Why 7-cell?

[Broke 0]

I was looking at the pictures in this months parachutist, and there was an article about the CRW camp in Mass. As I was looking at the pics I noticed that all the canopies were 7-cell canopies.

Is there a particular reason that 7-cell is preffered to 9-cell?

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[BillyVance 34]

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I was looking at the pictures in this months parachutist, and there was an article about the CRW camp in Mass. As I was looking at the pics I noticed that all the canopies were 7-cell canopies.

Is there a particular reason that 7-cell is preffered to 9-cell?

All the canopies in those pictures are PD Lightnings, CRW-specific canopies.

7 cells are more stable than 9 cells. I'm too tired to get into the specifics so someone else can do that.

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[relyon 0]

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I was looking at the pictures in this months parachutist, and there was an article about the CRW camp in Mass. As I was looking at the pics I noticed that all the canopies were 7-cell canopies.

Is there a particular reason that 7-cell is preffered to 9-cell?

Primarily because of the difference in the aspect ratios, where a 7-cell's is typically lower than a 9-cell's. In general, the higher the aspect ratio, the faster a canopy reacts in the case of an unintended turn (i.e. no toggle input). Such turns can develop either slowly, at an acceptable speed, or very fast, depending primarily on the aspect ratio and to a lesser degree on a few other design parameters.

Unintended turns can happen with offset docks when an end cell encounters the body burble of the person receiving the dock. It can also happen in the aftermath of a more aggresive dock if there is collapsing/collapsed end cell.

As far as the canopies shown in the article pics, they are all PD Lightnings. The camp was in preparation for the upcoming CF world record attemps this Nov.

'skies,

Bob

[homer 0]

WOW! Am I the only CRW dog who has absolutely no clue what you just said? (Takes another gulp of wine) I wish I had seen this months Parachutist but for some reason USPA never sends me a Sept. issue.

Quick hijack- How is Bob Lyons doing since his accident? I'd call him but his number got deleted from my phone.

CSA #699 Muff #3804

[BillyVance 34]

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Quick hijack- How is Bob Lyons doing since his accident? I'd call him but his number got deleted from my phone.

Didn't you just respond to his post?

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[relyon 0]

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WOW! Am I the only CRW dog who has absolutely no clue what you just said? (Takes another gulp of wine) ...

The aspect ratio of a wing surface (eg. a canopy) is how long and skinny the width (the span) is compared to its depth (the chord). 9-cells tend to generally be longer/skinnier than 7-cells. The calculation gets more involved for non-rectangular planforms (eg. an elliptical), but the idea is the same.

Canopies that are long and skinny in general turn faster than ones that aren't, so they tend to wrap faster and easier. They also tend to reinflate slower after a [partial] collapse. Both are usually undesireable qualities in a CRW canopy. That's a big reason I'm decidedly not a fan of so-called HP CRW, particularly when those doing it have little to no CRW training to begin with.

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Quick hijack- How is Bob Lyon doing since his accident? I'd call him but his number got deleted from my phone.

I'm doing pretty good all things considered, and hope to complete a full recovery by the Dec - Jan timeframe. Thanks for asking.

'skies,

Bob