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Sky_doggy

Why are canopies of 150 square feet considered high performance?

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Hi,

Could someone help me understand why canopies of 150 square feet or less are deemed high performance?

There is currently a thread titled Perris “11/29/2014” that has drifted onto discussions about smaller canopy sizes for lighter people being considered high performance even if the canopy is lightly loaded.

Let me frame the question. I understand that there are design factors such as elliptical, recovery arc's, pitch angle, riser pressure and so forth that go into a canopy for swooping or other high performance activities but my question is around more benign canopies such as the Pulse and Pilot in smaller sizes.

If for example someone is jumping a Pilot 150 that is loaded at 1 to 1 or less they are considered to be flying a high performance canopy. When I have asked about this I have been told that it is because the lines are shorter but I don't understand this statement. Surely everything in is proportion, that is to say that the length of the lines would proportionally the same in relation to the canopy area.

I'd appreciate if someone could help me with the rationale behind this.

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Not everything scales the same when you go smaller, and things still happen faster. Think of a full size airplane flying, then a model of the same plane. Even with the same scale dimensions and weights, stuff happens a lot faster in the model. Full size plane takes 20+ seconds to take off, while the model takes 5... That's the best analogy I can provide.

As far as the rule being 150 sqft, I would say its considered a general consensus that most canopy pilots need to be proficient in their abilities in order to fly such a canopy.

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shift

Not everything scales the same when you go smaller, and things still happen faster. Think of a full size airplane flying, then a model of the same plane. Even with the same scale dimensions and weights, stuff happens a lot faster in the model. Full size plane takes 20+ seconds to take off, while the model takes 5... That's the best analogy I can provide.



It's a wrong analogy though, generally speaking RC models and full scale aircraft only have the look in common, and some very general ideas of control surfaces etc.
Weight distribution, power to weight ratio, internal structure, aerodynamic design etc are two completely different beasts and are not scaled.
It's like comparing an RC car with a real car because they look alike, they have completely different constructions and performances.

I like the drag explanation.

I also think it's a matter of aspect ratio, which - if I recall right - it's the ratio between the canopy width and the lines length. As canopy decrease in size, this number also increase and, if you try to visualize, shorter lines in proportion means that a smaller input (i.e. still giving 5 inches of brakes) will produce faster outputs, deeper rotations, etc. So the same small mistake with an input on a big canopy with low aspect ratio will be less noticeable than the same amount of error in a smaller canopy.

Also, as the relative size decreases, you get closer to the canopy and, you being the suspended weight, like a pendulum system your overall inertia decreases, which means, again, rotation becomes faster and the whole system is less stable (which means more performance in a turn but also harder and slower to naturally recover stability and straight flight out of it).
Try to visualize a weight suspended from the ceiling and a long rope, if you give it some impulse, the swing will be at a slow angular rate..
Now shorten the rope, for the same weight and the same impulse force, the swing, in terms of angular speed, will be much faster.

Not 100% sure, makes sense?
I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

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I have a video of myself at a 1.5 loading on a nitro 150 being left in the dust by my wife on her sabre 2 120 @ a 1:1.1 loading. The performance of a canopy is not linear with size. Graphically it's an exponential curve that represents loading to performance in respect to size. There is simply less air acting on a smaller canopy regardless of loading. Less drag, less lift, so the equilibrium settles out at a faster speed to keep the canopy's natural flight path consistent. There is simply less fabric, lines and weight there, so it will respond faster and feel twitchier than the same model at the same loading at a bigger size.
So say you went from a Canopy x 290 to a 210. You'll notice that change about as much as going from a 135 to a 120. Take a 15 square foot canopy and load it with 15 lbs and tell me how it flies. It's going to haul ass and be extremely sensitive.
I was that kid jumping out if his tree house with a bed sheet. My dad wouldn't let me use the ladder to try the roof...

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Sky_doggy

When I have asked about this I have been told that it is because the lines are shorter but I don't understand this statement. Surely everything in is proportion, that is to say that the length of the lines would proportionally the same in relation to the canopy area.



This is true, as far as it goes.

But the important thing about shorter lines is that they make things happen faster when you turn and roll. This is not just a proportional affect of wing loading - the center of mass of the whole vehicle, parachute and parachutist, is closer to the middle, and it's easier for it to rotate.

If you make a mistake on a small canopy, no matter how loaded, it takes less input (and less time) for it to become a big mistake with you pointed at the ground.
--
"I'll tell you how all skydivers are judged, . They are judged by the laws of physics." - kkeenan

"You jump out, pull the string and either live or die. What's there to be good at?

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It just comes from people being heavier and coz 150 is highly loaded for them then it must be for everyone lol i flown a 150 sabre im 60kg that shit is definitely not high performance even flying a sabre 135 still feels like the canopy is stoned compared to flying something like a stilleto of similar size
FTMC

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skez

It just comes from people being heavier and coz 150 is highly loaded for them then it must be for everyone lol



:S

Up to now, this had been an excellent and instructive thread.
But, I was wondering how many posts it would take before someone said something really dumb.
7 posts.

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Andy9o8

***It just comes from people being heavier and coz 150 is highly loaded for them then it must be for everyone lol



:S

Up to now, this had been an excellent and instructive thread.
But, I was wondering how many posts it would take before someone said something really dumb.
7 posts.

I was stirring the pot a bit if u didn't notice lol...the rest is still relevant.....
FTMC

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mh. Wouldn't that also completely change the trim point and all other "characteristic" points of the canopy, i.e. sweet spot, neutral point, affect the neutral trim, glide ratio, pressure distribution, etc.

I think you could design a canopy "for small people with little experience" that is specifically meant to be smaller than normal but as docile as possible, maybe also playing of the "squareness" of it (i.e. making it more square than rectangular, so increasing the length of the X axis vs the Y axis), but it would need to be a design meant this way from the ground up, I don't think just sticking a longer set of lines on any canopy would be beneficial.

Maybe. At least that was the answer I gave to myself when I thought about it some time ago.
I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

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If you put longer lines on a small canopy, I believe it would spin up faster as the angle of the lines would be smaller.

I don't really know how to explain it, but... Imagine a board that's a foot long with four strings, one tied to each corner, each string also a foot long, with the lines pulled tight and going to another board about two inches wide.

Now imagine those same two boards, but with strings that are two feet long.

The set up with the longer strings will be easier to twist and you will be able to put more twist in before it gets to tight to twist anymore.

Not sure if that will make any sense to anyone except me, but I understand what I mean :)

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I remember watching a guy bust himself up on a paraplane ( an early square with really long lines) years ago. he came in flared too high rotated under the canopy. and at that point he was only a few feet off the ground.:Sthen went up thru the arch and stalled when he was level with the canopy and flat of his back . like 20 maybe 25 or 30 ft off the ground. and fell flat of his back crash[:/] he went to the hosp. brokenB|

i have on occasion been accused of pulling low . My response. Naw I wasn't low I'm just such a big guy I look closer than I really am .


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skez

the rest is still relevant



Not really.

Just because it still feels like it's asleep compared to a Stiletto of a similar size (to you) does not make it less high performance. It just means the Stiletto is even more high performance B|

I have friends who jump 80-foot crossbraced canopies (or smaller) loaded at 2.8 and even 3. This does not mean my Stiletto 135 loaded at "only" 1.8 is not a potentially vicious canopy or that I should ever treat it casually.

How many jumps you have skez, on what canopies? Not meaning to turn this into a dick measuring contest (I don't really have much experience either) - I am just curious as to what your background is; your opinion is not a common one and I'm interested in how you came by it.
--
"I'll tell you how all skydivers are judged, . They are judged by the laws of physics." - kkeenan

"You jump out, pull the string and either live or die. What's there to be good at?

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Jumps? Lol whats that gonna teach me....and nah im just sayin at my weight of fuck all my sabre 150 is very docile seriously...and i should mention its a sabre1 ......im no professional of any sort..is there any other light people under 60kg who have flown the original sabre in a 150? I would be interested to know what u thought of it

And my background is speedwing groundlaunching etc i learnt all my canopy stuff that way before i was ever a skydiver lol
Canopies range from stiletto 107 to raven 250.plus speedwing paragliders base canopies etc......
FTMC

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skez

my background is speedwing groundlaunching etc i learnt all my canopy stuff that way before i was ever a skydiver



As you will be aware with all that experience, speedwings fly differently to skydiving canopies. In some ways they're more high performance (high aspect ratio elliptical) but your GL experience beforehand can be a disadvantage too.

A speedwing does some things much better than a parachute... you can get out of some kinds of trouble on one that on a skydiving canopy are a dead end. People with that kind of muscle memory have had some interesting experiences.

I am sure you know this, but it's worth pointing out to people reading this thread in the future eh?
--
"I'll tell you how all skydivers are judged, . They are judged by the laws of physics." - kkeenan

"You jump out, pull the string and either live or die. What's there to be good at?

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Understood...and also i dont think sabre1s open to hard i was just stirring the pot..coz that's all anyone seems to believe haha
And yeh speedwings are very different...but a stilleto is close as it gets from what i have flown...definitely high performance...but just saying the old sabre1 is a very forgiving canopy when lightly loaded if u fuck up on that then u are doing something really stupid...if someone does dumb shit it doesnt matter what size the canopy is..the person who wrote this original forum post was asking about docile style 150 canopies at lighter wing loadings being high performance...for me there not.... the the sabre1 150 still handles like a mini base canopy..and i cant even stall it on toggles
FTMC

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I think the sensible way to start this discussion is to define exactly what "high performance" means, otherwise we are talking about something that is open to interpretation.

There are a number of things that, IMO, go into "high performance":

- high altitude lost in a turn
- high rate of turn
- steep glide angle
- high speed at full flight
- high stall speed

The above list is not exhaustive, but all the listed parameters make for a canopy that is less forgiving of mistakes and takes more skill & finesse to fly and land safely in all conditions and over a significant number of jumps.

Many of these parameters also increase with a decrease of canopy size. Therefore, for a given canopy model and jumper, a smaller wing will be higher performance.

Why 150sq ft?
That seems to me to be an arbitrary size because not all 150s will behave equally. For example, a Stiletto would have higher turn rate than a Sabre2 150, but would lose less altitude in a turn.

150 sq ft was probably chosen for the SIM as being canopy that the USPA don't want low experience jumpers using, regardless of their weight.
"The ground does not care who you are. It will always be tougher than the human behind the controls."

~ CanuckInUSA

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Di0

...
I also think it's a matter of aspect ratio, which - if I recall right - it's the ratio between the canopy width and the lines length. As canopy decrease in size, this number also increase and.....



Just to clarify that part. Aspect Ratio is the relationship between span and chord...line lenght has nothing to do. Something like this:

http://3.bp.blogspot.com/-YzSdnDA8SwM/UH6yGBoI2nI/AAAAAAAAAPc/GetwPVdPI6I/s1600/rwnew_2.gif
HISPA #93
DS #419.5


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yeyo

***...
I also think it's a matter of aspect ratio, which - if I recall right - it's the ratio between the canopy width and the lines length. As canopy decrease in size, this number also increase and.....



Just to clarify that part. Aspect Ratio is the relationship between span and chord...line lenght has nothing to do. Something like this:

http://3.bp.blogspot.com/-YzSdnDA8SwM/UH6yGBoI2nI/AAAAAAAAAPc/GetwPVdPI6I/s1600/rwnew_2.gif

I was just hoping he wasnt serious or miss typed lol aspect ratio is so basic..
FTMC

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A good analogy is that smaller canopies, regardless of wind loading are like having a short stroke on a gas pedal. When you turn you very quickly pick up speed.
"I encourage all awesome dangerous behavior." - Jeffro Fincher

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