Any sailplane pilots?

Andrew, read the numerical support of Mike Borgelt's statement below which I
posted a few days ago.


Mike Borgelt wrote:
Water vapour has a molecular weight of a bit over 18 and dry air a bit
more than 28. Water vapour at the same pressure as the air around it
is considerably less dense than dry air. More water vapour= more
bouyancy.

Just a simple approach with rough figures to support Mike's statement and
hopefully to trigger the "smart guys".
At atmospheric pressure (say 1013 hPa) and at 20 C° the density of dry air
is about 1.22 kg/m3. Pure water vapor at atmospheric pressure has a density
of 18/28 x 1.22 = 0.785 kg/m3, or 785 g/m3.
Air is saturated with water vapor when it contains 25 g/m3 at 20 C°.
Assume a relative humidity of say 30% on a dry day. Then one cubic meter of
air contains 0.3 x 25 = 7.5 g of water vapor and the air has then a density
of 1.2159 kg/m3. Assume further that over a shallow pond the humidity of the
air increases to 60% due to a serious evaporation from the pond. Then the
air directly over the pond will contain 0.6 x 25 = 15.0 g/m3 corresponding
to an air density of 1.2118 kg/m3.
So one cubic meter of air having 60% humidity is 1.2159 - 1.2118= 0.0041 kg
lighter then air with a humidity of 30%. This 4.1 g/m3 does not look much,
but compare this figure with the decrease in density when air is heated up.
The temperature coëfficiënt of air is 0.0044 kg/m3 per °C at 20 °C, meaning
that when air is heated up by one degree its density decreases with 4.4
g/m3.
So one may conclude that changing the relative humidity of air from 30% to
60% has the same effect on buoyancy as raising the temperature of air by 1
°C.
So it may be worthwhile indeed to search for a thermal over a shallow pond
in a dry area when low as I stated earlier.

Karel, NL


"Andrew Sarangan" schreef in bericht
om...
"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?

"Andrew Sarangan" wrote in message
om...
"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?

No. The reason that saturated air lapses at a slower rate is that latent
energy is being released as the water vapor changes to liquid, that is the
only reason.

Mike
MU-2

I don't disagree with your math but the air over the water is also cooler
than the air over the dry land adjacent to the pond.

Mike
MU-2

"K.P. Termaat" wrote in message
...
Andrew, read the numerical support of Mike Borgelt's statement below which
I
posted a few days ago.


Mike Borgelt wrote:
Water vapour has a molecular weight of a bit over 18 and dry air a bit
more than 28. Water vapour at the same pressure as the air around it
is considerably less dense than dry air. More water vapour= more
bouyancy.

Just a simple approach with rough figures to support Mike's statement and
hopefully to trigger the "smart guys".
At atmospheric pressure (say 1013 hPa) and at 20 C° the density of dry air
is about 1.22 kg/m3. Pure water vapor at atmospheric pressure has a
density
of 18/28 x 1.22 = 0.785 kg/m3, or 785 g/m3.
Air is saturated with water vapor when it contains 25 g/m3 at 20 C°.
Assume a relative humidity of say 30% on a dry day. Then one cubic meter
of
air contains 0.3 x 25 = 7.5 g of water vapor and the air has then a
density
of 1.2159 kg/m3. Assume further that over a shallow pond the humidity of
the
air increases to 60% due to a serious evaporation from the pond. Then the
air directly over the pond will contain 0.6 x 25 = 15.0 g/m3 corresponding
to an air density of 1.2118 kg/m3.
So one cubic meter of air having 60% humidity is 1.2159 - 1.2118= 0.0041
kg
lighter then air with a humidity of 30%. This 4.1 g/m3 does not look
much,
but compare this figure with the decrease in density when air is heated
up.
The temperature coëfficiënt of air is 0.0044 kg/m3 per °C at 20 °C,
meaning
that when air is heated up by one degree its density decreases with 4.4
g/m3.
So one may conclude that changing the relative humidity of air from 30% to
60% has the same effect on buoyancy as raising the temperature of air by
1
°C.
So it may be worthwhile indeed to search for a thermal over a shallow pond
in a dry area when low as I stated earlier.

Karel, NL


"Andrew Sarangan" schreef in bericht
om...
"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?

Mike

OT-- Can you give us a short disseration on the MU-2. I have seen a
lot of odd accidents with it and Japan quit making it years ago vs
correcting some of the problems as I recall????

Big John

On Tue, 06 Jan 2004 15:05:58 GMT, "Mike Rapoport"
wrote:


"Andrew Sarangan" wrote in message
. com...
"Mike Rapoport" wrote in message
rthlink.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?

No. The reason that saturated air lapses at a slower rate is that latent
energy is being released as the water vapor changes to liquid, that is the
only reason.

Mike
MU-2

There are indeed a number of odd accidents with no particular pattern. I
have read all the reports. Seven died after taking off over gross into
known severe icing with non-functioning boots (they knew this when they
departed). They didn't get very far. Another was lost after a NTS inflight
test failed. Why they tried it at night(!!!) is beyond me. Another flew
into the ground at Martha's Vineyard. He was 800' below the GS at the outer
marker. The fatal accident rate is about the same as the King Air 90 series
according to the last data I saw, so I guess that not all the bonehead
pilots are flying MU-2s.

Mitsubishi stopped making the airplanes in 1982 when the bottom fell out of
the aircraft market although they called planes built in 1982 and sold in
1985 "1985 models". The MU-2 enjoys excellent support from Mitusbishi even
though it has been out of production for 18 yrs.

The airframe was built in Japan and shipped to Texas where it was assembled
with US made engines, props, avionics and virtually everything else. The
plane had 70% US content. The airplanes are really well built, much better
than the competition. The MU-2 offers the best price/performance in its
class by a wide margin. It is substantially faster AND substantially
cheaper than comparable King Airs or Cheyennes.

Mike
MU-2


"Big John" wrote in message
...
Mike

OT-- Can you give us a short disseration on the MU-2. I have seen a
lot of odd accidents with it and Japan quit making it years ago vs
correcting some of the problems as I recall????

Big John

On Tue, 06 Jan 2004 15:05:58 GMT, "Mike Rapoport"
wrote:


"Andrew Sarangan" wrote in message
. com...
"Mike Rapoport" wrote in message
rthlink.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?

No. The reason that saturated air lapses at a slower rate is that latent
energy is being released as the water vapor changes to liquid, that is
the
only reason.

Mike
MU-2

"Mike Rapoport" wrote in message
k.net...
There are indeed a number of odd accidents with no particular pattern. I
have read all the reports. Seven died after taking off over gross into
known severe icing with non-functioning boots (they knew this when they
departed). They didn't get very far. Another was lost after a NTS
inflight
test failed. Why they tried it at night(!!!) is beyond me. Another flew
into the ground at Martha's Vineyard. He was 800' below the GS at the
outer
marker. The fatal accident rate is about the same as the King Air 90
series
according to the last data I saw, so I guess that not all the bonehead
pilots are flying MU-2s.

Mitsubishi stopped making the airplanes in 1982 when the bottom fell out
of
the aircraft market although they called planes built in 1982 and sold in
1985 "1985 models". The MU-2 enjoys excellent support from Mitusbishi
even
though it has been out of production for 18 yrs.

The airframe was built in Japan and shipped to Texas where it was
assembled
with US made engines, props, avionics and virtually everything else. The
plane had 70% US content. The airplanes are really well built, much
better
than the competition. The MU-2 offers the best price/performance in its
class by a wide margin. It is substantially faster AND substantially
cheaper than comparable King Airs or Cheyennes.

Mike
MU-2


Sorta!! http://www.jetbrokers.com/tpmu.html

"Tom Sixkiller" wrote in message
...

"Mike Rapoport" wrote in message
k.net...
There are indeed a number of odd accidents with no particular pattern.
I
have read all the reports. Seven died after taking off over gross into
known severe icing with non-functioning boots (they knew this when they
departed). They didn't get very far. Another was lost after a NTS
inflight
test failed. Why they tried it at night(!!!) is beyond me. Another
flew
into the ground at Martha's Vineyard. He was 800' below the GS at the
outer
marker. The fatal accident rate is about the same as the King Air 90
series
according to the last data I saw, so I guess that not all the bonehead
pilots are flying MU-2s.

Mitsubishi stopped making the airplanes in 1982 when the bottom fell out
of
the aircraft market although they called planes built in 1982 and sold
in
1985 "1985 models". The MU-2 enjoys excellent support from Mitusbishi
even
though it has been out of production for 18 yrs.

The airframe was built in Japan and shipped to Texas where it was
assembled
with US made engines, props, avionics and virtually everything else.
The
plane had 70% US content. The airplanes are really well built, much
better
than the competition. The MU-2 offers the best price/performance in its
class by a wide margin. It is substantially faster AND substantially
cheaper than comparable King Airs or Cheyennes.

Mike
MU-2


Sorta!! http://www.jetbrokers.com/tpmu.html


There are some problems with this data. The first thing that I noticed is
that a Merlin has lower operating cost than a Marquise. I happen to know
that a Merlin uses more fuel, has twice the maitenance cost per flight hour
and is slower. It can't possible have a lower DOC, so the data is
inaccurate..

Mike
MU-2

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

"Tom Sixkiller" wrote in message
...

Sorta!! http://www.jetbrokers.com/tpmu.html


There are some problems with this data. The first thing that I noticed is
that a Merlin has lower operating cost than a Marquise. I happen to know
that a Merlin uses more fuel, has twice the maitenance cost per flight
hour
and is slower. It can't possible have a lower DOC, so the data is
inaccurate..

Mike
MU-2

You dare to argue with experts?

"Tom Sixkiller" wrote in message
...
You dare to argue with experts?

You forgot the smiley in that post. You obviously can't be serious.

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



Sorta!! http://www.jetbrokers.com/tpmu.html


There are some problems with this data. The first thing that I noticed is
that a Merlin has lower operating cost than a Marquise. I happen to know
that a Merlin uses more fuel, has twice the maitenance cost per flight
hour
and is slower. It can't possible have a lower DOC, so the data is
inaccurate..

Maybe they're taking more into account than YOU are.