yuri_base

YALP (yet another low pull) 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 interesting to see the dynamics of full-flight WS opening. Before linestretch, the canopy is in the 'saddle' between bridle and lines, with its center of gravity lower than the suspension points. This makes the canopy orientation more stable, resisting any twisting forces. Maybe this explains why openings from full flight have better heading? (BTW, a 180 in this low pull would most likely ruin a day...) Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yo! A recent study by physicists at Moscow Institute of Physics and Technology showed that Coriolis force greatly affects the heading performance. It is a well known fact that toilets in the Northern Hemisphere drain counterclockwise, and toilets in the Southern Hemisphere drain clockwise, due to Coriolis effect. Similarly, given perfect body position and packjob, parachutes in Northern Hemisphere tend to turn left, while in Southern Hemisphere they tend to turn right. A control experiment involved three BASE jumpers - from USA, Australia, and Norway. The american got severe counterclockwise linetwists which he was not able to undo because his fat red neck was pinned by twists. The australian got a clockwise 180 which actually saved him as he was doing a triple gainer with a twist from a 200ft cliff and was facing the cliff as he pulled. The Norway jumper only got a 90 degree left offheading which saved him from hitting the wall on the opposite side of the 2-mile wide fjord he flew over at superterminal speed. This is consistent with the fact that Coriolis effect is greatest on the equator and zero on the poles. In fact, if you BASE jump at the North Pole, your heading will always be remarkably consistent - the parachute will always open to the south. Also, the winds at the North Pole for at least the last 100 years have been amazingly consistently blowing only from the south. Therefore, your canopy will always open perfectly into the wind, making landing very easy. A BASE jump at the North Pole is hard to do due to lack of buildings (B), antennas (A), spans (S) and earths (E). South Pole is more BASE-friendly, although it might take a while to find a bridge there. It is advised that the jumpers in Northern Hemisphere drop their right shoulder at pull time, and jumpers in Southern Hemisphere drop their left shoulder to counteract the Coriolis effect. If you forget the right direction, just drain the toilet before the jump! Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

In terms of glide ratio, yes. But for the thrill of flying at amazing horizontal speed, a sleek suit optimized for glide ratio 1.4 with minimum drag will beat wingsuits hands down. Prodigy pants do 140mph horizontally easy, but they are not optimized for minimum drag. A suit like this will be a true Speed Satan! Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Mike, welcome to the Ranch! Are you coming 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

Acceleration is the derivative of speed: a = dV/dt. This gives us the differential equation for speed: dV/dt = g*(1 - (V/Vt)^2) Integrating dV/(1 - (V/Vt)^2) = g*dt gives us inverse hyperbolic tangent on the left side and g*t on the right: Vt*arctanh(V/Vt) = g*t or (1/2)*ln((1 + V/Vt)/(1 - V/Vt)) = g*t/Vt and finally V(t) = Vt*(e^(2*g*t/Vt) - 1)/(e^(2*g*t/Vt) + 1) Fun, heh? Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Correct. ma = mg - Drag. At terminal velocity (a = 0), Drag(Vt) = mg. Since the drag is proportional to the square of speed, at speed V drag will be Drag(V) = Drag(Vt)*(V/Vt)^2 = mg*(V/Vt)^2. So, ma = mg - mg*(V/Vt)^2 a = dV/dt = g*(1 - (V/Vt)^2) QED

Hear, hear. Bringing the finest mental masturbation to the object near you. I wondered, too, if initial horizontal speed slows down your descent a bit. It turns out it does, but not too much. Long story short - on a BASE jump, you reach terminal velocity about a second and a half sooner than on a jump from airplane. This is because the high initial drag on a plane jump has a vertical component which slows you down a little more. If your terminal velocity is 120mph, you'll reach 95% of it (114mph) at 10.0s on a BASE jump and at 11.4s on a jump from airplane doing 100mph. This assumes that you maintain the same boxman body position - no lift, only drag - throughout. 11.4s is time to reach 114mph vertically; however, the total speed will reach 114mph at 10.6s (due to residual horizontal speed). So the difference is not really noticeable. Skipping the lengthy derivations, for BASE jump the speed V follows this differential equation: dV/dt = g*(1 - (V/Vt)^2) where t is time, g = 9.8m/s^2 = 32ft/s^2 is acceleration of gravity, Vt = 120mph is terminal velocity. This equation can be solved analytically: V = Vt*(e^(2*g*t/Vt) - 1)/(e^(2*g*t/Vt) + 1) where e = 2.718281828459045... (BTW, this formula can be used to derive freefall chart with a step less than 1s. Johhny? ) For an airplane jump, we have two equations for horizontal Vx and vertical Vy components of speed: dVx/dt = - g*(V/Vt)^2*Vx/V dVy/dt = g*(1 - (V/Vt)^2*Vy/V) which can be solved numerically using finite differences, see the attached spreadsheet. The only useful result of this masturbation is that if you want the softest opening possible on a hop-n-pop, wait 2 seconds before pitching (see how the green line, the total speed, makes a minimum of 85mph at 2s). This is based on 100mph jumprun (Twin Otter). For King Air, wait more. For Cessna, wait less. 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 someone have actually had a horseshoe in BASE, they couldn't post here. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

You say that like masturbation was a bad thing. When I step off the edge, I feel overwhelmed with the gratitude to the Founding Monkeys who started mental masturbation 30,000 years ago. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Yes, it's artificially inducing higher angle of attack and it's totally similar to improving your glide under canopy by pulling on rear risers. The best glide is very close to stall (pull a little more and the glide suffers dramatically - that's what happened on my last two unsuccessful flights). On rears, your forward speed decreases a little, while the vertical speed decreases a lot. That's exactly what happened when I accidentally nailed the magic glide: the forward speed dropped from 100-110mph to ~90, while fall rate decreased from 45mph to 30. While I can reproduce 100/45 (default trim) easily and repeatedly, so far I failed to reproduce 90/30. But that's only 3 flights in The Shoes, with them it's like totally different suit and it will take dozens of flights to nail it. With canopy, it's easy to find the best glide by using "the accuracy trick". With wingsuit, you can't use it because as soon as you look forward, you lose the glide and go into stall. You have to listen to the music of the air until you hear sirens singing. Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

You'll have to wait until 10/2/2025 for that to happen....

I wanna learn that! Here is an example how with ninja skilllllllzzzzz you can dayblaze a tower in Toronto, fcuk a cow, pick two 45y.o. chicks and Pigs won't even see you!!! Urban Ninja video

6-pack?! That was in the 20th century... now it's more like a 24-pack. A potential for 40% increase right there! Wait a minute... BEER... that's what we need! Forget clown shoes, forget lead weights... we need beer tanks in our leg wings!!! With a camelback tube to the mouth to dynamically adjust the distribution of beer between the two vessels for the perfect balance and 100% boost in performance!

I think that starting from aerodynamics (shape of wings) and then adjusting the balance using weights allows for better results than starting from human body's natural balance and sacrificing the aerodynamics to match the balance. It would be nice if manufacturers provided some guidelines on where the center of mass should be relative to wingsuit's geometry based on wind tunnel tests, so that users can adjust their balance on the ground. I wouldn't mind a day in horizontal wind tunnel. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Excellent, Johan!!!

Yo! Another 'fine' flight, this time at a fabulous 1.0 glide ratio!!! (the feathers must have grown backwards....) The two last flights with The Shoes sucked the big time, the first one showing ~3.0 for a few seconds (dynamic planeout), then quickly dropping to 2.0 and way below... the second was 1.0 all the way down (didn't correct it for the winds, though, but it sucked anyway). Couldn't figure out what was wrong, even looked over my shoulder, thought it must be PC in tow! -- so poor the glide was. Tried looking between the legs, rolling the shoulders forward... nothing. One foot down = one foot forward, baby. Welcome to The Stall! Here are my thoughts: Once you're trimmed leg-heavy, a slightest deviation from the perfect body position will send you to stall. Forward speed decreasing, the angle of attack increasing, repeat. Also, it seems to be very dependent on the previous 'history of flight' (hysteretic behavior). If you nail the angle in the first couple of seconds, you get the amazing glide as in the first post. If you don't nail it, forget it. Probably only a radical measure, like doing a spiral, will allow you to break the stall and try again. In rear riser analogy, if you pulled the risers past the stall point, it will be hard or impossible to return to the best glide (some rear risers) until you release them completely and go to full flight first. I can reproduce 2.2 in Phantom reliably in default 'trim' (head-heavy), but it will take many flights to nail that wonderful, but extremely fragile - close to a stall, but not a stall - 2.9. The investigation of the Mystery of Clown Shoes continues, stay tuned... or better yet, experiment yourself. Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

Nick, Please RSVP me for the next party. Preferrably a month in advance so I can find cheap tickets. Thanks! Yuri Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

To prospective students: to enroll in Maggot's FJC, you need to study the basics of ninja moves. This is an essential skill in urban BASE. Here is a video Maggot put together for the students (this is instead of "packing video" usually sent to students before the course... you don't need to pack to BASE jump!) Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

On a recent wingsuit flight, my cutaway cable was pulled about 1 inch down. The handle is internal and is right where the main lift web emerges from the wing. I guess on deployment when the MLW was jerked up, the wingsuit pushed the handle down. I had the 3-rings shut down (by loosely tying the small ring to the grommet) for backup, but I'll wrap the cutaway handle with gaffer's tape on future flights. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio

On the second thought, the 2-leg 180-degree method described in the first post probably beats the 3-leg method by simplicity while having very good accuracy. The 3-leg method is based on the fact that 3 points (ends of groundspeed vectors drawn from a common point) define a circle (the radius of which is TAS). The 2-leg method is based on the fact that 2 points also define a circle if we know the angle between radii for these points (in other words, if we know the difference in TAS bearing). In particular, the most accurate case, the 2 points are the ends of the diameter (2 legs with 180-degree change in bearing). How sensitive is the 2-leg method to the accuracy of the U-turn? A simple calculation shows that the error db in bearing of the 2nd leg results in relative error dA/A of TAS equal to dA/A = 1 - cos(db/2) For example, if you made a U-turn and your new bearing (relative to the 1st one) is 150 degrees instead of 180, TAS if off by dA/A = 1 - cos(30/2) = 0.03 = 3% That's typically just 3mph error - pretty damn good for a quite sloppy U-turn. The advantage of the 2-leg method is that it consumes less altitude - less chance of entering a layer with different windspeed - and only one turn is needed - less chance of distorting the body position and flying legs at different airspeeds. To sum it up: 1. Fly parallel to some straight feature on the ground (road). Make U-turn, fly parallel to the road again. ("fly parallel" means keep your body oriented parallel to road; the wind will actually blow you sideways (usually not noticeable, especially at altitude), and your actual path across the ground will be at some angle to the road). 2. Your true airspeed is: TAS = sqrt(G1^2 + G2^2 - 2*G1*G2*cos(g1-g2))/2 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! Klaus of Paralog digged out the information about a very clever way to calculate true airspeed (TAS) using 3-leg pattern. This approach doesn't require to fly the legs in predetermined directions like above. See "Measuring True Airspeed using GPS" at the end of this page: http://go.phpwebhosting.com/~khorton/rv8/phplinks/index.php?&PID=49 (I attached the article and the spreadsheet from this link for convenience.) It was developed by Doug Gray in 1998. Very elegant geometric solution!!! (gives a mental erection to those who like math) Here's what to do. 1. Fly a 3-leg pattern trying to maintain the same airspeed as best as you can. Freeze your body position and make turns in such a way that you can restore exactly the same body position. Fly straight legs long enough to collect enough datapoints but short enough to stay in the layer of the same windspeed (check the winds aloft forecast to see if the wind from 6K to 12K is about constant both in speed and direction). An equilatteral triangle pattern will give the most accurate result, but legs at 90 degrees will work great, too. 2. Calculate the average groundspeed and course for each leg from your GPS data. 3. Plug the numbers into Gray's spreadsheet and you're done! Many thanks to Klaus for productive discussion and finding this great stuff. Woohoo!

Yo! So, was it just 2 Ladies per 70 Dudes??? L/D = 0.029?! That's pretty lame L/D. Shouldn't it be, like, 100x greater? 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 not 200mph, but only 89mph (v = sqrt(2gh) = sqrt(2*0.079*10000) = 40m/s). Definitely survivable with fresh marshmallow (if it's deep enough).

Here we go. If (NEVER) is minus and (LOTS OF) is some big number N, by subtracting the two equations we get DANGER + N*FUN - BORING = - BORING - N*DANGER + FUN or (N+1) * DANGER = - (N-1) * FUN Since N is big, N+1 and N-1 are about the same and we can cancel them out. Finally, DANGER = (NEVER) FUN Since this is obviously not true, the above equations are mathematically incorrect. QED. Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio