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GentleTiger

canopy lunge explained

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I talked with one of the guys at my dz (I swear these guys know EVERYTHING!), and the explanation for the canopy "lunging" on opening follows:

when the canopy is inflated and turns into a "wing", it begins forward motion, but since I'm still falling vertically, it appears as a lunge since I'm not underneath it right away as it begins its forward movement.

tadaaaa! ;)

blues to all,
Tiger
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Look, up in the sky! It's a bird! It's a plane! It's a tiger in the sky!! Throw down some steaks and run for the hills!!!

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So you tow the canopy until it opens and then it flies in front of you?

Sounds more like opening head low. If you open head low your body travels forward pretty quick. The canopy stops you but it's some what behind you. As you pendulum underneath it it surges forward.

Just a hunch.

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no...I watch as the canopy opens and the slider comes down, but I'm still falling straight down as the canopy begins flight. It just appears to be lunging in front of me, but it actually isn't. I don't think you get quite the same affect under smaller canopies...this is a big ol' Navigator 260, so it's much more obvious. Check it out. :)
bbs
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Look, up in the sky! It's a bird! It's a plane! It's a tiger in the sky!! Throw down some steaks and run for the hills!!!

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wouldn't that depend on the wing loading?

it seems to me that if you have a higher wingload, it would be less obvious because your weight under a small canopy would bring you under canopy sooner. My windload on a Nav 260 is .65, so I'm still falling when the canopy starts flying forward.

do you have any explanations for the phenomena?

I'm not asking you to believe me, I'm inviting you all to check it out for yourselves. :)
blues
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Look, up in the sky! It's a bird! It's a plane! It's a tiger in the sky!! Throw down some steaks and run for the hills!!!

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Sorry man ... if you're still falling the canopy isn't inflated yet. I have lots of jumps and big and small canopies. If the surge, it's either to deep of a brake setting and it stalls then surges forward, or I believe it's what I said earlier.

I haven't jumped a Navigator in a while, so what the heck! Of course it will be 3 weekends till I'm back at the DZ I jump at. Remind me after next weekend say the 15th or 16th to give it a shot.

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My windload on a Nav 260 is .65, so I'm still falling when the canopy starts flying forward.



I'm not sure what you mean by that. What does the wingloading have to do with it? I think the surge you're feeling occurs as your canopy recovers from the stall it's in during the opening. Maybe that's what you're saying actually. There isn't really a distinct difference between falling and flying. I mean, there comes a point when the drag and lift from your canopy slows you down to a new terminal velocity (your descent rate). But I think you mean the same thing I do...

Dave

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until the canopy is fully inflated, you're still falling vertically...it's when the canopy is fully inflated that you begin forward motion.

now me, having a butt the size of manhatten :S, am slow to move forward...in fact, there is no forward motion until the canopy starts flying (fully inflated).

I guess technically, the canopy is in a stall until it fully inflates?

blues
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Look, up in the sky! It's a bird! It's a plane! It's a tiger in the sky!! Throw down some steaks and run for the hills!!!

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I can't agree with you.

For me to have that sort of wingloading, I go back to jumping solo on tandem gear during my rating course.

Under a Sigma 370 and a wingloading of about .7:1 I didn't notice anything like what you're describing.

The only time I ever had a "lunge" or surge or whatever you want to call it is the time I forgot to set my brakes on my Heatwave (loaded 1.7:1).
--"When I die, may I be surrounded by scattered chrome and burning gasoline."

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I was not aware of any phenomena resembling what you described on the Navigators either... I even recently jumped a 280 loaded at ~.7:1 since it was the only thing packed right before I got my "A". I have decent body position and my openings have been very undramatic to say the least.

I defer to the experts on this one but make sure that you are pulling from a stable body position and not subconsciously aniticipating the "snatch" before the canopy inflates.
NSCR-2376, SCR-15080

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This happens if you have momentum (forward or backward) while dumping. Make sure you have *stopped* moving horizontally and have a stable, level body position before tossing out.

Other explanations to this problem seem (to me) to be excuses for not flying your body right.

Shane

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OK, here's how dem der par'chutes inflate y'all. (simplified)

1. Pilot chute is released and decelerates, pulling the parachute to line stretch.

2. "Snatch Force" The parachute is accelerated again by the load (jumper)

3. "Openning shock" The parachute begins it's inflation, exerting force, decelerating the load (ouch).

4. Flight (really simplified). The canopy accelerates forward due to the shape of the wing.

This surge accelerates the jumper forward until braked flight is achieved (Unless you forgot to set your brakes). The canopy will pivot down slightly until the jumpers speed and the canopy's speed are matched when acceleration stops. The faster that mode is, the more surge you will experience.
A higher loaded wing or or unstowed toggles = more surge
I would imagine a larger canopy would surge less because the size would create more parasitic drag. Pilots out there?
I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet.

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Thats not true either, I have tons of forward speed on Birdman flights and I never have a canopy surge on opening.



Not maybe a forward surge. But sometimes backwards. I have had two strange openings while dumping my FX70 at full flight. The canopy stalled during opening and "fell down" back of me for a while. Not a nice feeling. I was used to dump at full flight with S1 but with S3 it doesn't feel like the best way to go.

"Fear is the path to the Dark side"
(Master Yoda)

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wow, really good thought mig...along with what teason said, I could well be bringing my feet up to my butt and flying backward on opening...so the surge and backward flight could exagerate the "lunge"...will check that out, thanx!!

blues,
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Look, up in the sky! It's a bird! It's a plane! It's a tiger in the sky!! Throw down some steaks and run for the hills!!!

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Yes you are correct. They tend to stall somewhat backwards then rock forward. Watch a 360 tandem reserve with the brakes set.

A short delay on a BASE canopy with too deep of brakes, will most often just start to fly backwards and will not rock forward.

There's some good explanations above. Back sliding, forward motion....

Now that I think about it, after the brakelines shortened on my stiletto, it would surge like crazy.

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The only time I ever had a "lunge" or surge or whatever you want to call it is the time I forgot to set my brakes on my Heatwave (loaded 1.7:1).



how was the opening? did you have to add brakes to get the slider to come down? -i did the same thing on a velocity and i dont think the slider would have come down without brake application. that was one of the craziest deployments i've ever had...

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