Pin Tension & New Closing Loops

[Bodhisattva420 0]

The last time I went to the DZ I changed my closing loop after an experienced jumper informed me that it was too long. I was in a hurry to leave that day so I ended up doing a shitty job packing at the end of the day. Last night I remembered this and decided to open up my rig and repack it before I forget. Upon opening my rig I realized it took a lot more force to extract the pin. How do I know if there is too much tension on my pin? It freaked me out when I had pull fairly hard to extract the pin and would like to make sure it is safe before jumping it again.

[Rugby82 0]

For freeflying I always had a tight closing loop due to the differences in wind. Nowadays I do more FS4-video and C&P but still use a tight loop.

I can just lift my rig off the ground a couple of inches with the bridle of the pilot-chute before the pin pops out. It always opens well (have to make 2 seconds of freefall with a C&P).

As you can see the pin can be very tight and still everything will be ok.

Blue skies!

[skydiverek 63]

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The last time I went to the DZ I changed my closing loop after an experienced jumper informed me that it was too long. I was in a hurry to leave that day so I ended up doing a shitty job packing at the end of the day. Last night I remembered this and decided to open up my rig and repack it before I forget. Upon opening my rig I realized it took a lot more force to extract the pin. How do I know if there is too much tension on my pin? It freaked me out when I had pull fairly hard to extract the pin and would like to make sure it is safe before jumping it again.

The 28-inch Zero-P pilotchute (very common) generates approximately 160 lbs of force at terminal. I bet it required no more than 10 lbs to pull your pin. So, no worry. Old rule is: "If you can close the container by hand, it is not too tight". Bet on the 'tight' side, you don't want a horseshoe...

For different PC sizes and delays check the attached file.

[councilman24 37]

I see the copyright notice at the bottom of the page. How in the world can someone publish a table with delay as the x axis? ESPECIALLY a wingsuit company? Delay doesn't not correlate to speed, either vertical or total vector.

Are these calculated values and not experimental values? I assume they are calculated from the significant figures used in the table. No way would a direct measurement be valid to 5 significant figures. IF these are real measurements a force meter might have displayed 5 sig figures but I guarantee it wasn't that accurate.

Do you know what equations were used to caclulate these values? I don't know what equation would take into account the real world deceleration to terminal velocity, too many variables.

All that being said. Picking up a container by the bridle doesn't mean that it's too tight. Unless your doing an emergency exit with the main at 1000'.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[riggerrob 643]

Picking up a rig by its main bridle is a quick-and-dirty way to confirm that pull force is less than 22 pounds.

[chuckakers 426]

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Quote

The last time I went to the DZ I changed my closing loop after an experienced jumper informed me that it was too long. I was in a hurry to leave that day so I ended up doing a shitty job packing at the end of the day. Last night I remembered this and decided to open up my rig and repack it before I forget. Upon opening my rig I realized it took a lot more force to extract the pin. How do I know if there is too much tension on my pin? It freaked me out when I had pull fairly hard to extract the pin and would like to make sure it is safe before jumping it again.

The 28-inch Zero-P pilotchute (very common) generates approximately 160 lbs of force at terminal. I bet it required no more than 10 lbs to pull your pin. So, no worry. Old rule is: "If you can close the container by hand, it is not too tight". Bet on the 'tight' side, you don't want a horseshoe...

For different PC sizes and delays check the attached file.

How do you explain the drag forces on that chart continuing to get greater beyond 12 seconds of freefall? That is - give or take - the amount of time it takes to reach terminal. According the chart, I would still be accelerating after 18 seconds.

Chuck Akers
D-10855
Houston, TX

[Bodhisattva420 0]

Hey thanks a bunch! I guess I'm good to go since I didn't need packing tool to close it, just a pull up cord.

[skydiverek 63]

OK, how about this (attached)?

[davelepka 4]

OK, it is correct that tighter is better than looser in terms of closing loop tension. It is also true that if you can close the rig by hand, it's not too tight for the purposes of pin extraction, and general safety.

However, there is such a thing as 'too tight' in terms of the rig itself. Even if you can close it by hand, it may be too tight and risking damage to either the grommets or the stiffeners in the flaps.

Typically, it requires continual use with a tight closing loop to actaully damage the rig, so for one pack job and one jump, you should be fine. After that, consult a rigger or more experienced jumper when you go to close the pack job to make sure that it;s not too tight.