# Ski jump: how much does aerodynamics matter? **URL:** \ **Category:** Factual Questions\ **Created:** [February 20, 2014, 5:56pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807 "2014-02-20T17:56:14Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [February 20, 2014, 5:56pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/1 "2014-02-20T17:56:14Z")
Watching the Olympic ski jump event, I started to wonder: how much does aerodynamics matter for these guys? If I took a skier’s speed and trajectory just after leaving the ramp and calculated a parabola based on 1 g of downward acceleration due to gravity, where would that parabola intersect the hillside relative to their typical landing zone? ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 20, 2014, 7:21pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/2 "2014-02-20T19:21:13Z")
Aerodynamics matter a lot. The introduction of the V-style significantly increased lenghts, wikipedia says 10% ([V-style](http://en.wikipedia.org/wiki/V-style)). ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [February 20, 2014, 7:27pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/3 "2014-02-20T19:27:48Z")
But it’s an interesting question whether ski jumpers go further because of the air, compared with the same jump in a vacuum. I suspect they do, but that’s just a WAG. ---
**Author:** ![Poysyn](https://avatars.discourse-cdn.com/v4/letter/p/f4b2a3/32.png) [@Poysyn](https://boards.straightdope.com/u/Poysyn)\ **Post date:** [February 20, 2014, 7:44pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/4 "2014-02-20T19:44:51Z")
Speaking of Ski Jump…does anyone else find it a little eerie when they are in parachute? It just looks like they are hovering there… ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [February 20, 2014, 8:09pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/5 "2014-02-20T20:09:24Z")
> [@ZenBeam](#): > > But it’s an interesting question whether ski jumpers go further because of the air, compared with the same jump in a vacuum. I suspect they do, but that’s just a WAG. I speculate they’d go farther in a vacuum. Granted, they get a lot of lift by assuming an airfoil shape, so they fly higher and therefore farther than they would otherwise. But I’d bet dollars to donuts that the overall effect of resistance outweighs the additional distance due to lift. If we had sufficient data, it would be fairly easy to calculate the vacuum trajectory and answer this question analytically (given actual data for the ski jumpers, which would be very hard to model accurately.) ---
**Author:** ![ethelbert](https://avatars.discourse-cdn.com/v4/letter/e/958977/32.png) [@ethelbert](https://boards.straightdope.com/u/ethelbert)\ **Post date:** [February 20, 2014, 10:44pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/6 "2014-02-20T22:44:36Z")
The clothing that ski jumpers wear is pretty strictly regulated to prevent them from wearing baggy suits that would carry them further. ---
**Author:** ![j\_sum1](https://avatars.discourse-cdn.com/v4/letter/j/8baadc/32.png) [@j\_sum1](https://boards.straightdope.com/u/j_sum1)\ **Post date:** [February 21, 2014, 6:21am UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/7 "2014-02-21T06:21:11Z")
> [@Learjeff](#): > > I speculate they’d go farther in a vacuum. I would speculate the opposite. Those skis are broad and long and I would suspect generate a lot of lift. I would love to see a calculation and comparison. ---
**Author:** ![polar\_bear](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@polar\_bear](https://boards.straightdope.com/u/polar_bear)\ **Post date:** [February 21, 2014, 6:52am UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/8 "2014-02-21T06:52:37Z")
Note also a head wind leads to bigger jumps. Nowadays you even get a points deduction if you have a head wind and extra points if you have the wind in the back. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [February 21, 2014, 12:51pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/9 "2014-02-21T12:51:26Z")
> [@polar\_bear](#): > > Note also a head wind leads to bigger jumps. Nowadays you even get a points deduction if you have a head wind and extra points if you have the wind in the back. That would seem to settle it pretty conclusively. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [February 21, 2014, 2:58pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/10 "2014-02-21T14:58:52Z")
> [@polar\_bear](#): > > Note also a head wind leads to bigger jumps. Nowadays you even get a points deduction if you have a head wind and extra points if you have the wind in the back. Yeah, that started back in 2009. One interesting point I could find about it is that while the formula is linear and the points deduction of a headwind is equal to the points addition on a tailwind of equal speed, in computer simulation at least, it doesn’t work out that way, with a tailwind actually hurting the distance much more than the headwind helps. [Here’s an article](http://fuckyeahfluiddynamics.tumblr.com/post/76636822248/yesterday-we-talked-about-the-technique-ski) that cites a study finding a 3 m/s headwind adds 17.4 meters to a jump, but the same velocity tailwind deducts 29.1m from the jump. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 21, 2014, 3:20pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/11 "2014-02-21T15:20:39Z")
It could still be the case that a ballistic trajectory in a vacuum exceeds either (especially if the whole jump including the slide down the ramp is in vacuum). We’ll know for sure at the Vacuum Olympics in 2034. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [February 21, 2014, 10:53pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/12 "2014-02-21T22:53:54Z")
Here’s a [research paper](https://cds.cern.ch/record/1009275/files/p269.pdf) (note: PDF) on the aerodynamics of jumping - well worth the read if you want to geek out. It starts simple… > [@](#): > > Owing to the non-linearity of the equations, a variation of the geometrical and fluid mechanical parameters can result in bifurcations and the non-linear fluid system can display deterministic chaos. …and then gets a bit more complex. Regarding the benefit/disadvantage of a headwind or vacuum, look at Figure 7 near the end of the paper. This shows that somewhere around 15 meters from the take-off (at which point the jumper has probably assumed the ideal alignment), the lift force is greater than the drag force. These forces aren’t in the same direction so you can’t simply cancel them out, but maybe someone with more time and skills than I could determine what this means when you factor in landing angle and all that good stuff. Figure 8 on the last page shows differences in distance and velocity with a headwind. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [February 22, 2014, 12:52pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/13 "2014-02-22T12:52:43Z")
If the data is available for launch angle, velocity at launch and height between launch point and the landing area, it’s pretty straightforward to calculate distance travelled in a vacuum. Then just compare it to the actual distance traveled by the jumper. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [February 22, 2014, 5:38pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/14 "2014-02-22T17:38:27Z")
> [@polar\_bear](#): > > Note also a head wind leads to bigger jumps. Nowadays you even get a points deduction if you have a head wind and extra points if you have the wind in the back. A little googling corroborates your claim, so I stand corrected. I find this argument sufficient to resolve the question. Ignorance fought, thanks! ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [February 22, 2014, 5:58pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/15 "2014-02-22T17:58:05Z")
The L/D \> 1 data point tells us that the jumper will be able to sustain a 45 degree or flatter glide until he (or she!) re configures for landing. The parabolic path taken by a jumper in vacua will cross below this at some modest height, so on tall jumps the vacuum would hurt. That of course assumes equal launch speeds. The lack of drag on the approach would lead to higher launch speed, assuming the problem of the snow and ice sublimating could be solved. Actually I would not be surprised if the friction at the ski-snow interface was much higher without air in the mix. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [February 22, 2014, 6:02pm UTC](https://boards.straightdope.com/t/ski-jump-how-much-does-aerodynamics-matter/681807/16 "2014-02-22T18:02:27Z")
Another factor with wind is that it will be closer to tangent to the landing slope than hirizontal, so the jumper with a headwind is actually jumping into an updraft. This is well known and exploited by glider pilots. Known as slope soaring, it is far more reliable and easier (but more dangerous) to learn than using thermals.