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Wind strength


matt_k
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Wind at ground level is probably the deciding factor, along with the trim speed of your wing (usually about 18mph) for safe launches & landings. Even if the wind speed is higher with altitude you can use trimmers or speed bar to make progress in smooth 25 mph laminar air no problem, or fly lower in the wind gradient.

Its usually the opposite for free flying (on UK hills) as you can safely reverse launch in 18-20 mph winds knowing that it will probably only be 10-14 mph once you are out of the 'compression zone' at launch.

Saying that, I'm a wuss with the motor and tend to launch when the wind is in single figures (on ground). Its one thing getting dragged with a nice airbag / foam protection harness on the hill, but not with a fragile, heavy & expensive motor on your back ! :lol:

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Its usually the opposite for free flying (on UK hills) as you can safely reverse launch in 18-20 mph winds knowing that it will probably only be 10-14 mph once you are out of the 'compression zone' at launch.

Compression Zone??? The venturi effect that you sometimes get on the hill is not a ‘compression zone’. The venturi effect actually lowers the pressure and increases the wind. Sorry to be pedantic but this is often incorrectly called a compression zone. and that is confusing.

Paul D

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Its usually the opposite for free flying (on UK hills) as you can safely reverse launch in 18-20 mph winds knowing that it will probably only be 10-14 mph once you are out of the 'compression zone' at launch.

Compression Zone??? The venturi effect that you sometimes get on the hill is not a ‘compression zone’. The venturi effect actually lowers the pressure and increases the wind. Sorry to be pedantic but this is often incorrectly called a compression zone. and that is confusing.

Paul D

Surly if the wind was being sucked over the hill then you would get a Venturi effect (as in a carb.)

but with the wind blowing on to the hill and being forced up and over it is compressed between the hill and the air above

thus causing the wind to back up/ build enabling you to fly farther out in front of the ridge, if it was a Venturi effect you would not get this!!!!!!!!

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Surly if the wind was being sucked over the hill then you would get a Venturi effect (as in a carb.)

The carb doesn't work from the engine suction - that just pulls air through it. It is the narrow venturi that causes the air to speed up, lowering pressure and thus drawing fuel through the jets.

but with the wind blowing on to the hill and being forced up and over it is compressed between the hill and the air above

thus causing the wind to back up/ build enabling you to fly farther out in front of the ridge, if it was a Venturi effect you would not get this!!!!!!!!

its certainly easier to visualise it as water flowing against and over a rock in a river, although Bernoulli wouldn't be too happy about it .... :D

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Jesus!!! i only wanted to know what wind strengths other people flyin!!!

Well I'm getting so desperate to fly that I'll take any wind up to 20mph providing its not (a) raining, (b) dark, © raining again ...

So where is the compression zone again?

According to the BHPA, here:

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Practise your ground handling in higher winds with a normal harness first with trims out, but make sure you are safe in case you get dragged

Yes but if handling in strong wind on a hill, be aware of the 'Zone of accelerated air flow' which you may find close to the hill (previously wrongly called the compression zone)

Paul D

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