Sidecut radius

[kjl]

Hey, fellas - I hope you have been having a good summer so far, and I hope (like everybody else here) that the search for a new factory to produce the Swoard is going well!

I am bored because it's summer and I can't go riding, so I have a question regarding boards that I wonder if you could answer . Why do the shorter boards have a shorter sidecut radius? As I understand it, the sidecut radius would determine the top speed one could ride at a certain edge angle while still carving. That is, at any given edge angle (say, leaning the board over 75 degrees or more to extreme carve), a longer sidecut board can be (or must be?) ridden faster than a shorter radius board.

The reason I ask is twofold:

1) I like to ride fast, so I think I would like a 13.3 m sidecut. But I am short and have small feet, so am perfectly sized for the 161M, and besides, I enjoy having a small board - very maneuverable. So what I really want is a 161M with a 13.3m sidecut.

2) Sometimes I feel on really steep slopes, I gain so much speed during the course of the carve that I end up at the bottom going faster that the board wants to go. That is, by the end of the carve, my speed exceeds that which the sidecut radius can support. Most of this is because my technique is still poor (as Patrice and Nils can attest to, right? ), but I was thinking that because I am comfortable with speed and less comfortable with leaning the board over 80 degrees like J/P/N, that perhaps a longer sidecut is what I should be riding?


Anyways, is there any reason to do with body weight or sizes or any other mechanic of snowboarding why the shorter boards have shorter sidecut radii?

Thanks!

[NateW]

I assume it's because manufacturers assume that customers expect short boards to be turny and long boards to be more stable at speed. Most customers probably do expect that... primarily because most manufacturers build things that way.

Things are built as if shorter people ride slower, but I don't think that's a valid assumption. Speed is a function of the rider's skill and attitude, not the rider's size.

Most ski makers have a habit of making a particular model have the same tip/waist/tail widths, no matter what the length, so the sidecut varies by length. Short models carve tighter and the long models carve wider. This bugs me... When I was shopping for skis I was in the opposite situation you're in - I was looking for a 13m sidecut but I could only find it on skis that were SHORTER than what I wanted.

Seems to me that each model of ski (and the Swoard!) should have the same sidecut regardless of length. That way each one handles similarly, and the rider's size only changes the length of the board, not the speed range for which it is most suited.

[harald]

This also have to do with torsional stiffness. If the same sidecut, for example 10 m, should be achieved on a longer board (or ski) than on a smaller board, the nose and tail width has to be increased proportionally. Since greater width will create difficulties in having the same torsional stiffness with existing materials, longer boards and skis have narrower tips and tails relative to the waist and hence a longer radius.

[kjl]

Should be easy to make what I want, then - a long sidecut on a short board looks more like a popsicle stick than an hourglass :)

[nils]

Actually Jacques designed the board with the idea of perfect adequation of board / rider. He made the 175M and then from it designed the 168H for Patrice, and the rest of the quiver... The idea was that everyboard behaves the same... It means that the 161S has exactly the same behaviour as the 175H.. A rider that is short and light will have exactly the same feelings on his 161S than on a huge baby on a 175H...
The radii are not the same, but the behaviours very similar...

Also something to keep in mind is stability in straight line... A short board with huge radius would pretty much be very hard to control since the nose would tend to bite and curve around the rider much faster than wished...
When you get fast u also need edge length for extra balance on both tips... Like a guy in a circus walking on a rope would need an extra long stick to hold for better stability... the farther the tips, the better the balance since his center of gravity would get "wider"...

Like previously said on this forum: the Swoard is a compromise for the best grip for the best EC turns... it means it might also work with longer radii on the shorter models, but the quality of the overall ride would be way uncomfy!

Nils

[kjl]

Actually Jacques designed the board with the idea of perfect adequation of board / rider. He made the 175M and then from it designed the 168H for Patrice, and the rest of the quiver... The idea was that everyboard behaves the same... It means that the 161S has exactly the same behaviour as the 175H.. A rider that is short and light will have exactly the same feelings on his 161S than on a huge baby on a 175H...
The radii are not the same, but the behaviours very similar...

The only thing that makes me skeptical is the fact that gravity does not affect heavier riders more than light riders (well, it does, but in direct proportion to mass, so that the effect on velocity is the same). i.e. if Jacques, at 82 kg, and I, at 61 kg, start at the same speed, and carve the same turn down the same slope, then we finish at the same speed as well (I do not exit out of the carve at 75% of his speed because I weigh 75% less). But his larger sidecut radius might still be carvable at that speed, whereas my little sidecut radius might not. As I mentioned before, I like to ride pretty fast - I don't want to make tight little turns at a slower speed while all the big guys get to make giant, rocketing speeds on the same steep slope :)

Also something to keep in mind is stability in straight line... A short board with huge radius would pretty much be very hard to control since the nose would tend to bite and curve around the rider much faster than wished...

Isn't that backwards? It seems like a short board with a large radius would be more difficult to turn, not easier...

When you get fast u also need edge length for extra balance on both tips... Like a guy in a circus walking on a rope would need an extra long stick to hold for better stability... the farther the tips, the better the balance since his center of gravity would get "wider"...

I think that's true in principle, but in practice, I have yet to get to the top speed of a 161cm board where I get unstable along the tip->tail direction. I rode my first 157 freestyle board (and thus much smaller effective edge than a Swoard or other carving board) much faster than I ride these days, since I try to carve all the time now.

[nils]

u forgot the height ! Since a guy on 161 is shorter that the one on 175, the feeling of the turn on both boards will be the same since he is shorter
Lets wait for Jacques answer maybe tall guys are too slow for short quick boards

[WokkingMax]

u also forgot about the 'zentrifugal'force that is higher for more heavy guys at the same speed in the same turnradius (goes linear with ur mass). so the lighter guy has not as much pessure on the edge as a big one, so u need a lil smaller radius to reach the same turn radius as the heavy one (at same speed). and as nils said, i think jaques developed pretty good settings with radius stiffness etc. so that the sword in ur setting according to that lists would be optimal for EC
Btw still no news about production???? *waiting*

[kjl]

u forgot the height ! Since a guy on 161 is shorter that the one on 175, the feeling of the turn on both boards will be the same since he is shorter Lets wait for Jacques answer maybe tall guys are too slow for short quick boards

Nah, I don't buy it Jacques is 186 cm, and I am 167 cm tall, a difference of ~20 cm, but that means our center of gravity is only maybe ~10 cm difference. From the extended to the compressed EC positions, maybe Jacques gets (making numbers up) 50cm of travel (can manipulate center of gravity higher or lower by 50 cm), and I maybe get 45cm of travel (just a guess, he is 10% taller than me, so maybe he get's 10% more travel). I don't believe a difference of 5 or 10 cm of travel can matter that much in a carving turn with a radius of 5m or more... but maybe I am wrong. Where are you Jacques, to refute my bad physics? Taking care of the little one maybe

u also forgot about the 'zentrifugal'force that is higher for more heavy guys at the same speed in the same turnradius (goes linear with ur mass). so the lighter guy has not as much pessure on the edge as a big one, so u need a lil smaller radius to reach the same turn radius as the heavy one (at same speed).

Actually, the radius of the turn is solely dependent on the sidecut radius and the edge angle. A lighter guy might need a softer board to properly flex the board, but a 13m sidecut on a board leaned over 80 degrees will carve the same radius arc no matter who is on it, as long as the stiffness of the board is matched to the weight of the rider.


Ah, it is all theoretical and speculative anyways I have to wait a few years for Swoard to be big enough to start offering custom models!