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Wings-n-Things

downsize too much?? diminishing returns

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Is there a point when downsizing, that a heavy jumper gets diminishing returns on the wing loading? A point where their weight is too much for a canopy to glide effectively? I'm thinking there has to be. If a plane can be overloaded, why not a ram air parachute??? :|
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Yes there are, but then again, I think a lot of it is still evolving.

For instance, just 6 or 7 years ago to hear of a competitive swooper loading above 2.2 was crazy, but now common wingloadings are above 2.5 and some are above 3.0!

Flying technique has changed how pilots use the speed the canopy generates. I also believe that larger X-braced canopies can take and benefit from slightly higher wingloadings than the same canopy in a smaller size.

Now for open cell canopies, there is definitely a point that performance suffers. The top skin and canopy structure deforms under too much weight and it negatively effects how the canopy flies. For instance, I felt that the Sabre2 really tapered off above 1.7 and the Katana above 1.9. However, some people really like their Sabre2 and their Katana loaded higher than that.

JayMo has set distance records on wingloadings that were considered ludicrous shortly before!

EDIT:

I also think you can overload a canopy situationaly. For instance, loading above about 2.2 is really way too high for most normal skydiving. You end up flying through traffic much too fast. A slightly off heading opening has you going across the sky at literally twice the speed of other canopies while the brakes are still set.
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Yes there are, but then again, I think a lot of it is still evolving.

For instance, just 6 or 7 years ago to hear of a competitive swooper loading above 2.2 was crazy, but now common wingloadings are above 2.5 and some are above 3.0!

Flying technique has changed how pilots use the speed the canopy generates. I also believe that larger X-braced canopies can take and benefit from slightly higher wingloadings than the same canopy in a smaller size.

Now for open cell canopies, there is definitely a point that performance suffers. The top skin and canopy structure deforms under too much weight and it negatively effects how the canopy flies. For instance, I felt that the Sabre2 really tapered off above 1.7 and the Katana above 1.9. However, some people really like their Sabre2 and their Katana loaded higher than that.

JayMo has set distance records on wingloadings that were considered ludicrous shortly before!

EDIT:

I also think you can overload a canopy situationaly. For instance, loading above about 2.2 is really way too high for most normal skydiving. You end up flying through traffic much too fast. A slightly off heading opening has you going across the sky at literally twice the speed of other canopies while the brakes are still set.



OK. But I guess what I was getting at was mostly about swooping in and of itself. Is there a point where the weight negates the glide itself. I'm thinking about that guy who jumped a 35 sq ft canopy out at Perris. He landed it OK, and it was a record smallest canopy ever, but surely he would get more glide from a larger canopy.
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Luigi did that jump as a stunt and who knows, in 10 more years we may have another advancement in technology or skill set that brings about even smaller canopies being routinely jumped in competition.

Nick flies a 64 (or somewhere in that size) JVX for the speed event. Its amazing to watch him leaf through the exit at such a high rate of speed... (some of you will get it)
--"When I die, may I be surrounded by scattered chrome and burning gasoline."

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VC 71 - probably the most fun to fly canopy, and when you hit it the thing is amazing. loading 3.0

VC 79 - best all around canopy I currently own. has the speed of the 71 but a little stronger recovery arc allowing me to carry more speed more consistantly. loading 2.55-2.7

VC 90 - Fantastic on the water. accuracy, wingover's, freestyle, doesn't matter, just feels like you're riding on rails going across the water. and up here in Colorado it goes faaaarrr. loading 2.2 - 2.35

If i could only fly one canopy for competition and everyday jumping it would probably be a VC 84. i think i would be satisfied with the speed and its ability on the water.



This sounds like what I'm talking about. Larger canopies and lighter wing loadings bringing longer swoops. Larger may or may not fly as fast in the air, but it sure looks like it swoops further.
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Here's what I don't get:

You take a good canopy and load it up. Flies pretty good.

You load it up even more. Flies even better - COOL

You load it up even more. Now it's starting to get glitchy and weird.

You load it up even more. Now it's a piece of crap.


NOW - superloading.....


You load it up even MORE - ridiculously so - the performance smooths out and you get some more fun from it.


What nut actually thought "hey, I know the performance is turning to crap as I add on more lead.....BUT what if I just add a bunch more and let's see what happens????"

now that ranks right up there with the cavemen that figured out which berries were good and which were poisonous....:D

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This sounds like what I'm talking about. Larger canopies and lighter wing loadings bringing longer swoops. Larger may or may not fly as fast in the air, but it sure looks like it swoops further.



Yes, sometimes, but for the speed event it is not about distance it is abot speed, surprisingly.:P

Accuracy is also not about distance and lots of distance is really really bad in accuracy.

In speed events, if a canopy that is loaded at 3.0 gets through the 70m faster but then dies in its ass at 80m then it is still a better tool for that event.

Sometimes with a head wind the small canopies have an even better advantage, in tail wind a different story.

This is why competators have a quiver of weapons for competition.

Once you delve into the discipline it is much more technical than one would think...
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From what I can see in competition, there are two ways to go far in distance.

Small highly loaded wing (example sub 80 sqft @ 2.7+). Comes through the gate with lots of speed, has less overall drag than a larger wing and covers lots of ground very quickly in the first 3/4 of the total distance but then does not float or maintain as much lift at the end. I see a trend towards this now with the weight limits.

Larger highly loaded wing (example 96 -111 sqft @ 2.7). Requires the pilot to be over the weight limits without lead. Big guys basically. Comes in with less speed through the gate covers the first 3/4 slower but maintains the lift longer during the end of the swoop.

I think the smaller wings require better technique to maintain the speed. The returns diminish quicker due to technique rather than wing size, but past a certain size I'm sure the returns would tail off completely.
I have seen some quite sloppy turns go mega distance with a 18 stone pilot under it.

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If winds aloft are taken out of the scenario then the glide angle will not change with a change of w/l. The higher wingloading will derive a faster descent rate, a lower a slower DR. Now if you consider the winds aloft:
-A higher decent rate in strong headwinds will give you more of as forward glide angle
-A lower decent rate (lower w/l) will give you more of a glide angle with tailwinds.
But both of these are derived by how much time you are able to spend in the air, more time spend in a tailwind scenario then further the distance covered ( vs a higher w/l or decent rate).
Both of these calculations are based on your relationship to the ground.
Now, a/c have weight ristrctions because they have to take off within a certain perameters ( ie the runway infront of you, or land) they also have to maintain altitude and be able to climb. Canopies dont have to meet these. I dont think that comparing a/c weight limits and canopies is an "apple to apple comparision"...
To give a VERY general answer : IMHO with the canopies we have now it is around and above 3.0:1 WL
Actually reading back over you question I am a little confused. Are you talking about an increase of w/l dirived by an decrease of canopy size or by an increase of weight or both??
Hope this helps and hope to hear more!

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Good post!

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If winds aloft are taken out of the scenario then the glide angle will not change with a change of w/l. The higher wingloading will derive a faster descent rate, a lower a slower DR.



Ok this is close to what I was talking about. In this case you mean full glide, no brakes or front or rear risers. I can see how that could be true. I'd love to see the comparison from a GPS instrument.

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Now if you consider the winds aloft:
-A higher decent rate in strong headwinds will give you more of as forward glide angle
-A lower decent rate (lower w/l) will give you more of a glide angle with tailwinds.
But both of these are derived by how much time you are able to spend in the air, more time spend in a tailwind scenario then further the distance covered ( vs a higher w/l or decent rate).
Both of these calculations are based on your relationship to the ground.



Hmmm... There is an algebra equation in there. (Since I'm taking an algebra class, I guess I should get to work! ;) )

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Now, a/c have weight ristrctions because they have to take off within a certain perameters ( ie the runway infront of you, or land) they also have to maintain altitude and be able to climb. Canopies dont have to meet these. I dont think that comparing a/c weight limits and canopies is an "apple to apple comparision"...



True. But not if you compare the lift one would get in a swoop to an aircraft taking off. It seems like if the canopy is too overloaded it would barely plane at all and just put the jumper sliding across the ground.
Maybe it's not apples to apples but how about oranges to grapefruits? :P

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To give a VERY general answer : IMHO with the canopies we have now it is around and above 3.0:1 WL
Actually reading back over you question I am a little confused. Are you talking about an increase of w/l dirived by an decrease of canopy size or by an increase of weight or both??
Hope this helps and hope to hear more!



Both I think. It's just a ratio of weight to canopy size regardless of how it's acheived.
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Good post!

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If winds aloft are taken out of the scenario then the glide angle will not change with a change of w/l. The higher wingloading will derive a faster descent rate, a lower a slower DR.



Ok this is close to what I was talking about. In this case you mean full glide, no brakes or front or rear risers. I can see how that could be true. I'd love to see the comparison from a GPS instrument.

Yes I was reffering to full flight but the DR rate will naturally change with change of control input. Half barkes on a lighter loaded wing is still a lower DR then half brakes on a higher w/l wing.
Quote

Now if you consider the winds aloft:
-A higher decent rate in strong headwinds will give you more of as forward glide angle
-A lower decent rate (lower w/l) will give you more of a glide angle with tailwinds.
But both of these are derived by how much time you are able to spend in the air, more time spend in a tailwind scenario then further the distance covered ( vs a higher w/l or decent rate).
Both of these calculations are based on your relationship to the ground.



Hmmm... There is an algebra equation in there. (Since I'm taking an algebra class, I guess I should get to work! ;) )

Quote

Now, a/c have weight ristrctions because they have to take off within a certain perameters ( ie the runway infront of you, or land) they also have to maintain altitude and be able to climb. Canopies dont have to meet these. I dont think that comparing a/c weight limits and canopies is an "apple to apple comparision"...



True. But not if you compare the lift one would get in a swoop to an aircraft taking off. It seems like if the canopy is too overloaded it would barely plane at all and just put the jumper sliding across the ground.
Maybe it's not apples to apples but how about oranges to grapefruits? :P
True. I have never seen a cnapoy overloaded. I have landed a VX55 at around 3.5-4.0.After doing a 270 I was able to get some swoop out of it so...To answer your question I think it would have to be WAY up there for there to be NO lift available.
Think about this:
If Jaymo or whoever is able to get a 1000 ft swoop after hitting 5ft gates his glide ratio might not be what we think. It is for sure not a 200:1 glide ratio. Without having done his trun he would never get that energy and so we might have to consider the 1000 feet lost in the turn too..I am not sure If I am right or wrong.
SO after all of that the glide ratio is 1:1 ( pretty crappy).
Now if we take you your scenario of a highly loaded canopy, lerts say a 3.0: 1 WL.
If that personl starts their turn at 1000feet agl and then swoops 200 feet his GR is...1:0.20 ( shit I think that's right but I am not even sure about that math).

Quote

To give a VERY general answer : IMHO with the canopies we have now it is around and above 3.0:1 WL
Actually reading back over you question I am a little confused. Are you talking about an increase of w/l dirived by an decrease of canopy size or by an increase of weight or both??
Hope this helps and hope to hear more!



Both I think. It's just a ratio of weight to canopy size regardless of how it's acheived.

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Hi I think it is pretty clear why beyond a certain optimum wing loading there is a performance penalty.
That's because every wing has an optimum glide ratio at a certain lift coefficient (see pdf attached). Let's say you are doing a distance competition. your speed is given by the trim angle of the canopy and your weight mainly. so you can imagine now to change the size of your canopy to get at the maximum glide ratio: you are now at the best loading for your wing in terms of aerodynamic efficiency. Load it more, performance degrades.
That is why an airline plane climbs higher and higher during a flight, to compensate the weight decrease with density decrease (and therefore fly at the same CL with different weights): they want to fly at the best efficiency, set speed and save gas.
if you take the same canopy now, let's say a vengeance and you plot the figure I sent for different sizes, the curves will shift to the right as you decrease the size (square feet of the canopy), therefore the best glide ratio will be at a slightly higher CL. This is because of Reynolds number effects: but remember the graph is for the drag coefficient! There will be also an optimum size for the minimum drag when the CD is multiplied by the area to obtain the drag. Decrease the size even more (at constant wing loading) and you decrease performance. So for a pure distance performance, there is an optimum wing loading and an optimum size.

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I don't think it was so much over your head as it didn't make any sense.

1) Your speed (gate speed) in a distance run is not a function of trim angle. It is a function of weight, parasitic drag, and (of course) technique.

2) Best glide ratio is not affected by weight nor is it particularly relevant in a distance swoop which is predominately horizontal flight with continuous changes to angle of attack.

3) I believe cruising heights of airliners are subject to several considerations including stall speed, the speed of sound, and engine efficiency. I don't see the relevance to swooping.

4) The Reynolds Number predicts the likelihood of turbulent (versus laminar) airflow. I figure the Reynolds Number for a parachute never exceeds 6,000,000 (assuming a chord length of 6.5 feet and a maximum speed of 100mph). But what does this have to do with wing loading?

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