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Binding Centerline Position (not the typical ?)

post #1 of 16
Thread Starter 
Some of you may be aware that I made a pair of my own skis last season. One of the hardest parts was determining where to place the "centerline" of the ski.

Looking at many pairs of skis, it seams that the actual center of the side cut, which I assume should be the center of the binding, is behind the center of the contact surface. For my first design, I estimated the position by measuring several pictures out of a gear guide. In doing so, I found that the skis centerline was located approximately 55% of the skis length from the tip. This seemed to work OK, but I'd like some more numbers.

This is where you come in. Hopefully at least a few of you could help me out here while you are putting everything into storage for the summer. Here is what I need:

Ski: Maker/model
Specified Length: Length printed on ski
Contact Length:
Optional, but very helpful. Place ski on a flat surface, then measure from where the tip contacts the surface to where the tail contacts the surface.
Tip: Dimension printed on ski
Waist: Dimension printed on ski
Tail: Dimension printed on ski

Distance to Binding Center:
This one is a bit trickier. Ideally, measure from the front contact point to the printed centerline. Alternatively, measure from the tip to the same line (less accurate for me due to tip design, but quicker). Please specify if tip or contact surface was used.
  • Mount Details: If the skis have multiple specified mount points or are mounted custom, please specify this as well (i.e. "Park" mount or +5cm). This will help me to determine if the specified centerline might be off.
Any units are fine, I will convert to the metric system when I toss them into a spreadsheet.

Thanks!!
post #2 of 16
Thread Starter 
I'll start:

Ski: Atomic Metron B5
Specified Length: 172cm
Contact Length:
1463.675mm
Tip: 133mm
Waist: 76mm
Tail: 116mm
Turn Radius: 12m
Distance to Binding Center: 822.325mm Contact Surface
  • Mount Details: "Forward" position
post #3 of 16
Thread Starter 
Another:

Ski: "Blue Cheese" prototype
Specified Length: 172cm
Contact Length:
1406.525mm
Tip: 114mm
Waist: 75mm
Tail: 104mm
Turn Radius: 13.6m
Distance to Binding Center: 768.35mm Contact Surface
  • Mount Details: Prototype
post #4 of 16
I don't know if this helps any, but on all of the 7-8 skis I have measured in the last couple years, the boot center mark is between 6.5 and 9.5 cm aft of the chord center (halfway point between tip and tail contact points). It's a fairly consistent range. The ski lengths have been 175cm to 186cm. There is not necessarily a correlation with length or ski type.
post #5 of 16
Thread Starter 
That does help, and is related to what I was finding with the pics out of the gear guides. I have a feeling that if you were to look at the 6.5-9.5cm range compared to the 175 to 186 length there would be some common ratio.
post #6 of 16
What works for me, for all my skis, is to have the ball of my foot at the mid-point of the running surface of the ski.

The running surface is measured from the point where the shovel of the ski contacts the snow to the point in the tail where it starts to bend upward. I mark the mid-point on the side of the ski.

I mark my boot where the ball of my foot is - with your foot in your boot you can tap the boot with a ball peen hammer to feel the position of the ball of your foot.

I line up the mark on the boot with the line on the ski and that is where the boot is going to be - the binding is then set up to hold the boot in this position.

Basically, this positions the boot so that there is just about the same amount of lumber in front of the ball of the foot as there is behind the ball of the foot. This allows for quick pivoting in the bumps and fast edge to edge carving. For pure speed, you might want to be 1 cm back, but for most of your skiing this position works best.
post #7 of 16
The BOF on center of RS method works well for me on tele bindings. Here's a description on measuring.

And one method for finding center side to side.
post #8 of 16
I like the BOF/CRS method in the sense that it gets people to at least put some thought and understanding into mount points. Myself, I prefer to be a little back of BOF/CRS in most cases, say 1-2cm. For most skis, the manufacturer's center mark puts me about 1-3cm behind a BOF/CRS match. A few have been vastly different -- my Elan M666 and Mag 12 put me ahead of BOF/CRS, and my Atomic Sweet Daddys put me about 6cm behind BOF/CRS. In both of those cases, I did not like the feel of the skis at all, and later adjusted to the 1-2cm range.
post #9 of 16
Thread Starter 
Guys,

I'm not sure that my original intent was clear. This isn't really a BOF/CRS mounting issue, it is more of an issue in locating the center of the sidecut.

I appreciate the comments, but, if you could, please stick to my example.
post #10 of 16
Sorry, playing off previous post but thought it useful for general consumption.

If you want, I can draw what I think you want. To find center of side cut, how about taping a string (or use a long straight edge) to contact points and measure the longest distance from string to ski edge.
post #11 of 16
Thread Starter 
Quote:
Originally Posted by Alpinord View Post
Sorry, playing off previous post but thought it useful for general consumption.

If you want, I can draw what I think you want. To find center of side cut, how about taping a string (or use a long straight edge) to contact points and measure the longest distance from string to ski edge.
No hard feelings, I appreciate any help, I'm just looking for something really specific.

Yes, that would give me the location of the sidecut center. I figured that this would most likely be a little to much to ask for though, so I went with the assumption that the majority of mass produced skis are going to have the mount point located close to the sidecut center.
post #12 of 16
Quote:
Originally Posted by krp8128 View Post
Guys,

I'm not sure that my original intent was clear. This isn't really a BOF/CRS mounting issue, it is more of an issue in locating the center of the sidecut.

I appreciate the comments, but, if you could, please stick to my example.

What, you wanted useful info? I don't think we know how to do that here.

Quote:
Originally Posted by Alpinord View Post
Sorry, playing off previous post but thought it useful for general consumption.

If you want, I can draw what I think you want. To find center of side cut, how about taping a string (or use a long straight edge) to contact points and measure the longest distance from string to ski edge.

Terry, I think he's trying to determine where most off-the-shelf skis have their boot center mark, in relation to CRS and sidecut center. Hence the request to build a database of sorts. I figure an engineering student who built his own skis already knows how to find the waist with some calipers!
post #13 of 16
Thread Starter 
Quote:
Originally Posted by skier219 View Post
Terry, I think he's trying to determine where most off-the-shelf skis have their boot center mark, in relation to CRS and sidecut center. Hence the request to build a database of sorts. I figure an engineering student who built his own skis already knows how to find the waist with some calipers!
Exactly.

P.S. Don't tell anyone, but I mounted my own bindings too!
post #14 of 16
As someone else said today, I should get to work (and quit multi-tasking).

Quote:
so I went with the assumption that the majority of mass produced skis are going to have the mount point located close to the sidecut center.
Isn't an Assuming Engineer an oxymoron? (Did you hear the one about why designers need engineers? I wouldn't know. : )

Skimming over, I ASSUMED you wanted actual measurements which could be measured by the string or straight edge. How do the ski markings relate to the measured sidecut center?
post #15 of 16
Thread Starter 
Quote:
Originally Posted by Alpinord View Post
As someone else said today, I should get to work (and quit multi-tasking).



Isn't an Assuming Engineer an oxymoron? (Did you hear the one about why designers need engineers? I wouldn't know. : )

Skimming over, I ASSUMED you wanted actual measurements which could be measured by the string or straight edge. How do the ski markings relate to the measured sidecut center?
It is ridiculous how many things get assumed in engineering. Fortunately, I spend a good part of each day studying the math that makes these assumptions and simplifications valid.

The ski markings do not necessarily relate to the sidecut center. I want to have a record of them to see what happens, i.e. contact length vs. marketed length. I figure this might end up being of some use to others as well, plus it is the easier part of my request.
post #16 of 16
Quote:
Originally Posted by empressdiver View Post
What works for me, for all my skis, is to have the ball of my foot at the mid-point of the running surface of the ski.

The running surface is measured from the point where the shovel of the ski contacts the snow to the point in the tail where it starts to bend upward. I mark the mid-point on the side of the ski.

I mark my boot where the ball of my foot is - with your foot in your boot you can tap the boot with a ball peen hammer to feel the position of the ball of your foot.

I line up the mark on the boot with the line on the ski and that is where the boot is going to be - the binding is then set up to hold the boot in this position.

Basically, this positions the boot so that there is just about the same amount of lumber in front of the ball of the foot as there is behind the ball of the foot. This allows for quick pivoting in the bumps and fast edge to edge carving. For pure speed, you might want to be 1 cm back, but for most of your skiing this position works best.
Let's agree to change your last comment to "for most of my skiing that is what works best for me"
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