Towline Tension

Edbrazil · December 2017

Anyone out there have some information to contribute, about how much towline tension a SL skier generates?
Some years back, Dave Benzel had a computer-interfaced system, that measured tension and other factors.
I did some work at times with a Dillon Force Gage. Eay back, Jim Sylvester (AWSA President, Technical Committee)
did some measurements in the 1960s.

I have heard a figure in the range of 900 lbs. max. Don't know if this is accurate; sounds like a lot.

A_B · December 2017

That system was called LISA and there was an article in Spray or WSM. 900 was the max that Andy put on the line at 39 Off right behind the boat. The plotted pull force started with deepwater starts, which also put a fair amount of load on the line.

I am only guessing, maybe 250-300 pounds if I am remembering right. One thing that stood out was how consistently Andy peaked and where he peaked compared to some other decent non-Pro tournament skiers. There was quite an increase as all skiers headed into the wakes.

I wanted to get a copy of that article but WSM doesn’t have back issues, and had posted the approximate date of the article before, requesting all those guys who still have stacks of old magazines to look for it.

The only magazine I had was one where Benzel ski school was advertising to “come ski with LISA”. Not the article.

I’d love to see the article if any Ballers can post a copy.

ALPJr · December 2017

I think Syderhoud measured the lbs of pressure on the rope in the West Coast Slalom video with Marcus Brown and Terry Winter.

6balls · December 2017

In college when I was stronger and skied even more improperly than I do now I used to go through about 3 straightline brand ropes/year that were tensile rated at something like 1000-1200 lbs.

Always carried a new one in my trunk in case I skied with friends so I could give them a rope after (often) breaking theirs. Broke two in one day once and broke one at collegiate regionals. When I was a kid @razorskier1 broke three in one day--the one we were using, our spare, and the one we bought at the marina that day cuz we were out of ropes.

My guess is with all the understanding of efficiency now the amount of line tension on top skiers may be less than before? Dunno, in any case I bet it's still a very big number.

eleeski · December 2017

If I remember right (it was back in college - a LONG time ago), just riding a trick ski was about 75 pounds pull, the smoothest O was 150 and a sideslide was 25 pounds. Any wake trick or hard pull went off scale on our 500 pound max scale.

Remember the Saf-T-Pop automatic trick release? With such wide variations in load, no wonder it didn't work.

@6balls Ropes are much better nowadays. You braggart. (I'm still impressed.)

Eric

pregom · December 2017

I'd like to see visualizations of the pull force through a pass in the course. Maybe something like this GIFwith the rope that changes color as the load gets higher? Or a 3D plot where the x- and y- axis represent the handle path and the z-axis represents the load? and all this with real data coming from different skiers?

AdamCord · December 2017

@tap

Jordan · December 2017

Wondering if modern skis are more efficient at turning resistance to the boat into acceleration and therefore reduce tension on the rope?

mwetskier · December 2017

buy borrow or steal a copy of suyderhouds ' west coast style ' instructional video. theres an entire section on video analysis of terry winter and marcus brown skiing shortline and some of the clips have a time readout and strain gauge window that give real time values of elapsed time and rope loads. that may very well be some of the most accurate and reliable data you will ever find on the subject.

tap · December 2017

I've measured skiers anywhere from 400 to 700 lbs. force across a pretty good range of skill level. In general, the better the skier the smoother and higher the load.

Some previously posted data.

mwfillmore · January 25

Resurrecting this thread @tap @AdamCord can we see what kind of hurt @adamhcaldwell puts on pylon

MDB1056 · January 25

Didn't they just measure that at the last couple of majors as some new stat? Thought J Travers took top slot with some ridiculous amount of pull

AdamCord · January 25

@mwfillmore he pulls hard but not as hard as @FWinter

Dacon62 · January 25

Whats going on here? That is a heck of a lot of load/weight. There is no way I could hold almost a 1,000 lbs in my hands if I was standing straight up with good posture.
In the West Coast video I recall that 400-500 lbs was the max measured range. It went up slightly with each shorter pass. How did we get to 900+ pounds. Is the way the load is measure in the post above measured differently?
Does the boat provide some of the measured load as it moves forward. Obviously, it does provide load that is how cross course speed is generated. I guess what I am asking is only half the load amount felt by the skier because the other half of the load is taken on by the boats forward momentum?? Anyone understand what I mean?

elr · January 25

Interesting that 2 of the 3 scores into -41 were at the bottom of the list.

Dacon62 · January 25

lighter guys, less swing weight I'm guessing.

ReallyGottaSki · January 25

Yes although the raw numbers remain impressive, I'm sure it's been mentioned normalizing the measured peak force to body mass better delineates some skier efficiencies in accelerating. Also a skier maintaining less peak force but for over a longer duration can apply more total power , and if applied in the right locations, accelerates in better shape and gets to the buoy earlier.
Also a 'save' on a turn/cut can really load the line so one would have to be certain to compare only 'normal' turns and trim the flyers for all groups, analyze what is typical before any technique and style comparisons

@Dacon62 , I believe it's legit, the force is the same both ends of the rope, else there would be separation of the two points occuring. Their movement relative to the observer is not a factor, and the ropes mass is negligible

aspski · January 26

Mostly you can endure it for very brief periods of time. If it was several seconds no way, but 1000lb for 0.01 seconds the human body is capable of that. I remember seeing sports science clips showing forces of skiers and snowboarders landing large terrain park jumps. The force of landing was 2,000-3,000 lb in some cases, but only lasted for very brief period of time.

Than_Bogan · January 26

It's surprisingly important how long the measurement is integrated. Otherwise, what a person would call vibration and/or "instantaneous" deformation can register as a massive peak force.

That said, it's pretty sensible that if 500 is routine for these guys, then somewhere around double that would breifly appear during an Oh Crap Moment!

So my hunch is the measurement interval on TWBC stats is reasonable.

buoyboy1 · January 26

I have always wondered why TWBC rewarded the highest rope tension load since it takes more skill to NOT peak ZO and try to stay as light/invisible as possible. TWBC should take the 39 off pass for men and 38 off pass for women and use the smallest load number to determine the "smoothest skier" award. I think we all are really good at spiking ZO when we are in scramble mode.

chrislandy · January 26

@buoyboy1 I think it's more that the rope sponsor can prove the tow line strength, although I did notice that towards the end of the season they changed it a bit so it wasn't just the highest tension, wasn't it highest tension "while in control" or something like that?

adamhcaldwell · January 27

I completely disagree that the goal is to be "light on the load" and that HIGH numbers are bad. Efficiency in this sports has absolutely nothing to do with being "light on the line".

You don't have to be scrappy and out of control to spike the boat and/or create load.

"Efficiency" doesn't mean being 'easy' on the pull. To me, Skiing the course efficiently means to use the mass, energy, and power of the boat to do the work for you, and to be in a body position that can handle the forces without compromising your body and subjecting yourself to injury .

During the Malibu open, 'peak' load for me occurred at 3 ball on my 38off pass - a hair under 900lbs. When I saw that on the monitor it was almost comical to me as it was one of the easiest 38s I have probably run in a tournament.

By EASY - what I mean is I was WAY up course, running a super early line with a lot of width, angle and energy moving through the back of the ball. Just how I like to ski.

The high 'load' doesn't mean I took a hit, OR that I was working hard. It just means that I was in a ridiculously strong position on the back of the ball with a lot of direction/momentum going to CL, but not a lot of down-course speed. The "load" registered, was merely the boat accelerating my mass to CL while I just stood there to take the swing into CL. I didn't even feel the 890lbs that was recorded.

What I DID feel, was the hookup at 1 @41off (and I still felt it 3 days later). I was crushed on the back of the ball because my hips were back due to a mistimed swing off the second wake putting me super narrow at the ball. I just was not anywhere near the right body position to handle the hookup and had to work ten times harder to survive the swing to 2 ball. The load on my body was nearly too much to handle and recover from.

Conclusion: There's a ridiculously huge discrepancy between "perceived" load versus "actual" load. Poor body position will magnify the perceived forces and load on your body, whereas and 'ideal' body position will minimize them.

AdamCord · January 27

But I thought I was supposed to hide from Zero Off!!

JackQ · January 27

I think many skiers look at this the wrong way, it is not so much peak load. It is the "area under the curve" the pull from the ball to CL, not just one point (peak). No one is going to run 39 off by just standing up after the buoy.

The goal in my experience is to get as much angle and load at the buoy you can "comfortably" maintain to the centerline, better to have a little less than more. Typically though many skiers bite off more than they can maintain, spike line tension, ZO reacts and they get pulled up or out of position.

Horton · January 28

@adamhcaldwell Here is how I see it. Tell my if you disagree.

I want as much angle as possible and I need take enough load in the rope to maintain this angle but any load in excess of what is needed is to my detriment. Excess load in my hands at centerline diminishes my ability to stay in control after centerline.

Assuming I leave the ball in control and in position it is generally not to my advantage to drive my upper mass farther away from the boat approaching centerline.

( I am not talking theoretical ideals what might work for a SUPER ELITE skier trying to run 41 or get some at 43. I am talking about the rest of us mortals. )

slow · January 28

Well said

adamhcaldwell · January 29

@Horton -
Angle
"I want as much angle as possible and I need take enough load in the rope to maintain this angle but any load in excess of what is needed is to my detriment. Excess load in my hands at centerline diminishes my ability to stay in control after centerline."

The purpose of "angle" through the finish of the turn is fairly simple and straight forward. To decelerate down-course speed to maintain an EARLY line back to center. Period.

You only need angle one time - and thats through the back of the ball. Once downcourse speed is bled off and your connected into the pull, there's no need to work to try to build more. Swing speed is what will get you early to the other side, you just need to put the body/ski into a position to accelerate effectively. To get acceleration and swing speed doesn't mean you have to load excessively by any means. It just requires more awareness of our position on top of the ski.

Excess or unproductive load is almost always caused by a body position of top of the ski that has turned the ski into a tail digging anchor rather then a high speed planning hull. In addition, being 'separated' from the handle often creates 'overload' when crossing CL. If we can use the mechanics of the system to our advantage, then we should be able to attack into CL as aggressively as we want, without any negative overloading side effects. The speed and trajectory away from CL will ultimately govern if a heavy load will lead to loss of control or a more productive up-swing.

Upper Mass
"Assuming I leave the ball in control and in position it is generally not to my advantage to drive my upper mass farther away from the boat approaching centerline."

For sure..... If under control out of the turn, and you are going to hit CL early enough to have space and width into the next ball, you don't have to be as "aggressive" in your body lean/pull to keep the pass and energy going. But if being more aggressive in this situation causes a problem, the its probably highlighting something you can work on before you shorten the rope.

I look to drive my "upper mass" but not away from the boat. Instead - I am looking to drive it both away from the ski aka "standing up" and also out beyond the edge. The goal is to have the upper mass both high above the water, and away from the boat - but moving in relationship to the ski at all times.

Moving the shoulders 'away from the boat' is the wrong frame of reference. In one moment "away" from the boat might create an ideal position at the initial hookup, but a fraction of a second later the ski has built angle/direction or speed and left you in the back seat before you hit CL and leading to a overloaded/uncontrolled position. No bueno!

What I am looking for is that a skier is to be 'stacked' with the leading shoulder crossing the centerline a fraction of a second before the feet do - and then continuing to keep that leading shoulder moving out over/above the feet past the outside edge of the whitewater. The later is hard to accomplish, but pays dividends as the rope gets shorter.