horizontal speed on tracking

[Eule 0]

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I did a tracking race once when we got out 4 miles(so the pilot said, pre GSP days) from the DZ at 8,000 or and I had just passed the DZ at opening hight of 2500.

D'oh! Kallend caught me getting it backwards. I will plead not enough caffeine yet this morning.

You went 4 * 5280 = 21120 feet horizontally, and 8000 - 2500 = 5500 feet vertically. That would make your glide ratio about 21120 / 5500, or about 3.8:1. In other words, for every foot you fell vertically, you went a bit under 4 feet horizontally. This does assume that the glide ratio was the same for the whole dive - in other words you were tracking immediately out of the door and pulled in a track.

Given that the top trackers are said to be in the region of 1:1 and improving towards 1.5:1, I think one or more of your numbers is a little off. Either that or you should go win some tracking competitions. :)

Like jakee said, there has to be a time to get a speed.

Eule

(Edited to fix backwardness)

PLF does not stand for Please Land on Face.

[kallend 2,106]

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I did a tracking race once when we got out 4 miles(so the pilot said, pre GSP days) from the DZ at 8,000 or and I had just passed the DZ at opening hight of 2500.

You went 4 * 5280 = 21120 feet horizontally, and 8000 - 2500 = 5500 feet vertically. That would make your glide ratio about 5500 / 21120, or about 0.26:1, or equivalently 1:3.8 . In other words, for every one foot you went horizontally, you went a bit under 4 feet vertically. This does assume that the glide ratio was the same for the whole dive - in other words you were tracking immediately out of the door and pulled in a track.

Like jakee said, there has to be a time to get a speed.

Eule

I think you got that backwards.

...

The only sure way to survive a canopy collision is not to have one.

[pchapman 279]

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I'd probably believe wind tunnel data from a well-funded wind tunnel study of ski jumpers,

First, as for Trackingderby results, I tend to be a little skeptical as one normally has no clue how much tailwind people were working with.

As for tunnel studies, I've seen an aerodynamics text reporting data from wind tunnel tests from the 1950s and 60s in the USA. Even back then the L/D curves were showing peaks of about 0.7 to 0.75. Pretty good.

[PWScottIV 0]

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I've heard it's possible to get a 1:1 ratio with a good flat track...so if that's true...120mph

Wouldn't a theoretical ratio of 1:1 mean you would actually achieve 60 mph horizontal and 60 mph vertical? Or am I confused

Only if you were falling at 60mph... If you were falling at 120mph, and traversing at 120mph, that would be a 1:1 glide ratio. Your forward speed would be about 170mph.

Gravity Waits for No One.

[PWScottIV 0]

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...As you track efficiently, you create lift with your body, and your rate of descent drops into the 80s or maybe high 70s.

Umm, the ONLY way you're going to decend that slow is with a wingsuit. Just because you can move sideways, doesn't mean you're generating enough lift to slow your decent rate to sub-terminal (~120mph).

Gravity Waits for No One.

[PWScottIV 0]

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120mph AIRSPEED gives you v*sin(x) vertical speed and v*cos(x) horizontal speed. So a 120mph max track at 45 degrees would give you an 85mph fall rate, an 85mph horizontal speed.

>To achieve 120 mph horizontal and vertical it would have had to have
>doubled in strength wouldn't it?

?? Speed skydivers go much faster without skydiving on Jupiter. It's all about controlling drag and lift.

(BTW to previous poster - no skydiving canopies I know of get a 4:1 glide.)

How sure are you that you can get your vertical velocity anywhere near that slow? I seriously doubt anyone can do that without a wingsuit. The physics you're proposing just don't make sense. Your body is not all that great of an airfoil with respect to creating a lot of lift. I know it's easy to fly fast horizontaly in a track, but that doesn't have a whole lot to do with "lift" like you see with an aircraft wing. It mostly has to do with the fact that the relative wind is glancing off your body at an angle.

Gravity Waits for No One.

[billvon 3,070]

>How sure are you that you can get your vertical velocity anywhere near that slow?

I'm not; I'm just explaining the math. Best (slowest) vertical speed I've been able to get in a track is about 90mph. Don't know what my horizontal speed was though.

[PWScottIV 0]

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I find it extraordinarily hard to believe that a good track can have a glide ratio greater than about 0.5. The aerodynamics of a body sucks. I'd probably believe wind tunnel data from a well-funded wind tunnel study of ski jumpers, but I'd want to look the experimental details over very carefully.

Agreed... It would be *nice* to think we could generate a lot of lift with our bodies, but that's just not the case. Most of what's happening in a track is essentially thrust vectoring... Biasing the flow of relative wind off one side of your body or the other. There probably is a very small amount of aerodynamic lift created in a max track, but without a wingsuit, the effect is probbaly going to be relatively imperceivable.

Gravity Waits for No One.

[Butters 0]

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I find it extraordinarily hard to believe that a good track can have a glide ratio greater than about 0.5. The aerodynamics of a body sucks. I'd probably believe wind tunnel data from a well-funded wind tunnel study of ski jumpers, but I'd want to look the experimental details over very carefully.

Agreed... It would be *nice* to think we could generate a lot of lift with our bodies, but that's just not the case. Most of what's happening in a track is essentially thrust vectoring... Biasing the flow of relative wind off one side of your body or the other. There probably is a very small amount of aerodynamic lift created in a max track, but without a wingsuit, the effect is probbaly going to be relatively imperceivable.

I may be wrong but I don't believe that you have to increase your lift to decrease your vertical speed and I do believe there are people who can achieve relatively low vertical speeds.

"That looks dangerous." Leopold Stotch

[Hooknswoop 19]

From an old post of mine:

Jump run was 1/2 mile west of the DZ and into the wind (South), I opened 2 miles to the East of the DZ. I drove the road from where I opened to the edge of the DZ and added 1/2 mile. The pilot used GPS to fly jumprun 1/2 mile to the West and maintain a straight jumprun to keep the competion fair (it was a whole otter load). Pro-Track for exit, opening altitudes and free-fall speeds.

I looked it up on Jump-Track
Exit:13,500
Deploy:2,100
Free-fall time: 102 sec
By my math that equals 76 mph avg speed and a 1.158:1 Glide ratio.

Simple math to figure out the vertical and forward speeds.

You can believe it or not. I tracked about a mile farther than anyone else on the load. There were about 20 other people tracking on that jump in the competition. If we had had a tail wind, everyone would have gone a long ways, they didn't. Most people do not track to the best of their ability. They track fast, which trades altitude for speed, they do not track for distance. Most people do not improve their tracking. They are content with how well they track, think they track a lot better than they really do, and that they are tracking to the best they possibly can.

Derek

[PWScottIV 0]

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I may be wrong but I don't believe that you have to increase your lift to decrease your vertical speed and I do believe there are people who can achieve relatively low vertical speeds.

How slow is "relatively slow"?

Gravity Waits for No One.

[Tornolf 0]

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How sure are you that you can get your vertical velocity anywhere near that slow? I seriously doubt anyone can do that without a wingsuit. The physics you're proposing just don't make sense. Your body is not all that great of an airfoil with respect to creating a lot of lift. I know it's easy to fly fast horizontaly in a track, but that doesn't have a whole lot to do with "lift" like you see with an aircraft wing. It mostly has to do with the fact that the relative wind is glancing off your body at an angle.

Wingsuits are terrible airfoils with respect to creating lift as aircraft do. Don't think about aircraft wings, think vortex lift.

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=2683420;page=1;sb=post_latest_reply;so=ASC;mh=20;
From the guy who's been designing wingsuits for nearly 10 years:

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4. Wingsuit flight speeds are not very appropriate for laminar airfoils. Simply, we are still way to slow and we are operating at to high angles of attack to use and fully exploit the benefits of laminar airfoils.
I have mentioned similarity in shape between wingsuit and space shuttle. For lift generation, space shuttle relies heavily on generation of vortices over the whole airframe. These vortices are accelerating the air flow around space shuttle, thus generating higher pressure difference i.e. more lift. We can assume that the same thing is happening with the airflow around the wingsuit (and it is rather difficult to obtain experimental confirmation for that, as I explained some time ago). So, in the end, some vortices (turbulence) does not have to be a bad thing in the end.

A waddling elephant seal is the cutest thing in the entire world.
-TJ

[NewGuy2005 53]

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You can believe it or not. I tracked about a mile farther than anyone else on the load. There were about 20 other people tracking on that jump in the competition. Most people do not track to the best of their ability. They track fast, which trades altitude for speed, they do not track for distance. Most people do not improve their tracking. They are content with how well they track, think they track a lot better than they really do, and that they are tracking to the best they possibly can.

Derek

Derek: I'm convinced. Please explain your secret to a new tracking enthusiast. Thanks!!

[Butters 0]

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I may be wrong but I don't believe that you have to increase your lift to decrease your vertical speed and I do believe there are people who can achieve relatively low vertical speeds.

How slow is "relatively slow"?

In the 70mph and 80mph range. Increasing drag will decrease vertical speed. Increasing lift will increase glide ratio. (Does this also decrease vertical speed? If so, then will increasing drag and lift dramatically decrease vertical speed?) I am very interested in this topic because I love tracking.

"That looks dangerous." Leopold Stotch

[PWScottIV 0]

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I may be wrong...

In the 70mph and 80mph range. Increasing drag will decrease vertical speed. Increasing lift will increase glide ratio. (Does this also decrease vertical speed? If so, then will increasing drag and lift dramatically decrease vertical speed?) I am very interested in this topic because I love tracking.

I agree, you are wrong. There is no way in hell that someone is slowing down to 70/80mph without a wingsuit. Anyone who says so is either lying or fooling themselves. Digital logging altimeters show speeds that slow sometimes, but it's only due to fluctuations in air pressure caused by variable airflow and burble around the unit.

Gravity Waits for No One.

[Hooknswoop 19]

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There is no way in hell that someone is slowing down to 70/80mph without a wingsuit.

How can you explain 102 seconds of freefall from 13,500 feet to 2,100 feet in an RW suit? How could I fool a Pro-Track into logging more free-fall time than actual time? How could I fool the exit or opening altitudes?

Newguy2005;

Flat Tracking

Tracking is a maneuver by which a skydiver can add significant horizontal movement to the vertical descent of free fall. It is used to gain separation from other skydivers making it safe to deploy their canopies without risk of collision. Flat tracking is the further refinement of tracking, gaining more horizontal distance for the same amount of altitude lost/used.

The more horizontal distance skydivers can achieve by tracking between the break off and pull altitudes, the safer they are. With the proliferation of very small, highly loaded, ultra high performance canopies, horizontal separation has become more critical. Canopy performance has out-paced tracking skills, especially as the median experience level of pilots flying their first high performance canopy declines. Instead of a skydiver piloting their first small, fully elliptical canopy after refining their tracking abilities over five hundred or more skydives, some skydivers are flying these canopies with less than one hundred skydives. In some cases, their tracking skills may not be up to the task. Body position and stability at opening are more important on high performance canopies, with even a slight turn or unevenness capable of creating line twists. This is sometimes not completely understood by lower experienced skydivers. The higher potential for line twists on opening combined with less than adequate tracking skills and high performance canopies creates a potentially dangerous combination.

Ensuring sufficient separation at pull time starts with setting a break off altitude high enough above pull altitude to give everyone enough altitude to track. Plan your break off altitude for the worst case scenario by starting at the highest pull altitude in the group and working backwards. Add enough altitude to that altitude for tracking, based on the size of the group. The larger the group, the more altitude that is necessary to be set-aside for tracking. Then add in enough altitude to allow enough time for the two highest performance canopies in the group to kick out line twists, while flying directly at each other, and turn away without a collision.

On the flip side of the coin, a very experienced skydiver, due to complacency from an adequate track and separation for the larger, lower performance canopies they have flown for years, over thousands of skydives, is no longer sufficient for the new, high performance canopy they recently purchased. This is not to say their canopy control skills are not up to the task, but the ability to flat track is a critical component to safely flying high performance canopies. Also, it can be difficult for a highly experienced skydiver to admit that their tracking skills need improving to keep the same safety margin they had with their previous, larger canopy.

Flat tracking achieves more horizontal separation by slowing the skydivers fall rate and by creating a low-pressure area near where he reserve pilot chute sits on the back. This low pressure acts as lift, the same way lift is created over the upper surface of an aircraft's wing. Slowing the fall rate and producing lift both decrease the steep-ness of the track, increasing the distance covered for the same amount of altitude used. Flat tracking is about achieving the best possible angle; it is not about speed.

Creating the low-pressure area is done by mimicking the shape of an aircraft's wing. In a flat track, as seen from the side, the upper surface of your body should be shaped similar to the upper surface of a wing. To get a good experience of this body position, get permission from the owner and/or pilot of a twin otter first. Explain to them what it is you want to do and have them show you how to climb up on top of the wing without damaging the aircraft. Then lay on the wing facing forward with your chin even with the leading edge of the wing. Matching the curve of the wing in free fall generates lift, producing a flatter tack. If a twin otter is not available, find someone to coach you and stand next to the wing tip of your DZ's jump ship and assume the flat tracking position. Have your coach use the curve of the wing as a guide to adjust your body position to resemble the curve of the wing.


Slowing the fall rate is achieved by presenting as much surface area towards the ground as possible, "cupping" air. De-arch slightly, tighten the abdomen muscles, point your toes, completely straighten the legs, and shrug the shoulders as far up towards the ears and down towards the ground as possible. Tightening the leg straps on the harness too much will restrict the shrugging of the shoulders, decreasing/limiting flat tracking performance. Of course, do not wear your leg straps so loose as to compromise safety. It is possible to over do this. If the track feels unstable or wobbles, ease off a bit.

Booties on your jump suit improves the initial acceleration of tracking by providing heading control and increases the maximum horizontal distance of a track.

A diving track gains horizontal distance and gives the tracker a sense of security and correct performance from the increase in speed he/she can readily feel. This feeling of security is false, as the tracker could gain more distance using a flat track, and therefore more separation, while feeling less speed.


Jumper "A" and "B" both track for 2000 feet, but because jumper "B" can flat track, he moves farther horizontally than jumper "A" does in a diving track.

Turning away from the formation and diving at break off to generate speed and then into a flat track is not the best technique to gain the maximum separation.

Again jumper "B" will out distance jumper "A" with a flat track. Jumper "A" will arrive at pull altitude before jumper "B".

On every skydive you are presented with an opportunity to practice, experiment and refine your tracking. Never be satisfied with your track, always strive to improve it. If you are going to spend an entire (or good percentage of a skydive tracking, let manifest, the pilot, and everyone else on the aircraft know your intentions. Generally trackers exit last, tracking perpendicular to the jump run for 9 seconds and then turning back in the direction of the drop zone, paralleling the jump run. This should leave plenty of separation from other jumpers. Exiting after a large group may require a longer track perpendicular to jump run before turning to parallel. Make sure, regardless of your position in the exit order, that you do not track over the top of any skydivers exiting before you, or track up under any skydivers that exited after you.

Flat tracking is a survival skill. The sport has recognized the need for more advanced canopy piloting training to curb the growing number injuries and fatalities associated with high performance canopies. Flat tracking training must keep pace with canopy development. The ability to flat track is important even for skydivers that don't fly high performance canopies. Awesome canopy piloting skills are worthless if you in a canopy collision on opening.

Derek

[billvon 3,070]

>Digital logging altimeters show speeds that slow sometimes, but it's only
> due to fluctuations in air pressure caused by variable airflow and burble
>around the unit.

We've seen those speeds on jumpers during long tracks (>30 seconds) coming off the World Team jumps. Digital altimeters can be fooled momentarily, but not for significant amounts of time.

[PWScottIV 0]

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>Digital logging altimeters show speeds that slow sometimes, but it's only
> due to fluctuations in air pressure caused by variable airflow and burble
>around the unit.

We've seen those speeds on jumpers during long tracks (>30 seconds) coming off the World Team jumps. Digital altimeters can be fooled momentarily, but not for significant amounts of time.

How was their decent rate being measured/calculated? I just don't buy it... The human body sucks when it comes to acting as an airfoil. Is there concrete scientific proof or is this just information from some guy/s? I'm not arguing about the ability to fly horizontally that fast, just not slow their decent rate to that slow. That's aproaching wingsuit decent rates...

Gravity Waits for No One.

[PWScottIV 0]

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There is no way in hell that someone is slowing down to 70/80mph without a wingsuit.

How can you explain 102 seconds of freefall from 13,500 feet to 2,100 feet in an RW suit? How could I fool a Pro-Track into logging more free-fall time than actual time? How could I fool the exit or opening altitudes?

That's why I wanted to see the data for myself. No offense, but I just don't believe that it's possible to slow your decent rate down near wingsuit speeds. It just does not make sense.

Gravity Waits for No One.

[Tornolf 0]

I can easily do 80's in a track in an RW suit. I can do lower in a tracking suit. Granted I am 6' and 130lbs, but it's very far from impossible.

And see my previous post. There's more ways to create lift than a traditional aircraft's airfoil.

A waddling elephant seal is the cutest thing in the entire world.
-TJ

[OSOK 0]

I've achieved horizontal speeds of 100mph and glide ratios if about 0.8, as per my GPS. It's not anything amazing, but neither is my jumps number

[billvon 3,070]

>How was their decent rate being measured/calculated?

Change in altitude divided by time.

>I just don't buy it... The human body sucks when it comes to acting as an airfoil.

Indeed it does. You can barely get over 1:1. But then again, if you blow an airplane to bits, the wreckage is often found scattered over a wide area. Some of those fragments, even though they are not designed at all to be aerodynamic, are found very far away from the crash site.

>That's aproaching wingsuit decent rates...

?? We're talking speeds around 80mph by the best trackers out there. Wingsuits are down around 30mph when flown by the best birdmen out there. That's over a 2:1 difference.

[PWScottIV 0]

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>How was their decent rate being measured/calculated?

Change in altitude divided by time.

>I just don't buy it... The human body sucks when it comes to acting as an airfoil.

Indeed it does. You can barely get over 1:1. But then again, if you blow an airplane to bits, the wreckage is often found scattered over a wide area. Some of those fragments, even though they are not designed at all to be aerodynamic, are found very far away from the crash site.

>That's aproaching wingsuit decent rates...

?? We're talking speeds around 80mph by the best trackers out there. Wingsuits are down around 30mph when flown by the best birdmen out there. That's over a 2:1 difference.

I thought typical decent rates for wingsuits were around 50-60mph... Someone cliamed they could get 70mph with just their body... I'd say that's "aproaching" wingsuit decent rates.

As far as wreckage, imagine how relatively slow a big sheet of aluminum would fall relative to a person. Now imagine there's wind pushing that piece. It's not hard to imagine how far it could get pushed.

Gravity Waits for No One.

[billvon 3,070]

>I thought typical decent rates for wingsuits were around 50-60mph...

Heck, _I_ can get to 65mph in a wingsuit, and I'm not a skinny guy with a big suit who does this every weekend! If you're comparing apples to apples (light expert trackers to light expert wingsuiters) then we're talking a comparison of 80mph to 30mph.

>imagine how relatively slow a big sheet of aluminum would fall relative to a person.

Right - but still, that big sheet of aluminum sucks as an airfoil. Unstable, wrong curves etc. Yet it still falls relatively slowly, and can frisbee quite far away.

[RB_Hammer 0]

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From an old post of mine:

snip...

I looked it up on Jump-Track
Exit:13,500
Deploy:2,100
Free-fall time: 102 sec

I know that I am a noob here, but I would tend to question some of your numbers.

My Alti-Track shows deployment altitudes that are much lower than I pitch, it seems to record the altitude I am in the saddle. I know that I come out of the track and slow before I pitch. There has to be some time there that recorded free-fall time is not tracking. Trimming off seconds from exit to track and from track to pull seems to be needed in your calculations.

"I'm not lost. I don't know where I'm going, but there's no sense in being late."
Mathew Quigley