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I was watching the videos at http://www.stud.ntnu.no/~hansho/ and in each of them, the body position they use while tracking with tracking pants is to have their legs very wide apart, and their arms about where they'd be if they were wearing a wingsuit (with palms up, it looks like).

It seems to me that this body position would spill a lot of air and thus be very ineffective, but in the videos they are tracking absolutely unbelievable distances.

Can someone explain the aerodynamics of this to me? Why not move your legs close enough together to create a consistent surface (but not too close together to inhibit inflation of the legs), and therefore create a bigger "wing"? (And similarly with bringing your arms into your body).

Anyone?

Hans is one of the guys you see in the movie, use elastic (rubber) bands from shoe to shoe innside the pants, and rubberbands from hiprings to the arms innside the jacket. this system makes more surface between your legs and under you arms, also gives you less drag from clothing. It is a little complicated system, and narrow your movements allitle.

And now to our Q!

Give Hans a mail, he is the expert on this area! (Making his degree on airflow)

there's a good section of C2 that shows tracking suit body positions quite well...

methinks I will try this on my next tracking skydive

Hey Kid...
I am certainly NOT an expert tracker, but I spent the summer at Kjerag watching the Track Masters do their thing. Jon Inga and Atle Dahl were absolutely amazing in their smoke pants, and they used a very wide-legged body position. Even Darcy and Hecy, who don't have the classic long/lean tracking friendly body type were tracking like mutha's in this position. Here are some parts of their explanations to me: the wide legs give you a much more stable position, keeping you from rolling side to side at all, which adds to your ability to drive forward. The wide V of your legs actually gives you a wider area to push on, and the area between your legs gets nearly to be a burble zone. I watched these guys track from Kjerag TO OVER THE LANDING AREA in just smoke pants! (Jon Inga and Atle). The proof is in the delay, boys... :) It's all about practicing, finding the sweet spot that works with your body shape, then just going for it. I'm still learning, and look forward to making some huge strides next season.
Come to Kjerag! The guys are always happy to talk to guys and give them tips.

I miss you all over there....(sniff sniff)
Karen

are there any pics of this?
maybe a diagram would be cool.

when your legs are that wide while tracking, do you point your toes inwards?
when the palms are turned upwards, do you have to bend your arms slightly to bring your forearm paralell to your body?
and of course, hehehe... is there a similar body position for back tracking? would be awesome to use it being a rabbit on a tracking dive ;).

Hi,
i found myself elaborating on the subject in the answer to kidwicked's e-mail, so why not post it, now that i discovered this thread...

here goes:

"hi kidwicked,

first - i don't mind at all. for the sport to evolve it's essential to
share experiences and knowledge.

this technique (the wide body position) has been the common one amongst
experienced trackers here in norway. it seems to be very effective, way
more effective than the old "skydiving track" with arms an legs tight
together (skijumping has evolved in the same direction). but there are
also other factors than the wide position involved.

to give you a good explanation, i have to start with the basic
aerodynamics. the glide ratio of any freefalling body is given by the
lift-to-drag ratio as these are the only forces working, apart from
gravity itself. so what we are trying to do, is to maximize this ratio.
either by increasing the lift or reducing the drag.

increasing lift can be done by exposing a larger surface to the free
airstream (hence the wide position), but in many cases this also
increases the drag. to avoid this drag, we try to stiffen the surface
(the fabric in our clothing) by tightening pants and arms.

this season i have been attaching my pants to my shoes, both toe and
heel. real tight, so that an upright position is almost impossible. in
addition, i track with my feet outwards, to utilize the extra
"bootie-surface" between toe and knee. the spread legs puts this extra
surface out in the free airstream.
for the arms i've been using a cord from thumb to thumb (witch gives
palms up...), through the arms in the jacket. this is very effective, as
it stretches and stiffens the fabric and also gives it an airfoil
shape. the wingsuit-like arm position is very natural with this setup.
think of your body, not as one wing, but many separate wings, and try to
make them all effective. a tight "one-wing" position doesn't really give
you any wing at all, just a very irregular surface.

in addition to this, angle of attach is also a very essential element.
to fly this setup well, you should try to go steep. as you can see
from the videos, exit is almost head-down. as you gain forward
momentum, you stay at the same angle of attack relative to the air.
flying like this, it's very tempting to stall, because that gives you a
feeling of incredible lift. (i have done this too many times..) it's an
illusion! it will slow your speed and eventually you will loose
altitude, like flaring your track. try to maintain a high speed
throughout the jump. the faster the better, as lift is generated
proportional to the square of the speed.

but it's all in your balance, when it comes to angle of attack.
therefore, try to balance your clothing aswell(pants-jacket).

i hope this gives you some ideas to work with. looking forward to seeing
you from our bigwalls some day.

Han-Solo"

Thanks for that Han, a lot of useful info in that post.

Intresting post Hans.

What do you think about the Atmonauti angle for tracking, i start using it for base and it's a bomb !

 
To begin with, I must say a very good post there Hans on a very intersting issue indeed ! I've been thinking about tracking and aerodynamics of it and the more I think about it the more fascinating it is, basically so simple thing and still so multidimensional issue.


That is absolutely true that we must try to maximize this ratio but if you widen your body position (and present more surface to airstream) you simultaneously present more surface to relative wind, thus creating more drag ? Think about the cross section of the "wing" you are creating when you are tracking, more "closed" your position is the smaller the cross section of the wing is and the smaller the drag is it creates while moving throurgh the airstream. So with the wider position you should be able to create more lift to overcome the additional drag it creates. This all comes down to maximizing the ratio between lift and drag but in my books widening the position means more drag so if going for wider position I should get huge amounts of lift out of it to get better performance from it than narrower position.


Could you post pictures about your setup ? I'd be more than interested to see them.


That is very important point indeed, as we advance in tracking and get better and better performance in tracking we move closer to wingsuit flight. I feel that angle of attck pays a crucial role in winged flight, it is way too easy to fly your suit very near the stall point (or actually stall your suit) and get the feeling of an amazing lift. Way too many wingsuit fliers fly their suits colse to the stall point and get relatively good freefall times 'cause that position with modern suits is quite floaty. But what they simultaneously are doing is killing the forward speed. If they would only push little harder and fly with more agrressive angle of attack they would get amazing forward speed and create the lift through speed, not through additional drag. I think that the same applies for modern tracking and is easyly overlooked when thinking about improving ones tracking skills.

thanks Han, I went out and tried it and hit sub-90mph vertical fall rate on the first try [that's more than a 10% improvement from what I usually get]. I could also feel the difference between just creating lift and actually maintaining the speed while getting the lift. I found it pretty hard to fly straight though... guess I have to work on the symmetry of my feet some more.
anyway, very very cool.... thanks a bunch :)