Mals under a ZP versus an F111

[hongkongluna 0]

After reading the incident thread of the fatality at Prattville, I was wondering if some of you experienced people could point out the differences between having that same kind of mal under a Nav of the same size, for example. There was much talk of Sabre2 being not the best choice for students and new jumpers, if things go wrong. So if you had a busted steering line and line twists under Sabre2, how much faster would things be happening? I had nothing but a couple of minor problems under the student gear, Nav 260 & 220 and have had nothing (knock on wood) under my sabre2...

r

-Rainier

Sparks Brother #1 // "I vaguely heard someone yell "wait!" but by that point i was out the door." Quote from dz.com somewhere

[Thanatos340 1]

I dont believe it is so much the Fabric (ZP vs F111) that people are commenting on as much as it is the shape and trim of the Canopy. A Sabre2 is considered a semi-elliptical canopy.

[hongkongluna 0]

morning,
I am aware of that issue in terms of the canopy shapes being different. I wanted to get a discussion going of actual differences in speed of the mal, speed of alti loss, etc...I didnt mean to focus on the fabrics

Perhaps I should have titled this thread, "Mals under a Nav 220 versus a Sabre2 210"

-Rainier

Sparks Brother #1 // "I vaguely heard someone yell "wait!" but by that point i was out the door." Quote from dz.com somewhere

[faulknerwn 38]

Any sort of elliptical is going to behave much more radically in line twists. I've personally witnessed someone getting their Sabre2 into line twists accidently and having to cut it away because it started spinning radically and losing altitude quickly.

I regularly jump Triathlon 99's - a 7 cell square. Even though its highly loaded, I've had line twists on multiple occasions, and its just a yawner. Kick out.

[simplyputsi 0]

I think the discussion has moved to here regarding the Sabre2 discussion from the incidents.

Now I'm not saying a Sabre2 isn't a canopy to be reckoned with, but after over 150 jumps on mine I have to say I am glad I have one.

Someone spoke of the off heading openings. I was growing to just accept them at one point in time. However I started to pay a little more attention to my packing, as far as going in the bag goes, and also my body position on opening. When I did this I started to have dead on soft openings. I was like holy crap, bout time.

Then the last time I was out she spun me around 360 on my last opening. My fault, my body position was horrible. In my opinion you have to have a good body position upon release of your pilot chute. Then you have to maintain that position throughout deployment, of course you don't stay arched.

I think this is true for any canopy. I have never had my Sabre2 spin me violently, or anything near it. I can remember a jump where I was turning on deployment and ended up with many a line twist upon opening. I immediately was like shit!!!, then I noticed like all other times nothing violent was going on, so I grabbed the risers, pulled and kicked and that was that. It has always happened like that for me and this canopy.

Others have told me they have the same experience. What is my wingloading you say. I've ranged from 1.1 to max 1.3.

I'm not saying students should be flying a Sabre2. I'm just not so sure a Sabre2 is an unforgiving canopy. Only thing I would say is a lower wingloading does not seem to work well with one. That is just my opinion as everything I've written is just that. I'm looking for other opinions about this canopy, from people that have one or have had one.

Thanks

Skymama's #2 stalker -

[pilotdave 0]

I've had line twists on my sabre2 a ton of times. Loaded at about 1.1. Never got it to spin, even when I induced line twists by accident at 1100 feet, nor when I've had linetwists due to a toggle coming unstowed. Not saying it can't spin due to linetwists, but at least at light wingloading, I don't think the sabre2 is at all prone to doing anything radical because of linetwists. I once had a riser cover fail to open... pretty much flew straight even when things were completely uneven (without linetwists).

Dave

[hongkongluna 0]

Why does the planform make it behave more radically? Is the entire system under more tension because of the lines attaching to that shape?

Where is Brian Germain (or some other canopy designer) when you need him ??

I'm trying to get a sense of what exactly it means going off the student gear and getting your first rig with a Sabre2 in it, loaded 1:1. I could tell when I demo'd it that it definitely flew faster and with better control but it didnt seem like i was on top of a wild horse or anything that could go crazy at any moment...but i guess all of our canopies have that potential.

-Rainier

Sparks Brother #1 // "I vaguely heard someone yell "wait!" but by that point i was out the door." Quote from dz.com somewhere

[jheadley 0]

A navigator also has a tapered edge. You could call that semi-eliptical if you wanted.

I'm not sure what exactly causes the spinning. I've had a good 7 or 8 line twists on a Sabre 2 170 that flew perfectly straight, and only 2 line twists on a Sabre 1 170 (rectangular) that had me turning. I think it's more just uneven risers than the twists themselves.

[Jwelborn 0]

Can I throw another canopy into the discussion? I've been meaning to email PD and ask why the Spectre is not recommended as a student canopy. I've rented Sabre 1s and 2s and my Spectre is way more forgiving of bad packing technique and body position. Flew nice and stable while I kicked out of 6-8 line twists a couple of weeks ago too.

The supreme irony of life is that hardly anyone gets out of it alive.
Robert A. Heinlein

[hukturn 0]

If line twists are equal, you should remain in stable flight. But, if one set is drawn tighter then you introduce pressure on that side. Thus, creating a spin. The line twists themselves should not cause a spin. Okay, pulled it out of my ass, but it seems logical.
Of course, wing load would play a huge factor in this, also.

[illusioneer 0]

Like an acrobatic airplane, in order to get more performance (faster turn rates...ect) you usually have to give up stability. In other words the more stable a wing is , the more input it takes to get it to respond. So a less stable canopy is more responsive to small inputs and reacts faster. With a big stable student rig shifting your weight in the harness will have little result but with an advanced heavily loaded chute the result can be much greater.
So if something other than normal happens in a high performance chute it will be harder to control and you'd have less time to try.
The important part is to not get into a chute that is a higher performance canopy than you can handle at your skill level if and when something "other than normal" happens while you are flying it.I hope that answered your question hongkongluna

[billvon 2,991]

> If line twists are equal, you should remain in stable flight.

On a stable canopy, that's true. But some canopies are inherently unstable in brakes - the Mamba and the Diablo come to mind. Left alone they will eventually pick a direction, start turning, and the turn will continue to steepen into a spiral. One reason line twists are worse on some canopies than on others.

[ZigZagMarquis 9]

"Back in the Day", when I used to jump a PD190 and would get the occasional line twists on opening, it felt much more "docile" then the occasional line twists on my Sabre2 170 I now jump. The PD190 w/ line twists would fly "stright and level" and you just had to kick out the twists is what it "felt more like" as compared to the Sabre2 w/ twists; which feels like its "just wanting to" take off into a turn or spin in the occasional case where it opens into line twists. So much so, that I really really hate it when my Sabre 2 threatens me with line twists on opening that I tell myself to be very aware of whether or not the canopy is diving and/or turning while trying to kick out the twists and whether or not its getting worse or flying out of the turn and just has a line twist or two.

One other comment, I have one cut-away from my (classic) Sabre 170 because once on opening it opened into a couple of line twists and a turn, which at first, I thought, "I got it -- just kick the twists out", but then it went to a whole other (higher) order of magnitude (after the right side of the canopy collapsed) and turned itself into an SBOS (spinning ball of shit) malfunction that I had to get rid of. For the record, at that time, the canopy was badly out of trim and in need of a line-kit and I just wanted one more weekend out of it before sending it back to PD...

Anyway, I don't think it has anything in particular with ZP vs. F111 as it does to do with an "HP" design vs. a more docile canopy design and it just happens that pretty much all of your HP canopies are made out of ZP.

[hongkongluna 0]

Note to self: Avoid Diablo & Mamba canopies for a few thousand jumps.

I hadnt realized that more performance necessarily meant more instability.

-Rainier

Sparks Brother #1 // "I vaguely heard someone yell "wait!" but by that point i was out the door." Quote from dz.com somewhere

[hukturn 0]

Gotcha! Of course, I am the one who has cut away 100% of the ellipticals I have jumped. Not on the first time, but at some point or another they have all been cut away. Sabre1 has been kind on openings and swoops better than most. I even considered landing without two left end cells after low level CReW took tham out. It was flying really well with minimal corrections.
Bottom line...I am not the authority on ellipticals. And, I think that the spinner problem at hand is more due to ellipticals than zero-p.

[riggerrob 643]

Planform is just one variable that determines how fast a canopy spins when it malfunctions.
The ellipticalitynessosity factor is just one variable.
Furthermore, there are a dozen different definitions of "elliptical."
For example, some canopies have all their taper on the trailing edge: Diablo and Pin Tail.
Meanwhile, some canopies are only tapered along the trailing edge: Swept-Wing Jedei.
Some canopies have all their taper in the end cells, while others (i.e. Safire) have very cell a different size.
Over the years, designers have learned to fine-tune taper to achieve a variety of different flight characteristics. For example, tapered student canopies (Solo 270 or PD Navigator) use air foil sections and line trim that create ridiculously short recovery arcs (i.e. how long does it take to get a canopy overhead after a turn?). On the other hand, pro pond swooping canopies are designed to have ridiculously long recovery arcs.

[riggerrob 643]

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Can I throw another canopy into the discussion? I've been meaning to email PD and ask why the Spectre is not recommended as a student canopy.

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Ten years ago, Spectre would have been considered an ideal student canopy, forgiving of sloppy packing, forgiving of line twists, etc.
However, better student canopies have been designed since then: Solo 270, ZP Manta, Navigator, Skymaster, etc.

The biggest difference between Spectre and most student canopies is that most student canopies are nine-cells, and have a higher aspect ratio. Spectre's aspect ratio is only 2.14, while most nine-cells have aspect ratios in the 2.6 range.
Greater aspect ratio means a better lift-to-drag ratio, which - practical terms - equals a much larger sweet spot for flaring.
A large sweet spot means more lift/deceleration/braking, but more importantly means a "flare window" that is several seconds longer.
With a nine-cell, a student can flare two or three seconds too early or two seconds late and still walk away from the landing.
The same mis-timing - on a smaller 7-cell (i.e. Spectre) - will have them limping away from the same landing.
The other variable is size. The biggest Spectre only has 230 square feet, while most schools use student canopies in the 270 to 300 square foot range. While 230 square feet may be large enough for Japanese girls, it is unforgiving of mistakes made by bigger, fatter students.

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[kallend 2,027]

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While 230 square feet may be large enough for Japanese girls, it is unforgiving of mistakes made by bigger, fatter students.

I am certainly bigger than a Japanese girl, and I did my student training on a 190 (3 jumps) then a 170.

...

The only sure way to survive a canopy collision is not to have one.

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