Perhaps NASA will help us with thermal locating. Quoting from a CNN article
currently at http://www.cnn.com/2004/TECH/space/0...vil/index.html
:
Dust particles in a devil become electrified because they rub against one
another. It's like shuffling your feet across the carpet, the researchers
explained. But they figured the positive and negative particles would be
evenly mixed in a dust devil, keeping the overall electrical charge in
balance.

Instead, it turns out smaller particles tend to gain negative charge, and
the wind carries them higher.

Heavier, positive particles remain nearer the surface. The separation of
charges creates a giant battery. And because the particles are in motion, a
magnetic field is generated by the moving electrical charges, the
researchers explained.

They don't yet know for sure what to expect on Mars.

If dust on the red planet comes in a variety of sizes and compositions, as
expected, then dust devils there ought to be similarly electrified, the
scientists said. NASA could equip a future Mars landing craft with an
instrument to detect a dust devil's electric and magnetic fields.

Mike Koerner

"iPilot" wrote in message
...
Actually for thermal marking purporses smoke would work pretty fine. But I
don't know any smoke machine which is small enough to fit to the glider
and
which is controllable. For aerobatics they just fit smoking cartridges
that
burn to the end after ignition, but thermal marking needs some repeatable
2
sec buffs of somke.
There's another problem with bubbles. The only reasonable place to put it
is
on top of the rear fuselage. But then you spill the vertical fin with wet
bubbles and this harms your L/D.

Regards,
Kaido



"Bill Daniels" wrote in message
news:t6ahc.33650$ru4.33232@attbi_s52...

"Wallace Berry" wrote in message
...


So, would your idea work? I proved it would but all that heavy gear
will be
pretty hard to get into a glider. Throwing out bits of toilet paper
probably works better. Hmmm, Lets see.....what would a toilet paper
dispensing machine look like...

Bill Daniels



Someone beat you to it. Ted Teach had a 1-26 with a toilet paper
dispensing mechanism in the turtledeck. It was a little trapdoor with
a
cutting edge. Open the door and toilet paper unrolled into the
slipstream. Close the door and it severed the paper. Repeatedly
opening
and closing the door supposedly dispensed tp chaff to be followed as a
thermal marker. Teach's 1-26 also had a reprofiled nose and canopy and
doors that enclosed the landing gear (retractable gear being against
the
rules in 1-26 racing. Mark Connor later had this 1-26 and was undoing
all the "Teachisms" on it.

In all seriousness, the bubble experiments produced some very good
insights
in low level convective airflow. Neutrally buoyant bubbles have no
aerodynamic qualities of their own so if they are seen to move, it is
because airflow is pushing them. Bits of paper and other debris do have
some aerodynamic qualities so the data is corrupted. Up to that point
there
were several studies that used smoke, but that can't be analyzed
numerically. Discrete bubbles provided a means to measure speed and
direction of airflow in 3D to high precision.

Later, larger scale experiments with Mylar balloons were even more
interesting. First pairs would be released and tracked for many miles
by
radar. Eventually, large numbers of these balloons were released
simultaneously along a crosswind line in thermic conditions and watched
by
radar as they traced out thermal streets.

Today, most work of this kind is done with LIDAR (Laser Radar) which can

track naturally occurring tiny aerosols of pollen and dust revealing the
3D
structure of airflow with great precision over a large area in real
time.

Now, putting a LIDAR in a glider WOULD be interesting.

Bill Daniels