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Top Ten Misconceptions About Zero-P Canopies

Posted Monday, November 17, 1997

By Bill von Novak

A while back, I overheard a bunch of people discussing therelative merits of different types of canopies and materials forlow-time jumpers. I heard some interesting misconceptions aboutwhat's dangerous and what's not, what works and what doesn't. Inthe interest of getting some discussion going, I figured I’dlist my top ten misconceptions about Zp canopies:

1. Zero-p canopies are dangerous.

Zp canopies have gotten a bad reputation over the years, sincemost hp canopies are made of Zp fabric. However, this does notmean that hp fabric itself is dangerous - it just allows smallercanopies to land well, and so is often used for smaller, highperformance canopies. A large 9 cell Zp canopy is just as safe asits same-size F111 counterpart.

In fact, it is often safer. Zp fabric keeps air from escapingthough the top and bottom skins of the canopy, and thus allowsbetter canopy pressurization at a given airspeed. This helpsprevent canopy collapse in bumpy winds. In addition, the Zpfabric allows the airfoil to be a bit more efficient, and thusallows you to slow down a little more before landing. During alanding in a bad area (a power station, for example) that slowerspeed can be a lifesaver.

2. Zero-p canopies are harder to land than F111 canopies.

Not at all. In fact, the opposite is often true. Zp canopieshave more lift during the flare, and that extra lift can be usedto slow yourself to walking speed before touching down. F111canopies, especially old ones, often can't do that any more -they become so porous that they stall before slowing you downenough. Often, you will see people with older F111 canopies doingall sorts of tricks to get good landings - front risering, takingwraps on the brake lines, and turning low. Generally, suchmaneuvers are not required with Zp canopies.

This year I watched maybe 200 landings at bridge day.Conditions were not great - zero wind and an uphill landing. Thepeople who got the best landings were the people with fairly new(i.e. not porous) F111canopies and the people with Zp(Triathlons, Sabers, even a Stiletto or two). The people with theragged old Cruiselites and Pursuits were slamming in hard. Thecanopies simply did not have enough lift left to slow down thejumper before landing.

3. F111 canopies are a good choice for a first canopy.

Well, yes and no. A good, fairly new F111 canopy, loadedcorrectly, is indeed a good first canopy. However, you have twothings against you:

  1. Few people sell good, low-time F111 canopies any more. Most have 500-1000 jumps on them, and at that age, they become difficult to land. A larger canopy will not be affected by this as much as a smaller canopy, so size matters. A pd230 may still land you well after 1000 jumps, since its forward speed is low to begin with. A PD150 with 1000 jumps will be very hard to land without injury for most jumpers.
  2. It's hard to resell F111 canopies, for the very reason mentioned above. They are generally retired after about 500-1500 jumps, do you're paying about $1 per jump for them. Zp lasts much longer - you can easily get 2000 jumps out of a Sabre 150 with an occasional line replacement. This ends up costing you around $.60 a jump.

4. Zero-p canopies open really hard.

This rumor came about mainly because of the performance of theSabre and the Monarch, two popular Zp 9-cells. It is no longertrue. The Sabre was tamed by a larger slider, and mods exist forthe Monarch. Newer Zp canopies, like the Triathlon, open quitereliably and comfortably. Some new Zp canopies, like theStiletto, Spectre and Jedei, are designed to snivel for a longtime, and give extremely soft openings.

This was a boon for cameramen, who need soft openings due toall the weight on their heads.

Of course, there's a tradeoff between too little snivel andtoo much. But there are Zp canopies available that open at nearlyany rate, from rapid to very slow. Packing is an important partof that scale, and between canopy selection and packing techniquethere should be a wide range of openings to choose from.

5. You have to get a smaller canopy to get better landings.

Not true. Many people start out on old F111 canopies, andsimply assume that to get nice, soft, swooping landings like thepros, they need a small canopy like the pros. The truth is thatnearly any Zp canopy will land you well, if you fly it correctly.The technique you use depends on the loading, as listed below:

.8 psf or less - flare like a Manta. Wait until 5-10 feet, then smoothly bring the toggles down as far as you can. It will land much like an F111 canopy, with a little bit more flare.

.9 to 1.1 psf - here, the flare will begin to be stronger. The flare is similar, but now you'll stop your flare as soon as the canopy levels out, then complete the flare slowly as the canopy decelerates. It's important to keep flying the canopy the whole time - don't start sticking out your hands to "break your fall", or your canopy will happily obey and turn you into the ground.

1.2 psf and above - to land at these loadings, you need to initiate the flare very smoothly, and use the toggles to keep the canopy level and straight as you plane out. The plan is to use the toggles to keep your feet an inch off the grass until the canopy stalls. If you can do that, you've landed yourself at the slowest possible speed.

6. You need to get a smaller canopy to go faster.

While it's generally true that smaller canopies go faster,there are many other options to increase your speed and turn ratewithout taking away wing area. Wing area is all you have keepingyou in the air, and taking it away decreases the canopy's"forgiveness", or tolerance for mistakes. Some ideasfor increasing speed/maneuverability without sacrificing area:

  1. Canopy choice. The Silhouette, for example, is designed to be a faster large canopy. A 170 should give you nearly the same forward speed as a Sabre 150, with the extra forgiveness that the larger size entails.
  2. Pilot chute. The single best thing you can do for your medium / high performance canopy is to get a collapsible pc. It will do wonders for your glide, forward speed, and flare. I highly recommend this as a first step, before you get rid of that old, doggy canopy. Even older F111's can benefit from this.
  3. Slider. Figure out how to stow your slider somewhere. There are many different types of collapsible sliders, and they affect performance two ways - by reducing drag, and by allowing the risers to spread out more. Avoid stowing it on your jumpsuit, though - this can prevent a cutaway if you have a problem later, and has led to a few serious injuries.
  4. Riser tricks. Mini-risers reduce drag a bit, but not a whole lot. Separate riser-keeper rear risers allow the toggles a bit more freedom, and distort the canopy a bit less when you flare, allowing a little more flare power. Front-riser handles allow you to easily add front riser, a good way to increase your speed when trying to buck a headwind (for example.)

7. You should never, ever turn near the ground.

This is a good rule of thumb for your first few jumps.However, there are times when turning near the ground isnecessary, and all jumpers should know how to do this safely.Basically there are two ways to turn low - the braked turn andthe flare-turn. Practice these! Both allow radical turns withouta resulting dive towards the ground. Many jumpers have beenkilled when they found themselves flying downwind or towards anobstacle on final, and tried to turn without using these tricks.Depending on the canopy, you can safely make a 180 degree turn aslow as 50 feet - if you've gotten instruction on how to do it andpracticed it up high.

8. Skydive Chicago puts first-time jumpers on tiny Sabres.

Not quite, but close. They put first-time jumpers on Mantas(or have them do tandems) for the first few jumps, thentransition them to hp canopies. And interestingly, there have notbeen more injuries as a result. I think this is because many newjumpers learn bad habits on Mantas, and these bad habits aredifficult to unlearn. At Skydive Chicago, they transition earlyon, and get good instruction on how to fly the newer hp canopies.

This is a good model for transitioning ourselves. Wheneveryou're going to make a significant canopy transition (i.e.smaller, square to elliptical, etc.) get instruction! It costslittle to badger a more experienced jumper or instructor intowatching you land a few times, and the advice you get can beinvaluable later.

9. 7 cell canopies are dogs.

Not any more! The Triathlon and the Spectre are both highperformance Zp canopies, and are good choices for jumpers buyingtheir first Zp canopy. The big difference between 7 and 9 cellcanopies is aspect ratio - which is just the relationship betweenwingspan and front to back size. 7 cells have ar's around 2.5 to1, and 9 cells are around 3 to 1. Generally, a higher ar has abetter glide ratio, but that's about the only hard-and-fastdifference. Zp 7-cells can go as fast, land as well, and planeout as far as their 9-cell counterparts, if they are loadedcorrectly. They are a bit more forgiving at similar loadings, andare thus a really good choice for a first Zp canopy.

10. It's really hard to pack Zp fabric when it's new.

Sometimes this is true, but not always. "SouthAfrican" fabric, such as the material they use in theTriathlon, is pretty easy to pack from day one. It doesn't seemto last quite as long as the more slippery PD material, though.Some canopies, like the Silhouette and the Turbo-z, mix F111 andZp material to make a canopy that flies well and is still easy topack.

But even a brand new Sabre is manageable, if you work at it.The psycho-pack is a good way to control an unruly canopy, andthere's at least one gadget out on the market that helps you packslippery canopies.

Copyright 1997 Billvon Novak, Safety and Training Advisor




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