 Poster: A snowHead
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I recently saw a salomon BBR review by phil smith (http://www.snoworks.co.uk/blog/?p=4687), in which he measured that the BBRs normal turn radius of 13.5m is reduced to 10m at 40 deg edge angle, and an amazing 5m at a 65 deg angle. That raised a few questions from me:
According to my understanding, which may well be incorrect, the reason that an increased edge angle gives a shorter radius is because you have to pressure the ski more to stay in balance during the turn, which bends it more and thus changes the skis shape more...it is not due to a different unloaded sidecut radius when at 65 deg compared to 40 deg.
I know when i crank up the edge angle on my SL skis during a turn i can feel the radius decrease, but not to 5m or so! I assume the BBRs are less stiff than SLs so bend more & thus decrease the radius more?
Anyone got any similar data for conventional eg SL / GS skis?
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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The stated radius of the ski is, if I understand correctly, the radius of the circle drawn if you take the curve of the sidecut when the ski is laid flat and extend that curve through to a full circle.
The turn radius of any ski is hugely variable depending on many factors including the Construction of the ski, weight/pressure/edge angle applied.
The BBRs are pretty soft and I found them unpleasant to ski compared to other all mountain skis that I have used over the last year.
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Ah! It's a while since we had one of these..... 
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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spiceman, as mentioned by skimottaret, these skis aren't particularly stiff longitudinally so will probably bend quite easily, such angles they are referring to I'd imagine would be from soft ish groomed onwards, I'm not sure if they would be torsionally stiff enough to hold such angles on crusty hardpack like your SLs probably could.
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| Quote: |
The stated radius of the ski is, if I understand correctly, the radius of the circle drawn if you take the curve of the sidecut when the ski is laid flat
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so in this case, you will never achieve a carved turn with the stated skis sidecut radius, as to get it onto an egde when it is weighted/pressured and therefore must be bent to some degree more than the stated sidecut radius.
unless skimottaret, is correct, in which case this is the radius at a 10 deg angle so some ski bending is implied and this is different from the flat ski sidecut radius.
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| Quote: |
The BBRs are pretty soft and I found them unpleasant to ski
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pretty much what i thought when I saw a 5m radius could be achieved at a high edge angle - the numbers sound impressive at first, but i think means the ski must be flapping big time. Imagine skiing at speed with a low angle, then cranking onto the edges hard - going to a 5m rad is going to eject most skiers pretty quickly! Having said that I havent skied the BBR..but in the original vid we have a couple of well rspected (albeit salomon sponsored) skiers singing the BBR praises
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Quote
"so in this case, you will never achieve a carved turn with the stated skis sidecut radius"
No because the sidecut radius is only a description of the skis geometry.
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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The newer edition of the Ron LeMaster book has a table on the effect of edge angle on turn radius. My copy is in France, but if anyone has a copy then it would be a useful post.
One of the useful snippets from Fastman's DVDs is that the sidecut radius defines the maximum turn radius you can cleanly carve - notwithstanding gra's comment about it being impossible without some edge angle.
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FlyingStantoni, ahh good memory, i think that is where i got my rough figures from
Le Master says "A good approximation for the carving radius of a torsionally stiff ski held at an edge angle of 45 degree on hard snow is 70% of the skis sidecut radius. At 60 degrees the carving radius is 50%"
I woudl guess most decent skiers can hold a 45 degree edge angle carve more than that you would need to be pretty handy.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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It's not all about sidecut. The greater the edge angle, the greater the horizontal component of the reaction that acts perpendicularly through the ski. That's the centripetal force that pulls the skier round the turn.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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It's just a gut reaction response as I don't understand anything about this, but I wouldn't have said that edge angle would have much of an effect vs. the effect that bending of the ski due to the pressure that a skier puts on it through a turn. As mentioned above - I thought the stated turn radii were usually theoretical and governed by the dimensions of the ski itself. Surely what you can get a ski to achieve is determined by the skier?
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| Megamum wrote: |
| Surely what you can get a ski to achieve is determined by the skier? |
OF course: including how much edge he can give it, and how much it he can bend it (both of which are also dependent on the ski).
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You know it makes sense.
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| Megamum wrote: |
| Surely what you can get a ski to achieve is determined by the skier? |
Yes, the skier has a huge influence, but just as important is the shape of the ski if that is what you are using to predominantly form your turn. There is a massive difference in carving a ski with a 12m turn radius and a 23m turn radius.
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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There is some confusion here, I think. To a good approximation it is *only* the edge angle and ski geometry that determine the radius of a pure carved turn. Because of the sidecut, as edge angle increases, the ski *must* bend to an (approximately) unique profile for the entire edge to stay in contact with the snow. That profile determines the radius of the turn, and the radius reduces continuously as edge angle increases.
The forces are secondary - if the ski is so stiff that the skiers accelerated mass is not sufficient to bend the ski to the profile required by the edge angle, the ski will skid. If the skier is not strong enough to resist the increased acceleration, they will either reduce edge angle, skid, or fall. For a given ski and edge angle the radius is fixed, and the skier can only alter speed within a limited range by changing the balance of inclination and angulation (i.e. moving the position of their centre of mass without changing edge angle).
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