Canopy design questions

[flyinryan 0]

It seems like cross braced canopies are not as eliptical as say a Stiletto, but rather they depend on rigidity and trim to get their preformance. So why don't we se a canopy taking advantage of a high degree of taper, AND cross bracing. Basicly, why don't we see the cross braced Stilettos? Which brings me to another question. Is the short recovery arc of the Stiletto more a function of the line trim or the shape of the wing? Okay, enough questions for now.

BASE 853

[SkymonkeyONE 4]

These canopies exist, but until there is a big enough demand for them, or a lull in a manufacturer's sales, then they will not be brought out of prototype and into production. One example is Brian Germain's cross-braced airlock jig, and another is the Atair Onyx.

Chuck

[geanky 0]

Chuck;
have you flown an Onyx? If so how does it fly? Just some food for thought.

learn to fly in 3d

[SkymonkeyONE 4]

No, I didn't fly the original 95 we have because it needed some trim adjustment and besides, they were cutting the 9-cell crossbraced planform main anyway. I will have that main as soon as it gets lines on it.

Chuck

[flyinryan 0]

Jeeze Chuck, isn't a 95 kinda big ;) Don't you fly like a 65 or some rediculus size like that. Okay, so with these more tapered cross braced wings will we see thighter recovery arcs, or is the recovery arc more a function of trim? And since someone brought up the Onxy...right now it seems like the cobalt can be loaded higher than any other non cross braced canopy...is this pattern gonna hold for the Onyx? Is this canopy gonna be able to take a bigger load than say a VX or a Xaos 27?

BTW, these questions are purly academic at this point as I am very happy on my 170 and will probably not be going to a 150 for several hundred jumps. Just the engineer in me trying to figure out how stuff works.

BASE 853

[rmsmith 1]

First, I'm no expert on the subject.

I can tell you about several notable differences between the Crossfire and the Stiletto regarding line trim. The first thing I noticed was that with the Stiletto the pilot is hanging more in front toward the nose. The Stiletto's line trim cause the canopy to be smoothly arched over your head whereas the Crossfire has a differential trim causing the center portion of the canopy to be flatter overhead with the sides arched. I believe that the more tapered a canopy the more it will over-steer. As for the recovery arch, I don't know how they design that to happen, but it sure makes it easier to develop speed higher up giving the pilot time to get off the front risers and set-up for landing.

[cobaltdan 0]

there is a certain amount of play, but basically where you 'hang' under the canopy is a function of the airfoil chosen and its pressure distribution. the fx,vx,xaos and stilletto all use the same airfoil (the "pd" airfoil).

how much lift a design produces governs how you set its angle of attack. the amount of lift a design generates is governed by the airfoil and planform efficiency and drag (or lack there of, i.e. reducing spanwise distortion). planform and airfoil making the most difference.


must run to a meeting....

sincerely,

dan<><>

Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

[dskydave 0]

ever jump a 170 stilletto? then jump 120 stilletto?There are a lot of factors that determine recovry arc, line length is a major factor.170 lines are longer and keep you in a dive longer. i get better swoops from the 170,,,

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[cobaltdan 0]

"right now it seems like the cobalt can be loaded higher than any other non cross braced canopy...is this pattern gonna hold for the Onyx?"


yes, in fact this is one of the reasons we designed the onyx. not to make smaller sport canopies, but to make higher wingloaded military canopies.

in testing the ability to land a cobalt tapers off at 5:1. the onyx will definately extend that range.

sincerely,

dan<><>

Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

[rhino 0]

Have you jumped the crossfire2?

How would the competition cobalt compare??

Rhino

[ramon 0]

Not stirring the pot, but, I did jump a competition cobalt 120 (loaded about 1.9) Butz's green and Black one.
It was very nice. flat glide, soft risers, nice opening, easy to fly and swoop.

I could probably replace both my FX109 and vengeance 135 with one as it seemed to do the job of both (fly like a bigger one swoop like a smaller one) for when I don't want to jump the VX (good swooper poor skydiving canopy)

But that's just what I think.

"Revolution is an abrupt change in the form of misgovernment.", Ambrose Bierce.

[SkymonkeyONE 4]

The CC is a very nice canopy. I jump it in meets, for AFF, with my wingsuits, everything. I can't bitch; I did VERY well on tour with it last year. Still, I yearn for the next step.

Chuck
<><>swoop monkey

[rhino 0]

Ramon, SkymonkeyONE,

Have either of you jumped the crossfire2 to compare to the CC?

Rhino

[Yoshi 0]

I jusmped the cobal..not cc but the crossfire 2 was much more desireable to me...soft openings (way soft) I lov snivels though...very fast turns and the toggle stroke is very similar to the cobalt...the recovery arc is very long....quite noticeable difference from the crossfire 1...flare is awesome and powerful till the last drop and the risers were arguably softer than the cobalt...I was hammering 360/360's up top with not too much of a striegn, and I am not the built very big...
-yoshi
-my 2 cents the crossfire 2 will be my next canopy even though I had the 1 and had to have it relined with the mod and my buddy blew it up...

_________________________________________
this space for rent.

[PhreeZone 20]

Rhino, your also looking at canopies marketed at different segmants. Most top of the line swoopers are'nt looking for canopies that do a 360 toggle turn in 15 feet, they are looking for the capoy that has the best glide, recovery arc, riser pressure, speed building ablilities, things like that. A VX does'nt compare to a Stiletto because thay are marketed and designed for different jumpers. A Crossfire is a high proformace canopy for most recreational jumpers (with the experience) where the VX is'nt for most recreational people.

The people that like the Velocities, FX/VX, Xaos, CC's are'nt the ones that measure the proformace by how fast it turns or how many right left right riser turns they can do, they measue it by how long it swoops and how nicely it handles in the last 6 feet off the ground.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[rmsmith 1]

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...even though I had the 1 and had to have it relined with the mod and my buddy blew it up...

I'd like to hear more about this canopy. Thanks!

[Remster 30]

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ever jump a 170 stilletto? then jump 120 stilletto?There are a lot of factors that determine recovry arc, line length is a major factor.170 lines are longer and keep you in a dive longer. i get better swoops from the 170,,,

Dave,

you are comparing 2 canopies on which you made 2 major changes and attibuting the difference in flight only to one parameter......

Its well estasblished that AT THE SAME WINGLOAD, a smaller canopy will outperform a larger one of the same design.

On the comparaison you proposed, the line lenght did change, but there also was a more then significant change in wingload.

Remster

[ramon 0]

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Its well estasblished that AT THE SAME WINGLOAD, a smaller canopy will outperform a larger one of the same design.

On the comparaison you proposed, the line lenght did change, but there also was a more then significant change in wingload.

Depends on what you call out perform.
This has all been experienced by me and my friend Levin:
An FX 109 at 2.0 and an FX 74 at 2.0 perform differently. 74 dives from higher up, lighter riser pressure goes fast does not surf as far. the 109 has a shorter recover arc, will float in deep brakes much longer, is somewhat slower in the dive and in full flight, but will surf a further.

What is performance?

"Revolution is an abrupt change in the form of misgovernment.", Ambrose Bierce.

[SkymonkeyONE 4]

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Its well estasblished that AT THE SAME WINGLOAD, a smaller canopy will outperform a larger one of the same design.

Remi,
that depends entirely on your definition of "outperform". I can tell you that on tour, the opposite is true. This is why guys who would normally be able to get away with a (example here) are now jumping one or two sizes up and wearing weight to achieve nearly the same wingload. The larger wing will always give you a longer swoop at the same load. Perfect examples of this are Jay Moledski jumping his Velocity 84 all last year and ruling; and Eric Butts jumping a CC 120 and outswooping me at the same wingload in every meet last year. While the larger main may turn a tad slower, and be slightly slower through a PPPB speed course, it will shine in every other event.

Chuck
<><>swoop monkey

[Yoshi 0]

rmsmith,
well it was on the recall list for mandetory reline. I didnt have any substantial problems with it bucking or buffering in flight beforehand, but hey if the manufacturer says it needs done its done. when I got it back it flew much the same accept the front riser pressure was much harder...opened the same and all.. then while I was demoing a 119 my buddy jumped mine and blew the tail section out of the right end cell... he thought his leg strap was loose because of a turn when in full glide and since the tear was on the top skin he coulnt see it...landed with no problem then saw what he had done to my baby... I hav icarus repair it and now it flies the same with the exception of the soft openings...I am actually ROLLING THE NOSE ON MY CROSSFIRE! to get those 900 ft snivels I love so dearly:) anyways thats my story and I am sticking to it.. any other questions?
-yoshi

_________________________________________
this space for rent.

[rmsmith 1]

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...any other questions?
-yoshi

Thanks for the follow-up! I have two Crossfires, and one of them required the line trim modification. It opens much faster now, and I am going to buy a larger slider for it to get back those 800-ft snivels. It still flies and lands great otherwise, and yes, it does have higher front riser pressure too.

--rms

[RichM 0]

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in testing the ability to land a cobalt tapers off at 5:1. the onyx will definately extend that range.dan<><>

*cough* 5:1?? Thats big ballz

Rich M

[GroundZero 0]

cobaltdan claims: "but basically where you 'hang' under the canopy is a function of the airfoil chosen and its pressure distribution."

groundzero replies: the point where one "hangs" is determined by the designers lineset. Angles determined by the b and d cascades and their insertion point in the a and c lines will determine where the mass will be located under the airfoil, whether it be a "pd" airfoil, an atair airfoil or any other airfoil.

must run to play!

Chris xox

[markbaur 0]

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cobaltdan claims: "but basically where you 'hang' under the canopy is a function of the airfoil chosen and its pressure distribution."

groundzero replies: the point where one "hangs" is determined by the designers lineset.

Would it be correct to restate Dan's claim as, "The center of gravity hangs below the center of lift"?

And would it be correct to restate Chris's reply as, "The angle between the chord and the CG-CL line is determined by the line set"?

If both of these restatements are correct, then Dan's and Chris's claims are complementary, not contradictory. I'd be interested in hearing more.

Mark

[GroundZero 0]

It is important to note that the center of lift produced by the airfoil and the positioning of the center of load is what makes the pressures on the corresponding risers vary... ie higher or lower riser pressures... beyond that, performance of the canopy varies greatly with respect to where the load is placed in respect to the center of lift...

Differences can be seen in how long a canopy will remain in a dive (recovery arc), differences in riser pressures, differences in airfoil efficiency (how far it will surf), differences in neutral flight speed, and very importantly, differences in stability.

The lineset (among other things) determines the relationship between the center of lift and the positioned center of the load below. This is one of the many variables of canopy design.