Reserve deployment time/altitude and size

[Hooknswoop 19]

What do you think will deploy faster (least amount of altitude), a PD 218R or a PD-106R, given all other factors are the same (airspeed, weight of jumper, same type of container, etc)?

Derek

[ChrisL 2]

I would think the larger area on the PD218R (this is my reserve btw)
would create more drag, catch more air, and bang open faster.
Of course I do not claim to be any kind of authority on the subject.

__

My mighty steed

[ladyskydiver 0]

**Disclaimer: Not an expert by any means **

I would actually think they'd open in the same amount of time.

Life is short! Break the rules! Forgive quickly! Kiss slowly! Love truly, Laugh uncontrollably. And never regret anything that made you smile.

[lummy 4]

I'll guess the 106 because the wingloading would be higher and would give a faster decent thereby creating more drag

I promise not to TP Davis under canopy.. I promise not to TP Davis under canopy.. eat sushi, get smoochieTTK#1

[hookitt 1]

All things equal, the 106 would have a slight advantage. Less weight for the pilot to anchor. Less air needed to fill the canopy.

My grammar sometimes resembles that of magnetic refrigerator poetry... Ghetto

[davelepka 4]

I would guess they would be pretty close. The 106 is lighter, so the reserve PC could pull it to line stretch faster, and the lines are shorter, so again, to line stretch quicker.

As far as inflation, the 106 has less volume of air needed to fill it, but smaller inlets to allow that air in. It would seem that the 218 would slow the airspeed considerably before it was fully inflated, maybe slowing the end stages of inflation.


I'll say the 106 will pop open quicker.

[FrogNog 1]

Is your question just about which one will reach full inflation quicker, or is it also about which one will decelerate the jumper to a survivable descent rate quicker, too? (Just asking.)

[nicknitro71 0]

By weight of jumper what do you mean? Are both at the same WL or the 218 is more lightly loaded?

Memento Audere Semper

903

[BIGUN 1,483]

My answer is: 300 feet or three seconds from the time the container opens - same time; irregardless of weight or w/l.

Nobody has time to listen; because they're desperately chasing the need of being heard.

[Hooknswoop 19]

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Is your question just about which one will reach full inflation quicker, or is it also about which one will decelerate the jumper to a survivable descent rate quicker, too? (Just asking.)

Fully open for both.

Derek

[Hooknswoop 19]

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By weight of jumper what do you mean? Are both at the same WL or the 218 is more lightly loaded?

Same weight under both, the 218 would be more lightly loaded.

Derek

[Kris 0]

I'm going to go with the bigger canopy.

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[brits17 0]

The 106. Shorter lines, greater snatch force, lighter canopy weight... that's my guess.

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[jumper03 0]

time wise, I'd say the smaller reserve. Less altitude for the bigger one.

No scientific reason, just gut feeling....

Scars remind us that the past is real

[AMax 0]

Is there any experimental data?

[Canuck 0]

I believe in the BASE community it is accepted that smaller canopies open faster than larger ones...

Canuck

[BIGUN 1,483]

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I believe in the BASE community it is accepted that smaller canopies open faster than larger ones...

Why?

Nobody has time to listen; because they're desperately chasing the need of being heard.

[Canuck 0]

Dunno. I'm not in that community, I just lurk their posts every once in a while, and I remember seeing Tom A writing something to that effect. I do know that the BASE people (for obvious reasons) have devoted much research to finding out what opens fast.

Canuck

[TomAiello 26]

Some disclaimers:

1) I know next to nothing about canopies as small as the 106 under discussion here. What I've learned from larger canopies may be applicable, but it may not.
2) I'm not an expert on skydiving. Skydiving and BASE canopies vary quite a bit in lots of particulars (in this case, BASE canopies are made to open quickly, where the skydiving reserves in question may not have this as such a prominent design criteria).
3) While I'm fairly confident that this all applies to slider-up (i.e. using a slider to reef deployment) BASE canopies, my knowledge is primarily based on slider down deployment observations. The observed differences in slider up canopies are much less consistent.
4) If you are talking about a very subterminal slider up deployment, the variations in individual deployments are likely to be so great that individual deployments are barely indicative of average opening speed.

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I believe in the BASE community it is accepted that smaller canopies open faster than larger ones...

Why?

My observation has been that, all else equal (i.e. same canopy design, same jumper, same conditions), smaller canopies will open faster.

I believe there are several reasons for this:

1) Less fabric in the canopy means less time to "unfold" the pack job.
2) Less internal airspace in the canopy means less time to full pressurization, assuming air inflow occurs at roughly the same rate.
3) Shorter lines means less delay between container opening and line stretch (hence the start of bottom skin expansion as a precursor to cell inflation).


On separate, but related issues:

1) Canopies with higher wingloadings will tend to open slightly faster than canopies with lower wingloadings. This effect is not nearly so great as the pure size difference in the canopy, though.
2) Canopies need time to decelerate the load (i.e. jumper). This means that a lighter jumper will reach full deceleration (and full canopy controllability) sooner. This is because a heavier jumper will still be decelerating when the lighter jumper has finished.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[BIGUN 1,483]

Thank you for your time, Tom. It is appreciated. Makes my "same time" answer wrong, but I learnt sumpin.

Nobody has time to listen; because they're desperately chasing the need of being heard.

[EvilLurker 2]

"Canopies need time to decelerate the load (i.e. jumper). This means that a lighter jumper will reach full deceleration (and full canopy controllability) sooner. "

I agree with this. The larger canopy will expose more surface area, resulting in more drag and a quicker deceleration, and will decelerate to the point that the slider comes down faster (and with less altitude loss) than a smaller canopy of the same design under the same weight. A BASE rig, with no slider or a mesh slider, may or may not exhibit the same characteristics. I'll let the BASE guys answer that, they will have studied it a LOT, I'm sure. The shorter suspension lines between a 106 and a 200+ would amount to what, about 6 feet? Terminal is 180 ft/sec. or 1/30 sec. line-stretch difference. I think the deceleration from a much larger area would quickly overcome that advantage. Something not mentioned was whether the pilot chutes were equally sized, or were the recommended size for each canopy, because that would also have an effect.

[Hooknswoop 19]

Here's my thoughts on this and I would like to hear PD's.

The 106 would open in less altitude for several reasons. First off, a Javelin RS and a J7 both have the same size reserve PC's. They are lifting much different weights though. Same drag on PC with 1/2 the weight means it is going to come out of the free bag a lot sooner. Shorter lines also means it will come out of the bag sooner. Tandem reserve deployments take forever for the canopy to come out of the free bag. As for altitude to inflate after coming out of the free bag, even if the 218 slows the jumper down quicker, it won't be enough to catch up to the 106 that got out of the free bag long before the 218.

With all that being said, don't get a smaller reserve because it can deploy faster.

Derek

[mjosparky 4]

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Here's my thoughts on this and I would like to hear PD's.

The 106 would open in less altitude for several reasons. First off, a Javelin RS and a J7 both have the same size reserve PC's. They are lifting much different weights though. Same drag on PC with 1/2 the weight means it is going to come out of the free bag a lot sooner. Shorter lines also means it will come out of the bag sooner. Tandem reserve deployments take forever for the canopy to come out of the free bag. As for altitude to inflate after coming out of the free bag, even if the 218 slows the jumper down quicker, it won't be enough to catch up to the 106 that got out of the free bag long before the 218.

With all that being said, don't get a smaller reserve because it can deploy faster.

Derek

Derek,

You may be right on this and several of the other posts have some good points. But in the final analysis, whichever one is faster how many skydivers have access to the equipment that can measure the difference.

If your main is bad, make that decision quickly, get rid of it and pull the damn reserve.

Sparky

My idea of a fair fight is clubbing baby seals

[EvilLurker 2]

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As for altitude to inflate after coming out of the free bag, even if the 218 slows the jumper down quicker, it won't be enough to catch up to the 106 that got out of the free bag long before the 218.

That's where we disagree, as I don't believe the 106 will be out of the bag "long before" the 218, and the difference in drag while they are both reefed by the slider (deceleration before inflation stage) will be very significant. I'd sure like to see some actual data, though, I might end up eating crow.

[Hooknswoop 19]

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That's where we disagree, as I don't believe the 106 will be out of the bag "long before" the 218, and the difference in drag while they are both reefed by the slider (deceleration before inflation stage) will be very significant. I'd sure like to see some actual data, though, I might end up eating crow.

I had 2 reserve rides within a week or two of each other. Both were on Javelins. One was a MR-109-M and the other was a Fury 220R. There was a large difference in the amount of time it took before the 220 came out of the freebag vs. the 109. The tandem reserve rides I've had took a long time for the reserve to come out of the bag.

I too would like to hear from PD or someone else with hard data to see how my experiences compare.

Derek