Factoring the Weight of a Canopy?

[AggieDave 6]

Had a thought/question about wingloading calculation.
We generally use our exit weight as the number to use against the size of the canopy, but wouldn't the suspended weight under the canopy be different? The total weight of the main canopy wouldn't factor into the equation, since it is a wing and slowing the decent, right?
A human cannonball, I rise above it all
Up higher then a trapeze, I can fly

[Hooknswoop 19]

For wingloading, just stand on a scale all geared up. The weight of the main is included in the wing loading calculation, it has to support it's own weight too. Same thing for aircraft, the weight of the aircraft includes the wings.
Hook

[AggieDave 6]

Yeah, I figured it had to support its own weight, I was thinking that it wouldn't be the full amount of weight, just a fraction.
A human cannonball, I rise above it all
Up higher then a trapeze, I can fly

[flyinryan 0]

What about max suspended weight...a lot of manufatures give us that number??? Does that include the canopy? How about the lines? Sorry if this is a dumb question.

[quade 4]

Quote

Yeah, I figured it had to support its own weight, I was thinking that it wouldn't be the full amount of weight, just a fraction.

Well, ya don't get nothin' for free.
The aerodynamic forces aren't just holding up the cargo, they're holding up the wings as well.
quade
http://futurecam.com

[GrumpySmurf 0]

Hmm would make sense if it did factor in the canopy - since all other weight calculations for the canopy do *shrug* Though if you are coming close enough to this number that the weight of the canopy would make a difference, you may wish to look at a different/bigger canopy

[freefallin14 0]

How do manufacturers figure out their max suspended weight for the canopies? Is this an actual weight that they have seen failure at, or a percentage of a weight that will cause failure, etc? Especially in the case of reserves. Not that I am that close to any max weights I am just curious to know how it is done.
Bret

[SkydiveMonkey 0]

I think it's got a lot to do with performance drop offs as well ie. the canopy will not give you enough lift for a nice landing.
When you participate in sporting events, its not whether you win or loose, its how drunk you get.

[pilotdave 0]

Think the weight of a 747's wings aren't taken into account for it's wingloading? It's the same thing with a canopy... It's gotta generate enough lift to match your weight plus it's own weight.
Dave
http://www.skydivingmovies.com

[apoil 0]

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Yeah, I figured it had to support its own weight, I was thinking that it wouldn't be the full amount of weight, just a fraction.

So what would be supporting the rest of its weight?
It's not just going to float there.

[polarbear 1]

The maximum weight for a reserve is dictated by the TSO under which it is certified and is based on strength requirements. Most of the reserves we use today are under TSO C23c, Category B, which specifies 254 lbs. maximum weight (this is why most of PD's reserves have 254 as a maximum weight). This isn't the weight at which the reserve will fail; it is just the weight at which it has been certifed to not fail. I think the TSO actually requires the reserve to be tested with 300 lbs, but don't quote me on that.
Some designers, like Precision, take it a step further and introduce a facrtor of safety in the maximum weight for a reserve, thus, the Raven has lower than 254 lbs. for a max. The Dash-M is under a different TSO (TSO C23d), which allows the manufacturer to specify its own maximum weight.
For main canopies, the maximum usually has more to do with performance, specifically, landing performance. Some canopies are designed for lower speeds and just don't do well with more weight.

[riggerrob 643]

To clarify polarbear's post, there are usually two weight limits on reserves.
All modern reserves must demonstrate that they can survive opening at 254 pounds at 150 knots.
Most manufacturers placard their smaller reserves at less than 254 pounds because they do not expect your ankles to survive a landing at 254 pounds. A few manufacturers (ie. Performance Designs) try to link exit weight to the users' experience level.

[AndyMan 7]

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A few manufacturers (ie. Performance Designs) try to link exit weight to the users' experience level.

How's that? Fat people are less experienced?
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[DanG 1]

He means to say that a new jumper should not jump a PD-126R at X-pounds, while an experienced jumper can get away with it at that weight. They are really giving wingloading guidelines, but giving people a weight for each canopy size is easier to understand.
- Dan G

[freefallin14 0]

Thanks for the answers all. What about mains? Do test jumpers go up with new canopies and say, well this doesn't fly or land well at anything more than this weight? Or is it more of a educated guess. Why does Precision Aerodynamics make such a strong point about its Xoas 21 that the max weight is not to be exceeded.
"Maximum Operating Weight Limitations for the Xaos-21 are absolute. Do not exceed these limitations under any circumstances. Severe bodily injury or death may result in exceeding these limitations of experience and/or wingloading."
Is the max weight listing for main canopies more of a performance issue or a safety (canopy cannot handle the load) issue?
Bret