Sharing a thermal

[Hal]

Still learning to benefit from thermalling with another glider and so
far have not realized the benefits. If you are opposite another
glider and observing your progress in relationship to the other glider
how do you adjust your path if you see the other glider in better
lift? I seem to have the biggest problem at the top of the thermal
when the other glider has flattened out the bank angle and seems to
stay in better lift.

[Bill Daniels]

"Hal" > wrote in message
om...
> Still learning to benefit from thermalling with another glider and so
> far have not realized the benefits. If you are opposite another
> glider and observing your progress in relationship to the other glider
> how do you adjust your path if you see the other glider in better
> lift?

Use the other glider as a "zero time constant vario". When you are opposite
the other glider and his climb is at the greatest, reduce your bank to swing
wide on the opposite side of the thermal then tighten up again. Learn to
control airspeed by sound and use an audio vario so you can keep your eyes
on the other glider.

Reducing bank angle from 45 deg to 30 degree will double your turn diameter.
If you resume a 45 degree bank after 180 degrees of turn, you will have
moved the circle center one diameter toward the stronger lift. This gentle
correction will let you keep the other glider in sight.

He should follow your move to stay opposite.

I seem to have the biggest problem at the top of the thermal
> when the other glider has flattened out the bank angle and seems to
> stay in better lift.

I have the same problem. I think they are just better than I am. I avoid
the problem by leaving the thermal before reaching the top pretending I am
using the stronger lift band.

Bill Daniels

[Robert Ehrlich]

Bill Daniels wrote:
>
> "Hal" > wrote in message
> om...
> > Still learning to benefit from thermalling with another glider and so
> > far have not realized the benefits. If you are opposite another
> > glider and observing your progress in relationship to the other glider
> > how do you adjust your path if you see the other glider in better
> > lift?
>
> Use the other glider as a "zero time constant vario". When you are opposite
> the other glider and his climb is at the greatest, reduce your bank to swing
> wide on the opposite side of the thermal then tighten up again. Learn to
> control airspeed by sound and use an audio vario so you can keep your eyes
> on the other glider.
>
> Reducing bank angle from 45 deg to 30 degree will double your turn diameter.
> If you resume a 45 degree bank after 180 degrees of turn, you will have
> moved the circle center one diameter toward the stronger lift. This gentle
> correction will let you keep the other glider in sight.
>
> He should follow your move to stay opposite.

The way I was taught and I am now teaching my students for moving your circle
in a given dicrection is rather to revert to zero bank angle when your heading
is just the direction to which you want to move the circle, keeping wings
level the amount of time suited to the intended move and then resuming circling
at the previous bank angle.

Your method of reducing bank angle for half a turn assumes you start that a
quarter turn (90 degrees) before your heading is in the direction you want
to move. You are then in the worse part of your initial circle, maybe sinking.
If you needed 45 degree bank, that means that the thermal was narrow. Lowering
the bank angle at the worse part of the thermal will make most of the part of this
manoeuver in the worse part of the thermal or outside of it.

Anyway the main problem is to have the other glider follow your move. Regarding
this, this is also a pro for the method above, at least in my country, as
everybody having learnt here should have learnt in the same way and so the intent
should be obvious. However going straight ahead maybe misiniterpreted at the
begining of the manoeuver as leaving the thermal, although the dive associated
with this last thing is missing. If the other glider is known to have a radio on
the same frequency, using it may help.

[Andy Durbin]

(Hal) wrote in message >...
> Still learning to benefit from thermalling with another glider and so
> far have not realized the benefits. If you are opposite another
> glider and observing your progress in relationship to the other glider
> how do you adjust your path if you see the other glider in better
> lift? I seem to have the biggest problem at the top of the thermal
> when the other glider has flattened out the bank angle and seems to
> stay in better lift.

He may just have a lower sink rate than you. Differences is glider
sink rate are insignificant when both gliders are racked up tight in a
strong core, but they are very significant when trying to milk the
last 100ft out of a thermal.

If the gliders don't have different performance, and you are being
outclimbed, then go where his is and do what he is doing. It does
require all the pilots in the thermal to be aware of each other and to
continuously adapt. Keep everyone in your scan and position yourself
where you can be seen by everybody else.

Don't fixate so much on the one other glider that you miss the other 3
that are joining you, or the other one that is half a mile away
climbing far better than both of you.


Andy

[Chris OCallaghan]

Hel,

Great question. Let me give you the simple answer. If you are opposite
(180) a glider and it's climbing better, steepen your bank through 90
degrees of turn, then shallow out for several seconds to shift your
circle to the side of the thermal where you saw the better lift.

Let me take you around the points of the compass.

You see better lift on the south side of the circle. Your are on the
north side (facing West - turning left) Steepen up (60 degress)
through 90 degrees of turn, until you are facing south, then shallow
(not level - about 20 degrees) for a count of three. If you feel a
surge, stick with it for as long as you dare. In either case, you next
adjustment should be to steepen you turn to 60 degrees again. Stay
steep for one full turn, noting differences around the circle, then
adjust accordingly to center on the core at about 40 degrees of bank.
Be sure to watch out for your marker. If he didn't see your
adjustment, you will probably conflict with him as you come around
facing west.

Top of the thermal... lift gets much more difficult to center at the
top of a thermal. I can't offer much help here.

Cheers,

OC


(Hal) wrote in message >...
> Still learning to benefit from thermalling with another glider and so
> far have not realized the benefits. If you are opposite another
> glider and observing your progress in relationship to the other glider
> how do you adjust your path if you see the other glider in better
> lift? I seem to have the biggest problem at the top of the thermal
> when the other glider has flattened out the bank angle and seems to
> stay in better lift.

[Martin Hellman]

"Bill Daniels" > wrote in message news:
> Reducing bank angle from 45 deg to 30 degree will double your turn diameter.

Not a big deal and I did it wrong the first time, so won't vouch for
this one either, but think the diameter increases by 73%, not 100%.
The pertinent equations seem to be

Fh = m v^2/r

where Fh is the horizontal component of lift

and

Fh/mg = tan(theta)

where theta is the angle of bank, yielding

r = v^2 / [g * tan(theta)]

so

r(30) / r(45) = tan(45) / tan(30) = 1.73...

Any corrections are welcome.

Martin

[Martin Hellman]

"Bill Daniels" > wrote in message news:
> Reducing bank angle from 45 deg to 30 degree will double your turn diameter.

Not a big deal and I did it wrong the first time, so won't vouch for
this one either, but think the diameter increases by 73%, not 100%.
The pertinent equations seem to be

Fh = m v^2/r

where Fh is the horizontal component of lift

and

Fh/mg = tan(theta)

where theta is the angle of bank, yielding

r = v^2 / [g * tan(theta)]

so

r(30) / r(45) = tan(45) / tan(30) = 1.73...

Any corrections are welcome.

Martin

[Carl Czech]

How do you guys figure all this out? Count to 60 seconds, bank at 45,
then etc, etc, etc.

I watch the other glider. If he or she's doing better than me (almost
always), I try to proscribe the same path. If I'm the one doing
better,then I just keep on trying to do it. Mostly I follow my own
mediocre thermaling instincts while trying not to interfere with
others. Safety is always first, and I'll always avoid the too close
encounter or leave the thermal if things aren't working out.

Maybe it's just me, but when I overthink my flying, I never do as
well. Still learning, always...

Carl
Discus B, Warner Springs


(Chris OCallaghan) wrote in message >...
> Hel,
>
> Great question. Let me give you the simple answer. If you are opposite
> (180) a glider and it's climbing better, steepen your bank through 90
> degrees of turn, then shallow out for several seconds to shift your
> circle to the side of the thermal where you saw the better lift.
>
> Let me take you around the points of the compass.
>
> You see better lift on the south side of the circle. Your are on the
> north side (facing West - turning left) Steepen up (60 degress)
> through 90 degrees of turn, until you are facing south, then shallow
> (not level - about 20 degrees) for a count of three. If you feel a
> surge, stick with it for as long as you dare. In either case, you next
> adjustment should be to steepen you turn to 60 degrees again. Stay
> steep for one full turn, noting differences around the circle, then
> adjust accordingly to center on the core at about 40 degrees of bank.
> Be sure to watch out for your marker. If he didn't see your
> adjustment, you will probably conflict with him as you come around
> facing west.
>
> Top of the thermal... lift gets much more difficult to center at the
> top of a thermal. I can't offer much help here.
>
> Cheers,
>
> OC
>
>
> (Hal) wrote in message >...
> > Still learning to benefit from thermalling with another glider and so
> > far have not realized the benefits. If you are opposite another
> > glider and observing your progress in relationship to the other glider
> > how do you adjust your path if you see the other glider in better
> > lift? I seem to have the biggest problem at the top of the thermal
> > when the other glider has flattened out the bank angle and seems to
> > stay in better lift.

[Andrew Warbrick]

In practice the increase could be even less than 73%
because 'v' is not constant, you can thermal slower
with a lesser bank angle.

At 02:24 14 October 2004, Martin Hellman wrote:
>'Bill Daniels' wrote in message news:
>> Reducing bank angle from 45 deg to 30 degree will
>>double your turn diameter.
>
>Not a big deal and I did it wrong the first time,
>so won't vouch for
>this one either, but think the diameter increases by
>73%, not 100%.
>The pertinent equations seem to be
>
>Fh = m v^2/r
>
>where Fh is the horizontal component of lift
>
>and
>
>Fh/mg = tan(theta)
>
>where theta is the angle of bank, yielding
>
>r = v^2 / [g * tan(theta)]
>
>so
>
>r(30) / r(45) = tan(45) / tan(30) = 1.73...
>
>Any corrections are welcome.
>
>Martin
>

[Nyal Williams]

At 14:36 14 October 2004, Todd Pattist wrote:
(Chris OCallaghan) wrote:
>
>>If you are opposite
>>(180) a glider and it's climbing better, steepen your
>>bank through 90
>>degrees of turn, then shallow out for several seconds
>>to shift your
>>circle to the side of the thermal where you saw the
>>better lift.
>
>I wouldn't do this.
>
>When I'm sharing a thermal with another glider at the
>same
>altitude I'm trying to figure out two things - 1) 'where
>is
>the best lift?' and 2) 'what is the other glider going
>to
>do?' The first question is answered by watching the
>other
>glider's relative climb rate. The second is usually
>signaled by the changes he makes in bank angle.
>
>I have to recognize that the other pilot may not agree
>with
>me where the lift is strongest. I also keep in mind
>that
>he's trying to answer the same two questions I'm trying
>to
>answer, so my actions signal to him my intentions,
>just as
>his actions signal his to me. The first pilot to
>adjust
>his bank is signaling where he wants to move the center.
>
>I think it works better for each glider to flatten
>towards
>the core to move the center. I'm not against tightening
>in
>the core, a bit, but that method should be used with
>more
>caution as it tends to put the gliders closer. I'm
>against
>tightening in the sink first, then flattening as it's
>likely
>to confuse the other pilot and delay the cooperative
>process
>of moving to the center of the lift.
>
>If I see a pilot steepen in sink, I'm immediately concerned
>he thinks the lift is stronger there. However, if
>he waits
>90 and flattens on the heading towards the core, I'm
>reassured that he's either leaving and not a problem,
>or
>more likely, he agrees with my conclusion on where
>the core
>is.
>
>
>
>If a pilot is alone and thinks he's found the core,
>he'll
>typically steepen his bank. It keeps him turning in
>the
>core and it moves the center of the circle closer to
>the
>core before the pilot opens up a bit. If he doesn't
>steepen
>in the core, but recognizes the sink side first he'll
>typically open up the bank first and fly towards the
>core.
>Thus, with two pilots in the same circle negotiating
>as to
>where to move the core, it's the first to change his
>bank
>that signals where he thinks the core is.
>
>If I'm coming into the strong core, I desperately want
>to
>tighten, so I'm closely watching the glider on the
>weak
>side. If I see the pilot steepen there, I'm immediately
>concerned he thinks the lift is stronger there. However,
>if
>he waits 90 and flattens on the heading towards the
>core,
>I'm reassured that he's either leaving and not a problem,
>or
>more likely, he agrees with my conclusion on where
>the core
>is, and I'll expect him to tighten as he reaches the
>core.
>
>Bottom line,
>Todd Pattist - 'WH' Ventus C

Let's hope you two guys don't meet up in the same thermal!
I believe we have the makings here of a two-party
system on thermalling. Let's hope it doesn't get vicious.

Some of us don't even have a theory; we just blunder
around.

[Chris OCallaghan]

I'm a little confused by who is writing what and to whom, but each
person has their own peculiar theory of thermalling. Hal was
interested, as best as I could tell, in maximizing his climb. The
approach I suggested gets you into the better lift as quickly as
possible, and establishes a new "center" for others in the thermal to
join. If you have found the better lift, others will join you. If not,
you'll adjust back into the original center.

I find that only a handful of pilots actively seek the best part of
the thermal. Most are content to accept a circle that provides
relatively uniform lift all the way around. This means that I often
find myself conflicting with other gliders. But only briefly, as I'm
usually above them within a turn or two. I'll note that I do not fly
this way around the home drome... These are techniques for racing and
assume the people in a thermal understand that we are all trying to
get around the course as quickly as possible. Achieving a consistently
high climb rate has a dramatic impact on your x-c speed... so more
often than not, when I find the core (that is, the "real" core),
everyone else in the thermal quickly joins in.

If Hal is interested in maximizing his climb rate (which means getting
into the best available lift as quickly as possible), he needs to fly
aggressively. However, those who appreciate soaring for its tanquility
may not appreciate his enthusiasm, or particularly care that they're
not in the best lift. One adjusts as necessary to one's surroundings.

As for close quarters at 60 degrees... bring it on. I love flying with
pilots who can sustain a steep turn in the core. Great views, great
fun. And chances are good that all the pilots in there with you know
how to fly.

Years ago, at a contest in Corning, NY I entered a thermal at no more
than 400 feet above the ground. It was to my right, so I cleared and
started turn to the right. I found about 2 knots. After gaining a few
hundred feet I heard a call on the radio: "Five Niner, you're turning
the wrong way!" I nearly broke my neck trying to see who I was about
to hit. After two more turns, I looked up to see a Libelle 4,000 feet
above, nearly at cloudbase. (I should note that 59 had a very
distinctive paint job and 3-foot high winglets -- visible from miles
away). I keyed the mike... "Libelle, are you talking to me?"

"Yes, you're turning the wrong way."

It wasn't worth the effort to explain why I was turning right... or
why he shouldn't care. Within another turn he'd left the thermal. End
of discussion.

OC

[Chris OCallaghan]

> Let's hope you two guys don't meet up in the same thermal!
> I believe we have the makings here of a two-party
> system on thermalling. Let's hope it doesn't get vicious.
>
> Some of us don't even have a theory; we just blunder
> around.

Don't worry... I'll be above him in half a turn. And I'll have cold
beers waiting for both of you at the finish line. ;-)

[RWEpp]

I like the trash talk, Chris. Did you ever paly basketball?

[Bill Daniels]

"Todd Pattist" > wrote in message
...
> (Chris OCallaghan) wrote:
>
> >I'm a little confused by who is writing what and to whom, but each
> >person has their own peculiar theory of thermalling. Hal was
> >interested, as best as I could tell, in maximizing his climb. The
> >approach I suggested gets you into the better lift as quickly as
> >possible, and establishes a new "center" for others in the thermal to
> >join.
>
> I'm as interested as you in getting to the new center
> quickly, but here is the scenario: you and I are at the same
> altitude on opposite sides of a turn, and you are on the
> weak side, I'm on the strong side. I desperately want to
> turn tighter so I can stay in the lift and skip the weak
> lift you're in. I'm going to tighten as much as I can and
> still be clear of you .
>
> The problem is that you suggested tightening first on the
> weak side, then opening up. Aside from the fact that I don't
> see much advantage in tightening on a weak side, if you
> tighten, I can't tighten, as that puts us both head on if
> you don't open up. Since most pilots will tighten in strong
> cores, when I see you tighten, I've got to consider that
> you're mistaken as to the location of the core.
>
> We have the same problem if you're on the strong side, and
> I'm on the weak. If I use your method of tightening in the
> sink, you can't safely tighten in the strong lift because
> I've turned into the space you need.
>
> Bottom line, when we're at the same altitude, some
> cooperation will be both safer and better for both of us.
> We'll get the lift cored faster if we tighten in lift, not
> sink.
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

I went back and plotted the glider paths to scale using turn math. My
suggestion to reduce the bank by 15 degrees at the weakest point works
perfectly and creates no problem even if the pilot opposite tightens his
turn in the strongest lift. This isn't my idea, I think it was Klaus
Holighaus who originally wrote about it.

It's a bit counter-intuitive but an 8-second 180 degree turn at reduced bank
will place you in perfect position to tighten up in the core, or at least
you will have moved the turn center directly toward the strongest lift.
It's also much easier to keep track of other gliders at a lessened bank.
The small control deflections required are very efficient.

Violent maneuvering to center the core has several disadvantages. It's very
draggy to fly with large control deflections, it's harder to do the mental
dead reckoning to keep track of the direction to the stronger lift and it
risks collision with possibly unseen gliders.

To summarize, at the weakest point of the turn, lessen the bank by exactly
15 degrees (45 to 30 for example) and then hold that bank and airspeed for
180 degrees of turn and then increase the bank again to 45. This moves the
circle center roughly one turn diameter in the direction of the stronger
lift. It's a very gentle maneuver and it is easy to do. It just takes some
patience to stick with it through the 180 turn.

Bill Daniels

[Bill Daniels]

"Todd Pattist" > wrote in message
...
> "Bill Daniels" > wrote:
>
> >I went back and plotted the glider paths to scale using turn math. My
> >suggestion to reduce the bank by 15 degrees at the weakest point works
> >perfectly
>
> I don't have a problem with reducing the bank on the weak
> side. That's what I recommend too. I had a problem with
> *tightening* the bank on the weak side.
>
> Here is what I was responding to:
>
> "You see better lift on the south side of the circle. Your
> are on the north side (facing West - turning left) Steepen
> up (60 degress) (sic) through 90 degrees of turn, until you
> are facing south"
>
> >Violent maneuvering to center the core has several disadvantages. It's
very
> >draggy to fly with large control deflections, it's harder to do the
mental
> >dead reckoning to keep track of the direction to the stronger lift and it
> >risks collision with possibly unseen gliders.
>
> I completely agree. there's no reason to tighten in sink
> first, then open, then tighten again.
>
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

Todd, I believe that your method works but, if I understand what you are
saying, I have one reservation about it.

The time that it takes to level the wings from 45 degrees is about 2-3
seconds during which time you will have traveled about 200 to 300 feet in a
more-or-less straight line. (Estimating true airspeed at 100 FPS). It's
about the same time and distance to resume the 45 degree bank.

Resisting the temptation to roll through large angles is a good thing.
Changing from 45 to 30 or back can be done in less than a second while
traveling only about 100 feet. The glider is more efficient at 30 degree
bank so any losses during the 180 are small. During the 180 you can use the
time to re-acquire any gliders you may have lost track of.

Thermalling with those few pilots who use this method is like a beautiful
waltz toward the thermal core. It's very relaxing compared to flying with
pilots who make unpredictable moves to center the thermal. My waltz partner
and I almost always top the thermal first leaving the yank and bank "fighter
jocks" far below.

Thermalling with a pilot who can lock in on the opposite side of the turn is
one of soaring most beautiful experiences. He just seems to hang there in
space with no relative velocity as you both turn about the same center.
Even though he is very close, there is no danger since he is heading the
opposite direction all the time.

Bill Daniels

[Nyal Williams]

How much of this depends on the reaction time of the
vario?

I'm sure that textbooks from 40 years ago said to tighten
up in sink and open out in lift. As a matter of fact,
I believe this is one of the methods described by Reichmann.
This <can> make sense if the tightening if it is slight
>and takes place early on the sink side, followed quickly
by opening up again. Such a move would tend to move
the circle toward the core, but would be disastrous
if done late.

I agree that opening out will enlarge the circle such
that the opposite side will then move toward the center.


At 17:12 18 October 2004, Todd Pattist wrote:
>'Bill Daniels' wrote:
>
>>Todd, I believe that your method works but, if I understand
>>what you are
>>saying, I have one reservation about it.
>
>I'm not sure I spent much effort describing 'my' centering
>method. I was concerned about a technique being recommended
>to a beginner that called for excessive maneuvering
>in close
>quarters that was the opposite of what most pilots
>do.
>
>There are lots of commonly used techniques that the
>other
>pilot can use - and that 1) I'm comfortable with,
>2) I will
>recognize, and 3) I can adapt to and work with. He
>can roll
>level at 90 degrees from the weak point. He can simply
>reduce bank slightly to shift towards the center.
>If he's
>got longer wings, he may just slip it towards the center.
>For all these common techniques, if he goes first,
>it's easy
>to see what he's doing. and I can move in tighter
>behind
>him so we're both well centered in the core.
>
>The one thing that will screw us both up is if he tightens
>up in the sink.
>
>Personally, I use whatever works. As soon as I figure
>out
>which direction to go, and provided he hasn't made
>a move
>yet, I'll try to shift and signal to him where I think
>we
>should go. How much I shift and the technique I use
>can
>depend on lots of factors.
>
>Long wings and strong tight core with a small centering
>distance? - I may just slip it over.
>
>Near the top, lift weakening and I'm willing to leave,
>but I
>think there might be some better lift in the on-course
>direction? I'll probably roll it level, then roll
>back in
>if it improves, but keep going if not.
>
>Big center change to make? Probably roll it level.
>
>Normal centering adjustment? I'll reduce bank as needed
>as
>I pass the weak side and/or tighten in the best lift.
> Even
>this has lots of variations. Is the other pilot flying
>with
>too little bank? I may turn inside in the strong core.
> Is
>it a student in a 2-33 and I'm just climbing to start
>altitude? I'll be less aggressive. Is he ahead of
>me or
>behind me in the circle? I may combine the centering
>with a
>position adjustment to get opposite him.
>
>
>Todd Pattist - 'WH' Ventus C
>(Remove DONTSPAMME from address to email reply.)
>

[Bill Daniels]

"Nyal Williams" > wrote in message
...
> How much of this depends on the reaction time of the
> vario?
>

A lot.

Most vario's have a time constant of about 2-3 seconds or more. I put a
bunch of different varios on a test bench last winter and found some were as
bad as 11 seconds. The average 45 degree bank thermalling turn takes about
13 - 14 seconds so a 3 second delay can be a quarter turn. Some vario's
respond more quickly with the onset of lift but can take much longer to
return to zero after the lift ends.

FWIW, Mike Borgelts varios were the best of the lot on my test bench.

This means that you have to pay attention to the "whack it the back" (or
"whump in the rump" in the case of a 2-33) feel as you enter a thermal. If
you must watch the vario, figure a 60 degree of turn correction for vario
lag.

All this points up the need for an "inertial vario" that integrates the
vertical acceleration to display rate-of-climb. An inertial vario would
have no lag, no noise since it is damped by the mass of the glider and
should be dead accurate. UAV MEMS AHRS (Attitude Heading Reference Systems)
with three orthogonal gyros and accelerometers are in the $1000 range.
They'd make a fabulous vario. I'd love to have an instrument with a 1:1
correlation with the seat-of-the pants feel.

Bill Daniels

[Michel Talon]

Nyal Williams > wrote:
> How much of this depends on the reaction time of the
> vario?
>
> I'm sure that textbooks from 40 years ago said to tighten
> up in sink and open out in lift. As a matter of fact,
> I believe this is one of the methods described by Reichmann.
>

By the way, it is what i have been learnt to do, and it seems
to work :-)

>

--

Michel TALON

[Eric Greenwell]

Bill Daniels wrote:

>
> Most vario's have a time constant of about 2-3 seconds or more. I put a
> bunch of different varios on a test bench last winter and found some were as
> bad as 11 seconds. The average 45 degree bank thermalling turn takes about
> 13 - 14 seconds

Yikes! I don't know what you are flying, but it takes my ASH 26 about 27
seconds to make one turn (50 kts IAS, 8000' msl, 8.2 lb/sq ft wing
loading). That's measured from a flight trace. My ASW 20 was a little
quicker, flying at 7.5 lb/sq ft, but nothing like 14 seconds.

so a 3 second delay can be a quarter turn. Some vario's
> respond more quickly with the onset of lift but can take much longer to
> return to zero after the lift ends.
>
> FWIW, Mike Borgelts varios were the best of the lot on my test bench.

How did the 302 compare, what did you have the time constants set at,
and where you judging by the needle or the audio?

>
> This means that you have to pay attention to the "whack it the back" (or
> "whump in the rump" in the case of a 2-33) feel as you enter a thermal. If
> you must watch the vario, figure a 60 degree of turn correction for vario
> lag.

At least with my glider and my vario, it seems to be less than 20
degrees, and I can ignore it, since the glider doesn't respond quickly
enough. Flying small gliders (11 meter SparrowHawk, 12 meter Russia,
etc.) will surely change the equation.

>
> All this points up the need for an "inertial vario" that integrates the
> vertical acceleration to display rate-of-climb. An inertial vario would
> have no lag, no noise since it is damped by the mass of the glider and
> should be dead accurate. UAV MEMS AHRS (Attitude Heading Reference Systems)
> with three orthogonal gyros and accelerometers are in the $1000 range.
> They'd make a fabulous vario. I'd love to have an instrument with a 1:1
> correlation with the seat-of-the pants feel.

I'm guessing the hard part for an inertial vario would be ignoring stick
thermals.


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Eric Greenwell
Washington State
USA

[Bill Daniels]

"Eric Greenwell" > wrote in message
...

> Yikes! I don't know what you are flying, but it takes my ASH 26 about 27
> seconds to make one turn (50 kts IAS, 8000' msl, 8.2 lb/sq ft wing
> loading). That's measured from a flight trace. My ASW 20 was a little
> quicker, flying at 7.5 lb/sq ft, but nothing like 14 seconds.
>
You might re-check your bank angle and your static port position error. 27
seconds seems too long.

I fly a Nimbus 2C and I do turn tight. At 6lbs PSF I usually thermal at
45-55 degree bank at 40 MPH. I checked the elapsed time with the sweep
second hand on the panel clock. At 11 PSF the 45 degree bank Vmin sink goes
up to 55mph or so. (One of these days, I'll get an ASI in knots.)

Although, I did look at some flight recorder traces of the Nimbus thermaling
at 17,999 feet on a hot summer day with the ballast tanks full. The turns
were 2000 feet in diameter.

OTOH, a good 1-26 driver can rip off a 360 in 10 seconds.

> How did the 302 compare, what did you have the time constants set at,
> and where you judging by the needle or the audio?

I didn't check the 302.
>

> I'm guessing the hard part for an inertial vario would be ignoring stick
> thermals.
>
TE compensation can be done by the same computer that integrates the
acceleration.

Bill Daniels

[F.L. Whiteley]

"Eric Greenwell" > wrote in message
...
> Bill Daniels wrote:
>
> >
> > Most vario's have a time constant of about 2-3 seconds or more. I put a
> > bunch of different varios on a test bench last winter and found some
were as
> > bad as 11 seconds. The average 45 degree bank thermalling turn takes
about
> > 13 - 14 seconds
>
> Yikes! I don't know what you are flying, but it takes my ASH 26 about 27
> seconds to make one turn (50 kts IAS, 8000' msl, 8.2 lb/sq ft wing
> loading). That's measured from a flight trace. My ASW 20 was a little
> quicker, flying at 7.5 lb/sq ft, but nothing like 14 seconds.
>
Should be 17secs.

Try your flavor.
http://www.soarcsa.org/thinking_pages/soaring/turn_radius/turn_radius_calculator.htm

Frank Whiteley

[Jim Vincent]

>Try your flavor.
>
>http://www.soarcsa.org/thinking_pages/soaring/turn_radius/turn_radius_cal
culator.htm
>

Frank, the CSA website is truly impressive! Well done to you and your team.
Question though, where is the link to the Thinking Pages section? TIA.

Jim Vincent
N483SZ

[F.L. Whiteley]

"Jim Vincent" > wrote in message
...
> >Try your flavor.
> >
> >http://www.soarcsa.org/thinking_pages/soaring/turn_radius/turn_radius_cal
> culator.htm
> >
>
> Frank, the CSA website is truly impressive! Well done to you and your
team.
> Question though, where is the link to the Thinking Pages section? TIA.
>
> Jim Vincent
> N483SZ
>

No such link as it wasn't quite fleshed out. We'll add one though.

Frank

[Andy Blackburn]

At 8000' 50kts IAS = 58kts TAS, so 27 seconds would
correspond to a 40 degree bank angle. Wing loading
is only relegant to the degree that it affects stall
speed. The only relevant variables for turn radius
are ture airspeed and bank angle - assuming you are
flying in an unaccelerated condition.

Of course you can make a real fast circle if you spin
it...

9B


At 23:30 18 October 2004, F.L. Whiteley wrote:
>
>'Eric Greenwell' wrote in message
...
>> Bill Daniels wrote:
>>
>> >
>> > Most vario's have a time constant of about 2-3 seconds
>>>or more. I put a
>> > bunch of different varios on a test bench last winter
>>>and found some
>were as
>> > bad as 11 seconds. The average 45 degree bank thermalling
>>>turn takes
>about
>> > 13 - 14 seconds
>>
>> Yikes! I don't know what you are flying, but it takes
>>my ASH 26 about 27
>> seconds to make one turn (50 kts IAS, 8000' msl, 8.2
>>lb/sq ft wing
>> loading). That's measured from a flight trace. My
>>ASW 20 was a little
>> quicker, flying at 7.5 lb/sq ft, but nothing like
>>14 seconds.
>>
>Should be 17secs.
>
>Try your flavor.
>http://www.soarcsa.org/thinking_pages/soaring/turn_radius/turn_rad
>>ius_calculator.htm
>
>Frank Whiteley
>
>
>
>

[Eric Greenwell]

Bill Daniels wrote:

> "Eric Greenwell" > wrote in message
> ...
>
>
>>Yikes! I don't know what you are flying, but it takes my ASH 26 about 27
>>seconds to make one turn (50 kts IAS, 8000' msl, 8.2 lb/sq ft wing
>>loading). That's measured from a flight trace. My ASW 20 was a little
>>quicker, flying at 7.5 lb/sq ft, but nothing like 14 seconds.
>>
>
> You might re-check your bank angle and your static port position error. 27
> seconds seems too long.

Using Frank's calculator, 55 knots @ 35 degrees gives about the right
diameter and time. I don't know the density altitude that day, but the
speed sounds a little low. The IAS was likely 50 knots, where I usually
thermal when empty.

Looking at a contest flight, the thermal I measured then plugged into
the calculator gave 65 knots @ 40 degrees to get the right diameter and
time (27 seconds). That was a 9800' msl on a warm summer day, so the
speed seems about right; also, I was flying with water.

Next time I thermal, which might be 5 months from now, I'll have to
concentrate on bank angle more and redo the measurements. I generally
find myself flying at steeper bank angles than most pilots, except at
contests with good pilots, where it's about the same. Maybe the
instrument mounting holes on our panels aren't quite at 45 degrees...

But, what I was getting around to saying is your comment -

> The average 45 degree bank thermalling turn takes about
> 13 - 14 seconds

may be true for you, but not most pilots, based on my observations in
sport and contest flying, where 22+ seconds is typical. Maybe you meant
your average turn?


--
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Eric Greenwell
Washington State
USA

[Bill Daniels]

"Eric Greenwell" > wrote in message
...

> But, what I was getting around to saying is your comment -
>
> > The average 45 degree bank thermalling turn takes about
> > 13 - 14 seconds
>
> may be true for you, but not most pilots, based on my observations in
> sport and contest flying, where 22+ seconds is typical. Maybe you meant
> your average turn?
>

Nope, I meant my standard thermalling turn in the Nimbus is 14 seconds, 45
degrees and 45 MPH. If the core is small, I'll tighten up to a 60 degree
bank and 48mph. Ballast will, of course, bump those numbers up a little.

Eric, I think your turns are way too shallow and fast to make use of the
strong cores.

Bill Daniels

[Hal]

Wow, I really appreciate all the comments on thermalling. It is
amazing how much thought and calculations go into this sport although
not all agree on the solution. Reminds me of all the advice I got on
take-off. It was all good but also different.

It would seem logical if you are in a close circle with another glider
that reducing the bank angle is the safer technique. That said if you
are not in danger of conflict then increasing the bank angle seems to
follow what I was taught and what I have read.

The last flight of this year I tried water and that brought out a lot
of flaws in my termalling technique. Controlling speed and flying
through thermals were a problem. It was like learning all over again,
although when I looked at the trace after the flight I was impressed
with my average speed. I think using smoother and less abrupt changes
is something I need to work on and some of the techniques mentioned
here seem to enforce that.

[Udo Rumpf]

>> But, what I was getting around to saying is your comment -
>>
>> > The average 45 degree bank thermalling turn takes about
>> > 13 - 14 seconds
>>
>> may be true for you, but not most pilots, based on my observations in
>> sport and contest flying, where 22+ seconds is typical. Maybe you meant
>> your average turn?
>>
>
> Nope, I meant my standard thermalling turn in the Nimbus is 14 seconds, 45
> degrees and 45 MPH. If the core is small, I'll tighten up to a 60 degree
> bank and 48mph. Ballast will, of course, bump those numbers up a little.
>
> Eric, I think your turns are way too shallow and fast to make use of the
> strong cores.
>
> Bill Daniels

Eric &Bill
If a stall speed of a glider is 36 kt at a wing loading of 6 lb/sq/ft in a
45 deg.
it will be about 44 kt and at a 60 deg bank it will 50kt.
With a loading of 9lb/sq/ft the stall speed will be 44kt at a 45 deg bank it
will be 53kt and at a 60 deg bank it will be 61 kt.
I do not know what your respective wing loading are but both of you could be
right. It is more beneficial to turn tighter with a lighter wing loading ,
then it is
with a heavier wing loading.
Regards
Udo

[Eric Greenwell]

Udo Rumpf wrote:

>>
>> Eric, I think your turns are way too shallow and fast to make use of the
>> strong cores.
>>
>> Bill Daniels

You might be right, but I'm not routinely outclimbed by other pilots
wherever I fly, even by US World team members, so experience suggests
I'm not too far off the mark. I do try tighter banking occasionally, and
sometimes it helps, but it usually not, so the 40 degree bank is what I
normally end up using.

Perhaps you are circling more tightly than needed, your thermals are
much smaller than the ones I encounter, or as Udo suggests, it's the
wing loading difference. Or all items...

It would be interesting to look at the circling times of good contest
pilots using contest flight files, or perhaps the OLC files. Circle time
(our primary parameter in the discussion) and circle diameter can be
obtained directly from the flight trace, the true airspeed can be
determined by noting the highest and lowest ground speeds during the
circle and taking the average. These can be plugged into Frank's web
calculator to get the bank angle.


--
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Eric Greenwell
Washington State
USA

[Eric Greenwell]

Eric Greenwell wrote:

> Udo Rumpf wrote:
>
>>>
>>> Eric, I think your turns are way too shallow and fast to make use of the
>>> strong cores.
>>>
>>> Bill Daniels

Ooops! The above was written by Bill, not Udo, as I accidentally replied
to the wrong posting.

--
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Eric Greenwell
Washington State
USA

[Bill Daniels]

OK, this is going to get good.

Eric thinks wide fast turns work best for him. I think 45 degree turns are
best on average with steeper turns useful in small cores. If fly as slow as
I can without risking a stall.

Lets have a poll. Tell us how you thermal.

Bill Daniels

[Udo Rumpf]

Bill,
I try to fly, if the conditions warrant it, a 45 deg. bank
my wing loading is 8.3 lb/ft/sq at that bank my turn will be 22 seconds.
My speed will be 52 kt. indicated.
Udo
PS. I will check some of my contest recordings to make sure my memory is
still ok. Also I open up the turn when more lift is indicated and tighten
when
less lift. I use the Borgelt and I react to the trend, that is when the
needle or sound just start coming out of the bottom or falling off. Works
for me like a charm.
Udo

"Bill Daniels" > wrote in message
news:2bidd.499463$8_6.239366@attbi_s04...
> OK, this is going to get good.
>
> Eric thinks wide fast turns work best for him. I think 45 degree turns
> are
> best on average with steeper turns useful in small cores. If fly as slow
> as
> I can without risking a stall.
>
> Lets have a poll. Tell us how you thermal.
>
> Bill Daniels
>

[Udo Rumpf]

Bill,
a small correction, wing loading remains 8.3 lb/ft/sq, average time around
the circle 25 second at 50 kt Ground speed. Bank of between 40 and 45 deg. I
use the Instrument screws as reference.
I have a number of recordings. If any body cares to look at them let me know
and I will send an http.
Udo
> Bill,
> I try to fly, if the conditions warrant it, a 45 deg. bank
> my wing loading is 8.3 lb/ft/sq at that bank my turn will be 22 seconds.
> My speed will be 52 kt. indicated.
> Udo
> PS. I will check some of my contest recordings to make sure my memory is
> still ok. Also I open up the turn when more lift is indicated and tighten
> when
> less lift. I use the Borgelt and I react to the trend, that is when the
> needle or sound just start coming out of the bottom or falling off. Works
> for me like a charm.
> Udo
>
> "Bill Daniels" > wrote in message
> news:2bidd.499463$8_6.239366@attbi_s04...
>> OK, this is going to get good.
>>
>> Eric thinks wide fast turns work best for him. I think 45 degree turns
>> are
>> best on average with steeper turns useful in small cores. If fly as slow
>> as
>> I can without risking a stall.
>>
>> Lets have a poll. Tell us how you thermal.
>>
>> Bill Daniels
>>
>

[Eric Greenwell]

Bill Daniels wrote:
> OK, this is going to get good.
>
> Eric thinks wide fast turns work best for him.

"Fast" is relative: at 8.2 lb/sq ft, going a slower is
counterproductive. I can slow down to 45 knots from the usual 50, but
the glider isn't very steady, feels "draggy", and it doesn't climb any
better, even in very smooth thermals (this measurement done when
circling with other gliders). In anything but very smooth thermals, the
50-52 knots is needed to have decent control, anyway.

> I think 45 degree turns are
> best on average with steeper turns useful in small cores. If fly as slow as
> I can without risking a stall.

This may be appropriate for the Nimbus 2, but not for the ASH 26, where
the stall is noticeably lower than minimum sink. Waibel told me once
that he considers this a safety feature.

>
> Lets have a poll. Tell us how you thermal.

And what, and where. These are likely important reasons for your bank
angle and speed preferences.

>
> Bill Daniels
>


--
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Eric Greenwell
Washington State
USA

[Bill Daniels]

"Eric Greenwell" > wrote in message
...
> Bill Daniels wrote:
> > OK, this is going to get good.
> >
> > Eric thinks wide fast turns work best for him.
>
> "Fast" is relative: at 8.2 lb/sq ft, going a slower is
> counterproductive. I can slow down to 45 knots from the usual 50, but
> the glider isn't very steady, feels "draggy", and it doesn't climb any
> better, even in very smooth thermals (this measurement done when
> circling with other gliders). In anything but very smooth thermals, the
> 50-52 knots is needed to have decent control, anyway.
>
> > I think 45 degree turns are
> > best on average with steeper turns useful in small cores. If fly as
slow as
> > I can without risking a stall.
>
> This may be appropriate for the Nimbus 2, but not for the ASH 26, where
> the stall is noticeably lower than minimum sink. Waibel told me once
> that he considers this a safety feature.
>
> >
> > Lets have a poll. Tell us how you thermal.
>
> And what, and where. These are likely important reasons for your bank
> angle and speed preferences.
>

I just examined some IGC traces of mine and, correcting for density
altitude, the IAS was about 43 mph in what looks like a 40 - 45 degree bank.
I'm still looking for a representative climb in a small, strong core but I
think I should have one from Moriarty, NM.

The Nimbus 2C ailerons become very ineffective at low IAS but it still
responds nicely to rudder inputs. I use Dick Johnson's slipping turn so the
ailerons stay neutral and I fly the bank with rudder. The big glider is
very stable in slow turns.

If there's a strong core, I'm not concerned with sink rate in slow, steep
turns. The strength of thermal cores will easily offset that.

Bill Daniels

[Andy Blackburn]

Actual SeeYou measurements

ASW-27B dry (8.2 lbs/sf)
Altitude 13,000 ft
TAS/IAS: 71/53 mph
Measured radius: ~350 ft
Implied bank angle: 43.5 degrees
Stall speed (calculated): ~51 mph

ASW-27B wet (11.5 lbs/sf) -- prior day
Altitude 13,500 ft
TAS/IAS: 84/61 mph
Measured radius: ~515 ft
Implied bank angle: 42.5 degrees
Stall speed (calculated): ~57 mph

9B


At 03:06 20 October 2004, Eric Greenwell wrote:
>Bill Daniels wrote:
>> OK, this is going to get good.
>>
>> Eric thinks wide fast turns work best for him.
>
>'Fast' is relative: at 8.2 lb/sq ft, going a slower
>is
>counterproductive. I can slow down to 45 knots from
>the usual 50, but
>the glider isn't very steady, feels 'draggy', and it
>doesn't climb any
>better, even in very smooth thermals (this measurement
>done when
>circling with other gliders). In anything but very
>smooth thermals, the
>50-52 knots is needed to have decent control, anyway.
>
>> I think 45 degree turns are
>> best on average with steeper turns useful in small
>>cores. If fly as slow as
>> I can without risking a stall.
>
>This may be appropriate for the Nimbus 2, but not for
>the ASH 26, where
>the stall is noticeably lower than minimum sink. Waibel
>told me once
>that he considers this a safety feature.
>
>>
>> Lets have a poll. Tell us how you thermal.
>
>And what, and where. These are likely important reasons
>for your bank
>angle and speed preferences.
>
>>
>> Bill Daniels
>>
>
>
>--
>Change 'netto' to 'net' to email me directly
>
>Eric Greenwell
>Washington State
>USA
>

[Bob Korves]

"Bill Daniels" > wrote in message
news:2bidd.499463$8_6.239366@attbi_s04...
> Lets have a poll. Tell us how you thermal.
>
> Bill Daniels
>

I do whatever it takes to make the averager number bigger! What that might
be depends on whether I am at Truckee or Ely or Williams; whether the lift
is turbulent or smooth, big or small core, alone or with other gliders, with
or without water, bugs on the wings, etc. The correct bank angle and speed
might change from one side of the circle to the other and is changing,
experimenting, trying to iterate the best possible lift.

When I see another glider climbing better in another part of the thermal, I
just go there!

It really matters that the climb rate is as high as possible in each climb
taken. When I fly with others in our DuoDiscus I am amazed at how carefully
many pilots follow the speed director (which is on a 30 second averager) in
cruise, but climb sloppily and lazily, accepting whatever comes and not
actively searching for the best thermals and using them to the max.
Maximizing climb and avoiding sink are the best ways to cover miles (or
km.). Interthermal glide speeds are relatively unimportant.

Of course, most of this is just experience -- many hours of flying and
thermalling -- and better learned in thermals than on Usenet...
-Bob Korves
5H DuoDiscus
5K LAK-17a

[Greg Arnold]

Won't SeeYou underestimate the thermalling speed because it is
calculating speed based on the straightline distance between different
points on a circle?


Andy Blackburn wrote:
> Actual SeeYou measurements
>
> ASW-27B dry (8.2 lbs/sf)
> Altitude 13,000 ft
> TAS/IAS: 71/53 mph
> Measured radius: ~350 ft
> Implied bank angle: 43.5 degrees
> Stall speed (calculated): ~51 mph
>
> ASW-27B wet (11.5 lbs/sf) -- prior day
> Altitude 13,500 ft
> TAS/IAS: 84/61 mph
> Measured radius: ~515 ft
> Implied bank angle: 42.5 degrees
> Stall speed (calculated): ~57 mph
>
> 9B
>
>

[Jim Vincent]

>> > Lets have a poll. Tell us how you thermal.

I don't believe in a shallow bank for 180 degrees. The trade off in efficiency
is more than offset by getting out of the sink and into the lift quicker.

Reichman's rules: Increase bank in sink, shallow bank as vario rises, increase
bank in lift. My numbers say min sink is 44 ktws, 30 degree min sink is 49, 45
is 52, and 60 is 63 kts.

If themals are tight and narly, then crank 45-60, decreasing with altitude as
thermals generally widen. Like many here, the screws on the instruments are
the 45 degree indicator (a golden nugget from a CSA instructor). I would
rather increase my airspeed than shallow the bank since the increase in
airspeed effectively increases the turn radius with minimal drag effects and
low time lag.

To me, crankin and bankin to get into the best lift is worth it...plus much
more fun!

Jim Vincent
N483SZ

[Gary Boggs]

I used to think that I could climb faster with steeper turns in the
strongest part of the thermal, but after flying with the some of the best
open class pilots in the USA, and seeing them outclimb me, it seems to me
that lower bank angles, 30-45 degrees, and slower speeds are better than
tightening up in the core and using steeper banks angles, and higher IAS.
Maybe this isn't as true with 15m wings.

I have seen days though, when you couldn't even climb if you didn't wrap it
up hard and use bank angles of at least 60 degrees or more.

It may not always be the most efficient, but I do think it's fun to circle
at very high bank angles for a few turns, or more once and a while. It is
such a rush to just stand a sailplane on it's wing., and climb at 3 or 4+
g's!

Gary Boggs

"Jim Vincent" > wrote in message
...
> >> > Lets have a poll. Tell us how you thermal.
>
> I don't believe in a shallow bank for 180 degrees. The trade off in
efficiency
> is more than offset by getting out of the sink and into the lift quicker.
>
> Reichman's rules: Increase bank in sink, shallow bank as vario rises,
increase
> bank in lift. My numbers say min sink is 44 ktws, 30 degree min sink is
49, 45
> is 52, and 60 is 63 kts.
>
> If themals are tight and narly, then crank 45-60, decreasing with altitude
as
> thermals generally widen. Like many here, the screws on the instruments
are
> the 45 degree indicator (a golden nugget from a CSA instructor). I would
> rather increase my airspeed than shallow the bank since the increase in
> airspeed effectively increases the turn radius with minimal drag effects
and
> low time lag.
>
> To me, crankin and bankin to get into the best lift is worth it...plus
much
> more fun!
>
> Jim Vincent
> N483SZ
>

[Andy Blackburn]

I'm at a pretty high sampling rate - 2 seconds I think.
At least my circles look pretty round. I don't know
how SeeYou calculates ground speed, but it stands to
reason that if you only had, say, 2 samples per circle
that might lead to an error - unless SeeYou somehow
assumes a circle through the points (seems doubtful).

The answer is pretty consistent with the bank angles
I thought I was flying based on aligning the diagonal
screws securing my instruments.

9B

At 05:24 20 October 2004, Greg Arnold wrote:
>Won't SeeYou underestimate the thermalling speed because
>it is
>calculating speed based on the straightline distance
>between different
>points on a circle?
>
>
>Andy Blackburn wrote:
>> Actual SeeYou measurements
>>
>> ASW-27B dry (8.2 lbs/sf)
>> Altitude 13,000 ft
>> TAS/IAS: 71/53 mph
>> Measured radius: ~350 ft
>> Implied bank angle: 43.5 degrees
>> Stall speed (calculated): ~51 mph
>>
>> ASW-27B wet (11.5 lbs/sf) -- prior day
>> Altitude 13,500 ft
>> TAS/IAS: 84/61 mph
>> Measured radius: ~515 ft
>> Implied bank angle: 42.5 degrees
>> Stall speed (calculated): ~57 mph
>>
>> 9B
>>
>>
>

[Chip Bearden]

Greg Arnold > wrote in message news:<0imdd.50323$hj.44614@fed1read07>...
> Won't SeeYou underestimate the thermalling speed because it is
> calculating speed based on the straightline distance between different
> points on a circle?

I was unable to duplicate SeeYou's calculations of thermaling speed. I
tried straight line between two points, fitting a circle through three
points, and calculating circumference based on a rough diameter.

I was trying to reconcile indicated airspeed I recalled from the
flight with SeeYou's numbers. But even after correcting for true
airspeed, I was still off. I finally gave up. Does anyone know how
SeeYou calculates speed in a thermal?

Chip Bearden
ASW 24 "JB"

[Wojciech Scigala]

Dnia 10/20/04 5:16 PM, U¿ytkownik Chip Bearden napisa³:

> I was trying to reconcile indicated airspeed I recalled from the
> flight with SeeYou's numbers. But even after correcting for true
> airspeed, I was still off. I finally gave up. Does anyone know how
> SeeYou calculates speed in a thermal?
Ground speed (as well as vertival speed) is an average calculated with a
few last readings. Check Options->Flight menu and values named "ground
speed filter" and "vertical speed filter".

--
Wojtus'.net __|__
FidoNet: 2:484/47 `--------o--------'

[Mark James Boyd]

I fly into it and continue until the trend of the vario reverses to
down, then begin a turn into the lifted wing with between
30-45 degrees of bank. I've tried up to 60 degrees, and have
seen only worse climb from over 45 degrees. This in commonly
4-6 knot thermals.

Less than 30 degrees and I'm not sure I could stay in any of the thermals,
more than 45 and I think the loss of upward lift due to bank angle
exceeds any benefit from a tighter core, at least
in thermals around here.

I also tend to stay in the middle third of the thermal altitude,
so if it tops out at 9000ft agl, I'l stay between 3000-6000 ft agl,
although sometimes a little higher over unlandable or known thermal-free
terrain.

In article >,
Jim Vincent > wrote:
>>> > Lets have a poll. Tell us how you thermal.
>
>I don't believe in a shallow bank for 180 degrees. The trade off in efficiency
>is more than offset by getting out of the sink and into the lift quicker.
>
>Reichman's rules: Increase bank in sink, shallow bank as vario rises, increase
>bank in lift. My numbers say min sink is 44 ktws, 30 degree min sink is 49, 45
>is 52, and 60 is 63 kts.
>
>If themals are tight and narly, then crank 45-60, decreasing with altitude as
>thermals generally widen. Like many here, the screws on the instruments are
>the 45 degree indicator (a golden nugget from a CSA instructor). I would
>rather increase my airspeed than shallow the bank since the increase in
>airspeed effectively increases the turn radius with minimal drag effects and
>low time lag.
>
>To me, crankin and bankin to get into the best lift is worth it...plus much
>more fun!
>
>Jim Vincent
>N483SZ



--

------------+
Mark J. Boyd

[Chris OCallaghan]

Soccer.

Gentlemen play rugby.

(RWEpp) wrote in message >...
> I like the trash talk, Chris. Did you ever paly basketball?

[Chris OCallaghan]

It's a workable technique, but the logic isn't wholly clear why it's
better than simply steering directly into the core.

Draw a set of concentric circles representing decreasing lift as you
move away from the core. Place your circle slightly off center. While
a widening of the turn puts you in a good position to move gracefully
into the core on the opposite side, it also steers you initially into
weaker lift and keeps you in it for several extra seconds (as your
rate of turn decreases with decreasing bank). Weaker lift, longer
exposure.

Also, as you shallow your bank, the glider opposite will begin to
catch up with you, turning inside, assuming he is not matching your
correction. And in fact, the shallower your turn, the more difficult
it will be to see since your wing blocks more of your view to the
rear, exactly where the other glider will approach you as you widen.

No danger. Simply requires an extra look before steepening into the
core.

If the gradient is strong, it's worth your while to move in quickly,
even if it briefly costs in terms of gliding efficiency. I may be
flying less effeciently, but I'm doing so in stronger lift, and I'll
return to optimum bank sooner, and centered on the core. The stronger
the gradient, the greater the payoff for letting one's impatience
rule.

As for safety, if I'm turning inside the other glider, I'm keeping it
in view. Shallowing your turn puts the other glider in your blind spot
and potentially in a position to keep your from moving gracefully into
the core. If I am breaking the established pattern, I'd much rather
keep others in view than to assume that they've seen me and depend on
them to adjust.

Steeper... gets you to better lift more quickly without traversing
weaker lift first. Shallower... well, I have to admit, it's more
graceful, though not necessarily safer, nor better for maximizing your
climb rate.