? for ground launchers

[freeflight 0]

if a wind is directly uphill, does it act the same way as a wave coming to the shoreline? and if it does, at what speed does it begin to be unfreindly to a flying canopy? i understand that slope angle might be a factor in this as well.
also, is there anyone who published anything on this subject(for free that is) on the web anywhere?

any input is greatly appreciated.

[ChangoLanzao 0]

The short answer is no.

A wave coming on shore is mostly affected by gravity. The wind moving towards a hill is not. Wind going up a hill is a completely different model and the amount of turbulence is mainly determined by factors such as wind speed, surface features, and convection.

Note: I'm not a fluid dynamics expert, but I DID stay at a Holidy-Inn Express last night


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[airtwardo 6]

Note: I'm not a fluid dynamics expert, but I DID stay at a Holidy-Inn Express last night


~That just happened to be on a HILL!

~ If you choke a Smurf, what color does it turn? ~

[billvon 2,380]

>if a wind is directly uphill, does it act the same way as a wave coming to the shoreline?

No. It does not 'break' if that's what you mean. It keeps going up.

>and if it does, at what speed does it begin to be unfreindly to a
>flying canopy?

It's not too different from the sort of winds you might find at a DZ. If it's a flat gradual slope, there will be few problems. If winds are gusty, or strong, and/or there are trees and other obstacles below you, you may have problems.

Dennis Pagen has two excellent books - "understanding the sky" and "the art of paragliding" - that go into this in very great detail. For online sources I'd search under paraglider launch.

[tdog 0]

Quote

if a wind is directly uphill, does it act the same way as a wave coming to the shoreline? and if it does, at what speed does it begin to be unfreindly to a flying canopy? i understand that slope angle might be a factor in this as well.
also, is there anyone who published anything on this subject(for free that is) on the web anywhere?

any input is greatly appreciated.

I learned to fly a paraglider off a mountain before this skydiving thing. I am no expert, but I know the basics. 1st, there are great books on paragliding that really do apply 100% to ground launching canopies. 2nd, a paraglider instructor or even a 1st flight course would really do ya some good…

But, the basics are – winds are so unpredictable you need to have wind indicators at the bottom and top of the hill. The one on the top should be as close to the peak of the hill as possible. You know NOTHING until you know what the winds are actually proven to do, because chaos does exist in this world.

You want both the top and bottom windsock pointing nearly the exact same direction, and uphill, preferably not flopping around left to right as if the air is unstable, but solid and in the same direction. The reason is, it is very common for the winds to rotor around the top of the mountain and see the winds appear to be going uphill at the bottom and mid point, but really have a downhill wind instead at the top. This will kill you. The only way to fly up there safe is to know the winds are truly going uphill and over the top. You always fly on the uphill wind side of the mountain with the winds on the ground, the winds at the peak, and the winds a thousand feet above the peak all going the same way uphill.

Yes, there are huge rotors on mountains. You never want to be over the top of the mountain, and especially never behind the leeward side – because the rotors will be more intense than you can imagine. Take the rotor off a hangar on flat ground and make it much worse. The rotor could run the whole back side of the hill. If you get blown back over the top and have to pass over the top to get back, be hundreds if not thousands of feet over the top, or fly with the wind and land somewhere far away. The area on the “down hill” wind side of the mountain, near the top, is very deadly.

The fact the winds are forced up as they push against the mountain gives canopies lift. It is common for a paraglider to run sideways real close to the mountain hoping to get the lift they need to find a thermal. Some places never get thermals, but the mountain/cliff is so good at changing the winds to make them go up that you never have to land until you want to…

Check out Dixon White’s info on http://www.paraglide.com/DixonsNotes06.html and the other pages too on that site in addition to the books mentioned. Dixon While was the Brian Germain of paragliding until he died of natural causes at a young age.