Mid Running Surface

[Cadman]

In the past, normal cambered skis had what they call an MRS (mid running surface) which was the mid point between the forward and aft contact points.
The FCP and the ACP were where the tip radius and the tail radius started to bend up. Now that we have skis built with rocker only and no camber I am wondering if you can actually have a point on the ski where you would call
the mid running surface. It appears that drawing a vertical line at the center of the rocker is where they are putting the waist of the ski now. Others say
that is not where the waist is. Any comments here?

[rockaukum]

If I follow you correctly, I have done both. One with the standard sidecut of the ski and add rocker tip and tail. One with the sidecut reversing at the point of rocker in the tip and tail. Just a guess on this but it seems that with the reverse sidecut ski at rocker the skis seem to smeer (?) more than without. Not a bad thing but different. I actually like the feeling provided you have the room in the trees.
I kept my mounting location consistent on both models.
If this is not what you are talking about.....Oh well....
RA

[twizzstyle]

It gets more complicated in my mind as soon as you lean the ski over on-edge.

On a traditional-sidecut ski, with reverse camber, as you lean over on edge there will still be some point longitudinally on the ski where the tip comes off the snow. You end up basically in the same situation that you are in with a traditional-camber ski on edge, the ski is just "pre-flexed" when it is rocker/reverse camber.

I'm not clear what your question is (if there is any), but it's an interest thought/discussion regardless.

On all of my skis, the "center of camber" (whether it's traditional or reverse) has always been at the true center of the ski, regardless of where the sidecut waist is.

[petemorgan(pmoskico)]

im probably just misinterpreting the question but some regurgitated food for thought:


yes there is a difference in the FCP in a rockered ski compared to a traditionally cambered ski. the FCP is much further back obviously, but twizz brings up some great points. this is a dynamic measurement because the ski is in a pre-bent shape and the FCP changes quite a bit when actually leaning the ski over. you get a much longer contact surface on hardpack then when the ski is flat on the snow.

are you just trying to figure out the boot center mark on a rockered ski? i use a percentage formula of the total length of the ski. between 43-45% of the total length with more ski in front of boot center obviously.

or are you asking about where to put the center of a radius of a side cut on a rockered ski? i would try to put your skinniest spot same as my boot center location.



(yeah rockaukum i like the smeer sensation of a rockered tapered tip. )

[Cadman]

Thanks for the feedback. The reason that I brought this up was because the manufacturers traditionally put the running surface in when they were building traditional skis with normal camber. It was pretty easy to figure out the MRS since it was half the running length (from ACP to FCP). Now they want the MRS for all these rockered up skis and it doesn't appear that there is any way to acutally measure it any more. Alot of people confuse the center of the ski as the MRS. That is true as long as the tip and tail are the same length but the second the tip and tail have different lengths, the true center of the ski doesn't appear to mean anything more. The manufacturer was asking for the MRS on all the models that we were working on and I am not sure what to put down. I don't quite understand what the exact center of the ski has to do with anything unless the ski is symetrical. If anyone has some ideas on this, I am all ears. Thanks

[MontuckyMadman]

I think we need some example diagrams and shapes. If you have mrs then that is the distance between the contact points prior to bending the ski and in the middle. The sidecut is not acurate to the running surface on some modles and is on others.
Depends on the design.
I generally make the running surface acurate to the change in contact area of an unflexed or non decambered ski.
I think you are the expert here rather than the conjecture that other like me are posting.

[falls]

I would say you state running surface as the length of ski that contacts the snow when you are running along the snow flat on the bases. You can then state MRS as the middle of that distance.
However what you then do with the MRS is not the same as in traditional cambered skis. Traditionally you would mount the ball of the foot at this MRS point.
So I think RS and MRS are still definable it just isn't as relevant to where to mount the ski in a modern flat/cambered and rockered design.

edit: Oh I see you are talking about completely reverse cambered skis. I don't think you can define a running surface on those.