Thanks for the refined info. I’m sure your answers will help others mull things over as well. Looks like JASP has already gotten into the same areas I was concurrently writing up. I too think strength is nice to have though not really necessary when dealing with this particular issue.
To me, the key info you’ve provided is the combination of:
- ‘launch starts @ 1:00’
- ‘not in linked turns’
- ‘just the legs - unless a taut body’
'launch starts @ 1:00'
Skiers looking for speed tend to choose a spiral-in turn shape. However they start their turn, the skier straightens-out the turn shape as they progress toward Apex to accumulate speed. Coming out of Apex (maybe from 2:00 onward) the skier rapidly reduces turn radius to complete the desired direction-change creating the Spiral-In shape. (This is sometimes called a ‘Cycloid Curve’ but actually it’s not. A Cycloid Curve is symmetrical whereas the Spiral-In curve is not.)
Reducing turn radius with speed constant increases Centrifugal Force (CF) acting on the skier. A Spiral-In turn increases Centrifugal Force dramatically - often faster than the skier can adjust their CM position to remain in lateral balance over the skis. This seems to fit your ‘1:00 Launch’ model as that’s near the peak increase in CF for Spiral-In turns.
It’s possible you’re holding onto the old turn a bit too firmly - perhaps for speed-control (unconscious or not) or perhaps for an extra bit of direction change. So long as we release edge-angle progressively (after 2:00 or so) and/or un-weight into our new turn we diminish (or avoid) this inherent aspect of Spiral-In turns.
'not in linked turns'
Linked turns tend to demonstrate largely the same radius over a series of turns. It’s generally when making sudden and large reductions in turn radius (Spiraling-In) that we experience the unexpected CF-Ejection thing. Yet it can still happen if we hold large edge-angles too late in turns made on steep slopes with firm or semi-firm snow underfoot.
A person standing upright across a 35-degree slope already has a ‘built-in’ 35-degree ski-to-surface angle. This means the ski’s sidecut is already acting to bend the ski into an arc - with no upper body inclination/angulation needed.
When skiing a steep slope, at turn Apex we might have our skis tipped 30-degrees. If we hold the same body angles and ski-tipping-angle into turn finish on a 35-degree slope we end up with a 65-degree ski-to-surface tipping angle at the end of our turn - the equivalent of a much tighter turn than at Apex.
In effect the slope itself creates the Spiral-In effect when we don’t correctly adjust for slope-angle late in our turns. (This is much less of a problem in soft snow since sidecut is less definitive in turn shape there)
Even if a skier progressively reduces edge-angle late in the turn on steep slopes they might not reduce edge-angle fast enough for the given slope - especially if they’re bracing against the slope late in the turn for speed control. If we don’t reduce edge-angle properly coming out of turns on steep slopes then these too end up as Spiral-In turns.
Just look closely at tracks left on many steep slopes and you’ll notice a lot of linked ‘J-shaped’ turns - turns with a stretched out Entry-thru-Apex while showing a sharply hooked finish. This is a squarish version of a Spiral-In turn.
If you experience this ‘turn ejection’ thing often on steep slopes, this may be worth exploration. Experiment with longer, more progressive finishes that include gradually diminishing edge angles.
'just the legs - unless a taut body'
This is an important thing to notice, implies a lot - and takes a whole lot of analysis to properly explore.
When skiers experience the Spiral-In Turn or the similar effect caused by steep slopes a kind of ‘differential motion’ effect occurs based on muscular tension between upper and lower body.
For the most part, lower body components (foot, lower leg, upper leg, and hip) are laterally aligned perpendicular to the base of our skis whether we’re turning or not. When we Angulate our upper body components are no longer aligned perpendicular to the base of our skis because we’ve tipped the upper body to the side. Any thrust against the base of our skis pushes directly up through the Mass of lower body components - but pushes Off-Center against the Mass of the upper body because the upper body is now to the side of that thrust. Unless we do something to compensate, any unexpected thrust coming up through out feet causes our whole body to Rotate Sideways toward the outside of the turn.
For Spiral-In turns the large thrust against the bottom of our feet increases exponentially due to the rapidly decreasing turn radius. Late in this process the thrust may be so great relative to what we normally perceive that we experience it as a ‘Pop’ or Catapulting sensation.
This is the primary source for the feeling of ‘Pop’, ‘Ejection’ or ‘Rebound’ that we perceive from our skis as they execute a very sharp turn. Ski elasticity (stiffness & flex pattern) contributes to this - but much less so than the sudden angular acceleration caused by the rapid increase in thrust-intensity from the more-sharply turning ski.
With this in mind we should consider how a skier’s upper body and pelvis together have much more Mass than lower body components. we also need to realize that the skier controls how much of the energy directed into their skis gets transferred further up the skier's body.
If while Angulated, we maintain passive tension between upper and lower body then any ‘rebound energy’ directed perpendicular into the base of our skis can be used to ‘toss’ our skis to the Outside of the New Turn using energy provided in the last moments of the Old Turn while our upper body continues moving in the same direction it was already going. Relative to the skier, any upward component of the ‘pop’ can be absorbed internally while the lateral component is used to shift our skis to the other side of our body re-orienting us for New Turn inclination.
If we stiffen upper/lower body connective muscles then any ‘pop’ will be partially directed into our upper body Mass offering a variety of potential outcomes. This gets complicated since every outcome depends on an *exact mix* of muscular tensions, degree of angulation, rate of Spiraling-In, execution timing and a well-synchronized position for our CM.
In general though partial muscular tension is probably the most useful allowing us to direct ‘pop’ from our skis into useful purposes like un-weighting, missing a rock, whole-body reorientation into the next turn, etc. Too much muscular tension between upper and lower body is likely to result in an uncontrolled whole-body rotation toward the outside of the Old Turn (being ejected) unless we are moving closely in sync with the rapidly changing thrust from our feet.
OK, that’s quite a lot of analysis, but it does seem to support your experience of ‘just the legs’ being ejected unless you ‘stiffen up’. Since I was in Verbose-Mode tonight, my typing-fingers are quite winded so I’ll leave it to others to provide training ideas and solutions.