Reduction of Friction on Artificial
Ski Surfaces:
Athlete Surface Interactions
Professor Peter Styring
EPSRC Senior Media Fellow
Chemical & Process Engineering
The University of Sheffield
STARRS, Loughborough, 18 September 2007
Ski Surfaces
•
•
•
•
•
•
Alpine Snow
Artificial Snow (Alpine & Snow Hall)
Dendix
SnowFlex
PermaSnow
Other polymers
Dendix
SnowFlex
Waxing the Bases
• Without a wax there is high friction between the
ski base and the plastic (less so on alpine snow,
but still a factor).
• What about artificial snow?
• The wax is usually applied using a hot iron to get
the wax into the porous base.
• Excess wax is scraped off and the base then
polished with a fine horsehair brush.
• This process requires a workshop and toolkit to
carry it out effectively.
• It is a very time consuming process that requires
experience for it to be done well consistently.
What Happens to the Wax as
we Ski on an Artificial Slope?
• Friction and abrasion on the base of the ski
causes the wax to be lost.
• Performance decreases as we ski due to these
losses.
• On a plastic slope waxes are lost quickly.
• Artificial snow is more abrasive than alpine
snow.
• Plastic slope and snow slope skiing are really
two different sports.
• What we need is a way to constantly replace any
lost wax as a thin, renewable layer
A Continuous Waxing System
Flowrate of lubricant Q
Q
U
W
h
Drag Force ~ Area x shear force
L
~ W L μ U/h
Lubricant
Q ~
Viscosity
(User Control)
Fdrag
Ski Contact Area
(Discipline Dependent)
hWU
Fdrag ∝
ηA
Q
Lubricant
Flowrate
(User Control)
How Does it Work?
• Skiers apply pressure to the skis
• Reverse camber causes the Wildfire rise plate to
bend which forces fluid through a pipe to the ski
base
• The more pressure that is applied, the greater
the flow
• No external energy source is used, just the skier
(FIS Equipment Rules Compliant)
• The lubricants are environmentally friendly and
biodegradable
• The continuous flow, continually reduces friction
How Can We Confirm it Works?
• Glide tests are carried out to measure the time taken
between two points to simulate a Downhill track (DH). We
can also look at Giant Slaloms (GS) and Super-Gs.
• The skier must adopt a tuck position to minimise wind
resistance.
• Consistency is essential for the results to be statistically
acceptable
• Controls are run at regular intervals (Fair Testing)
• Mountain tests would be ideal but for initial studies we can
use UK artificial facilities at Sheffield Ski Village and
SNO!zone Castleford
Data from
Bob Kirk
Abrasion and Flow
4.8
No Fluid Flow
4.7
Fluid Flow On
4.6
4.5
Time (s)
4.4
4.3
Hot Wax
Continuous Wax
4.2
4.1
4
3.9
3.8
0
100
200
300
400
Distance (m)
500
600
700
Weight & Balance
Artificial Snow Moguls
‘How Science Works’
‘How Science Works’
Engineering
Gold!
TeachersTV
17 October 2007
Relative Performance of the
Wildfire System in Different Tests
Test
GS
DH
DH
DH
DH
Surface
Dendix
Dendix
Snowflex
Artificial
Snow
Alpine
Snow
% Speed
increase
23
32
48
8
1-2
Data taken from Snowsport England Validation Tests
Wildfire on Artificial Snow
WF50W
Comments
Averages
%improve
4.80
0.0
4.55
5.3
4.58
4.6
Tank drained
4.57
4.61
4.57
Run History
5.10
5.00
4.90
Time (s)
Run
1
2
3
4
5
6
7
8
Time (s)
Race wax
PP3
4.64
4.82
4.95
4.55
4.69
Race Wax
4.80
PP3
4.70
WF50W
4.60
4.50
4.40
0
1
2
3
4
5
6
Run Number
7
8
9
Athlete Perception
• Phil Smith at SSV: “It feels like I’m skiing on
snow!”
• Holly Cutler at SSV: “Much faster and smoother”
• Graham Bell (Laterns, Austria): “There was no
loss of edge control”
• Becky Hammond at SSV: “I got much higher out
of the pipe!”
• Phil Smith at SSV: “I can feel when the system is
switched off. Without it the drag is greater and
bits of the slope start to melt on to my skis!”
Wear on SnowFlex
Summary
• Controlled blind tests have been validated by
Snowsport England.
• Results show enhanced performance on all
surfaces while adhering to FIS Equipment
Regulations.
• In addition to performance enhancement there is
added base and slope materials protection.
• We are looking to using the technology in the
FIS World Cup but our prime objective is at the
2010 Winter Olympics in Vancouver.
Special Thanks
• Dr Alex Routh (Cambridge)
• Graham Bell, Hannah Handford-Styring, Becky
Hammond, Phil Smith, Jon Smith, Holly Cutler
• Bob Kirk (MechE)
• Head Skis GmbH & Atomic Skis GmbH
• Glasshead Ltd
• The Polymer Centre
• Sheffield University Enterprises Limited