Raymond recently wrote:
> lift was good on a light wind day. zero lift on windy day.
> can anyone explain to me what happened?
Raymond,
What you experienced is not that unusual. And there are several reasons that
may be contributing to your disappointing flight.
At a given location, lighter wind may be much more laminar (that is smoother
and free of turbulence) than heavy wind. Turbulent, choppy, gusty wind is
much less likely to organize itself into a healthy, soarable ridge wave. By
contrast, the lighter, perhaps smoother wind will build up a very lovely,
consistent slope wave that may keep up a glider that will barely ascend in
the stronger choppier conditions. Ironic, but true.
Another common condition is that lighter winds are often created by a series
of warm (relative to the average ambient air temp.) thermal bubbles getting
pressed up against your slope and rising up along it. These thermal
'packets' behave alot like slope lift, but have the added energy of air that
is rising in part due to temperature differential, and so may produce much
more useable lift than a powerful front-driven airmass moving at much higher
speed.
For a slope to create powerful lift in high-speed wind, especially wind that
has no real local thermal component, the slope needs to be STEEP, otherwise,
big wind can be LESS useful than lighter winds. On a truly steep slope with
a defined edge, big wind really is an almost CERTAIN indicator of big lift,
but if the slope is mellower, or has a rounded top, the high-speed wind may
still have so much horizontal component that the useable band of lift may be
surprisingly narrow, and close to the surface, and a glider may spend most
of its flight energy penetrating and barely able to climb.
I suspect that this last reason plays the biggest role in your disappointing
recent experience, but not being familiar with the topography of the slope,
I can't be sure. It is also possible (again depending on the shape of your
slope) that there was more vertically oriented lift further out and away
from you, but that your glider was not able to penetrate far enough out to
make use of it. When you have flown many slopes in many conditions, you will
be better able to 'diagnose' the local lift.
In summary, lift is NOT a simple phenomenon. Ridge lift is perhaps the most
predictable of all lift, but sitll, many factors are at play in determining
the quality and 'soarableness' of the air.
Hope this is useful!
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
"unsubscribe" requests to [EMAIL PROTECTED]
