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Sep 08, 2015, 08:23 AM
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on thermals and stranger things


i have been an enthusiast about flying on thermals, since my days of free flight, and now more with sailplanes, radio and vario at my hand am having the time of my life.
i have been compiling data on the subject, and as i said, with the aid of the vario am learning still more about them.
as far as i knew, thermals form from the ground and rise to the condensation level and become clouds. their shape could be bubbles or a column.
but now on clear sky am getting some lift that i find in areas like waves that run across, like some clouds that are lines that run parallel. this i 'see' because am using a vario that sends beeps when the plane climbs.
has any1 experienced this?
is there any link about this?
for more details i started a thread here:
https://www.rcgroups.com/forums/show....php?t=2487246
and if you have any info please bring it here.
Last edited by phil alvirez; Sep 10, 2015 at 05:34 PM.
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Sep 08, 2015, 04:42 PM
greg
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in general, the sun heats the ground and the ground warms the air. Air temp at ground level is assumed to be at ground temperature and cools as the dry adiabatic lapse rate

there are at least three sources of lift: thermals, ridges lift due to wind perpendicular to the ridge and wave.

see the thermal soaring forecast methodology page for a discussion and equations for determining cloud base from surface temperature and dew point.
Sep 08, 2015, 09:04 PM
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thank you very much for the links. will see them.
Oct 15, 2015, 02:51 PM
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conclusions


i have been flying in waves long enough to understand their behaviour at this field. it is in a flat area all over, some 5 km north of lake erie, and the prevailing wind blows from the lake too.
and the great thing is that i have the vario that sends tones and switching i can get height too, so it is as if they were colored clouds. no guess work. with this i have been able to learn:
1.-they are found on a line across the wind;
2.-climbing to 200 meters is where i find them;
3.-at this height they don't move. are stationary for a long time;
4.-if i climb to 300 meters i find thermals that drift with the wind:
5.-this happens even in clear sky;
6.-usually waves are located around a slope or mountain range but as i see, also at flat surfaces;
7.-so this means that even if waves are stationary, thermals can drift above them.
8.-this does not happen in many places; it takes some sort of special situation like the 1 i find at this specific place;
9.-but as i said, it is necessary to have a vario like mine that tells height and sends tones that tell if the plane is climbing (and how fast depending of the pitch and frecuency of the tones) to pinpoint their location.
anyway, a most rewarding experience-and all this new to me.
i only catched thermals all my life and had no idea of waves until now.
i hope this is of some use to you guys that enjoy staying up without a motor running.


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