Rotation of canopy in static-line jumps

[jason]

Noticed something going through some of the video from a recent series of static line jumps. Very consistently, the canopy takes on a rotation in the saggital plane of the jumper (the attached diagram might be helpful). I've reasoned this through, and I'm certain it's due to the fact that the middle fold of the canopy rotates by 180 degrees during deployment (or very nearly) and carries that rotation through until line stretch.

The problem is that by the time line stretch is reached, the canopy is nearly 90 degrees off of the line from the attachment point to the jumper -- ie, tailpocket UP on a standing exit but still on-heading -- and gets WRENCHED into alignment when the jumper's weight hits it. It might be a small thing, but it seems to me that the packjob as presented to the wind (ie, after it is pulled into alignment) must bare only a little resemblance to the one I put in the tray, and I'm actually surprised at the consistency of the deployments having seen this.

Anybody else noticed this? Anybody have a fix?

[crwper]

Can't access the attachment -- do you have a still shot of the phenomenon you're describing?

Michael

[imported_Tom Aiello]

I'm not following.

What is the "saggital plane of the jumper"?

Which direction is "tail pocket up"? Does that mean the topskin of the canopy (to which the tail pocket is attached) is facing up? Or that there is a 180 degree bend in the lines themselves between the locking stow and the line attachments?

Please elaborate. And, perhaps re-link the diagram?

Thanks.

--Tom Aiello
tbaiello@mac.com

[jason]

Hmm... The link does seem to have disappeared. I've re-attached here.

The saggital plane is the one that divides you into left and right halves. The rotation I'm talking about is like the canopy, s-folds undone, tailpocket facing backwards relative to the jumper, does a front flip as it moves away from the jumper. It gets through almost 90 degrees of that rotation before the jumper hits linestretch.

Check out http://www.ucalgary.ca/~jcooper/slowmo.mov for an example.