Wing dihedral

I've often wondered how 2 channel R/C works without ailerons (obviously
well enough, right?)

I know a guy with a Yak-52, and I've noticed what looks like an almost
complete lack of dihedral on its wing. I suppose that has a lot to do
with its stability (or lack thereof?) The Chinese version (Nanchang)
has dihedral starting on approx the outer 1/3rd of its span IIRC.

Only because the a/c is slipping - the vertical/horizontal component of
lift stuff misses the point

Chris Wells wrote:
The higher wing has less AOA.

I agree completely - it's about the slip created and how dihedral
responds to it.

Dallas wrote:
"William Snow"

Give some thought to the components of lift, on both wings, and to which
direction lift acts. ;-)

http://makeashorterlink.com/?B25A35DCC

I have. I see no forces presented in this illustration that would change
the components of lift on the wings or it's direction that would cause the
aircraft to roll back to horizontal.

Why would a horizontal wing create "more effective lift" than a banked wing?

2 channel (w/o ailerons) works great. You'll never see a aileron-less
model without dihedral (I understand swept wings work too but I've never
seen that).

single channel works too - how does one do a loop with rudder-only?
Quite well thank you.

Acrobatic R/C with a normal configuration a/c are often straight winged
or close too it. That's to isolate the function of the rudder so it
causes yaw only. Works pretty well except for some effects from
fuselage blanking and such.

But that's when R/C aircraft were mosting just trying to model full
scale aircraft. That balloon was busted a long time ago. What is this?

http://youtube.com/watch?v=K6besEwoR...c%20hydroplane

wrote:
I've often wondered how 2 channel R/C works without ailerons (obviously
well enough, right?)

I know a guy with a Yak-52, and I've noticed what looks like an almost
complete lack of dihedral on its wing. I suppose that has a lot to do
with its stability (or lack thereof?) The Chinese version (Nanchang)
has dihedral starting on approx the outer 1/3rd of its span IIRC.

"Dallas"

Why would a horizontal wing create "more effective lift" than a banked
wing?

Let's think of a set of wings with a dihedral angle of 10 degrees up from
horizontal, on both wings.

Now, think of the shadow the wings would make, if the sun were straight
overhead, while the plane is banked at 10 degrees. The wing that is up
would make a smaller shadow than if the plane were flying level. The wing
that is down would be making the largest shadow that is possible.

The size of the shadow is the only size that is important, because the lift
that is straight up (towards the sun, in our example) is the only lift that
will be important to the plane, as that is what is counteracting the force
of gravity. The fact that the down wing's shadow is larger, will make have
more effective area than the up wing, and will tend to bring that wing back
up.

While you are in level flight, the same thing will constantly be at work,
automatically trying to keep the plane level.
--
Jim in NC

It's a coherent description but I think it's inaccurate. The sum of the
lift vectors is now simply tilted from the vertical aircraft will
simply turn.

I agree that dihedral will have a stabilizing effect but it's not
because more of the wing low wing is parallel to the earth. It's
because the a/c slips towards the inside of the turn (controls being
neutral). The slip gives the low wing a higher angle of attack, thus
more lift and it will tend to right itself.

Conversely, a wing with dihedral will tend to bank if the aircraft is
yawed with the rudder. Left rudder, right skid, right wing has higher a
of a in relation to relative wind and the aircraft banks left.

Fold a hersey bar sized piece of paper to simulate such a wing. Then
slip and skid it and imagine the a of a on each panel.

Morgans wrote:
"Dallas"

Why would a horizontal wing create "more effective lift" than a banked

wing?

Let's think of a set of wings with a dihedral angle of 10 degrees up from
horizontal, on both wings.

Now, think of the shadow the wings would make, if the sun were straight
overhead, while the plane is banked at 10 degrees. The wing that is up
would make a smaller shadow than if the plane were flying level. The wing
that is down would be making the largest shadow that is possible.

The size of the shadow is the only size that is important, because the lift
that is straight up (towards the sun, in our example) is the only lift that
will be important to the plane, as that is what is counteracting the force
of gravity. The fact that the down wing's shadow is larger, will make have
more effective area than the up wing, and will tend to bring that wing back
up.

While you are in level flight, the same thing will constantly be at work,
automatically trying to keep the plane level.

Take a look at the NASA item in the following threads. It should be apparent
what happens. L1L2 therefore L1 wing rises until L1=L2. I can not believe
all of this discussion has ensued. This is a fundamental of aircraft design.

"Dallas" wrote in message
ink.net...

"William Snow"
Give some thought to the components of lift, on both wings, and to which
direction lift acts. ;-)
http://makeashorterlink.com/?B25A35DCC

I have. I see no forces presented in this illustration that would change
the components of lift on the wings or it's direction that would cause the
aircraft to roll back to horizontal.

Why would a horizontal wing create "more effective lift" than a banked
wing?

This thread began in another group and some interesting points were
discussed, but I honestly expected a few belly laughs here on the
absurdity
of this book's explanation.


Dallas

Take a look at "Aerodynamics for Naval Aviators" NAVWEPS 00-80T-00, Page
295....

"Maule Driver" wrote in message
m...
2 channel (w/o ailerons) works great. You'll never see a aileron-less
model without dihedral (I understand swept wings work too but I've never
seen that).

single channel works too - how does one do a loop with rudder-only? Quite
well thank you.

Acrobatic R/C with a normal configuration a/c are often straight winged or
close too it. That's to isolate the function of the rudder so it causes
yaw only. Works pretty well except for some effects from fuselage
blanking and such.

But that's when R/C aircraft were mosting just trying to model full scale
aircraft. That balloon was busted a long time ago. What is this?

http://youtube.com/watch?v=K6besEwoR...c%20hydroplane

wrote:
I've often wondered how 2 channel R/C works without ailerons (obviously
well enough, right?)

I know a guy with a Yak-52, and I've noticed what looks like an almost
complete lack of dihedral on its wing. I suppose that has a lot to do
with its stability (or lack thereof?) The Chinese version (Nanchang)
has dihedral starting on approx the outer 1/3rd of its span IIRC.

It is clearly explained in "Aerodynamics for Naval Aviators", NAVWEPS
00-80T-00, page 295....



"Dallas" wrote in message
nk.net...
Would anyone care to comment on the accuracy of this illustration of how
wing dihedral works from a 1981 Jeppesen Sanderson book.

http://makeashorterlink.com/?B25A35DCC

The accompanying statement reads:
"When an aircraft with dihedral rolls so that one wind is lower than the
other, the lower wing will have more effective lift than the raised wing
because it is not tilted from the horizontal as much. The imbalance in
lift
tends to raise the lower wing and restore level flight."


Dallas

Dallas wrote:
Would anyone care to comment on the accuracy of this illustration of how
wing dihedral works from a 1981 Jeppesen Sanderson book.

http://makeashorterlink.com/?B25A35DCC

The accompanying statement reads:
"When an aircraft with dihedral rolls so that one wind is lower than the
other, the lower wing will have more effective lift than the raised wing
because it is not tilted from the horizontal as much. The imbalance in lift
tends to raise the lower wing and restore level flight."


Dallas


This is not quite correct, and most of the "pilot books" have it wrong
too. Here is a very nice explanation taken from the book titled
"Mechanics of Flight" by A.C. Kermode of the RAF.

"The most common method of obtaining lateral stability is by the use of
a dihedral angle on the main planes. Dihendral angle is taken as being
the angle betwen each plane and the horizontal, not the total angle
between the two planes, which is really the geometrical meaning of
dihedral angle. If the planes are inclined upwards towards the wing
tips, the dihedral is positive; if downwards, it is negative and called
anhedral; the latter arrangement is used in practice for reasons of
dynamic stability.

The effect of the dihedral angle in securing lateral stability is
sometimes dismissed by saying that if one wing tip drops the horizontal
equivalent on that wing is increased and therefore the lift is
increased, whereas the horizontal equivalent and the lift of the wing
which rises is decreased, therefore obviously the forces will tend to
right the airplane.

Unfortunately, it is not all quite so obvious as that.

Once the aircraft has stopped rolling, provided it is still travelling
straight ahead, the aerodynamic forces will be influenced only by the
airstream passing over the aircraft. This will be identical for both
wings and so no restoring moment will result.

What, then, is the real explanation as to why a dihedral angle is an
aid to lateral stability? When the wings are both equally inclined the
resultant lift on the wings is vertically upwards and will exactly
balance the weight. If, however, one wing becomes lower than the other,
then the resultant lift on the wings will be slightly inclined in the
direction of the lower wing, while the weight will remain vertical.
Therefore the two forces will not balance each other and there will be
a small resultant force acting in a sideways and downwards direction.
This force is temporarily unbalanced and therefore the aeroplane will
move in the direction of this force - i.e. it will sideslip - and this
will cause a fow of air in the opposite direction to the slip. This ahs
the effect of increasing the angle of attach of the lower plane and
increasing that of the upper plane. The lower plane will therefore
produce more lift and a restoring moment will result. Also the wing tip
of the lower plane will become, as it were, the leading edge so far as
the slip is concerned; and just as the center of pressure across the
chord is nearer the leading edge, so the center of the pressure
distribution along the span will now be on the lower plane; for both
these reasons the lower plane will receive more lift, and after a
slight slip sideways the aeroplane will roll back into its proper
position. As a matter of fact, owing to the protetcion of the fuselage,
it is probably that the flow of air created by the sideslip will not
reach a large portion fo the raised wing at all; this depends very much
on the position of the wing relative to the fuselage.

Both the leading edge effect on the lower wing, and the shielding of
the upper wing by the fuselage, occur on nearly all type of aircraft,
and may well mean that an aeroplane has a sufficient degree of lateral
stability without any dihedral angle, or too much if some of the
follwing effects also apply. Even if there is no actual dihedral angle
on the wings, these other methods of achieveing lateral stability may
be described as having a dihedral effect."