Diving Line Twists on Reserve Canopies

[DonnellyB 2]

I've been searching hard for an answer to this question and I'm just not able to find it.  It seems to me based on all the various cutaway videos I've watched (very scientific, I know) that diving line twists almost never happen on reserve canopies.  Can anyone give me the technical explanation for why this is the case?  Is it something to do with the aspect ratio or trim of reserve canopies?  Should this knowledge inform anything about I fly reserve canopies (ex. if trim is different)?

Thanks in advance!

[RolandForbes 44]

 Id assume its for similar reasons that static line BASE jumps yield a lower off heading rate than handheld or stowed.. Would be interested as to the physics behind it but it seems removing PC oscillation may be a factor?

[gowlerk 2,072]

7 hours ago, DonnellyB said:

Is it something to do with the aspect ratio or trim of reserve canopies? 

Yes, especially the aspect ratio. Maneuverability and stability are standard trade offs in canopy design. There are many main canopies available that also are very stable and unlikely to have diving openings unless something is fouling the lines. But they are not as much fun to fly as "sportier" designs. 

[wsdm 0]

Reserves canopies tend to not have diving line twists by design. It's easy to know why as you absolutely don't want them when you deploy your reserve. If you think about it the other way you can sort of deduct why reserves don't have them. High performance canopies (that tend to have more diving line twists) for example have an extra 2 cells (so 9 instead of 7), a planform that's more elliptical especially at the sides (for those quick turns), a thinner airfoil (less drag = more speed), a higher aspect ratio, crossbracing. If you don't have all of these things by design you're basically left with a canopy that just wants to fly slow and straight and there you have it. 

 

 

Edited October 27, 2022 by wsdm

[DonnellyB 2]

Thanks for the answers!  It sounds like this is actually pretty straightforward.  I do wonder why I wasn't able to find this information anywhere else?  Might be operator error on my part!  

[wolfriverjoe 1,451]

On 10/27/2022 at 1:43 PM, DonnellyB said:

Thanks for the answers!  It sounds like this is actually pretty straightforward.  I do wonder why I wasn't able to find this information anywhere else?  Might be operator error on my part!  

Probably more because the inherent stability (or lack of) in varying parachute planform designs is a pretty obscure and esoteric subject.

It's not something many people are interested in.

Except on here, of course.

[nwt 131]

On 10/26/2022 at 9:59 PM, gowlerk said:

But they are not as much fun to fly as "sportier" designs.

Plenty of fun can be had flying a lightning