Line Twist, Spinning Mal, & Wingloading

[Megatron 0]

How do these 3 factors interplay?

From what I understand at this point, higher wingloadings make line twist a more dangerous malfunction by turning it into a spinner.
Is this correct? If so, at what WL does this become significant?

Ive had line twist 4 times already and so far its been little more than an inconvenience. The first two were on student canopies and I arguably could have landed it twisted with a good PLF (assuming I didnt have to steer). The last two were at a 1.2WL and initially showed some tendency to dive but quickly stabilized.

I want to avoid any parachute with WL that requires a cutaway after line twist since I'm near certain it will happen again.

[AggieDave 6]

I nearly spun in after loosing altitude awareness 6-7 years ago on a 170 Heatwave loaded 1.7:1. This past year I chunked my Velo 111 loaded at nearly 2.6:1 due to linetwists. I felt the bag come off my back weird, looked up to 3-4 twists with slightly uneven risers. By the time I got my hands up to my risers to level the lines, I was already on my back and made a rotation. I was able to get my cutaway pulled by about the second to third rotation. It was exceptionally violent.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[c10edges 0]

are you really loaded 1.32 at 70ish jumps???

[Megatron 0]

yes, its no fun unless I PLF

[DSE 3]

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I want to avoid any parachute with WL that requires a cutaway after line twist since I'm near certain it will happen again.

You may wish to reconsider if skydiving is for you. You may also wish to reconsider a moderate to high wingloading for a longer while.

[erdnarob 1]

As other people tell you, if you have (at 70 jumps) to do a PLF in order to land your parachute, you have a problem. I would suggest you to take some canopy piloting lessons. OTOH don't you think that if you still need to do PLF that your canopy doesn't provide you enough support ? Or are you jumping in Colorado at very high elevation ? Or is your canopy made of F111, has thousands of jumps and became like a huge strainer...?
I like the idea that a fellow like you demonstrate interest in skydiving equipment but at your level, you should maybe concentrate more on the basics like using the proper canopy and mastering your landing.

Learn from others mistakes, you will never live long enough to make them all.

[Megatron 0]

I was just being sarcastic. Truth be told I have rarely had to PLF. Without getting ahead of myself I think I'm quite proficient in my piloting skills given my level of experience. I'm set to take a canopy course in the coming weeks as well.
There are many things which, while I understand superficially, I dont really get fully. Line twist being a good example...it seems that, as Dave's experience shows, that line twist becomes a more aggressive malfunction with higher wingloading, but why?
btw, is there I book I can get that goes into alot of this kinda stuff in detail...rigging & such?

[Gato 0]

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line twist becomes a more aggressive malfunction with higher wingloading, but why?

I have less experience than you do, but my understanding is this:

As mains (and reserves) get smaller, lines get shorter, and the whole thing gets closer (proportionally) to being around the same size as your body. Think about drag and G-forces. At that point, you're also flying considerably faster than you would on a larger wing, so EVERYTHING happens faster and possibly more intensely.

I was told this is partly why a 1:2 WL on a 190 is considerably different than a 1:2 on a 150.

Having said all that, I am a noob, and I don't know shit - other than that I know for a fact that I don't want my fat ass flying around on a 150!!

T.I.N.S.

[Pulse 0]

Gato is right about everything happening faster. Also, smaller canopies are more responsive to harness input. On a larger canopy, if you have line-twists and your risers are a little uneven, this won't be as big of an issue as on a smaller canopy.

If you can keep your risers even on during line-twists with a high wing loading you still won't spin. But if you start shifting in your harness when kicking out you will start spinning.

It's very simple. If you don't like the idea of cutting away. I would REALLY take a second look at whether or not this sport is for you.

"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

[Reginald 0]

I had spinning, diving line twists that required a cut away on a 1.1 loaded Sabre2 , 190. The G forces were so strong after just a revolution or two that it was hard to cutaway. It can happen on any canopy any time. BTW, you are already past that WL at far less experience.

"We've been looking for the enemy for some time now. We've finally found him. We're surrounded. That simplifies things." CP

[gearless_chris 1]

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I had spinning, diving line twists that required a cut away on a 1.1 loaded Sabre2 , 190. The G forces were so strong after just a revolution or two that it was hard to cutaway. It can happen on any canopy any time. BTW, you are already past that WL at far less experience.

The only time I had to use both hands to cutaway was on my 215 Monarch loaded at 1.1, it was a brake fire. All you have to do is get the risers uneven with linetwists and you're going to have some problems.

"If it wasn't easy stupid people couldn't do it", Duane.

My momma said I could be anything I wanted when I grew up, so I became an a$$hole.

[JohanW 0]

Wingloading helps to turn diving twists into a spinning mal. But planform is a major factor as well.

You really want to avoid the more radical elliptical designs just yet.

I have insufficient experience with Sabres 2 to unrecommend them on the basis of being elliptical, turn-happy, dive-happy suicide machines. I do feel they have a recovery arc that is longer than would be appropriate for you at this time.

I (heart) Silhouettes myself for people with your amount of experience (including myself at that time); something like a 210 sounds about right for you. Your friendly online canopy nazi (who has never seen you jump maybe a 210 for you ATM.)

Johan.
I am. I think.

[erdnarob 1]

<<>>

Some physics here: Spinning comes from a non symetrical open canopy behaving more or less like a the blades of a windmill. More load leads to more speed then to faster spin.

Now: faster spin for smaller canopies : The resisting torque (tendency to stay straight) is less important for small canopies since their mass and aerodynamical resistance due to the fabric is less far away with respect to the centre of rotation or spin. It's like a small farmer water pumping wind turbine spinning way faster than a 400 feet high wind turbine both under the same wind conditions. Do you get it? No book on parachute equipment really explains that but taking a physics course would. Physics when well understood makes you see things differently. You know more about why things happen.

Learn from others mistakes, you will never live long enough to make them all.

[BrianSGermain 1]

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How do these 3 factors interplay?

From what I understand at this point, higher wingloadings make line twist a more dangerous malfunction by turning it into a spinner.
Is this correct? If so, at what WL does this become significant?

Ive had line twist 4 times already and so far its been little more than an inconvenience. The first two were on student canopies and I arguably could have landed it twisted with a good PLF (assuming I didnt have to steer). The last two were at a 1.2WL and initially showed some tendency to dive but quickly stabilized.

I want to avoid any parachute with WL that requires a cutaway after line twist since I'm near certain it will happen again.

Wingloading is but on contributing factor in the way in which a parachute responds to line twists, and it is not the most significant. The degree and shape of the elliptical taper is also very important (more taper is more likely to spin).

Symmetry of the harness (body position is also very important. If we remain symmetrical during the initial snatch, and do not try to counter a turn with weight-shift during the initial inflation, we will experience far fewer line-twists.

Getting line-twists is not the end of the world. It is just something that happens now and then. It is true that some parachutes are more prone to spin than others, but that doesn't have to result in a cutaway.

The first step toward prevention of regular chopping is to pull high enough to fix the problem. I still pull at 3000 at the lowest.

The second is to go with the flow, and stay in the middle of the harness. It is bigger than you are, let it do it's thing, and when the lines get tight, give decisive action to point it where you want to go.

The third is to pack well. That is a long answer that many people can help you with.

Another thing is to have your gear set up correctly to inhibit line-twists. Good pilot chutes, long bridles and reasonable fit in the container can all make a big difference in your malfunction rate.

There is more, but I did want to chime in and put my 2 cents in.

Peace out!
Brian
PS Here is a link to an interesting (although unrecommended) solution to line-twists:
http://www.youtube.com/watch?v=-17AHJQQ8fA&feature=channel_page

Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

[Jeffwxyz 0]

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<<>>

Now: faster spin for smaller canopies : The resisting torque (tendency to stay straight) is less important for small canopies since their mass and aerodynamical resistance due to the fabric is less far away with respect to the centre of rotation or spin. It's like a small farmer water pumping wind turbine spinning way faster than a 400 feet high wind turbine both under the same wind conditions. Do you get it? No book on parachute equipment really explains that but taking a physics course would. Physics when well understood makes you see things differently. You know more about why things happen.

The term I think that you are really looking for is called "Conservation of Angular Momentum".

You can use a couple of analogies:

1. Think of the canopy and jumper as a clock pendulum. If you slide the pendulum weight up the rod, the pendulum will swing faster. This is the same as having shorter lines on a smaller canopy that affects the Pitch angle.

2. Think of an ice skater that trys to spin in place. They have to draw in their arms to spin fast. They are moving in mass toward the center of the spin axis. This causes the rotation to speed up. This is the same as having line twists on a small canopy with short lines. Your body is closer to the canopy, which puts most of the mass closer to the central axis. This again causes the rapid as opposed to slower spinning.

Correct me it I am wrong:
The OP was asking if there was a specific canopy size where twists causes bad spinning. I would say that there is no specific point of canopy size where this goes from acceptable to bad. I am sure that this has to do with the weight of the jumper (more or less mass) and what the tolerance level of the jumper is.