Lucifer

Standard disclaimer , etc. Just trying to clarify : As I understand the phenomenon the prime motivation of the canopy filling is the depression zone created over the canopy because of the vertical speed (relative to air) towards the ground. This depression expands the upperskin, just like inflating a chewing-gum outside-in (inside your mouth) by sucking air from outside. There would be three steps in an ideal canopy inflation : *POC = air Pressure Over Canopy PIC = air Pressure Inside Canopy PUC = air Pressure Under Canopy 1) The canopy (after expansion) is deflated and act as an aerodynamic deccelerator just like said above. The trajectory is vertical. A depression is created over the canopy, thus sucking the upperskin up, making the canopy suck the air from outside. During this phase, POV < PIC < PUC so any vent will let the air inside the canopy fill the cells quicker but the canopy will inflate even if there's no forward motion and no vents. 2) The canopy is inflated, but the bottom skin is curved inside or just flappy. POC < PIC = PUC. The shape is ready to act as a wing as soon as any horizontal component will occur. 3) As the canopy begins to move forward (because of the "deflection" explained by Tom), a minimal amount of air goes dynamically in the cells from the nose (due to the relative wind). POV < PUD < PIC. As the pressure inside the canopy is greater than the pressure under the canopy the bottom skin inflates towards the outside, making a clean inflated shape of each cells. so pretty much the same conclusions head wind -> quicker inflation in 3) and quicker transition to flight mode (less forward speed to build before flying) vents (any) -> really quicker inflation in phase 1) reducing the loss of altitude during this phase. the inflation also begins earlier when the canopy is still expanding open vents (no valves) -> maybe slowing down last inflation phase in 3) but probably not noticeable Anyone could try to evaluate the relative duration of each phase? (probably they arent practically clearly separated, mostly because the forward motion depends on when you pop the brakes and how you set them) any comment or stupid joke appreciated : ) L.

Winglets are especially efficient on low aspect ratio, rectangular wings (the relative effect of vortices is bigger on low a/r wings). On modern paragliders, due to the high aspect ratio, the relative improving of performance due to additional stabs would be less significant (but Advance make some upper surface inflated stabs on their wings, probably just to differ from others). Moreover, the elliptical shape tend to minimize the vortices. If you follow the evolution of paragliders, you'll find that the stabilisers are in fact now totally integrated on the wing. At first they were just like the stabs on base canopies, then they were vented (inflated) from the inside, and are now the closed cells on wingtips. Take a look at the great 1990 Pro Design (Mcc Aviation) ... there was already vented canopies 15 year ago : )

Seriously, they act just as the winglets on some planes - they reduce the drag resulting of the vortices on wingtips. They are also supposed to help your wing staying perpendicular to the relative wind direction (ie avoiding to slide while turning)