From the Thermalier, newsletter of the Pensacola Free Flight Team
Picking Thermals
An article by Peter Brocks, which is stolen here
from the November 2001 Ontario-based
Sam 86 Speaks,
who in turn stole it from the August 2001
Bat Sheet.
Picking thermals has to do with feeling the subtle
changes in the environments, which, to the
untrained, are not apparent. Therefore there is no
simple recipe.
Tools:
Mylar streamers, fast sampling thermistor devices,
fluffies, bubble machines, piggybacking (on) birds,
and other models.
Early
morning:
The air is buoyant neutral, small rises in
temperature possible (as little as 2° F).
Midday:
Strong thermals (boomers) develop that exceed the
sink rate of models, rise in temperature can be a
few degrees with wind calming, wait until a cooler
breeze (fill) is felt and the temperature clearly
drops. Do not launch right away, especially with
fast, higher climbing models. Wait 10 to 20 seconds,
depending on wind velocity.
Late
Afternoon:
Thermals stay closer to the ground, tend to be
larger size. Smaller rises in temperature (1°+ F).
Be patient; fly over dark areas.
Strong wind:
Wait for a three- or four-second lull of lower wind
velocity; launch immediately at an angle to the
wind.
No wind:
Watch streamers to see center of building hot air
column. The rising air circles counterclockwise.
Wait for light air movement indicating fill. Be
patient as the air rises very slowly.
When launching, place the model in the center of the
rising air.
Cold front:
Rising air precedes the rain and the breeze. Good
air is still present even when rain starts.
Flapping:
If wind is moderate and ground surface is warm, then
flapping a shirt or running or driving under the
model will release rising air.
General
Rules:
Do not launch if there is a chance that the sun
might soon come out of the clouds. Do not fly if
other models are launched when a conscientious
decision to launch has not been made; rather watch
other models behavior. Most of the time flying a
little later will give better results. Concentrate
and take in your environment.
Q
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