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Binding Ramp Angle Question

post #1 of 24
Thread Starter 
How do you guys measure the binding ramp angle? I know that it is similar to the boot ramp angle. I already know how to measure the internal ramp angle but i have no idea how to measure the length between the toe piece and heel piece. With the bootboard it is easy because all you have to do is measure the length of the bootboard.
I also know that in smaller sizes it increases and decreases in bigger sizes (just like the boot ramp angle).

I have the Marker Comp 14.0. I need to know how to measure the length between the toe and heel because i want to find my overall ramp angle (boot ramp angle + binding ramp angle).

Thanks!

Jamie
post #2 of 24
http://forums.epicski.com/showthread...inding+d elta

Hopefully, you will find this helpful.
post #3 of 24
Actually that old thread (which I participated in) didn't really discuss how to calculate the ANGLE. We were only discussing the difference in stand height between the toe and the heel. The actual angle needs to be calculated using trig.

Remember the old SOHCAHTOA numonic (I think that's what these are called):

Sine = Opposite/Hypotenuse
Cosine = Adjacent/Hypotenuse
Tangent = Opposite/Adjacent

As long as we have the heel stand height and the boot sole length we can calculate the actual ramp angle at the toe.
post #4 of 24
I just found a good link to a description on how to use SOHCAHTOA if anyone is interested: http://www.mathwords.com/s/sohcahtoa.htm
post #5 of 24
OK - a request came in to show an actual calculation. So here it goes:

Using some trig we're trying to determine the delta angle theta (here's another good link for this calculation: http://regentsprep.org/Regents/math/rtritrig/LtrigA.htm).

We know the opposite side length - that's the difference between the heel stand height and the toe stand height. We also know the adjacent side length - that's the boot sole length. So since we have both the opposite and adjacent lengths known we should use the "TOA" for our trig calculation.

tan theta = opposite/adjacent
tan theta = 5mm/301mm (using 5mm as the delta between the stand heights)
tan theta = .017 (rounded up)
inverse tan of .017 = .97 degrees

So we see that the delta angle is just under 1 degree. If the boot sole is longer then obviously the calculation will show that the delta angle will be smaller.

Note that the stand height calculations should use the distance from the bottom of the heel to the bottom of your ski and the bottom of your toe to the bottom of the ski. Subtract the toe from the heel and you'll get the delta for the stand height.
post #6 of 24
1 mm error in stand height makes a .19 degree difference whereas 1mm error in boot length is only 0.003 degrees, for the example above.
post #7 of 24
Thread Starter 
Thank you! But i have one question. The adjacent side length - should it be the boot sole length? That is what confused me.

I have found a thread on delta angle and i have to say that two bootfitters think that we should not measure over the length of the boot.
Here is what they had to say:

Quote:
Originally Posted by louis rosenfeld
actuality the ramp isn't measured over the length of the boot but over the length between the two points on which the boot or foot is suspended.

So in the case of binding ramp it is measured between the AFD and the heel pad.
Quote:
Originally Posted by bud heishman
One thing you need to consider is the angles I got were derived from using a boot sole contact point on the binding itself not the very tip of each end of the boot. the boot contacts the binding on a shorter base and consiquently affects the angle
My boot contacts the AFD in one point only. Is that the point they are talking about?
Which is the other point where the boot contacts the heel piece?
With that method, the sole length will be shorter and the angles will increase. For example, my boot sole length is 285mm. If the delta is 5 mm then the angle is exactly 1 degree. But with their method the sole will be shorter so the angle will increase.

What do you think?
post #8 of 24
Quote:
Originally Posted by Noodler View Post
OK - a request came in to show an actual calculation. So here it goes:

Using some trig we're trying to determine the delta angle theta (here's another good link for this calculation: http://regentsprep.org/Regents/math/rtritrig/LtrigA.htm).

We know the opposite side length - that's the difference between the heel stand height and the toe stand height. We also know the adjacent side length - that's the boot sole length. So since we have both the opposite and adjacent lengths known we should use the "TOA" for our trig calculation.

tan theta = opposite/adjacent
tan theta = 5mm/301mm (using 5mm as the delta between the stand heights)
tan theta = .017 (rounded up)
inverse tan of .017 = .97 degrees

So we see that the delta angle is just under 1 degree. If the boot sole is longer then obviously the calculation will show that the delta angle will be smaller.

Note that the stand height calculations should use the distance from the bottom of the heel to the bottom of your ski and the bottom of your toe to the bottom of the ski. Subtract the toe from the heel and you'll get the delta for the stand height.
you should be using sin.
post #9 of 24
Quote:
Originally Posted by freeskier75 View Post
you should be using sine.
Correct, but for small angles they're close enough. The boot -is- the hypotenuse.
post #10 of 24
thanks for the spelling correction
post #11 of 24
Quote:
Originally Posted by sywsyw View Post
My boot contacts the AFD in one point only. Is that the point they are talking about?
yes
Quote:
Which is the other point where the boot contacts the heel piece?
The point closest to the toepiece that you can't slide a knife/feeler gauge in.
post #12 of 24
Thread Starter 
Thanks!
post #13 of 24
Quote:
Originally Posted by freeskier75 View Post
you should be using sin.
Oh yeah - you're right. A big OOPS : on my part.

Yes, the boot length is the hypotenuse in this case so we should use SOH in the calculation.

sine theta = 5mm/301mm
sine theta = .017
theta = .95 degrees

So yes, the calculation is still fairly close, but comes out a bit less.
post #14 of 24
sywsyw - technically Lou and Bud are correct. The boot sole length probably is just a bit longer than the actual contact points. However, determining a true length may not add up to much of a difference in the final calculation. We're talking about tenths of a degree here.
post #15 of 24
you should be able to use the sole of the boot, you just have to be consistent with where you are measuring. If you use the entire sole, you have to measure at the very tip of the toe and back of the heel. just because its contacting the binding doesn't mean the angle is changing. (unless its actually flexing the sole which I doubt)
post #16 of 24
Freeskier:
Lou here. Actually it does matter if you use the boot sole to measure and it does make the calculation incorrect. Flexing of the sole has nothing to do with it. However, I agree with other comments that the difference may not make a huge difference in the actual answer. Sorry I don't have time to do sample calculations to give an example. Also keep in mind that as the boot gets shorter the difference between the two measurement methods will increase.
post #17 of 24
I don't get it, if you measure the height at the heel, the VERY heel, and the very tip of the toe, get the difference, that difference is over the entire length of the sole. No?
post #18 of 24
Thread Starter 
Lou,

Thank you for joining the discussion.

If you have time please do sample calculations to give an example so that everyone interested in this subject will understand.

I agree with you when you say that if the boot ramp angle and forward lean is correct for the skier, the binding ramp should be zero (flat).



Jamie
post #19 of 24
Hi guys:
Look everyone is making this too complicated. It is really very simple, but it is necessary to use trig tables or a calculator unless you get a digital level which is what I use in the shop.

Take the boot out of the equation. You are trying to determine binding ramp here, not boot ramp. To determine binding ramp the easiest way is to measure the height of the toe AFD and the height of the heel and subtract toe height (assuming it is lower) from heel height. Measure the distance between the points on the AFD and the heel where the boot contacts and follow the rules of trig (already listed on this site) to determine the angle. It is really simple but does require understanding this basic trig.

I found tables at industrialpress.com. I think most of us will find angles of between 1 and 2 degrees. Doesn't sound like much but it adds directly to boot ramp and it also increases boot forward lean.
post #20 of 24
For everyone interested in this you may also be interested in new risers from VIST called "Step Concept" There is a selection of risers with the toe higher than the heel. Some are predrilled for VIST bindings but others are just blanks and will take any binding. They also make 2,3, and 4mm shims that can be used as well. If you want to get binding ramp to zero it will only be necessary to measure difference between binding toe and heel height and then use the appropriate riser or riser/shim combination.

Lou
post #21 of 24
Thread Starter 
Thanks Lou.
post #22 of 24
Thread Starter 
Anyone who's interested in Trigonomertic Tables click here.
post #23 of 24
Quote:
Originally Posted by sywsyw View Post
Anyone who's interested in Trigonomertic Tables click here.
People actually use tables for trig functions?

Do you guys use slide rules too?

post #24 of 24
I do, yes! But don't know how to use it for trig so have to rely on tables.
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