What do you think you feel if not for the vibration of the tip of the ski?
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Ski Stiffness - Hero, Whiteout and #1SC Compared
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What do you think you feel if not for the vibration of the tip of the ski?
This conversation is getting even more interesting.
I don't believe that the vibrations I'm referring to are isolated to just the tip of the ski. These vibrations can be sourced from any part of the ski and felt through your feet. I would assume that vibrations at the very tips and tails would be more attenuated before they get to you versus those that are occurring directly underfoot. Whatever the source, it's clear to me that some ski constructions/materials are better at dissipating/eliminating these vibrations than others. Why else would many manufacturers include a rubber layer in their construction layups?
Why would Renoun and Sandwich Tech go out of their way to develop and market constructions that promote their anti-vibration capability? This is an important characteristic of all skis and the reason I mentioned it. If you truly want to extol the features of your ski finder service, then this is an aspect that I believe really needs to be included. It tells a part of the ski "story" that helps buyers better understand how the ski will perform without actually skiing it.
Thinking more about this, how difficult would it be to have a rig setup that has a sensor mounted on the top surface of the ski and then a way to introduce vibrations from the tip and from the tail? Being able to introduce vibrations at various frequencies would build a spectrum picture of how well the ski can attenuate those vibrations before they arrive at the binding.
Of course binding interfaces also impact what is felt by the skier. Some plates do a fantastic job of altering the feel of a ski. They Tyrolia Speedplate+ comes to mind. Also, each binding has it's own feel when it comes to the transmitted vibrations.
Of course binding interfaces also impact what is felt by the skier. Some plates do a fantastic job of altering the feel of a ski. They Tyrolia Speedplate+ comes to mind. Also, each binding has it's own feel when it comes to the transmitted vibrations.
Us older models are more fatigued by high frequency vibration than the younger ones.
You don't really feel it but you know after a couple of hours when you start hurting.
Plate systems definitely reduce high frequency vibration transmission as do thicker liners.
There are several good vibration frequency analyzer apps available for phones and I have one but have not tried it with my skis.
Structural engineers use an instrumented hammer to whack things to test vibration response.
Taping a phone with a frequency analyzer app to the bindings and whacking a suspended ski should give some interesting data.
You don't really feel it but you know after a couple of hours when you start hurting.
Plate systems definitely reduce high frequency vibration transmission as do thicker liners.
There are several good vibration frequency analyzer apps available for phones and I have one but have not tried it with my skis.
Structural engineers use an instrumented hammer to whack things to test vibration response.
Taping a phone with a frequency analyzer app to the bindings and whacking a suspended ski should give some interesting data.
And here I thought I was the only one who would rap a ski as well as hand flex and hand twist it. Sales staff always look at me like I'm from Mars when I do that. I never really paid any attention to the sound, just what it felt like when I hit it.
Tip vibrations are not attenuated by the ski construction before they reach your feet. Well, they are, but barely as a ski only has about 1-2% of damping... this is very small!! If something attenuate them it is the snow.
A lot of vibrations in skiing is coming from directly under your boot. You can't do much to change that. That is just an edge catching and releasing from the snow. No matter what ski you have (stiffness, mass, damping), that section will always behave exactly the same for the same motion on snow.
I am not arguing that some construction are not better than other. But they can be in many ways. Can you really say that you have been testing skis by isolating all variables beside damping?
The rubber layer is used to prevent the delamination between two materials of highly different stiffness (i.e., the steel edge and composite fiber). The rubber that is typically used in ski construction has relatively low damping compared to other rubber-like material. That is why they use rubber to make sling shot... it returns a lot of the energy you put in it!
You can read this: Comparative Study of Ski Damping Technologies by Accelerance Maps - https://www.mdpi.com/2504-3900/49/1/49. This is similar to what you are suggesting, i.e., vibrating a ski and measuring it. We use a instrumented hammer like Dakine is suggesting.
In that paper, we tested most technologies available on the market to damp skis. None really made a difference (beside one that involved putting a 300 g oil bag on your ski). We tested constrained layer damping by plastering a ski with that rubber/metal laminate. Doesn't do much in the lab. It is what is used in Rossignol VAS and it what it seems like Sandwich Tech is doing (not sure, their website is very vague). You can buy constrained layer damping material in many car shops to reduce the vibration/sound that your car body is generating. Buy some and put it onto your skis. It will improve its sounds response. You will also add mass by doing this, but it would still be interesting to see if you can feel a difference on snow. If it does, I will eat my tongue. And you won't need to buy expensive skis anymore, you could just add a few dollar of rubber to any model you like!
This paper also confirm that Volkl UVO technology doesn't change much in lab measurements and is not feel by skiers during blind on-snow tests: https://www.mdpi.com/2504-3900/2/6/305/pdf. I mean, the first version of their "damper" released to the public didn't even move in the right direction to expect that this damper could create damping! They changed the direction of motion in the following years!!
Head has an piezo and computer chip system to reduce vibrations on certain models. However, their own engineers showed that it doesn't really work or is realistic: https://www.researchgate.net/publication/245481344_Active_vibration_damping_of_the_alpine_ski. I seen on many models that the "chip" is now just a sticker. However, Head skis do feel different on snow... and they do something very different and interesting with the torsional stiffness. They locally boost the torsional stiffness of many of their model at the tip and tail.
Renoun... well... I will just say that I can't wait to see more about their methodology/results for what they claim is a 300% decrease in vibration with their tech. I am not saying that these skis are not feeling different on snow... after all, they are digging channels in the core and fill them with a soft foam... that can certainly change a lot of thing beside damping.
All skis compagnies need to have something to say when they try to sell you a ski. All companies will try to tell you that they have something to damp vibrations because it seems like something that people like to talk about (probably due to the importance of damper in car racing). Almost 100% of it is pure marketing. That is why we want to provide real measurements. For now, we start with geometry, EI and GJ. We could and will expand our measurements...
Let say we were to record the sound a ski make when we hit it in the store. That is easy to do, but it also brings a lot of questions. How do you correlate that to on-snow feel? Which part of the sound is important (e.g., the difference between a "thud" and a "ping" is mostly the frequency, not in damping)? Does it correlate to the lower frequencies that you will feel in your feet/body? We could bypass that and just put a wav file on our website so that you can hear the sound without going to a shop. However, can you convince me that it is worth investing in the sound recording equipment and spending the time doing that test for each of the 1000 skis we measure per year? How valuable is that information for you? How many "older models" out there want that info?
I feel there are better ways to reduce the vibrations that you feel through your body. I will write more about it later...
How do you hand twist a ski?
Tip vibrations are not attenuated by the ski construction before they reach your feet. Well, they are, but barely as a ski only has about 1-2% of damping... this is very small!! If something attenuate them it is the snow.
A lot of vibrations in skiing is coming from directly under your boot. You can't do much to change that. That is just an edge catching and releasing from the snow. No matter what ski you have (stiffness, mass, damping), that section will always behave exactly the same for the same motion on snow.
I am not arguing that some construction are not better than other. But they can be in many ways. Can you really say that you have been testing skis by isolating all variables beside damping?
The rubber layer is used to prevent the delamination between two materials of highly different stiffness (i.e., the steel edge and composite fiber). The rubber that is typically used in ski construction has relatively low damping compared to other rubber-like material. That is why they use rubber to make sling shot... it returns a lot of the energy you put in it!
You can read this: Comparative Study of Ski Damping Technologies by Accelerance Maps - https://www.mdpi.com/2504-3900/49/1/49. This is similar to what you are suggesting, i.e., vibrating a ski and measuring it. We use a instrumented hammer like Dakine is suggesting.
In that paper, we tested most technologies available on the market to damp skis. None really made a difference (beside one that involved putting a 300 g oil bag on your ski). We tested constrained layer damping by plastering a ski with that rubber/metal laminate. Doesn't do much in the lab. It is what is used in Rossignol VAS and it what it seems like Sandwich Tech is doing (not sure, their website is very vague). You can buy constrained layer damping material in many car shops to reduce the vibration/sound that your car body is generating. Buy some and put it onto your skis. It will improve its sounds response. You will also add mass by doing this, but it would still be interesting to see if you can feel a difference on snow. If it does, I will eat my tongue. And you won't need to buy expensive skis anymore, you could just add a few dollar of rubber to any model you like!
This paper also confirm that Völkl UVO technology doesn't change much in lab measurements and is not feel by skiers during blind on-snow tests: https://www.mdpi.com/2504-3900/2/6/305/pdf. I mean, the first version of their "damper" released to the public didn't even move in the right direction to expect that this damper could create damping! They changed the direction of motion in the following years!!
Head has an piezo and computer chip system to reduce vibrations on certain models. However, their own engineers showed that it doesn't really work or is realistic: https://www.researchgate.net/publication/245481344_Active_vibration_damping_of_the_alpine_ski. I seen on many models that the "chip" is now just a sticker. However, Head skis do feel different on snow... and they do something very different and interesting with the torsional stiffness. They locally boost the torsional stiffness of many of their model at the tip and tail.
Renoun... well... I will just say that I can't wait to see more about their methodology/results for what they claim is a 300% decrease in vibration with their tech. I am not saying that these skis are not feeling different on snow... after all, they are digging channels in the core and fill them with a soft foam... that can certainly change a lot of thing beside damping.
All skis compagnies need to have something to say when they try to sell you a ski. All companies will try to tell you that they have something to damp vibrations because it seems like something that people like to talk about (probably due to the importance of damper in car racing). Almost 100% of it is pure marketing. That is why we want to provide real measurements. For now, we start with geometry, EI and GJ. We could and will expand our measurements...
Let say we were to record the sound a ski make when we hit it in the store. That is easy to do, but it also brings a lot of questions. How do you correlate that to on-snow feel? Which part of the sound is important (e.g., the difference between a "thud" and a "ping" is mostly the frequency, not in damping)? Does it correlate to the lower frequencies that you will feel in your feet/body? We could bypass that and just put a wav file on our website so that you can hear the sound without going to a shop. However, can you convince me that it is worth investing in the sound recording equipment and spending the time doing that test for each of the 1000 skis we measure per year? How valuable is that information for you? How many "older models" out there want that info?
I feel there are better ways to reduce the vibrations that you feel through your body. I will write more about it later...
I did read that paper. I feel like we're going in circles here. Your response mixes the ski vibration concern with oscillation issues. I don't see these as being the same thing, but for some reason I think you believe they are directly related (or maybe even the same thing). Most of the tip devices you referred to from the paper are not for decreasing ski vibration. They are for decreasing tip oscillation. You really should have a discussion with @Cyrus Schenck of Renoun to better understand the ski characteristic of vibration that I'm specifically focused on here. The Head EMC system is also supposed to reduce vibration and they had an elaborate demonstration system at the ski show last season to show how the vibrations of the ski were reduced when the EMC system was enabled. It's too bad their new EMC enabled skis don't actually feel damp when skied.
It's interesting that you brought up the car sound & vibration because that is exactly what I'm getting at. Most cars that "ride quiet" are generally more expensive luxury brands. Similarly, skis that also ride quiet are perceived by skiers as being more "luxurious". It's like having a car with bad tires that create a ton of road noise and vibration into the vehicle versus one that rides super smooth with little road noise and vibration. Which skis provide the "luxury ride"? That's what your data is missing.
@AlexisLD - take a look at the Head 2021-22 catalog that was just released. Note on page 16 how they refer to the (#9) rubber layer they include in the construction layup as a "dampening layer". Pages 40-41 show all of their core constructions. They almost all have the "dampening layer".
www.zuzupopo.com
Head - zuzupopo / Catalogues - zuzupopo
I grab it with one hand at the boot centre mark and another hand near the tip and apply torque. How much I can twist it tells me how easily it will give up hanging on in a turn. I have or at least used to have strong hands. How badly I cut myself if I do it without wearing gloves tells me how sharp the edges are
.I don't have nearly the data trove you have, but my anecdotal data tells me that Fischer's "Frequency Tuning" really works. I suspect from grade 12 physics it might have something to do with where they put ridges to change the natural frequency of the skis resonant harmonic oscillations.
Well, in my world, vibration = oscillation. You can look here: https://en.wikipedia.org/wiki/Vibration. "Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point.". So I am not too sure what you mean. Do you just mean that what you are talking about is at higher frequency?
You can look at the websites of most of these device, and they all clearly state that they are there to reduce "vibration":
- https://floskis.com/products/floshocks-system
- Rossignol VAS = Vibration absorption system
- etc.
I am happy to measure Renoun's skis.
If Head EMC doesn't work, wouldn't it kind of prove the point that damping doesn't help?
A lot of money is poured into making for a quiet ride. The reason for that is so that you can hear better the music from your expensive sound system or talk on the phone. None of that is really relevant to skiing.
Do you feel that the StormRider 88 is significantly different from the Brahma 88 (Or the SR 95 to the Bonafide)? Do the Stockli's skis feels significantly more luxurious (beside the price tag)?
Then there is torsional vibration.
If that isn't well damped the skis will chatter like hell.
And mixed modes.....
If that isn't well damped the skis will chatter like hell.
And mixed modes.....
Well you clearly are not a vibration zealot like some of us around this forum. So I'll agree that vibrations are just higher frequency oscillations, but in the real-world these are two very different ski characteristics. The ability of a ski to remain "composed" and hold a strong edge is directly related to its ability to reduce the oscillations along its length. However, none of that has anything to do with the teeth rattling vibrations that some skis will readily transmit versus others.
Any device placed on the tip of the ski may indeed reduce vibrations sourced at that part of the ski, but I don't believe that they're doing anything for those that are coming straight up into the ski from directly underfoot. That's why technology from Renoun like Vibe-Stop is really ground breaking for ski construction. Head's EMC doesn't prove that damping doesn't work, what it proves is that EMC isn't a very good system for damping their skis.
I'm quite surprised that it seems you don't differentiate between skis you have ridden that have differences in their ability to damp vibrations. This is one of the first things most testers will talk about upon getting a lap or two on the skis. How do they feel on the snow? Are they smooth and quiet or are they harsh and loud? The whole reason we've gone down this road is because if I'm going to pick a ski purely based on data, then this vibration/damping data is something I would need to know before buying. It will tell me an important part of the "ski's story" that improves my enjoyment factor when skiing.
BTW - A lot of folks on this forum will tell you from firsthand experience that the ride quality of a Stockli ski is clearly and obviously better than most other skis they've ever used. What Stocklis have you skied?
I grab it with one hand at the boot centre mark and another hand near the tip and apply torque. How much I can twist it tells me how easily it will give up hanging on in a turn. I have or at least used to have strong hands. How badly I cut myself if I do it without wearing gloves tells me how sharp the edges are
I don't have nearly the data trove you have, but my anecdotal data tells me that Fischer's "Frequency Tuning" really works. I suspect from grade 12 physics it might have something to do with where they put ridges to change the natural frequency of the skis resonant harmonic oscillations.
That is interesting. I tried before and couldn't get interesting results. I tried again. I need to grab it in a specific way and I would say that if I look at how much the ski twist, I can get an idea of their torsional stiffness for very soft skis. I can't get much useful informations for my torsionally stiffer skis. I seem to be able to distinguish my girlfriend first skis from my own skis, but can't really say anything within my ski quiver. Maybe I need more practice... or a machine!
Couldn't find anything about the Fischer's frequency tuning beside that it is supposed to include fibers that create energy.
I would even add that it is all mixed modes if you are able to put a ski on edge. The only way you get pure bending or torsion is when the ski is up in the air. That doesn't happen very often for most skiers but some people care. Park/freeride skiers don't like to have a soft ski with a large portion of the mass at the tip/tail. Beside increasing the swing weight and making spinning harder, it will also create a very slow oscillation frequency of the tip that will take time to damp out (slower frequency take more time to damp out) and create more forces at the boot...
@AlexisLD - take a look at the Head 2021-22 catalog that was just released. Note on page 16 how they refer to the (#9) rubber layer they include in the construction layup as a "dampening layer". Pages 40-41 show all of their core constructions. They almost all have the "dampening layer".
Head - zuzupopo / Catalogues - zuzupopo
Most skis companies use this construction with VDS rubber on top of the edges. It is primary used for bonding: https://www.snowboardmaterials.com/index.php/articles/item/45-about-vds-foil-rubber-foil. If it was creating a much better ride, and people would care, all compagnies would use more of it. You can easily cover the full ski with it as it wouldn't add much weight (1200 kg/m^3 x 2 m length x 0.1 m width x 2 layers [top and bottom] = 100 grams) and would cost them only a few more bucks.
Funnily, Stockli seems to be using full-length, full-width rubber layers in their skis ( ... I assume the black sheets around 1:13 are some kind of rubber). This is only the second time I see that (but I am far from an expert on skis layups), the other company being Crosson. I also found that the Big Horn Sego is using this too. There are probably other nice things in Stockli's skis, but it would be funny if a little bit of rubber was what makes people rave about their on-snow feel!
Nothing is new about that, it was used in early Head skis (in the 60s). Interestingly, Rossignol in their VAS patent claims that putting so much rubber in a ski render it lifeless. The VAS is the localized use of this rubber. Glenne's article (K2) says that it doubles the damping of some vibration modes, but it still remains a very small damping increase w.r.t. what the binding, boot and snow contribute.
I remember reading that Kastle also uses the rubber layer for damping. No one in this thread is talking about Kastle. Any thoughts or comparisons with Stockli?
Well, I was trained to run away and search for better snow when I can ear my skis scrapping the ice. I tried the SR95 briefly and they didn't strike me as much different than other skis when I tested them. Maybe I didn't had the conditions to make them shine. There are a lot of ski with very similar bending and torsional stiffness patterns to the SR88 and SR95 (contrary to what is said here). If you don't care about "teeth rattling vibrations", then I am not sure there is anything special about them (ok, Swiss built quality). If you do, and I am learning that some people do, then they might be special and I agree that this information is helpful.
I think we are getting somewhere. Basically, I would describe the difference between what we are saying as this. Oscillations like you define them is about the motion in flexion or twisting of part of the ski following different modes and frequency. I would call them bending or torsional vibrations. These vibration happens at many frequency and they depends mostly on stiffness and mass distribution (not damping as it is very small).
What you seem interested in is how an impact on the underside of the ski, kind of directly under your foot (otherwise it would create oscillations/vibrations in that part of the ski) is transmitted to your foot. That is not a vibration. This happens when the underside of your ski drifts and catch-and-release with the snow. The frequency of that is driven by the weight of your foot/boot/ski, the stiffness of your leg, the mass of your upper body, the edge angle, the snow, etc. I would generally think that the ski construction changes nothing to that frequency ( around 5ish Hz).
However, when I discovered that Stockli put two full layers of rubber in their skis, that got me thinking. If you put a soft layer between your foot and the ski, you will not change the total impulse transmitted (the integral of force x time) but you will spread that force over a longer period of time, reducing the peak force. It is basically as if you are thinking of the ski as being vertically soft/squishy. I am a little surprised that thin layers of rubber could do that (not sure of their thickness), and would think that investing in a better boot liner would help more than adding rubber to a ski (not with the sound that your ski make when you ski it, but with the comfort you feel), and I am surprise that people can feel a change in that (but maybe your bones/joints could after a full day of skiing), ... But if you tell me that you can feel it on snow I believe you (I am just trying to understand exactly what you feel). I am not 100% sure if this squishy behavior could help reduce vibrations at the tip/tail. It might, but I need to think more about it.
Is my understanding correct?
All this is interesting because you can think of different levels of complexity to describe a ski:
1. One rigid body: mass, shape
2. Many rigid bodies (mass, shape) connected through bending and torsional springs (and damper... that I still consider as mostly irrelevant)
3. Many soft bodies connected to each other...
Sooth has been operating at level 1 and 2 for now. The industry in general barely does #1.
Now we would need to measure what you feel/describe. Material "squishyness" is somewhat related to the sound at impact so I can see that there might be a correlation there (and Francois' way of measuring the resulting vibration with its hand after such impact would probably not work... this is more about the vibrations). We could also measure the force profile during the impact. Anyways, I need to think about ways that would work on most skis and what it would involve to deploy that.
Any other skis that would fit the same category as Stockli's skis? This video talks about the Liberty VMT construction being comparable. Would you agree? From what I can see of their construction, it doesn't involve any squishiness. What about the Blizzard Bonafide and Brahma? Any skis that would be the complete opposite of Stockli's quietness? I am curious, because if we want to measure something and verify that the measurement works, we need a list that people agree on...
We are probably just having different reference groups. To me and my friends, a quiet ski is not that important. We must have tick feet and a lot of hair in our ears. One of my good friend also always scream when he ski, so I can't hear much else! I read/listen to pretty much everything I can find on Blister, SkiEssential, OutdoorGearLab, and other review sites. This is the first time I hear about a ski being "harsh and loud". I never seen that kind of question asked during a ski test. I can't find anything interesting in Google with the keyword "ski harsh and loud" and not much with "ski quiet". I would go ski to feel it if I could, but I am out of commission this winter. Smooth is a confusing word that can easily be associated to the tip/tail geometry engage or how the deformed shape interact with the snow. Damp is even more confusing as some people talk about "suspension", some about "speed limit", some about real damping, some about the ability of a ski to not-generate vibration when drifting, some mean stability (which in itself can have a lot of different meaning), etc. I am trying to clean that up.
It seems that I stumbled into the den of Stockli's skiers where "quiet" is the God. That is OK, I am happy to learn new words and start using them! Thank for sticking with me. ;-)
It's amazing how loud fans of quiet can be.
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