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Long Shallow vs Short Deep Fin

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Comments

  • Ed_JohnsonEd_Johnson Posts: 1,827
    I can totally testify what the Adam's are saying about differential depth adjustment. Takes less than 5 minutes to do it, costs about .15 cents, and the results are amazing. Adding one standard and one thin washer resulted in a depth change of .030, and completely solved my overturning issues with the D3 NRG. I cannot thank both of them enough for this advice.

    Loving the Reflex Supershell with R Style Rear !!!
    adamhcaldwellWishmylemsky
  • HortonHorton Posts: 25,181 Administrator
    Reading the thread by @Tap about fin surface reminded me that my original thesis was lost in this discussion. I happen to be a firm believer that a shallower fin or less total fin for On Side is almost always better. So for the "fan boys", yes, I think Adam and Adam really found something there.

    The point of the video and this thread is that depth impacts tail depth and ski attitude. My question for the brainiacs is if surface area and Center of Pressure are kept static why would a deeper fin pull the tail down more than a shallower fin?

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  • GloersenGloersen Posts: 766 Crazy Baller
    edited January 9
    if surface area and Center of Pressure are kept static why would a deeper fin pull the tail down more than a shallower fin?

    for a given, fixed FSA, X-axis centroid can be maintained with corresponding DFT adjustment.

    However, for a fixed FSA, the fin with the greater depth, the unadjustable Y-axis centroid moves down (although the asymmetrical washer technique can mitigate this) as @tap calculated; this will yield the onside results on the tail/tip as @Horton describes, imo.

    It's all cool stuff but look forward to the self-adjusting SmartFin(tm)
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  • DanEDanE Posts: 814 Crazy Baller
    From a very reputable source: Long shallow promotes longer preturns and require a bit more patience from apex to hookup.
    Short deep results in a more hooked style turn.
  • JoepruncJoeprunc Posts: 248 Baller
    Interested in this discussion.
    I just picked up a 2018 Vapor Probuild (coming off a Strada), and set it up with a long and shallow. I only have two sets on it so my thoughts are very preliminary.....but ski seems to be very predictable and stable (not as fast as the strada), but from the post above "the longer preturn and patience hooking up" makes sense with what I'm feeling. Maybe I'll play with the fin this weekend.
  • HortonHorton Posts: 25,181 Administrator
    edited September 4
    @Stevie Boy hope you do not mind that I merged out threads.

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  • Stevie BoyStevie Boy Posts: 1,686 ★★★Triple Panda Award Recipient ★★★
    @Horton np people have suggested the washer trick to me and I was a bit sceptical but it seems like there numbers of people that do it,
    Would still like to know if either of the setups would require a slightly different approach in style whilst skiing.

    " Ski It Like You Mean It ! ”

  • HortonHorton Posts: 25,181 Administrator
    @Stevie Boy no need to change skiing style. Ski as technically well as you can and ski with gear that works w/ your skill set.

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  • DangerBoyDangerBoy Posts: 117 Baller
    edited September 5
    I find this discussion fascinating and intriguing, especially the talk about differential fin depth settings. I've done some searching on this forum and the 'net in general and I haven't yet found anything that shows me how this differential find depth settings using thin washers is done and how I might use it to my advantage. Can somebody please be kind enough to point me to a video, thread and/or web page that will teach me all about this part of finlore? You can PM me if you prefer.

    This finlore stuff is kind of like wandlore in Harry Potter; all steeped in legend, alchemy and mystery... ;)
    I can take anything apart
  • Ed_JohnsonEd_Johnson Posts: 1,827
    edited September 5
    @DangerBoy .... As I said before it works great. I use the same settings Caldwell mentioned before with the CG Fin on my NRG, it's a totally different ski than when it was stock. Plus I use long/shallow, and it turns really quick off the apex, setting a lot of angle.
    Here's the info on differential tuning.
    https://www.denaliskis.com/single-post/2016/01/31/Fin-Area-Tuning-System

    Loving the Reflex Supershell with R Style Rear !!!
  • GlydonGlydon Posts: 220 Baller
    @DangerBoy you want to get into "finlore" pickup a copy of @SkiJay 's The Fin Whisperer !
  • BraceMakerBraceMaker Posts: 2,593 Mega Baller
    @DangerBoy you literally just loosen off the clamp remove one middle screw slip a washer between the box and the fin and snug all 6 screws back up, the one with the washer tighten last, where to put it and how much it should be is a good read on their site.

    A slightly tougher method is to remove the box, tap the hole for a set screw and replace the screw with a flat faced set screw.
  • DangerBoyDangerBoy Posts: 117 Baller
    edited September 5
    The diagrams on the Denali skis page aren't that clear to me. What are we trying to do here? Tilt the bottom of the fin slightly to towards the onside turn (i.e. tilt bottom to right for LFF/to left for RFF)? If that's the case, why couldn't you just put a strip of very thin shim metal under one edge of the fin block so the fin is still 90 degrees to the finblock but the finblock is slightly tilted relative to the ski? Wouldn't that accomplish the same thing?
    I can take anything apart
  • Ed_JohnsonEd_Johnson Posts: 1,827
    edited September 5
    @DangerBoy .... Your NOT trying to tilt the fin, your just very simply lowering one side of the tail relative to the fin so the depths are different on each side. That is as simple as it gets. A .15 cent, 5 minute mod.
    Key is getting the thickness of the washer or washers to equal at least a .030 difference to have any effect.

    Loving the Reflex Supershell with R Style Rear !!!
  • DangerBoyDangerBoy Posts: 117 Baller
    @Ed_Johnson whether you envision moving one side of the ski tail relative to a fin that you imagine is fixed or tilt the fin relative to a ski that you imagine is fixed is the same thing. When all is said and done, if you look at the setup from the rear of the ski and the ski base is on the horizontal, the fin will not be perpendicular to the bottom of the ski it will be tilted or slanted slightly to one side, correct?
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  • Ed_JohnsonEd_Johnson Posts: 1,827
    edited September 5
    NO...NO...NO...The fin is not tilted !!! Only the bottom of the ski is lowered on one side, making that side shallower.

    Loving the Reflex Supershell with R Style Rear !!!
  • HortonHorton Posts: 25,181 Administrator
    There is no tilt. You are deforming the bottom of the ski so the fin is effectively smaller on one side.

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  • BraceMakerBraceMaker Posts: 2,593 Mega Baller
  • BraceMakerBraceMaker Posts: 2,593 Mega Baller

  • DangerBoyDangerBoy Posts: 117 Baller
    Ahh, I get it now. You're actually bending the ski downwards a hair on one side of the finblock! Skis are so rigid I didn't think that was possible but I guess the amount of deflection doesn't have to be very much to have a relatively large effect. Okay, I'm with the program now. So you deflect the tail downward on the back foot (onside) side of the ski to get a shallower fin depth and less cross-section/slide resistance on the onside turn and more on the offside turn? Interesting.

    As an alternative to that, could you not just paint on a few extra layers of resin on one side of the fin to make the ski on that side of the fin 0.030" thicker? I'm just speaking theoretically here. I doubt anyone would actually want to do that but theoretically speaking, would that not also accomplish more or less the same thing?
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  • HortonHorton Posts: 25,181 Administrator
    @DangerBoy yes you could add Bondo to the bottom of the ski next to the fin for the same effect

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  • Stevie BoyStevie Boy Posts: 1,686 ★★★Triple Panda Award Recipient ★★★
    No ! No ! please no Bondo

    " Ski It Like You Mean It ! ”

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