Any sailplane pilots?

On Sun, 21 Dec 2003 06:00:30 GMT, "Chuck" wrote
in Message-Id: . net:

My cousin just bought a Schweizer 1 36 sailplane.

I've some experience with the Schweizer 1-26. It had an L/D of 30
IIRC. Do you know the L/D of the 1-36?
http://www.dfrc.nasa.gov/Gallery/Photo/Schweizer-1-36/

We took it to the airport today where he is going to hanger it today, and
put her together so the FAA could give the stamp of approval with the
airworthiness certificate.

Looks like the sailplane could be alot of fun.

It is a contest between the pilot and mother nature. The idea is to
spend more time in rising air than sinking air, and thus gain and
sustain altitude. The pilot must mentally visualize the movements of
the air masses in his vicinity, due to convective and orographic
vertical displacement, solely through interpreting instrument
indications and seat-of-the-pants cues.

The spectrum of soaring meteorological conditions ranges from flat
(little or no vertical movement of the air mass) to booming. During
the latter, the pilot is nearly unable to prevent his ship from
rising; it's like having a motor. On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.
Because this can require banks in excess of 60 degrees, occupants ware
a parachute. Such long, constant high-G circling can adversely affect
passengers of multi-place sailplanes, but the pilot will find it
exhilarating. The sport of soaring adds another dimension to similar
naturally powered sports such as sailing, surfing, and skiing...

I have never been around them before.

Just wondering how many guys fly gliders...


[newsgroup rec.aviation.soaring added]

Larry Dighera wrote:


The spectrum of soaring meteorological conditions ranges from flat
(little or no vertical movement of the air mass) to booming. During
the latter, the pilot is nearly unable to prevent his ship from
rising; it's like having a motor. On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.
Because this can require banks in excess of 60 degrees, occupants ware
a parachute. Such long, constant high-G circling can adversely affect
passengers of multi-place sailplanes, but the pilot will find it
exhilarating. The sport of soaring adds another dimension to similar
naturally powered sports such as sailing, surfing, and skiing...

Just in case you might get the idea from Larry that we all have our
blood at our feet from G loads, note that _most_ us use more like a 30
degree bank (g load hardly noticeable after a few flights), and can go
up just fine!

And for _most_ of us, wearing a parachute doesn't have anything to do
with circling in thermals. They aren't required except in contests, but
most private owners end up with one for various reasons, and wear it all
the time (sort of like wearing a seat belt in a car). Clubs aren't so
likely to use them while flying their gliders.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Larry wrote:

On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.

Why do you write "anticyclone" Larry. This would mean that all gliders would
circle righthanded to stay as close to the core as possible thereby using
the headwind of the thermal.
I have never found a meteorological reason to circle in a certain direction.
Most pilots circle lefthanded just because they were tought to do so in the
vicinity of their home field. However in x-country flights there is usually
no preference. In low situations the pilot usually circles in the direction
he feels most comfortable. Sometimes the gliders feels better when circling
to the right rather then to the left is my experience.

Karel, NL

"Eric Greenwell" schreef in bericht
...
Larry Dighera wrote:


The spectrum of soaring meteorological conditions ranges from flat
(little or no vertical movement of the air mass) to booming.

Eric Greenwell
Washington State
USA

On Fri, 26 Dec 2003 09:00:24 GMT, "K.P. Termaat" wrote
in Message-Id: :

Larry wrote:

On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.

Why do you write "anticyclone" Larry.

That was my recollection from my soaring experience in the early '70s.
However, it appears that the word 'cyclone' may have more correct now
that I have done some research:

The National Weather Service Glossary page here
http://www.wrh.noaa.gov/Phoenix/general/glossary/ has this to say:

ANTICYCLONE - A region of high atmospheric pressure around which
winds move in a clockwise direction in the northern hemisphere.
Generally associated with warm and dry weather

CYCLONE - An area of low pressure around which winds blow in a
counter-clockwise fashion in the northern hemisphere. Generally
associated with cool, wet and unsettled weather

On the other hand ...

This would mean that all gliders would circle righthanded to stay as close
to the core as possible thereby using the headwind of the thermal.

I'll defer to these sources:

http://www.rc-soar.com/tech/thermals.htm
Do thermals rotate?
They do, but not predictably. Even dust devils don't have a
preferred direction of rotation (see Stull, p.449). Thermals are
too small and too short-lived to be affected by the earth's
rotation (Coriolis force) or by the equator/pole thermal gradient.
Their rotation is determined by local terrain. Rotational velocity
in the core of a typical thermal is small compared to the vertical
velocity.


http://www.skynomad.com/articles/athermal10.html
THERMALS

Do Thermals Spin?
by Peter Gray

Of course, dust devils spin, so thermals probably do also, at
least when they're close to the ground. For many years, I was
convinced that dust devils rotated in random directions. However,
based on a few flights in northern Washington State, where I kept
more careful mental notes, I would guess that about 2/3 to 3/4 of
the dust devils there spin counterclockwise, in agreement with the
Coriolis Effect. Contrary to popular belief, the smaller-scale
equivalent, water going down a toilet or drain, is essentially
unaffected, and the rotation, if it is biased toward one spin
direction, is the result of the geometry of each such basin (check
it out for yourself!).

The dust devils formed by thermals seem to be just large
enough to be affected somewhat by the Coriolis Effect. If I have
the choice, I usually opt for circling against the dust devil's
rotation, most often to the right, in case this will produce a
better climb rate by reducing my circling ground speed, thus bank
angle and sinkrate.

However, when I have reversed direction several times in one
climb, I have rarely detected a significant advantage in one
direction. What little angular momentum thermals start with, they
seem to lose through drag in the surrounding air, and they
probably start with little spin anyway. As with water going down a
drain, very little spin momentum at a large radius can translate
to a rapid spin when the radius shrinks to that of a dust devil.

I have never found a meteorological reason to circle in a certain direction.
Most pilots circle lefthanded just because they were tought to do so in the
vicinity of their home field. However in x-country flights there is usually
no preference. In low situations the pilot usually circles in the direction
he feels most comfortable. Sometimes the gliders feels better when circling
to the right rather then to the left is my experience.

Karel, NL

Agreed. Circling direction is more often dictated by other gliders in
the thermal than meteorological phenomena and physics.

Thanks Larry for your interesting respons with your links to the articles.

As a matter of fact most members of our National Team (my son is one of
them) tend to circle to the right when low. They don't in effect know why.
They say, and I agree, that it usually feels better in getting up again. So
Peter Gray may be right in saying that most of the thermals have the
tendency to rotate to the left in the northern hemisphere, especially when
low when still having small diameters. Coriolis may be the cause then. Would
be interesting to know the experience in the southern hemisphere.

Talking about a drain and water brings me to the idea of telling that when
low and looking for a thermal I always try to locate small ponds in dry
areas. It looks to me that the water vapor rising from these ponds is an
excellent means of starting a thermal. Water vapor is lighter then air, so
it increases the boyancy of the air over the pond and off it goes. Starting
at about ground level, circling to the right may then generally be the
better option. Any experience with this Larry?

Karel, NL


"Larry Dighera" schreef in bericht
...
On Fri, 26 Dec 2003 09:00:24 GMT, "K.P. Termaat" wrote
in Message-Id: :

Larry wrote:

On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.

Why do you write "anticyclone" Larry.

That was my recollection from my soaring experience in the early '70s.
However, it appears that the word 'cyclone' may have more correct now
that I have done some research:

The National Weather Service Glossary page here
http://www.wrh.noaa.gov/Phoenix/general/glossary/ has this to say:

ANTICYCLONE - A region of high atmospheric pressure around which
winds move in a clockwise direction in the northern hemisphere.
Generally associated with warm and dry weather

CYCLONE - An area of low pressure around which winds blow in a
counter-clockwise fashion in the northern hemisphere. Generally
associated with cool, wet and unsettled weather

On the other hand ...

This would mean that all gliders would circle righthanded to stay as
close
to the core as possible thereby using the headwind of the thermal.

I'll defer to these sources:

http://www.rc-soar.com/tech/thermals.htm
Do thermals rotate?
They do, but not predictably. Even dust devils don't have a
preferred direction of rotation (see Stull, p.449). Thermals are
too small and too short-lived to be affected by the earth's
rotation (Coriolis force) or by the equator/pole thermal gradient.
Their rotation is determined by local terrain. Rotational velocity
in the core of a typical thermal is small compared to the vertical
velocity.


http://www.skynomad.com/articles/athermal10.html
THERMALS

Do Thermals Spin?
by Peter Gray

Of course, dust devils spin, so thermals probably do also, at
least when they're close to the ground. For many years, I was
convinced that dust devils rotated in random directions. However,
based on a few flights in northern Washington State, where I kept
more careful mental notes, I would guess that about 2/3 to 3/4 of
the dust devils there spin counterclockwise, in agreement with the
Coriolis Effect. Contrary to popular belief, the smaller-scale
equivalent, water going down a toilet or drain, is essentially
unaffected, and the rotation, if it is biased toward one spin
direction, is the result of the geometry of each such basin (check
it out for yourself!).

The dust devils formed by thermals seem to be just large
enough to be affected somewhat by the Coriolis Effect. If I have
the choice, I usually opt for circling against the dust devil's
rotation, most often to the right, in case this will produce a
better climb rate by reducing my circling ground speed, thus bank
angle and sinkrate.

However, when I have reversed direction several times in one
climb, I have rarely detected a significant advantage in one
direction. What little angular momentum thermals start with, they
seem to lose through drag in the surrounding air, and they
probably start with little spin anyway. As with water going down a
drain, very little spin momentum at a large radius can translate
to a rapid spin when the radius shrinks to that of a dust devil.

I have never found a meteorological reason to circle in a certain
direction.
Most pilots circle lefthanded just because they were tought to do so in
the
vicinity of their home field. However in x-country flights there is
usually
no preference. In low situations the pilot usually circles in the
direction
he feels most comfortable. Sometimes the gliders feels better when
circling
to the right rather then to the left is my experience.

Karel, NL

Agreed. Circling direction is more often dictated by other gliders in
the thermal than meteorological phenomena and physics.

Maybe it is simply an ergonomics thing --- I feel more comfortable
circling to the right in clutch situations simply because it is easier
to pull and adjust rather than push and adjust in right turns.

K.P. Termaat wrote:
Thanks Larry for your interesting respons with your links to the articles.

As a matter of fact most members of our National Team (my son is one of
them) tend to circle to the right when low. They don't in effect know why.
They say, and I agree, that it usually feels better in getting up again. So
Peter Gray may be right in saying that most of the thermals have the
tendency to rotate to the left in the northern hemisphere, especially when
low when still having small diameters. Coriolis may be the cause then. Would
be interesting to know the experience in the southern hemisphere.

Talking about a drain and water brings me to the idea of telling that when
low and looking for a thermal I always try to locate small ponds in dry
areas. It looks to me that the water vapor rising from these ponds is an
excellent means of starting a thermal. Water vapor is lighter then air, so
it increases the boyancy of the air over the pond and off it goes. Starting
at about ground level, circling to the right may then generally be the
better option. Any experience with this Larry?

Karel, NL


"Larry Dighera" schreef in bericht
...

On Fri, 26 Dec 2003 09:00:24 GMT, "K.P. Termaat" wrote
in Message-Id: :


Larry wrote:


On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.

Why do you write "anticyclone" Larry.

That was my recollection from my soaring experience in the early '70s.
However, it appears that the word 'cyclone' may have more correct now
that I have done some research:

The National Weather Service Glossary page here
http://www.wrh.noaa.gov/Phoenix/general/glossary/ has this to say:

ANTICYCLONE - A region of high atmospheric pressure around which
winds move in a clockwise direction in the northern hemisphere.
Generally associated with warm and dry weather

CYCLONE - An area of low pressure around which winds blow in a
counter-clockwise fashion in the northern hemisphere. Generally
associated with cool, wet and unsettled weather

On the other hand ...


This would mean that all gliders would circle righthanded to stay as

close

to the core as possible thereby using the headwind of the thermal.

I'll defer to these sources:

http://www.rc-soar.com/tech/thermals.htm
Do thermals rotate?
They do, but not predictably. Even dust devils don't have a
preferred direction of rotation (see Stull, p.449). Thermals are
too small and too short-lived to be affected by the earth's
rotation (Coriolis force) or by the equator/pole thermal gradient.
Their rotation is determined by local terrain. Rotational velocity
in the core of a typical thermal is small compared to the vertical
velocity.


http://www.skynomad.com/articles/athermal10.html
THERMALS

Do Thermals Spin?
by Peter Gray

Of course, dust devils spin, so thermals probably do also, at
least when they're close to the ground. For many years, I was
convinced that dust devils rotated in random directions. However,
based on a few flights in northern Washington State, where I kept
more careful mental notes, I would guess that about 2/3 to 3/4 of
the dust devils there spin counterclockwise, in agreement with the
Coriolis Effect. Contrary to popular belief, the smaller-scale
equivalent, water going down a toilet or drain, is essentially
unaffected, and the rotation, if it is biased toward one spin
direction, is the result of the geometry of each such basin (check
it out for yourself!).

The dust devils formed by thermals seem to be just large
enough to be affected somewhat by the Coriolis Effect. If I have
the choice, I usually opt for circling against the dust devil's
rotation, most often to the right, in case this will produce a
better climb rate by reducing my circling ground speed, thus bank
angle and sinkrate.

However, when I have reversed direction several times in one
climb, I have rarely detected a significant advantage in one
direction. What little angular momentum thermals start with, they
seem to lose through drag in the surrounding air, and they
probably start with little spin anyway. As with water going down a
drain, very little spin momentum at a large radius can translate
to a rapid spin when the radius shrinks to that of a dust devil.


I have never found a meteorological reason to circle in a certain

direction.

Most pilots circle lefthanded just because they were tought to do so in

the

vicinity of their home field. However in x-country flights there is

usually

no preference. In low situations the pilot usually circles in the

direction

he feels most comfortable. Sometimes the gliders feels better when

circling

to the right rather then to the left is my experience.

Karel, NL

Agreed. Circling direction is more often dictated by other gliders in
the thermal than meteorological phenomena and physics.

"K.P. Termaat" wrote in message
...
Thanks Larry for your interesting respons with your links to the articles.


Talking about a drain and water brings me to the idea of telling that when
low and looking for a thermal I always try to locate small ponds in dry
areas. It looks to me that the water vapor rising from these ponds is an
excellent means of starting a thermal. Water vapor is lighter then air, so
it increases the boyancy of the air over the pond and off it goes.
Starting
at about ground level, circling to the right may then generally be the
better option. Any experience with this Larry?

Karel, NL

You will find less lift over water of any kind, even if it is contained in
vegetation. The best lift is always over the highest, dryest, darkest
surface around. The water vapor idea is...well...it is hard to find a place
to start...but it won't work

Mike
MU-2

In message , Eric Greenwell
writes
Larry Dighera wrote:


The spectrum of soaring meteorological conditions ranges from flat
(little or no vertical movement of the air mass) to booming. During
the latter, the pilot is nearly unable to prevent his ship from
rising; it's like having a motor. On an average day, a pilot will
spend a great deal of time attempting to "core" thermals. That
involves mentally visualizing the sailplane's position relative to the
thermal's vertical anticyclone column center, and guiding his
sailplane to circle as near to the center of it as he is able.
Because this can require banks in excess of 60 degrees, occupants ware
a parachute. Such long, constant high-G circling can adversely affect
passengers of multi-place sailplanes, but the pilot will find it
exhilarating. The sport of soaring adds another dimension to similar
naturally powered sports such as sailing, surfing, and skiing...

Just in case you might get the idea from Larry that we all have our
blood at our feet from G loads, note that _most_ us use more like a 30
degree bank (g load hardly noticeable after a few flights), and can go
up just fine!

And for _most_ of us, wearing a parachute doesn't have anything to do
with circling in thermals. They aren't required except in contests, but
most private owners end up with one for various reasons, and wear it
all the time (sort of like wearing a seat belt in a car). Clubs aren't
so likely to use them while flying their gliders.

Don't know about the states but we use parachutes in everything. As far
as I know everybody does in the UK.

Robin
--
Robin Birch

In article , Robin Birch robinb@r
Don't know about the states but we use parachutes in everything. As far
as I know everybody does in the UK.

Robin

Everything except driving the tug.
--
Mike Lindsay

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