Basejumper.com - archive

seriously, i need to know the point of these fabric labias.

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)

Good question. My JVX swooping canopy doesn't have them and I've got plenty of terminal as well as sub-terminal openings on the JVX without too many issues. Now a BASE canopy could be a different story when it comes to the openings. I just don't know enough about BASE canopies (shit I don't know enough about canopy designs period) to know if jumping a BASE canopy without stablizers is a good idea. But once again, I don't have stablizers on my skydiving swooping canopy.

aerodynamically, elliptical wings minimize wingtip vortices, enhancing the wings efficiency. the narrow wingtip also reduces any advantages of stabilizers.

big, rectangular BASE canopies can benefit from stabilizers.

do not know if they are critical...

http://www.surfplan.com.au/sp/
I highly recommend this site and download.
take care,
space

One of the bigger things they do is on slider up jumps you have a place to put slider stops, keeping the grommet from pushing up over the line loops and onto the canopy fabric.

ok, i know they act as inverted winglets, but what do they do for opening? and WHY are they called stabilisers? i originaly thought they were for yaw stability. paragliders do not have them, (well, at least most of them) pataglider wingtips curve down a lot more though. i can see the point that it is a good place to stop the slider. but what wouldt the problem of letteing the rear of the slider com all the way up to the canopy with the washers placed there? i bet with no stabilisers there would be less offheading openings from the linestretch end of it. it would also be easier to pack.

In my opinion, they don't do anything for the opening.

Our parachutes have two different functional modes. At first they act as aerodynamic decelerators (basically giant air brakes, like round parachutes) to stop us falling toward the ground. Then, they transition to acting as wings (like paragliders) to fly us to our landing area (and land us softly).

My understanding is that the stabilizer is supposed to prevent air from "slipping" around the side of the parachute when it is flying as a wing. This ought to make it fly more efficiently, and yield "crisper" toggle response when turning.

I dunno. I've got a couple really old canopies around. maybe I'll try slicing the stabilizers off one and seeing if it changes the way it flies.

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 : )

Flight Concepts reserve does not have stabilizers.

The recent designs (Omega 7 etc.) only have negligible "ears" any more, because - as you said - the ears always have been rather a marketing ploy than an aerodynamically sound construction. Probably they do not have any effect or even hurt performance, and I guess this is why they cut the ears of on newer designs...

Given you extensive knowledge in parachute design, construction, and the greater field of fluid dynamics I will chop off the stabilizers off all my tarps.

Agreed, i design Radio Control sailplanes that i have used in competition, and the winglets i haveput on the wingtips work for the same benefit as stabilisers on a big square (read:disgustingly low aspect ratio) canopies, but do it only on the airflow on the bottom side of the wing. winglets on the top surface of wings are there to keep the air above the wing at a low pressure, in effect they increas the aspect ratio of said wing. being that the glide ratio of a BASE canopy is hopeless anyway, originaly the stabs were probably to improve glide, but the canopy has a huge anehedral to it. i would love to see Tom cut the stabs off one of his old tarps. that would be sweet. i bet it does help the flare a lot.

thanks kids.