or Connect
New Posts  All Forums:Forum Nav:

One Left Turn

post #1 of 9
Thread Starter 
Here our ROBO Skier makes one left turn then a brief pause.

Tell me what we should improve...

<FONT COLOR="#800080" SIZE="1">[ December 01, 2001 04:37 PM: Message edited 2 times, by Dr.GO ]</font>
post #2 of 9
Dr. Go needs to go get a job.
post #3 of 9
Dr. GO,

Is it me or are you being a bit of a rascal here? Your "airplane cockpit" depiction above looks remarkably like a skier Bob Barnes described for us early on in the now closed HH thread.

Before offering any prescription for change, I'd like to make sure I'm reading the gauges as you intended. At the beginning (when the skis are pointed right) the skis are parallel, right ski is edged less then the left. Next the right ski is advanced slightly and then its tail is stemmed out slightly. This advance and stem occurs sequentially in a 1-2 fashion. As the right ski is advanced its edge angle is reduced. This flattening continues during the stemming movement. During this advance and stem there has been no release (reduction of edge angle) of the left ski. However the instant the stem is complete, the left ski is brought parallel and its edge angle matches the right skis. Throughout the remainder of the turn/demo the skis stay parallel and develop edge angle equally.

Again, this is a "check for understanding" before proceding. Please confirm or correct my observations to reflect what you intended.

BTW, I've stayed away from the "Percentage of body weight" dials because I find them a little confusing. At the start of the demo the left dial shows about 75-80% and the right roughly 45%. This creates a skier who weighs about 120% of their weight. Are the dials showing a perceived pressure taking into account forces developed during a turn?

Nevertheless very cool stuff.

post #4 of 9
Thread Starter 
Yeah, the skier is a bit heavy I gues, The sequence begins with the skier traveling so there is some force generated.

The ski sequence is correct. Attempting to duplicate what Bob was describing.

For a bit more dialog.

What do you think?
post #5 of 9
Good eye, Gary. I see the same thing. It's a tiny, quick, little sequential move--a little stem-step turn.

If that's what you're shooting for, Dr. G, I think you did a great job with this one. I like the independent action now of the two skis. And that subtle little move of the CM to the right with the step, before moving left as the turn progresses, is very accurate. The only thing that may not be quite right is that there would probably be a 100% weight transfer as the skis are matched. It may not last (the skier is likely to fall back to the inside ski, for a variety of reasons), but for at least a moment there would be no weight on the inside ski, typically, with this movement pattern.

Can't argue with SCSA on this one--if not a job, at least a hobby! I take it the skiing's not that great yet down there in Texas....

Best regards,
Bob Barnes
post #6 of 9
Gary--if I may--I think that, in general, Dr. Go's "percentage of body weight" dials are reasonably accurate. Because of the g-forces of turns, the pressure on the two skis combined would often add up to more than 100% of the skier's weight, especially in the latter half of a turn.

In the particular turn above, I'd expect to see a very brief but substantial increase in the pressure on the left (downhill) ski at first, as the skier pushes off from it. Then the weight would quickly come off that left ski as the skier transfers weight to the right ski and steps or slides the inside ski parallel to the outside ski.

Best regards,
Bob Barnes
post #7 of 9
<BLOCKQUOTE>quote:</font><HR>Originally posted by Dr.GO:

Tell me what we should improve...

Your participation in online forums maybe??
I just can't handle all the shouting.

<FONT COLOR="#800080" SIZE="1">[ December 02, 2001 11:18 PM: Message edited 1 time, by Roto ]</font>
post #8 of 9
<BLOCKQUOTE>quote:</font><HR>Originally posted by Dr.GO:
...Tell me what we should improve...

1) Make 'em go way slo, Dr. GO. Put more frames in to bring the speed down to about 1/2 or 1/3rd of the current value. This might be a problem for people with slow connections, but it would sure make it easier to see what is going on.

2) The PEOPLE that say they can't stand shouting mean THAT they don't like sentences that READ like this one -ie, the ransom note approach to typography.

Tom / PM
post #9 of 9
First of all thanks to BB for pointing out that the red dot represents movements of the CM. I probably should have figured that out but totally missed it.

Anyway, in my earlier post I described the “effects” I was seeing. Now onto some possible “causes.” Things get a little trickier without seeing the body parts attached to the skis.

With regard to the skis being edged unequally the question becomes – is the left ski over-edged, is the right ski under-edged, or is it a little of both?

If the right ski is under-edged it could suggest a lack of activity or discipline with the inside ski, but only on turns to the right since it does not appear on turns to the left. Since it is only occurring on one side, it could also be an equipment alignment issue on the right leg.

The “little of both” scenario points towards a knock-kneed stance. The skier may be over-flexing at the knees allowing this. Alternatively, he/she may be naturally knock-kneed and have equipment alignment issues with both legs.

Finally, the left ski being over-edged option. In this situation the left (outside) leg may be over-flexing allowing the knee to move towards the right calf. Another possibility here is that the left leg is appropriately flexed and aligned with respect to the right leg and the over-edging comes from an equipment alignment issue.

Again, these are just possible causes for the edge angle “irregularities” at the very beginning of the sequence. There may well be many others.

Perhaps the group would like to discuss this so far before proceeding.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Ski Instruction & Coaching