Technical Information Needed

Tuesday, November 16, 2004
I’m looking for some technical information on skis/bindings. I have been skiing since 1968 and enjoy a run down any trail in any conditions. My problem this year is I’ve lost some weight, about 30 lbs, and want to properly set my bindings from last year’s “heavy” values. Skied Killington last week and the first run down West Glade through the bumps was great, as a precaution I took one number off the spring tension and had no problems. But, did I go far enough? Also, does anyone ever compensate for the added weight sometimes carried - ski coat, back pack, water, all add weight – should this be factored into the total skier weight? As background info, I’m a degreed engineer and really understand mechanical systems such as a binding – very concerned when I see so called “Ski Technicians” doing a binding check which from what I observe is nothing more than verifying that the binding DIN value matches a number on a chart for a skiers ability and height/weight combination. Where do I find this chart? Has anyone experimented with different base/side wall edge angles on Volkl P50’s?

johnkuc wrote:
Tuesday, November 16, 2004
I’m looking for some technical information on skis/bindings. I have
been skiing since 1968 and enjoy a run down any trail in any
conditions. My problem this year is I’ve lost some weight, about 30
lbs, and want to properly set my bindings from last year’s “heavy”
values. Skied Killington last week and the first run down West Glade
through the bumps was great, as a precaution I took one number off the
spring tension and had no problems. But, did I go far enough? Also,
does anyone ever compensate for the added weight sometimes carried -
ski coat, back pack, water, all add weight – should this be factored
into the total skier weight? As background info, I’m a degreed engineer
and really understand mechanical systems such as a binding – very
concerned when I see so called “Ski Technicians” doing a binding check
which from what I observe is nothing more than verifying that the
binding DIN value matches a number on a chart for a skiers ability and
height/weight combination. Where do I find this chart? Has anyone
experimented with different base/side wall edge angles on Volkl P50’s?

DIN http://www.terrymorse.com/ski/din.html
The accuracy of the binding scales is such that you really can't do any
better than setting to chart based on a range - that's why the torque
release value testing is important. In Europe they sometimes measure the
diameter of the tibia head and set to this measure - I've never seen it
done in America. No one adjusts binding settings based on added clothes
weight IME.

If you're going to experiment with edge/base angles be sure to sneak up
on it - it's hard to reduce edge angle and it'll chew up alot of base to
grind out a base bevel. I'd start with a flat base and a one degree
acute edge; if you feel like you're hooking, try a 2 deg edge, 1 deg
base bevel (about what Volkl recommends, IIRC.) (FWIW, I ski my Volkls
at flat base, 2+deg edge.)

"johnkuc" wrote in message
...

I'm looking for some technical information on skis/bindings....

There are, I think, a number of discussions on this topic here (and
elsewhere).

Weight isn't the issue, it's just an indirect way of measuring what you
really care about, which is bone (and, to some extent, ligament) strength. A
DIN number is associated with a particular torque that's required in order
for the binding to release. When they use fancy equipment to test bindings,
all they're doing is checking that the DIN number marked on the little
window on the binding corresponds to the torque that it's supposed to.
They're not checking what the DIN setting "should" be. There's not a good
way to do that, short of torquing your leg until it breaks.

The variables typically used in the charts a

- Height and weight. Between them, these are supposed to give an
approximaton of how strong your bones are. Of course, this is highly
imperfect, as they don't distinguish between a 6' 200 lb guy who's built
like a linebacker and a 6' 200 lb guy who's just fat. As noted above, there
are charts that use tibia-head diameter instead: I have some that came with
Marker bindings, or at least used to. Whether that's a better measurement, I
can't say.

- Boot sole length. This is necessary to convert between torque at the toe
(where the binding is) and torque at the ankle (where the bone gets
twisted). Longer boot sole - lower setting, because, compared to a shorter
sole, a relatively lower torque at the toe produces the same torque to the
bone.

- "Skier Type." This is really in there because bindings are not perfect,
and it's necessary to balance one potential problem (not releasing when they
should) against the other (releasing when they should not). The former is
the by far the greater danger for slow-skiing beginners, while for
fast-skiing, chute-loving experts, the latter becomes more important. This
is the case for several reasons: (i) when you're going slowly, "slow
twisting falls" are more likely: falls in which the force builds up
gradually, while the endangered leg is weighted, producing lots of boot-ski
friction; (ii) when you're going fast, very short duration shocks, which
don't hurt you, can easily knock your bindings off; (iii) when you're
dropping into an icy rock-lined chute, the downside of a premature release
may be a lot worse than a mere broken leg; (iv) same thing when you're
flying along at 50 mph.

- Age. Bones get brittle in middle age.

So, really, gaining and losing weight shouldn't affect the proper DIN
setting (unless you're gaining and losing weight in your bones). Weight
you're carrying shouldn't affect anything. Sure, both of these will increase
the torque that gets applied at your boot ... but they don't affect the
torque at which the binding should release, which remains: just enough
before you break something to give an appropriate margin for error.

One final thought: it seems that the history of binding development has been
most oriented to avoiding spiral fractures. That goal has been pretty nearly
accomplished: fractured legs are much, much rarer than they were twenty
years ago. The bigger danger now is to knee ligaments. Nobody has quite
developed a binding that's really effective at protecting knees. Among top
racers, the mean time between knee injuries is absurd: something like three
years, at most.

sjjohnston wrote:

CLIP
Nobody has quite
developed a binding that's really effective at protecting knees.

I think the old Nava binding/boot combination of 20 years ago may have
effectively prevented knee injuries - it's problem was it also
effectively prevented skiing.

johnkuc wrote:

... I’m a degreed engineer
and really understand mechanical systems such as a binding – very
concerned when I see so called “Ski Technicians” doing a binding check
which from what I observe is nothing more than verifying that the
binding DIN value matches a number on a chart for a skiers ability and
height/weight combination.

A proper release check is more than simply verifying that the DIN
indicator is set to the right number. It involves actually measuring
the torque required to release the boot from the binding. For me it's
58 newton-meters at the toe and 229 newton-meters for the heel. The
modern machines that do this measurement are actually quite
sophisticated and relatively idiot-proof. I'd bet you'd be interested
in the process - ask the shop if you can watch.

Now you don't usually see this testing at the rental counter because
they don't have time to do it for every rental at the point of
purchase. Presumably, they've already done the torque test at a
non-busy time and can just set the indicator.

Anyway, the smart move is to have your bindings tested at the
beginning of every season, just as you have the brakes on your car
inspected at periodic intervals. A release check usually costs $15 to
$20, and is money well spent, if you consider the alternative.



Has anyone
experimented with different base/side wall edge angles on Volkl P50’s?

I bought my P50s from a racer who had the edges set to zero bottom /
two degrees side. I haven't changed it and it seems to work well.
Maybe a bit grabby, but I like 'em grabby.

IIRC, Volkl recommends 1 deg. bottom / 2 deg. side.


--
// Walt
//
// There is no Volkl Conspiracy

"lal_truckee" wrote in message
...
sjjohnston wrote:

CLIP
Nobody has quite developed a binding that's really effective at
protecting knees.

I think the old Nava binding/boot combination of 20 years ago may have
effectively prevented knee injuries - it's problem was it also effectively
prevented skiing.

Ain't that the truth.
then there was the turntable heel, Talk about a pre-release bandit.

"Walt" wrote in message news:k8umd.450


// Walt
//
// There is no Volkl Conspiracy

sure there is .

IIRC, Volkl recommends 1 deg. bottom / 2 deg. side.

lal_truckee wrote:

DIN http://www.terrymorse.com/ski/din.html

Here's another chart:
http://home.online.no/~stigbye/skiing/equipment/bindings/DIN-setting-1_step-1.html
or http://tinyurl.com/5djna

I went the other direction a few years ago. Adding less than ten
pounds bumped me from a DIN of 7 to one of 8.5 using the chart. Being
an engineer, I just wish they'd give me a formula instead of the
chart. Of course, if I wasn't quite so lazy, maybe I could
reverse-engineer the equation from the chart. My current
skis/bindings are unlikely to see the snow again, as they're due to be
retired. I'll be renting on my next trip.

Richard M wrote:
lal_truckee wrote:

DIN http://www.terrymorse.com/ski/din.html

Here's another chart:

http://home.online.no/~stigbye/skiin...setting-1_step
-1.html
or http://tinyurl.com/5djna

I went the other direction a few years ago. Adding less than ten
pounds bumped me from a DIN of 7 to one of 8.5 using the chart. Being
an engineer, I just wish they'd give me a formula instead of the
chart. Of course, if I wasn't quite so lazy, maybe I could
reverse-engineer the equation from the chart. My current
skis/bindings are unlikely to see the snow again, as they're due to be
retired. I'll be renting on my next trip.

There's always the racers method, wind them up until the don't come off in
the start gate


--
Chris *:-)

Downhill Good, Uphill BAD!

www.suffolkvikings.org.uk

Originally Posted by lal_truckee

johnkuc wrote:
Tuesday, November 16, 2004
I’m looking for some technical information on skis/bindings. I have
been skiing since 1968 and enjoy a run down any trail in any
conditions. My problem this year is I’ve lost some weight, about 30
lbs, and want to properly set my bindings from last year’s “heavy”
values. Skied Killington last week and the first run down West Glade
through the bumps was great, as a precaution I took one number off the
spring tension and had no problems. But, did I go far enough? Also,
does anyone ever compensate for the added weight sometimes carried -
ski coat, back pack, water, all add weight – should this be factored
into the total skier weight? As background info, I’m a degreed engineer
and really understand mechanical systems such as a binding – very
concerned when I see so called “Ski Technicians” doing a binding check
which from what I observe is nothing more than verifying that the
binding DIN value matches a number on a chart for a skiers ability and
height/weight combination. Where do I find this chart? Has anyone
experimented with different base/side wall edge angles on Volkl P50’s?

DIN http://www.terrymorse.com/ski/din.html
The accuracy of the binding scales is such that you really can't do any
better than setting to chart based on a range - that's why the torque
release value testing is important. In Europe they sometimes measure the
diameter of the tibia head and set to this measure - I've never seen it
done in America. No one adjusts binding settings based on added clothes
weight IME.

If you're going to experiment with edge/base angles be sure to sneak up
on it - it's hard to reduce edge angle and it'll chew up alot of base to
grind out a base bevel. I'd start with a flat base and a one degree
acute edge; if you feel like you're hooking, try a 2 deg edge, 1 deg
base bevel (about what Volkl recommends, IIRC.) (FWIW, I ski my Volkls
at flat base, 2+deg edge.)

Thanks for the comments, now that you mention it, I do remember long, long, long ago getting a quick measurement of the tibia for binding settings, maybe I need to look for a better ski shop! So far I have not changed my edge angles from factory specs but often wonder how they would ski if different. These are my first shaped skis (yes, I was one of those hold outs in converting from long straight skis) and I still can’t let go of fall line, quick edge change type of skiing – the long radius turns just don’t seem as fun!