Any sailplane pilots?

(Kirk Stant) wrote in message . com...
"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 adiabatic rate of moist air is about 1.5C/1000ft. For dry air it
is 3C/1000ft. Therefore, assuming that the water temperature is the
same as the surrounding ground (which would be true if the water is
shallow), I could see how one will experience greater lift above
water.

"Andrew Sarangan" wrote in message
om...
(Kirk Stant) wrote in message
. com...
"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 adiabatic rate of moist air is about 1.5C/1000ft. For dry air it
is 3C/1000ft. Therefore, assuming that the water temperature is the
same as the surrounding ground (which would be true if the water is
shallow), I could see how one will experience greater lift above
water.

Not for unsaturated air it isn't. The moist rate only applies to saturated
air (ie in clouds)

Mike
MU-2

"Brian Case" wrote in message
om...
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.

We are apparently sharing different definitions of "dust devils." The
ones that rage across the part of the country I fly mostly do not fit the
structure of a thermal.
Thermals, at least where I am, are rising volumes of air created by
differential temperatures on the surface. One of our best local thermal
engines is the black paved surface of Runway 10/28 at IYK. The equipment
parking lot for the highway maintenance yard is another. The location of
these is pretty constant and reasonably predictable and reasonably benign.
Dust devils on the other hand, while they may begin at convective
sources, are cyclonic whirlwinds that travel laterally across the ground,
sometimes for miles. DDs in our area are typically less than five meters in
diameter. One monster dust devil that went across a portable weather station
at the Naval Air Warfare Center spun the anemometer over 80 knots before it
ripped the mast apart. We watched that one travel about ten miles. On
another occasion, a monster went across a mobile home park and took the roof
off a home and dissassembled tool sheds like card houses.

Casey Wilson wrote:
Dust devils on the other hand, while they may begin at convective
sources, are cyclonic whirlwinds that travel laterally across the ground,
sometimes for miles. DDs in our area are typically less than five meters in
diameter. One monster dust devil that went across a portable weather station
at the Naval Air Warfare Center spun the anemometer over 80 knots before it
ripped the mast apart. We watched that one travel about ten miles. On
another occasion, a monster went across a mobile home park and took the roof
off a home and dissassembled tool sheds like card houses.

Yeah, those are the kind of dust devils I look for 8^)

I remember one I saw in a valley north of Tonopah, when I was down low
looking for lift. It had one huge central column and six smaller ones
twisting around it. I could see huge pieces of sagebrush literally
getting blown out of its path. I pulled into it at roughly 1500 feet
AGL, and centered a 14 knot climb with dust and twigs flying all around
me. I was at 18000 feet in what seemed like a moment. Even at that
altitude, there was plenty of dust, and looking down into was like
looking into the maw of a huge snake that stretched all the way back
down to the ground.

You don't know what you're missing 8^)

Marc

I've seen this effect many times in Australia. Kept finding
lift over small irrigation ponds (altitude several hundred
feet). Decided to do an experiment whilst awaiting a buddy
who was interminable slow to get airborne. There was an
irrigation pond about 1km from the airfield. After losing
sufficient altitude doing aero, spoilered down to several
hundred feet over this pond, then climbed out and repeated
the procedure. Four or five times (like I said, he's slow).

The interesting features here (and in Arizona) a
- very dry air, and
- shallow irrigation tank/pond subject to good heating (warm water)
Don't know that I understand the physics, but extremely
consistent.

Beaver Pond Lift is however a different phenom...

Best Wishes for 2004 to all, Dave "YO"


Peter Creswick wrote in message ...
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.

On Mon, 29 Dec 2003 02:02:43 GMT, "Casey Wilson"
wrote in Message-Id: :


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.

Turning into the rising wing is intuitive, and logical. I'm only able
to think of a couple of alternative techniques, but I would expect
neither of them to provide superior results.

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.

That is consistent with what has been written in the past in this
newsgroup concerning the optimum bank in a turn-back to the airport
maneuver.

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.


My soaring experience was also in the Mojave Desert, Antelope Valley
area around El Mirage and toward the east and west of there. In the
summer, dust-devils were as plentiful as columns at the Forum. They
visibly marked areas above which the chance of encountering lift was
virtually assured.

I'd be interested in hearing more about your dust-devil encounter.

ny
Larry Dighera wrote in message . ..
On 23 Dec 2003 08:13:37 -0800, (Jim
Buckridge) wrote in Message-Id:
:

I got my glider private rating for less than $3000 including all costs...
books, exams, flights, etc.

During the early '70s, the Southern California Soaring Association ran
a glider operation at El Mirage Dry Lake (Antelope Valley) under the
guidance of Leonard Sharp. We had a 2-33, 1-26, and Blanik B-13 (?),
that we aero-towed to El Mirage Dry Lake, and an old Buick with a
1,500' cable for cheap auto-tow launches to well over a 1,000' all day
long. Dues in the club ran $10/month, and auto-tows were $2/each.
Instruction was provided (gratis) by many very experienced and
competent CFIG members.

The SCSA cub operation was inexpensive, and provided the camaraderie
and manpower that is characteristic of soaring.

As a horticulturalist and a glider pilot, perhaps the answer is that the
moist ground acts as more of a heat sink into the ground, up until it
achieves a full heat load and then dissipates this in the afternoon, more so
than the surrounding dry ground. Vegetation on a west facing slope is a
great source in the afternoons out our way.

I have found lift in moister areas, but much more so in the afternoons,
mainly when lower in the convection zone and certainly not in the mornings.
Try walking around a wet area at 10am and 6pm and compare the relative heat
to dry areas.

The other issue that could be occurring is the bubble of cool air over the
moist ground could be acting as a trigger point, for the drifting heated air
from the surrounding dry areas. We all know of the tremendously small things
that can act as a trigger.

As to lapse rates the air is not saturated till cloud base, unless of course
a fog is present (mornings) which is a different case than trying to get a
thermal.

Robert P
Nimbus 2C

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

"Andrew Sarangan" wrote in message
om...
(Kirk Stant) wrote in message
. com...
"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 adiabatic rate of moist air is about 1.5C/1000ft. For dry air it
is 3C/1000ft. Therefore, assuming that the water temperature is the
same as the surrounding ground (which would be true if the water is
shallow), I could see how one will experience greater lift above
water.

Not for unsaturated air it isn't. The moist rate only applies to saturated
air (ie in clouds)

Mike
MU-2

"goneill" wrote in message
...

"Aspley Nursery" wrote in message
...
Robert P
Nimbus 2C

I see in your sig Nimbus 2 C
That model is one I have been considering for some time.
Do you have any comments on it in comparison to other open class
gliders and in particular its approaches with the ventus style brakes.
Because there are none here I have some contrary comments from
other club members and even considered just getting a ASW20
instead .
The main reason I have been looking at it is most of the better pilots
are flying ventus's 18m but my budget only runs to an older open class
How does the 2c keep up with them all be it with a bit of water on to
get the wing loading up.The main "anti" comment is that it won't keep
up with its thicker aerofoil section and thus negating the main reason
why I am considering one.
gary

"Mike Rapoport" wrote in message thlink.net...
"Andrew Sarangan" wrote in message
om...
(Kirk Stant) wrote in message
. com...
"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 adiabatic rate of moist air is about 1.5C/1000ft. For dry air it
is 3C/1000ft. Therefore, assuming that the water temperature is the
same as the surrounding ground (which would be true if the water is
shallow), I could see how one will experience greater lift above
water.

Not for unsaturated air it isn't. The moist rate only applies to saturated
air (ie in clouds)

Mike
MU-2


OK, 1.5C/1000ft applies only to 100% RH air. But a 50% RH air must
still have a lower lapse rate than dry air, no?