Any sailplane pilots?

The "standard" is to circle to the left. Usually this is a must near glider
airfields, especially with a competition going on. This is for safety
reasons.
While on x-country and joining other gliders, the circle direction is given
by these other gliders in the same thermal.
When alone and hitting a thermal, the direction to turn into is where you
suspect the thermal to be. Some experience is required for that. It always
makes sense to circle towards the direction of rotation of the thermal if
there is any rotation. Some pilots have the idea that 2/3 of the thermals
rotate counter clockwise looking from below. I have the idea that this may
be true, but only at low altitudes. That's why quite a lot of pilots, and I
am one of them, circle to the right when low. Some other pilots think that
there is no rotation at all, except in very narrow dust devils which are
unsuitable to fly in.

Karel, NL
"William W. Plummer" schreef in bericht
news:gCWHb.163786$8y1.490686@attbi_s52...
I didn't receive any direction about which way to circle. Common sense
would rule out going against the traffic in an established pattern.

If there is a "standard" I wonder if it is related to the default for
holds
(right) in airplanes. I used to wonder why the default for holds is to
the
right but the default for VFR patterns at airports is left. --Bill



"Casey Wilson" wrote in message
...

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


The protocol I was taught was that unless you are first into the
thermal, you follow the left or right pattern of the gliders already
there.
I've never had a preference of right or left. I was taught to turn
into
whichever wingtip went up.
I was also taught that the most efficient technique, that is the
highest rate of altitude gain, is in a 45-degree bank turn hopefully
"coring" the thermal.
Up here in the Mojave Desert flying out of IYK, I've been in a
couple
of
10 Knot thermals but 5 to 6 is the most common. I can't ever remember
any
kind of cyclonic rotation of any of them.
That said, I did once, inadvertantly fly into a dust-devil. I NEVER
want
to do that again. If I had seen any dust indication that it was there I
would definitely have avoided it in the first place.

"K.P. Termaat" wrote in message ...
My experience is that it works, especially on days with very low humidity,
but no boomers and only low.


"Mike Rapoport" schreef in bericht
ink.net...

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


Have to disagree with you, Mike - out here in Arizona, in the desert
areas that are not irrigated, we often find good lift directly over
small cattle "tanks" - small shallow ponds that are scattered around.
A lot of us have noticed this and compared notes, and it works; if too
low to get to high, dark ground, I'll head for the nearest pond and it
will usually turn up a nice thermal. We think it may be due to the
fact that the ponds are in a natural low spot, and coupled with the
little bit of moisture, could be the necessary trigger for a thermal.

Now obviously, large irrigated farm fields or river basins are death
to thermals - but a local lake (reservoir) seems to have little effect
on thermal activity - could it be all the drunk boaters?

What's the old saying about never saying never?

Kirk
LS6-b

The moisture doesn't really help lift until the air is fuly saturated and
starts condensing releasing heat. Also, the air above the water is cooled
by evaporation and is cooler than the surrounding air. I will never say
never and I don't dispute your or others experience, but the explanation
doesn't make sense to me.

Mike
MU-2


"Kirk Stant" wrote in message
om...
"K.P. Termaat" wrote in message
...
My experience is that it works, especially on days with very low
humidity,
but no boomers and only low.


"Mike Rapoport" schreef in bericht
ink.net...

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


Have to disagree with you, Mike - out here in Arizona, in the desert
areas that are not irrigated, we often find good lift directly over
small cattle "tanks" - small shallow ponds that are scattered around.
A lot of us have noticed this and compared notes, and it works; if too
low to get to high, dark ground, I'll head for the nearest pond and it
will usually turn up a nice thermal. We think it may be due to the
fact that the ponds are in a natural low spot, and coupled with the
little bit of moisture, could be the necessary trigger for a thermal.

Now obviously, large irrigated farm fields or river basins are death
to thermals - but a local lake (reservoir) seems to have little effect
on thermal activity - could it be all the drunk boaters?

What's the old saying about never saying never?

Kirk
LS6-b

"Mike Rapoport" wrote in message link.net...


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


I hope you come and fly with us in Arizona some time. After a few
miles of cross country in the blue you may come to appreciate the
thermals triggered by the small ponds known as cattle tanks.

Been using them for over 15 years and no theororetical analysis will
convince me they dont work.


Andy (GY)

Mike Rapoport wrote:

The moisture doesn't really help lift until the air is fuly saturated and
starts condensing releasing heat. Also, the air above the water is cooled
by evaporation and is cooler than the surrounding air. I will never say
never and I don't dispute your or others experience, but the explanation
doesn't make sense to me.

Mike
MU-2

"Kirk Stant" wrote in message
om...
"K.P. Termaat" wrote in message
...
My experience is that it works, especially on days with very low
humidity,
but no boomers and only low.


"Mike Rapoport" schreef in bericht
ink.net...

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


Have to disagree with you, Mike - out here in Arizona, in the desert
areas that are not irrigated, we often find good lift directly over
small cattle "tanks" - small shallow ponds that are scattered around.
A lot of us have noticed this and compared notes, and it works; if too
low to get to high, dark ground, I'll head for the nearest pond and it
will usually turn up a nice thermal. We think it may be due to the
fact that the ponds are in a natural low spot, and coupled with the
little bit of moisture, could be the necessary trigger for a thermal.

Now obviously, large irrigated farm fields or river basins are death
to thermals - but a local lake (reservoir) seems to have little effect
on thermal activity - could it be all the drunk boaters?

What's the old saying about never saying never?

Kirk
LS6-b

Have seen similar effects over the small dams on farms here too. My idea is that the air over the
water cools by evaporating water out of the pond. In so doing it looses more heat and hence
contracts more (gets denser) than it gains buoyancy by water vapour increase, ie, it gets both
colder and denser overall than the surrounding surface air. As the dense pool of air becomes
greater, it spreads out, ie, sort of collapses on itself, and pushes out over the edges of the pond
/ dam, particularly down slope over the dam wall, creating a miniature equivalent of a valley wind
in the creek or down the slope, thus acting as a wedge trigger to lift the warm dry air off the
ground.

I am not disputing the facts, I am disputing the explanation.

Mike
MU-2


"Andy Durbin" wrote in message
om...
"Mike Rapoport" wrote in message
link.net...


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


I hope you come and fly with us in Arizona some time. After a few
miles of cross country in the blue you may come to appreciate the
thermals triggered by the small ponds known as cattle tanks.

Been using them for over 15 years and no theororetical analysis will
convince me they dont work.


Andy (GY)

Mike Rapoport wrote:

"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

As I just posted in the "water vapour" thread, I think you have it all back the front.
Have seen similar effects over the small dams on farms here too. My idea is that the air over the
water cools by evaporating water out of the pond. In so doing it looses more heat and hence
contracts more (gets denser) than it gains buoyancy by water vapour increase, ie, it gets both
colder and denser overall than the surrounding surface air. As the dense pool of air becomes
greater, it spreads out, ie, sort of collapses on itself, and pushes out over the edges of the pond
/ dam, particularly down slope over the dam wall, creating a miniature equivalent of a valley wind
in the creek or down the slope, thus acting as a wedge trigger to lift the warm dry air off the
ground.

On Mon, 29 Dec 2003 14:11:24 GMT, "William W. Plummer"
wrote in Message-Id:
gCWHb.163786$8y1.490686@attbi_s52:

I used to wonder why the default for holds is to the
right but the default for VFR patterns at airports is left. --Bill

That is how I found my best thermal ever. Flying my HP16T at a Region
8 contest in Eric's stomping grounds. It was about 2 hours into a 3
Hour post task and front started moving into the area. I decided that
getting home might score better than trying to make the minimum time
and landing out so I headed back to the airport under the cloud deck.
The Glide was totally smooth and I arrived back at the airport at
about 1500 AGL. (~3000MSL) on the far side of the airport the sun was
shining and I could see two large dust devils up on the hill from the
airport. As I approached closer dust devil I could see cheat grass,
tumble weeds and garbage bags floating around in it. I put my left
wing into the dust devil and turned hard left. My 10kt vario pegged. I
switched the scale to 20kts and it pegged again. It would occasionall
drop to as low as 16kts. I went from 3000MSL to 11000MSL in about 4
minutes averaging right at 20kts. I had to stop the climb due to cloud
bases. From there I did a final glide out to a turnpoint and back to
the airport to finish within a few minutes of the 3 hour minimum.
Looking out on the wing I could see cheat grass draped all along the
leading edge of the wing. I am sure it didn't due anything good to my
glide ratio. As I rolled to a stop at the airport all the Cheat grass
dropped off the wing onto the tarmac, which made for a great story
"There I was, so low that..."

Brian
HP16T



Eric Greenwell wrote in message ...
Casey Wilson wrote:

That said, I did once, inadvertantly fly into a dust-devil. I NEVER want
to do that again. If I had seen any dust indication that it was there I
would definitely have avoided it in the first place.

No dust, no dust devil! But, of course, the thermal can still be there.
Coming into one low can be dangerous, but up here in eastern Washington
State, we use them frequently, especially on blue days. They are usually
quite tame. Only the biggest are potentially dangerous, and then only
when "near" the ground (say, less then 1500 feet AGL).

What you are flying makes a difference, too: a 1-26 is going to be
tossed around a lot more than an ASW 20 with ballast. Flying faster than
the normal thermalling speed helps quite a bit if the thermal is rough.

On the other hand I can't tell you how many times(numerous) I
intercepted a dust devil at 1000-1500 AGL and climbed out at less then
1kt or even did not climb. Most times however I get 3-6 kts out of
them. I have see dust devils go to 7-8000 feet up. Hate to tell the
one gentleman this that wouldn't fly into a dust devil, but if he flys
using thermals he is just flying into dustless dust devils, As far as
I can tell the only difference is if it is lifting air over an area
were it can pick dust up or not.

Brian
HP16T



Eric Greenwell wrote in message ...
Casey Wilson wrote:

That said, I did once, inadvertantly fly into a dust-devil. I NEVER want
to do that again. If I had seen any dust indication that it was there I
would definitely have avoided it in the first place.

No dust, no dust devil! But, of course, the thermal can still be there.
Coming into one low can be dangerous, but up here in eastern Washington
State, we use them frequently, especially on blue days. They are usually
quite tame. Only the biggest are potentially dangerous, and then only
when "near" the ground (say, less then 1500 feet AGL).

What you are flying makes a difference, too: a 1-26 is going to be
tossed around a lot more than an ASW 20 with ballast. Flying faster than
the normal thermalling speed helps quite a bit if the thermal is rough.