Troll canopies

[ArmitageShanks 0]

I don't understand this:

"The Troll is available in five precisely scaled sizes: (Note – Atair measures surface area by measuring the span x chord of the bottomskin)

205 ft.2 = PIA spec 220
225 ft.2 = PIA spec 240
245 ft.2 = PIA spec 260
265 ft.2 = PIA spec 280
290 ft.2 = PIA spec 305"

(From the Morpheus website).

Who measures their canopies differently to this?
If you buy a Flik 293 or an Ace 280, are they actually smaller than you think? I don't get it. If a 290 is a 305, why not call it a 305? Or is it really a 290?

?????????????????????????? Help?

[TomAiello 25]

I have been very confused on that issue myself.

Here's what I've learned.

Every manufacturer I contacted (CR, BR, Vertigo) says that their canopy is measured according to the PIA standard.

In general, the Troll is about the same size as the next larger canopy from other manufacturers. I'm not sure why Atair doesn't measure their canopies using the PIA standard. A question for Stane, I suppose.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[unclecharlie109 0]

Hi,

I emailed Stane on this issue and received the following response:

"The method we use is common in aviation: wing span x chord. When the canopy is inflated, the wing span shrinks about 12 to 15 %.

We'll use the PIA system in the future. "

Mucho BASE,

James

[Gargoyle 0]

When we first began working closely with Stane, the designer and manufacturer of the Troll, we had similar questions. We were accustomed to the generalized PIA standard method of measuring a canopy to determine its size as well.

Stane prefers to use the "Fly CAD 2000" computer program to design and subsequently measure his canopies. It was developed by Michael Nesler who is a leading paragliding and wing designer, known throughout the world.

http://www.profly.org/eng/index.htm

When working with this program, several parameters are needed to formulate the outcome such as the wing plan form, the baseline, frontal canopy arc, the number of cells in the canopy, the rib system (diagonals, etc.) and the skin tension. To get the canopy size, the measurement still consists of Chord X Span, but with this method, both the chord and the span are measured by the bottomskin as opposed to the PIA recommendation of using the mean chord X span on the topskin.

Stane feels that this method calculates a figure that is nearer to representing a flying canopy. The bottomskin is tensioned when measured on the ground and Stane feels that the measurement that is taken at that time most represents the measurement of the bottomskin when inflated. When using the PIA measuring method, we feel that people are led to believe that they are under a far bigger canopy than they actually are flying. This being because of the reduction in overall measurement of the canopy from the ground to full inflation.

Once he explained this to us, we felt that there was great validity in his beliefs and have stayed with these measurements. However, we have tried to educate customers and let people know the approximate comparisons to the PIA method of measuring. We have always guided our customers in size recommendations for their wing loading and jumping needs.

Regarding the PIA method of measuring... which was developed about 20 years ago is still quite open to interpretation. If 3 different people were to measure the same canopy with this method, those 3 people would come up with 3 entirely different results. If every canopy could be sent in to the PIA and measured by the same individual, it would come closer to achieving more subjective and consistent results. The late Ian Bellis wrote an interesting article when he was employed by Performance Designs.

http://www.performancedesigns.com/docs/packvol.pdf

If anyone wants to take the time to read this, I think that you will be quite enlightened by the conclusions that have been reached by PD.

Although Stane's method of measuring a canopy was taken from paragliding, it is felt that its application offers a high degree of accuracy in the sport of BASE jumping and we don't want to ask him to change this. At this point, there are so many Trolls out in the field that we think that this could cause even more confusion.

Although paragliding spawned from skydiving; in its short lifespan, the sport has grown far more world- wide than skydiving and certainly more than BASE jumping. With this, the advancement in paragliding technology is stead lily providing more information and education to the skydiving industry in the development of winged flight as opposed to the use of a crude aerodynamic decelerator. Parachute design in general has come along way since the implementation of the PIA measuring system. In this way, we feel that the obvious widespread use of design programs in todays ever changing world is offering an accuracy and appreciation that was not possible 20 years ago.

Maybe in the future, the PIA will revise their method. Virtually every canopy today that we are aware of is designed on a computer and although the PIA method of measuring can be calculated on a computer, the method itself was not created with the understanding of todays single wings. The PIA came up with the best method possible at the time with the knowledge that they had of those new fangled things called square parachutes.

Stane has always been one to follow his feelings and beliefs. In this way, he researches every aspect of flight and methodology. We have a great respect for him as he has been in this and related industries such as hang gliding and paragliding since he was a kid. He built and flew his first hang glider at 21 years old and has a great passion for all aspects of flight, including BASE jumping.

Agree or disagree, hopefully this information has shed some light on to why Stane uses a different method of measuring his canopies.

[wzettler 0]

This just some thoughts in general:
So does this mean that jumpers (both BASE and skydivers) have been jumping higher wing-loadings than they thought? I guess it does. I guess that if a more accurate system of measuring square-footage is available then wing-loading recommendations would also have to be adjusted? Maybe the PIA would think this is too much of a pain to switch to, kind of like in America we still don't use the metric system when most everyone else does.

I think when Jesus said "love your enemy" he probably meant don't kill them.

[TomAiello 25]

Quote

So does this mean that jumpers (both BASE and skydivers) have been jumping higher wing-loadings than they thought?

Not really. When you say "my wingloading is X" what you are really doing is expressing common shorthand for "the flight characteristics that I experience under this particular canopy approximate Y."

In other words, it doesn't matter what the number is, just that we all understand what it means--which, in general, we do. For example, if we all started expressing wingloading as tons per square inch, that wouldn't actually change the flight characteristics of our canopies any, only the numbers we used to discuss them.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com