New CG Fin from Denali

Horton

https://www.denaliskis.com/

MISkier

Is the new fin designed to specifically work on the Denali or would it provide benefit on any ski?

Than_Bogan

From what I understand of the theory behind this fin, it should provide benefit on any ski. However, you'd be on your own to figure out settings, which are basically unrelated to "normal" fin settings.

BraceMaker

I would wonder if the deck thickness for the slot would limit you - IE. if some skis that are thicker/thinner in the tail would not be able to achieve the appropriate settings. Probably overcome that with shims if it were too thin.

Than_Bogan

I had the privilege of testing this fin last fall. For me personally, I found the CG fin an even larger improvement that the c-65 itself, but I was coming from a prototype that was, in effect, a c-53, so the ski wasn't quite as big of a jump for me.

Two specific things really jumped out with this fin:
1) Sooo easy to establish and maintain angle from buoy to centerline. My ski partner noted that my offside pull, which is often the weakest point of my skiing, looked better than it had in many years, perhaps ever. I believe the overall shape of the fin, especially the slot directly under the ski, is mainly responsible for this, allowing the fin to act smaller when you want angle, but larger again when you want stability.
2) Transitioning into the onside, the ski begins to rotate effortlessly, letting me really get ahead of that turn. But at the apex, it grabs the water and finishes hard yet under control. I believe the asymmetric cut holes are responsible for this. My onside has never been anything too impressive, but without doubt these were the best feeling onsides of my life.

Jordan

@Than_Bogan can you shed some light on the asymmetrical cut holes? How do they work? I presume that there aren't right and a left foot fwd designs. I am very curious.

Than_Bogan

@Jordan. Not sure if that was a typo, but there definitely are different lff and rff CG fins. The cuts aid the onside (more than I think any of us really thought they would) while having no perceptible effect on the offside. (Of course, you could tune the overall setup more to optimize offside, knowing the cuts will make your onside magic anyhow )

I'm not sure how much I'm allowed to say about why it works. I'll let the Adams comment on that if they wish to.

bradb

Anybody know of a price yet?

Than_Bogan

@bradb So far the only published offer has been "$2000 -- and comes with a free c-65!"

Jordan

***there definitely are different lff and rff CG fins***

@Than_Bogan well that makes more sense to me! Thanks!

bradb

sounds like no one knows a price for just the fin and block?

adamhcaldwell

YES, the fins are specific for LFF and RFF skiers.

@Than-Bogan - I wouldn't necessarily go as far to say it has 'no perceptible effect' on the off-side. In-fact, it has an appreciable impact on both sides!

During the Onside turn, the holes will produce less drag/resistance to rotation, while during the OFF-side, they produce more drag & resistance to rotation. This enables us to run a shallower fin setup that is beneficial on the HS turn and reduction of overall 'load' experienced behind the boat during the pull, yet still gain the tail stability & deceleration during the OFFside turns. A huge deal when it comes to keeping the line tight on both sides of the course!

We should probably make a video explaining the finer details of what this fin is doing, but we are also not sure we really want to completely let the cat out of the bag.

Ed_Johnson

@adamhcaldwell .... Does this fin utilize differential fin depth tuning like the previous Denali Fin did ???

PS: I still Thank You for that idea, biggest improvement to my onside turn ever !!!

adamhcaldwell

@Ed-Johnson, during the development of the CG fin, I ran with ZERO offset of surface area. My #1 objective was to find another way to create the same effect as what the 'fin area offset' tuning accomplishes. This was because we had a lot of customers that tended to not fully utilize the potential. I wanted a new way to guarantee people would have a fin working for them in an optimal fashion as much as possible - even with little to no offset.

To answer your question, YES, you can use BOTH a CG fin and offset adjustment. BUT, there will probably need to be a fairly significant DFT shift to accommodate and ensure adequate stability on the HS turn. - Which, I don't see anything wrong with that as it will just make you wider into the next ball!

After spending 3 months finding the most optimal setup with the CG fin (w/no offset), the next couple weeks I will be working on adding some of the offset back in and seeing what kind of balances and adjustments need to be made, if any.

I'm stuck in a hard spot though, as there is yet another new very dynamic top secret fin/box I we are working on. The downside is there would be no way to create any offset what-so-ever with the new fin block - another reason behind development of the CG fin as it preserves your ability to naturally have an asymmetric fin setup on the ski.

Than_Bogan

@Ed_Johnson Ymmv, but fwiw I found the offset to be "a helpful option" whereas I found the CG to be closer to "on side miracle."

Gloersen

@adamhcaldwell - that's an rff-F pictured? Assuming different thicknesses were tried for optimal drag and hole bevel effect, ended up? around .095"? Any particulars in alloy grade choice?

Than_Bogan

Yes RFF is pictured. I cannot answer the other questions.

Horton

I can say that Off Set is a real thing and a great idea. My few rides with the CG fin and no Offset were as good or better.

AdamCord

https://www.denaliskis.com/cg-fin

@MISkier anyone can order the fin.

@BraceMaker the Denali is thicker through the tail than most other skis so worst case it may require some filing to get it to work on thinner skis.

6balls

Just ordered my fin attached to one of those c-65 thingies. Bring spring.

Rich

Can we buy the finblock & the blade?

Dacon62

Very cool. More tech on the fin side is long overdue.

adamhcaldwell

@Glorsen, The real reason fin thickness is such a huge deal is largely because of the holes and their respective geometry. The thicker the fin - the more 'drag' or resistance the holes can create. Theres no doubt that if we make a fin with no holes at all, any fin with a thickness .06 to 0.12" would feel excessively fast at 34 and 36mph. It would come down to a function of 'shape' on the leading and trailing edge - which has been done, and is fairly limited in terms of how far you can really take it.

Our goal was to unbalance the reaction forces and drag on each side of the fin. By exploiting the geometry of the holes, we were able to increase the reaction force on one side of the fin, while simultaneously reducing it on the other. The aim was to do this in such a way that created optimal performance on both sides of the course. This fin is no doubt a game changer.

Some of the development fins would offset the reaction forces of the fin so much that the ski would turn on a dime on one side of the course, but wouldn't even begin to initiate a turn on the other. The most extreme version of the fin that I had worked on felt completely normal on the pullout for the gate, but when trying to roll the ski over and move back toward CL I honestly could not displace it from its path straight down course. It did not budge. Until of course I slammed it on edge in hopes to make the gate on time. Lets say I was successful at getting the ski on edge, but the fin was more successful at creating a massive reaction force. Strong enough that the ski came to an immediate stop and ripped me right out of my boots before I even got to the first whitewash. Wish that one was on video. Far worse then hitting a Perfect Pass magnet!

I am certain that in the next several years you will see more and more 'new' fins that will steer away from the current geometry. There is a lot of magic tied up there that few understand. Over the years, I would think I learned something about a fin, but the logic could not be applied and explained in all aspects of the course. For example, the surface area argument. Drilling holes to reduce surface area does NOT reduce drag. To me, surface area is a very, very small piece of the puzzle.

Fin dynamics are an extremely challenging thing to wrap your mind around. The development of this fin finally provide hard physical proof of something that I have been scratching my head over for the last 15 years - something that even some of the sharpest engineers I know couldn't put a concrete explanation to. Once again, it was completely non intuitive, and opposite to what you might think until the answer is staring you right in the face.

For those wondering, there is a very specific reason why only 3 out of the 5 holes are 'ported' or 'directional'.

DW

@adamhcaldwell : Nice work coupling an asymmetric flow pattern fin to the asymmetric stance of the skier along with being a very simple and elegant solution. You might qualify the fin dynamics statement as the understatement of the thread, the operating conditions of the fin make it very difficult to visualize and also model for simulation. I am sure there is a lot more to come.

adamhcaldwell

@DW - Thanks! and YES always working on something.

KRoundy

@adamhcaldwell said, "For those wondering, there is a very specific reason why only 3 out of the 5 holes are 'ported' or 'directional'."

Mind blown. It feels like we may still be in the early stages of our understanding regarding fins and slalom skiing, even after all these years. I love this sport. The deeper you dive the more there is to see.

Than_Bogan

Yeah, my brief time on several Denali fin prototypes has me convinced that there is quite a bit more performance "hidden" in the fin -- maybe more than is left to discover for the ski itself.

EricKelley

Nice job Adam. This will change things for sure. More set up variables, lots of ideas to ponder..

Jibbo

@adamhcaldwell what does the bent tip of the wing do? I have seen them before in the past but most manufacturers stay with a pretty standard flat wing these days.

Jordan

I find this concept to be very interesting. Years ago I had an asymmetrical Lapointe ski that came in lff an rff versions. While I thought that this was ground breaking at the time, I also thought that it would be very unlikely that the idea would take hold because of the increased cost of tooling and R&D to the manufacturer and the increased cost of inventory for dealers The thought that the skier needs something different in the heel side versus the toe side turn just makes sense. Addressing that with different fins is genius!

Congrats to the Adams for coming up with this!

adamhcaldwell

@Jibbo, No doubt there have been a lot of 'bent wings' over the years. However, the trend is that the tip of the wing was rolled up parallel with the fin. Which, I think would just reduce drag on the wings tip. Ours is much different.



The bend on the Denali wing is positioned about 45 deg off CL.

Objective is to manipulate the reaction force on the wing such that as the ski rolls up into extreme bank angle there is still the overall effect of a 'downforce' in the tail. Usually we do that by using adequately deep or long fin setups. At extreme conditions however - which you run into at your hardest pass - sometimes a larger fin area is not enough and your risk of tail lift or blowout is significantly higher.

Our bent wing, in some ways, has a similar characteristic to rounding the back corner of the skis tail. Like what you would see Wade Cox do on a lot of his HOs back in the day. Rounding off that corner was an easy way to blur the lines between a 'square' and 'round' tail geometry. Each have a very different 'feel' during the preturn, apex & finish.

The concept goes back to some of our global design objectives - Develop less load in the pull, without excessive speed in the turn. Put differently, get the ski to 'accelerate faster & easier' and 'decelerate faster & easier'.

We aim to use fin settings that have much less resistance during the pull (less overall fin loading), yet still have ample deceleration and tail stability into and through the turn without risk of blowing the fin out.