The111 1 #1 September 9, 2003 I hear all the time that people learning HD are "all over the sky". How does the efficiency of forward motion in HD compare to a belly track? Can you cover the same distance in a jump? More? Less? Obviously, if you're falling 1.3 times faster (for example), you'd have to move faster laterally by the same factor to cover the same distance. Just curious...www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
Vertifly 0 #2 September 9, 2003 This is actually a very interesting question. I couldn't possibly speculate on which one is more "efficient". In this case, it is like comparing apples to oranges. The reaction of the air is very different when you compare the two different speeds. In a back-track, some freeflyers can take it down as low as 100mph and cover a # of miles during one skydive. At the same time, in the head-down position, your acceleration is faster because of the speed of the relative wind. I would argue that a freeflyer moving forward could pick up a lot of speed also. Not really sure what the ratio would be in comparison, but the acceleration factor will definitely max it out if moving forward in a HD then immediately going to a back-track. Remember the difference in wind resistance from 100mph to 200mph isn't doubled, it's squared. In other words: If wind resistance at 100mph is 5lbs, then, wind resistance at 200mph is NOT 10lbs, it's actually 5² or 25lbs. This is why freeflying allow's for such versatility. And given the "versatility" of the sport, I would argue that (in one skydive) you could cover much more ground (or AIR in this case). LOL =8^) Quote Share this post Link to post Share on other sites
The111 1 #3 September 9, 2003 Hehe, I actually have a BS in Aerospace Engineering so I have a little bit of an idea about what you're talking about. :) And I hate to nitpick, but... as far as wind resistance (a force) is concerned, in a stable (terminal) position, it will be the same whether you're going 100 or 300mph. And it will equal your weight, regardless of your body position or speed. To go to a non-static body position, you could induce an inequilibrium of forces which would generate accleration in any direction. The reason for higher lateral accelerations in FF, from an aerodynamic standpoint (or even just physics), it not due to the higher speed, but due to simple geometry. Go drive your car at 60 mph. Hold your hand out the window, palm perpendicular to the airflow. Small changes of the angle of your hand will not result in huge instabilities. But move your palm so it is parallel to the wind (like a wing, or a FF body position), and it will generate huge accelerations for small angular changes. Notice the car is moving at the same speed the whole time. I haven't found my HD yet, but I have a halfway decent sit going and I know what you mean about the massive accelerations you can create by swapping from a foward slide to the opposite... and I'm sure those accelerations are even stronger in HD! EDIT: God, I'm a dork. When I start thinking about stuff like this I can't stop... partially I'm trying to explain better and partially I'm trying to understand better, I'm still figuring it out. You are right in that normally (i.e. considering airplanes) drag is related to the square of velocity. But planes keeps the same area presented to the wind at all times and vary their velocity by propulsion. As freefallers, we can only vary our velocity by changing our area, and our propulsion is always the same (our weight!). /still thinking...www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
Vertifly 0 #4 September 9, 2003 If a person goes from flat to a 45-degree angle, that is from ___ to \ the acceleration on the horizontal plane to terminal velocity, this would not be as quick as the transition from this | to \. This is what I meant by the speed of movement in the sky from head down to a track. It isn't the terminal velocity that changes, it is the amount of time (speed) at which terminal velocity is acquired. Therefore, initially, head down allows for a quicker acceleration rate on the horizontal plane. This is all that I meant. Quote Share this post Link to post Share on other sites
The111 1 #5 September 10, 2003 Like my car window example. :)www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
lazyfrog 0 #6 September 10, 2003 your body position can make you move real fast... If HD are all over the sky is because these HDers do not have a stable position and good body control... the move is faster than in RW, and the collisions too ---------- Fumer tue, péter pue ------------- ourson #10, Mosquito Uno, CBT 579 Quote Share this post Link to post Share on other sites
78RATS 0 #7 September 10, 2003 Quote I hear all the time that people learning HD are "all over the sky". The real issue presented by "people learning headdown" is that the are all over the sky unintentionally. Nothing wrong with that as long as you are aware of it. The person learning headdown should change headings occasionally to keep from moving in one direction the whole skydive. As far as other people on the load, I have heard Heath Richardson say to treat them like a ten way for exit seperation purposes. Rat for Life - Fly till I die When them stupid ass bitches ask why Quote Share this post Link to post Share on other sites
