Canopy performance by w8 or size?

[mindcool 0]

Hello
I have right now 80 jumps and i just reached the phase that every skydiver is in......My first rig.
usually people jump and try all canopies sizes before they decide which one to buy...
my problem is that i'm a skinny guy that weight only 110 pounds and for a first canopy i wanna choose something that i'll wingload 1:1.
but i'm still not ready for a hight perforamce canopy...
so my question is:
if i'll buy a 120sqf canopy for beginners, do i need special skills to fly that?
i know that there are charts for every canopy.
so where can i find if i have enough skills to : Hornet , spectre, sabre/2 , trihatalon, cobalt, etc...
is it really the small size or only the wingloadding?

[skybytch 273]

Smaller canopies react faster to control inputs than do larger canopies due to shorter line lengths.
What's the smallest main you've jumped? Do you do primarily RW or freeflying? If you do RW, how much weight do you wear on a regular basis? Based solely on your body weight and the fact that this will be your first rig I'd suggest a 135 sq ft main - any of the ones you mentioned with the possible exception of the Cobalt would be great - the Cobalt is a very high performance canopy imho.
pull & flare,
lisa

[alan 1]

Please read this article, you should find it very helpful and informative.
http://www.performancedesigns.com/docs/wingload.pdf
alan

[Milo 0]

Wow, that is a nice article!
I'm a newbie lightweight jumper as well.
After we graduated off of student status myself and a significantly heavier jumper were seeking advice for our first rigs.
I listened as they reccomended canopies loaded at 1:1 or 1.1:1 for him and as they reccomended canopies loaded at .8:1 or .9:1 for me.
I trusted their experience, but secretly felt it was a criticsm of my flying skills.
This article puts down in words what my JMs knew from experience, and will be a nice addition to the bulletin board at the dz.
Milo

[drenaline 0]

Judge your skills if you are good flaring and have good canopy control then I think you can get a 1:1 wingloading with no problem, my first canopy I load it at 1.13:1 and at first I had trouble judging the flare but it went ok. The model I got was a Spectre 150, reasons: smooth opening (the one i was jumping before was a PD 230, big transition), easy to pack and cause of the wing load it will last me for a lot of jumps before I downsize again. If you are still doubting your skills, ask somebody (jumpmaster, instructors, etc.) to watch your canopy control and judge your skills, and check the reviews on the different canopies so you know what you are getting is what you want.
"Life is full of danger, so why be afraid? be extreme"
drenaline

[crazy 0]

Very interesting article indeed. I would have probably understood a bit more if i knew the definition of "responsiveness" and if i could figure out the meaning of "the physical and aerodynamic laws don't scale with the parachute". So, is there anybody on this forum to give me additional pointers, or even better, to help me to solve the following problem.
Consider two jumpers (SG is light, FB is twice heavier) jumping at the exact same loading, two canopies perfectly scaled (including lines and command lines).
I understand that a toggle input at shoulders level is actually a deeper input for SG than for FB, because the risers are the same length. Similarly, i understand that if both bury a toggle all the way down to full arm extension, SG has a deeper input because the length of the arms is not proportional to the weight. But, if both have proportionally the same input, let's say SG pulls a toggle 2 feet down, while FB pulls a toggle 4 feet down, what happens?
Who's canopy will bank more?
Who will have the higher maximum turning rate?
Who will dive more?
Who will feel the most airspeed?
Who will feel the strongest acceleration?
For me it's quite hard to believe blindly that the answer is SG for all questions. So, as a first approximation, i assumed that both canopies would bank the same and then i drew a few diagrams. I was obviously wrong because my conclusions were quite different from John LeBlanc's statements. So, can anybody explain?
Blue ones
Come

[rmsmith 1]

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I would have probably understood a bit more if i knew the definition of "responsiveness" and if i could figure out the meaning of "the physical and aerodynamic laws don't scale with the parachute".

At your local university, skip past the "scantron-classes" where everyone is a winner. Once you have finished the calculus, differential equations, and physics courses you will be able to take statics, dynamics and fluid mechanics, which will give you a better feel for the world around you and your favorite sport too.
In a nutshell, the heavier jumper will always be "sluggish" due to the additional mass that must swing to the side or front of the canopy during control inputs. Think about two automobiles of different weight and how they might perform; i.e., in a corner, braking distance, and acceration. The heavier automobile will require more traction, bigger brakes, and more horsepower, respectively. Even if they find more powerful racing horses you'll never see a bigger jockey!

[alan 1]

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I would have probably understood a bit more if i knew the definition of "responsiveness"

My best guess is that when John wrote the seminar, he was giving skydivers credit for some intuitive knowledge of how the meaning of responsiveness applies to canopy flight characteristics, especially given the context of his seminar. Additionally, when he presents the seminar, participants have the opportunity to ask the question you just did. I don't think a precise scientific definition is needed or useful. Essentially, responsiveness is how a canopy responds to the variety of control inputs it may be subjected to, which include range and rate, both as inputs and responses.

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and if i could figure out the meaning of "the physical and aerodynamic laws don't scale with the parachute". So, is there anybody on this forum to give me additional pointers, or even better, to help me to solve the following problem.
Consider two jumpers (SG is light, FB is twice heavier) jumping at the exact same loading, two canopies perfectly scaled (including lines and command lines).

Here is the source part of your misunderstanding. The canopies do not scale exactly in the real world. The canopy fabric does not scale, meaning and 89 ft2 canopy uses the same fabric that a 220 ft2 canopy uses. The lines do not scale exactly because an 89 ft2 canopy may use the same Vectran lines found on a 169 ft2 canopy. The seams in the fabric do not scale, etc.. It seems to me like you have theoretical questions that have no real world application.....as least for all practical purposes.

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For me it's quite hard to believe blindly that the answer is SG for all questions.

That is healthy. I'd be willing to bet that if you contacted the author of the seminar, he'd be very willing to answer your questions and defend his conclusions. Maybe you could then share that with us.

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So, as a first approximation, i assumed that both canopies would bank the same and then i drew a few diagrams.

On what do you base this assumption?

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I was obviously wrong because my conclusions were quite different from John LeBlanc's statements.

Your conclusions don't have to be wrong because they were different from John's. It is possible that yours are correct and his are in error. It would be nice if you were to share your conclusions with John and give him the opportunity to defend his. You might both learn something from such an exchange and if it was shared with the rest of us, we could all have the opportunity to learn and benefit. I know firsthand that John takes a student mindset to skydiving and is always open to learning.
alan

[crazy 0]

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In reply to:
> So, as a first approximation, i assumed that both canopies would
> bank the same and then i drew a few diagrams.
On what do you base this assumption?

I assumed that both canopies with the same proportional input have the same proportional distortion. At the steady state, assuming that the lift/drag coefficients are the same, the same force diagram applies to both. Scaling the diagram doesn't change the angles.
I agree with the fact that the seams, the thickness of the fabrick and the lines don't scale. This might give a lower lift/drag coefficient for the smaller canopy, which might make the smaller canopy dive more. But i have good reasons to think that this can be neglected as a first approximation.
BTW, i said an input of 2 feet for the small canopy and 4 feet for the big one. I meant 2.8 feet for the big one (the area increases with the square of the scale factor)

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It would be nice if you were to share your conclusions with John and give him the opportunity to defend his. You might both learn something from such an exchange and if it was shared with the rest of us, we could all have the opportunity to learn and benefit. I know firsthand that John takes a student mindset to skydiving and is always open to learning.

I would really enjoy to have the opportunity to tolk with somebody as knowledgeable as him. However, before wasting his time with my questions i want to be sure that i'm able to understand. These people's time is much better used designing canopies than explaining basic flight dynamics to ignoramuses

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[alan 1]

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I assumed that both canopies with the same proportional input have the same proportional distortion. At the steady state, assuming that the lift/drag coefficients are the same, the same force diagram applies to both. Scaling the diagram doesn't change the angles.

I might be wrong, but when you scale the diagram you introduce an error if you scale the lengths of the suspension lines.
It is too bad you won't take the time to e-mail John. I am sure that you would be surprised at how willing he would be to respond to you and how in depth and detailed his response would be.
alan

[PhreeZone 20]

Call John.... He's one of the coolest people when it comes to answering questions like this. His siminars are not to be missed if you attend one. I learned so much during the one at Lake Wales over Christmas and he answered some questions from AFF students up to 3000+ jump jumpers. Call him.... you won't be sorry.... he loves talking Shop more then mostt of us I think...
"Hey.. Its my camera, and my remote... I'll rewind if I want to!" ~ Goat #2

[crazy 0]

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I might be wrong, but when you scale the diagram you introduce an error if you scale the lengths of the suspension lines.

If i assume that the weight of the canopy (and the lines) is negligible, i think that the length of the lines don't affect the banking angle (still at the steady state).
However, the length of the lines will affect the time required to reach the steady state. It will affect the radius of the turn as well (but not that much).
Anyway, you convinced me, i'll ask directly John LeBlanc. I'll post a summary of the discussion on the forum.
Come