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# Air volume inside cells

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Is there any way to measure air volume inside the canopy cell ?
i need it for a scientific article .

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Aerodyne (at least) publishes volumes for each canopy size, although not by individual cells.

http://www.flyaerodyne.com/pilottech.asp

Short of measuring the cell dimensions (lxwxh), I don't know a better method.

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FYI: Those volumes are pack volumes.

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CrashProne

Aerodyne (at least) publishes volumes for each canopy size, although not by individual cells.

http://www.flyaerodyne.com/pilottech.asp

Short of measuring the cell dimensions (lxwxh), I don't know a better method.

I think those are pack volumes. As in what size main container should they fit into.

HxWxD won't work either, because they taper to the tail. You'd need approx area of the rib, x width of cell x chord of canopy. And the chord will vary from the middle cells to the outer cells on anything but a truly "square" canopy.
"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

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accumack

FYI: Those volumes are pack volumes.

Ah, that makes sense, brain fart.

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Hold the nose upright over a bathtub. Fill the cell with water one gallon at a time from a jug. Count the number of gallons. When full, convert gallons to cubic feet. Presto!

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How accurate do you really need it??

Looking for an approximation of air mass? It can be a few pounds I remember calculating for a typical canopy but more for a student canopy. (With the volume rapidly going up, by the power 3/2 vs area.)

Actually MEASURING the air volume is tough; calculating roughly what it would be is easier. I can't offer much beyond the obvious calculations:

For a rectangular canopy the volume as constructed would be just span * chord * height * a factor for the area of a rib compared to the rectangle it fits into. (Somewhere between .33 and .5 lets say). If one doesn't have access to any fancy techniques to integrate the area inside the curve, just estimating with a drawing over graph paper (physically or on the computer) will work.

One can either trace a rib of a canopy or find the occasional (sometimes rare) drawing of a canopy rib out there to get a typical shape.

Thickness to chord ratios vary but one could figure out estimates for different styles of canopies if one doesn't have a canopy to measure.

For tapered canopies, one can easily make linear adjustments as most canopies don't have a complex geometry like a paraglider.

If you want to estimate the change due to distortion when inflated, with shortened span and increased bulge between ribs, that'll take a little guesswork. Guess the volume would increase slightly as the shape becomes rounder. I have seen Icarus publish estimates on % span reduction but not on thickness changes.

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pchapman

...Actually MEASURING the air volume is tough; calculating roughly what it would be is easier. I can't offer much beyond the obvious calculations:

For a rectangular canopy the volume as constructed would be just span * chord * height * a factor for the area of a rib compared to the rectangle it fits into. (Somewhere between .33 and .5 lets say). If one doesn't have access to any fancy techniques to integrate the area inside the curve, just estimating with a drawing over graph paper (physically or on the computer) will work.

One can either trace a rib of a canopy or find the occasional (sometimes rare) drawing of a canopy rib out there to get a typical shape.

Thickness to chord ratios vary but one could figure out estimates for different styles of canopies if one doesn't have a canopy to measure...

Two thoughts on this:

If you have access to a canopy and a hanging rack, hang the canopy up and go up into a cell. Measure the height of the rib at a few points. Use that data to get a rough estimate of the area of the rib.

Send an e-mail to a few canopy manufacturers. Ask them. Tell them why you want the info. Keep in mind the ribs vary from canopy to canopy, and even more by size of canopy, so be specific.
No guarantees it will get a response, but certainly worth the effort if you want accurate info.
"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

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SgtDimitri

Hold the nose upright over a bathtub. Fill the cell with water one gallon at a time from a jug. Count the number of gallons. When full, convert gallons to cubic feet. Presto!

Don't use water. Use packing peanuts.
Always remember the brave children who died defending your right to bear arms. Freedom is not free.

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SgtDimitri

Hold the nose upright over a bathtub. Fill the cell with water one gallon at a time from a jug. Count the number of gallons. When full, convert gallons to cubic feet. Presto!

that could work if there are no pre-cut holes in the cell dividers, but I'd imagine filling one cell would get pretty damn heavy.

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nolhtairt

***Hold the nose upright over a bathtub. Fill the cell with water one gallon at a time from a jug. Count the number of gallons. When full, convert gallons to cubic feet. Presto!

that could work if there are no pre-cut holes in the cell dividers, but I'd imagine filling one cell would get pretty damn heavy.

I think he was joking...
-------------------------------------------------------

To absent friends

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Iran and ran and ran.

Volume per cell or total volume....

Remember you have some tapered/eliptical canopies.

Get dimensions from manufacturer, then it should be fairly simple, or get a blown up old canopy.

What would be interesting though, is air pressure. That wing gets rock solid in the air....
You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

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potatoman

What would be interesting though, is air pressure. That wing gets rock solid in the air....

Not really, as you may well know.

First time I did CRW and grabbed a canopy, I was shocked how easily the canopy moved under my hand, how a whisper of air held us aloft.

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Have you tried crew with high performance canopies?

Think there would be a serious pressure difference between low aspect 7 cell types, and high speed smaller ones.
You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

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potatoman

Have you tried crew with high performance canopies?

Think there would be a serious pressure difference between low aspect 7 cell types, and high speed smaller ones.

Twitchy handling, super thin lines? No thanks. I'll leave that to the kids.

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Yup, was a kid once too. Got some nice "tiger claw" rips through my jumpsuit.

Back to volume.
You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

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Search out info on Ozone XXXlite, Niviuk Skin, and Air Design UFO. All recent single surface paragliders. They talk about the volume of air they don't have and how that affects handling. Seen specific numbers but can't remember where.

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