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Arc?

post #1 of 17
Thread Starter 

PSIA-NW Alpine Certificationn Guide, 2011, pg 45, “Rotary Control Movements”:

 

“Long radius turns should be performed on groomed blue to black terrain with a very narrow arc.”

“Perform an uphill Christie on steep terrain with a narrow arc……”

 

What is an arc?  How does it get wider / narrower?

 

 

post #2 of 17
The arc is the curved line the skis make during a turn on the edges.

I think the "narrow" description applies to the distance between the skis.
post #3 of 17

molesaver   

 

That refers to the marks left in the snow by the skis, more carved than skidded.  It has little to do with the width of the feet apart.

 

RW

post #4 of 17
What Ron White said ^^^.

They're looking for a turn closer to a Dynamic Parallel Turn than a widely drifting/brushing Open Parallel turn. No need for a highly refined carve nor anything so dramatic - just using the bent ski to create the majority of turning rather than friction and/or pivoting (and certainly no heel-pushing to drive the tail out).

.ma
post #5 of 17

Could be we need to see the complete description instead of snippets. Can you post those Mole?

post #6 of 17
Thread Starter 

I, too, need to see a complete description.  The "Certification Guide" is 101 pages.  This is the only one where "arc" is used (I really wish PSIA would turn over the generation of its educational texts to Bob Barnes).  Here is pg 45 in its entirety:

 

Edge

Control

Movements

These

tasks

and

drills

are

designed

to

help

the

Level

III

instructor

change

the

edges

from

uphill

to

flat

to

slightly

downhill

during

the

turn

transition

before

turning

the

skis

toward

the

fall--‐line

in

most

conditions

and

terrain

the

mountain

presents.

Traverse

on

either

uphill

or

downhill

ski

with

it

tracking,

alternate

with

it

sliding

diagonally

down

the

hill

to

another

track

Perform

both

target

and

side--‐cut

traverses

In

a

wedge

position

moving

slowly

down

the

fall

line

of

a

moderate

to

beginning

slope

gently

hop

from

ski

to

ski

on

the

inside

edge

without

the

skis

sliding

sideways

Perform

hop

turns

on

moderate

terrain

--‐

outside

ski

to

outside

ski

and

both

skis

to

both

skis

Pressure

Control

Movements

These

tasks

and

drills

are

designed

to

help

the

Level

III

instructor

perform

round

medium

and

short

radius

turns

with

the

skis

in

contact

with

the

snow

and

gradually

increase

pressure

on

the

outside

ski

throughout

the

turn

on

most

terrain

and

most

conditions

that

the

mountain

offers.

Be

able

to

time

a

takeoff

from

one

small

round

bump

and

land

on

the

reverse

side

of

a

nearby

bump

Perform

round

medium

radius

turns

in

the

bumps

Railroad

track

turns

--‐

ski

medium

radius

round

turns

with

a

narrow

arc

in

the

snow,

skis

in

contact

with

the

snow

at

all

times,

with

the

hips

staying

roughly

the

same

distance

off

the

snow

Rotary

Control

Movements

These

tasks

and

drills

are

designed

to

help

the

Level

III

instructor

perform

medium

and

short

radius

turns

in

most

conditions

and

terrain

that

the

mountain

presents,

with

a

narrow

track

in

the

snow

throughout

the

turn.

Long

radius

turns

should

be

performed

on

groomed

blue

to

black

terrain

with

a

very

narrow

arc.

Maintain

ski/snow

contact

in

the

deep,

heavy

snow

throughout

medium

and

short

radius

turns

Round

short

radius

and

medium

radius

turns

in

blue

to

black

bumps

Perform

an

uphill

christie

on

steep

terrain

with

a

narrow

arc

in

the

snow

where

the

turn

is

not

started

by

a

pivot

to

an

edge

Perform

a

series

of

linked

pivot/hockey

slips

on

steeper

terrain

maintaining

speed

control

staying

on

the

fall--‐line

post #7 of 17

The "arc" is following the design radius of the ski. Slalom ski = small arc, 120 underfoot Alaskan slope blaster = big arc. In a long radius turn there should be little to no rotational movement. We're looking that you can tip the skis on edge and move with them throughout the turn. In the East we can it a railroad track turn.

post #8 of 17
Thread Starter 

That makes sense to me.  Is the stipulation of "narrow arc" superfluous then?

post #9 of 17
Quote:
Originally Posted by molesaver View Post

That makes sense to me.  Is the stipulation of "narrow arc" superfluous then?



I guess you could think so. I believe what they are trying to get across is that they don't want to see more bend in the ski then just standing on it and guiding it gives. This would be vs. a performance short radius turn where you really need to "arc" the ski to perform the task. Does that make sense?

post #10 of 17
Thread Starter 

Tracked down the Author!  Yeah!

 

Here's what he had to say:

 

Good question.  Intent vs content.  You will note that these descriptions are taken from exercises to help develop better skill awareness and skill blend & not from the task lists for any of the 3 certification levels. 

 

When the goal is to achieve a turn maintaining a parallel relationship while not starting the turn with a pivot of any kind, you leave a slender or narrow track in the snow that is best described as an arc.  By definition, an arc is any part of a curve, especially of a circle.

 

As shaped skis replaced what we once referred to as contemporary skis, especially from a racing perspective, more turns were achieved leaving single tracks in the snow & referenced as arcing versus carving.  The coaches association embraced the use of the shaped skis thereby adding a higher level of ski use i.e. arcing.  Now, arcing is the upper end of carving.  In the ATM, we define ski use as sliding, slipping, skidding, carving & as is stated " For the most part, carving is the absence of skidding but recognize that some skidding is present in all turns."  The upper end carving leaves a narrow track {arc} in the snow.

 

Bottom line - I appreciate that you are studying the guide so carefully.  I also appreciate that you have brought this to my attention.  When written it made prefect sense to me but now that I see it can be interpreted, I need to edit to ensure that everyone fully understands that narrow is in reference to the track left in the snow and that the long radius turns or uphill christies are completed correctly by using the design of the ski not started with a pivot. 

 

Pragmatically, most of the turns made while skiing at our level we refer to as carved turns but the tail cannot follow the tip thru the turn due to varying, terrain/conditions/need turn shape but they are still quality turns. 

post #11 of 17

I gather from this that:

pencil thin line in the snow = narrow arc

one of these is wanted for each ski

post #12 of 17

Reading that does definitely shine a light on things, but I believe we were on the right track and that just confirmed it.

post #13 of 17
Thread Starter 

Yes, I think you guys nailed it from a couple of different directions.  Still it helps to know exactly what the author had in mind, especially when they are instructions on how to be successful in an exam!  The dictionary def. of 'arc': "any segment of a curve, especially a circle" had me thinking that a 'narrow arc' had to be one whose tangent and secant were close together and a wide arc was one whose tangent and secant were far apart.  That ought to teach me to NOT get the dictionary out.

post #14 of 17

Real Skiers can't even read dictionaries. You should know that by now molesaver. We love to make up words. Take my favorite (Sail with a sigh) that seems to be rampant in the east, foragonially. I don't even know if I can spell it right let along define it.

Tip 'em and Rip 'em.

post #15 of 17

It would seem "arc" will always have slightly different interpretations and therefore in an exam situation, be sure to clarify with examiner so you are both on the same page!

 

Some view "arc" as the purest form of carving while others take a more liberal view and exchange it freely with the traditional definition for carving or perhaps simply being closer to the carving end of the "pivot vs. carve" spectrum.

 

I personally do not get to hung up on it and in an exam or clinic I try to define clearly what I want to see so there is no confusion.  If I see poor results, I check for understanding, reiterate the goal, and try again.

post #16 of 17

yup yup, what Bud said. Imagine going to a test and pulling out the author's note just to find the examiner that day means something different. Best to ask them up front what they want to see if you have any questions. And you should alway ask instead of assume you know what they mean.

post #17 of 17

After passing L3 in 2 disciplines I think my rule of thumb works well.

 

Read, but don't worry about what the guide says, or even what the examiner says. Just do what is demoed and you'll be fine.

 

Most examiners have their own slight variation in understanding of explanations. You'll be better served showing adaptability to their interpretation then in trying to show what you think is the right way.

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