7 Cell vs 9 Cell differences?

[Thanatos340 1]

What are the basic differences in flight characteristics between 7 Cell and 9 Cell Canopies? What advantages does on have over the over as a Main? I have read that a 7 cell will have a slightly smaller pack volume but is this at the expense of performance?

[skymick 0]

9 calls generally have better glide then a 7 cell as they have a higher aspect ratio which means less form drag (which is induced by the friction of the air against the skin of the canopy). They also tend to need less input so tend to react more aggresively then 7 cells. But due to the higher number of cells they tend to infalte more unevenly (takes more time to inflate the ends cells) and they do have a higher pack volumne becuase of the higher number of cells, which means more matieral.

OK for anyone who hasnt realised I just scabbed most of that from http://skydiveaz.com/resources/book_canopy.htm

so instead of trying to sound like I know what Im talking about ill just copy and paste some if it below...

The seven cell is more likely to open on heading, will pack slightly smaller for the same wing area, and is less vulnerable to malfunctions of a line-over type. In a partial malfunction situation, the seven cell will be less radical (have a slower descent rate and less violent behavior.)
A nine cell will have a flatter glide, giving it slightly more range. It will have a longer flare, which may make the flare easier to time but requires a longer runway.
The seven cell will be more stable at slow speeds, give more warning before stalling, and recover from a stall more predictably than a nine cell.
The nine cell may have more forward speed, an advantage in winds.

If anyone has'nt read the 'Book of Canopy Control' by Bryan Bourke go and read it..it is really interesting and helpful (the addy is above)

[darkwing 4]

I think this is a more complex question than you know. To really answer your question as to the INTRINSIC difference you would need two canopies that are identical, except that one is 7 and one is 9 cell. I don't think such things exist in the market.

Having said that, generally speaking, 9-cell canopies have a higher aspect ratio, which (once again, generally speaking) will automatically make them fly better (by today's most common definition of "better").

Now to really answer your question -- basically 9's have a flatter glide angle, and a better flare. If they have the same square footage (measured by the same method) the 9 will have more pack volume--due to seam and line bulk.

-- Jeff
My Skydiving History

[cobaltdan 0]

if you made 2 canopies identical in planform and airfoil, only difference being one was constructed from 7 cells and the other 9 cells:

the only difference would be the 9 cell would have a lower spanwise distortion on the top skin airfoil.

sincerely,

dan<><>
atair aerodynamics
www.extremefly.com

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

[skybytch 259]

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9-cell canopies have a higher aspect ratio, which (once again, generally speaking) will automatically make them fly better (by today's most common definition of "better").

"Better" is a relative term. Personally I think a 7 cell flies "better" than a 9 cell - by that I mean that I prefer the flight characteristics of a 7 cell over a 9 cell.

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9's have a flatter glide angle, and a better flare.

My Spectre flares better than the PD F111 9cell I used to jump. I think it has a better flare than the Sabres I've jumped. It certainly is easier to flare than the Safire I used to jump.

One is not better than the other... it depends on what a person wants out of their canopy.

7CP #2 representing.

[darkwing 4]

Dan, are you saying that there would be NO difference in flight characteristics as a consequence of the lower distortion? I don't disagree with your statement, but it seems to imply that there would be no diffs in flight characteristics, which I doubt you would say.

-- Jeff
My Skydiving History

[darkwing 4]

I don't think I am disagreeing with anyone above. Skybytch is comparing apples to oranges. Sure you can find examples of 7-cells that fly better (by some definitions) that some 9-cells. I was trying to make a point about intrinsic differences.

-- Jeff
My Skydiving History

[mjosparky 3]

Try this and read some of the articles.
http://www.performancedesigns.com/education.asp
Sorry I don't know how to make a clicky.
Sparky

My idea of a fair fight is clubbing baby seals

[Jimbo 0]

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the only difference would be the 9 cell would have a lower spanwise distortion on the top skin airfoil.

Dan, correct me if I'm wrong, but doesn't each cell generate X amount of lift? If you remove two of the lift generating cells aren't you going to have a canopy that doesn't glide as well as the 9 cell? The way I read your statement, it seems as if there's no need for the extra 2 cells on a 9 cell canopy.

Anyone with a better understanding of aerodynamics, I'd love to hear more on this.


-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[darkwing 4]

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Dan, correct me if I'm wrong, but doesn't each cell generate X amount of lift? If you remove two of the lift generating cells aren't you going to have a canopy that doesn't glide as well as the 9 cell? The way I read your statement, it seems as if there's no need for the extra 2 cells on a 9 cell canopy.

Anyone with a better understanding of aerodynamics, I'd love to hear more on this.
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Jim

I think we need to be very specific here. Your question implies to me that you mean simply removing two cells from a 9-cell canopy. I think Dan and I both mean otherwise identical, same span, chord, airfoil etc, so that each of the cells in the 7 cell canopy is wider than each in the 9 cell. Sorry if I am not interpreting Dan's comment correctly, but I am certain I am interpreting myself correctly.

-- Jeff
My Skydiving History

[Jimbo 0]

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I think Dan and I both mean otherwise identical, same span, chord, airfoil etc, so that each of the cells in the 7 cell canopy is wider than each in the 9 cell.

After reading Dan's post again, with your input, I think that you're probably right. Hopefully though, someone will come along and set us straight!

-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[mjosparky 3]

Lift is not a result of the number of cells but the effective area of the wing. A 300 sq. ft. canopy could have 22 cells or 9 cells and the lift area would be the same.

My idea of a fair fight is clubbing baby seals

[andrewstewart 0]

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I think this is a more complex question than you know. To really answer your question as to the INTRINSIC difference you would need two canopies that are identical, except that one is 7 and one is 9 cell. I don't think such things exist in the market.

Having said that, generally speaking, 9-cell canopies have a higher aspect ratio, which (once again, generally speaking) will automatically make them fly better (by today's most common definition of "better").

Now to really answer your question -- basically 9's have a flatter glide angle, and a better flare. If they have the same square footage (measured by the same method) the 9 will have more pack volume--due to seam and line bulk.

Actually a 7 cell will have a "better" flare than a 9 cell.

[Kris 0]

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Actually a 7 cell will have a "better" flare than a 9 cell.

Wha...? Care to clarify?

Sky, Muff Bro, Rodriguez Bro, and
Bastion of Purity and Innocence!™

[indyz 1]

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Actually a 7 cell will have a "better" flare than a 9 cell.

Really? The worst flare on any canopy that I've ever jumped was a 7 cell Lightning. I totally love the flare on a Lotus (9 cell). I think it's better than my Spectre (7 cell).

[mjosparky 3]

"Better" being a relative term, what facts do you base this statement on?

My idea of a fair fight is clubbing baby seals

[phoenixlpr 0]

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Really? The worst flare on any canopy that I've ever jumped was a 7 cell Lightning. I totally love the flare on a Lotus (9 cell). I think it's better than my Spectre (7 cell).

Stop compairing apples to perrys! Lighting is a CRW canopy. You should know the CRW canopys are not famous for good flare power, they trimmed differently.

[indyz 1]

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Stop compairing apples to perrys! Lighting is a CRW canopy. You should know the CRW canopys are not famous for good flare power, they trimmed differently.

I was just trying to point out that his generalization was totally bogus.

[phoenixlpr 0]

Why? You cn compare Sabre and Spectre.
They are in the same class, similar trim.....

[Kris 0]

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Why? You cn compare Sabre and Spectre.
They are in the same class, similar trim.....

Actually, the Stiletto is as close of a 9-cell equivalent as you're going to get to the Spectre. The Sabre & Spectre aren't even close.

Sky, Muff Bro, Rodriguez Bro, and
Bastion of Purity and Innocence!™

[vt1977 0]

I’d agree with that! I normally jump a Sabre 135 and before that a Sabre 150 and jumped a Spectre 135 for the first time yesterday. It felt very different to my Sabre 135 – heavier toggle pressure (probably closer to that on my Sabre 150), pretty comparable riser pressure (possibly slightly lighter front riser pressure?) but definitely faster turns. Beautiful openings and lovely flare and landings – but again the landing/flare felt slightly different to my Sabre. I think I liked it! Definitely confirmed my thought that my next canopy will be a Spectre 120!

Vicki

[b1jercat 0]

7 cell steeper glide angle, better for accuracy, single stage flare.
9cell flatter glide angle, two stage flare.
All the 7cell canopys I have jumped had a great flare
and I always felt like I could drop on a dime.
I jump a saber 2 9 cell canopy and it took me a few jumps to get the flare down and it has more forward speed.

blues

jerry

[ianmdrennan 2]

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7 cell steeper glide angle, better for accuracy, single stage flare.

umm...no. Spectres are 7 cells - no single stage flare, so are velocities and I definately don't single stage flare mine. Accuracy depends on the pilot, not the number of cells.

Blue skies
Ian

Performance Designs Factory Team