yuri_base

Does the better glide come from the increased forward speed and the same vertical speed, or the decreased vertical and the same forward? (compared to other canopies of the same size at the same loading) Is BlackJack trimmed at the maximum of glide ratio (does a small rear riser input result in decreasing GR?) or you have some range on rears to improve GR? For what it's worth, vented Flik has a terrific GR, but it seems to be at its max in default trim. Imho, it's better to have both "up/down" options than just "down"... Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us All your BASE are belong to us Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Another nugget. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

By the way, that little graph (L/D vs. AoA) has some valuable - and precise - result hidden in it. If we convert it to L/D vs. Pitch (using formula Pitch = AoA - GlideAngle = AoA - arctan(1/(L/D))), we get this graph. L/D for the G3 flight (correctly extracted from planeout using acceleration data) was 1.6. Looking at the graph, the pitch angle corresponding to L/D=1.6 is either 5 or 23 degrees. To achieve the maximum L/D=1.8, the pitch should be ~10 degrees. Some balance tuning is needed to achieve the perfect pitch. The cleanest way to change balance is to use weights to shift the center of mass. The aerodynamic way to change the balance - changing the relative surface areas of different parts or changing body position - is more tricky, since it changes L/D curve itself, so the whole analysis needs to undergo several iterations. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Maybe Texas gang can argue about what the shape of the L/D curve is all about? Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yes, I started from standard airfoils and then "dumpened" the data a bit to take into account low aspect ratio and the fact that wingsuit consists of sections with very different characteristics. The absolute values are not important, they are just a vehicle to observe the trends and demonstrate the point. I think you're absolutely right about the absense of the stall drop in lift curve for trackers. See the attached graph, it's the windtunnel data from VKB's post in BASE forum about their G3 tracking suit. There's just a tiny dent, if any, on lift and L/D curves at 15 degrees AoA. In this case, there's no "stall barrier" and the pitch angle is unambiguously related to the glide ratio. We can only guess about real lift and drag curves for wingsuits. I still think that we do have the stall "drop", just because with the stall, the L/D curve is very sensitive to AoA near the best glide, and that's why it is so hard to find, and that's what we observe in practice. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

I agree with your thoughts. You explained in plain English what I'm trying to explain with squiggles. You can easily derive the equations if you write the components of forces: Fx = L*sin(A) - D*cos(A) = 0 Fy = M*g - L*cos(A) - D*sin(A) = 0 (L = lift, D = drag, A = glide angle, M = mass) and then replace sin and cos by sin(A) = Vy/V cos(A) = Vx/V and lift and drag by L = (1/2)*Cl*ro*S*V^2 D = (1/2)*Cd*ro*S*V^2 where ro is the density of air, S is the surface area of wingsuit. ro, S, and M end up being wrapped in an empirical constant K: K = sqrt(2*M*g/(ro*S)) Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

That's THE SPIRIT!!!

Now we're talking! Now, that's the collective brainpower of creative individuals sharing their passion! So if we have a pitot tube with two pressure sensors measuring dynamic and static pressure, we know absolute airspeed V and vertical speed Vy. Then we know the horizontal speed, too: Vx = sqrt(V^2-Vy^2). So we have an L/D meter: L/D=Vx/Vy. This will be a much more accurate L/D meter and provide instant feedback to the flyer e.g. via beeps, like vario. The pitot tube will need to be mounted on a weathervane to point into the airflow. Maybe this is what's on the head of the Gibolin guy. But it seems they don't want to share. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

I noticed this "stall entrapment" mostly occurs after flat turns. So far, it happened just a few times - a couple of times on balloon jumps (light winds, not affecting groundspeed much), once in BASE (after flat 135 degree turn; no wind), and a couple of times on plane jumps (very poor glide in maxed out position, thinking, must be strong headwind, flat-turning 180 and still having very poor glide, like 1.0). We need to understand the nature of the glide destroyers - more predictable stall entrapment for one and unpredictable flutter for two - to efficiently fight them. Poor glide sometimes is just not healthy. Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yo! Ever get a jump when it feels all wrong... you max out the suit, but barely move forward and get crappy glide ratio and can't figure out what the hell is wrong? Well, now you can blame basic aerodynamics instead of blaming yourself! Here's a little masturbation demonstrating why sometimes it's just not your day. If lift and drag coefficients Cl and Cd as functions of the angle of attack are known, the glide ratio L/D as a function of AoA is simply L/D = Cl/Cd the pitch angle (angle of your body to horizon) is Pitch = AoA - arctan(Cd/Cl) and horizontal Vx and vertical Vy speeds are Vx = K*Cl/(Cl^2+Cd^2)^(3/4) Vy = K*Cd/(Cl^2+Cd^2)^(3/4) where K is some coefficient proportional to the square root of your wingloading. You can estimate K by matching the polar curve Vy(Vx) with your horizontal & vertical speeds in maxed out position, as measured by GPS. The attached spreadsheet contains some model Cl and Cd curves for some wingsuit and the resultant L/D, pitch, speed, and polar curves. (For the discussion of lift/drag coefficients at high angles of attack, see this article.) You can drag the points on Cl and Cd curves and see the effects. Also, adjust the coefficient K in cell A2 to realistically match your speeds. Take a look at the "L/D vs. Pitch" curve. This curve tells us that at a pitch angle of -10 degrees (headlow 10 degrees below the horizon) your glide ratio can be 1.0, 2.1, or 2.7. 2.1 occurs at the stall, at AoA=16, and thus is an unstable situation. 1.0 (AoA=35 degrees, post-stall) and 2.7 (AoA=10 degrees, pre-stall) are potentially stable, if the total momentum of all forces is zero. (For now, let's assume it is.) So, you can "max out" and your body is at "usual maxed out" pitch of 10 degrees below the horizon, and yet in one case you fly like a bird at L/D=2.7, while in the other case - same body position, same pitch - you fall like a brick at L/D=1.0. In the first case, your fallrate is 39mph, in the second 53mph. Sounds familiar? Horizontal speeds are 106 and 53mph, respectively. Conclusion: the stall introduces a potential barrier which separates the efficient flying from inefficient. You can assume your maxed out body position and yet be at the slow end of the stall barrier and get poor glide (depending on previous history of flight, hence the "hysteresis" title). To "hop" over the barrier, you need first to increase your forward speed dramatically (by, for example, collapsing the arm wings and thrusting at full throttle with the leg wing). No more wondering, "what's wrong?!" Something to try this weekend. Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

It's odd, indeed: the day I switched to packing grommet-to-BOC (~100 jumps ago), the occurrence of linetwists magically decreased from ~10% to zero and stayed at zero ever since. Also, I had a linedump on one of the flights before the switch. As the bag rotates almost 180 degrees, "scrubbing" the container, it could drag the stowed lines through the excess lines and open the bag. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

- Trying to detect radiation by sensing it. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Looks like he lost the right toggle: the tail is flapping as there's no tension on it. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yo! Here's the angle to skydiver as seen from airplane for various jumprun airspeeds. The methodology of calculations can be found here. As you can see, 45 degrees can only be seen at some special airspeed of 135mph. But variation of the angle is too small anyway to make it a practical indicator. Next! Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

If you order an all-pink XXXXXL Prodigy, you'll definitely plummet with style! Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yo! While playing with some calculations (don't ask ), I scaled the polar curve to different weights and found answers to some old questions. Take a look. The blue curve is a polar curve -- vertical speed vs. horizontal speed -- for a 230lbs (exit weight) jumper in some imaginary wingsuit. (the small numbers by the curve represent the angle of attack.) The orange curve is a 170lbs jumper of the same physical dimensions in the same suit. The jumpers have the same body positions for every flight mode, the only difference is weight. They both have the same maximum glide ratio (2.2), achieved at the same angle of attack (14 degrees), but their minimum fall rates are noticeably different: 44 and 38mph, respectively. Basically, the lighter jumper's curve is simply the heavier's one scaled by the factor of sqrt(170/230). The semitransparent areas inside the curves represent the range. You can fly inside your range by partially collapsing wings, arching, etc. You cannot steadily fly outside the range, you can only "peek" outside by, for example, diving and planing out. They can flock inside the intersection of their ranges. Star shows one possible - if not typical - flocking point: 80mph forward, 65mph down. Now suppose at breakoff flyers "pop": while maintaining the same forward speed, they try to decrease their fallrate as much as they can. Mr.Phatty can only slow down his phat ass by 9mph to 56mph, while Mr.Skinny floats like a helium balloon straight up to his minimum rate of 37mph, a whopping 28mph change. Different scenario: at breakoff flyers remain on the same level (65mph down), but increase the forward speed to the max. Skinny is much closer to the right boundary of his envelope and reaches almost 100mph in an instant. Phatty, since he was flying almost in a stall (his AoA was almost 20 degrees), needs first to break the stall (spilling a lot of air), then accelerate every one and each of his 230 pounds and by the time he reaches 100mph, Skinny already disapeared on the horizon. While Phatty is able to achieve speeds up to 115mph horizontally, it's time to pull before he can reach them. Short version: the performance of different wingsuits and flyers cannot be judged by observing the range when flocking and "smoking ass" on breakoff. High-performance machines specifically designed with BASE in mind can only be objectively evaluated in BASE. Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Theoretically, if you use the 45 degree exit technique (the most efficient one) on WS BASE jump, the bigger the better because the distance you cover in the first 5-6s is directly proportional to the effective surface area (this is because at 45 degree AoA, the actual geometry of flying body has little effect on the lift coefficient). For example, if you can clear a 200ft-wide ledge in Prodigy, and Vampire's effective surface area is (for example) double of Prodigy's, you'll outfly a 400ft ledge in Vampire over the same height. Put Prodigy, Phantom, and Vampire on top of each other. Phantom is actually not so much larger than Prodigy, while Vampire is significantly larger than Phantom. So while Phantom gives you the convenience of BOC in BASE, Vampire is the way to go, since it starts flying faster... Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

That's what you want the device to tell you. Two things: L/D and AoA. P.S. Of cource, L/D(AoA) curve is only useful when body position is frozen throughout the flight and you can reproduce it reliably on subsequent flights. Otherwise, you may achieve 16 degrees AoA by bending your knees, but the aerodynamics will change and L/D will become 2.0. If you have the same body position from flight to flight, the purest way to change AoA is by using weights to move center of mass. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yo! More input. If horizontal & vertical accelerations Ax, Ay and velocities Vx, Vy are known for a given moment in time, one can calculate the momentary L/D ratio (which is not equal to glide ratio in non-sustained flight) using this formula: L/D = [Ax + Vx/Vy*(g - Ay)]/[g - Ay - Vx/Vy*Ax] (here g is the acceleration of gravity) This is the precise formula based on Newton dynamics; it does not depend on actual aerodynamics of the flying body. Acceleration can be measured using AHRS with accuracy 0.01g or better, making the integrated velocity reasonably accurate during the first few seconds of WS BASE flight. This will give an accurate L/D curve as a function of time. If you combine this data with the body pitch angle data from AHRS, you get the L/D curve as a function of the angle of attack (AoA = glide angle - pitch). This is a very valuable piece of data: only folks with horizontal windtunnels have a luxury of having it! L/D(AoA) graph may show, for example, that your sustained AoA is 10 degrees and corresponding L/D = 2.4; but at 16 degrees, L/D = 2.8. You'll be then like, "hmmmm...." Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

An accurate GPS combined with Attitude and Heading Reference System (AHRS) would make a great tool for wingsuit, especially for WS BASE, where accurate acceleration and velocity data allows one to "scan" the Lift/Drag ratio for various angles of attacks during the initial ~30 seconds of flight. This will allow you to find the angle of attack that gives the maximum L/D. I researched this a bit lately and found that existing AHRS are too expensive: Crossbow AHRS board equipped with GPS - $1500 Xsens MTi - more than $2K It sounds like an interesting project!

We already have one verse, created by Maggot: "BASE is sweeter than the morning dew Glistening on a rose petal As the sun rise's Over all of our kindered spirits"

It's spelled whorehouse. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Interestingly enough, it was V-2 where flutter was first discovered. V-2, a German rocket used to bomb London in 1944. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

What kind of sensor do you use attached to weathervane and how the output is recorded/monitored? Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio