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SunSurfer

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Everything posted by SunSurfer

  1. Another option is to seek out an orthopaedic surgeon with an interest in sports medicine and knees. They can examine your knee(s) and look at your records, determine where are the structures that would benefit from support / movement limitation etc. and then recommend a device that actually does what YOU need.
  2. @daveo I'm assuming you've checked out SkiMojo https://www.skimojo.com/
  3. Dangerous time walking the dog. I get thinking. So, given the effect of weight distribution along the board on flex, perhaps rider BMI is a better indicator of how a board will flex under load. A shorter rider of nominal BMI will have less mass, but likely a shorter stance, so their mass is more concentrated towards the middle of the board. A taller rider of same BMI will have more mass, but likely a longer stance, so their mass is spread over a longer mid-section of board. This mass distribution relationship might enable a board designed to perform satisfactorily for a rider of given mass and physique, to perform satisfactorily for a wider range of physiques than we might have originally thought. ------------- A rider can only cope with a certain level of rate of change of direction before they get get thrown off. Our brain and muscles need to be able to keep up with the changes. Sudden changes in direction are harder to cope with. If the rate of direction change produced by the edge engagement curve of the sidecut at lower angles and the flex curve at higher angles are very different then that might make for an uncomfortable ride, especially for riders rapidly moving between low and high edge angles. Kind of expanding on what @Jack M was describing in the the first lines of his post above. An easy riding board would seem to need reasonably matched sidecut and flex curves, and in use by the intended rider not produce direction changes of greater rapidity (really tight radius curves i.e. too soft) than the rider's body could keep up with. A board that is hard to initate a turn on unless the rider is going faster than speeds they're comfortable with is too stiff. An easy riding board is like porridge for Goldilocks, it's "just right!"
  4. I can't agree with the text in italics. Turn geometry doesn't work like that. So to reduce that to the absurd, that would mean a 6 metre long board and a 1.5 metre long board, both with a 3cm deep sidecut would turn roughly the same. To carve, there must be a groove (trench for Mario) that the board initiates, and then compresses both walls as the board tracks the groove, and the curve of the groove and the resistance of the snow to compression changes the board's (and rider's) direction. The radius of that curved groove at any point in the resulting turn will depend on the combined curves of board sidecut and board flex. The higher the lateral wall of that groove the more the board flex curve is contributing to the turn radius. A typical days carving for me will wear away the wax sheen on the 2-3cm just in from the steel edge. On my 174 Nirvana T4 Energy the wax wear starts where the board edge curves to the nose and runs to the tail. The rest of my wax job is almost untouched. That wear pattern is a reflection of the friction on the board base from the pressure against the snow in the lateral wall of carve groove. That same pressure creates the flex curve along the length of the board. If it was just the steel edge sidecut shape that determined the turn shape then there would be a much more even wear pattern on my wax. On an inclined plane slope of perfectly smooth ice, with a perfectly engaged edge, then the maths of Nate's old calculator of how sidecut curve radius changed with edge angle would be accurate. EXCEPT that even on ice a carved edge creates a groove, and that groove has measurable depth in millimetres, and that's enough to throw off Nate's calculator significantly. The bending force applied along the length of the board, and that pushes against the compressed snow that keeps us carving and turning, will depend upon the rider's mass, where along the board that mass is applied, their speed and the radius of the turn. Bending force increases with greater rider mass, the closer to the centre of the board that mass is applied, the greater the speed, and the smaller the radius of the turn. The where the mass is applied effect is not immediately intuitive. This is an important part of the effect of isolation plates that attach to the board at just two points and allow the board to curve freely under load (e.g. Bomber Boiler Plate). Under the effect of gravity, with a board suspended at tip and tail, if all of a rider's mass (e.g. 80kg) is applied at the centre of board then the maximum bend for that mass is produced. If you divide that mass in two, and apply it above the suspension points at tip and tail no bending occurs. If you mount a BBP plate on the board and put the mass in the centre of the plate the board bends less than if the mass was in the centre of the board. Distribution of mass along the plate makes no significant difference to the resulting curve in the board. The wider the plate axles are apart, the less the bend for any given mass. If you have an isolation plate you can demonstrate this for yourself. But the point I want to make is this. The lateral wall of the groove is what keeps us from falling in the depths of our turns. It's what we balance on at every point of the turn, and what forces (as in changes our momentum) us to turn. And that means that groove geometry and board flex are key parameters in the production of any carved turn.
  5. When you talk about typical short board performance are you thinking of the relative lesser stability at high speed, or that shorter boards generally turn more tightly. The tighter turning is probably due more to the sidecut tending to be shorter too. Not a lot of 160cm long boards out there with 20+m sidecuts! Thankyou to everyone who has posted so far. I am having a great time pondering all the various factors that are being brought to this discussion.
  6. @TimW How do you measure stiffness? What are the units for the y axis (stiffness). Thanks for the explanation so far. I need to re-read it and think for a while.
  7. @dredman You're primarily dealing with BV for the Contra, although I know you've ridden and are riding other makers boards (edited) so have a broad board experience. You've mentioned a range of different aspects of flex and that's going to help me start to understand this. But, and it's a BIG but, what repeatable and reproducible methods are there for measuring these different aspects of flex? Unless we can measure it and determine just how the flex curve is shaped at various degrees of loading, and as you point out how it behaves dynamically, trying to understand what's happening as a result of changes in design and construction becomes a fuzzy gestalt of what "feels good".
  8. We can precisely describe/draw the sidecut shape. Our ability to describe flex is very limited. "Soft", "firm", various numbers with one or more decimal places. To me this is part of the problem we have in describing and understanding the interplay between sidecut and flex. Another part is how reproducible a flex curve is i.e. can a builder make a number of boards with an identical flex profile, or how much variation should we expect given that most are wood cored, and wood is not a consistent material.
  9. @johnasmo I was reading your just posted comments (Whitefish videos) about the complex curves used for the sidecut shape of the Contras you were testing at Whitefish at the end of the 20/21 season. I can see that at board inclination angles below 45 degrees sidecut is probably the major factor affecting turn shape, but it would seem to me that the flex profile curve would transition to become the major determinant above 45 degrees. This interaction and transition is something I've not seen addressed here before. Could you comment on the interaction of flex & SCR generally, but also for the Contra prototypes you had designed and were testing? Thanks in anticipation!
  10. I've used pieces of cut off boot plastic, and a soldering iron to melt it, to fill no longer needed screw holes that were potential points of moisture/snow entry.
  11. If you were a dinkum Aussie it'd be green and yellow! Can't think of anywhere in particular where All Black is the favoured colour scheme.
  12. "Alpine Testing Lab"!!! Jealous doesn't cover it. Dream occupation for almost everybody who hangs out here. Reviews? Or are these boards so early in the prototyping process that they too much of a work in progress?
  13. @lonbordin The references above state the speed difference as a result of structure can be between 0 & 10% of the skiers total speed. Do you know if this is in straight glide i.e. not on edge, or under race course conditions. Intrigued also that higher speeds and more water under the base favour coarser structure patterns. That might suggest for a carving snowboard to structure the base 3cm in from the edge coarsely all the time given the high pressures and speeds that area is subject to.
  14. I've had base grinds on boards for 2 reasons. 1/When I've put in a set of extra binding inserts to convert an older board to UPM plate pattern. Done this on several boards in my plate experimentation phase. 2/ Once on my RadAir Obsession after buying it second hand for a minimal cost. Base was fairly deeply marked with dirt in the marks (white P-Tex), plus both edges had areas of pitting from rust damage. The tech in the shop was sceptical about how much he'd have to take off to get any kind of reasonable result. One pass and the base was spectacularly cleaner/smoother and the edge pitting was pretty much gone. I have no intention of putting it through anything that will necessitate another base grind.
  15. Might have to retire my faithful GoPro Silver3+. The 9 sounds pretty darn good. PS: The YouTube reviews I've watched consistently suggest that unless you're like a kite surfer who mounts the camera on the kite, that the 8 represents better value than the 9 for most users. I am now planning to upgrade to the 8. If I had a 7 I might wait to see if there are firmware upgrades for the 9 or wait to see what the 10 brings. (planned obsolescence as a continuing income stream strategy is alive and well!)
  16. A study in clean, apparently effortless, carving. Dave's body appears to do so little, balanced over the middle of the board, yet the board flows from edge, to edge, to edge, ..... board turning rider, not the other way round.
  17. https://link.springer.com/article/10.1007/BF00849563 @daveoYou might think that, I couldn't possibly comment.
  18. So, you didn't like the performance, or the colour. Ask @JRAZZ all the best bindings are purple !
  19. One gals pink is another guys purple. Looks like a great day was there for the having. And a cool combination of colours, white, grey, and PURPLE!
  20. GoPro unfortunately don't make an accessory that produces John's riding and rider tracking skills. That's the video production tool most deficient in my toolkit.
  21. @daveo Chest mount Imgur link: https://imgur.com/a/7otM1p7
  22. Thanks @1xsculler My cardio-resp fitness is as good now as it was pre-event. I'll happily ride a 100km or climb 1000m during a fitness mountain bike ride.
  23. It's even better to have the buddy with the camera on skis. I had thought that my head would be a good gimbal, and set up a chinbar GoPro mount on a full face helmet. But with the amount of traffic where I normally ride the amount of head movement from me maintaining situational awareness makes for poor footage. Tracking someone else riding is generally a different thing from recording one's own freeriding. There I'm concentrating on keeping them in frame and the distance right, rather than trying to carve myself. Again, traffic levels make a big difference to how safe being so fixated on one place while riding. @daveo I'll get a photo and post it over the weekend.
  24. In my hands a chest mount is steadiest. I have a DIY one using a large plastic plate against my chest to minimise shake and integrated into my hydration backpack straps. Hand helds shake, helmet mounts move as your head tracks the traffic around you. Stabilisation software during processing essential for most human mounted shooting. A powered gimbal makes a big difference. Drones that track the rider do a great job where they are permitted.
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