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Objective board comparisons


John E
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It would be informative to me if there was some way to measure different board characteristics so I could see how they stack up on paper.

What I'm thinking is that along with length, width & sidecut radius, other measures such as longitudinal stiffness, torsional stiffness, fundemental frequency and damping factor:

1) If a board were to be supported at the ends & measure how far it deflects under a specific load (say 200 pounds).

2) If one end of the board is clamped & the other end twisted, the number of degrees of twist per pound-foot of torque applied.

3) If the board were clamped at the center & "twanged", it would vibrate at a particular frequency. The stiffer the board, the higher the fundemental frequency.

4) If the board were clamped at the center & "twanged", it would vibrate until the amplitude of vibration fell below some value. This would be a measure of dampening.

Regardless of how a board is made, these tests would allow one to compare boards from different manufacturers "on paper".

It seems like so much of board evaluation is based on how much fun someone has on the board. This is very subjective and is influenced by so many other factors other than the board itself.

Has this ever been considered? Does anyone else think it would be of value?

The reason I'm asking on this forum is that it seems like members are more analytical than snowboarders in general.

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Having objective tests would be awesome, but I can't seem to find it reasonable. There are so many different variables; where do you apply the load, where does it twist, what do you do for longer and shorter boards, what if the board is the same length but has a different nose shape, etc...

The problem is in order to get in detail enough to actually make a decision, there are so many numbers it's overwhelming. Not to mention the fact that you'd end up with 2 boards with totally different numbers that end up acting the same.

I'd love it if everything were analytical. I'm fairly anal retentive, everything should be in it's place. Unfortunately snowboarding is just one of them things that at the end of the day you gotta go by feel.

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yeah those should definitely be standard. shorter and longer boards would obviously have different characteristics, and that would be seen in the measurements.

at least with these type of standards you would have a starting place on board decision. and yes of course, how it feels would be the final determining factor (if you get a chance to demo).

i'd also like to see a comparison of base structures... i believe that i saw some AFM profiles of a base in a SWIX catalog... but i would have to double check. i've thought about contacting some companies to get some samples.

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Good to see like minds think a like! This has been a pet project/idea of mine for close to 10 years. The closest I ever came to getting it done was I worked as an advisor with two Colorado University engineering students back in the late 90's to develop the test stand for just these tests as a senior project. So here is the interesting point, we came up with the same three test you just listed. However, we clumped the "vibration measurements" into one. Unfortunately, the guys I worked with did a great theoretical job on the project but they never actually finished the test stand. Damn mechanical engineers and their Deep Space Nine chat rooms taking up their time!

I have always disliked the subjective test the magazines do with skis and boards. You read "and snowboard instructor Brad from VT thought that Brand X really ripped and was a blast in the pipe"......OK, what does that mean to me and who the hell is Brad? How many boards have you ridden that your buddy said "it rips" and when you get on it you hate it? Too many different tastes in what makes a good board. It needs to be more scientific to be useful.

Imagine if car reviews where just a page of what the test driver thought and no basic stats on the car? Yea, a little helpful but I know that if I read the stats on the car i.e. horse power (watts for the guys across the pond), curb weight, wheel base, type of suspension, skid pad tests, quarter mile numbers, 0 to 60 mph times, etc I can get a pretty good idea what this car may feel like. Not a 100%, but much closer then not knowing any of these facts. Of course test driving the car is the ultimate. Same goes for snowboards.

I think the whole idea would be fantastic and a benefit to the entire snowboard and ski community. What would happen is initially it might not have much merit as there will not be much to compare too. But image after a few years and the data base builds, you can then start comparing boards from ones you have used in the past. This would then help you make a decision on a board now. Some of the details still need to be figured out, but very doable.

One issue I see is the industry itself rejecting this test. I could be wrong, but they may find it a negative on the way their boards are perceived and debunk the test. I don't see an issue with the guys most of us work with (Donek, Coiler, Prior, etc) as they are all pretty analytical but the really big guys might knock it down if it does not fit their bottom line.

OldAcura, swing by the Bomber shop next time you are up and I'll show you the partially made test stand I have. We can chat more on the subject as well........and Deep Space Nine stuff too.

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another aspect of 'standard testing' would be to see how quickly a board (or mfgr) falls out of original limits. maybe as a board ages it gets more damp... or less. maybe one mfgr has a 'good' run of boards and several bad lots.

I could see some mfgrs shooting this down from this standpoint.

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I think Fin has done an excellent job of pointing to the tip of the Iceberg! (not to mention cover a tough subject in a few well choosen words)

Deep subject , many consider, few attempt. There are some good processes in place and being used by builders. For obvious reasons (touched on by Fin) they are not quickly offered up. We can hope that some one does take this up and if they do, we should try to be constructive in comments associated with the systems.

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another aspect of 'standard testing' would be to see how quickly a board (or mfgr) falls out of original limits. maybe as a board ages it gets more damp... or less. maybe one mfgr has a 'good' run of boards and several bad lots.

I could see some mfgrs shooting this down from this standpoint.

Exponentially more slippery a slope!!

Let the "Engineer Speak" begin now.

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hey fin, how much of the stand is actually complete? if you have any pictures, could you post or send me an email?

there's a couple ways to measure vibration, and yeah vibration/damping coefficient can definitely be taken with a single measurement.

maybe if we got a complete prototype stand built it would be possible to test it on various boards... maybe take it to an ES! certainly someone would be interested... even if companies don't want to standardize, they'd probably want something similar for internal use (if they don't already).

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Another interesting test would be if the flex is linear along the board, because some boards are softer in the middle and stiffer at the ends (like Coiler from what I've read), or softer in the front and stiffer at the tail, and so on. And also maybe add a variable that would determine how different bindings affect the flex pattern. This could be a different poject by itself more oriented towards bindings.

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We talk about this, or at least flex / bobsi, every year...

I do not think that manufacturers wont to have an accurate system available to the public, not even to compare own models, never mind to the other brands! How else would they sell you the same model as 3 to 4 different ones, with just graphic changed? Ski companies are notorious for this, and I believe the bigger snowboard companies too.

Out of our 3 favorite makers, only Bruce would tell you how exactely his numbering flex system worked, and that's only applicable to the same lengths of the same model. None of the 3 ever bothered to join one of these discussions...

And to be compared to another maker? No ways, Jose! How would one sell on emotions (most prevailing factor in majority of the buys), graphics, and marketing jibberish/techno talk?

Nope, you wont see any kind of standardisation like that, unless a government/international agency forced it upon them by the means of standard.

Boris

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even so, if there was such a tool available it could still be used to measure boards from people on a voluntary basis. vibration tests are non-destructive, and load tests wouldnt necessarily have to be performed. a database could be built and accessed by the public.

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I can understand the marketing departments of board makers to avoid tests like these because it may expose their hype. However, each of these tests would be pretty easy to carry out with simple equipment.

The fundemental frequency & damping tests would require an accelerometer and a computer to display the data. We make these type of measurements on equipment we design at work.

The holy grail of designing a mechanical system intended to move is to make it stiff & light. The easy way to make something stiff is to add material. Unfortunately, this also increases the weight. That's why stuff like carbon fiber is appealing - it has a very high strength to weight ratio.

Getting a board to damp out vibration usually involves adding an elastomeric material. Unfortunately, this also adds weight.

Anyway, if the makers are not interested in doing & publishing this data, it would involve time & expense on the part of a 3rd party (like Fin). It is also likely that makers would attack the data if their product didn't measure up well.

I think it would be interesting from the standpoint of comparing subjective opinions on the performance of a board to how it performs in objective tests.

This may advance the development of boards.

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I took BOBSI to heart and have measured more than 50 boards, rode at least 45 of them too. The net result - you cannot tell how a board will ride based on the numbers. Like asking why a 1.8 turbo VW seems much faster than 180 hp, and why a 400 HP LS2 Trailblazer is so slow. The stats don't recognize the flex pattern, the use of metal, the width of the board, and so on. The only use it might be is to compare different lengths of the same model from the same manufacturer.

BTW - BOBSI says the metal boards are so soft they will be unrideable, and we know that's not true.

Fin, bring on the board dyno.

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it's undeniable that the type of characteristics being discussed have an impact on how a board performs. yes, flex patterns and other considerations will contribute, but at least with some standards, there is a starting point which can be built upon so you can say "alright my board has this damping coefficient and this flex pattern, etc.... so i can assume it will be good for ice, etc."

i'm not familiar with BOBSI (i.e. what it means, what it measures)

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http://www.bomberonline.com/VBulletin/showthread.php?t=6270

http://www.bomberonline.com/VBulletin/showthread.php?t=4499

http://extremecarving.com/forum/viewtopic.php?t=1104

http://www.bomberonline.com/VBulletin/showthread.php?s=&threadid=23

The highlights:

Bomber

Online

Board

Stiffness

Index

...the formula is:

(98.1/deflection)*(effective edge squared) = BOBSI

The euro version?

(98.1/X)x(effectife edgelenght x effectife edgelenght)

x= the height difference of the camber in cm when you load your board with 10kg weight

the board must attached at the end of its eff. edge..

too difficuld for my english, please look at vkrouverks link

it says the donek stiffness index is something different as the scale reaches up to 10 only

Hey!!! It still has a heart beat!! Come on , let's make sure we beat this to death this time!! :cool::eplus2:

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Ok - I see that this subject has been discussed to death. However, it looks like the BOBSI measurment is static. A dynamic measurement might be more telling but it would also be more difficult to carry out (require more sophisticated equipment).

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Cail: the partial test stand is buried right now in storage and I have no pictures at this time. If I ever drag it out I'll take some shots.

Derf: you nailed it. One flaw with the BOBSI (not here to bash BOBSI, great idea and excellent start) is it takes the entire board flex into measurement. So in theory you could have a board with the front half stiff as a brick and the rear half soft as a noodle (as DERF mentioned). With BOBSI you would get the average of the two and show a relatively OK flexing board. When the fact is it would be unridable. My suggestion would be just that, test the front half and rear half of the board independently. Still not the ultimate but better then the entire deck at once.

Chris H: Could you post a handful of the number you took? Be interesting to see what you found. Give some of the higher and lower numbers as well. I am interested to see what resolution you are getting on the results and repeatability?

Your analogy is correct, if all you knew was horse power you would think a 400 hp TrailBlazer should be faster then the 180hp VW. But not the case. However, with just one more piece of information, curb weight, we would know the truth. Of course gearing, wind resistance, etc will also change things but for BETTER understanding just these two numbers would work.

Why the BOBSI is showing the metal boards are too soft? The test is only one factor in the three proposed tests needed. You need to measure the torsional flex and the ability to dampen to get a better taste for the board. As we all know (if you have been on one) the metals have some fantastic dampening abilities, so maybe this makes up for the softer flex? Maybe the metals are torsionally stiffer, making up for the softer longitudal flex? Who knows, I say we find out!

Another interesting thing we could measure with this test stand is board life. Measure a new board and log the numbers, then ride for 10 days and measure again, ride for 10 days, measure again, and so on. After while you should see a curve showing the changes (the three measurements) in the board. Might not mean much at first, but as I mentioned before it will be the accumulation of data over time where we will start to see the trends. So if we see a large dip in the number curve on the "Life" test at the same spot for all boards (lets say after 30 days) then we start to know that after 30 days of riding board, we see drastic changes in the boards measurements that may or may not mean lack of performance. We'll have to see.

My other theory is on the brontosaurus: it was really skinny at one end, very fat and large in the middle, and then really skinny again at the other end. That is my theory.

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i was just looking up some specs on Titanal (http://www.amag.at/en/fs_b.htm) and it has fairly high tensile strength (comparable to some PM steels..in fact it's yield strength is higher than a lot of PM steels). also, it's Brinell hardness is comparable too (slightly lower).

anyway, in regards to BOBSI, i'm going to take a look at it to figure out why it would say that Titanal is "soft". basically, the calculation doesn't make any sense to me, especially since it has no units.

measuring dynamic stiffness is more complicated than static measurements, but doable.

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Imagine if car reviews where just a page of what the test driver thought and no basic stats on the car? Yea, a little helpful but I know that if I read the stats on the car i.e. horse power (watts for the guys across the pond), curb weight, wheel base, type of suspension, skid pad tests, quarter mile numbers, 0 to 60 mph times, etc I can get a pretty good idea what this car may feel like. Not a 100%, but much closer then not knowing any of these facts. Of course test driving the car is the ultimate. Same goes for snowboards.

You've got two kinds of numbers there - specifications and performance results. Horsepower/weight ratios allow you to speculate how fast the car will accelerate but you don't know until you measure it. Gearing and suspension also have an affect - I've seen tests where the worse car on paper is faster for whatever reason.

Publishing flex indices and vibration points for boards is even worse - that's like trying to deduce how fast a car will be around the track when all you know is spring rates, sidewall stiffness and shock valve sizes.

What is needed is an objective performance test with subjective clarification. Car mags will say "car X was slightly faster than car Y around the course but felt unstable, so for average drivers car Y is a better real world handler". That's useful. Why not set up race courses of a couple flavours, get a few riders of different weights, and try to get some stats on time? Then you could say, "board X was faster for heavier riders, board Y was faster for light riders, most riders felt board Z was too nervous".

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We are not trying to establish the speed here... Speed would be more a function of base material, structure and wax used, right?

With BOBSI we are talking flex and only the flex. So a buyer can think to himself "ok, it should be this easy or that difficult to bend this board with my weight and skill". If a data base existed, then he could say "ok, according to these numbers, it would be similar to the board A I've ridden before, but softer then the board B..."

Torsional stifness would be a separate number, and it would indicate the potential edge hold.

Oscillation number would indicate the dampness.

Etc...

This is not exactelly the rocket science... Just an indication for those who care and believe in numbers...

On the side line, when BOBSI tels you the Metals are soft, well they are, and they were intended to be so. That doesn't mean they are bad boards. It just means they are easier to ride (well, bend).

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We are not trying to establish the speed here... Speed would be more a function of base material, structure and wax used, right?
Speed is a combination of a variety of things, but to take structure and wax out of the picture the boards should be tuned by the same tech in any sort of test.

My problem is that stiffness alone is not very informative. As the metal boards are proving, stiffer isn't always better.

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OK, these results are for normal "serial" boards unless stated otherwise.

Burton FP 6.4/19 10.0

Prior 161 WCR 10.2

Hot Blast 164 11.8

Virus Gladiator Extreme 11.8

Sims Burner 167 11.9

Donek GS 180 12.9

Volant SL 162 13.3

Oxygen Proton 178 13.6

Prior 179 4WD 14.5

F2 168 Siberpfeil 10.5

F2 168 Silber w/conshox 19.6

The Volant felt much stiffer than the Oxygen, maybe the metal? They all rode quite well, certainly it would be a challenge to guess the number even after riding the board. I came to the conclusion that torsional stiffness is a greater factor than longitudinal stiffness - ergo low BOBSI for metal (under 10) but rode more like 14. I have lots more, but a lot are custom built so they would not mean much by way of comparison. All results are an average of 3 measurements, the flex under load was fairly consistent and repeatable, never varying more than 1 mm unless I screwed up the setup.

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Please let me speak on the subject as I have spent a bit of time on it :D As you may know I do put a stiffness indication # on the side of every board. It is just a static measurement that gets the board in the ballpark for its designed user. However, being ballpark, it is still miles better than having nothing at all. Even for different flex patterns the numbers are somewhat similar as if the overall stiffness is right, the flex pattern will change the performance a bit to get the desired ride but the overall stiffness of the board is close to the same. Of course if you get into some real off the wall patterns, that is a different story. As builders what we are up against is the actual tolerances of the core thickness, which we can control if careful but the real demon is wood density variables. Even using the same species in an identical configuration can give drastically different results in overall stiffness. This is especially a factor in cores that use strips in the 3/4"ish wide configuration. Cores with narrower strips will naturally have a more consistent stiffness due to the law of averaging out. Even using wood from the same planks will have differences due to grain directions so its impossible to get the same thing every time. I once did 2 identical boards with cores accurate to 1/10mm and the stiffness came out to approx 50lbs of rider weight difference. One core was real stiff, the other quite a bit softer and that was all it took. Since my cores are cambered it may well affect my process more than others.

The metal boards are certainly interesting in that you can get by with a way softer board and still get massive edge hold from it so the results are a bit deceiving. I find that you can ride the softer boards but there are limitations especially in softer snow of course. They work like no others on steep icy hills though! For some reason they tend to fold less than a softer glass board also. Can't really say why but I feel its due to the different kind of flex the metal offers throughout the various sections of the board.

Never did get around to doing a torsional stiffness measuring system as it is a tough thing to figure out and just from experience I know approx the amount of materials to use to get the desired results per application and that seems to be good enough. Some of my glass race boards have a varying torsional rate throughout the length so it would be really tough to measure those.

So if you are thinking a measuring system would be good, you are probably right. If you are thinking you are going to see one widely accepted, I doubt it. Most boards come out different ( even identical models) as it is real hard to get them exact with all the variables in play. Good old fashioned labor and extra time during the process can remove a lot of the factors and that is the way I get around it. Probably takes me 2 hrs or so per board just dealing with those factors. Pain in the ass but the end results are worth it.

Cheers, BV

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I thought I would share a small nugget here, but dont want to get too far into this.

I personally have a lot of interest in the measurements of vibrational energy and what that can tell us about riding characteristics. Because of this, I spent a notable amount of time with some fairly high end equipment to take some measurements on many of the boards at my disposal. After MANY hours of data gathering, finite element modeling and data analysis. Here is what I found.

1) a properly developed and constrained FEA model can accurately predict at what frequecnies a particular board will have resonances.

2) a properly developed and constrained FEA model has a difficult time predicting the actual amplitude of these resonances

3) boards of different dimensions have drastically different vibrational characteristics (this includes lenght, width, core profile etc)

4) depending on the point at which an accelerometer is placed on a board surface, you will get drastically different results. If you dont know all of the different vibrational mode shapes, and you place the accelerometer in a null, you could take a board that is known to be very chattery and underdamped, and make it look as smooth and damped as the best kessler ever produced.

5) based on #4, an analysis between two different board designs is nearly impossible unless one were to take data over the entire board with a scanning laser.

6) Even when analyzing 3 boards, with the same dimensions, that "feel" different to riders, it is VERY difficult to see any difference in the vibrational data gathered (if you can see it at all). furthermore, quantifying this value into a meaningful number or score to be compared from board to board would be just about impossible.

I will try to link to an animation of one of the modes of one of my 185 GS boards a little bit later when I can find the file.

Just thought I would throw in my quick 2 cents.

So, not to sound like a jackass, but when talking about the reduction of vibrational energy, aren't we talking about damping, not dampening? When I started at work and refered to it as dampening, I was promptly told that I was using the wrong word.

-Todd

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