If I know the length of the ski (177) and the side cut (126/93/114) then how do I calculate the nominal turn radius?

Ignore me. Can’t read.

Mine have the turn radius marked on them too.

Not sure you can deduce it from those figures quoted.

For some reason the skis (2010 G3 Saints) do not have the radius marked on them. Even when I find the original brochure for the skis it only has the dimensions detailed above quoted.

Assume the ski “bends” into a section of the diameter of the circle, and that diameter, ignoring any slip, is the turning diameter??

Assume the ski “bends” into a section of the diameter of the circle, and that diameter, ignoring any slip, is the turning diameter??

Yep, that sounds about right. Now work out the diameter! 🙂

yeah I thought it was to do with how much you bend them. My instructor told me that as I was heavy I should be able to turn tighter…

I promptly fell over.

It’s not a fixed number. Imagine that if you tip the ski up on a flat surface, the centre of the sidecut would be raised off the surface. Your weight will flex the middle of the ski outward so that the edge all touches. The more you lean them the further the centre will flex and the smaller the turn radius.
If you wanted a number for comparison, I guess you could simply figure out the radius of the sidecut itself from the three widths and the length and find the circle that passes through the three points you know.

the amount of bend will depend on your weight and the stiffness of the ski – I don’t think its easy to simply derrive from the side cut dims. I’ve seen a few calculators on-line, but they vary from calculator to calculator if you plug in the same dimensions. I think it is probably brand and model specific.

Just calulate the radius from the side cut. using this handy tool to assist:
http://www.mathopenref.com/arcradius.html

I don’t think you can do it unless you know the distance from either tip to the mid-point between the two bindings, where the waist is. This isn’t the middle of the ski. (shuffles off to measure his nordicas)

yep, you need to know the distance to the waist from the tip. Using the calculator above, my Nordicas (178cm 12.1/7.4/10.6) work out at an 18m radius. They’re actually a 15.8m. Also, don’t forget that most skis’ side-cuts are parabolic.

Thanks hot_fiat. Looks like I’ll have to break out the tape measure as well then before using that calculator above. If you measure from the widest point to the mid-point do you get the right number using the calculator above.
I understand that the actual turn radius is a function of the force bending the ski but most skis also quote a “radius” which is a function of the degree of side-cut and length.

yep, you need to know the distance to the waist from the tip

Surely the distance to the contact point is the relevant dimension not the tip?

@spin: good point, especially with compound camber skis like me dad’s k2s and the o/h’s stupendous Rossignol Alias.

lot’s of funky stuff being done with sidecuts. I doubt there are many that are purely radial. increasing and decreasing radius sidecuts, compounds, kinks, quadratics.

There’s a very interesting (if you like that sort of thing) vid from the guy from Donek about tuning sidecuts to produce different turn caracteristics. I’ll dig it out when I get home if no-one’s googled and linked by then.

Lemon, that’s not the turn radius for a ski. The turn radius of a ski is his much the ski bends when you angle it on an edge assuming zero side slip, that’s why it doesn’t simply and easily relate to the side cut dims or the resulting radius of the side cut.