Hands off thermalling

[John Jones]

How many gliders can be trimmed for hands off thermalling?

An instructor showed me, with spoilers open and proper
trim, the glider will stabilize in a slow descending
turn. Claimed it was good for getting out of a cloud.

Neat, but would not want to thermal with the spoilers
open.

[JC]

John Jones > wrote:

>How many gliders can be trimmed for hands off thermalling?
>
>An instructor showed me, with spoilers open and proper
>trim, the glider will stabilize in a slow descending
>turn. Claimed it was good for getting out of a cloud.
>
>Neat, but would not want to thermal with the spoilers
>open.
>
>
I have done it in the Schleicher K-6e that I used to own.
I was near the top of a pretty good thermal, fairly big. I was banked
about 15 degrees. I set the elevator trim, took my hands off the
stick and refolded my chart. I was pleasantly surprised when I
continued to climb.

There are other planes I would not ever take my hand off the stick for
a second.

>
>

[Nick Hill]

John Jones wrote:

> How many gliders can be trimmed for hands off thermalling?
>
> An instructor showed me, with spoilers open and proper
> trim, the glider will stabilize in a slow descending
> turn. Claimed it was good for getting out of a cloud.
>
> Neat, but would not want to thermal with the spoilers
> open.
>

People I know who have flown a Skylark 4 state that it will happily
climb in a thermal hands off while you fold you map, eat sandwiches etc

Nick Hill

[Shawn Curry]

John Jones wrote:
> How many gliders can be trimmed for hands off thermalling?
>
> An instructor showed me, with spoilers open and proper
> trim, the glider will stabilize in a slow descending
> turn. Claimed it was good for getting out of a cloud.
>
> Neat, but would not want to thermal with the spoilers
> open.

Grob Astir CS works pretty well. Passed the urination-while-thermalling
test. So does my Mosquito.
Don't try it in a Ventus =o
As for getting out of a cloud that's a benign spiral. Lots to be found
by Googling this group, but ask your instructor for a demo too.

Shawn

[Shawn Curry]

Shawn Curry wrote:
> John Jones wrote:
>
>> How many gliders can be trimmed for hands off thermalling?
>>
>> An instructor showed me, with spoilers open and proper
>> trim, the glider will stabilize in a slow descending
>> turn. Claimed it was good for getting out of a cloud.
>>
>> Neat, but would not want to thermal with the spoilers
>> open.
>
>
> Grob Astir CS works pretty well. Passed the urination-while-thermalling
> test. So does my Mosquito.
> Don't try it in a Ventus =o
> As for getting out of a cloud that's a benign spiral. Lots to be found
> by Googling this group, but ask your instructor for a demo too.

Oops TIA. S/he did demo it.

Shawn

[Andy Durbin]

John Jones > wrote in message >...
> How many gliders can be trimmed for hands off thermalling?
>
> An instructor showed me, with spoilers open and proper
> trim, the glider will stabilize in a slow descending
> turn. Claimed it was good for getting out of a cloud.
>
> Neat, but would not want to thermal with the spoilers
> open.

My ASW 19b and ASW 28 will thermal hands off for several turns. Only
works for smooth thermals not the more typical rowdy tight cores of a
strong Arizona day.

The full airbrake, hands and feet off controls, descent is known as
the benign spiral. Does not work in all gliders so try it before you
use it in a real descent emergency.


Andy

[Doug Taylor]

During Gary Osoba's first flight in the SparrowHawk, he flew for 10
minutes hands off, including entering and centering two thermals.

Also in the SparrowHawk, I find it easiest to use the pee-bag while in
a thermal, as long as it is a nice big smooth one.


John Jones > wrote in message >...
> How many gliders can be trimmed for hands off thermalling?
>
> An instructor showed me, with spoilers open and proper
> trim, the glider will stabilize in a slow descending
> turn. Claimed it was good for getting out of a cloud.
>
> Neat, but would not want to thermal with the spoilers
> open.

[Claudia Buengen]

The DG-100 - just park it in a thermal and go up!

Seriously, I tried it once in fairly calm conditions, trimmed it, let go
of the stick, and I managed to gain about a hundred feet before it
started oscillating.

Claudia

Nick Hill wrote:
> John Jones wrote:
>
>> How many gliders can be trimmed for hands off thermalling?
>>
>> An instructor showed me, with spoilers open and proper
>> trim, the glider will stabilize in a slow descending
>> turn. Claimed it was good for getting out of a cloud.
>>
>> Neat, but would not want to thermal with the spoilers
>> open.
>
>
> People I know who have flown a Skylark 4 state that it will happily
> climb in a thermal hands off while you fold you map, eat sandwiches etc
>
> Nick Hill

[Jim Vincent]

>How many gliders can be trimmed for hands off thermalling?
>
>An instructor showed me, with spoilers open and proper
>trim, the glider will stabilize in a slow descending
>turn. Claimed it was good for getting out of a cloud.

You're talking about two totally different things here. One is thermalling,
the other is the benign spiral mode (what your instuctor did with you....good
instructor!).

The way I teach the benign spiral is trim for 60 kts and don't touch the stick.
The plane will speed up and slow down and turn, but should always stay within
limits. As you said, it is useful if caught in cloud. Spoilers deployed is a
new one to me.

Jim Vincent
CFIG
N483SZ

[Bruce Greeff]

John Jones wrote:

> How many gliders can be trimmed for hands off thermalling?
>
> An instructor showed me, with spoilers open and proper
> trim, the glider will stabilize in a slow descending
> turn. Claimed it was good for getting out of a cloud.
>
> Neat, but would not want to thermal with the spoilers
> open.
>
>
>
>
>
Depends what you are flying, don't try this with a std. Cirrus. The speed
excursions are quite extreme.

[Martin Gregorie]

On 22 Apr 2004 11:16:50 -0700, (Andy Durbin)
wrote:

>John Jones > wrote in message >...
>> How many gliders can be trimmed for hands off thermalling?
>>
>> An instructor showed me, with spoilers open and proper
>> trim, the glider will stabilize in a slow descending
>> turn. Claimed it was good for getting out of a cloud.
>>
>> Neat, but would not want to thermal with the spoilers
>> open.
>
>My ASW 19b and ASW 28 will thermal hands off for several turns. Only
>works for smooth thermals not the more typical rowdy tight cores of a
>strong Arizona day.
>
>The full airbrake, hands and feet off controls, descent is known as
>the benign spiral. Does not work in all gliders so try it before you
>use it in a real descent emergency.
>
Indeed. I found out that the ASW-20 has a 20 second phugoid when
trimmed at 50 kts, clean at zero flap. I didn't notice the height
variation, but the speed excursion is +/- 5 kts and its stable - once
the phugoid is established in smooth air it doesn't increase or damp
out over about 10 cycles. I haven't tried other trim speeds and was
using my feet gently to stay straight, so I don't know if a spiral
would have developed or what happens at other trim settings

I must try the benign spiral next time I'm out with height to spare.
What sort of speed is recommended?

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Eric Greenwell]

Jim Vincent wrote:

> You're talking about two totally different things here. One is thermalling,
> the other is the benign spiral mode (what your instuctor did with you....good
> instructor!).
>
> The way I teach the benign spiral is trim for 60 kts and don't touch the stick.
> The plane will speed up and slow down and turn, but should always stay within
> limits. As you said, it is useful if caught in cloud. Spoilers deployed is a
> new one to me.

My experience, and that of many others, is the having spoilers deployed
is crucial to the benign spiral mode. Some gliders can't manage it, even
with the spoilers open. What glider are you teaching this in?

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

Eric Greenwell
Washington State
USA

[Jim Vincent]

>My experience, and that of many others, is the having spoilers deployed
>is crucial to the benign spiral mode

You're correct, Eric. The maneuver should be taught in both configs to
determine the characteristics.

Jim Vincent
CFIG
N483SZ

[F.L. Whiteley]

"John Jones" > wrote in message
...
> How many gliders can be trimmed for hands off thermalling?
>
> An instructor showed me, with spoilers open and proper
> trim, the glider will stabilize in a slow descending
> turn. Claimed it was good for getting out of a cloud.
>
> Neat, but would not want to thermal with the spoilers
> open.
>
>
Open Cirrus, no problemo

[mike fadden]

(Doug Taylor) wrote in message >...
> During Gary Osoba's first flight in the SparrowHawk, he flew for 10
> minutes hands off, including entering and centering two thermals.
>
> Also in the SparrowHawk, I find it easiest to use the pee-bag while in
> a thermal, as long as it is a nice big smooth one.
>
Yeah. Those small, textured bags can be a real distraction ;-).

Mike

[Andy Durbin]

(Jim Vincent) wrote in message >...
> >My experience, and that of many others, is the having spoilers deployed
> >is crucial to the benign spiral mode
>
> You're correct, Eric. The maneuver should be taught in both configs to
> determine the characteristics.
>
> Jim Vincent
> CFIG
> N483SZ
>

The whole point of the benign spiral is to make an emergency descent
in non visual conditions. Emphasis on descent. Full airbrakes, gear
down, hands AND feet off controls. I can see absolutely no point in
doing this with airbrakes closed.


Andy

[Buck Wild]

John Jones > wrote in message >...
> How many gliders can be trimmed for hands off thermalling?
>


LS4
-Dan

[Bill Daniels]

The aerodynamics of this are interesting.

The most likely reason that a glider exhibits the spiral stability to fly
thermals hands-off is that once it is set up to fly coordinated circles and
the controls released, the controls have just enough friction to keep the
aileron and rudder controls where they were - just a bit of outside aileron
and rudder. If you lube the controls, you may lose the hands-off
thermalling capability.

The other possibility is that the inner and outer wings are flying on
opposite sides of the polar curve with the outer wing on the high speed
side of the polar and the inner wing on the slower side. Discontinuities in
the polar due to separation bubbles may play a part too.

A perfectly symmetrical glider with a perfectly smooth polar and
frictionless controls SHOULD develop a spiral dive from a hands off turn.

Bill Daniels


"Buck Wild" > wrote in message
om...
> John Jones > wrote in message
>...
> > How many gliders can be trimmed for hands off thermalling?
> >
>
>
> LS4
> -Dan

[Mark James Boyd]

mike fadden > wrote:
(Doug Taylor) wrote in message >...
>> Also in the SparrowHawk, I find it easiest to use the pee-bag while in
>> a thermal, as long as it is a nice big smooth one.
>>
>Yeah. Those small, textured bags can be a real distraction ;-).
ROFLMAO. I KNEW someone was gonna catch that one...
--

------------+
Mark Boyd
Avenal, California, USA

[Andreas Maurer]

On Fri, 23 Apr 2004 20:14:02 GMT, "Bill Daniels" >
wrote:


>A perfectly symmetrical glider with a perfectly smooth polar and
>frictionless controls SHOULD develop a spiral dive from a hands off turn.

How does this explain the behaviour of non-radio-controlled model
gloiders that return to level flight anytime? They are built perfectly
symmetrical, have a smooth polar and no controls at all...


Bye
Andreas

[Jim Vincent]

>How does this explain the behaviour of non-radio-controlled model
>gloiders that return to level flight anytime? They are built perfectly
>symmetrical, have a smooth polar and no controls at all...

They have a lot more dihedral or polyhedral to help them return to level
flight.

Interestingly, a well trimmed hand launch free flight glider will climb almost
straight up, "flop" into a glide without stalling, and then start turning in a
stable, constant circle. Great fun!

Jim Vincent
CFIG
N483SZ

[Nyal Williams]

At 12:18 24 April 2004, Andreas Maurer wrote:
>On Fri, 23 Apr 2004 20:14:02 GMT, 'Bill Daniels'
>wrote:
>
>
>>A perfectly symmetrical glider with a perfectly smooth
>>polar and
>>frictionless controls SHOULD develop a spiral dive
>>from a hands off turn.
>
>How does this explain the behaviour of non-radio-controlled
>model
>gloiders that return to level flight anytime? They
>are built perfectly
>symmetrical, have a smooth polar and no controls at
>all...
>
>
>Bye
>Andreas
>

My hand-launced gliders are built with crossed controls,
which produces this effect. A slight amount of rudder
into the turn keeps it going. A slight amount of opposite
aileron keeps it from overbanking. A slight amount
of up elevator lifts the nose. Just enough weight on
the nose keeps it from making phugoids. Just enough
dihedral helps it right itself. It is not the most
effective climbing setup possible, but it produces
stability much like a sailboat with the tiller down,
the main sheet slack, and the jib tied across to the
opposite side.

It requires experimentation to get it right and they
have to be built for a left-handed or right-handed
person. It must turn to the left for a right-hander
and vice versa.

[Eric Coleson]

"Bill Daniels" > wrote in message news:<eOeic.21511$GR.2890579@attbi_s01>...
> The aerodynamics of this are interesting.
>

I was taught (and that was long enough ago for it to have passed from
fashion, apparently) that shallow, medium, and steeply banked turns
were defined by the control inputs required to maintain them, to which
the actual angles of bank are merely incidental. Shallow turns
require pro-turn aileron to maintain the angle of bank. Steep turns
require anti-turn aileron to preclude over-banking. As in level
flight, medium turns balance the converging lift vectors of wing
dihedral and require no control displacement whatever to maintain
angle of bank. This isn't to say that medium turns are stable, only
that at some particular angle of bank all lateral forces produced by a
wing with dihedral will balance about the c.g..

From an instructional standpoint, it's easy to demonstrate and serves
as a graphic intro to the subjects of stability and control. One
caution: Dont add this to the student's plate before he's in the
habit of (I mean "really learned") to manuever by applying whatever
force, rate and displacement of controls may be necessary to achieve
the desired result. This is one of those things that can get a
student to thinking too much and (except possibly for spin recoverier)
I've never seen anybody's flying improved by watching their hands and
feet while maneuvering.

Cheers,
Eric

[Martin Gregorie]

On Sat, 24 Apr 2004 14:04:11 +0200, Andreas Maurer
> wrote:

>On Fri, 23 Apr 2004 20:14:02 GMT, "Bill Daniels" >
>wrote:
>
>
>>A perfectly symmetrical glider with a perfectly smooth polar and
>>frictionless controls SHOULD develop a spiral dive from a hands off turn.
>
>How does this explain the behaviour of non-radio-controlled model
>gloiders that return to level flight anytime? They are built perfectly
>symmetrical, have a smooth polar and no controls at all...
>
Free Flight gliders - at least in the F1A class, which I fly - are not
aerodynamically symmetrical: There is always more wash in on the inner
wing in the turn and the rudder is set into the turn, giving a
crossed-controls effect. Without the differential wash-in most designs
will have nasty spiralling tendencies.

The flight regime is somewhat different, too. The model is trimmed at
min. sink (about 8-10 kts) and is flying in a still air circle that
requires 40 - 60 seconds to complete. That's a 30 - 40 m diameter
circle being made by a 2.5 m span model, which is a relatively much
larger circle than we tend to use in our sailplanes and yet is small
enough to fit easily inside a thermal column.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

[Jim Vincent]

Also, adding stab tilt helps the free flight glider turn towards the high side.

All these are tweaked in until the glider performs as desired. I also fly
Jet-X gliders, little free flight gliders with a small rocket engine attached
that burn for about 10 seconds. If done right, a thing of beauty. If not, they
loop like mad or auger in dramatically. Always fun.

>My hand-launced gliders are built with crossed controls,
>which produces this effect. A slight amount of rudder
>into the turn keeps it going. A slight amount of opposite
>aileron keeps it from overbanking. A slight amount
>of up elevator lifts the nose. Just enough weight on
>the nose keeps it from making phugoids. Just enough
>dihedral helps it right itself.



Jim Vincent
CFIG
N483SZ