Ski reviews: Qualitative vs Quantitative

[endre]

We are still measuring around 100 pairs of skis every year, most of the data is on skitest.com. SFI is a norm adjusted to the average ski stiffness, five segments of the ski, 5=average back to front. (So a SFI 86432 would be stiff in the back and soft in the tip) We have been publishing these and a lot of other data in Fri Flyt every year since 2006, a lot of the stuff posted in here is really old. Still doung it though, and it is available if you pay for it I guess.

[endre]

Sorry, My bad. seems like they have taken down the info. Will find what happened to it and get back to you, if not I will dump it on www.eviski.com

[endre]

You will find all the data and a review in norwegian if you follow the link to FriFlyt.no. This should be more easily available internatinally imo.

[waxoff]

We are still measuring around 100 pairs of skis every year, most of the data is on skitest.com. SFI is a norm adjusted to the average ski stiffness, five segments of the ski, 5=average back to front. (So a SFI 86432 would be stiff in the back and soft in the tip) We have been publishing these and a lot of other data in Fri Flyt every year since 2006, a lot of the stuff posted in here is really old. Still doung it though, and it is available if you pay for it I guess.

I'm curious about how the definition of average stiffness is established. Is that something that has changed/evolved over the years as more skis have been tested, or has it always been a fixed value?

[endre]

I'm curious about how the definition of average stiffness is established. Is that something that has changed/evolved over the years as more skis have been tested, or has it always been a fixed value?

It is a fixed reference now, it is based on the first three years of testing (2006-2009), but as it is interesting to compare skis back in time and also track development of flex curves we fixed it. The average skis of 2020 seem to be a tiny bit softer than an average 2010, the 2010 would be a 55555 and the 2020 is probably near a 55554 (Have not done the actual math on that). The selection of skis and the size of our categories have also changed over the years, so numbers are not directly comparable. We measure more light touring skis in 2020 than 2010, so a softer average flex is expected. The point of the SFI is that you can directly compare a 2007 something 193 to a 2021 something 176.

[waxoff]

Great info, thanks! I used to have access to skitest.com and found the flex index helpful as a comparison tool. Good to know about the science behind it.

[alude]

In my mind, "damp" describes a behavior more than it does a more quantitative word. The problem with using a quantitative word like, "7 stiffness" to try and describe "damp" is that there are many other things that can play into making s ski damp. Camber is a good example. Take a ski that's "7" and has 5mm of camber in it, then compare it to a ski that's "6" but is completely reverse camber. Which is gonna be more damp? Probably the second one. You will absolutely get a lot your energy out of the cambered ski because (if you're skiing well) you're bending that ski into an arc shaped in the opposite shape of what it was molded as. The ski will try and return to that original shape, thus giving the ski a very lively, energetic feel, even though it's stiffer. Thus you have two different qualities both "stiff" and "damp" and the two can vary from one another quite a bit. They can also vary a lot depending on conditions.

Which one would be more damp on groomers? Would it change when you're skiing the ski flat vs. on edge? Things start getting complicated and muddled when you lose sight of the context. What's funny is our brains make sense of things without us being consciously aware of it. The Shiro is a good example: I would also describe the ski as being damp. I also would prefer that ski in a lot more snow than I would a narrower ski. There's the context - the Shiro is a pretty damp ski when you're in softer snow. If you ski it flat on a groomer it probably won't be as damp as a ski with more camber would be. Yet all these details I don't really have to explain for our brains to make sense of it, IF I get the context correct.

That is super interesting, but I simply think that the word damping is overloaded with different meaning. That is why you need to have the context, and why just getting a "this ski is a flex 7" doesn't help you. With the contexts described, I can think of two different definition for damping. One is how much input a ski gives you for a given terrain (e.g., powder, bumps, etc.). The other one is more related to the pressure distribution on the tip. If there is a lot of pressure on the tip, you can ski to a higher speed before the tip starts flapping around. Both effects, and many others, can be calculated/described from ski measurements.

So to get back to the meat of the subject. As far as I'm concerned, I think I prefer more qualitative descriptors more than I do quantitative. But, it rides on the expectation that whoever's reviewing a ski gives some background - what the ski's designed for, how heavy they are, what type of skiing background they have, as and where did they test the ski? If the context is there's I can usually understand what they're talking about.

I agree, this is the holy grail (as is testing the skis yourself). But you need to find a person that is a good match for you and where/how you ski, the ski you are interested in (model and length) and can describe the context sufficiently well for you to understand what they mean. It is not always easy. If 190 cm skis are not your things, it is a little hard to relate to Blister's reviews... shorter skis do not necessarily feel the same as longer one.

TL;DR: context is everything IMO. Skiing is too dynamic and complicated to quantify everything

A ski is really not that complicated. If we can come up with a list of on-snow feels with associated context, I am sure we can find a way to quantify it. You can then judge if they are useful or not... :-)

[alude]

Rocker profile also affects the suspension of the ski though. For the sake of this example lets take the exact same ski but one is fully cambered and one if fully rockered. A fully cambered ski hits a bump with the very tip of the ski and flexes the entire ski up to your boot to absorb it, a fully rockered ski hits the bump much closer to your boot, where the ski is typically stiffer and the leverage of skier is decreased to flex the portion or ski left between the boot and the bump. This leads to different feels on snow even if in the lab the skis would test exactly the same for stiffness and other measurable variables.

How are both feeling different? I understand the different situation, but I am not sure about what you perceive...

A damp+heavy build will be a monster truck and let you ski variable snow like a hero. But once you start trying to be playful, like catching small airs, popping off lips, throwing tricks. Or even skiing something like a pillow line that involves a lot of direction changes and quick movements, those type of skis become way less fun that something lighter.

On the other end of the spectrum is light and energetic, if you want to take it really far think of a carbony touring ski that weighs like 1300 grams. This ski sucks in variable snow. But in perfect pow skis that light perform really well and are super easy to move around. A very dynamic skier who absorbs a lot of the terrain with they’re legs, or uses the terrain to stay off the ground as much as possible will get along with a lighter and more energetic ski build than someone who likes to stand on their skis and arc turns through any snow conditions in front of them.

Super interesting. It makes total sense that a heavy+soft ski will be unpleasant in the air. Beside the more mass that you will have to move in the air (e.g., inertia in rotation), the tip/tail will keep oscillating with large amplitude and for a long time. You will feel that in your boots.

A light+stiff ski will be affected by variable snow both because of the lack of mass (more mass = less momentum change to the ski during impact) and the high stiffness (high stiffness = more of the ski momentum transmitted to the skier).

[alude]

We are still measuring around 100 pairs of skis every year, most of the data is on skitest.com. SFI is a norm adjusted to the average ski stiffness, five segments of the ski, 5=average back to front. (So a SFI 86432 would be stiff in the back and soft in the tip) We have been publishing these and a lot of other data in Fri Flyt every year since 2006, a lot of the stuff posted in here is really old. Still doung it though, and it is available if you pay for it I guess.

Endre, very inspiring work! But I always wondered why you don't measure the torsional stiffness? We found that skiers are generally more sensitive to torsional stiffness, and that the torsional stiffnesses vary much more than bending stiffness in the skis available. For example, slalom skis have typically very similar bending stiffnesses distribution, but widely varying torsional stiffnesses across brand and depending on if they target beginner or expert skiers...

[waxoff]

A light+stiff ski will be affected by variable snow both because of the lack of mass (more mass = less momentum change to the ski during impact) and the high stiffness (high stiffness = more of the ski momentum transmitted to the skier).

And on top of the above: A light and stiff ski is more likely to e.g. transmit high frequency vibrations to the skier. Not that it necessarily will change how the ski performs, but it will change how the skier perceives the ski. This experience will vary from skier to skier, depending on ones preferences of the matter.

[alude]

And on top of the above: A light and stiff ski is more likely to e.g. transmit high frequency vibrations to the skier. Not that it necessarily will change how the ski performs, but it will change how the skier perceives the ski. This experience will vary from skier to skier, depending on ones preferences of the matter.

I am very curious about that... do you guys think that you can feel the high frequencies of a ski directly? Beside the first bending mode of a ski at around 10Hz, the other vibration modes are at around 50 (2nd bending), 80 (1st torsion), etc. To give you an idea, you can try this: https://www.youtube.com/watch?v=bslHKEh7oZk

Do you think you feel the vibration, e.g., the amplitude or frequency change? Or do you feel some other effect resulting from the ski vibrating like the lost of edge grip, change of direction, the sound it makes, etc? Or maybe even some other effects not necessarily related to vibration, like the ski being pushed all over the place by rough snow?

[skibrd]

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