Forums: Skydiving: Gear and Rigging:
(too) Lightly loaded

 


djro

Jun 8, 2011, 4:13 PM
Post #1 of 16 (1252 views)
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(too) Lightly loaded Can't Post

Is there a point where having a light wing loading becomes a problem where the only objective is a nice soft landing?


jrmrangers  (B 36060)

Jun 8, 2011, 4:26 PM
Post #2 of 16 (1232 views)
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Re: [djro] (too) Lightly loaded [In reply to] Can't Post

yup, when you start going backwards in the breeze its a bad thing!!


riggerrob  (D 14840)

Jun 8, 2011, 5:26 PM
Post #3 of 16 (1197 views)
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Re: [djro] (too) Lightly loaded [In reply to] Can't Post

When canopies are too-lightly loaded, they take forever to open and easily collapse in turbulence.

The flip side of that debate is that you will be descending so slowly that you will probably not notice a collapsed end cell on a lightly-loaded canopy (less than 0.6 pounds per square foot).

Keep in mind that minimum wing-loadings vary with canopy model.
... 0.6 pounds per square foot may be the minimum wing-loading for a student canopy.
OTOH that would be ridiculously-light loading for a Velocity which is designed to be loaded at 2 to 4 pounds per square foot.


Premier wmw999  (D 6296)

Jun 8, 2011, 5:55 PM
Post #4 of 16 (1180 views)
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Re: [riggerrob] (too) Lightly loaded [In reply to] Can't Post

BASE jumpers commonly expect their canopies to be loaded very, very lightly. But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width). Lots of room for the air to rush in.

You can end up going backwards in lower winds than other people; of course, you'll still be way better than people used to be jumping rounds 40 years ago. Trust me on this -- I jumped rounds for a long time, as well as more than one low aspect ratio 7-cells loaded at under .7.

Wendy P.


AggieDave  (D License)

Jun 8, 2011, 6:38 PM
Post #5 of 16 (1149 views)
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Re: [wmw999] (too) Lightly loaded [In reply to] Can't Post

When you load in the .3 (or lower) range the canopy actually stops functioning as an air foil, there simply isn't enough weight to create enough airflow. Pulling the toggles may give a minor amount of heading control, but for all practical purposes you're under a funny shaped round.


DaVinciflies

Jun 8, 2011, 10:35 PM
Post #6 of 16 (1081 views)
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Re: [wmw999] (too) Lightly loaded [In reply to] Can't Post

In reply to:
But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width).

I may be wrong but I thought aspect ratio was related to chord vs span of the canopy and not height vs width of the cells.

Can someone confirm? One of us is severely misunderstanding the situation!


phoenixlpr  (D 3049)

Jun 8, 2011, 10:50 PM
Post #7 of 16 (1074 views)
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Re: [DaVinciflies] (too) Lightly loaded [In reply to] Can't Post

In reply to:
In reply to:
But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width).

I may be wrong but I thought aspect ratio was related to chord vs span of the canopy and not height vs width of the cells.

Can someone confirm? One of us is severely misunderstanding the situation!

Aspect ratio got some effect on openings and recovering from collapse. It does not have direct correlation with recommended minimum loading.


bqmassey  (Student)

Jun 8, 2011, 11:04 PM
Post #8 of 16 (1063 views)
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Re: [DaVinciflies] (too) Lightly loaded [In reply to] Can't Post

In reply to:
In reply to:
But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width).

I may be wrong but I thought aspect ratio was related to chord vs span of the canopy and not height vs width of the cells.

Can someone confirm? One of us is severely misunderstanding the situation!

You are correct, DaVinciflies.


popsjumper  (D 999999999)

Jun 9, 2011, 1:37 AM
Post #9 of 16 (1031 views)
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Re: [DaVinciflies] (too) Lightly loaded [In reply to] Can't Post

In reply to:
In reply to:
But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width).

I may be wrong but I thought aspect ratio was related to chord vs span of the canopy and not height vs width of the cells.

Can someone confirm? One of us is severely misunderstanding the situation!

Maybe she us saying the same thing just putting it into simple-to-understand terms for the OP?
How tall = Length nose-to-tail = Chord
Width = end cell-to-end cell = Span

Guessing here but it sounds right to me.

OTOH, maybe Wendy finally blew a big one all to hell and back! In which case, get video...it's going to be a cult classic.
LaughLaughLaugh


(This post was edited by popsjumper on Jun 9, 2011, 1:39 AM)


Erroll

Jun 9, 2011, 4:24 AM
Post #10 of 16 (995 views)
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Re: [DaVinciflies] (too) Lightly loaded [In reply to] Can't Post

In reply to:
In reply to:
But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width).

I may be wrong but I thought aspect ratio was related to chord vs span of the canopy and not height vs width of the cells.

Can someone confirm? One of us is severely misunderstanding the situation!

You and Wendy are both correct. Aspect ratio is the ratio between any two dimensions, eg. width and height. This can apply to wings, cells and even TV screens.


jerolim  (F License)

Jun 9, 2011, 4:41 AM
Post #11 of 16 (980 views)
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Re: [djro] (too) Lightly loaded [In reply to] Can't Post

I did a solo jump with tandem (410 sqft) canopy. It was part of tandem master training. I had a WL 0.365.
Opening was not much slower. It was a half and hour ride down, it felt like paraglider ride.


Premier wmw999  (D 6296)

Jun 9, 2011, 5:22 AM
Post #12 of 16 (953 views)
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Re: [popsjumper] (too) Lightly loaded [In reply to] Can't Post

I wasn't sure which it was, so I looked it up in Wikipedia Blush, under both "aspect ratio" and "parachute."

What I meant was "big tall cells"

Wendy P.


(This post was edited by wmw999 on Jun 9, 2011, 5:22 AM)


pchapman  (D 1014)

Jun 9, 2011, 5:22 AM
Post #13 of 16 (951 views)
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Re: [Erroll] (too) Lightly loaded [In reply to] Can't Post

In reply to:
Aspect ratio is the ratio between any two dimensions,

Techically that's basically right but it is wrong in the conversation here. In skydiving and aviation, there is only one basic definition of aspect ratio for a wing.

If you want to talk about some other aspect ratio, you'd have to be very specific that it is the aspect ratio of something else. (e.g., the aspect ratio of the cell openings)


Gary73  (D 21341)

Jun 9, 2011, 6:56 AM
Post #14 of 16 (902 views)
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Re: [DaVinciflies] (too) Lightly loaded [In reply to] Can't Post

In reply to:
In reply to:
But they jump 7-cells with low aspect ratios (i.e. how tall the cells are as compared with the width).

I may be wrong but I thought aspect ratio was related to chord vs span of the canopy and not height vs width of the cells.

Can someone confirm? One of us is severely misunderstanding the situation!

You are correct about aspect ratio, but since cells largely maintain the same proportions (height vs. width vs. length) regardless of size, adding cells generally increases the aspect ratio.


djro

Jun 9, 2011, 3:33 PM
Post #15 of 16 (758 views)
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Re: [jerolim] (too) Lightly loaded [In reply to] Can't Post

In reply to:
I did a solo jump with tandem (410 sqft) canopy. It was part of tandem master training. I had a WL 0.365.
Opening was not much slower. It was a half and hour ride down, it felt like paraglider ride.

Cool!


riggerrob  (D 14840)

Jun 11, 2011, 10:34 AM
Post #16 of 16 (635 views)
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Re: [wmw999] (too) Lightly loaded [In reply to] Can't Post

In reply to:
I wasn't sure which it was, so I looked it up in Wikipedia Blush, under both "aspect ratio" and "parachute."

What I meant was "big tall cells"

Wendy P.

.....................................................................

"big tall cells" is pronounced as "finesse ratio" by aeronautical engineers.
Finesse ratio defines the height of the airfoil (rib) compared with the chord.
IOW "How fat are the ribs?"

Thin ribs are only found in fast canopies, like Velocities. Since they go so fast, they are deflecting lots of air and only have to deflect all that air by a little bit to generate enough lift for landing. Canopy piloting competitors (aka. pond swoopers) routinely load their canopies at more than 2 pounds per square foot.

Medium thickness ribs are sewn into most mid-range canopies: student, tandem, sport mains, reserves, BASE and canopy formations.

Thick ribs are reserved for slow canopies. They need to deflect - what little - air a lot to generate enough lift for survivable landings. Remember that classic accuracy competition (precision landing) can involve stalling the canopy onto the target from as high as 30 feet (10 metres). When they are stalled, square canopies fly like small, awkward round canopies. The only way your ankles will survive classic accuracy landings is if you have LOTS of fabric overhead, say loading at 0.7 pounds per square foot.



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