Ski Builders Forum

As I understand it, in SnocadX, the sidecut bias is the center of the sidecut radius in relation to the center of the ski. I printed out a design last night with the sidecut bias set at the centerline of the ski, and it looks funny. Seems to me that all my commercially made skis have the center of curvature set somewhere behind the center of the ski, but without a physical reference I'm just going from memory and pictures.

What is a good measurment for sidecut bias? It looks like all the Kam's skis have zero bias, any advantage/disadvantage to this?

I changed mine around by playing with different combo's of bias, tip length, running length etc. I wanted mine to be a bit different to suit my beginner style and give me fast, easy turns on icy groomers I ski around here. So on a easy turn the ski should turn like my Rossi's do, but if I lean a bit fwd the fat tips should cut the radius down quite a bit, turning me faster and keeping me from flying in to the Mississippi (I ski Chestnut mtn).

To get that I had to 'trick' the software by creating something I didn't want, then manipulating it to the sizes I needed, with the profile hopefully coming out right.
The nose was easier.. most of the changes to the bias center point came from playing with the tail length and width after the sidecut was set.

There are a couple of other things I've forgotten about that affect it. I'll load it up on my linux box tomorrow and try to remember what it was..

Standard design puts the sidecut center (waist) behind the MRS (mid running surface. Rule of thumb is 55% of the running surface. I use a
standard length of about 2.75 inches which is the average distance from
the ball of the foot to the center line of the boot. From what I read, the
ball of the foot should be on the MRS and the centerline of the boot should
mount on the waist. For jibbers, it is a different ball game. They mount way forward which makes powder skiing a bit of a challenge.

We (me, BigKam, and Kelvin) tend to put zero bias on our skis because they're designed for tele. Typically tele skiers mount their skis dead center or in my case forward of center.

Cadman,

I don't know how I missed your post initially, but thanks! This is exactly what I needed to know.

I actually just came to the same 55% number myselft this morning. All of the pictures in a gear guide I have lying around are scaled to 245mm, so I took a few measurements and found that the sidecut bias varies from about 53%-56% of the RS for most skis.

krp8128,
I'm borrowing the thread but I think it's still kind of on topic.

littleKam,
when you put zero bias on your skis, how do you make the correct taper, i.e. difference between tip and tail width? Do you draw a tangent line from the arc giving you the wanted taper, or do you use two arcs with different radius?

Lasse,

No problem, I think I'm done with it anyway.

Are you planning zero bias, or zero sidecut? They way I understand it, zero bias is when the center of the sidecut radius is at the center of the running surface. The sides still have a curve.

It sounds like you don't want any sidecut radius.

I'm at work right now, later I will try to make up an image of what I am talking about.

Well, maybe I was a bit vague...

If you have a defined radius on your ski and a zero bias sidecut, i.e. the waist is centered on the running surface, then the tip will have the same width as the tail. There are only a few jibbing skis that are designed that way.

My question is, when making a zero bias sidecut, what is the common method used to make the tail smaller than the tip? A tangent line from the arc towards the tail, two arcs with different radius for front and rear of the ski, or any other sophisticated way...

I see what you are saying.

When I designed my ski I used SolidWorks. I drew the tip, the waist, and the tail (to size). Then I just used a combination of splines and arcs to connect the point until I had a smooth curve that I liked. I ended up with 114-75-104, I drew one up with zero bias and one with something like -20mm.

lasse, usually the arc on a ski is not a perfect circular arc, so most people just decide on a tip with a waist width and a tail with and connect them with the smoothest line possible.
This thread explains in more detail:

http://www.skibuilders.com/phpBB2/viewtopic.php?t=785