Accurate, replicable method of measuring ski flex (long)

endre · Post by **endre** » Fri Nov 09, 2007 4:39 pm

Actually no, but I am going to. Got a pile of old skis from every decade to 100 years back. I'll be back with something about that.

endre · Post by **endre** » Tue Nov 27, 2007 2:55 pm

I have updated the flex PDF with next year's skis, and made a flex index . This row of 5 numbers (the Ski Flex Index) makes comparison of skis of different length possible (more description in the PDF file), and it makes flex communicatable

Here is the PDF:

http://www.friflyt.no/files/SFI_2008.pdf

MartinH · Post by **MartinH** » Mon Dec 01, 2008 4:11 am

Any chance there will be a .pdf with the ’08-’09 skis?

endre · Post by **endre** » Mon Dec 01, 2008 5:07 am

hmm... probably one with the SFI sometime, but right now I am in a race with nature to get my factory up and running.

nick · Post by **nick** » Mon Aug 31, 2009 11:58 pm

I know this topic is old but I was doing research on the topic and have a question. I am not too familiar with skis but my concern is with snowboards. Do some skis have a differnt flex pattern in the front than say in the back. From those graphs, they look like they are pretty close to being identical from front and back. If this is true, only 3 points would be needed to be measured. But with snowboards, you have the possibility of having a directional board, or twin board. So obviously you have to take into account that there are 3-6 different stiffness areas to take into consideration. In this case, would it be wise to measure in 5 different points of the board (front, middle front, middle, middle back, and back)? Does my question make any sense?

Sorry for the rough description, its 2am and can't sleep because I am thinking about snowboarding.

endre · Post by **endre** » Tue Sep 01, 2009 7:39 am

All skis and boards are different throughout the whole length. I measure every 100mm of the ski, that makes 16 segments of every ski, 12 on boards. This is, however too complex to be useful for most people. that is why we simplify the curves into the SFI or SBFI for snowboards. this is a row of 5 numbers corresponding to the different parts of the ski as you suggest.
read more on: www.endrehals.no

nick · Post by **nick** » Tue Sep 01, 2009 9:23 am

Ok, I have a dumb question. It all makes sense to me except for a few little things. I like the 5 number system, however, how do you arrive at those numbers for each measurment. What is the scale? What does SFI stand for? Thirdly, do I understand correctly that you put the ski on a flat bench or whatever at a tip, then measure the given points? Wouldn't the length of the ski affect how much it would be able to flex under weight and pressure? Obviously, how close the location you are measuring from the anchored down point affects the flex. This stuff is so cool to me! I love the math involved. How did you put it all onto a computer? And that PDF document, you have 2 different size skis there ryte (shown by the thick black space around the ski)? Would it still be the same length of measurement or not? Sorry there was more questions than a few. My bad.

nick · Post by **nick** » Tue Sep 01, 2009 9:24 am

SBFI= SnowBoard Flex Interval? or something like that? just a guess

nick · Post by **nick** » Tue Sep 01, 2009 10:41 am

Also, please explain this equation to me! y=(PL^3)/3EI it seems like im the only one still on here from the U.S. hehe but from my understanding, that equation helps estimate how the flex in your ski/snowboard will be before you make it? I could see the advantage to that! You would be able to tweak the shape and design of your board before you made it. I understand it would not nesecarilly be precise but give you a rough estimate. That would be awesome to know before making a board.

And as for the testing of the older skis, you have to somehow take into consideration that the skis are more "broken in" than the newer ones. They say with snowboards (im sure its the same with skis) that the board only lasts about a month or so before its fibers are broken down and worn in. But, that does sound really interesting. Dang, I wish you guys were snowboarders. I should just move to Norway and come chill w/ you guys and ride, and test boards. Sounds like fun. I'll make it over there someday.

Richuk · Post by **Richuk** » Wed Feb 17, 2010 1:30 pm

Hello,

I'm new to the forum, so please forgive my ignorance, but - jumping in, has any analysis has been completed on how the weight of the rider effects flex? I mean, someone builds the perfect ride and then passes it to someone else who's 10kg lighter and 20cm shorter and now it sucks - they don't lever the ski in the same way ... what's the best way to size up or size down a ski?

Drew · Post by **Drew** » Thu Feb 25, 2010 1:15 pm

Hi I just read through this forum and i didn't see anyone mention that individual pairs of skis inside of a big manufacturer's model line(Like two pairs of mantras) may have different flexs. My point is proved by elan who check the flex of each individual ski and then match it up with another ski that has the same flex. So this being said, I could buy a pair of skis and someone else could buy a pair of the same skis and they could have two completely different flexes.

Here is the url to elan's production process video:
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skidesmond · Post by **skidesmond** » Fri Feb 26, 2010 3:53 am

After seeing the video and judging by the quality controls Elan has in place it would seem to me that the difference from one ski to the next in a given line of ski would be minimal. The flex matching seems like a great quality control check. I wonder if other manufactures go to that length.

I'm just glad the skis I've made have stayed in 1 piece so far

Ski On!

Drew · Post by **Drew** » Fri Feb 26, 2010 6:41 am

From what I hear Line skis doesn't go to that length. I've heard about lines skis coming with two completely different cambers in the pair. They could use some quality control.

Richuk · Post by **Richuk** » Fri Feb 26, 2010 12:15 pm

These might help for pre/post analysis. Gotta say I prefer the DIY option!

Shop bought: http://www.imagesco.com/sensors/flex-sensor.html

DIY: http://www.instructables.com/id/Neopren ... -IMPROVED/

jpelentrides123 · Post by **jpelentrides123** » Sun Dec 12, 2010 2:54 am

hi there

i am a 3rd engineer at Exeter university and am interested in measuring stiffness in snowboards and ski's.

This forum seems to be the best i have found.

Can anyone give me some advice about where to start?

Cheers JP

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Accurate, replicable method of measuring ski flex (long)

Accurate, replicable method of measuring ski flex