burns next to tail pocket

[guest]

I noticed something interesting the other day at Perrine...
(The jumps were all no slider of 1 to three seconds delay)

I was interested to see that many of the canopies would spread out spanwise then cordwise. The pilot chute bridle drops behind the canopy before the cordwise expansion and then is pulled forward. As several of this type opening occurred I noticed that the bridle would drag across the top skin of the canopy and it was interesting to note that the closing flap of the velcro rigs would sometimes catch on the trailing edge of the canopy and pucker it towards the front then release it. It made it very obvious that the bridle is being drug across the rear/top skin at or around the area of the tail pocket.

questions...
1. Are many experiencing burns at the trailing edge because the bridle is being drug across as the canopy expands cordwise?

2. Would it be worth adding a small area of cotton adjacent to the tail pocket to avoid burns.

3. I have a "multi" point pilot chute attachment system. Could these burns be related to the sheath for it?

[imported_Tom Aiello]

>I noticed something interesting the other
>day at Perrine...
>(The jumps were all no slider
>of 1 to three seconds
>delay)
>
> I was interested to see
>that many of the canopies
>would spread out spanwise then
>cordwise. The pilot chute bridle
>drops behind the canopy before
>the cordwise expansion and then
>is pulled forward. As several
>of this type opening occurred
>I noticed that the bridle
>would drag across the top
>skin of the canopy and
>it was interesting to note
>that the closing flap of
>the velcro rigs would sometimes
>catch on the trailing edge
>of the canopy and pucker
>it towards the front then
>release it. It made it
>very obvious that the bridle
>is being drug across the
>rear/top skin at or around
>the area of the tail
>pocket.
>
> questions...
>1. Are many experiencing burns at
>the trailing edge because the
>bridle is being drug across
>as the canopy expands cordwise?

I have definitely also noticed line burns on the trailing edge of my canopy. However, I had though they were the result of tail inversions on deployment, and were caused by the lines on the underside of the canopy, rather than the bridle. I theorized that the tail was inverting through those lines, and the burns occured as it inflated past them.

>2. Would it be worth adding
>a small area of cotton
>adjacent to the tail pocket
>to avoid burns.

I have no idea. I think it might be better to address the underlying cause, rather than to bandage the problem area.

>3. I have a "multi" point
>pilot chute attachment system. Could
>these burns be related to
>the sheath for it?

This is the most interesting part. I have two canopies, a single attachment point (Mojo 260), and a multi attachment point (Fox 265M) bridle. I have NOT seen any line burns on the Fox with the multi.

I had assumed that the multi, by supporting the tail pocket through deployment, was preventing the tail inversion that caused the line burns on the canopy with the single attachment point. Your experience, however, makes me re-examine my assumption.

Do you have video of the bridle sliding across the tail pocket? I would be very interested in seeing it.

I am planning a trip to the same bridge for next weekend (22,23,24). I'll try to shoot some top down video on that trip, and see if I can verify your findings.

Does anyone else know anything about this? I know BR did some test jumps where they looked at tail inversions (while developing the multi)--anyone know what they found?

--Tom Aiello
tbaiello@ucdavis.edu

[guest]

I don't have any video of my own but I assure you that you will see it on top down views. It is especially obvious when the closing flap catches on the TE momentarily. Like I said the pilot chute drops below the TE before chordwise expansion and must be drug forward over the aft/top skin. I think I got my burn on a 3+ second no slider delay. BTW... I use a tail gate tightly bound with a rubber band too.

[guest]

What were the wind conditions on your jump? Tail? Head? How strong? I'm wondering if wind misdirecting the pilot chute might share some of the blame.

--Tom Aiello
tbaiello@ucdavis.edu

[guest]

Good question Tom. Now that I think about it I can't quite say. We were jumping in light to no head winds and then in fairly strong (5-15+ mph) tail winds. Hmmmmmm...