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Side Cut Variation in Racing


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Feel free to move to the "racing" sub-forum, but thought this would have broader interest.

Was talking with a buddy yesterday about this:

What do you think are the pros and cons of tighter vs. longer sidecuts on, say, a standard length 185cm GS board as applicable strictly to going faster?  

Then, to make things interesting: let's consider variations on where the longer vs. shorter radius is played out on the board... So variations in turn in vs. release, etc.   Pros and cons from the standpoint of going through a course as fast as possible?

I will delay putting forth my thoughts for the moment, as I know there are members here with more technical design prowess than I. 

What say you all?

 

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Too many variables including the rider and style but a larger SCR on a 185 board  would be faster than a 185 with a small SCR on a GS course.  Consider the rooster tail of snow thrown up by twin tip skis. The same thing happens with skis or boards with a small SCR but the snow is pushed off to the side. Not as much with large SCR boards. The best approach is to match a board to the course layout and be the best rider in the race !

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GS race coarse has "standard" size turns. This means that "perfect" SCR will depend on abilities of the racer, which determine the how fast racer rides and how high on edge racer can put the board in apex. Even 20m SCR board makes very tight turns if you put it at 85+ deg angle. Racer do not care so much about long round turns with constant radius. Usually turns are very tight only near apex, and then they "fly" straight to the next tight turn.

P.S. I am not "pro", this is just my observation, which maybe not be valid...

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In GS skiing the minimum SCR is made longer than the athletes might prefer judging by the quotes from athletes when FIS set the minimum. That would make carving tight enough turns harder and more tail sideslipping required to get the necessary entry angle to the next gate.

But watch most World Cup / Olympic level GS snowboarders and you'll see a lot of tail sideslipping or even aerial transitions to set the approach to the next gate. As far as I know, there is no set minimum SCR for GS boards at that level of competition. If that is correct then racers have SCR choices but prefer to ride with that technique.

To finish first, first you must finish. Edge loss in a rutted race course seems to be the commonest reason for failing to complete a run in snowboard GS. Board properties that help the rider cope with race course conditions may also be important in picking winning equipment.

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4 hours ago, SunSurfer said:

But watch most World Cup / Olympic level GS snowboarders and you'll see a lot of tail sideslipping

This was true some years ago, nowadays situation is reversed. Racers  mostly do very clean carving,  and very little sideslipping - which called "drifting" in their term. Which btw is very different from regular slipping/drifting turn... Please note that sometimes people by mistake think that after "air" time racers sideslipping, in really it is edge digging into snow  with huge force after "landing" 🙂.


Example of very clean racing carving:

 

Edited by dgCarve
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I think the question might also go to style. Is it better to 'power' the board into the arc for a tight turn, vs 'riding' the edge through the turn...  Obviously, the board will arc, but I would think (correct me if misinformed) that the longer sidecut would be favored by the one who 'powers' through the turn, forcing the arc, and the tighter sidecut would be for the person who 'rides' the edge more.....  I also imaging the differences of the sidecuts on a board of 180 or so would not be much more than a half meter as past that would make it hook badly...

Thoughts? Does the style make different sidescuts better, or has that math and design been so solidified now that any deviance would disadvantage the rider?

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5 hours ago, TVR said:

that the longer sidecut would be favored by the one who 'powers' through the turn,

Indeed some 'powers' through the turn. However it looks like racers do not really do that as speed and their mass pressure the board much more than you can pressure it with your legs. It looks like racers control turn size just by edge/board angle. Would be nice if some real "racer" could confirm reject this ... 🙂

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On 10/30/2020 at 9:57 AM, Alexey said:

So, taking the graph as shown, if I can get my board up to 90 degrees on edge I should be able to see my own backside ahead of me. (turn radius =0)

Rather, up at 90 degrees the SCR is making relatively little contribution to the curve the board edge follows through the snow surface. The carve curve is now determined by the flex of the board along its' length.

The true radius caculation graph is correct in that it shows the radius of the curve formed when all of the board edge is on the same plane when the board is tilted on edge. Trouble is that a carving snowboard penetrates the snow surface, and the edge depth will vary, and the board base pushes against the side of the groove/trench formed in the snow.

Edited by SunSurfer
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10 hours ago, SunSurfer said:

Rather, up at 90 degrees the SCR is making relatively little contribution to the curve the board edge follows through the snow surface. The carve curve is now determined by the flex of the board along its' length.

You can't actually carve or do much of anything on a firm surface with the board truly up at 90 degrees.  Most pictures you see of people carving, the board is somewhere around 60 degrees or so.

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What happens if we return to the original questions and discuss those.

Speed relative to scr. The contribution of variable radii along a single edge to the performance of that edge throughout a turn. Performance pertaining to how well it bites into the snow, how much energy is lost by that edge by bending the board and moving snow and what is regained upon unweighting the edge and hopefully releasing it leading into setting the next edge.

Great visual graph showing the relationship of 2 variables. Please discuss beyond that.

It isn't a question of racers vs. Freecarvers. It is a question of board performance. Please return to that.

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https://www.ski.ru/az/blogs/post/kak-kontrolirovat-skorost-v-rezanom-povorote-epizod-1-fizicheskii-mekhanizm-kontrolya-skorosti-pri-chistom-karvinge/


Im sorry but its russian language. Or google translate or ask your local guys translate it. This is very good article with answer to the question.


 

Edited by Alexey
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@Alexey Thanks, the article translates quite intelligibly with Google translate.  My only problem understanding it was the weakness of my math. But it made more sense around the motion of the front part of the ski and the importance of edge penetration control than I've come across in my past reading on this topic.

Edited by SunSurfer
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Here are a few things that might help people have a better understanding of speed, friction, SCR and modern race boards:

To keep it simple (reduce variables), let's assume all the racers stay on the exact same path throughout the entire course.  This way, it should be obvious that the racer who maintains the most speed overall will be the fastest.

So, how can a racer maintain the most speed?

1. Use methods that reduce friction/drag:

(a) The more the board bends into the turn the more friction it creates (most modern race boards bend less in the middle than previous generations).

(b) Too high of an edge angle creates additional friction (riding on the sidewall is slower).

(c) In general, riding the edge is faster than riding the entire base (less friction).

(d) In general, keeping the board/edge on the snow is faster than being in the air.

(e) A shorter/tighter SCR requires the board to be feathered to stay on the exact path of a larger turn radius (this will be slower than carving on the longer SCR).

(f) A longer SCR requires the board to be manipulated/skidded to stay on the exact path of a smaller turn radius (this is usually slower than carving on the shorter SCR).

(g) A variable SCR allows the rider to be more efficient, which should reduce friction.
 

2. Use methods that create energy/increase speed:

(a) Edging at the top of the turn/in the fall-line can increase speed.

(b) Use rebound energy to thrust forward/increase speed.

(c) Use terrain changes and/or pumping to increase speed.

(d) Maintaining precise tracking/edge hold helps maintain speed and can even increase speed.

Edited by noschoolrider
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6 hours ago, Alexey said:

https://www.ski.ru/az/blogs/post/kak-kontrolirovat-skorost-v-rezanom-povorote-epizod-1-fizicheskii-mekhanizm-kontrolya-skorosti-pri-chistom-karvinge/


Im sorry but its russian language. Or google translate or ask your local guys translate it. This is very good article with answer to the question.


 

There are some interesting points with proofs. There is a proof that when you ride fast and aggressive (and put your snowboard high on edge) you can control speed very efficiently in open turns, so you do not need to go perpendicular to the fall line (I love that  :-)).

As a result of this:

1) You must ride relatively fast to control speed by doing only open turns, because you have to put board high on edge. But you can do that even at very steep slopes. However for beginners it could be very challenging to start with this technique. (I personally started with "bomber" style going perpendicular to fall line, then started to move more to a "race" style and still do that :-)).

2) Do more smaller and tight turns to control the speed on steep slopes - it is more efficient than doing big turns perpendicular to the fall line (as you have to go extended time up/perpendicular to the slope to decrease the speed).  This something what Galmarini mentioned in his video (see below).

3) Bigger SCR helps you to put board higher on edge (and go faster :-)), which ultimately helps you to control the speed. Something what I found with my SG Full Race 185cm board (which is ~20 SCR) - I ride open turns, quite fast, but after archiving certain speed, it stays stable.

4) When you ride SL boards (small SCR) turns must be super tight and quick to control speed in apex. Otherwise the board will not be high on edge, and you will have to go perpendicular to the fall line to drop the speed.

This is just my thoughts, correct me please, if I am wrong.

The article states amazing fact - racers can "brake" in (open) carving turn faster than car on tarmac... 🙂 Amazing!

Another great point - if you can not control speed in (open) carving turn without sideslipping, it is not because it is impossible, it is because your technique is not good enough 🙂

It is not necessary that track must be "pencil" line wide - at high speed clean carving tracks can be more than half ft wide (because of high speed/force).

Efficient speed control in open turns - archived when you put lots of pressure on the board in apex, which means that between turns you want to put as little pressure on the board as possible. This explains why racers on steep slopes do small tight  turns and between turns go almost at straight. 

https://www.youtube.com/watch?v=UjW2RLz9cvc&ab_channel=WorldSport

Edited by dgCarve
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21 hours ago, Alexey said:

https://www.ski.ru/az/blogs/post/kak-kontrolirovat-skorost-v-rezanom-povorote-epizod-1-fizicheskii-mekhanizm-kontrolya-skorosti-pri-chistom-karvinge/


Im sorry but its russian language. Or google translate or ask your local guys translate it. This is very good article with answer to the question.

Interesting article! Google translate did an excellent job translating that to English.

That writer is quite verbose. Reads like someone who has a minimum word count on their university paper. Not terrible, just dense. 

Three things came to mind as I read that:

1. The concept of the front of the ski/board cutting the trench makes perfect sense, and also reveals why the decambered noses of modern boards are so efficient. They make for a smoother transition in this region rather than the old abrupt noses. 

2. I don't have measurements or graphs, but I believe a large part of adjusting to snow conditions on a given day/surface is finding a balance between the nose cutting and the tail riding in that groove. Firm snow permits high nose loading. Slush demands much more gradual loading, even weight biased to the rear foot. 

3. Snowboarders have one extra control parameter: Torsion imparted by two feet on one board. The graph of the ski cutting into the snow changes dramatically if one twists the board, or if the board's torsional stiffness is tuned by the board maker. Bruce from Coiler said that he adds additional cuts in his 0.4mm titanal sheets (compared to 0.3mm) to make the boards easier to slip. Much has been debated on this forum about whether 'pedaling' is good/useful or not. I certainly don't do it consciously, but put a stiff plate between me and the board and suddenly the moments entering/exiting a turn feel like I'm not in full control anymore. 

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