Bumping end cells and canopy stability

[bch7773 0]

I recently did a jump where we did a high hop N pop and bumped end cells. When somebody bumped mine, it caused both canopies to do a quick shudder and turned us away from each other about 20 degrees.
When I watched the same jumper bump end cells with another person, his canopy did another shudder, and turned and dove in front of the other guys. The bottom jumper had to walk across the other guys canopy.

is this a normal issue with bumping end cells? or maybe it occurs only on fairly highly loaded ZP canopies? (canopies were triathalon at 1.3, crossfire2 at 1.9, and sabre at 1.)

how do you CRW guys deal with this, if it happens to you?
(note, I have no CRW experience so forgive this if its a dumb question. I want to try real CRW at some point so I want to learn)

MB 3528, RB 1182

[TVPB 0]

You probably disturbed the airflow around the end cells of your canopies. This may have led to variations in pressure, air speed, lift, etc around the end cells. This in turn, leads to oscillations or shudders as you call it.

Changes in flying characteristics are common. But the response from the second incident you described is fairly radical and is probably due to a combination of bumping end cells too agressively or unsymmetrically (nose near tail with crossover for example), and an input from the canopy pilot to try and correct the initial "shudder". This input could be toggles or harness balance and can be either intentional or unintensinal.

CRW is great fun and you can learn a lot about flying canopies and aerodynamics.

BTW - the wing loadings you described are not that great. We were at 1.7 at last years world meet. I want to go to about 2.2 next time.

Stay Safe - Have Fun - Good Luck

The above could be crap, thought provoking, useful, or . . But not personal. You decide.

[Andrelr 0]

2.2, Tom?
With that old body of your's?

[TVPB 0]

Yes!

No pain, no gain.

Just because you Sout Efrikaans can' handle anything over 0.75.

Are we going to see you guys again?

Stay Safe - Have Fun - Good Luck

The above could be crap, thought provoking, useful, or . . But not personal. You decide.

[Andrelr 0]

Not for a while - I'm still stuck out here in the desert.
How did that op on your back go?

[superstu 0]

here's a question kind of related. i notice that when a friend and my self go up with our vx's at 2.2 and go to bump end cells our canopies end cells actually get sucked toward each other.
we've tried to stay as close together as possible with out touching and you can actually notice the fabric pulling toward each other. now why is this? airflow?

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down

[faulknerwn 36]

Absolutely! In the CRW world we call this end-cell suck... You're coming up beautifully for your end-cell dock, and suddenly you're just sucked into the formation! We avoid this by staying slightly farther ouside...

It has something to do with the vortices coming off of the wingtip of the canopy...

W

[parachutist 1]

Quote

here's a question kind of related. i notice that when a friend and my self go up with our vx's at 2.2 and go to bump end cells our canopies end cells actually get sucked toward each other.
we've tried to stay as close together as possible with out touching and you can actually notice the fabric pulling toward each other. now why is this? airflow?

Stu,

There are more unexpected anomalies that you are going to discover if you continue learning CRW under high performance canopies; some of it will not be so easy to correct for. I sincerely suggest learning with CRW canopies because they're designed for it and they give you a safety buffer while you're learning.

Something about HP canopies and CRW that could be fatal, but that is not so obvious: trailing pilot chutes. When someone disrupts the airflow in front of these they can start whipping back & forth, going forward farther than you'd expect. They can catch a line easily on either canopy and cause a serious mess of tangled people/fabric/lines. (Sharp small lines)

blue skies & soft grass,
Chris Warnock

[superstu 0]

i would love to do some CRW on 'slightly larger' canopies more designed for CRW, it would be fun! i have done about 250-300 CRW and even more non-contact stuff with my vx and i've seen some of the stuff you're talking about as well. but yes, slightly larger lightenings would probibly be better suited for what we are doing. thanks

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down

[Shark 0]

I've done a little on a Stiletto 370.