PD Sabre 2 135 for me?

[skymedic 0]

almost all of those are lightly eliptical...but that doesn't mean they are unsafe......they are all very safe at appropriate wing loadings....I would throw in the PISA hornet also....as I am a bit inclined to it....
marc
BSBD

[n2skdvn 0]

i know the tri is square as for the others except the omega(i have one) im not sure. i like my omega nice turns great landings too can swoop it if i want to!!!
It's not the fall that kills you, it'ssudden deceleration syndrome.

[billvon 2,991]

>Bottom line is that a small highly loaded canopy is like to behave better in turblance than a slow flying canopy.
The results of even a minor pertubation to a canopy planing out at 40mph are very severe; a one-foot drop on a larger canopy will not be as severe. A slower canopy may be somewhat less stable, but will land you more safely in turbulence simply because there is more margin for error (and for turbulence.)
If I ever find myself in really severe turbulence I hope I will be jumping a somewhat large 7 cell.
-bill von

[AndyMan 7]

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I won't argue that.. Are they all seven cell canopies?

No. The PD Navigator, the canopy PD designed excusively for students, is 9 cell I believe.

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Of the bunch which aren't at all elliptical?

Again, the PD student canopy is slightly tapered.
Do you think that just because of these two critera, the Triathlon is safer then the Navigator? Personally, I think there's way more things to consider then just number of cells and planform. Wing Loading, for one - is a hell of a lot more important then either of these. Secondly, depending on where you live, the better glide of a nine cell could save your ass just as much as the docility of a seven cell.
Are you going to argue that the Triathlon is a better first canopy then the Navigator?
Actually, I would. The Navigator would suck after 10 jumps, but that's a different debate.
Canopy choice should be based on a number of factors. Saying blindly that you're going to buy product 'A' just because it was good for you is silly. When the time comes, consider all appropriate products. Then buy the one that makes the most sense.
_Am (who sold his Triathlon, and loved it)
ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
Yahoo IM: ametcalf_1999

[billvon 2,991]

>A 7 cell is no more inheridently stable in turbulence then a 9 cell.
I disagree. High aspect ratio canopies are less stable than low aspect ratio canopies. This becomes very obvious in high AR ram-airs like paragliders.
>What keeps a canopy inflated? Air flowing over the wing and into the wing right?
No. If that were the case, then rounds, Rogallo wings and single-surface canopies (the Paradactyl for example) would not inflate, and sliderless BASE canopies would take much longer to inflate than they do. The primary stabilizing force is the difference in pressure between the top and bottom of the canopy (upwards) vs the normal force generated by the lines (downwards.) On a typical canopy, each line sees 2-10 lbs and can withstand 500lbs or so of upwards force. This greatly exceeds any "air mattress" effect from the inflated canopy.
If you doubt this, take a knife and make long slits in the bottom of several cells on one side of an old canopy. This will effectively reduce the air pressure inside to nearly zero. Now jump it and see whether the canopy retains its basic shape. Next, take another canopy and cut the outer two A/B and C/D lines on one side. See whether that side of the canopy retains its shape.
>In most instances a 9 cell will be travleing faster to start with
>so it maintains its pressure better then a 7 cell.
Quite true, but there is far more to stability in turbulence than that. In fact, pilots will often reduce their speed in turbulence to below structural cruise speed to prevent damage to their aircraft from turbulence. In this case _decreasing_ your speed will decrease the severity of the perceived turbulence.
>. . . that you started and were shown how the higher airspeed causes more inflation in normal flight and
>less turbulence on a 9 cell then on a 7 cell.
Turbulence can be expressed as change in airspeed over time. Increasing your airspeed increases the perceived turbulence, since you are transitioning a region of changing winds in a shorter time.
-bill von

[PhreeZone 20]

Inflated was a pad choice of words. Pressureized is a better word. The faster you go the higher pressure you can maintain in a canopy correct? The higher pressure you are able to maintain, the less sucetible to collapsing a canopy is right? But going too fast in turbulence means if the canopy does collipse it will take a higher pressure inside the canopy to reinflate it correct?
Percieved turbulence is the whole name of the game, a low aspect canopy (not only 7 cells, some 7's are above 2.25 now and some 9's are in the 2.4 range) will spend more time in the turbulence and will have a lower level of percieved turbulence. A faster moving canopy will spend less time in turbulence then a slower canopy, but since the change in airspeed is percieved as higher, the amount of turbulence is percieved as higher too. The actual amount of airspeed change is the same but since its spread over a longer time for the slower canopy... its percieved as "safer" to be under that style canopy in turbulence. Maintaining the pressure in the canopy is the key here...as long as the canopy is maintaining its pressure... Its fairly safe to be under.
Cause I don't wanna come back down from this cloud... ~ Bush

[billvon 2,991]

>Inflated was a pad choice of words. Pressureized is a better word.
I'd prefer the word stable. A stable canopy with no cell pressurization can land you safely; a pressurized canopy wadded up in a ball cannot.
>The faster you go the higher pressure you can maintain in a canopy correct?
Correct.
>The higher pressure you are able to maintain, the less sucetible to collapsing a canopy is right?
Correct. That is one issue. In order of importance, I think the things that give a canopy its shape are:
1. Air pressure above and below offset by force from the lines;
2. Dynamic pressure from the air (this is what keeps end cells deflated sometimes, and why it takes pressure to flare)
3. Static pressure inside the canopy.
>Percieved turbulence is the whole name of the game, a low aspect canopy (not only 7 cells, some 7's are above 2.25
>now and some 9's are in the 2.4 range) will spend more time in the turbulence and will have a lower level of percieved turbulence.
Agreed.
>Maintaining the pressure in the canopy is the key here...as long as the canopy is maintaining its pressure... Its fairly safe to be under.
As I mention above, I put cell pressurization third on the list of important things that keep a canopy flying. It has an effect, but I don't think it's the major one.
-bill von