Denali C75 ..41off ..Boom!

[drewski32]

@adamhcaldwell After seeing the example with nate I think I'm starting to understand what you're getting at. Are you suggesting that we need to achieve the required change in yaw through the transition without rolling too hard onto the inside edge and thus stopping the outbound trajectory of the ski? And by creating more roll stability and a little more freedom in yaw, it becomes easier to achieve this?

[Adam Caldwell]

@drewski32 - now your cooking with fire.

 

This is the same reason why being “open” behind the boat was such a huge push for a long time. It is a functional way to get the hips to open and effectively get the ski to “yaw” sooner. Problem is, you can’t allow the body to “open” in a productive way through CL if you never generated the downswing velocity on the way there. Starting off “too open” on the way to CL will inhibit your ability to generate that speed. More so for lefties then righties.

 

The CG fin also supports this philosophy, by complimenting the asymmetric nature of the stance as the skier crosses CL and begins the early stages of the preturn.

[Adam Caldwell]

@jimbrake very cool! I’ve thought a lot about surfboards!

 

Just consider all the alternative combinations for rocker and profile shape at their extremes. Super flat or super banana.

 

I’m not claiming that what we’re doing is the absolute best way to do it, but it certainly makes sense to us.

 

The thing to remember that any geometric surface that causes a fluid to change direction will typically increase drag. Unless of course, your playing with hyper-cavitating propellers, vortex shedding in air, or doing anything that would influence changes to the Coanda effect on a control surface.

 

For example with surfboards, imagine a longboard with a lot of surface area. You already have a lot of film drag due to the whetted surface. Add a bunch of rocker, or a rounder profile shape, and you'll just make the situation worse as more 'shape' equates to more drag and more stability. Depending on what you are trying to accomplish with the board, this can be a good thing , OR a bad thing. I don't think its a coincidence longer boards are relatively flat with little 'shape'/rocker.

 

Just imagine how well a giant round beach ball would stay on plane versus a big sheet of plywood. For a quick lesson of the influence of 'shape' on drag and stability effects, get in your boat, travel about 5-10mph and then hang a turn buoy attached to a rope off the side and let it just barely touch the water. The more curvature -in any direction - will significantly increase drag. This is a great way to see/feel/and experience it. Same reason you can get a ping pong ball to hover in a high speed jet like a hairdryer, or stream of water.

 

Back to surfing, a shorter board that has no rocker and is more rectangular would be pretty squirly with very little drag. Like what a trick ski feels like. To create a stabilizing effect, shaping the board to cause the streamline fluid-flow to change direction and effectively create drag will act to provide a level of stability to the rider. You can play with that stabilizing effect both with the profile and rocker geometry, and going further; with the bevels & rails & bottom surface geometry.

 

In our slalom, we have a 400hp engine trying to throw swing us out into a turn going really fast. We don't have a set of disc brakes or parachutes to work with (yet), so we utilize surface geometry to create stability and drag effects to help slow us down to stay in timing with the slalom course.

 

For us (DENALI), there are key locations on the ski that we WANT to create an increased amount of drag in the profile shape & rocker. For example, some skis have a very soft transition between the tail and the tip in attempts to make the ski 'more efficient'. Others, like the Denali, have a more aggressive transition to create a zone on the ski that is 'less efficient'. The more aggressive transition causes the fluid stream to change direction and increase drag in a specific location. This acts to create a control point for rotation. This does make our skis a little more sensitive with boot position, but we think thats a good thing. As its much more obvious when the bindings are in the WRONG spot and quicker to diagnose a required setting change.

[Deke]

@adamhcaldwell that explains why rocker but not why rocker and outline the same.

[Adam Caldwell]

@deke - come again?

 

Lets just say your dealing with an object that is never running flat to the water (except at the gate), and is constantly changing roll angle.

 

The more extreme your rocker shape is, and the less extreme the profile shape, then as roll angle increases, then your water-break, lift and drag would change significantly.

 

If you had a straight profile shape with big banana rocker, then as the ski rolls from flat to edge you would completely change where the water break sits on the ski, as well as the streamline flow characteristics along the ski, and its propensity to start "turning'. vice versa is also true.

 

Ill share a lot of info, and just about anything related to technique, but like with the CG fin's flow dynamics, there are some things we would like to keep to ourselves. Lets just say we have found a happy medium between the two.

 

 

 

[jimbrake]

@adamhcaldwell - I get it. Sort of. Fortunately slalom skis are designed to work in a relatively uniform environment. The ocean wave environment is anything but and the needs of a surfer on a board are also widely varying. I probably shouldn't have even brought up the surfboard in my question. I'm just mainly interested in the Denali rocker and outline and you explained the reasoning well.

[BraceMaker]

@deke it makes me want to find other skis and stack them to see what they look like in re: profile to rocker. But remember that it is the top sheet's rocker but the tunnel and side aren't molded by the top sheet.

 

I suspect that in doing so the shape is constrained in CAD in a way that is efficient for modeling.

[Wish]

This is why I love starting any Denali thread. We just get to sit back and learn. Seems every Denali thread is full of explanations, techniques, and well... science. Thank you Adams for continuing your pursuit of the perfect ski, taking the time to share your knowledge, explaining the what, where, why and how's of slalom and taking us along for the ride!!

[BlueSki]

@Wish, I thought you were just bragging about running 41 on your new Denali.

[Wish]

@Blueski in my dreams just about every night. That and a boatless slalom set, but that one is just weird.

[Adam Caldwell]

Thanks @Wish - Kudos to epic thread title. lol.

[Ed_Johnson]

I will 2nd what Wish had to say. You Guy's have helped so much with Technique and Equipment. Your articles on developing swing speed and modifying the Reflex boot have helped me immensely. Add to that differential Fin Depth... Plus the CG Fin totally changed my NRG.

 

Starting to save for the C-75 "XL" Big Guy Version !!!!

 

 

[ISP6ball]

98% off their explanations are over my head. I just scroll through the thread and look for cool pictures and diagrams :)

[jimbrake]

@Wish - you know, your spelling has really gotten a lot better.

[Wish]

Of corse ..or is it course..

[slow]

Matching rocker to ski profile is a marketing line. 4front snow skis have the idea on their website for years but can’t really explain it other than iit sounds interesting.

[AdamCord]

@slow why on earth would we use this as a “marketing line”?

 

The rocker and the profile shape of this ski are the same. You can see that in the pics Caldwell posted above in this thread.

 

This is so that when the ski rolls, the water break and therefore center of pressure under the ski does not move forward or backward. This has the effect of making the edge changes seamless, let’s you use the entire ski in the turn if needed, and helps keep the tip down and driving through center through the turns.

 

That’s also why the skis look so flat in the tip compared to other skis. We don’t add a bunch of unnecessary and arbitrary rocker there, because we want to be able to use that part of the ski.

 

We came up with this idea years ago when analyzing lots of different skis. We realized that most of the better skis out there have a rocker and width profile that were pretty close to matching from about 40” back. We figured that couldn’t be a coincidence so we tested it out, and found that skis with matching rocker and profile from 40” back do indeed work better. Then we figured why the hell not try it on the whole ski, and that’s when the 3.1 was born in 2015.

 

We’ve used this design function ever since and have even used the width/rocker profile to define other aspects of the ski.

 

If we were worried about marketing gimmicks we’d come up with something cooler sounding than this.

[Bill22]

Watching video of someone run 41off in March is even better marketing.

[Adam Caldwell]

@slow, worth noting, it’s not a coincidence our skis are extremely hard to blow out of the water. This design attribute is one of the major reasons behind that fact. The tip geometry doesn’t turn into a plow when the water break moves too far forward and stoping forward progression of the ski. You may not have a perfect turn, but you can survive the turn and go get the next ball.

 

Maybe we should be talking about the tip-to-tail-tunnel instead? Another key ingredient in preventing tail blow! Or the 1:1 torque to flex ratio? We’ve got tons of BS available... unfortunately they’re all legitimate design characteristics were using to figure out how to break records.

 

I’m an engineer, not a marketing guru.

[ghutch]

X10 on the tail blow comment. I used to blow the tail fairly often on my Goode and D3 running 32 into 35. Since being on the c-65 I'm pretty sure I haven't blown it out since. And I have the confidence this ski will let me push it to scrap for that next buoy. Can't wait for the big boy 7.5's to come out!

[Adam Caldwell]

4 ball here is a great example. Moving into a offside turn this late and fast with your hips back on anything other ski and I’m blowing the tail and swimming at 4.

 

This was tonight, on the same ski as on last Sunday’s 41 (from the boat video on first page of the thread) , but with boot pulled boot back 1/2” and fin forward 50/1000, longer 30/1000 and shallower 10/1000, just to play around at longer lines with. But couldn’t NOT cut the rope. It wasn’t better, but I did learn something which is always the goal.

 

Horrible looking pass but still kind of baffling to get to 5 ball after dorking up 2 ball so bad... got there way earlier then I expected to.

 

[slow]

i am a mechanical engineer and a business owner. I know you’re smart enough know that this is a great place to market your product. Maybe you are a marketing guru.

[drewski32]

@adamcord "If we were worried about marketing gimmicks we’d come up with something cooler sounding than this."

 

Flextail? ?

[customski]

 

My "borrowed ski" after using Denalis for nearly 3 years. Definitely dont blow Denali tails as often.

[Adam Caldwell]

Separate from the rocker and profile geometry, in the design of the ski alone there are are at least 7 different design elements that all factor into a skis propensity to "blow the tail".

[Adam Caldwell]

Almost everytime @AdamCord or I ski we are trying to learn something to help a customer or someone on the test team. We never suggest a setup we haven't already been to before. It doesn't always go as planned, but we usually at least have a better understanding of what other people might be feeling when we communicate with them. Every design has a different characteristic and I feel like it takes me about 14-18mo to know ALL there is to know about a ski in terms of the ideal setup. Thats a lot of sets, and even more fin adjustments - somedays theres a move EVERY pass... (I have very patient ski buddies!)

 

I dont have video, but its not uncommon that we mount up double radar boots, stand and lean on the back foot and keep our hips back and elbows away from the body, just to figure out settings for 'someone else' who is at an earlier stage in this slalom game. We want people to experience what we are feeling as much as humanly possible. A huge challenge.

 

Today, I went a little smaller with the fin today and a touch forward. Maybe a little too far for shortline, but was nice and free and finished into angle with speed at 32/35 really well. Definitely a lot better there at the earlier passes.

 

1.10dft, 2.450, 6.710, 7wing 27.75 boot - not to mention@9400 on the wheel - AGAIN.

 

This highlights how UN-SENSITIVE the CG fin is to Depth adjustments. These settings are; 70/1000 shallower, 45/1000 forward and 10/1000 shorter then the 41video (#2) from last weekend (and on a stiffer flex ski). Last time I checked you can NOT do that on normal fin!

 

[Texas6]

I can’t comprehend 2-5 ball. None of it makes sense

[Than_Bogan]

Well thanks for making -41 look a little challenging...

[Adam Caldwell]

@Texas6 - Thats called SCRAP CITY. I should have been swimming at 2 with how far the ski turned....I think beyond 90deg b/c the tail slid through WAY to far. Time to put more fin back. Maybe 70/1000 depth change was a bit much..

[6balls]

@adamhcaldwell if u don’t dial that thing better in on your off side u might miss a 41?

[BlueSki]

This set and the set one the first page seem illustrative of the benefit of different fin setting for different line lengths. It seems that on the early passes the line stayed tighter with these settings and seemed easier than for the set on page one. Clearly the shorter line lengths were different from your comments and video. @adamhcaldwell, care to elaborate any further? I ask only because I am certain that I will learn something.

[JAS]

Do you find the same benefits from yaw at longer line lengths (>28 off)

[DangerBoy]

@adamhcaldwell I can't believe how easy you make those 32, 35, 38 and 39 off passes look. And you're the same height as me! I've never run a course in my life but based on how bloody easy it looks in your videos I'm pretty sure I could get through 39' off on my first or second try. How hard can it be? ;) I might need one of your skis and fins though. ;)

[jipster43]

I just bought a new ski, but I had to put my name down for a small Denali now that they are making a ski my size.

[9400]

The 41s you see on here are just the ones he’s running when there’s somebody in the boat to video. There’s more being run than what you see and it’s been happening all winter and in all conditions. (Well at least since this ski came out from behind the curtain). I was surprised to see that one look that scrappy when I watched because it felt really smooth. I normally don’t even look in the mirror when driving past -28 but now sometimes watch him at -39 through the mirror because I know he won’t miss it.

[Adam Caldwell]

@BlueSki- Yes your absolutely correct.

 

When we talk about slalom were talking about energy and trajectory. Like in any kinematic system, if we want something to go further, or higher, we need MORE energy somehow. OR alternatively, We need the same amount of energy, but reduce the losses and inefficiency in things like drag.

 

The smaller fin setup that is further forward basically helped to reduce drag, reduce the resistance to the ski wanting to 'rotate' in all 3 directions of Pitch Roll and Yaw, meaning I basically was able to get MORE of all three, quicker AND the ski did not decelerate as rapidly during the pre-turn. All good things for longer lines as it caters to helping the skier create more energy before CL, to provide more space & time before the ball after CL.

 

Imagine a 200' rope. Lets say you only have 10deg of displacement WRT the pylon when at the buoy. As soon as the rope starts to pull, there is not much working in your favor to accelerate you across course, but the fact the boat is going 34mph and your nearly directly behind it, its doing a lot to try to accelerate you downcourse only. This is going to require a ski that will move into a rolled & banked position easier & faster prior to CL. The faster we can move through the downswing to CL, the more TIME we will have between CL and the next Buoy.

 

At shortline, and with much more angular displacement from CL when at the ball, we have the benefit of the boat accelerating us toward CL before it tries to accelerate our mass downcourse. In an ideal situation we are connecting to they pull of the boat closer to a 45deg displacement from CL. Therefore, if were not careful, we can get going TOO FAST to slow down enough to make a controlled turn. Which is what you see in the most recent video.

 

[rockdog]

Those passes looked unbelievable all the way through. So early! I can’t scrap a 14m like @adamhcaldwell scraps a 10.25m. Absolutely amazing skiing, in a suit no less.

[Adam Caldwell]

@JAS,

One reason this ski, the C75, is doing what its doing has to do with its ability to help the skier decrease the time spent before CL - and ultimately increasing the time, space and distance before the next ball. The YAW element after CL is only realized AFTER a much bigger and more important event has taken place.

 

Consider this;

 

The time period, T, from buoy to buoy is FIXED for a given boat speed. Meaning that T= Time before CL + Time After CL.

 

Therefore, the only way to create MORE TIME between CL and the next buoy is to DECREASE the time we spend in the downswing to from the buoy to CL.

 

The best way I see to accomplish this (ie reduce time from buoy to CL) is to get the ski and the boat to move away from each-other FASTER. Sure, putting a big fin on a ski can help make this happen, however, that big fin then becomes over-stable, and a challenge for the ski to enter the preturn without excessive drag or resistance to rotation.

 

Before centerline, the additional width and tunnel in the tail of the C7.5 work in your favor to reduce down-course slip, making the boat move away from you FASTER during the down swing WITHOUT needing a big fin. The short wheel base -boot back fin foward to reduce YAW stability- help you get the ski to YAW and roll into angle easier during the early stages of the down swing such that the tunnel can start to work its magic.

 

This way we get the result we want before and after CL. An increase in angular acceleration before CL producing more time before the next buoy with a ski that moves easily into the preturn. More time equates to more distance, more distance equates to more ski rotation prior to arriving at the buoy. Then, combine all that and sprinkle some flex and torsion fairy dust in, and the final result equates to MORE BUOYS and SHORTER ROPE.

[Rednucleus]

So if we are decreasing time before CL, we are increasing acceleration to CL? Does that put a skier like me (make 50% of 15 off 32mph) at more risk of going out the front when I don't get back to a good stacked position?

[JAS]

Thanks, I could easily see the benefit of yaw after CL, but was missing benefits before CL.

Tuning and setup then to maximize acceleration of ski? Increase of Ski path angle is simply a result of efficiency.

As a mere mortal skier all these years I think I’ve been “ Lookin for love in all the wrong places”. I admire what you guys are doing

 

 

[Adam Caldwell]

This is for sure a Practice PB. Never had a legit pull to 2 ball at 43. Not quite around 2, more straight through the top of it. First time trying since August last summer.

 

Heel side seems to be good no matter what. Pulling fin back, and moving boot back 1/2" made the ski a little too slow to rotate during the pre-turn into offside causing me to parallel the boat before the buoy with these numbers.

 

Will edit and post the settings shortly. I didn't have time to measure before skiing.

 

@AdamCord said its time to speed the boat up and see what this ski is capable of at 36 next.

 

 

 

[Adam Caldwell]

@jipster43 - Height & Weight?

[travtitle]

This is so cool- thanks for posting these Adam. Great thread!

[Adam Caldwell]

@travtitle - just let me know when to stop.

 

What I think is really cool is that you can see how different each setup is. They all have very different feel to them on the water. Today was a little slow to accelerate with bigger turns compared to yesterday (video #4 above). Yesterday felt amazing behind the boat, just too fast loose in the finish.

 

Official measurements:

Boot back 1/2" and fin back 100/1000s , slightly longer shallower. from #4

27.5 1.0" dft, 2.440, 6.730, 7wing.

[Than_Bogan]

You know you're doing some ridiculously sick skiing when a clean 41 doesn't even merit a fist pump...

[Adam Caldwell]

@Than_Bogan naturally I was just frustrated to not go further at 43. Lol. The addition is real.

[9400]

@Than_Bogan, well he does run it pretty much every set right now.

[Wish]

What is the record @34mph? Who set it?

[Adam Caldwell]

@ Wish pretty sure Jeff R has the record at 2. Theres video of Mapple going to 4 ball at 34mph.

 

I have seen CP pull to 4 at 36mph from the boat, and I have no clue how far Nate can go, but guessing pretty far.

[jipster43]

@adamhcaldwell 5’5” and a buck thirty. My PB is 2.5@32 off. I have a hard time with my stack and generating speed, but I can typically turn a ski... as long as I’m not coming in too hot!

 

My best lobbying efforts in support of the small size comes down to better marketing viability with the women skiers, but I get that y’all are pursuing a passion more than a corporate model. Thanks for that!