Clothoid Sidecut

[Jack M]

On 12/18/2018 at 2:30 AM, bobdea said:

Yeah, still it sounds there’s something a little different to kessler geometry. Way back rode a few and still own one, they are just different. Some of Palmer softboot boards had that Kessler magic in ‘em too. Sounding like they STILL have some special sauce not found elsewhere. 

Can anyone explain what he does different? I know I like it but there’s never been much of explanation that I’ve seen. Other than the Palm said it feels like flying. 

There is a bit of a giveaway here:

http://www.kessler-swiss.com/en-US/technology/kesslerShapeTechnology

Seems like the idea is that the tighter radii at the ends will bend the middle of the board into a tighter arc, and the longer radius in the middle resists the tendency for the board to simply fold or kink between the feet.  The result should be a smooth consistent curve.  A clothoid curve is used in rollercoaster loops to keep g-force on the passenger constant all the way around the loop.  It compensates for the fact that the speed slows to a minimum at the top of the loop, then accelerates again.  Clothoid is also called a Euler Spiral.

I suspect that for the GS boards and maybe the SL boards, the radius is longer in the tail than the nose, but I think it may be longest in the middle.  I suspect that for the 168 (and my new 175) there is less of a difference between nose and tail radius, but again, longest in the middle.  I tried to measure the sidecut of my 168 by measuring the width of the board every 5cm.  Around the waist, the board's width is a constant 202mm for a surprisingly large span - about 15cm.  This would imply an effective radius significantly larger than 12m in the middle of the board.

[daveo]

My feeling is that it's longest in the middle, also. Front seemed tightest to me.

[pokkis]

That is also how they are in normal three radius setup, like NSR.

[jburk]

Last year I picked up a (barely) used custom Kessler 162, and got the specs directly from HK via email. 

He listed the sidecut as “7-14,14-9”, which I interpreted as “two separate spiral curves, 7m in the nose increasing to 14 in the middle, then another spiral starting at 14 mid-board and tightening up to 9 at the tail”. Makes sense if you think of it as two spirals joined in the middle. 

Magic, any way you slice it. 

[Corey]

Coiler does short - long - medium for VSR sidecuts too.  No math, just experience.  

Donek does similar, but with a progressive change defined by a mathematical formula.  Sean calls the tighter tail radius 'hook'.  

I think Thirst does the opposite, with a tighter radius in the middle, or under the feet.  I could be totally wrong, but I know the two I rode practically stopped turning when I loaded up the nose.  Stay centered for that signature Thirst ride!  

I've heard a theory that the Kessler sidecut is a factor, but the decamber is the real magic behind their boards.  Once we tilt the board up to free-carve angles, the sidecut can't be doing too much.  The nose is already turning the second it's tipped up, before the rider bends the board.  That same person theorized that the Kessler sidecut patent (available online) was a decoy to steer board makers away from the importance of the decamber profile. 

[Buell]

31 minutes ago, Corey said:

I've heard a theory that the Kessler sidecut is a factor, but the decamber is the real magic behind their boards.  Once we tilt the board up to free-carve angles, the sidecut can't be doing too much.  The nose is already turning the second it's tipped up, before the rider bends the board.  That same person theorized that the Kessler sidecut patent (available online) was a decoy to steer board makers away from the importance of the decamber profile. 

I don't think it can be anyone one thing in particular.

My impression is that Kessler is exceptional at understanding how the many design aspects of a board work together. He is able to integrate the sidecut curve with the flex, the decamber, the longitudinal and torsional flex, the characteristics of the construction materials, and probably some stuff we aren't even aware of, to produce a board where all the parts work as one.

 

 

[bigwavedave]

1 hour ago, Corey said:

Coiler does short - long - medium for VSR sidecuts too.  No math, just experience.  

Donek does similar, but with a progressive change defined by a mathematical formula.  Sean calls the tighter tail radius 'hook'.  

I think Thirst does the opposite, with a tighter radius in the middle, or under the feet.  I could be totally wrong, but I know the two I rode practically stopped turning when I loaded up the nose.  Stay centered for that signature Thirst ride!  

I've heard a theory that the Kessler sidecut is a factor, but the decamber is the real magic behind their boards.  Once we tilt the board up to free-carve angles, the sidecut can't be doing too much.  The nose is already turning the second it's tipped up, before the rider bends the board.  That same person theorized that the Kessler sidecut patent (available online) was a decoy to steer board makers away from the importance of the decamber profile. 

 

21 minutes ago, Buell said:

I don't think it can be anyone one thing in particular.

My impression is that Kessler is exceptional at understanding how the many design aspects of a board work together. He is able to integrate the sidecut curve with the flex, the decamber, the longitudinal and torsional flex, the characteristics of the construction materials, and probably some stuff we aren't even aware of, to produce a board where all the parts work as one.

 

 

Mark at Thirst emphasizes that one of the design features in his boards is something he does with the core (in addition to the asym part) that tunes it to work with the sidecut and flex patterns and the changes when the board is decambered. His sidecut curves have some secret sauce as well,  probably not clothoid spirals, but I wouldn't know. 

What I do know is if you ride a Thirst relatively neutral (which must be the way I ride anyway), it carves as smooth as any board I've ridden (Kessler, Coiler, SG, Oxess, Rev) and maybe even smoother and quieter, if that's possible. They also seem to accelerate faster through turns than my other boards while still making a nice C shaped turn. I'm interested to ride them back to back with my other boards this winter. 

 

[David Kirk]

One interesting way to analyze the shape of the sidecut is to put the board down on a strip of paper and trace the sidecut. Now pick the board up and turn it around and set one of the edges up against the line on the paper.

Interesting stuff.

 

dave

[philw]

3 hours ago, Corey said:

... I've heard a theory that the Kessler sidecut is a factor, but the decamber is the real magic behind their boards.  ... That same person theorized that the Kessler sidecut patent (available online) was a decoy to steer board makers away from the importance of the decamber profile. 

Except here's the patent for the nose decamber, so they're hardly trying to misdirect away from it. You can patent pretty much anything in Trump-Land, so the existence of a filing doesn't mean much.

[bobdea]

4 hours ago, Jack M said:

There is a bit of a giveaway here:

http://www.kessler-swiss.com/en-US/technology/kesslerShapeTechnology

Seems like the idea is that the tighter radii at the ends will bend the middle of the board into a tighter arc, and the longer radius in the middle resists the tendency for the board to simply fold or kink between the feet.  The result should be a smooth consistent curve.  A clothoid curve is used in rollercoaster loops to keep g-force on the passenger constant all the way around the loop.  It compensates for the fact that the speed slows to a minimum at the top of the loop, then accelerates again.  Clothoid is also called a Euler Spiral.

I suspect that for the GS boards and maybe the SL boards, the radius is longer in the tail than the nose, but I think it may be longest in the middle.  I suspect that for the 168 (and my new 175) there is less of a difference between nose and tail radius, but again, longest in the middle.  I tried to measure the sidecut of my 168 by measuring the width of the board every 5cm.  Around the waist, the board's width is a constant 202mm for a surprisingly large span - about 15cm.  This would imply an effective radius significantly larger than 12m in the middle of the board.

Yeah, I can tell you my Kessler SL certainly can be opened up at the end of the turn. So long radius in rear might be the case Someday I’ll get a freeccarver from him, as that board isn’t always pleasant for freeriding around on but is insane when you lay into it. The hangls don’t help, me being waaaay out of shape doesn’t either. 

[SunSurfer]

https://patentimages.storage.googleapis.com/3b/4d/81/7eaeb6f6d7df14/US9216343.pdf

For tech heads, and anyone wanting to try to understand the Kessler "secret sauce".

[Corey]

I'll have to read through in more later, but this seems to be an odd choice: they've put so much detail in there that changing any one little thing makes it a unique product that would not infringe on this patent. Many patents try to be vague so they can sue anyone that gets close to the patented product. 

[lowrider]

On 12/18/2018 at 2:41 PM, David Kirk said:

One interesting way to analyze the shape of the sidecut is to put the board down on a strip of paper and trace the sidecut. Now pick the board up and turn it around and set one of the edges up against the line on the paper.

Interesting stuff.

 

dave

This approach has me giddy inside love to see the math thrown out the window with the advantage  of simple observation. No matter what the science is behind the board a good rider can jump on figure it out and ride the shit out of it as it should be !