Why symmetric mounting on fatties?

[marshalolson]

great, ive been singled out as the local enginerd.

well, i was right wasn't i

[Evmo]

Done and gone with Elan, many years ago. It really just doesn't work out in principle as well as it might sound on paper. Especially nowadays with wide waists, where the point is to be more 50/50 on your skis than the 90/10 (ish) that asymmetrical mounts force you into.

According to Stockli, their new DP's (as of last season, the Silver ones) are asymetric, but not in sidecut, in flex. Apparently the inside tail is a different flex than the outside tail, so there is a left/right ski... Not sure conceptually "why", no one has explained it very well to me in the past...

[jfk]

bullet is right:
the outward rotation of your foot (duckstance) only takes place when your leg is fully extended. when your knees are bent, you shouldn't be in a duckstance (if you are, your stance is really messed up). so the whole thing doesn't really make sense.
what does make sense though is an individual stance (footbeds, shell work, whatever) that allows your foot to be in a natural position.

[BakerBoy]

BakerBoy: Those sound like exactly what my foot needs. I need new boots to replace Nordica Beasts and since Nordica is on boycott status...

How heavy are fischer boots? Nordicas are horrendously heavy (13.5lbs for a 26.5).

How do they fit on the instep?

My MX9's are just over 11 pounds on my very unscientific bathroom scale, with Booster Straps added. Same boot next year, just different liner graphics. The X-line shouldn't be any heavier...

Insteps were great for me. Not too much, and not too little -- Fischer (to their ultimate downfall) tends to go right down the middle of the road on everything freeride-wise, so that they work for the widest variety of people. That being said, the MX9's were the best fitting boots out of the box I've ever used. I didn't touch a single thing for over a season and a half other than throwing a Booster Strap on there.

FYI, the race Soma Tec used to be set at 14 degrees or something, but they downgraded it to around 7 degrees toe-out for the freeride boot line. It definitely is nowhere as extreme as the duckfoot mounts that have been on the market lately. The biggest benefit isn't really the "natural" stance, but rather having the centerline of your foot corresponding to the centerline of the ski. Edge to edge transfer is radically benefitted, IMO.

[summit]

I have a high instep but if it fits you might have just sold me on my next set of boots.

[ill-advised strategy]

hmmm...duckfoot eh?

I'm imagining some difficulty getting it precisely right without a jig.

[mntlion]

hmmm...duckfoot eh?

I'm imagining some difficulty getting it precisely right without a jig.

most fat ski jigs have reversable shims for diff width skis. you just reverse the two corners and you have a 3' offset. Diamers are harder... but same idea

[marshalolson]

Thats roughly a 40% improvement in the force you have to apply from your boot to generate the same force at your edge. Or take it the other way, 40% less force you need to generate to counteract the edge forces.

correct me if i am wrong, but isn't there a square in there?

sqrt 40 = 6.3 %

[pechelman]

correct me if i am wrong, but isn't there a square in there?

sqrt 40 = 6.3 %

I was having a hard time figuring out where you got your square from, myself.
There could be, but I dont think so. Someone please correct me if Im wrong.


My thought process;

When on edge, the torques are in equilibrium with one another.
The Torques identified as;
-applied by you to the ski
-from the ski to you by being on edge

Since Torque = Force X Distance, and torques must be equal to stay on edge, it then went that

Fe X De = Fa X Da

where sub e is for edge
where sub a is for applied by the skier

Since everything is directly related, and we know our distances,

The ratio of the forces is equivalent to the ratio of distances.

Fe/Fa = Da/De

In the above example

25/50 = .5
35/50 = .7

For a random turn, lets assume it takes 50lbs of edge force to stay in the turn.

it then goes that

Fa = .5 / 50 = 100lbs
Fa = .7 / 50 = ~70lbs

or 30% less force applied by you the skier to stay in that same turn.



my above 40% was wrong. I divided the .2 by .5 instead of .7
.2/.7 = ~.30

[ill-advised strategy]

most fat ski jigs have reversable shims for diff width skis. you just reverse the two corners and you have a 3' offset. Diamers are harder... but same idea

brilliant!

[Shepherd Wong]

here is my reason why:

the whole reason for a riser is to increase leverage on the edge. on a fat ski, you have a ton of leverage already from the width of the ski. if the ski is 100mm, you have effectively 50mm^2 of leverage (gross simplifications taken. pechel- this is prolly very wrong, so feel free to fix it - reallistically, if the ski is 100% torsionally stiff, it would be 100mm^2 and 10mm of effective lift from a 5mm riser, but whatever). by pythagoraus, with a 5mm riser, 50^2 + 5^2 = 50.24mm^2 or 1% more leverage.

basically the idea is that you are adding weight, adding damping that reduces the feel of the ski, and changing the flex pattern of the ski for no real improvement in leverage.

Fat skis give less leverage!
Fat skis have less leverage

In pictures, crank over the edge here to the right---->
.(ski is the flat bottom vertical line is center of boot)

|_

and crank it over here |_______

which is more difficult?

crank it over here,


|__

|
|
|__

Which looks easier?
Fat skis have less leverage. As a racer I found leverage didn't mean anything. It was more about not booting out, and with a fat ski you don't really boot out.
Also more leverage means less feel.

[ill-advised strategy]

agreed.

when I was racing it was all about derby/deflex plates and it was a combination of stiffening/dampening the ski and lessening boot out. I don't remember leverage ever being discussed.

[davep]

great, ive been singled out as the local enginerd.

but since you asked..
Unless Im missing something, the benefits seem to be a bit more on the torque\leverage side of things than 1%

Ive always though of stack height vs width as a leverage ratio.
Assuming we have a 100mm ski and a 25mm stack (height from edge to binding) that would be a leverage ratio of .5
ie 25/50

Now say we mount some freerides on there 34mm right?
Well whatever, lets just say its a stack of 35mm for round numbers.
so then 35/50 = .7

Thats roughly a 40% improvement in the force you have to apply from your boot to generate the same force at your edge. Or take it the other way, 40% less force you need to generate to counteract the edge forces.

and by this logic, if you mount your boot flush to the ski, it takes infinite force to edge the ski

[pechelman]

and by this logic, if you mount your boot flush to the ski, it takes infinite force to edge the ski

i ignored that the force applied by the skier is a coupled torque for brevity and clarity.

if indeed it was as perfectly idealized as in my examples, applying a directly parallel force to the base at the base would result in it sliding.

[marshalolson]

[nerd rant]

Fat skis give less leverage!
Fat skis have less leverage

a longer lever arm (ie wider ski) gives more leverage. ::highschoolphysics::

leverage = D lever x force

so unless you are reducing the force by more than you are increasing the lever arm length (D lever) - which is possible in an unskilled skier, or a torsionally soft ski, leverage increases with increased ski width.

once mass is set in motion it resists change. The more force (weight/leverage), the more inertia, the more inertia, the more stable, therefore the more leverage the better.

leverage = D lever x force = D lever x mass x acceleration

acceleration is proportional to lever arm length (right pechel?), so

leverage = (D lever)^2 x mass x c

[/nerd rant]

[lemon boy]

I'm gonna kick all you nerd's moms heads in if you don't shut up soon. Jesus christ.

lemon boy = always rollin with the jacked up risers

[pechelman]

[nerd rant]

a longer lever arm (ie wider ski) gives more leverage. ::highschoolphysics::

leverage = D lever x force

so unless you are reducing the force by more than you are increasing the lever arm length (D lever) - which is possible in an unskilled skier, or a torsionally soft ski, leverage increases with increased ski width.

once mass is set in motion it resists change. The more force (weight/leverage), the more inertia, the more inertia, the more stable, therefore the more leverage the better.

leverage = D lever x force = D lever x mass x acceleration

acceleration is proportional to lever arm length (right pechel?), so

leverage = (D lever)^2 x mass x c

[/nerd rant]

bringing dynamics into this, damn.
yea acceleration increases with an increase in distance.
there are increases in both tangential\linear and centripital accelerations.

most definitely a wider ski can produce more torque\leverage but I think what the other folks are pointing at is that with the same binding rise it makes it a little more difficult to apply that same leverage due to a decrease in mechanical advantage (what I called a leverage ratio above).

but yea, like you said marshal, for a strong skier, stiff skis and boots, you can apply more force\leverage with a wider ski.

its the reason why you see hydraulic actuators located stupid close to the pivot axis on things like cranes etc. They can produce a stupid amount of force, therefore they can create large boom displacements with small actuator piston displacement. Its the whole premise behind mechanical advantage.

This is a similar advantage of a wider ski in that you can make your edges engage earlier since you need less knee movement to tip them to the snow.
The downfall ofcourse is then that you have less precision when doing so due to a large motion ratio.

[freak]

The biggest benefit isn't really the "natural" stance, but rather having the centerline of your foot corresponding to the centerline of the ski. Edge to edge transfer is radically benefitted, IMO.

oh, i like the "natural" stance... dramatically reduces the hurting knees in the evening i had when i was skiing the first day after some weeks of skiing-absence...
but that was the only effect i noticed until now. but maybe im not a good enaugh skier to notice the difference...
but i really like my somatec boots (f9000ti) and can recommend them, you only have to be careful with the liners

freak~[&]

[Skier]

On the subject of Fischer boots:

Last year I rode part of the season on the Fischer MX Pro which is basically the MX9 with a stiffer flex pattern. The 'duck' stance is not very pronounced in the MX line and not as prominent a stance as in the Race line. Other manufacturers(some Atomic and Nordica models) also incorporate a duck footed stance in their boots but they do so with the angulation originating from the heel and not the midfoot as with Fischer.

As a poster alluded to earlier if your knees are bent they will resist a duck footed stance. When your knees are straight and locked they will naurally try to angle into a duck footed posture due to the anatomical reality of your allignment and posture. Not too many skiers I know spend a lot of time with their knees locked in an upright posture.

The fit of the MX Pro is good for medium to slightly wide forefoot but has a relatively low instep compared to other models I have ridden and caused some pain around the navicular. It is realtively upright in stance and has a pretty good heel hold. The liner packs out quick though so consider downisizing or going with a third party liner. The flex on the MX Pro was relatively stiff for a non race boot. As far as the ride I found that the greater I flexed the MX Pro the less precise my edge control was and I spent a lot of time having to make corrections with balance. It takes some getting used to and I did not like the feel. Everyone is different though. The gear guys at Footloose sports said they even had some skiers who simply could not ski the MX line at all due to the stance.

The 'duck footed' stance is not real noticeable when trying the boots on or walking around but once you get them on the snow you definately can tell something is different and can tell. I believe 'duck footed' is not for everyone and I suspect it would benefit a certain anatomy. Keep in mind when your knees are bent being in a duck footed posture is not 'natural'.

[Yossarian]

...

I'm still just in total shock from your last (first) post that "Skier" wasn't already taken as a name.

[Fatty]

And if you're naturally duckfooted?

[fiddler]

hmmm...duckfoot eh?

I'm imagining some difficulty getting it precisely right without a jig.

Very technical stuff hard to totally understand until this, a duck doing a jig, now that I can understand

Sorry....

[fiddler]

More to the point than my last post, I have a very pronated stance, when I sit on the chair my ski tips are way apart. Trying to ski a flat ski is a bit of work, I always seem to be somewhat on my inside edges but I've adjusted to it over the decades. Now I'm curious about whether the stance in those Fischer boots would help that circumstance. Canting the boots or bindings has always been the suggested remedy in the past.

[BakerBoy]

More to the point than my last post, I have a very pronated stance, when I sit on the chair my ski tips are way apart. Trying to ski a flat ski is a bit of work, I always seem to be somewhat on my inside edges but I've adjusted to it over the decades. Now I'm curious about whether the stance in those Fischer boots would help that circumstance. Canting the boots or bindings has always been the suggested remedy in the past.

They've got the MX9 at Yeager's. You can stuff some socks in the toes of mine. It really is far more subtle than one might think. It's not a drastic toe-out like that binding mount pictured in this thread. More along the lines of a few mm this way, and few mm that way...

[Shepherd Wong]

[nerd rant]



a longer lever arm (ie wider ski) gives more leverage. ::highschoolphysics::

leverage = D lever x force

so unless you are reducing the force by more than you are increasing the lever arm length (D lever) - which is possible in an unskilled skier, or a torsionally soft ski, leverage increases with increased ski width.

once mass is set in motion it resists change. The more force (weight/leverage), the more inertia, the more inertia, the more stable, therefore the more leverage the better.

leverage = D lever x force = D lever x mass x acceleration

acceleration is proportional to lever arm length (right pechel?), so

leverage = (D lever)^2 x mass x c

[/nerd rant]

What's your lever arm for me and for my ski? What I'm thinking is that force(me) is me edging, and lever(me) is the distance from the knee(or top of boot) to edge(not center of ski). the edge is the fulcrum. The force I'm balancing is force normal to ski(my fat ass on top of the ski on the flats or a combination of that and centrifigual force from a turn) and the lever arm is from the edge to the center of the ski. In equalibrium--
Force(me on boot)*lever(top of boot to edge)=Force(fat ass pushing down on center of ski)*lever(edge to center of ski)
So with a fat ski, lever(ski) increases while lever(me) only increases by a goofy radical function which is less than lever(ski) increases, therefore force(me) must be greater to balance the force(me cause of my fatness) over the ski.