Low speed lift.

[rmcvey 0]

What design characteristics give a canopy good lift at low speed, e.g. cobalt more bottom end than stilletto...

Is it purely airfoil shape?

In other words why do some have a better "bottom end" than others.

[Geoff 0]

I'm sure airfoil, planform, line trim and wing rigidity during the flare all play a part. Probably some other factors as well.

[yarik 0]

Among the others:

- Thickness of the airfoil - the thicker - the more lift at low speed.

- Planform - the closer it's to the rectangle - again - the more lift at lower speed.

- The design of the front edge - to maintain good presurization at slower speeds.

IMHO the best slow flyers are Accuracy canopies. Compare even visibly details of the design of them with some hp ones and see the difference.

The problem is that in most cases changes in design for increasing the lift at slower speed will induce more drag (like in the airplane - lowering the flaps requires more throttle, while having more lift at slower speed). So there always should be a balance.

[grega 0]

Quote

Compare even visibly details of the design of them with some hp ones and see the difference.

How about comparing it to gliding canopies, and they are totally nothing like accuracy canopies

"George just lucky i guess!"

[yarik 0]

Quote

How about comparing it to gliding canopies, and they are totally nothing like accuracy canopies

oops.... you're right, nothing... my guess would be that they are not that good slow flyers as accuracy canopies, but for slower flight capabilities thay have higher area and consequently - smaller wing loading.
Paragliders are designed not for the slowest flight, but for the best ratio of Lift to
Drag which is reffered as "wing quality" in Russian (who knows the correct term in English, please advise). This allowes them to sustaintain flight with very little vertical speed.

Personally jumped accuracys as well as hps, but never flew paraglider, so this is just theory for me so far and I may be wrong.

Who can add something here?

[DrewEckhardt 0]

Quote

Among the others:

- Planform - the closer it's to the rectangle - again - the more lift at lower speed.

I don't think so. At the same size, elliptical canopies have a lower stall speed than squares.

Quote

IMHO the best slow flyers are Accuracy canopies.

Because they're huge and can be landed in a controlled fall even if the wing does stop flying. Scaled down to not much over 100 square feet they wouldn't work for all but the smallest jumpers.

[grega 0]

well the question was, What design characteristics give a canopy good lift at low speed.

i haven't flown a paraglider either, but i saw plenty of them. Try putting paraglider in deep brakes, and you'll see that it looses almost no height at slow speed, meaning that even at slow speeds it produces a lot of lift.

Quote

Paragliders are designed not for the slowest flight, but for the best ratio of Lift to
Drag

I think glide ratio and lift are more or less dependent. more lift means the canopy can have better glide ratio.

well all i wanted to state with this paraglider comparison is that the characteristics that help produce lift are completely different than characteristics at accuracy canopies. and accuracy canopies produce close to nothing lift. did you ever see accuracy canopy swoop, or climb?
i just think that paragliders are the best "lift producers" regardless of speed.

But that's just me, i could be wrong.

"George just lucky i guess!"

[yarik 0]

Agree and not Well, obviously, never seen accuracy canopy swoop, but that's just because of the huge drag they produce.
If we think abstractly of an airfoil - at the same AoA and same airspeed more lift will be produced by the one wich is thicker - Bernouli's principle, that's for sure.
What I'm thinking now is that the initial question was not only about the lift on it's own, but indeed, as you said about glide ratio. In this case reducing drag at the same angle of attack will result in the flatter glide slope. I think that one way to reach it - is to flatten a bit angle of incidence. In this case canopy will get a bit slower, but more efficient at lower speeds since could be flown in less or no brakes at that range vs the canopy with steeper AoI.
To continue the discussion I need a board and a marker

[freeflyfree 0]

mmm lets see, I found something in the Talk Back forum hmmm Accuracy Landing

--
Blue Skies
NO FEARS, NO LIMITS, NO MONEY...
"A Subitánea et Improvísa Morte, Líbera nos, Domine."

[quade 3]

Quote

Is it purely airfoil shape?

In theory -- yes.

In practicality, because we're talking about flexible wings that only hold their shape due to ram air pressure, you also would have to take into consideration how well it can sustain that shape at slower airspeeds.

But, long story short, it's the shape of the airfoil.

You can fool around with airfoils yourself with the NASA Foilsim program. It's a JAVA program that should work on any system with JAVA.

There is usually a tradeoff between low speed lift (which causes a lot of drag) and high speed performance (which is the result of low drag and therefore less lift).

quade -
The World's Most Boring Skydiver

[quade 3]

Quote

If we think abstractly of an airfoil - at the same AoA and same airspeed more lift will be produced by the one wich is thicker - Bernouli's principle, that's for sure.

Only to a certain point at which it becomes less efficient again.

quade -
The World's Most Boring Skydiver

[yarik 0]

Quote

mmm lets see, I found something in the Talk Back forum hmmm Accuracy Landing

Shit... that looks scary ...
But you know what - they approached in brakes, leaving no room for flare and trying to hit the target, plus it looks like there's no wind - which in conjunction is quite bad for demo jumps on concrete.
I don't know if anyone tested it, but if someone tried to put paraglider into the same glide slope at the same weather conditions, it will probably stall...
But for better performance at low speed (we are not talking about more lift only), i think we have to get back to efficiency of the wing or L/D ratio, which if higher, would let it just fly better, but L/D ratio also is different at different AoA, so - if the rigger's angle of incidence is adequate to the AoA of the highest L/D ratio than the canopy would be less aggressive and more polite and fly flatter, actually it would be tuned to the flattest glide, but it won't speed up as fast.
Yes, I think if you take two the same canopies, one would fly better at low speed whos AoI corresponds to lower speed flight AoA.
Maybe here is anyone from manufacturers of the canopies or test pilots, who can confirm or disprove my thoughts?