Board flex and fast powder turns

I gave some thought to why it's easier to turn quickly in powder on a
flexy board....

There are 3 components to turning on a snowboard: steering, edging and
pressure. In powder edging doesn't apply, so that leaves steering and
pressure.

In a wide open bowl you can make long drawn out turns just by steering –
pointing the board in the direction you want to go. You don't need to
use your knees to apply pressure – you can descend with you knees bent
at a fixed angle. But for quick turns you need to use pressure created
by active extension of the legs.

Two things need to happen to make a quick turn in powder:
1) The board needs to come to the surface
2) The momentum of the board and you needs to change direction

Flex helps with both of these. Imagine standing with your board flat on
hardpack and jumping. If you don't ollie, you get the board off the
ground by developing upward momentum in your upper body and using this
to pull up your legs and board. It's hard work! Ollieing uses the flex
of the tail as a spring. This helps generate upward momentum in your
upper body but also applies an impulse directly to the base of the board
to push it off the ground.

I think the same sort of thing is happening due to the flex of the board
in powder: leg extension is storing energy in the base of the board (due
to bending) which then helps to push the board (and you) both upwards
and towards the new direction of travel. You can feel the same thing
when carving where the spring helps to unweight the board for the edge
change.

Comments? Mike, Arvin, Phil, Neil, anybody?

Iain
Looking forward to hitting Kirkwood soon!

id wrote:

I think the same sort of thing is happening due to the flex of the board
in powder: leg extension is storing energy in the base of the board (due
to bending) which then helps to push the board (and you) both upwards
and towards the new direction of travel. You can feel the same thing
when carving where the spring helps to unweight the board for the edge
change.

I don't think it's anything that complex. Powder turns are basically
banking off the snow. When you flex the board, it makes a rounded shape
against the snow and that helps it come around. Long, curved noses are a
big factor, too - when you lay it over, the curve of the nose helps
bring it around. I think the nose is probably the most important part
of the equation, especially in really light powder where even noodly
boards aren't flexing much.

Stiff boards can't be flexed unless you can get an edge into something,
and they usually have shallower noses, so they tend to go straighter.
To get them around requires more muscle, more up and down like you do
with old skis.

My theory, anyways.

Neil

Neil Gendzwill wrote:

I don't think it's anything that complex. Powder turns are basically
banking off the snow. When you flex the board, it makes a rounded shape
against the snow and that helps it come around. Long, curved noses are a
big factor, too - when you lay it over, the curve of the nose helps
bring it around.

That sounds right. Nose flex should increase lift at the nose and help
turn the board. But I think for really fast turns, e.g. ducking through
the trees, then the spring of board is important - like a jump turn. The
mechanism you describe is analogous to the carve where the edge on the
snow determines the turn radius and you turn continuously and smoothly.
So I agree that the flex will help the smooth continuous turn; but I
think it's also critical for the very fast, discontinuous jump turn
equivalent.

I think the nose is probably the most important part
of the equation, especially in really light powder where even noodly
boards aren't flexing much.

The flex will be determined by the force the rider is applying to the
board. When going straight this will be the rider weight. When turning,
it's a combination of rider weight and G force. In light snow you'd need
to travel faster to get the same G force through the turn and hence the
same board flex

Stiff boards can't be flexed unless you can get an edge into something,
and they usually have shallower noses, so they tend to go straighter. To
get them around requires more muscle, more up and down like you do with
old skis.

So I think you're saying that a stiff board will turn very slowly unless
you use the up and down movement; a more flexible board will turn more
quickly without the need for up and down movement. I would add that
flexible board plus the up/down gives very fast turns.

My theory, anyways.

Thanks, Iain

(it must be that time of year..)
I think you're probably about right. Turning in powder is *not* all
about banking off the snow. Banked turns are possible in open glacier
terrain, and for those board flex is much less relevant. Even on open
glacier most experienced people don't turn that way most of the time.

I think I'm probably particularly fussy about board flex as I ride hard
boots & bindings. What flex I feel comes from the board.

In tight-radius turns on a glacier in knee-deep or better powder
there's a great deal of leg action. I don't think it's "up
unweighting", but there's a lot of down unweighting and the legs work.
Without a lot of experience you'll find most people need to stop a fair
bit - the reason is that a lot of work is being done. It takes more
effort for tighter radius turns. That work's being done on something,
and I reckon it's working against the board flex in the snow. It would
be interesting to examing the profile of a trail through the snow,
although you could just video a rider from the side..

In the trees.. flex matters more because you're generally doing tight
turns. That's all there is to it.

What I'm not sure about is how the board flex and camber work with the
tail flex, which is obviously related but slightly different. Add in
tail shape and you have something interesting to model.

Nose shape: I don't think that this is particularly important. I've
ridden a range of boards with radically different nose shapes in
bottomless and the only thing I'd say you need is a reasonable amount
of stiffness plus a decent size.


phil

I gave some thought to why it's easier to turn quickly in powder on a
flexy board....

Easier but definately not better. On a smooth powder surface with no
ruts a slightly shorter firm board is sportier. Compare it to driving
a Porsche vs. Cadillac.

My prefered ride for powder is a Volkl Anthrax 160 cm. with a 24.7 cm.
waiste.

og

On a smooth powder surface with no ruts [...]

I think we may be having trouble with terms here. The "surface" of the
powder is irrelevant 'coz you're in it, not on it.

I think we're talking about "bottomless" powder, not just fresh snow at
a resort, which is not all that different from pisted snow, assuming
you're turning with good style.

On Fri, 10 Dec 2004 13:45:30 GMT, id no@id allegedly wrote:

Two things need to happen to make a quick turn in powder:
1) The board needs to come to the surface
2) The momentum of the board and you needs to change direction

I won't pretend to know anything about fluid dynamics, but have you
considered factoring information in from surfing, or even windsurfing on a
short board.

The boards are small and sit under the water with the rider's weight.
When they get planing they come to the surface. Both types of boards have
high noses allowing for deep carves. And a surf board (not sure about a
windsurf board) has some flex in it although not that much.

As a windsurfer, you may be able to draw information from your
experiences.

- Dave.

--
The only powder to get high on, falls from the sky.
http://www.vpas.org/ - Snowboarding the worlds pow pow -
Securing your e-mail

The Snowboard FAQ lives here - http://rssFAQ.org/

Thanks, Phil!

In tight-radius turns on a glacier in knee-deep or better powder
there's a great deal of leg action. I don't think it's "up
unweighting", but there's a lot of down unweighting and the legs work.

I think the up and down unweighting become the same thing if you're
making turns in quick succession. Down unweighting comes from flexing
the legs - but you won't have ridden far with straight legs so the
extension will have been just before the flexing. So upwards momentum
will already have been generated prior to flexing.

Without a lot of experience you'll find most people need to stop a fair
bit - the reason is that a lot of work is being done. It takes more
effort for tighter radius turns. That work's being done on something,
and I reckon it's working against the board flex in the snow. It would
be interesting to examing the profile of a trail through the snow,
although you could just video a rider from the side..

Good point. You could tell a lot from the trail. Sadly I don't think I
have the mental strength to study a trail when there's virgin powder
close by...

Iain

Switters wrote:

I won't pretend to know anything about fluid dynamics, but have you
considered factoring information in from surfing, or even windsurfing on a
short board.

The boards are small and sit under the water with the rider's weight.
When they get planing they come to the surface. Both types of boards have
high noses allowing for deep carves. And a surf board (not sure about a
windsurf board) has some flex in it although not that much.

I think Phil's point is relevant he with powder you're generally in
it not on it. Surfboards and windsurfers have two sources of flotation:
displacement (like a boat) and planing. In your surfboard example the
flotation due to displacement is not enough to float the rider when
stationary - you need additional displacement flotation from the rider
himself being under water. Once you're moving you get additional
hydrodynamic lift (planing) and actually less displacement flotation as
most of the board comes out the water. I don't think the flex
contributes much to turning a surfboard

As a windsurfer, you may be able to draw information from your
experiences.

In a normal carve turn there's no unweighting - actually the weight on
the water will increase due to loss of lift from your sail.
Alternatively you can go for complete unweighting - jump gybe - where
you use the sail to get airborne. That makes for a quick turn but you
tend to end up stationary - board in the water, not planing. No chance
of linking jump gybes!

Iain

id wrote:
I don't think the flex contributes much to turning a surfboard

Do surfboards flex? They look like rigid structures to me, but I don't
surf.

Neil