BlueB
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Posts posted by BlueB
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Check your mail.
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Thanks for responses, everyone!
Ok, I see, I was reinventing the wheel a bit... But I think it is worth it. As Skywalker said, there must be a way to ESTIMATE a boards characteristics by numbers. Again, I tried (just like authors of BOBSI) to come up with a simple test that everyone could perform at home without complicated rigs, and a formula just to give an overall idea of the board's stiffness. Not to predict the ride completely (where would be the fun then - we could all just crunch the numbers instead of riding?), just to give an ESTIMATE. Instead of saying to a buyer "look, it is quite stiff when I flex it with my hand..." or "I am 80kg (~176lb for pound lovers ;) ) and it rides fine...", one would say BOBSI 9.2 or ULFI 6.4. It should have more meaning?
I have read all the articles I could find about BOBSI (probably there's more on old forum?). Great effort - why no one refers to these numbers any more? Where I can find the data base of measured boards?
Interesting, my ULFI uses similar techniques and maths as BOBSI, so we must be on the right track, no?
Now, few questions about BOBSI.
For those not remembering, formula is (98.1 / deflection) x (effective edge squared). 10kg was used as the test weight.
1) Observations
1a) For the formula to work with the figures given in old examples, deflection has to be taken in millimetres and effective edge in metres.
1b) Effective edge is actually the Contact length, surely? Effective edge is measured along the curve of the edge and it is quite difficult to do for amateurs. Contact length is a straight line. 2 boards of same Contact Length can have different Effective Edge, due to different sidecuts.
2) Could someone (an engineer?) explain the logic behind formula, for public? My knowledge of physics is limited to what I remember from school, so excuse my assumptions.
3) Where the figure 98.1 comes from? My thinking is that the Acceleration of 1G (~9.81 m/s) was multiplied by Mass of 10kg used, resulting in Force of 98.1 Newton? Obviously, it is not a number added in to bring the results into 1 to 10 scale, as many boards go over it, up to 15 - 16.
3a) What the 98.1 (lets call it F) does to the formula? It should be there only if it "levels the field", meaning that the BOBSI number would remain the same irrespectively of the weight used, so long as you adjusted the F accordingly (i.e. for 20kg F would be 196.2)
3b) I tried the test with 10kg and 20kg, and calculated the BOBSI. The results differed about 0.5 - quite a lot for an accidental mistake. It needs much more testing, but maybe, just MAYBE, the 98.1 should not be there at all?
4) Why squaring the Contact Length?
These questions are not to discredit the BOBSI by any means, I just want to understand it fully.
As Nate W said, I do not care what system is used, so long as manufacturers could adopt one and we (the riders) understand how it works. That's why I was hoping to hear from boutique manufacturers at least.
As long as the differences in tail/nose stiffness goes - who cares? In order to carve a perfect arc, you have to pressure the entire edge uniformly, so you would adjust your stance and technique accordingly to the nose/tail differences. Soft nose would help in moguls and maybe in pow, soft tail maybe on ice... For freecarving I would choose uniform flex anyhow. It is the overall stiffness that gives you the first idea. However it is nice knowing the rest too...
Torsional flex is another issue and deserves separate test. The required rig might be complicated for home use, but certainly achievable by manufacturers.
Regarding my proposed "dynamic flex index" test, yes I agree it is done in static state, but it gives you an idea of what would happen when you ride the board, and you pressure it more, and you pressure it more, and you... Trying to insolate/simulate the readings during the different phases of a turn. Therefore I call it Dynamic. And I proposed only 3 ratings, to keep it simple. It is probably less important than torsional flex, anyhow.
Measuring boards movements after sudden release would give a good idea on dampening - very important from what I read. Unfortunately it is completely beyond the means of "home user", and probably beyond the means of small manufacturers.
Again, this is all for fun, and idea exchange, not to start a war. If a benefit for riders would arise from it... well - super!
Boris
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Dean of Prior's told me it is probably 1998, before thy changed the name to 4wd and rounded the tail.
No idea about the exact weight range.
I'm 6' 178lbs and ride a soft Hooger 168 as my all-mountain bord, that has lesser BOBSI than 4x4.
Boris
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base
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deck
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SOLD
Never used, never mounted, mint condition. Few marks from storage / moving around.
I would love trying this one as my all-mountain board, but have no Burton plates...
Flex feels a bit stiffer than on short Alps.
Great all-mountain freecarving board at the budget price.
Nominal L = 169 cm
L (measured) = 167.5 cm
Contact L (measured) ~ 147 cm - 148 cm
Camber (measured) = 1.6 cm
Nose (measured) = 26.8 cm
Waist (measured) = 21.5 cm
Tail (measured) = 26.6 cm
SCR (calculated) ~ 10 m - 10.5 m
BOBSI = 9.2
Inserts = Burton 3D
Stance range = 38 cm - 53.5 cm
Reference stance = 45.5 cm, Setback = 1.5 cm
USD 120.00 + shipping
Boris
boris at netsplash dot ca
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tail
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waist
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nose
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*** SOLD ***
Never used, never mounted, mint condition. Almost no marks from storage / moving. Vax, polish the edges and go!
Ultimate all-mountain carving board for a smaller man, teen, or a female.
Nominal L = 155 cm
L (measured) = 155 cm
Contact L (measured) ~ 134 cm
Camber (measured) = 1.5 cm
Nose (measured) = 26.6 cm
Waist (measured) = 21.2 cm
Tail (measured) = 26.2 cm
SCR (calculated) ~ 8.6 m
BOBSI = 9.3
Inserts = 4x4, 3 pairs front, 3 pairs back
Stance range = 40 cm - 48 cm (with binding slot movement 38 cm - 50 cm)
Square tail
USD 170.00 + shipping.
Boris
boris at netsplash dot ca
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It would be great if manufacturers could standardise their stiffness / flex indexes and publish the information with the specs. Or at least if we, the carvers, could adopt something for our use, so when buying a board one would know what to expect...
I've put my thinking cap on and came up with a simple test and formula:
1) Support the board at the lines of contact (limits of the Contact Length "CL"), say on two chairs.
2) Measure the CL in centimetres. Determine the Centre of Contact Length "CLC".
3) Measure the Unweighted Distance "UD" from CLC, on the base/ edge, to the floor in millimetres.
4) Place a standardised weight, 10kg (10kg sounds good - almost every household bucket would have measurement and take 10L of water = 10kg, or just use 10kg fitness weights), on CLC).
5) Measure the Weighted Distance "WD" from CLC (base/edge) to the floor in millimetres.
6) Deduct the WD from UD. The result is the measured flex "MF".
7) Divide CL by MF, and round off to 1 decimal. The result is what we need: the Universal Longitudinal Flex Index "ULFI". Smaller numbers mean soft, bigger stiff.
It is probably fair removing the bindings, as they could stiffen the board...
Example on my Hooger 168:
CL = 143
UD = 443
WD = 419
ULFI = CL / (UD - WD) = CL / MF
ULFI = 143 / (443 - 419) = 143 / 24 = 5.9583
ULFI ~ 6.0
and another on an Alp 69:
CL = 147
UD = 449
WD = 426
ULFI = CL / (UD - WD) = CL / MF
ULFI = 147 / (449 - 426) = 147 / 23 = 6.3913
ULFI ~ 6.4
I might be wrong, but I brought the length and flex ratio in the play, because out of the two boards of the same absolute stiffness, the longer one will flex more due to greater leverage.
Isn't this a perfect summer tread, and also a chance to do something with your boards when not carving? :)
If there's interested people, I could do a photo story of how it's done.
Now further, boards of the same ULFI could still flex differently in real world - when used, or dynamically. By repeating the test with different standardised weights (10kg,- 20kg, 30kg; or 10kg, 15kg, 20kg, 25kg, 30kg ?), one could determine the Dynamic Flex Index "DFI". Simple graph would show weight "W" on horizontal axis, and measured flex "MF" on vertical axis. Resulting Dynamic Flex Curve "DFC" could be a parabola, hyperbole, straight ascending line, or an erratic curve (requires at least 4 weight test to show).
Uniform straight line would mean Uniform "U" dynamic flex / performance.
Parabola would mean Fast "F" action, meaning that board would probably be easy to initiate, but then require efforts for more aggressive bending / inclinations / turns.
Hyperbole would mean Progressive "P" action - hard to initiate, but then requires small tweaks to bring you deeper into the carve. I'm not too sure if this kind of performance would be nice.
Erratic curve you do not want to see - unpredictable performance...
(For this "performance hypothesis", let's suppose we are working with the boards with same SCR.)
Thus your board's Dynamic Flex Index - DFI could be rated as U, F and P.
I didn't try this test on my boards yet, I have to find the suitable weights first...
Now, I'm sure there's quite a few mechanical engineers here to give us some more input on all this - I am just an industrial designer ;)
Also, Bruce, Chris, Sean, could we hear some thoughts from you?
Boris
P.S. Other very important factor is the torsional flex / stiffness, as the torsionally stiff board should carve better than one that is not.
The testing would require a bit more hardware, but it can be done. Maybe I'll write about Universal Torsional Flex Index "UTFI" next?
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Hey Dave,
Good to hear Wistler is still great. I'll give it a go when Cypress finally closes. Still about 300cm on the peak, but it normaly doesn't last long when it gets this hot in the city... Rain last Saturday also messed up the things - but then it snowed again on Sunday!?
Did you ever ride the Blackomb glacier in the summer - I wonder is that any good?
Boris
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Yet another hardbooter at Cypress! After all we might have a small club of local Vancouver hardbooters...
I met Pierre on Sunday, just by the ticket sales. Of course, we decided to ride together for the day.
Pierre recently switched from a stiff 170 board to newish Rossi 162, short radius. He finds it much better on our narrowish trails. He rips on flatter slopes, his board is MUCH faster than mine on flats. Mine seems to handle better the steeper chopped up conditions. Probably because it is longer, wider and softer? Also we noticed the difference in styles - tall straighlegged vs. compact bent knees. Great fun riding with fellow hardbooters...
Getting really warm in the city, I hope the snow will hold another weekend or two.
Boris
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Originally posted by mirror70
To give the snowboarder a snowball's chance in hell. A skier running the wrong equipment on a snowboard course is still going to be hugely faster than a snowboarder running anything he wants.
Why does a ski have any less friction than a board? If you're on edge, they're the same, and if you're racing you're on edge.
Are you sure there wasn't any point? It seems like you just said that skis are constructed with different characteristics in mind, and as a result of that they are faster. Given that both tools work on exactly the same principals, does it not seem odd that the one which is demonstrably slower is also apparently aiming for different characteristics?
Exactly what I said - SL ski is much softer than a GS ski. GS ski is still compareable to GS board in stiffness. But trend IS towards softening...
Less friction because of lesser surface - no one is strictly just on the edge, especially while racing. J.J. is getting close, thou.
Rob Smith gave few good points too.
Boris
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Has anyone riden Santa Cruz Maverick 183, or 173?
It looks like an awsome big mountain stick, somwhat like Tanker maybe?
Good for plates?
Boris
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Originally posted by mirror70
Try racing a skier down a snowboard GS course, but restrict the skier to skis no longer than whatever the FIS minimum is for SL (155?). You are free to use ANY board you want.
After losing by 10 seconds (if you're exceptionally fast), please try to tell me that board makers are heading in the right direction with that whole longer and stiffer thing.
Question is, if on GS course, why skier should not be on GS skis? Specifically 170+ cm, 21-22m scr, and VERY stiff compared to SL ski. Yes, ski technology is at the moment going towards softer longitudinal flexes and stiffer and stiffer torsional flex. Basically, the idea is to eliminate the torsional flex completely if possible - but skis are easy to skid when you want to.
Generally, any modern race ski will kill any snowboard in the gates, due to the less friction, higher manoeuvrability and more forgiving ride. So comparing the two didn't make any point...
Any ski racers around here to give us more input?
Boris
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Last time I rode softies (early this season), it was 35/25 angles, but I use to ride at about 25/15 in my soft boot beginnings. I never felt that I needed lift/cant, but I figured that more forward lean on the rear highback helps a lot. Maybe some heel lift and less highback lean would be more comfortable? Also, I never liked the "loose" feeling or having any foot roll (skier roots :) ), so I basically tried to emulate the hard boots - cranking the straps until my feet would go numb, and releasing a bit for the chair lift... Going to plates was supposed to be real relieve... but, I still find myself overcranking those hard boots!
Note: This all is for resort riding. Never rode the bottomless powder :(
BTW, where in BC are you?
Boris
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There are couple of relatively cheep, short (153, 159) Rossis on ebay. Mostly never used.
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Here's what Dean of Prior's told me in his email:
"The 4X4 name was changed slightly a few years back to 4WD to avoid confusion to the 4X4 insert packs on snowboards. Bomber and several other customers, etc still refer to this style as the 4X4.
The 4WD with square tail you are referring to is several years old and was probably pressed in 1998. It may still work fine although our current 4WD has come a long way since those days."
Boris
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Snowy, windy, foggy day at Cypress. Not too many people. Hard groom. Nice!
Today I tried 57f/54r at 46cm and I did not like it, probably because I increased it from 45cm by pushing the rear binding back (too much setback). Then I pushed the front one forward to the max, which increased stance to 47cm. Way better! It inspired me to really square the shoulders (but consciously - on the shorter stances I do that without much thinking) and to drive the knees, especially the rear one, into the turn. There's still another 1cm for the rear binding to be pushed back, I'll try that next week, but it will probably upset the offset again...
BTW, toe side initiation is still difficult - I have to really throw myself into these turns. Heal side way easier to initiate, but with wider stance does not hold the edge and chatters if I do not square the shoulders and drive the knees.
Now, technical gurus, can someone explain why 44, 45 and 47cm stances fell ok, but 46cm does not? My only theory is the setback... Could it be so important? Ok, on the wider stances one drives the knees more, too.
Boris
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OK, silly me :) For my information...
Is this a new product? Not listed on their site...
Tel us more if you do have the info!
Boris
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Thanks for input, Mike.
I'm 181cm, inseam 32". Softies I ride at about 49cm. It felt too wide when I switched to hard boots (keep in mind they are ski boots), so I started riding 44cm. Now, it is more like 45.
This board has its maximum at about 47.5cm, but quite a set back, so I am not too keen to go max. Tried a setback stance last week in fresh snow and it felt a bit awkward. I'll probably try 46cm, 57f/54r in the morning... Still, shoot your suggestions!
As these ski boots do not have much flex compared to alpine ones, wide stances creates too much tension on my front quad. I even packed 5mm shin under front toes and 2mm at the back heel to adjust the cuff angles. I did nice bootfitting job (DIY) on these, especially since I started using them for snowboard too.
Boris
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Another beautiful day at Cypress.
Some rain over a week old snowpack, and good grooming made it for perfect morning hardpack. Not crowded either on steeper blues - not good for side-slipping crowds ;) By 10:30am it was a bit chopped up, and by lunch time it softened up, and I called it a day.
I fooled a bit with binding angles. My toe side initiation was still difficult with 60f/57r, so I tried dropping the front angle to 57 too. Easier, but more nose chatter (just like before when I tried this combination). Later on I tried 54f/54r (very small overhang on front foot) which was powerful and easy to initiate, but still with a bit of nose chatter. Tomorrow I'll try 57f/54r as mid-solution, and maybe 1/2' wider stance... Looking forward to it.
Boris
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Originally posted by D-Sub
email prior. theyre very good about info. Hell...take a trip to their shop! youre not that far, right?
No, not far - 2 hours drive. I will visit them, next time I go to Whistler. In the mean time I wanted to chat a bit with "brothers" about board I saw.
Boris
Prior 4x4 / 4WD 155
in For Sale
Posted
BOBSI is stiffness index that someone from this forum has developed... I recently tried to develop my own flex index (see the discussion forum), and learned about bobsi from replies. So now I do both calculations on every board I tuch, just to see how it works.
No idea when Prior rounded the tails...
Boris