Thermals - zero zone

[Mousson]

Hi,

As a newbie I have learned to find those strong inverse toilet bowl type thermals, the same type Seagulls use to spiral up in the afternoon.

More often, I see them just glide straight (not flapping their wings), neither going up or sinking (french pilots call this area the zone zero). They can go a long distance that way. This happens mostly early in the day or just before sunset. Are they riding any type of non spiral thermals ?

When flying, is there any way to know your RC glider just enter such an area and what would be the tactic to use to maximize gliding time ?

Thanks

[Ollie]

There are two types of more or less continuous lift larger than a single thermal.

One is easily identified by long columns of cumulus clouds aligned with the wind and spaces of blue sky between the cloud streets. There is a long line of more or less continuous lift under each line of clouds and sink under the lines of blue sky between.

The other is at the interface between a warm air mass and a cold air mass in collision. The cold air mass slides under the warm air mass creating a line of lift perpendicular to the wind direction. This can be very violent as in a squall line or more gentle as in a sea breeze developing in the afternoon. Here in SW Florida the sea breeze can often produce wide spread lift that persists for as much as an hour. It happens when the wind during midday is off shore but reverses direction in the afternoon with the warm inland air meeting the cooler air from the Gulf of Mexico.