Skiboard Stiffness Comparison?

[FightingForAir]

Skiboard stiffness comparison:

Did a search ... could not find anything together or all in one place and not much specific.

Stiffness is not listed on skiboardreview.com or on the SBOL comparison chart.

This is something that would be very helpful in board selection.

Perhaps adding to the board selection table that is already stickied? Or on the SBOL comparison chart ... or on skiboardreview?

I know I am still a rookie, but it seems to me the combination of board dimensions, total surface area and flex ... all relative to rider weight would be very helpful to new guys like me when considering new boards when we may not have the ability to field test them prior to buying.

Just a thought.

[nate]

This was discussed briefly a while back. It's an interesting subject, and I agree it could be helpful. The problem with putting it on something like skiboardreview or SBOL board chart is that it's not a very quantifiable thing. The feel depends largely on the person and the riding style. Also, different boards have different flex patterns, meaning a board could be very stiff throughout the middle, and get more flexxy at the tips. (or conceivably, vice versa)

All in all a hard thing to measure as a true "stat"

Edit: you can look at the thread where it was talked about here: http://www.skiboardsonline.com/vbulletin/upload/showthread.php?t=6460&highlight=skiboardreview.com

[EmptiMind]

Still want to see this. :P I want a stiff board, that's all I've ever used, and now I have the Reveolts, and they're by far the most flexible boards I've ever touched.

[SkaFreak]

The stiffest Revel8 boards are definitely the 08' KTPs. The Sherpas are pretty stiff as well.

[pinkkid]

Still want to see this.

me too.... but I see the issue of quantifying it, but by say soft flex, med flex, stiff etc can help. After riding enough of these R8 boards, I clearly like the flex over the stiffness. Sure, rider weight has a lot to do with the flex, but at least we have something to start with. When they design each board they put certain amount of flex in each one... we wanna know what that is is all were really saying here; and then put in the comparison chart from here on out. Is this possible to go G?

[TheTickz]

can someone make a list of all the boards that SBOL sells from stiffest to flexiest.

[Kirk S]

Loken's are the stiffest board that I have ever ridden

[DennisEvans]

I ride summits, they are pretty stiff compared to Revolts.

[Roussel]

i think the brands need to come up with a rating scale for themselves to let people know. or at least give them an idea what to expect. or at least put it somwhere in their description of their skiboards.

[slow]

This may be over the top and way to much information. But to do it "right", we would have to measure the force in pounds to deflect each skiboard a fixed deflection (say .5 inches) when a force is applied to the center and the skiboard is supported a fixed distance (say 15 inches) on each side from the load application point (simple point loaded beam). Then we could compare the pounds per inch of deflection of each skiboard. Higher the value in lb/in, higher the stiffness or flex.

SkaFreak, do you have any physycal testing of materials project requirements coming your way in your Engineering classes?

[SkaFreak]

It would be hard to create an exact method for determining the flex of the boards based off of any form of testing. Doing the calculations for the bending would be fairly complex as well, because of the composite structure. You would need to know the modulus of elasticity for every component involved and the equations would tend to explode.

I guess an FEA analysis of the boards would give pretty good results as to the flex profile of each board, but I know that the drawings for the boards aren't in a particularly good format for that. I won't have much spare time over the next few weeks or I would offer to do all the work for it. Depending on what happens between now and the 2010 lineup, I may talk to G and Jeff about getting the necessary information to basically produce flex profiles for each board that will show how the board deflects under a given distributed load. This should give a general idea of how flexy the board is along with how the flex changes throughout the length of the board....ideas ideas....

[SkaFreak]

Slow, I had considered a method similar to yours that consisted of making a test setup that would have a 4x4 and 4x10 mounting pattern with a filleted edge and a ruler at a given distance. The problem with this method, is that while it gives somewhat of a basic idea of the flex, it truly doesn't give enough of a profile to be useful. That is, skiboards taper to thinner at the tips than underfoot, so the flex is not linear. In addition to that, the taper is not always constant. For example, the tips and tails of the 09's ktps are softer than the 08's, but I am not positive if there is a change in the middle section of the board. In addition to that, the length of the board will greatly affect the flex. For example, say you have 2 boards with the same profile (by this I mean the exact same taper, so on either board, 20cm away from center would be the same thickness) but one is 90cm and one is 110cm. The 110cm board will feel way flexier because the tips and tail will flex a lot, but the test would show them having the same flex.

However I would like to end this by saying if people want me to run tests, I am more than willing to accept your donations of testing materials, namely boards. I still need Bantam's, Tanshos, BWPs, ALPs, some '09 KTPS, and some Condors. ;)

[FightingForAir]

Wouldn't a better test actually be rebound along the entire length and not static deflection under load? ... I mean for actual application that relates to riding characteristics ...???

Again ... just a thought coming from my rookie perspective ... but from my understanding one of the primary benefits and purposes of a stiffer board especially for heavier riders or higher speeds on hard surfaces is to reduce chatter and maintain that wicked edge hold while carving hard on the icy stuff... speeds are higher and impulses from undulating irregularities in the terrain are much faster. Thus, you just don't want those boards slapping up and down. On fluffy stuff, the impulses are longer (slower) so softer flex is good right?

Being into sports cars, suspensions, handling characteristics, etc ... I liken it to rebound damping in a sport tuned suspension.

And couldn't we test rebound relative to the board length to get a good measure of the board's potential to rebound too much or too quickly when subjected to smaller and faster impulses?

If we were to flex the tips of the board a given distance relative to its length and keep that ratio of flex to length regardless of board size ... release the flex and measure the impulse (speed) and distance of the rebound...??? So with a 90 cm board, we could deflect the tips say ..... 9 cm for a flex to length ratio of .10 (just an example). For a 110 cm board, we'd need to flex the tips 11 cm to keep the same ratio. The fulcrum of the flex would be the outside edges of the inserts so we would actually be measuring the same total area that would be flexing while riding.

Upon release, the rebound would tell us a lot about the board's potential to chatter on hard fast stuff or to be too firm for the larger and slower impulses of powder riding .... no? Am I way off base with this?

[SkaFreak]

It's not a bad idea, but it is not particularly practical. The equipment to run tests would either require a custom build rig or a high speed camera. Either one would be fairly expensive. Plus once again, you are only reliably getting the action at a single point on the board. In order to have a full analysis of the flex across the length using your method would require knowing the exact shape of the board at every point through the rebound. Basically you would have to take high speed video, pull the curve of the board out every x frames depending on how fast it is running (probably about 10 data points) and then fit that in order to develop a decent profile of how the board as a whole is flexing.

As I stated earlier, it isn't going to be a linear flex, so you truly need to have the flex across the whole surface to get a decent idea. If you truly are curious about the dynamic actions, it is possible to run dynamic models in FEA as well. I do not have as much experience, and I doubt it would be as useful for determining how the board will flex at a glance but may be something to consider when designing future boards.

I just realized truly how much I have geeked and MechE'd all over this thread. My apologies to those who are not as entertained by this as I am, hehe.

[slow]

Many years ago, an experienced highly successful and accomplished engineer told me: "Just get on with it! You will learn more by doing than speculating about what could be."

He was right.

Start simple, learn, then take the next step based on what was learned from the previous step. Some of the parameters may not be as significant as we speculate.

And what the hell, the testing of donated boards would be fun!

[FightingForAir]

I just realized truly how much I have geeked and MechE'd all over this thread. My apologies to those who are not as entertained by this as I am, hehe.

Don't apologize ... I like the technical stuff and it's good to hear input from someone who is truly knowledgeable about that technical stuff. Thanks.

However, maybe the quantifiable "stat" isn't all that important. Really all I need to know is how that info translates into riding characteristics rather than knowing a board has so much flex or rebound at "x" distance from center and so much more flex at "y" distance from center.

Sometimes it is hard to glean from reviews because there are so many variables (conditions, riding speed, rider size). A board that a 155 lb. rider feels is too firm may be just right for me (195 lbs) and the kind of riding I'm primarily doing.

I was just thinking good info might help new riders not have to go through 3 or 4 different sets of boards to find their "sweetness".

With that in mind ... how about us at least just pulling together info from a subjective poll to create a chart similar to the sticky skiboard selection table? One that has the bases covered along with perception of flex in different conditions (board, rider height, rider weight ... then perceptions of board flex under different conditions ... well-groomed, icy hardpack, chop, pow, and park)?

[SkaFreak]

Many years ago, an experienced highly successful and accomplished engineer told me: "Just get on with it! You will learn more by doing than speculating about what could be."

He was right.

Start simple, learn, then take the next step based on what was learned from the previous step. Some of the parameters may not be as significant as we speculate.

And what the hell, the testing of donated boards would be fun!

I agree Slow, testing donated boards would be quite fun, I'm just not exactly expecting many people to toss me some $250-$300 boards just to get an idea of how they flex compared to other boards, hehe. I am more than willing to test them when I have time to make a good solid setup. That will be a couple of weeks, but other than a mounting plate and getting a good level surface with a contant distance, it should be pretty quick and easy.

[SBruce]

Just a thought ..

Composite hockey sticks are sold by flex. Might be worth looking to see how they come up with their flex values and possibly apply that to skiboards?

[SkaFreak]

Correct me if I am wrong, but I think that hockey sticks have a constant profile for at least 95% of their length and are made of a single composite material. If that is the case, it would be super easy to throw it in a bending equation and get a deflection/unit length. This is not the case with skiboards because the entire boards are tapered.

[SBruce]

This video shows a machine that they use for measuring stick flex.

"It measures how much force it takes to bend the shaft 1 inch. If the force is within a certain range (the value they print on the sticks you buy), the shaft has the correct degree of stiffness for that model."

So essentially quantifying the stiffness is with a number that is relative to other similar objects tested.

I see what you are saying with sticks being different, I am just throwing up an idea. I am guessing you would have to provide a flex value for tip/waist/tail

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/G-ueMOMW6mw&color1=0xb1b1b1&color2=0xcfcfcf&hl=en&feature=player_embedded&fs=1"></param><param name="allowFullScreen" value="true"></param><embed src="http://www.youtube.com/v/G-ueMOMW6mw&color1=0xb1b1b1&color2=0xcfcfcf&hl=en&feature=player_embedded&fs=1" type="application/x-shockwave-flash" allowfullscreen="true"
</embed></object>