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Help Understanding Turning Radius

post #1 of 7
Thread Starter 
Ok so this is what I think turning radius is (please correct me if I'm wrong): how "quick" the ski will turn edge to edge, the smaller the number the quicker the ski is. If you ski a lot in tight trees you want a pretty short turning because you need to make quick short turns. If you ski in wide open powder you want a pretty long turning radius because you will be making a lot of long slow turns.Right? 

I was reading about the S7 and someone said that they think the turning radius is too short (at 15m) and it will go to like 30-40m and I thought the S7 was made for short quick turns in the trees so why would you want a longer turning radius or does he/she think the S7 is made more for charging?

thanks in advance
post #2 of 7
Welllll, not exactly. The conditions you describe, tree skiing, involve a lot of tail release to control speed and vary turn radius to move through irregular tree spacing and terrain features. The radius numbers apply to carving, that is riding the edge of the ski with minimal slip or release. So your ability to release or slip the skis, tails, may have more to do with having a soft flex and a straigher tail sidecut.

If you mean by too short that Rossignol has mis-labeled or mis-tested the ski, that is probably not exactly correct. That ski should only be discussed in terms of deep powder performance, and therefore is capable of any number of turn radii depending upon skier input.

Quickness is generally a function of energy, rebound, lively flex as opposed to dampness, power, stiff flex.
post #3 of 7
Thread Starter 
Quote:
Originally Posted by davluri View Post

Welllll, not exactly. The conditions you describe, tree skiing, involve a lot of tail release to control speed and vary turn radius to move through irregular tree spacing and terrain features. The radius numbers apply to carving, that is riding the edge of the ski with minimal slip or release. So your ability to release or slip the skis, tails, may have more to do with having a soft flex and a straigher tail sidecut.

If you mean by too short that Rossignol has mis-labeled or mis-tested the ski, that is probably not exactly correct. That ski should only be discussed in terms of deep powder performance, and therefore is capable of any number of turn radii depending upon skier input.

Quickness is generally a function of energy, rebound, lively flex as opposed to dampness, power, stiff flex.
 
Ok, so in the trees you probably want a medium turning radius because you will be doing a variety of turns?

In what conditions would you want to have a short turning radius?
post #4 of 7
The following comments refer to hard pack/groomer conditions and carving turns (where the edge creates a trough in the snow that it follows from tip to tail).

Small radius skis will make tight turns ala Slalom. Large radius skis will make bigger turns: 21 m - 27 m radius = GS style. DH skis have a radius of 45 m or over.

The length and flex (stiff/soft) of the ski is related to the size of the turn that the ski will make as well. Softer skis are easier to decamber so easier to make tighter turns. Shorter skis are easier to decamber than longer skis of the same radius and will make tighter turns more easily.

Race skis or race stylized skis are torsionally stiff and the tips and tails will grab so the ski will more easily decamber than other skis. Recreational skis have softer torsional characteristics so are more forgiving as they don't bite so much at the tip and tail and won't decamber the ski as quickly. They need greater forces at the middle of the ski to make tighter turns.

Now, to get off the groomers and into the trees or at least not carving.

Radius is less of a function than your ability to get the ski to perform a variety of turns sizes utilizing skidding, not carving. Carving results in speed so is not advantageous in the trees. Speed is ok in the trees, but only with soft snow. Soft snow lets you manage the speed easily by plowing through fresh snow (what I call using snow brakes), pushing the ski into the snow to either cause slowing or decamber and turn.

The shape of the tail is very important in determining how a ski will release a carve and how easily it will permit a skid to develop. Narrower tails release the carve and skid easier than wider tails (width being relative given skis of a particular length and similar turn radii). Turned up tails, like a twin tip, or even the less severe turned up tails that are popular (as on my Rossi B2s) make it easier to release the carve and let the tails skid.

For instance, when I ski the trees, I like my Atomic Powder Plus 165cm. It has a 30+ m radius, but is easy to skid. It is fat (130/110/120). If you went just by radius, you'd think I'm nuts to ski it in the trees, but I don't rely on radius to turn the ski. I can decamber the ski easily in soft snow and because the ski is short it will arc a very small turn. I also smear the tails which is easy because it has a tail that has corners that are rounded and don't catch in the snow easily. My 184cm B2s would work with an 18m radius, but they aren't fat enough to keep me from inadvertantly breaking through the snow. The PP is easier to control. Because it is short and fat, it is easy to pivot, even on softer snow. If I ever get shut down in the trees or get going too fast, I can generally pivot the skis perpendicular to the fall line and do a hockey stop style shut down. It can be tricky with heavier or deeper snow so I usually end up on my side to prevent going over the high side. But I've stopped and usually haven't hit anything.

So short radius is really only necessary if you want to make small carved turns. Short length skis make pivoted, jumped or skidded turns in the fall line pretty easy.
post #5 of 7
Thread Starter 
Quote:
Originally Posted by MastersRacer View Post

The following comments refer to hard pack/groomer conditions and carving turns (where the edge creates a trough in the snow that it follows from tip to tail).

Small radius skis will make tight turns ala Slalom. Large radius skis will make bigger turns: 21 m - 27 m radius = GS style. DH skis have a radius of 45 m or over.

The length and flex (stiff/soft) of the ski is related to the size of the turn that the ski will make as well. Softer skis are easier to decamber so easier to make tighter turns. Shorter skis are easier to decamber than longer skis of the same radius and will make tighter turns more easily.

Race skis or race stylized skis are torsionally stiff and the tips and tails will grab so the ski will more easily decamber than other skis. Recreational skis have softer torsional characteristics so are more forgiving as they don't bite so much at the tip and tail and won't decamber the ski as quickly. They need greater forces at the middle of the ski to make tighter turns.

Now, to get off the groomers and into the trees or at least not carving.

Radius is less of a function than your ability to get the ski to perform a variety of turns sizes utilizing skidding, not carving. Carving results in speed so is not advantageous in the trees. Speed is ok in the trees, but only with soft snow. Soft snow lets you manage the speed easily by plowing through fresh snow (what I call using snow brakes), pushing the ski into the snow to either cause slowing or decamber and turn.

The shape of the tail is very important in determining how a ski will release a carve and how easily it will permit a skid to develop. Narrower tails release the carve and skid easier than wider tails (width being relative given skis of a particular length and similar turn radii). Turned up tails, like a twin tip, or even the less severe turned up tails that are popular (as on my Rossi B2s) make it easier to release the carve and let the tails skid.

For instance, when I ski the trees, I like my Atomic Powder Plus 165cm. It has a 30+ m radius, but is easy to skid. It is fat (130/110/120). If you went just by radius, you'd think I'm nuts to ski it in the trees, but I don't rely on radius to turn the ski. I can decamber the ski easily in soft snow and because the ski is short it will arc a very small turn. I also smear the tails which is easy because it has a tail that has corners that are rounded and don't catch in the snow easily. My 184cm B2s would work with an 18m radius, but they aren't fat enough to keep me from inadvertantly breaking through the snow. The PP is easier to control. Because it is short and fat, it is easy to pivot, even on softer snow. If I ever get shut down in the trees or get going too fast, I can generally pivot the skis perpendicular to the fall line and do a hockey stop style shut down. It can be tricky with heavier or deeper snow so I usually end up on my side to prevent going over the high side. But I've stopped and usually haven't hit anything.

So short radius is really only necessary if you want to make small carved turns. Short length skis make pivoted, jumped or skidded turns in the fall line pretty easy.



Thanks! I think I understand now, and I was partially wrong.

So, the ideal "quick" ski in powder trees would be: soft flex, twin tip/rockered, wide, and short?
post #6 of 7
Quote:
Originally Posted by Downhillin99 View Post

Thanks! I think I understand now, and I was partially wrong.

So, the ideal "quick" ski in powder trees would be: soft flex, twin tip/rockered, wide, and short?

 

Short is good because it has the advantages of being to be turned sideways for emergency speed control in the narrowest places. Wide isn't essential. I weigh 200 lbs, so I need some float which I loose with the 165cm length. I have never used rockered and can't comment, but it definitely isn't necessary. My PPs are standard camber. Twin tip is nice, easily pushed tails is the desired benefit of that. Plus if you get stopped and have to back up a twin tip does 'reverse' pretty easily.

A tree ski needs to let you make a wide variety of turns. It is a jack of all trades. When there is pow, you want to float. When it is firm, you want to be able to skid to control speed. When it is tight, you don't want to snag your tips or tails.
post #7 of 7
Basically, the shaped skis create an arc when pressure is applied in the middle, they bend in and cause an arc, as you lean the ski onto its edge, that arc will cause the ski to turn by itself, because the path of travel is governed by the edge of the ski, which is now an arc.

This is what it means to me:
When going down a small hill, and leaning to one side, make a 15 meter diameter circle in your mind, and start turning, by the time you have turned 180* and now facing the direction you came from, you have traveled around half of the 15 meter diameter circle.

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