All this assumes that stiffness is all that matters in judging ski life…
Bending and torsional stiffnesses measurements are both within 5%. We measure stiffness distributions, so all along the full length of the ski.So are torsional stiffness measurements not precise enough to show a difference? There’s little doubt amongst long term skiers that skis lose their grip with advanced age of use.
Where would you measure it? I’d imagine measuring torsional stiffness in front of the binding piece is not easy.
Bending and torsional stiffnesses measurements are both within 5%. We measure stiffness distributions, so all along the full length of the ski.
The original idea (one of them) was that we would measure a ski from the factory, and that stiffness changes would be >20%. We could then easily compare skis out there to the reference. But we never found that to be true...
On thing that can change with use is camber. I also agree that torsional stiffness is part of the equation that described edge grip, but it might not be the only thing. If torsional stiffness doesn't change with time, it must be something else.
All this assumes that stiffness is all that matters in judging ski life…
That's what you're implying here, correct?
On thing that can change with use is camber. I also agree that torsional stiffness is part of the equation that described edge grip, but it might not be the only thing. If torsional stiffness doesn't change with time, it must be something else.
It's the torsional stiffness that is the most difficult to see of test by hand. That's the one that needs specialized equipment for measurement.
This sounds like a little experiment that I have never done in any sort of controlled way but that might support my superstitions. I typically mark skis L and R, ski them that way most of the time, then if I need some extra edge grip (very icy), switch them - but only if I'm fairly sure I won't hit any rocks, etc. My spurious logic had been to concentrate the edge dings / wear and tear on one set of inside edges, keeping the other set cleaner. But this spurious logic is a bit undercut by the fact that I often ride the inside ski too much. I hadn't considered whether there could be any long term effect on material stiffness that would be specific to one side of a ski vs the other. Who knows.Strange thing happened today. Took out an older pair of FIS SL today. Ski had about 50 days on them. Skis have nose picker tips. The skis had a fresh base grind and my usual hand tune. Normally, the skis are skied with the nose pickers pointing in. So there is a definite preference which edges are the inside edges.
Snow was very firm today. Skied the first run with nose pickers pointing in. There was definitely a lack of grip feel. Second run, the same lack of grip feeling persisted. Switch skis left to right (nose picker pointing out) on the third run. Felt an improvement with grip.
Half way through the day, switched back. That lack of grip feeling returned. Switched again. All is right with the world again. Finished the day with the nose picker pointing out.
Hmmm.
☝Placebo is strong. If you have faith in your gear, it miracolously holds better. It is a fantastic thing
It's only a "placebo" until it can be quantified via scientific measurement. We're getting there thanks to the folks at SoothSki. They're already providing a ton of valuable data and I believe that given some more time, we're going to see these questions get answered regarding the life span of skis and how they change over that time.
As I said before, we measured the "wear" on a few skis. We didn't find any change in stiffnesses. Can I say that nothing change? No, nobody could say that with such experiment. One could always come up with one more thing that you could have measured, or different test conditions. I just know that continuing this experiment would be very difficult/long, and there is a good chance that we would not find anything again. I was asking you guys to provide reasons to tackle this so that I can change my mind about this!
Strange thing happened today. Took out an older pair of FIS SL today. Ski had about 50 days on them. Skis have nose picker tips. The skis had a fresh base grind and my usual hand tune. Normally, the skis are skied with the nose pickers pointing in. So there is a definite preference which edges are the inside edges.
Snow was very firm today. Skied the first run with nose pickers pointing in. There was definitely a lack of grip feel. Second run, the same lack of grip feeling persisted. Switch skis left to right (nose picker pointing out) on the third run. Felt an improvement with grip.
Half way through the day, switched back. That lack of grip feeling returned. Switched again. All is right with the world again. Finished the day with the nose picker pointing out.
Hmmm.
Hyvää!
All FIS SL skis are torsionally stiff; might of course differ a little (also from pair to pair) but they're all about as stiff as alpine skis come in that respect. Longitudal flex will vary in pattern and overall but they are all somewhat stiff. They all grip if edges are sharp (and you ski them the right way) but have a different feel to them (I haven't enough experience in all brands and year models to give a fair overview, someone like @Scotskier perhaps?). Some have a little more 'pop'/energy, some are damper/deader, but they are all designed to do the same job--so rather nuances than big differences inme. Tune makes a helluva difference. But personally I think people obsess about edge angles too much, a sharp 88 tune will bite very good, not a whole lot of difference too an 87 inmo--if it's good. Base bevel impacts how "fast" the ski will bite and ... the temper of the ski a lot more than side bevel--0.3, 0.5 or 0.7 has less impact on bite. Some athletes ski with (barely) no base bevel at all--which most find completely unskiable as the ski will hook up just by thinking about making a turn. You will have to be very skilled managing your pressure and be on edge all the time (which is basically the idea of a SL ski anyways). @Primoz will know most things about tuning, since he has real pro tech experience ... and he is from Slovenia (like most good techs)! You can order FIS SL:s in different (longitudal) flex from the factory. I have a pair of Salomon (Atomic) FIS LAB 16/17 in the soft version. But I am 48 y/o. It is a damp ski, with a very gradual flex, if that makes sense. Easy going. As stated earlier, your ability and intended usage is more important than your weight or height. Quite normal that strong U16 (14-15 y/o) girls ski the 155 cm FIS SL:s. And what is most fun for you.
EDIT: Most "normal" people never tune the base. Just polish it up with a fine stone to keep it smooth and get rid of burrs.
It's only a "placebo" until it can be quantified via scientific measurement. We're getting there thanks to the folks at SoothSki. They're already providing a ton of valuable data and I believe that given some more time, we're going to see these questions get answered regarding the life span of skis and how they change over that time.
This sounds like a little experiment that I have never done in any sort of controlled way but that might support my superstitions. I typically mark skis L and R, ski them that way most of the time, then if I need some extra edge grip (very icy), switch them - but only if I'm fairly sure I won't hit any rocks, etc. My spurious logic had been to concentrate the edge dings / wear and tear on one set of inside edges, keeping the other set cleaner. But this spurious logic is a bit undercut by the fact that I often ride the inside ski too much. I hadn't considered whether there could be any long term effect on material stiffness that would be specific to one side of a ski vs the other. Who knows.
The effect (if it exists) could also be placebo - if I think the ski will hold better, I may ski less defensively and voila, the ski holds better.
This is so hard to explain... if someone has a better way, please tell me. People seem to be too used to think only about the deformation, and not about the stiffness. The curve that we provide are not the deformation profile. They are the stiffness profile.I been skiing for decades, and skis breakdown over time. I doubt most skiers who have owned a pair of skis for a long time would disagree (maybe I am wrong). The two things I notice the most are longitudinal flex gets softer (especially the front/tip area) and they loose their pop or rebound energy. I watched your video, and if you are just measuring flex profiles (or displacement) by bending the ski to the same position every time, you won't be actually measuring that. Do you actually measure force versus displacement at various positions on the ski? I don't want to make any incorrect assumptions about what your machine does.
To your question: I had a pair of K2 710 FO skis. They were foam cores and that was new at the time. They broke down and became really soft before the end of one season. It took a few years, but the process of natural selection determined foam cores don't hold up as long a wood cores. Your machine would have caught that right away. These days, I agree with basically everything you said about skis. They are almost all wood cores, and seem to last a reasonably similar time period.
I will say, since I am 6'4", 240 LBS, and a race coach, I can break down a ski faster than most people can because I can stress them more than most. I have an old SL ski (not FIS model) that has significantly softened after about 150 days. I have another ski, fully cambered twin tip, that is in the same boat after the same time frame. I still ski both, but notice the change. I have never measured anything, this is just by my feel.
I feel this quite often with almost all of my skis. Which ever ski I tend to favor for the right one, has slightly poorer edge grip. Nothing really to do with left or right feet, just the preferred inside set of edges. My inside edges almost always have more ding's and imperfections than my outside edges. When I flip the skis, I get a better grip out of the skis. I try to change them up now, I figured this out a number of years ago. You did say you had a fresh grind, so in theory they should have been the same, but maybe not in reality. I use magnifying goggles to inspect my edges and can see the minor imperfections. After a grind they are mostly gone, but the deep dings are still visible. I also believe your skis could be degraded some on the heavy usage edge side, too.
I sharpen my edges razor sharp, always. Sometimes they are too sharp. A few hockey stops mellows them out pretty quick. About half way through the day, on a boilerplate day, I switch left/right skis and always feel improved grip till they dull up a bit. I can feel a reduction in sharpness on a boiler plate day in about 4 hours. Not saying my edges are dull, but not as sharp as the first run.