Any sailplane pilots?

In the Jan. 2004 issue of Model Aviation, in the Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes a "condensation
analogy" to suggest places to look for thermals to trigger. Imagine water
condensing on a ceiling: it drips first from the low spots or tiny bumps.
Now imagine heated, but relatively stable, air along the ground. If it's
"trying" to rise, might it not "drip up" first from the higher spots, little
hills, even trees? If it's moving slowly horizontally, and encounters a tree
line, it might be forced up enough to trigger a thermal. His experience with
models supports the theory on the small scale. Does y'all's experience
support it at the larger scale?

Roger Worden

Same thing with sandy areas - the books say to avoid them like the
plague, but the sandy washes here in Arizona are also consistent
thermal sources - and like the ponds/tanks, are low discontinuities in
the local terrain. In this case, I'm sure it's not the sand that is
causing the thermal, my uneducated guess is that the wash channels (or
collects) the incipient themal until it gets big and strong enough to
break loose.

Any Real Smart Guys out there care to give us a serious possible
explanation for these effects? - or maybe we need to keep this to
ourselves and let the youngsters figure it out for themselves! Got to
keep a few tricks in our bags, you know, something about age and
experience beating youth and skill...

Kirk

What you are sying is just about what Reichman says about low level
thermal activity.
I did some exercises in a Ka6 (good short landing glider)
having a ceiling of 1300ft (I left on track at 1300ft) from takeoff point
and
over several flights did a 50km ,65kms ,and 102 kms triangles .
I was prepared to land out but never had to.
Sometimes I would have to drift off track = 10 kms but I kept to the plan.
I spent a lot of time between 300-800ft agl but still made good times for
that
type of soaring. (When I was competing in later years it was a good way to
burn off leeching pilots) It did no harm to my placings as I got 2 day
placings
of 3rd and finished 5th overall in that nationals.
It was a fantastic learning experience..
If your terrain is suitable and you are confident of your ability to short
land
the glider you should do this exercise ,you will learn a lot.
gary



"Roger Worden" wrote in message
m...
In the Jan. 2004 issue of Model Aviation, in the Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes a "condensation
analogy" to suggest places to look for thermals to trigger. Imagine water
condensing on a ceiling: it drips first from the low spots or tiny bumps.
Now imagine heated, but relatively stable, air along the ground. If it's
"trying" to rise, might it not "drip up" first from the higher spots,
little
hills, even trees? If it's moving slowly horizontally, and encounters a
tree
line, it might be forced up enough to trigger a thermal. His experience
with
models supports the theory on the small scale. Does y'all's experience
support it at the larger scale?

Roger Worden

Same thing with sandy areas - the books say to avoid them like the
plague, but the sandy washes here in Arizona are also consistent
thermal sources - and like the ponds/tanks, are low discontinuities in
the local terrain. In this case, I'm sure it's not the sand that is
causing the thermal, my uneducated guess is that the wash channels (or
collects) the incipient themal until it gets big and strong enough to
break loose.

Any Real Smart Guys out there care to give us a serious possible
explanation for these effects? - or maybe we need to keep this to
ourselves and let the youngsters figure it out for themselves! Got to
keep a few tricks in our bags, you know, something about age and
experience beating youth and skill...

Kirk

Just about 100%. I don't think this is so much a theory as an analogy.

Ian


"Roger Worden" wrote in message
m...
In the Jan. 2004 issue of Model Aviation, in the Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes a "condensation
analogy" to suggest places to look for thermals to trigger. Imagine water
condensing on a ceiling: it drips first from the low spots or tiny bumps.
Now imagine heated, but relatively stable, air along the ground. If it's
"trying" to rise, might it not "drip up" first from the higher spots,
little
hills, even trees? If it's moving slowly horizontally, and encounters a
tree
line, it might be forced up enough to trigger a thermal. His experience
with
models supports the theory on the small scale. Does y'all's experience
support it at the larger scale?

Roger Worden

Same thing with sandy areas - the books say to avoid them like the
plague, but the sandy washes here in Arizona are also consistent
thermal sources - and like the ponds/tanks, are low discontinuities in
the local terrain. In this case, I'm sure it's not the sand that is
causing the thermal, my uneducated guess is that the wash channels (or
collects) the incipient themal until it gets big and strong enough to
break loose.

Any Real Smart Guys out there care to give us a serious possible
explanation for these effects? - or maybe we need to keep this to
ourselves and let the youngsters figure it out for themselves! Got to
keep a few tricks in our bags, you know, something about age and
experience beating youth and skill...

Kirk

"K.P. Termaat" wrote in message . ..
I think your way of thinking is correct. I have an equivalent experience for
wooded areas. During the day they do not work well, but at dawn when the
environment is cooling down they give off their accumulated heat and produce
thermals.

Karel, NL


I expect 99% percent of those reading this will realize *dawn* was
probably a translation error, but just in case, I think you meant
*dusk* or evening.


Andy (GY)

From my experience it appears possible for thermals
to form over and rise from a body of water. In the
past I have done a great deal of hang glider ridge
soaring on the Eastern edge of Lake Michigan. The ridge
is a steep sand bluff about 300-400 feet high right
on the edge of the water. The water is so close that
at some points it touches the base of the bluff. The
lake at this point is about 80 miles wide. On rare
occasions during light winds just capable of sustaining
flight we would encounter what were believed to be
thermals. The water would be almost perfectly flat
and you could see circular disturbances on the surface
moving towards shore at wind speed. When they hit the
bluff you could circle up and drift back over the ridge.
Our only explanation was clouds that caused uneven
heating on the surface of the water were creating the
thermals.

"Roger Worden" wrote in message om...
In the Jan. 2004 issue of Model Aviation, in the Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes a "condensation
analogy" to suggest places to look for thermals to trigger. Imagine water
condensing on a ceiling: it drips first from the low spots or tiny bumps.
Now imagine heated, but relatively stable, air along the ground. If it's
"trying" to rise, might it not "drip up" first from the higher spots, little
hills, even trees? If it's moving slowly horizontally, and encounters a tree
line, it might be forced up enough to trigger a thermal. His experience with
models supports the theory on the small scale. Does y'all's experience
support it at the larger scale?

Roger Worden


Yes it seems to work that way. A moving object may also disturb
motionless hot air and start a thermal. I was once low over a local
dirt strip, I think turning base to land, when a truck drove into a
large flat dirt area. It triggered a good thermal that got me up and
home.


Andy (GY)

"Andy Durbin" wrote in message
om...
"Roger Worden" wrote in message
om...
In the Jan. 2004 issue of Model Aviation, in the Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes a "condensation
analogy" to suggest places to look for thermals to trigger. Imagine
water
condensing on a ceiling: it drips first from the low spots or tiny
bumps.
Now imagine heated, but relatively stable, air along the ground. If it's
"trying" to rise, might it not "drip up" first from the higher spots,
little
hills, even trees? If it's moving slowly horizontally, and encounters a
tree
line, it might be forced up enough to trigger a thermal. His experience
with
models supports the theory on the small scale. Does y'all's experience
support it at the larger scale?

Roger Worden


Yes it seems to work that way. A moving object may also disturb
motionless hot air and start a thermal. I was once low over a local
dirt strip, I think turning base to land, when a truck drove into a
large flat dirt area. It triggered a good thermal that got me up and
home.
Andy (GY)

One thing to keep in mind is that there is a ratio between thermal triggers
and the heated air available to be triggered.

In other words, in weak conditions over rugged terrain, there is a surplus
of available triggers, but a deficit of heater air to be triggered.
Sometimes there will be no thermal over an obvious trigger site because the
available bouyant air was already triggered by a lesser, but adequate
trigger upwind. In these cases, potential trigger sites are not a reliable
thermal indicator.

In strong conditions, over mostly uniform, flat surfaces, the few available
trigger sites become more important.

Bill Daniels

Hi Andy,

Thanks for your correction. Meant "dusk" i.s.o. "dawn". Translation error
indeed. Though because of my work (american) english is about my second
language I made this slip of the pen.

Karel, NL


"Andy Durbin" schreef in bericht
om...
"K.P. Termaat" wrote in message
. ..
I think your way of thinking is correct. I have an equivalent experience
for
wooded areas. During the day they do not work well, but at dawn when the
environment is cooling down they give off their accumulated heat and
produce
thermals.

Karel, NL


I expect 99% percent of those reading this will realize *dawn* was
probably a translation error, but just in case, I think you meant
*dusk* or evening.


Andy (GY)

Yes I agree. Another example is big cities versus small ones.
I almost never find thermals over the larger areas of housings and buildings
belonging to a somewhat larger urban area. Just to many trigger points
producing small and low thermals only. However when over a village or a
group of farm housings it is usually very easy to find the spot where good
thermals are triggered off using the heated air of the direct environment.

Karel, NL


"Bill Daniels" schreef in bericht
hlink.net...

"Andy Durbin" wrote in message
om...
"Roger Worden" wrote in message
om...
In the Jan. 2004 issue of Model Aviation, in the Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes a "condensation
analogy" to suggest places to look for thermals to trigger. Imagine
water
condensing on a ceiling: it drips first from the low spots or tiny
bumps.
Now imagine heated, but relatively stable, air along the ground. If
it's
"trying" to rise, might it not "drip up" first from the higher spots,
little
hills, even trees? If it's moving slowly horizontally, and encounters
a
tree
line, it might be forced up enough to trigger a thermal. His
experience
with
models supports the theory on the small scale. Does y'all's experience
support it at the larger scale?

Roger Worden


Yes it seems to work that way. A moving object may also disturb
motionless hot air and start a thermal. I was once low over a local
dirt strip, I think turning base to land, when a truck drove into a
large flat dirt area. It triggered a good thermal that got me up and
home.
Andy (GY)

One thing to keep in mind is that there is a ratio between thermal
triggers
and the heated air available to be triggered.

In other words, in weak conditions over rugged terrain, there is a surplus
of available triggers, but a deficit of heater air to be triggered.
Sometimes there will be no thermal over an obvious trigger site because
the
available bouyant air was already triggered by a lesser, but adequate
trigger upwind. In these cases, potential trigger sites are not a
reliable
thermal indicator.

In strong conditions, over mostly uniform, flat surfaces, the few
available
trigger sites become more important.

Bill Daniels

As regards cities I think it depends...

I once went on a lead and follow course with Andy Davis
in blue or partially blue weather. In briefing before
flying he would nominate where he was planning to take
climbs. In the case of larger towns and cities (Bath,
Worcester and Swindon come particularly to mind) he
specified where the best thermal source would be and
would then take us there as low as possible. If a
strong core wasn't there when we arrived he parked
us in weak lift and nosed around until he found the
next strong pulse. It seemed odd at first to take
so much time to do that but it was worth it because
he had saved so much more time by ignoring weak lift
in the cruise to reach his nominated best thermal source
with the minimum of delay and at an altitude low enough
to take best advantage of the good climb.

So I think that cities will be likely to have at least
one source that is better than the multitude of little
trigger points

John Galloway

At 21:24 04 January 2004, K.P. Termaat wrote:
Yes I agree. Another example is big cities versus small
ones.
I almost never find thermals over the larger areas
of housings and buildings
belonging to a somewhat larger urban area. Just to
many trigger points
producing small and low thermals only. However when
over a village or a
group of farm housings it is usually very easy to find
the spot where good
thermals are triggered off using the heated air of
the direct environment.

Karel, NL


'Bill Daniels' schreef in bericht
thlink.net...

'Andy Durbin' wrote in message
om...
'Roger Worden' wrote in message
news:...
In the Jan. 2004 issue of Model Aviation, in the
Radio Control Soaring
column, Real Smart Guy candidate Mike Garton proposes
a 'condensation
analogy' to suggest places to look for thermals
to trigger. Imagine
water
condensing on a ceiling: it drips first from the
low spots or tiny
bumps.
Now imagine heated, but relatively stable, air along
the ground. If
it's
'trying' to rise, might it not 'drip up' first from
the higher spots,
little
hills, even trees? If it's moving slowly horizontally,
and encounters
a
tree
line, it might be forced up enough to trigger a
thermal. His
experience
with
models supports the theory on the small scale. Does
y'all's experience
support it at the larger scale?

Roger Worden


Yes it seems to work that way. A moving object may
also disturb
motionless hot air and start a thermal. I was once
low over a local
dirt strip, I think turning base to land, when a
truck drove into a
large flat dirt area. It triggered a good thermal
that got me up and
home.
Andy (GY)

One thing to keep in mind is that there is a ratio
between thermal
triggers
and the heated air available to be triggered.

In other words, in weak conditions over rugged terrain,
there is a surplus
of available triggers, but a deficit of heater air
to be triggered.
Sometimes there will be no thermal over an obvious
trigger site because
the
available bouyant air was already triggered by a lesser,
but adequate
trigger upwind. In these cases, potential trigger
sites are not a
reliable
thermal indicator.

In strong conditions, over mostly uniform, flat surfaces,
the few
available
trigger sites become more important.

Bill Daniels