Re: New canopy (Outlaw, Hayduke, Vision)
Some more info on “Why ZP” A small amount of ZP used in a specific portion of a BASE canopy has proven to provide benefits to glide, flare, and openings.
Aerodynamics (specifically the effects of low or zero porosity surfaces on an airfoil) on such a simple level as BASE canopies usually don’t create much debate. There are factual benefits to zero porosity cloth, and well-documented benefits to it being used sparingly on BASE canopies.
Compared to a canopy with no ZP on it:
A canopy with a ZP leading edge will open faster, glide further, and flare better, on jump 1.
And, it will open faster, glide further, and flare better on jump 1000,
all other things being equal.
Why? Due to a simple fact which we can probably all agree on: air passes through permeable cloth, but does not pass through non-permeable (ZP) cloth.
The leading edge is a critical part of the airfoil (including at high AoA during flare), any air that passes through the surface of the canopy does not create circulating flow (lift) over the top of it, or add pressure to the inside of it.
ZP is 100% about improving aerodynamics, and that is why these days it can only be found on a small portion of the leading edge. It’s great to be focused on durability. That is a part of BASE. But that is not principally why ZP benefits parachutes.
About pack volume:
ZP is used on a small percentage of the chord, on the upper surface only. We have the upper, we have the lower, and we have the ribs. That means ZP makes up a total of less than 8% of the canopy fabric in your packjob for most parachutes.
About the weight:
Common ZP cloth is about 50 grams per square meter. PN9, the lightest cloth we could compare it to, is 30. What is 20 grams more weight per square meter, on less than 10% of the total fabric? The difference in actual weight on an Outlaw 248, for example, uses about 631 square feet of cloth, with 29 of that being ZP. That’s only 5% of the total, and about 60 grams (two ounces!) more weight. This ratio will be similar across most modern canopies which employ ZP.
About packing:
I have never met anyone who has been unable to handle the small amount of ZP on modern BASE canopies. Understand packing, and what the ZP is doing for you, and the result of having it there.
About openings:
A canopy with a ZP leading edge will expand and inflate faster, all other things being equal. That is why it is important to understand how to configure your gear for higher airspeed deployments (slow slider, slider brake, slider control, PC selection, packing), and how to control your airspeed and body configuration (change your AoA before deployment whether you’re tracking or wingsuiting). Learn these things, use ZP, and reap the many benefits (which, we should say, include faster openings).
(One point to consider: if you have a glass back or neck, you might not want to deal with a faster opening, or you could take a shorter delay). For 99% of jumpers, the performance benefits of ZP outweigh the costs.
Some “real” cons of ZP from a manufacturing perspective: It’s more expensive: Unless you’re getting the shaft from Porcher Industries because you order PN9 infrequently and in small quantities, ZP costs more than PN9 and most other 0-3cfm cloths.
Top surface cuts: It takes more time to manage an additional top surface panel, cut it, connect to main panel. Time is money.
It’s slippery! Like a new skydive main is annoying to pack, it requires understanding and skill to sew and takes more time.
It’s more cloth to stock. BASE jumpers like colors, and stocking another range of colors in another cloth type is not easy.
Also note: Many aspects of BASE canopies get worse if you use
too much ZP.. There is, without question, a sweet spot (amount). And there is, without question, a point where it quickly becomes generally detrimental (there is a reason why BASE canopies are almost entirely 0-3cfm cloth). But that “too much ZP” point was worked through many years ago, and modern BASE canopies have what we could say is a proven and successful track record of using the right amount of ZP in the right places.
For an example of too much, it was learned years ago that a complete upper surface ZP canopy does not perform well during extraction (so slippery!). If one formed an opinion about ZP way back then based on that much ZP, it would not apply to today’s parachute designs.
For more background on parachute cloth and how it is employed today by some BASE manufacturers, see here.
https://squirrel.ws/...-light-right-for-you thanks.
-Matt