True canopy size

[henryvillar 0]

Can anybody confirm the following information? -

"The true square footage of a PD-160 is actually 174 square feet. A PD-176 is actually 189 square feet"

The above statement was given to me by a rigger but doesn't match Performance Design's data. I'm currently looking into buying a new rig and would like to know what my true wingloading is going to be.

The opinions expressed herein are not necessarily those of my employer, not necessarily mine, and probably not necessary.

[PhreeZone 20]

It depends on whos measuring formula you use.

Each manufactors formula for measurements are slightly different. You can lay one conpanies 135 on top of a 150 from another and they are near the same size.

PD's formula is quickly becoming the industries base for the measurement of a canopy.


For the first rig, use what is labeled on the canopy.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[henryvillar 0]

I dont see why the results should be any different. Calculating surface area of a rectangular object should be relatively straight-forward with only minor differences between measurement techniques.
Anybody know why there are such different results?

The opinions expressed herein are not necessarily those of my employer, not necessarily mine, and probably not necessary.

[kelpdiver 2]

parachutes aren't as rectangular as they used to be, and at the very least they're 3-D - with a top and bottom. And in flight, they're an arc, not a flat surface.

[mjosparky 4]

Quote

"The true square footage of a PD-160 is actually 174 square feet. A PD-176 is actually 189 square feet"

It doesn't matter, both are still to small for your weight and experience
Are you sure PD let you see their "Design Data"?

My idea of a fair fight is clubbing baby seals

[councilman24 37]

There are multiple methods for determining the square footage. The Parachute Industry Association has published one method appropriate for rectangular canopies. PD chooses to use a different method. Another manufacturer may very well use another. Some published sizes are rounded versions of the true measurement and more model numbers than sizes.

Sizes are only really useful as model numbers. The recommended performance based limit should be used to judge appropriateness. You CANNOT say that a xxx size canopy from one manufacturer that is appropriate means that a xxx size from another manufacturer is either appropriate or will fit in the same container. PD's tend to pack "larger" because their measurements are relatively smaller than others.

From each manufacturer choose the appropriate reserve model (size). This won't necessarily be the same for each manufacturer. The same applies to mains and even perhaps even more so.

Recognize that this can be used as marketing also. "I jump a 120 brand x" may be bragging rights even though the canopy is the same size as someone elses 135.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[darkwing 5]

To paraphrase a famous person "it depends on the definition of "True""

Measuring the area of a modern canopy isn't as straightforward as you think it is. It would be nice if all the manufacturers would agree on a method, but even then it wouldn't solve many problems, since there can be vast differences between two canopies of the same size, due to airfoil, planform, and trim differences.

As it is now, people put way to much stock in the published square footage numbers, which are only useful as a very crude first approximation.

-- Jeff
My Skydiving History

[riggerrob 643]

That depends upon your definition of "true."
Back in the early 1980s, PIA published a method for measuring rectangular canopies. But it is not as good for measuring small, tapered canopies, so a bunch of different manufacturers have developed a bunch of different measuring methods, but the industry is gradually moving towards the measuring method developed by Performance Designs.

PIA method: measure chord in a straight line form the top leading edge - straight - to the trailing edge. Measure span across the top skin, a few inches back from the leading edge. Para-Flite and PISA used to PIA measuring method.

Performance Designs method: measure chord the same way, but measure span across the bottom skin. This results in PD canopies packing and "flying" about 5% larger.

Some manufacturers (i.e. Atair) refuse to explain their measuring methods, preferring to quote "whatever the computer tells us."
We were never sure which method Precision used, but their canopies always packed and flew %5 smaller.
Finally, several manufactures allow marketing managers to define canopy sizes. Since they will sell far more "99s" than "101s", this only complicates the issue. Quick kiddies, what is the difference between a marketing manager and a compulsive liar?

To further complicate the issue, several other manufacturers have converted from PIA to PD measuring methods (i.e. Icarus converted in 2001).
The new Aerodyne (post 2003) uses PD's method.

[ChrisL 2]

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This results in PD canopies packing and "flying" about 5% larger.

.

I dont know if I can agree with the packing larger part.

I have had a Sabre2 210 and a Pilot 210. Both brand new.

The Pilot is easier to bag, but as far as getting it in the container and closing it
I have a much harder time with the Pilot even though I have 150 more pack jobs under my belt than I did when I got the Sabre2 210
The container is a V357 in both cases.

So which system does Aerodyne use? Of the two, the Pilot of the same size definitely seems to have a larger pack volume...

__

My mighty steed

[phoenixlpr 0]

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So which system does Aerodyne use? Of the two, the Pilot of the same size definitely seems to have a larger pack volume...

Have you noticed that those canopies does not use the same material? So pack volume is a different story.

[PhreeZone 20]

The Pilot and the Sabre2 use the same material.

Aerodyne and PD use the same measuring sizes.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Remster 30]

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The Pilot and the Sabre2 use the same material.

I beleive they use SIMILAR material. Unless its changed recently since I talekd with the Aerodyne rep, the material PD uses is eithe patented or trademarked made especially for its products. Aerodyne uses a fabric by the same manufacturer that very closely matches the PD one.

Remster

[kelpdiver 2]

individual variation still exists, and likely is greater than 5%.

[Pendragon 1]

I also understand from a rigger that pack volume is greater on darker-coloured canopies as more coating is applied.

--
BASE #1182
Muff #3573
PFI #52; UK WSI #13

[ChrisL 2]

Quote

Quote

So which system does Aerodyne use? Of the two, the Pilot of the same size definitely seems to have a larger pack volume...

Have you noticed that those canopies does not use the same material? So pack volume is a different story.

Yes I've noticed. One difference being that the ribs in the Pilot are F-111 and the Sabre2 is all ZP.

According to my understanding F-111 packs smaller than ZP so this construction materials difference doesnt account for the larger pack volume of the Pilot.

__

My mighty steed