What happens if a sailplane has no horiz stabilizer or elevator?

[Mark James Boyd]

There are some designs which have no horizontal stab: flying wings
for example. There are also canard setups (the speed canard, for example).

For a sailplane, I was thinking about how one might design away
the typical T-tail stabilizer and elevator.

First of all, how much dynamic stability does the horiz. stab
contribute? If it were eliminated by design, would it
be absolutely necessary to compensate by using a swept
wing (either forward or backward)? When deflected,
how much torque does an elevator provide?

I'm considering these factors, because eliminating the
elevator and stab would reduce drag. From there, one
could potentially design a ducted surface, or use moveable
weights in the tail to change C.G and therefore pitch.

In the first case (ducting), there are commonly used
NACA ducts (they look like little triangles on
power planes) that are commonly used as air vents on
power planes. They have the advantage of producing minimal
drag when the vent is closed. On a glider, they could be
used in the tail to direct airflow and produce pitching
moments. There is a tail-rotor free turbine helicopter
which uses ducted bleed-air, I believe, to control yaw this way.

The other option, which is more elegant, is to use a moveable
weight in the tail for pitch. Move the weight forward to
pitch down, backward to pitch up. One difficulty is
if the weight must be quite heavy, or the stick movement
needed to move it is too heavy. I suppose this in some
part is a function of the length of the tailboom. Another
complication is that a regular elevator is more effective at
high airspeed, and less effective at low airspeed (more
deflection is required for the same torque). This isn't
necessarily true with a weight-shift pitch control.

Hmmm...anyone have data about forces provided by the
elevator is flight? Drag caused by the elevator/ vert. stabilizer
in level flight? How about torque produced by weight shift
near the arm of the elevator?

I suppose the best way to experiment with this is in a
model glider first, then in a full scale glider with BOTH
pitch systems (elev/stab, AND weight shift). Then finally
with the elev/stab removed.

[Scott]

Nature gave birds the horizontal stabilizer, I'll stick with the birds.
"Mark James Boyd" > wrote in message
news:4001c97d$1@darkstar...
> There are some designs which have no horizontal stab: flying wings
> for example. There are also canard setups (the speed canard, for
example).
>
> For a sailplane, I was thinking about how one might design away
> the typical T-tail stabilizer and elevator.
>
> First of all, how much dynamic stability does the horiz. stab
> contribute? If it were eliminated by design, would it
> be absolutely necessary to compensate by using a swept
> wing (either forward or backward)? When deflected,
> how much torque does an elevator provide?
>
> I'm considering these factors, because eliminating the
> elevator and stab would reduce drag. From there, one
> could potentially design a ducted surface, or use moveable
> weights in the tail to change C.G and therefore pitch.
>
> In the first case (ducting), there are commonly used
> NACA ducts (they look like little triangles on
> power planes) that are commonly used as air vents on
> power planes. They have the advantage of producing minimal
> drag when the vent is closed. On a glider, they could be
> used in the tail to direct airflow and produce pitching
> moments. There is a tail-rotor free turbine helicopter
> which uses ducted bleed-air, I believe, to control yaw this way.
>
> The other option, which is more elegant, is to use a moveable
> weight in the tail for pitch. Move the weight forward to
> pitch down, backward to pitch up. One difficulty is
> if the weight must be quite heavy, or the stick movement
> needed to move it is too heavy. I suppose this in some
> part is a function of the length of the tailboom. Another
> complication is that a regular elevator is more effective at
> high airspeed, and less effective at low airspeed (more
> deflection is required for the same torque). This isn't
> necessarily true with a weight-shift pitch control.
>
> Hmmm...anyone have data about forces provided by the
> elevator is flight? Drag caused by the elevator/ vert. stabilizer
> in level flight? How about torque produced by weight shift
> near the arm of the elevator?
>
> I suppose the best way to experiment with this is in a
> model glider first, then in a full scale glider with BOTH
> pitch systems (elev/stab, AND weight shift). Then finally
> with the elev/stab removed.
>
>




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[John Galloway]

At first glance I would want some reassurance about
the the spinning characteristics and recoverability
of a weight shift pitch control glider with a conventional
wing section! Also I wouldn't fancy flying it inverted.
I think you are proposing a highly unstable and unworkable
configuration i.e. a deathtrap.

The longitudinal control would work differently at
different pitch angles. In a vertical climb or dive
there would be no 'elevator' control. In a steep dive
spin recovery the conventional wing section would bunt
uncontrollably past the vertical. The weight in the
tail would then reverse its effect and increase the
negative g loads. I think it would be so violent that
the glider wings would depart immediately but even
if they didn't you would be in a non recoverable position
just waiting to exceed VNE sufficiently for the wings
to come off a second or two later.

In fact even trying to fly in a fairly level attitude
would be extremely difficult as any forward pitching
would diminish the effect of the weight 'elevator/tailplane'
so that you would then have to send it back past the
postion of stable level flight just to stop the nose
continuing to drop. Then there's the difference in
control forces that would be needed to shift the weight
up and down the tailboom at different pitch attitudes.

Then there's high speed cruising which would increase
the pitching effect of the wing so that the weight
would have to go further and further back as the speed
increased (even neglecting pitch change effects as
above) so the faster you go the futher back the stick.


Conventional glider wing sections are unstable in pitch
and the advantage of an aerodynamic pitch trim and
control device is that it increases its effect with
airspeed and works in all attitudes. If you want to
get rid of the tail you need to use a flying wing chord
section or to use thrust vectoring (maybe that could
be a use for the jet on the other thread but it wouldn't
be a glider)

John Galloway

At 22:24 11 January 2004, Mark James Boyd wrote:
>There are some designs which have no horizontal stab:
> flying wings
>for example. There are also canard setups (the speed
>canard, for example).
>
>For a sailplane, I was thinking about how one might
>design away
>the typical T-tail stabilizer and elevator.
>
>First of all, how much dynamic stability does the horiz.
>stab
>contribute? If it were eliminated by design, would
>it
>be absolutely necessary to compensate by using a swept
>wing (either forward or backward)? When deflected,
>how much torque does an elevator provide?
>
>I'm considering these factors, because eliminating
>the
>elevator and stab would reduce drag. From there, one
>could potentially design a ducted surface, or use moveable
>weights in the tail to change C.G and therefore pitch.
>
>In the first case (ducting), there are commonly used
>NACA ducts (they look like little triangles on
>power planes) that are commonly used as air vents on
>power planes. They have the advantage of producing
>minimal
>drag when the vent is closed. On a glider, they could
>be
>used in the tail to direct airflow and produce pitching
>moments. There is a tail-rotor free turbine helicopter
>which uses ducted bleed-air, I believe, to control
>yaw this way.
>
>The other option, which is more elegant, is to use
>a moveable
>weight in the tail for pitch. Move the weight forward
>to
>pitch down, backward to pitch up. One difficulty is
>if the weight must be quite heavy, or the stick movement
>needed to move it is too heavy. I suppose this in
>some
>part is a function of the length of the tailboom.
>Another
>complication is that a regular elevator is more effective
>at
>high airspeed, and less effective at low airspeed (more
>deflection is required for the same torque). This
>isn't
>necessarily true with a weight-shift pitch control.
>
>Hmmm...anyone have data about forces provided by the
>elevator is flight? Drag caused by the elevator/ vert.
>stabilizer
>in level flight? How about torque produced by weight
>shift
>near the arm of the elevator?
>
>I suppose the best way to experiment with this is in
>a
>model glider first, then in a full scale glider with
>BOTH
>pitch systems (elev/stab, AND weight shift). Then
>finally
>with the elev/stab removed.
>
>
>

[Mark James Boyd]

In article >,
John Galloway > wrote:
>At first glance I would want some reassurance about
>the the spinning characteristics and recoverability
>of a weight shift pitch control glider with a conventional
>wing section! Also I wouldn't fancy flying it inverted.
> I think you are proposing a highly unstable and unworkable
>configuration i.e. a deathtrap.
>
>The longitudinal control would work differently at
>different pitch angles. In a vertical climb or dive
>there would be no 'elevator' control. In a steep dive
>spin recovery the conventional wing section would bunt
>uncontrollably past the vertical. The weight in the
>tail would then reverse its effect and increase the
>negative g loads. I think it would be so violent that
>the glider wings would depart immediately but even
>if they didn't you would be in a non recoverable position
>just waiting to exceed VNE sufficiently for the wings
>to come off a second or two later.

Hmmm...excellent points. I can see that both weight
shift and ducting have problems in spin recovery (a
very important area).

So two more ideas for getting around having a tail
in the way of turbine temps.:

1. Mount the turbine slightly "cockeyed" a few degrees so
the blast isn't right at the tail. Needs some rudder
for powered flight, and doesn't look elegant,
but it's a simple solution to implement.

2. Use a canard. Has anyone ever made a glider with
a canard for control before? I'm guessing maybe not
since there are some obvious disadvantages in a glider
(landouts, aerotow, turbulence caused by a canard)...

[Gary Boggs]

V tail or twin rudders on the ends of the horizontal stabilizer makes the
most sense to me.


"Mark James Boyd" > wrote in message
news:4001c97d$1@darkstar...
There are some designs which have no horizontal stab: flying wings
for example. There are also canard setups (the speed canard, for example).

For a sailplane, I was thinking about how one might design away
the typical T-tail stabilizer and elevator.

First of all, how much dynamic stability does the horiz. stab
contribute? If it were eliminated by design, would it
be absolutely necessary to compensate by using a swept
wing (either forward or backward)? When deflected,
how much torque does an elevator provide?

I'm considering these factors, because eliminating the
elevator and stab would reduce drag. From there, one
could potentially design a ducted surface, or use moveable
weights in the tail to change C.G and therefore pitch.

In the first case (ducting), there are commonly used
NACA ducts (they look like little triangles on
power planes) that are commonly used as air vents on
power planes. They have the advantage of producing minimal
drag when the vent is closed. On a glider, they could be
used in the tail to direct airflow and produce pitching
moments. There is a tail-rotor free turbine helicopter
which uses ducted bleed-air, I believe, to control yaw this way.

The other option, which is more elegant, is to use a moveable
weight in the tail for pitch. Move the weight forward to
pitch down, backward to pitch up. One difficulty is
if the weight must be quite heavy, or the stick movement
needed to move it is too heavy. I suppose this in some
part is a function of the length of the tailboom. Another
complication is that a regular elevator is more effective at
high airspeed, and less effective at low airspeed (more
deflection is required for the same torque). This isn't
necessarily true with a weight-shift pitch control.

Hmmm...anyone have data about forces provided by the
elevator is flight? Drag caused by the elevator/ vert. stabilizer
in level flight? How about torque produced by weight shift
near the arm of the elevator?

I suppose the best way to experiment with this is in a
model glider first, then in a full scale glider with BOTH
pitch systems (elev/stab, AND weight shift). Then finally
with the elev/stab removed.

[Bob Kuykendall]

One of the guys at the forefront of tailless sailplane
design is Jim Marske. He's been experimenting with
most of the ideas you bring up, including the movable
trim weight. He regularly offers seminars on tailless
sailplane design.

Bob K.
http://www.hpaircraft.com

[Andreas Maurer]

On Sun, 11 Jan 2004 17:11:11 -0800, "Gary Boggs"
> wrote:

>V tail or twin rudders on the ends of the horizontal stabilizer makes the
>most sense to me.

Interference drag is pretty bad in both cases.

Bye
Andreas

[Chip Fitzpatrick]

Check out the German Horten's from WWII. They test flew flying wings
as gliders and were planning jet versions. Very interesting piece
discussing them on the History Channel this evening.

Chip Fitzpatrick

[Larry Pardue]

"Mark James Boyd" > wrote in message
news:4001f9e3$1@darkstar...

>
> 2. Use a canard. Has anyone ever made a glider with
> a canard for control before? I'm guessing maybe not
> since there are some obvious disadvantages in a glider
> (landouts, aerotow, turbulence caused by a canard)...
>
>
Yep, Burt Rutan. The Solitaire. Good designer, but this effort was not
covered with glory. Gliders need to fly right at the edge of a stall.
http://www.sailplanedirectory.com/zwfmot.htm

Larry Pardue 2I

[Neal Pfeiffer]

The Horten flying wings utilized a non-optimal spanload distribution
(wingtips loaded downward) in order to be stable, effectively a tail at
the wingtips. Because of this, their performance was not particularly good.

The Swift (see reference below) is a more modern flying wing that
addresses some of the shortcomings of the earlier ones.
http://aero.stanford.edu/Reports/SWIFTArticle1991.html

Other tailess glider variations were done by Al Backstrom (the Flying
Plank) and Jim Marske (Pioneer & Monarch).
http://www.nurflugel.com/Nurflugel/Fauvel/e_backstrom.htm
http://www.flyingacesclub.net/alamo/fullsizeflyingwingstuff.htm
http://www.continuo.com/marske/

or for the committed flying-wing person:
http://www.nurflugel.com/nurflugel/nurflugel.html

- - - - - - -

Moving of weights within a fuselage (or other part of the aircraft) is
not a viable solution. Response needs to be quick and reliable, even
for unusual attitudes.

- - - - - - -

Based on the vast majority of the gliders in existance, however, using a
correctly-sized tail is not a bad way to go. Remember, if you don't
truly enjoy what you're flying, you probably won't fly it long. Tailed
aircraft are probably easier to make fly good.


...... Neal

Mark James Boyd wrote:

> There are some designs which have no horizontal stab: flying wings
> for example. There are also canard setups (the speed canard, for example).
>
> For a sailplane, I was thinking about how one might design away
> the typical T-tail stabilizer and elevator.
>
> First of all, how much dynamic stability does the horiz. stab
> contribute? If it were eliminated by design, would it
> be absolutely necessary to compensate by using a swept
> wing (either forward or backward)? When deflected,
> how much torque does an elevator provide?
>
> I'm considering these factors, because eliminating the
> elevator and stab would reduce drag. From there, one
> could potentially design a ducted surface, or use moveable
> weights in the tail to change C.G and therefore pitch.
>
> In the first case (ducting), there are commonly used
> NACA ducts (they look like little triangles on
> power planes) that are commonly used as air vents on
> power planes. They have the advantage of producing minimal
> drag when the vent is closed. On a glider, they could be
> used in the tail to direct airflow and produce pitching
> moments. There is a tail-rotor free turbine helicopter
> which uses ducted bleed-air, I believe, to control yaw this way.
>
> The other option, which is more elegant, is to use a moveable
> weight in the tail for pitch. Move the weight forward to
> pitch down, backward to pitch up. One difficulty is
> if the weight must be quite heavy, or the stick movement
> needed to move it is too heavy. I suppose this in some
> part is a function of the length of the tailboom. Another
> complication is that a regular elevator is more effective at
> high airspeed, and less effective at low airspeed (more
> deflection is required for the same torque). This isn't
> necessarily true with a weight-shift pitch control.
>
> Hmmm...anyone have data about forces provided by the
> elevator is flight? Drag caused by the elevator/ vert. stabilizer
> in level flight? How about torque produced by weight shift
> near the arm of the elevator?
>
> I suppose the best way to experiment with this is in a
> model glider first, then in a full scale glider with BOTH
> pitch systems (elev/stab, AND weight shift). Then finally
> with the elev/stab removed.
>
>

[André Somers]

Scott wrote:

> Nature gave birds the horizontal stabilizer, I'll stick with the birds.
Nature also gave them flapping wings. Did you fly an aircraft that uses that
principle?

André

[Joeri Cools]

Nature didn't invent the weel, I suppose you don't have legs under your car
?

"Scott" > schreef in bericht
...
> Nature gave birds the horizontal stabilizer, I'll stick with the birds.
> "Mark James Boyd" > wrote in message
> news:4001c97d$1@darkstar...
> > There are some designs which have no horizontal stab: flying wings
> > for example. There are also canard setups (the speed canard, for
> example).
> >
> > For a sailplane, I was thinking about how one might design away
> > the typical T-tail stabilizer and elevator.
> >
> > First of all, how much dynamic stability does the horiz. stab
> > contribute? If it were eliminated by design, would it
> > be absolutely necessary to compensate by using a swept
> > wing (either forward or backward)? When deflected,
> > how much torque does an elevator provide?
> >
> > I'm considering these factors, because eliminating the
> > elevator and stab would reduce drag. From there, one
> > could potentially design a ducted surface, or use moveable
> > weights in the tail to change C.G and therefore pitch.
> >
> > In the first case (ducting), there are commonly used
> > NACA ducts (they look like little triangles on
> > power planes) that are commonly used as air vents on
> > power planes. They have the advantage of producing minimal
> > drag when the vent is closed. On a glider, they could be
> > used in the tail to direct airflow and produce pitching
> > moments. There is a tail-rotor free turbine helicopter
> > which uses ducted bleed-air, I believe, to control yaw this way.
> >
> > The other option, which is more elegant, is to use a moveable
> > weight in the tail for pitch. Move the weight forward to
> > pitch down, backward to pitch up. One difficulty is
> > if the weight must be quite heavy, or the stick movement
> > needed to move it is too heavy. I suppose this in some
> > part is a function of the length of the tailboom. Another
> > complication is that a regular elevator is more effective at
> > high airspeed, and less effective at low airspeed (more
> > deflection is required for the same torque). This isn't
> > necessarily true with a weight-shift pitch control.
> >
> > Hmmm...anyone have data about forces provided by the
> > elevator is flight? Drag caused by the elevator/ vert. stabilizer
> > in level flight? How about torque produced by weight shift
> > near the arm of the elevator?
> >
> > I suppose the best way to experiment with this is in a
> > model glider first, then in a full scale glider with BOTH
> > pitch systems (elev/stab, AND weight shift). Then finally
> > with the elev/stab removed.
> >
> >
>
>
>
>
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> http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
> -----== Over 100,000 Newsgroups - 19 Different Servers! =-----

[Chris OCallaghan]

Mark,

I've been hitting the books lately. I've just read Aerodynamics for
Naval Aviators (ASA). An excellent treatment of aerodynamics for the
aviator without the oversimplification one typcially sees in most
"learn to fly" books.

It has sections on static and dynamic stability that will help give
you a better grounding for exploring the questions you've asked. And
frankly, it's not bad reading. I was very surprised. Not nearly as
dessicated as I feared. A good addition to any pilot's personal
library.

BTW, it's easy to do the math to figure out what kind of loads you'll
need to produce on the tail to maintain pitch control. Use your weight
and balance calculations to exptrapolate approximations of the moment
arm between cg and center of lift, then match torques with the tail's
moment arm. Repeat this process for a load factor of two or three
(steep turns) and you'll find that you'll need to move a lot of mass
quickly and quite a distance to stay in trim. Just not very practical.
But interesting thoughts.

OC

[Slingsby]

Neal Pfeiffer > wrote in message >...


> Moving of weights within a fuselage (or other part of the aircraft) is
> not a viable solution. Response needs to be quick and reliable, even
> for unusual attitudes.
************************************************** *****************************
Moveable weights for pitch control aren't as responsive in the
negative pitch airfoils used in conventional gliders because
increasing speed increases the downward pitching moment which the wing
produces. Moving the weight forward to drop the nose and increase
speed leads to the requirement for back stick to increase downward
pressure on the horizontal stab and keep the nose from continuing to
drop. If you tried to do this only with weight shift, you would need
to move the weights forward to increase speed and then progressively
move the weight backward as the speed builds up just to maintain
stability. Computerized fuel shifting on airlines does this but they
still use all-flying-tails for the fine corrections.

Weight shifting for pitch control is very workable in flying-wing type
gliders as they are very responsive to changes in cg; and the inherent
stability of the reflex wing keeps the glider very close to the weight
shifted pitch.(and speed) Several Genesis owners use rudimentary forms
of weight shift on a regular basis. One has mentioned putting ankle
weights on the rudder pedals and moving them back and forth, someone
else has stated in the GenesisFlyers Yahoo Groups site that inflating
the lumbar support adds 4 knots to the trimmed speed. There have been
discussions about using nose and tail water tanks and shifting from
one to the other to trim for best thermalling or high speed. This is
a very workable improvement for Genesis 2 and Marske Pioneer type
gliders. Weight shifting on the Pioneer may work even better as it
may be possible to fly with a very aft cg which keeps the nose high
and then use forward stick to deflect the elevators down increasing
the lift coeffecient of the wing. Moving the weight forward would then
allow it to fly fast with the elevators slightly raised the way
flapped gliders fly with negative flaps.(reflex)

> Based on the vast majority of the gliders in existance, however, using a
> correctly-sized tail is not a bad way to go. Remember, if you don't
> truly enjoy what you're flying, you probably won't fly it long. Tailed
> aircraft are probably easier to make fly good.
************************************************** ******************************
It's hard to argue against correctly-sized tails, although I suspect
that what you call "correctly-sized" is what I spitefully and
maliciously call a boomsnapper. Boomsnappers interfere with low
energy landings as your pitch at flair is limited by your willingness
to slam down tail first and damage the boom. Some boomsnappers (G
102) are speed limited because, oops!, the elevator isn't as strong as
we thought and it is prone to flutter. The G103 Acro is acro no more
because that big heavy extremely strong tail boom isn't as strong as
it should be. Need to slap on a few more layers of carbon so's it
don't come off.
So, how strong and durable are those tiny, light weight tail booms on
newer high performance gliders? Are they at least as strong as the
wing spars on Shemp-Hirth gliders? How strong will they be when they
are as old as Grobs?
Got to keep that tape on tight, too, cause lifting of the front edge
of tape near the elevator causes an almost total loss of elevator
authority.
Genesis 2 and Pioneer owners all seem to really like the handling
characteristics of their flying-wing gliders and as a group they don't
seem to miss or wish they had longer tail booms.

Long tailed aircraft are certainly easier to make and they satisfy an
esthetic which sees ships, trains and trucks as boxes or tubes which
carry cargo, so an aircraft should be a box or tube with wings. The
more it looks like a truck the safer it "feels".

[Mark James Boyd]

In article >,
Chris OCallaghan > wrote:
>Mark,
>
>I've been hitting the books lately. I've just read Aerodynamics for
>Naval Aviators (ASA). An excellent treatment of aerodynamics for the
>aviator without the oversimplification one typcially sees in most
>"learn to fly" books.

An excellent book. The only place I found the equation for
the relationship between weight and stall speed. Good
stuff about the different effects of different types of
flaps. Too bad it's buried in the "abyss" (my garage)
due to new space needs (bassinet, changing table, laundry basket,
mom's cozy chair...)

:)

New pilots aren't hard to train, but they sure take a long
time to GROW!

[Erwin Janssen]

In article >,
says...
> Scott wrote:
>
> > Nature gave birds the horizontal stabilizer, I'll stick with the birds.
> Nature also gave them flapping wings. Did you fly an aircraft that uses that
> principle?

Centrair got pretty close with their Pegasus :)

Erwin

[Chris OCallaghan]

Whoops, a case of typing faster than I was thinking... Ignore the
second half of the last paragraph... it's a misplaced fragment from
another train of thought.

(Chris OCallaghan) wrote in message >...
> Mark,
>
> I've been hitting the books lately. I've just read Aerodynamics for
> Naval Aviators (ASA). An excellent treatment of aerodynamics for the
> aviator without the oversimplification one typcially sees in most
> "learn to fly" books.
>
> It has sections on static and dynamic stability that will help give
> you a better grounding for exploring the questions you've asked. And
> frankly, it's not bad reading. I was very surprised. Not nearly as
> dessicated as I feared. A good addition to any pilot's personal
> library.
>
> BTW, it's easy to do the math to figure out what kind of loads you'll
> need to produce on the tail to maintain pitch control. Use your weight
> and balance calculations to exptrapolate approximations of the moment
> arm between cg and center of lift, then match torques with the tail's
> moment arm. Repeat this process for a load factor of two or three
> (steep turns) and you'll find that you'll need to move a lot of mass
> quickly and quite a distance to stay in trim. Just not very practical.
> But interesting thoughts.
>
> OC

[Denis Flament]

Mark James Boyd wrote:

> I'm considering these factors, because eliminating the
> elevator and stab would reduce drag.

That's right.

You should also consider eliminating the wings, that would reduce even
more drag.

> I suppose the best way to experiment with this is in a
> model glider first,

Well... I suppose too... if you want to experiment this with a full
scale glider, it will be difficult to find a pilot to put in ;-)


--
Denis

R. Parce que ça rompt le cours normal de la conversation !!!
Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

[Mark James Boyd]

In article >,
Denis Flament > wrote:
>Mark James Boyd wrote:
>
>> I'm considering these factors, because eliminating the
>> elevator and stab would reduce drag.
>
>That's right.
>
>You should also consider eliminating the wings, that would reduce even
>more drag.

An interesting, but more challenging, idea...
An aerodyne without wings...hmmm...

>
>> I suppose the best way to experiment with this is in a
>> model glider first,
>
>Well... I suppose too... if you want to experiment this with a full
>scale glider, it will be difficult to find a pilot to put in ;-)

>Denis

Hmmm...methinks some sort of pully system in a plain old glider
might do it. Get a weight of the right size so that
if it lodges in the tail, you are still within safe CG, and if
it lodges in the nose, you are still within safe CG.

Maybe this is only a 1 pound weight. Then have an additional control
which moves this weight. Go up to altitude and see if moving
this weight gives sufficient control.

The biggest safety feature would be ensuring the weight didn't
come loose during a critical phase of flight (near the ground)
and your supplementary "weight" cables don't hinder
the original controls in any way...

A weight right in the tail which moves maybe 3 feet forward
when the auxiliary stick is moved might do it. Hmmm...

[Bill Daniels]

Denis, you should read up on the French designer Charles Fauvell and his
flying wings. They flew pretty well although I think Jim Marske's designs
are showing higher performance.

Tailless designs fly quite well and the performance really doesn't suffer.
They would be perfect for small jet engine self launchers.

Bill Daniels


"Denis Flament" > wrote in message
...
> Mark James Boyd wrote:
>
> > I'm considering these factors, because eliminating the
> > elevator and stab would reduce drag.
>
> That's right.
>
> You should also consider eliminating the wings, that would reduce even
> more drag.
>
> > I suppose the best way to experiment with this is in a
> > model glider first,
>
> Well... I suppose too... if you want to experiment this with a full
> scale glider, it will be difficult to find a pilot to put in ;-)
>
>
> --
> Denis
>
> R. Parce que ça rompt le cours normal de la conversation !!!
> Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

[Denis Flament]

Bill Daniels wrote:

> Denis, you should read up on the French designer Charles Fauvell and his
> flying wings. They flew pretty well although I think Jim Marske's designs
> are showing higher performance.
>
> Tailless designs fly quite well and the performance really doesn't suffer.
> They would be perfect for small jet engine self launchers.

Hi Bill

Yes I know that Fauvel "ailes volantes" like the glider AV36, and other
flying wings like Horten's fly quite well.

But I still doubt that suppressing the tail means suppressing the trim
drag of an airplane. Flying wings have to use stable wing profiles (with
positive pitching moment) and these produce more extra drag than a
tailplane.

Things are not so simple...

--
Denis

R. Parce que ça rompt le cours normal de la conversation !!!
Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

[Andreas Maurer]

On 14 Jan 2004 20:15:24 -0700, (Mark James Boyd)
wrote:

>Hmmm...methinks some sort of pully system in a plain old glider
>might do it. Get a weight of the right size so that
>if it lodges in the tail, you are still within safe CG, and if
>it lodges in the nose, you are still within safe CG.

>Maybe this is only a 1 pound weight. Then have an additional control
>which moves this weight. Go up to altitude and see if moving
>this weight gives sufficient control.


Just imagine what forces your movable weight will exert under a g load
different than 1? For example, when you are flying through a vertical
gust?

This is precisely the cause why your idea cannot work - and why the
pilot of a hang glider is hanging so far *below* his wing.



>The biggest safety feature would be ensuring the weight didn't
>come loose during a critical phase of flight (near the ground)
>and your supplementary "weight" cables don't hinder
>the original controls in any way...
>
>A weight right in the tail which moves maybe 3 feet forward
>when the auxiliary stick is moved might do it. Hmmm...


Have you ever thought about what is regarded as the most important
invention of the Wright brothers?
You name it - aerodynamical control around all three axes.

There's a good cause why there was never such a system that ever
worked on an aircraft, although thousands of designers have tried it
in the pas 120 years.


Bye
Andreas

[Mark James Boyd]

Andreas Maurer > wrote:
>On 14 Jan 2004 20:15:24 -0700, (Mark James Boyd)
>wrote:
>
>Just imagine what forces your movable weight will exert under a g load
>different than 1? For example, when you are flying through a vertical
>gust?

I'd imagine it will behave the same as an attached one pound ballast
weight on the upper part of the rudder of the glider used to
balance the rudder. Perhaps I'm missing your point here...

>
>This is precisely the cause why your idea cannot work - and why the
>pilot of a hang glider is hanging so far *below* his wing.
>

Now this a very interesting point. Whether the weight is above
or below the C.G. seems to also have an effect. Thank you
Andreas...

>>The biggest safety feature would be ensuring the weight didn't
>>come loose during a critical phase of flight (near the ground)
>>and your supplementary "weight" cables don't hinder
>>the original controls in any way...
>>
>>A weight right in the tail which moves maybe 3 feet forward
>>when the auxiliary stick is moved might do it. Hmmm...
>
>
>Have you ever thought about what is regarded as the most important
>invention of the Wright brothers?
>You name it - aerodynamical control around all three axes.

It seems this weight shift idea is just a very fine refinement.
It's intention is to reduce that tiny bit of additional
drag caused by moving surfaces or trim. I agree this is
not anywhere near "the most important invention," but just a
fun winter mind-teaser.

>There's a good cause why there was never such a system that ever
>worked on an aircraft, although thousands of designers have tried it
>in the pas 120 years.

Well, it has worked to improve the efficiency in cruise of
modern jet airliners, and has helped my fuel efficiency in
my 172 across the country, but perhaps, as you point out, not
as a primary control (for pitch in these cases). Except for
ultralights and powered parachutes (which have a low hanging weight)
we don't see it used in modern aircraft.
Perhaps you are right, the standard glider design
(with no low hanging weight) doesn't lend itself well
to this means of control...

>Andreas

Thanks for your thoughts!

Mark

[Mark James Boyd]

Bill Daniels > wrote:
>Denis, you should read up on the French designer Charles Fauvell and his
>flying wings. They flew pretty well although I think Jim Marske's designs
>are showing higher performance.
>
>Tailless designs fly quite well and the performance really doesn't suffer.
>They would be perfect for small jet engine self launchers.
>
>Bill Daniels

There are some obvious reasons not to use a canard (towrope tangling,
landout damage, creates turbulence before the wing) but this
seems an option as well... I've only flown one canard aircraft,
(and never a flying wing) so I may delve into this more...

[Martin Gregorie]

On 18 Jan 2004 11:57:22 -0700, (Mark James Boyd)
wrote:

>Bill Daniels > wrote:
>>Denis, you should read up on the French designer Charles Fauvell and his
>>flying wings. They flew pretty well although I think Jim Marske's designs
>>are showing higher performance.
>>
>>Tailless designs fly quite well and the performance really doesn't suffer.
>>They would be perfect for small jet engine self launchers.
>>
>>Bill Daniels
>
>There are some obvious reasons not to use a canard (towrope tangling,
>landout damage, creates turbulence before the wing) but this
>seems an option as well... I've only flown one canard aircraft,
>(and never a flying wing) so I may delve into this more...

The other reason is that, regardless of layout, the forward flying
surface always operates at a higher AOA in a stable trim, and this
usually results in the rear plane flying at a lower than optimal AOA.
As a canard has most of its surface in the rear plane its difficult to
get good glide performance under these conditions - certainly this has
tended to be the case in the model world.

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

[Andreas Maurer]

On 18 Jan 2004 11:53:31 -0700, (Mark James Boyd)
wrote:


>>Just imagine what forces your movable weight will exert under a g load
>>different than 1? For example, when you are flying through a vertical
>>gust?
>
>I'd imagine it will behave the same as an attached one pound ballast
>weight on the upper part of the rudder of the glider used to
>balance the rudder. Perhaps I'm missing your point here...

You are correct - but you have the horizontal stab that dampens the
motion (remember that the whole fuselage and tail acts as a weight!).

This is the cause why you need something aerodynamical to control your
pitch, and why weight shifting does not work.

It does not matter whether the damping is done by a horizontal
stabilizier or the airfoil/wing design of a flying wing.


>Now this a very interesting point. Whether the weight is above
>or below the C.G. seems to also have an effect.

Yes - and don't forget that the control authority of hang gliders is
extremely limited. If the gravity vector is not pointing "downwards"
(seen from the pilot's coordinate system) they have absolutely no
control at all. Inverted flight is out of question, and they are able
to fly their loopings only with some tricks.


>It seems this weight shift idea is just a very fine refinement.
>It's intention is to reduce that tiny bit of additional
>drag caused by moving surfaces or trim. I agree this is
>not anywhere near "the most important invention," but just a
>fun winter mind-teaser.

This is what is already being done - by water ballast in the tail that
fixes the CG at a position that is close to perfect for all flight
situations.
There have already trials been made (with ASH-25) to determine the
influence of performance of different CG positions in different
situations (cruise, climb, thermalling), and the inluence was nearly
immeasurably if the CG was moved to a supposedly "more optimum"
forward position during cruise.
The performance gain in a glider with rearward CG is (as you point out
for Cessan and airliners) often dramatic, especially in climb rate.




Bye
Andreas

[Roy]

"Andreas Maurer" > wrote in message
...
> On 18 Jan 2004 11:53:31 -0700, (Mark James Boyd)
> wrote:
>
>
> >>Just imagine what forces your movable weight will exert under a g load
> >>different than 1? For example, when you are flying through a vertical
> >>gust?
> >
> >I'd imagine it will behave the same as an attached one pound ballast
> >weight on the upper part of the rudder of the glider used to
> >balance the rudder. Perhaps I'm missing your point here...
>
> You are correct - but you have the horizontal stab that dampens the
> motion (remember that the whole fuselage and tail acts as a weight!).
>
> This is the cause why you need something aerodynamical to control your
> pitch, and why weight shifting does not work.
>
> It does not matter whether the damping is done by a horizontal
> stabilizier or the airfoil/wing design of a flying wing.
>
>
> >Now this a very interesting point. Whether the weight is above
> >or below the C.G. seems to also have an effect.
>
> Yes - and don't forget that the control authority of hang gliders is
> extremely limited. If the gravity vector is not pointing "downwards"
> (seen from the pilot's coordinate system) they have absolutely no
> control at all. Inverted flight is out of question, and they are able
> to fly their loopings only with some tricks.

Twaddle !
There are guys who fly HG inverted (they are complete nutters, but the point
is, it can be done)
Looping a HG requires 2 things,
1) speed
2) balls
fly very very, very fast, allow the bar to come forwards _slowly_ then
accelerate towards a full aft CofG position in a _controlled_ manner. (that
way you can do 54 consecutive loops in a HG) ((if you start high enough))

The CofG on a tailess aircraft (i.e. hangglider) is only secondary in the
control of VNE and stall, CofG is used for trimming but the primary speed
control of the wing is performed by the washout at the tips and on older
gliders through "luff lines" acting as "up elevator" as the speed built up
(not really used much these days)

bottom line, with a swept wing platform you can _make_ it operate within a
set airspeed range by limiting it's AUW and setting the AofA along the wing
section.

regards
Roy

[Francisco De Almeida]

Mark Boyd wrote:

>Hmmm...anyone have data about forces provided by the
>elevator is flight?=20

For the lift on the tail of an LS7 (standard class), see the last column =
of the table below. In a nutshell, in very slow flight the tail provides =
about 8 kgf (18 pounds) upward force, and at VNE, about 60 kgf (130 =
pounds) downward force.
These numbers are approximate, as the major influence is caused by the =
main wing pitching moment, which I estimated using xfoil and a single =
section approximation of the wing profile.

Francisco de Almeida
"C1" and "7"


IDA [33.3 daN/m2]
=20
Flight param @ min weight
=20
Wing
=20
for "111-1024"
=20
Drag
=20
=20
=20
=20
Horizontal tail
=20
=20
LD
s
Drag IDA
Power
V
=20
Pd
Rewing
CLW
a
CdW
CmW
Cdi
LD
profile
induced
parasite
Drag
s
M
CLH
LH
=20
-
ms-1
N
kW
kmh-1
ms-1
Pa
-
-
deg
-
-
-
-
N
N
N
N
ms-1
Nm
-
N
=20
23.9
0.84
144
2.9
72
20.1
247
921,632
1.346
7.5
0.0200
-0.116
0.0270
26
48
65
9
122
0.76
-279
0.30
78
=20
32.7
0.68
106
2.3
80
22.2
302
1,019,787
1.100
5.3
0.0090
-0.110
0.0180
36
26
53
11
91
0.62
-324
0.21
67
=20
39.7
0.63
87
2.2
90
25.0
383
1,147,260
0.869
3.4
0.0070
-0.105
0.0112
39
26
42
15
82
0.64
-391
0.13
50
=20
41.5
0.67
83
2.3
100
27.8
473
1,274,734
0.704
2.0
0.0059
-0.101
0.0074
41
27
34
18
79
0.68
-464
0.06
32
=20
40.2
0.76
86
2.6
110
30.6
572
1,402,207
0.582
1.0
0.0056
-0.099
0.0050
40
31
28
22
81
0.77
-551
0.02
10
=20
38.3
0.87
90
3.0
120
33.3
681
1,529,680
0.489
0.3
0.0054
-0.097
0.0036
38
36
24
26
85
0.88
-642
-0.02
-13
=20
35.4
1.02
98
3.5
130
36.1
799
1,657,154
0.416
-0.3
0.0051
-0.095
0.0026
36
40
20
30
90
1.01
-738
-0.04
-37
=20
33.0
1.18
105
4.1
140
38.9
926
1,784,627
0.359
-0.8
0.0049
-0.093
0.0019
33
44
17
35
97
1.16
-838
-0.06
-62
=20
30.6
1.36
113
4.7
150
41.7
1063
1,912,100
0.313
-1.2
0.0050
-0.092
0.0015
30
52
15
40
107
1.38
-952
-0.08
-90
=20
28.0
1.59
124
5.5
160
44.4
1210
2,039,574
0.275
-1.5
0.0050
-0.091
0.0011
27
59
13
46
118
1.62
-1071
-0.10
-120
=20
24.9
1.9
139
6.6
170
47.2
1366
2,167,047
0.244
-1.7
0.0053
-0.090
0.0009
24
70
12
52
134
1.95
-1196
-0.11
-151
=20
20.1
2.49
172
8.6
180
50.0
1531
2,294,521
0.217
-2.0
0.0057
-0.089
0.0007
21
84
10
58
153
2.36
-1326
-0.12
-184
=20
17.7
2.98
195
10.3
190
52.8
1706
2,421,994
0.195
-2.2
0.0057
-0.088
0.0006
19
95
9
65
169
2.75
-1461
-0.12
-218
=20

=20
=20
=20
200
55.6
1890
2,549,467
0.176
-2.3
0.0057
-0.088
0.0005
17
106
8
72
186
3.19
-1619
-0.13
-257
=20

=20
=20
=20
210
58.3
2084
2,676,941
0.160
-2.4
0.0075
-0.088
0.0004
14
152
8
79
239
4.31
-1785
-0.14
-298
=20

=20
=20
=20
220
61.1
2287
2,804,414
0.145
-2.6
0.0090
-0.087
0.0003
11
200
7
87
294
5.55
-1936
-0.14
-336
=20

=20
=20
=20
250
69.4
2954
3,186,834
0.113
-2.8
0.0090
-0.086
0.0002
9
259
5
112
376
8.07
-2472
-0.15
-470
=20

=20
=20
=20
270
75.0
3445
3,441,781
0.097
-3.0
0.0089
-0.085
0.0001
7
298
5
131
=20
=20
-2849
-0.16
-565
=20

[Steve Bralla]

Andreas Maurer > writes:

>
>This is the cause why you need something aerodynamical to control your
>pitch, and why weight shifting does not work.
>

Remember, with weight-shift control, if you are weightless, you are out of
control. That's why it gets very "interesting" in a hang glider whenever you
go weightless.

Steve

[Andreas Maurer]

On Mon, 19 Jan 2004 17:51:30 +0000 (UTC), "Roy"
> wrote:

>
>Twaddle !
>There are guys who fly HG inverted (they are complete nutters, but the point
>is, it can be done)

I'm talking about a *sustained* inverted flight, not a 4g loop where
the inverted part takes one second.

The loops you describe can also be done with a paraglider (where
inverted flight is obviously a little... problematic).



Bye
Andreas