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Aerodynamics of Ski Jumping
Our weather specialist, Len Randolph, explains the aerodynamics of Nordic jumping and how man can indeed fly.
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(Jan. 26, 2002)------Alan Johnson/Ski Jump Manager, SLOC: "IF EVERYTHING IS JUST RIGHT AND YOU DON'T MOVE A MUSCLE, YOU GO FAR, YOU GET A GREAT LANDING, YOU GET GREAT STYLE POINTS."
But for everything to BE just right, one must first understand how things have evolved.
Len Randolph, Weather Specialist: "What's been the biggest change in form and technique?"
"BIGGEST CHANGE WAS PROBABLY AROUND 1988. THERE WAS A SWEDISH JUMPER, YAN BUCKLOV, AND HE HAD A TECHNIQUE UNIQUE TO HIMSELF. WHEN HE JUMPED HE WAS UNABLE TO KEEP HIS SKIS IN A TRADITIONAL CLASSIC FORM RIGHT UNDERNEATH YOU."
Bucklov lost style points, but FLEW much further.
LAN: "AND HE ACTUALLY ENDED UP WINNING THE OVERALL WORLD CUP FOR I THINK TWO YEARS IN A ROW. AND IF YOU LOOKED AT HIS TECHNIQUE, IT WASN'T THAT GREAT. SO WHY WAS HE GOING SO MUCH FURTHER? SO HE MUST HAVE BEEN DOING SOMETHING."
ALAN: "AND SUBSEQUENT STUDY, WIND TUNNEL STUDIES AND PROJECTS REVEALED THAT WHERE THE OLD TRADITIONAL STYLE WHERE THE SKIER HAD LIKE 1.1 TO 1 LIFTOVER DRAG, BASICALLY NOT ALL THAT GREAT. WITH A V TECHNIQUE WITH THE SKIS SPREAD, CREATING A BIGGER SURFACE AREA."
...In essence, a bigger "wing."
ALAN: "I THINK IN THEORY YOU CAN GET UP TO 1.5 OR 1.6 OVER 1 LIFTOVER DRAG JUST WITH THAT CHANGE IN POSITION. Huge increase. ALMOST MADE EVERY HILL IN THE WORLD OBSOLETE."
Even if hills got bigger, basic flight theory has remained the same.
ALAN: "IF THERE ARE VARIATIONS IN THE WIND , IF YOU GO INTO A HEADWIND AND YOU HIT POCKETS OF TURBULNECE WHERE THERES ALL OF A SUDDEN A TAILWIND, OR SIDEWIND, YOU'LL SEE JUMPERS MAKING ALL KINDS OF CORRECTIONS AND IT'S NOT A WHOLE LOT OF FUN. AND IT GENERALLY WILL AFFECT THE DISTANCE GREATLY."
The idea is NOT to steer, but if they have to, jumpers use their hands.
ALAN: "YOU CAN PUT ONE HAND OUT ALMOST LIKE A FLAP TO CORRECT YOU OR STEER YOU OVER THIS WAY."
The skis also help one's flight.
Len: "Okay alan go over the diff between a recreational ski and a jump ski"
"WELL ASIDE FROM THE OBVIOUS, THIS IS A SKI FOR BIG GUY LIKE YOU AND THIS WOULD BE A SKI FOR A LITTLE GUY LIKE ME FOR JUMPING. THE OVERALL WEIGHT BETWEEN THESE TWO IS THIS IS A LITTLE HEAVIER. Wow. AND YOU CAN FEEL THE DIFFERENCE."
"That is amazing, This is substantially lighter."
The weight of the ski is apparent when force is applied.
ALAN: "WHEN THE SKIER IS IN THE AIR, YOU'LL SEE THE AIR BLOW THE SKI BACK. IT'LL FLEX 3 OR 4 OR 5 INCHES BACK JUST FROM WIND PRESSURE."
Put it all together-- form, weather and equipment, and you're ready to experience flight.
Len: "Whats that air pressure feel like?
WELL, WHEN YOU COME OFF, IT KIND OF BUILDS AS YOU GO. YOU FEEL THE AIR PRESSURE MORE AND MORE THE FARTHER YOU GET DOWN THE HILL. AND YOU CAN FEEL IT ON THE SKI JUST KIND OF PUSHING AGAINST YOU AND ON YOUR WHOLE BODY AND DEPENDING ON WHAT THE WIND IS DOING, YOU CAN FEEL IT EVEN MORE. AND IF THE WIND IS COMING UP THE HILL IT ALMOST LIFTS YOU UP, AND IT'S A GREAT FEELING."
Now THAT must be some feeling to have the wind pressure keeping you flying down those hills. And here's something interesting-- the landing is marked where the athletes' FEET touch down, not where the skis first hit the landing ramp.
Alan told us that he has seen jumpers drag their tails for some 40 meters before their feet finally hit.
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