    doonez
  • HortonHorton Posts: 28,921 Administrator
    @bowty‌ I am pretty sure there is more to it than that.
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    bowty
  • Than_BoganThan_Bogan Posts: 6,605 Mega Baller
    Always assumed it was for making Holy Water.
    Nathaniel Bogan -- GUT Padawan
    SBFL
  • LovellLovell Posts: 101 Baller
    I don't know, but one of my old kidder's I had as a teenager (1988) had a fin with no holes and a wing. The fin had a triangular shape, every ski before or after has had holes in the fin.

    I used that ski through 22 off and never had any performance issues.
  • lpskierlpskier Posts: 2,715 Mega Baller
    I remember when holes first appeared in the early 70s. Skis were still made of wood and fins were still screw on rather than drop through. If two holes were good, ten were better. Some fins looked like Swiss cheese. Most holes were between 1/4 and 3/8ths of an inch.

    An equally interesting question is "What is the origin of the holes in the fin?" The story that I heard at the time was that Bab Mahar from Maharajah skis received a shipment of fins at his shop. He looked around for a place to store them, but found none. So he drilled a hole in each fin so he could hang them on a nail on the wall. He then discovered that the skis with the holes worked better than the skis without the holes. True or false?

    WIngs came way after holes in the fin.
    John Wilkins- Si non pro sanguine quem ludus ne. #iskiconnelly
  • dchristmandchristman Posts: 1,106 Mega Baller
    edited December 2014
    A blurry picture from a 1977 book claiming the holes are for pressure relief:



    Interesting that Joel McClintock doesn't even mention fins in his book from 1980.

    Like @Lovell‌ I also used a Connelly "Tournament" fin with wing and no holes in the early 80's. It was an aftermarket item - the ski came standard with a fin with holes. Did it make a difference? It's too long ago for me to remember if I even compared them.
    Is it time to ski, yet?
  • mwetskiermwetskier Posts: 1,337 Mega Baller
    steve schnitz has studied a lot about this in terms of what the holes do and how number and size of holes affect the turn. most interesting to me is he says that altering individual holes can change different aspects of the turn depending on where those holes are on the fin.
  • lpskierlpskier Posts: 2,715 Mega Baller
    @Taperflex Ha! The Swiss cheese skis I am referring to were Taperflexes.
    John Wilkins- Si non pro sanguine quem ludus ne. #iskiconnelly
  • ozskiozski Posts: 1,678
    There is some talk that adjustable holes are on the way.
    'Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.'' Boat 2005 Nautique 196 6L ZO - Ski - KD Platinum

  • mwetskiermwetskier Posts: 1,337 Mega Baller
    @qzski -thats a misnomer. the holes them selves will not be adjustable the fin itself will be adjustable around the holes.
    Horton
  • thagerthager Posts: 4,866 Mega Baller
    Sphincter Fins?
    Stir vigorously then leave!
    Horton
  • eleeskieleeski Posts: 3,975 Infinite Pandas
    Why not?

    Start with a blank fin, add holes for as long as the performance improves. Forget about the why, just ski with the most comfortable fin.

    Analyze fin holes during the winter on the internet far from real skiing. Should I put holes in the bases of my snow skis?

    Eric
  • DirtDirt Posts: 1,625 Open or 55K Rated Skier
    I added an extra hole in the back of my A2 fin. It let the ski come/slide around better but did not track across the wakes/hold angle as well. It definitely makes a difference.
    I learned everything I know not to do from Horton
  • bassfooterbassfooter Posts: 159 Baller
    @eleeski‌ - Some downhill skis have a hole in the tip. For climbing skins? Anyway, with as little snow as Mammoth and Tahoe have right now, you can put holes in your bases just by skiing on them.
  • eleeskieleeski Posts: 3,975 Infinite Pandas
    @bassfooter‌ Yeah, my skis are in getting tuned tonight from the rock damage and need for edges on the Tahoe boilerplate that is everywhere at Squaw. Nothing worth hiking for yet. Pray for snow.

    Fins are important for ski performance. Holes are just one aspect of fins. Flex matters too. And fin placement - but .001 isn't ever relevant.

    Eric
  • HortonHorton Posts: 28,921 Administrator
    Chet can't long in - my fault not his. He emailed me the below post

    Hey John
    On your site people were wondering about holes in fins.
    A few years ago a friend of mine did me a favor and used some sort of metal bondo to fill in the holes on my 3 of my favorite fins (all identical).
    I was excited to ride the ski without the holes to draw my own conclusions.
    First set ...first pass I almost did a trick ski like side slide.
    As you would suspect I began to knock out one hole at a time.
    Each time the ski slid less and tracked out of the buoy better.
    As I remember the rear fin holes were the most critical to performance.
    Cool experiment but for now I like holes.
    Too many can really slow a ski down in contrast (increased drag).
    But slip or tail slide diminishes with increased holes.
    Hope this helps.
    Chet
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  • Than_BoganThan_Bogan Posts: 6,605 Mega Baller
    I am FAR FAR from an expert on fluid dynamics, but Chet's experience seems to confirm something that I was thinking: I don't think there is a lot of water passing through those holes. If it were about that, then we'd expect adding holes to cause more side-slide, whereas Chet found the exact opposite.

    I suspect the holes have a lot more to do with disrupting the laminar flow in some way that ends up being beneficial. To state it VERY imprecisely, they may give you some "grip" on the water.

    Iirc, Gator1's "crazy" fin grooves were directed toward disrupting laminar flow in a particular way, and I wouldn't be surprised if ultimately some carefully placed grooves are "better" than holes. (Nor would I be surprised if we actually want all of the above.)

    As usual: Theory is required to narrow down what is worth trying (since we have infinite possibilities but not infinite time). But only trying it can tell you if it works.
    Nathaniel Bogan -- GUT Padawan
    Wish
  • DWDW Posts: 2,129 Mega Baller
    Pressure relief as JTH noted and they generate some beneficial turbulence as Chet noted. Somewhat similar to vortex generators on a wing or surface and like feathers on a bird wing. The holes also allow the fin to move the leverage center deeper as an example to improve the tail blow out without the detrimental effects of a too deep fin depth.
  • estromestrom Posts: 512 Baller
    Back in the early-mid '80's, my buddy had Connelly's top ski, the HP, (which is what Mike Kjellander used at the time) that had no holes. It also had an odd shape to it.
  • 6balls6balls Posts: 5,338 ★★★Triple Panda Award Recipient ★★★
    @DW is on it if a foil through water shares properties with a foil through air (aircraft wing).

    In the air a turbulent boundary layer over the wing is less likely to separate from the wing than a laminar boundary layer. Thus adding vortex generators keeps turbulent flow over the wing, and hence control, in situations where it would separate otherwise...such as high angles of attack to the relative wind. Separation creates loss of airfoil control followed by aerodynamic stall (loss of lift).

    Would make sense that filling fin holes as Chet did would create a more laminar flow which is more likely to separate at high angles of attack causing loss of control and hydrodynamic stall.

    Could be full of baloney I'm no expert...just happen to have vortex generators on the Mooney and I know how they work and also the before/after story in flying it both ways.
    Dave Ross--die cancer die
    Than_Bogan
  • WishWish Posts: 8,004 ★★★Triple Panda Award Recipient ★★★
    I have an 80s HO Mach 1 - no holes.
    >>> 11.25..a different kettle of fish. <<<
  • dchristmandchristman Posts: 1,106 Mega Baller
    80's Connelly Tournament Fin. The holes are for the wing.

    Is it time to ski, yet?
    kstateskierestrom
  • HortonHorton Posts: 28,921 Administrator
    @dchristman dude you have some classics
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    gt2003kstateskier
  • HortonHorton Posts: 28,921 Administrator
    edited December 2014
    @AdamCord‌ you know you owe me. Come on ... you want to comment.
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  • lakeolakeo Posts: 77 Baller
    Than- a fin with grooves. now that might be interesting. John?
  • dchristmandchristman Posts: 1,106 Mega Baller
    Sigh... if only my wife appreciated my classic equipment, @horton
    Is it time to ski, yet?
  • HortonHorton Posts: 28,921 Administrator
    @lakeo again the old school explanation is that he holes allow some pressure equalization from the high pressure side to the low pressure side. Just like the low pressure side of and airplane wing sucks a plane up (all the smart guys just barfed on their PCs) the low pressure side of a fin has more impact than the high pressure side. So turning 1/3/5 the low pressure on the left side of the blade is what keeps the ski from swapping ends more than the right side which is pushing all the water.

    The holes bleed water to the pressure side.... hell I don't know.

    When I was making CarbonFins I tried a number of things that would have an effect similar to grooves and did not see any impact.

    Again this is the explanation I was give 25 years ago. @AdamCord‌ be nice when you tell me how incredibly wrong I am.
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  • MattPMattP Posts: 6,109 Mega Baller
    Right now the industry has two different common patterns one is a 4 hole and one is a 5 hole. The 4 hole is used by Mapple skis and still at O'Brien?(it was). Where the five hole is being used by majority of the other manufacturers. When testing skis do the companies test multiple fin hole variations or do they stick to what they know and have used in the past.
    @Horton‌ you designed fins at one point in your life. Did you do any hole pattern testing?
    @AdamCord‌ thoughts. Insight?
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