Moguls and foot pressure

LiquidFeet

lurking
Instructor
Joined
Nov 12, 2015
Posts
5,127
Location
New England
@Rdputnam515, thanks.

On a mogul ski, the tails don't wash out like they do on a carver ski.

I now have an image in my mind of slightly edged mogul or GS skis, sporting a long radius (because of an almost straight sidecut), with the entire edge making contact with the mogul's snow, and resulting in almost equal pressure distribution tip to tail.

As opposed to a short radius ski (having more sidecut), same edge angle. This ski will have more pressure at the tip and the tail than at the waist, if the entire ski is in contact with the snow.

I'm reading that the second ski's tail may lose its grip and wash out, while the first ski's tail will be less inclined to wash out. I'm assuming that the equal vs unequal pressure distribution causes this difference, but not sure.

My best guess is that the variations in underfoot reaction force from the snow, situated on uneven bumps (as opposed to a nice flat groomer) will jiggle the second ski's tail loose, while the same variations in reaction force along the length of the ski won't do that to the mogul or GS ski.

Does anyone have a better explanation?
 

Sanity

Putting on skis
Skier
Joined
Jan 6, 2020
Posts
190
Location
New York
@Rdputnam515, thanks.



I now have an image in my mind of slightly edged mogul or GS skis, sporting a long radius (because of an almost straight sidecut), with the entire edge making contact with the mogul's snow, and resulting in almost equal pressure distribution tip to tail.

As opposed to a short radius ski (having more sidecut), same edge angle. This ski will have more pressure at the tip and the tail than at the waist, if the entire ski is in contact with the snow.

I'm reading that the second ski's tail may lose its grip and wash out, while the first ski's tail will be less inclined to wash out. I'm assuming that the equal vs unequal pressure distribution causes this difference, but not sure.

My best guess is that the variations in underfoot reaction force from the snow, situated on uneven bumps (as opposed to a nice flat groomer) will jiggle the second ski's tail loose, while the same variations in reaction force along the length of the ski won't do that to the mogul or GS ski.

Does anyone have a better explanation?
Maybe the carver ski hooks up too much, creating more rotational force than the trail grip can tolerate. A mogul ski won't hook up much. That's a feature for mogul skis, so that it is easy to release the edges for a quick transition.
 

Rdputnam515

Putting on skis
Skier
Joined
Feb 2, 2021
Posts
136
Location
Colorado
@Rdputnam515, thanks.



I now have an image in my mind of slightly edged mogul or GS skis, sporting a long radius (because of an almost straight sidecut), with the entire edge making contact with the mogul's snow, and resulting in almost equal pressure distribution tip to tail.

As opposed to a short radius ski (having more sidecut), same edge angle. This ski will have more pressure at the tip and the tail than at the waist, if the entire ski is in contact with the snow.

I'm reading that the second ski's tail may lose its grip and wash out, while the first ski's tail will be less inclined to wash out. I'm assuming that the equal vs unequal pressure distribution causes this difference, but not sure.

My best guess is that the variations in underfoot reaction force from the snow, situated on uneven bumps (as opposed to a nice flat groomer) will jiggle the second ski's tail loose, while the same variations in reaction force along the length of the ski won't do that to the mogul or GS ski.

Does anyone have a better explanation?
This and you are spending small amount of time on those long straight edges. The important feature for mogul skis, shock absorption, quick edge to edge, and a bit of stoutness in the tail for support.

if your tips are too hooky it’s easier to get crossed up in the bumps, off balance and youre done.
yes smaller contact point helps you bend the ski into a tighter radius but smaller contact point is more vulnerable to losing grip in uneven terrain. Think of a smaller tire patch on the road. Not necessarily jiggling loose, but less flat area for a small contact area to work on.

also remember bump skis in many cases are single purpose. Built for people that ski bumps and are at least trying to ski them fast, with style (competitors). These guys skis spend less time in contact with the snow, the large side cut is not needed for a high G ski loading event/impulse event. Quickness edge to edge is important, As well as the contact point under your feet. Remember, the tips and tails will often be in uneven spots or off the snow all together a good percentage of time.
 
Last edited:

Rdputnam515

Putting on skis
Skier
Joined
Feb 2, 2021
Posts
136
Location
Colorado
Maybe the carver ski hooks up too much, creating more rotational force than the trail grip can tolerate. A mogul ski won't hook up much. That's a feature for mogul skis, so that it is easy to release the edges for a quick transition.
And little flat area for small edge contact points to work on
 

Noodler

Just call me Sir Turn-a-lot
Skier
Joined
Oct 4, 2017
Posts
4,364
Location
Denver, CO

same retraction of heels to A$$ but from a different perspective.

Nice simple approach to skiing moguls. I really like how he emphasized over and over that it's about A&E and fore/aft balance management. That last little snippet is where you can really see him open it up and just let the skis flow through the zipper line.
 
  • Like
Reactions: Ron

SSSdave

life is short precious ...don't waste it
Skier
Joined
Sep 12, 2017
Posts
1,915
Location
Silicon Valley
Earlier in this thread, I mentioned body mechanics are more complex than generally described. Recall seeing this video in one of the Deb A. threads. Something very evident in Bobby Aldighieri skiing is how he uses subtle anticipation/countering with lower to upper body separation. The upper body turns opposite, away from the direction the lower body with skis are turning. That is something comp mogul skiing seems to judge as a negative, instead seemingly promoting a most quiet monolithic upper body. Thus instruction tends to not mention it in comp mogul technique.

Although one can learn to turn so, IMO it is non-essential negative for rec bump technique. This person has always subtly made much use out of anticipation/countering that as a useful tool modulates the changing pressure across my skis. Like Aldighieri, I may look like my upper body is quiet, actually one can see subtle countering on most turns and is especially important with what is going on in the mind flow.
 

Guy in Shorts

Tree Psycho
Skier
Joined
Feb 27, 2016
Posts
1,671
Location
Killington
These nice slow mogul turns were what @Marker and I were working on yesterday morning. Bumps were hard and icy requiring aggressive speed control. Practice under all conditions is paramount.
 

no edge

Getting off the lift
Skier
Joined
May 17, 2017
Posts
634
The sidecut consideration for bump skis needs to take into consideration the flexing that occurs due to being in bumps. When I was skiing bumps in the mid 70s I was skiing on ST650 - Rossi. They were a straight ski. But in the bumps a bent straight ski took on the characteristics of a more shaped ski. Now we see straight skis in bump competition. But the f17 had mild shape. Awesome ski.

I think that there is a lot of steering going on. I see a ton of skidding. I see gas pedal but the main reason the boots appear to come back under the hips is partly caused by the actual transition of the ski after the bump with some deceleration.

If the ski tends to wash out that is an still issue of for/aft balance and too much shin pressure to the boot cuff. But when a ski does wash out in the bumps there is so much terrain that it can be brief. That's one of the pleasures of bump skiing. It's so dynamic.
 

Ogg

Making fresh tracks
Skier
Joined
Jun 3, 2017
Posts
2,532
Location
Long Island, NY
The sidecut consideration for bump skis needs to take into consideration the flexing that occurs due to being in bumps. When I was skiing bumps in the mid 70s I was skiing on ST650 - Rossi. They were a straight ski. But in the bumps a bent straight ski took on the characteristics of a more shaped ski. Now we see straight skis in bump competition. But the f17 had mild shape. Awesome ski.

I think that there is a lot of steering going on. I see a ton of skidding. I see gas pedal but the main reason the boots appear to come back under the hips is partly caused by the actual transition of the ski after the bump with some deceleration.

If the ski tends to wash out that is an still issue of for/aft balance and too much shin pressure to the boot cuff. But when a ski does wash out in the bumps there is so much terrain that it can be brief. That's one of the pleasures of bump skiing. It's so dynamic.
They're not really straight the IDOnes have a ~20m radius.
 

no edge

Getting off the lift
Skier
Joined
May 17, 2017
Posts
634
They're not really straight the IDOnes have a ~20m radius.
I thought of that ski when I was typing. The side cut on the f17 was perfect - in my opinion. But wouldn't you agree that the terrain allows the radius to change conciderably.

Aiko Uemura... amazing!
 

Rdputnam515

Putting on skis
Skier
Joined
Feb 2, 2021
Posts
136
Location
Colorado
are we talking about competition bumps or recreational skiing of bumps, world of difference.
I’m talking about comp skis.

I ski 99mm skis as my every day, 17m radius. They are a bit wide for hauling ass through steep bumps but they do ok and they are great all over the mountain.

I would not give that up for the loss of versatility in a dedicated bump ski. Unless I hit lotto but then I would have skis based On my mood too lol.

I was suggesting that dedicated bump skis are for competitors or people aspiring to ski bumps fast and aggressive And are built almost exclusively for that purpose.
 

Ron

Seeking the next best ski
SkiTalk Tester
Joined
Nov 8, 2015
Posts
8,894
Location
Steamboat Springs, Co
fwiw, the run that Bobby is skiing is called Norther and is a great, often overlooked blue bump run that holds powder very well. The last sequence is “surprise bumps”.
 
Last edited:

Blue Streak

I like snow.
Skier
Joined
Nov 12, 2015
Posts
3,182
Location
Edwards, Colorado
Nice simple approach to skiing moguls. I really like how he emphasized over and over that it's about A&E and fore/aft balance management. That last little snippet is where you can really see him open it up and just let the skis flow through the zipper line.
Yeah, but he introduced the segment, saying that he would talk about F/F and A/E, but he never really talked about his F/F pressure cues.
Enquiring minds would like to know.
 

geepers

Making fresh tracks
Skier
Joined
May 12, 2018
Posts
2,590
Location
Australia
No point. Just interested in your opinion. If you don't see much difference in the turns, then perhaps the ski radius is a minor factor. I would love to see someone doing high edge angle turns on a mogul ski and see what it looks like for them. I found several videos comparing low angle short turns, like mine, with and without mogul skis, but I haven't seen entirely different styles on a mogul ski. Just curious. I would like to know if Tom would look the same to you on a mogul ski. The differences I usually see with short turns is much more energy in the turn. The skier typically rebounds more, catches more air, and gets higher edge angles with the smaller radius ski. Perhaps it depends on what stands out to the observer. Maybe posture has a big effect on perceived style, but wouldn't be affected much by the type of skis.

There may be quite a bit of flex pattern difference between a mogul ski and the GS style skis. However the radius will be about equal so expect the turn mechanics not to vary hugely for short radius on groomers. Keep in mind those Tom Gellie runs are on steep pitches. I've skied those pitches and anyone trying low angle turns with the skis not getting much out of the fall line (as per your 7 sec groomer vid) is going to have a run away speed issue in a hurry.

I now have an image in my mind of slightly edged mogul or GS skis, sporting a long radius (because of an almost straight sidecut), with the entire edge making contact with the mogul's snow, and resulting in almost equal pressure distribution tip to tail.

As opposed to a short radius ski (having more sidecut), same edge angle. This ski will have more pressure at the tip and the tail than at the waist, if the entire ski is in contact with the snow.

I'm reading that the second ski's tail may lose its grip and wash out, while the first ski's tail will be less inclined to wash out. I'm assuming that the equal vs unequal pressure distribution causes this difference, but not sure.

My best guess is that the variations in underfoot reaction force from the snow, situated on uneven bumps (as opposed to a nice flat groomer) will jiggle the second ski's tail loose, while the same variations in reaction force along the length of the ski won't do that to the mogul or GS ski.

Does anyone have a better explanation?

IIRC the pressure distribution along a ski is highest where most of the weight is and least where the weight isn't.

1637924567937.png


Really doesn't matter too much what ski as long as it has flex and can bend to rest of the snow. It's why tips flex from surface irregularities.

The only "ski" that would have a roughly equal pressure from tip to tail would be a rigid beam on an even surface.

Looking at those vids above on the groomers I see plenty of ski redirection. Here's one where it's very clear. Mogul ski.



What I understand is happening here is that weight is forward causing the part of the ski in front of the bindings to be engaged with the snow and allowing the lightly loaded tails to displace. So the skis rotate around some point between the front of the binding and the tip depending on how much weight is forward. It's an effective way to redirect the skis whether flat or with some edge.

Aiko Uemura

Good find. This part starting at 30:02 shows the the increased skill and athletism required as the line becomes more direct and the turns are made in the vertical (following the bump surface) rather than lateral.

 
Top