Ski "roll" angle: More not necessarily better?

[Than_Bogan]

Once again, @gator1 is forcing me to start a new thread to further discuss some "crazy" thing he mentioned off-handedly in another thread. Here is a redacted version (with emphasis added by me):

 

"There are TWO angles of attack of ski to water.

 

The first /snip/.

 

The second angle of attack I never thought about until I saw Rogers ski in those floppy Wiley's. If you imagine the ski almost 90 degrees to the wake, and flat on top of the water this other angle is how far the ski is rolled away from the boat about its longitudinal axis. (Tipped on edge)

If the ski is rolled too far on edge it loses lift and creates drag. Far enough and it starts to stall, and slides towards the boat more than it carves across the wake.

 

/snip/

 

And the secondary light variable-- longitudinal roll vs speed.

 

/snip/"

 

Until this very moment, I have never considered the possibility that having your ski "too far" onto its edge will result in less angle.

 

Frankly, I don't really understand what @gator1 is talking about yet. But history suggest that once I do, I learn something.

 

And this is of great interest to me right now, because I am adjusting to new "soft shell" boots from rubber, and trying to figure out how to set the top buckle to suit my style.

 

So have at it! Do people WANT their bindings to allow rotation of the lower leg relative to the ski -- even when directly behind the boat? Why or why not?

[Razorskier1]

For me the only way to get too much edge in the water is for me to be leaning too hard away from the boat. If I stay on top of the ski the way Chet says I should, then my edge will be just right. I can't imagine not wanting my ski edge to be consistent with my body position.

[kfennell]

I don't have any input to this, but trent told me the only reason i can get away with wearing bindings as stiff as mine is that they plate under them flexes a little, it makes sense I guess that this keeps the ski flatter.

[Chef23]

Reading this stuff makes my brain hurt. My guess is that the better you are technically the less you want the binding to allow free movement. I equate it somewhat to snow ski boots. Boots for better skiers are much more responsive and better skiers make fewer mistakes with their feet/lower legs.

[Than_Bogan]

@Chef23 I've always assumed that as well and basically equated my inability to handle hard shells with technical flaws.

 

But some threads today and @gator1's comments strongly suggested otherwise, most notably about Andy cutting down his boots. Safe to say he's pretty good technically :). And of course Nate is in a rubber boot and an RTP -- pretty much the least "responsive" system out there.

[andjules]

You've got two questions:

- is there a maximum roll angle, after which performance (speed-for-effort) goes down?

- does the former mean that hard shells can be negative?

 

New additional question:

- if there is a maximum roll angle, do we ever get past it, or have any difficulty managing it?

My guess is that the answer to this one is NO. Either we manage it intuitively/naturally (we sense when more angle isn't going to help and adjust instinctively), or we just never get that steep. There are some smart folks in this sport, many of whom think too much... if it were even close to being a real problem, I think we'd be talking about it... especially on BallOfSpray.

- as for hard shells, I don't have any experience, but I do notice: i) people saying it takes a few sets to get used to hard shells, and ii) some people talking about being 'light on the line' and not leaning too hard, etc. Could i) and ii) be (some what) related to hard shells and controlling roll angle? Probably not. But I smell a good conspiracy theory.

[Chef23]

@Than_Bogan‌ I don't think that when it comes to water skiing that you can't ski well in a boot that is softer. I think with water skiing lateral stiffness/control is a good thing and forward stiffness isn't necessarily a good thing. That is why with hardshells sometimes I think having the lower buckles tight and the upper buckles looser works well.

 

[Horton]

I have skied on Jeff’s ski and used his bindings. His Wiley's look floppy but I almost pulled a hamstring getting them on. They are tight and stiff. I promise the roll angle of his ski matches the roll angle of his foot.

[MattP]

I think I have a video of @Horton trying to get that ski on. I was in the boat it was pretty damn funny!

[Horton]

the one thing that you do notice with more or less stiff bindings is harshness at the edge change. I realize this is not what you're talking about but just want to make clear that you're not going to mess with your roll angle with softer bindings. granted there may be some impact but not significant unless of course you go over the top crazy unsupportive

[Horton]

@ob if you are working on inside shoulder higher you are working on flatter ski...

[gator1]

Watch that heel shift go pro on ski video of Andy. Ski does not match shin bone angle. Stop a 41 off video of Nate at or in the wakes. Ski is much flatter than shin bone angle/ his lean angle. Don't have close up video of Jeff, but I was 40 or so feet away. I saw a flatter ski than lean.

 

Maybe semantics, @Horton, but to be precise, I am saying in the soft boots ski roll equals foot angle, while it does NOT equal shin bone/ankle angle. Whereas in a hard high boot, ski roll is much closer to shin bone angle because the ankle/foot has been locked to the shin.

 

By a quick static examination you can look at a pair of wileys on a ski without a skier in them. They point straight up. Put yourself or Jeff in them, and, since the your legs are attached to your hips, the cuff of the binding no longer points straight up. Both cuffs point out. The ankle on both feet has pronated (supinated, origaminated, some PT guy help me) and the rubber has followed the curve of the shinbone out.

 

Just standing on the dock, ski roll is 0 degrees and shin bone angle is about 5 degrees. In a hard boot without canting the shin will be trying to achieve 5 degrees, but the boot won't let it, and will be cutting into the outside of both legs at the top of the cuff.

 

This is why you never heard of canting when the only bindings were rubber, but when the super stiff ones came out it became a topic. And, I contend, is why it takes so long for many people to adjust to high stiff boots if they don't cant them.

 

I'd sure like to know Andy well enough to ask him why he cuts his cuff down........Maybe some baller out there can ask him.

 

@Than_Bogan‌ stop sucking me into this stuff. I've never gotten over my Panda on the whole straight back leg thing and I sense another one hovering nearby.

[ToddL]

@andjules‌ "There are some smart folks in this sport, many of whom think too much..." LOL!

[ForrestGump]

@Toddl At first I thought you typed "many of whom drink to much." lol

[ToddL]

@ShaneH‌ that, too!

[jimbrake]

I cant (cant = vertical tilt, not a lateral twist) my front D3 Leverage towards the left edge of the ski (I'm LFF) for that exact reason @gator1. Even in a rubber binding (although it is pretty dang stiff) if I didn't do that my front knee (and left hip) would be directly over the top of the ski and that makes me roll too hard onto the right edge. A degree or two of cant to the left and now my ski feels symmetrical rolling onto either edge.

[gator1]

@jimbrake‌ Sounds like you are a smart man who is thinking just the right amount.

 

My buddy who skis soft boots wanted to try my gatormoded Stealths, which I had a hell of a time skiing until I canted them. He'd never skied hard shells. He ran 28 up the rope into 38 first try.

 

He also coined the now classic phrase as he stood on the platform looking at the boots and two dog collars and parachute cords of the prototype gatormod: "Um, there seems to be a lot of sh!t going on back here"

 

@Than_Bogan‌ maybe you could turn your question around and get the answer I was trying to reach with my theory. Ask "why is heavy on the line/too much lean a bad thing?". Or, even more to the point "why can the studs hold more angle then the wannabe's with what looks to be the same degree of lean?". Or "WHY does Chet say stay on top the ski?"

 

Until an "expert" can tell my why, I am just like a dog in a cartoon hearing "blah blah blah GATOR BAD blah blah blah". Without the why its just dogma to me.

[Than_Bogan]

@Gator1 Hah! I have the same problem. My brain won't let me pay attention without the why. I'm pretty sure I have heard the exact phrase "blah blah blah Than Bad blah blah blah" from several coaches...

 

Veering off topic, but oh well: I've been working with a G2 (soon to be G3) skier on my home lake recently, and she has outright told me I'm her favorite coach (beating Brooks Wilson which may cause my head to explode and is super ironic since I desperately need to get some coaching from him!). I'm almost sure the reason is that she's also one of these Obsessed With Why people. Again and again I think I've told her too much at a time -- only to have her ask 10 more minutes worth of questions!

 

So much comes down to learning style.

[Chef23]

@Than_Bogan that whole family is obsessed with why. Not that that is a bad thing.

[jimbrake]

@Gator1 - known fact: I think way more than just the right amount. It is likely better to feel your way through the course than think. I have skiing ADHD - "ooooh, counterrotation! Tight line! Level shoulders! Look - a buoy!!! Turn easy! Ski light with less angle! Ski with more angle and speed! More space! Wider! Narrower! Stand tall! Lead with the hips! AGGGGHHHH!" Please make the voices stop.

[jimbrake]

@Than_Bogan - remember, they need to be in W1, man.

[ForrestGump]

Topics such as this reinforce my belief that I could kill it in Girls 1.

[thager]

@JimBrake SQUIRREL!!!!

[bbirlew]

@thager,

That's me! Sitting in the water I'm going over my keys, thinking "hips (across the wake), elbows (pinned to the vest after the wake) and shoulders (level in the turn)."

Once I'm on the water all I seem to remember in the pass is "woo hoo!!! I'm skiing!!!"

[gator1]

@

[gator1]

@jimbrake‌ move to Colorado or wa. Anti ADHD treatment now legal

[SkiJay]

Here is some "why" for you to contemplate @Than_Bogan‌ and @gator1. The two main reasons a ski turns are rocker and tail smear. The more a ski is rolled up onto an edge the more dynamic rocker gets flexed into the ski while it's under cornering loads, and the less fin area there is presented to the water flowing past the tail (a ski rolled to 90° presents virtually no fin area to the water flow). So, the steeper the angle of roll, the tighter the carve and the less resistance to tail-smear there is, increasing the range of options the skier has over the radii of turns. During the cut, the same applies to the control of cross-course load and angle.

 

Hardshells provide the highest level of control over how much the ski is rolled up onto it's edges, and how consistently extreme edging can be held. But like all high performance relationships, there is a tradeoff. With more control comes a higher demand for correct inputs. Rubber is more forgiving of imperfect inputs and even imperfect water, and a little forgiveness breeds confidence, and confidence is king--so rubber is still in the game.

 

Ultimately, a skillful, supremely-confident skier with the high level of control hardshells provide will masterfully dial in just the right amount of roll needed through every phase of a pass. He/she will no more likely roll too much angle into the ski than load the rope too early or pull too long.

[SkiJay]

Coming at this from another angle; if you want your ski to roll less, run your fin shorter and deeper. The fin acts like the keel on a sailboat. The deeper it is, the more your ski will resist being rolled up onto an edge regardless of binding type. However, the current trend seems to be towards long-shallow fin setups; suggesting that over-rolling just isn't the problem this thread suspects it to be.

[Horton]

Nate...

[gator1]

@Horton‌ Mapple Torque

[Horton]

@Gator1 I think that is a whole different deal. In the same way flex is not the same as rocker.

[gregy]

Its exactly what gator is talking about.

[gator1]

@ gregy yep. You'd almost think I read the patent ap. But I didn't. You can't read those till they're issued.

[jimbrake]

@skijay - "rocker" = carve and "tail smear" = pivot (also referred to as "steering").

[SkiJay]

I'm not sure if you and I are describing the same thing @jimbrake. By "dynamic rocker" I was referring to how when a ski is loaded in a turn, the radius of its rocker is tighter than the radius of its static rocker while unloaded. The higher the load on the ski, the more it flexes, the tighter its tip-to-tail radius, and the tighter the arc it will want to carve. Tail-smear is a separate dynamic describing how loose the tail is while turning. The more up on edge the ski is, the more the tail smears/drifts. Both of these are directly affected by roll.

 

It's always seemed that the more control a good skier has over edging/roll the better. But if the new Mapple T Series is truly a game changer, maybe this needs a rethink. A few years back in Moto GP, they managed to make the bike frames so stiff that handling suffered. When they softened the frames a bit, lap times improved. The suspension damps low frequencies, the tires damp higher frequencies, and apparently the frame itself has to damp the highest frequencies.

 

Maybe a slalom ski that behaves more softly in torsion damps high frequencies in a similar way. Maybe softer bindings have a similar effect too. Maybe extreme edge/roll control can become a negative!?!

[Than_Bogan]

Maybe indeed. But I think the simplest aspect of this is that you can get BOTH of the effects you described earlier -- the fin effect and the edge effect -- at the same time if the ski can twist a little.

[Horton]

I am moderately dubious of this whole thread but

 

More speed with less load at the centerline means it is easy to control and flow out to the ball. Less load means more relaxed.

 

I have heard it speculated that Mapple (and other super elite skiers ) who look to have a massive lean at the center line actually have far less load than it appears.

 

@Than_Bogan feel free to throw math at this.

 

If two skiers have a 45 degrees angle path at the center line. No matter how fast they are going across the lake they are going 34 mph down the boat path. If Mapple is going 60 mph at the center line and I am going 50 mph at the center the boat is dragging me down course more per foot traveled than Mapple so I will have more tension on the rope. I will have more load and less control.

 

This is all the result of his center of mass being way more forward than mine and all the other stuff he does before the center line to make speed.

 

@MattewBrown I hope I did not make you spit your coffee on your computer with this post.

[Horton]

Ooooo so the whole point is the more speed you can get with less lean and load the better.

[gator1]

Nothing more entertaining then IT guys doing physics and dynamics. Go Than go!

[DanE]

@Horton Impossible to have the same angle path crossing the centerline if you don't have the same speed.

If you're talking about ski angle, well, I guess that is possible and then you would have more load.

[Horton]

@DanE‌ yes yes good correction. Ski angle at center line

[Than_Bogan]

I think you guys have basically got it. I wish I could write up a few pages of math and end with QED, but it turns out the "basic" equations of slalom are insanely complicated thanks to that evil skier at the end of the line and her dreaded "free will." Still, I can say a few things that may interest some:

 

One the more apropos portions of basic physics is that of a mass swinging at the end of a string. Since the mass's natural tendency is to continue in a straight line, the rope must provide acceleration to force it into a circular path. That acceleration (and matching tension) is along the string and its magnitude is given by m(v^2)/r, where m is the mass, v is the magnitude of the velocity (relative to the center), and r is the length of the string. Note that r in the denominator: that is one of the fundamental reasons that shorter line lengths are more difficult. A smaller r, even with the velocity exactly the same, requires greater line tension.

 

BUT the skier isn't kind enough to just be a rigid mass. So let's next imagine that our little mass at the end of the string has a handy rocket engine. He can use that rocket to push himself inside the circular path and make the string go slack. But perhaps of more interest at the moment, he can point the rocket exhaust toward the center and do his best to break away. Assuming the string doesn't break, his path may be unchanged (even considered over time), but he is significantly increasing the tension on the rope that is required to keep him in that path.

 

A skier can do the same. This may be easiest to understand when the skier is just hanging out behind the boat. In this situation, the "basic" physics above predicts the line tension is zero since the skier's angular velocity is 0. But of course the tension is not zero -- there's some drag which much be matched by line tension. And worse yet, the skier can add to it by rearing back and increasing drag.

 

When crossing the center line in a slalom run, the same is true. There's a certain minimum tension that must be supplied by the line to maintain a given path. But it's absolutely possible to add to that in a way that doesn't accomplish anything else.

 

Exactly how the ski's attitude, twist, fin settings, etc. affect this is waay beyond me. But it's clear that they could.

[mwetskier]

@Than_Bogan -its official now. the word geek in your signature line should be in all caps and under lined. not that thats a bad thing.

[Than_Bogan]

@mwetskier That's the restrained version...

[A_B]

Where should I be pointing my rocket?

[Andre]

Of course you all know that Jeff Rodgers just get out there and...ski ?

 

-Hoping i'm not the only one completely lost in such a discussion...

[Than_Bogan]

Those with actual athletic talent can and should "just go out there and ski." But each of us has to try to maximize whatever advantages we have and hide our weaknesses. I think Sun Tzu may have been the first to write that one down.

 

Any time I can make skiing become math, I have an advantage. Unfortunately for me, that is very rare.

[Horton]

I can count to 6

[gator1]

@Andre‌: I'm not lost. Here is a summary:

 

Over-rolling the ski on edge. Is it possible and is it bad?

 

I said yes and yes.

 

@Than_Bogan‌ said: "its too complicated to be mathematically modeled"

 

@Horton‌ said: "gator1 is probably talking thru his hat. And, the more the ski skids sideways during your pull, the worse off you are."

 

AND, meanwhile in late breaking news, Mapple's patent-applied-for new ski appears to cooborate gator1's theory of the downsides of over-rolling the ski.

 

AND...I still really want to talk to Andy about what he is doing. But, as a schmuck posting crap on the internets I have no illusions that will happen.

 

That is all.

 

Just pull harder.

[SkiJay]

Andy would definitely discuss this with you @gator1. He's a remarkably approachable guy. Give him a call.