When To Change Your Ski ?

[Stevie Boy]

So with improved materials and manufacturing techniques, how long before the various components in a ski, break down enough that it would be beneficial to change a ski, if you took a 22 - 35 off skier who does, 150 sets a year and looked after his ski as well as keeping it out of direct sunlight when not skiing, would you be looking at one, two or three seasons ?

[Ilivetoski]

I'm a 22-35 off skier who keeps my ski out of direct sunlight and I have replaced mine every year for the past 4 years. And I'm selling my v type now to get my V type R as soon as the dealer can get one. I do it just because of the deals I can get. If I paid the full $1520 for my V type I would have kept it 3 seasons probably

[Chef23]

I would say you should be able to get 2-3 seasons at that level out of most skis. @Horton may have a better perspective.

[Than_Bogan]

I honestly still feel like I can get 5 years out of a ski, but I am a lighter-style skier despite occasionally getting into -39. I'm currently on my 3rd season with my Nano One and I have no reason to suspect any degradation in performance.

[Horton]

150 sets a year into 35 off? I would demo at the end of year two. If new skis do not feel faster and snappier no change. After 3 years I would do it again.

 

Personally I would change more often but I ski pretty hard.

[303Skier]

I'd say replace your ski every 2-3 seasons personally. I ski into 35 off 36 MPH consistently and I can say my A2 is finally starting to lose it's performance. I demoed another ski for a week, went back to my A2 and it just felt dead. I don't know if they lose rebound, get more stiff or if they flex more over time?

[Ilivetoski]

@303Skier lose flex. Get soft.

[gsm_peter]

I ski slow speed and 15off.

My Vectors al frame are softer after type 300 sets compared to newer Vector ff 30 sets.

Can not comment on skis...

[Horton]

@303Skier I think rebound is mostly what is lost. At longer rope lengths and slower speeds I think it is less noticeable. For me a dead ski is so frustrating.

[303Skier]

@Horton I agree 100% about rebound. Maybe a Q45 will last longer since the layup is at 45 degree angle? I know that when I ski my A2, off the ball I can't hold the angle like I use to which equates into skiing narrow.

[Jordan]

You should get a new ski as soon you try a new one and it is sweet! !!!!!

[Horton]

@303Skier I seriously doubt that layup impacts breakdown

[E_T]

when you have 2k burning a hole in your pocket

[ALPJr]

After 15 seasons and about 500 sets, my Phantom skis like new when I'm skiing the right way. My brand new Vapor looks pretty silly when I'm screwing up.

[Horton]

@ALPJr put Phantom on the wall and never use it again

[303Skier]

There is a guy at my club who still skis on a Phantom! Lol.

[thompjs]

My Goode 9500 only lasted two sets, I never got back to the practice score I got on that ski on second set.

 

Dave does some amazing engineering to have that happen!

 

 

[ozski]

When a better looking one comes out.... This is the only true answer so far :smile:

[Chef23]

When I can talk my wife into it.

[DaveD]

How do you test rebound loss? Would flex testing show that degradation or should we strap accelerometers on the ski and do some vibrating testing?

[Horton]

@DaveD I know it has been talked about but I do not think it has been done. Easy to dream up a contraption but time consuming to get it right.

[Horton]

@DaveD i belive regular flex testing does not do a good job of showing loss of rebound

[nzcabbage]

I buy new technology to makeup for inability......I've had a few new skis........

[DaveD]

@Horton, so are you thinking the standard flex tester is missing the weakened area of the ski? I would think that the flex toward the back of the ski would be just as important to check as the area under the bindings.

[Horton]

@DaveD static flex testing does not measure dynamic flex - rebound.

[Horton]

@DaveD static flex testing does not measure dynamic flex - rebound.

[303Skier]

Rebound would be a very hard one to test! You'd definitely need a baseline to compare.

[DaveD]

Coming up with a standard test set-up for rebound probably wouldn't be a difficult task but I doubt the set-up would be as easy as the current flex test.

 

I guess we're stuck convincing our wives we need a new ski with subjective data instead of quantitative.

[tap]

The setup and data collection for dynamic stiffness can actually be very simple (more so than a static flex tester), the data analysis on the other hand is much more interesting and requires about a sophomore level understanding of undergraduate physics. I think the question is not so much the how, but whether or not it brings any value (yet to be determined).

 

@Horton is very much correct, in general static stiffness is not dynamic stiffness. Although, I suspect for this application that a knockdown in the static numbers would be a pretty good indicator that the dynamic numbers are also changing.

 

I measured a few dynamic baselines at the start of this season on a couple of my skis. I am planning to measure again at the end of the season to see if there is any variation. I may have some data to present then, but for now it's all conjecture. I love the analytical side of the sport as much as the physical side. I do it just for fun because I like the science of it, but then again I'm quite certain I'm the odd one out. Most of the time I just get the deer in headlights expression when I wonder too far into the science.

 

The problem with analysis seems to always come down to measurement resolution and establishing a threshold. If I measure at the beginning and the end of the season and find no measurable difference then are you convinced that nothing has changed, or simply that the instrumentation was unable to measure the change? And... even if I am able to measure a change, how big of a change is needed before it truly affects the performance of the ski?

 

Maybe someday I'll have a large enough data pool to draw a general conclusion. Until then I say try a new ski, if you love it and can afford it then buy it (but don't throw away the old one, donate it to science!).

[Texas6]

Nationals is generally the time to change your ski:)

[Stevie Boy]

@tap interesting, it would be good data for all sorts of purposes, especially when it comes to different skis and different methods of manufacture, if you take the Fisher or Monte Carlo would they stand up better against other skis produced by the preferred method of manufacture, if this was the case, there could be a good argument for spending those extra dollars.

[DW]

@DaveD: You could test rebound loss by measuring frequency or the time decay of an input to the ski, kind of like a tuning fork.

[Than_Bogan]

@tap I'd certainly be interested in your dynamic flex test setup and methodology. If no one else is, send me a private message about it!

[DaveD]

@DW, there are test labs all around town (SE MI) with shaker tables. Unfortunately, I don't have any friends that work/own any of these test labs I could hit up with a favor.

 

The biggest issue, and @tap alluded to this, is the complexity of measuring the output of any dynamic test. That's the beauty of the flex tester. It's stupid simple use and just about anyone could make one to have around for regular use.

 

It's been 30 years since engineering school for me. Maybe there's a engineering student out there that has used an inexpensive data acquisition system for a lab that could chime in here. Every one I've used for work has been quite expensive.

[DanE]

Maybe a new way of static flex test would reveal a change in dynamics, instead of just flexing the ski to the one standard measured distance divide that distance in say four increments along the way and make notes.

Loss in rebound characteristics might show in lesser pounds in the smaller flex distances?

[tap]

@Than_Bogan , I'm keeping the setup and analysis as simple as possible. I strip the ski of all hardware (bindings, plates, fins, fin blocks) then fixture it in a simply-supported condition at both ends, stick an accelerometer to the mid span, then give it a whack! I convert the acceleration data to the frequency domain using a fast fourier transform to find the natural frequency of the ski.

 

Right now all I'm doing is tracking the natural frequency. All else remaining constant, a 1% change in frequency (Hz) equates to a 2% change in stiffness (EI), modeled as a simple uniform beam. What is neat about the frequency assessment, in theory, is that it measures the entire ski with one single number, which is great for monitoring the health of a ski.

 

The accelerometer I use has a pretty high sample rate, but if you get really bored just about all smart phones have a built in accelerometer. There are free apps to capture .csv data. Just remember, if you strap a cell phone onto your ski you are changing the mass, and therefore the natural frequency. The key to the analysis is consistency in the setup.