Biplane rigging question
Dick Ripper
statement which I don't understand and wonder if someone could explain it to
me:
"Most people don't know how to rig a biplane (I don't)
and this one is rigged a bit differently than most.
He designed the thing so that in LEVEL flight, you'd
be flying on the top wing ONLY, so as to give a
heavier wing loading".
I understand "heavier wing loading" but am at a loss on how the plane flies
only on one or the top wing due to rigging. I assume "rigging" is the
tension/compression loading of the flying wires and struts??
Thanks , Dick
Rick McShane
far more then just wire tension. With the rigging you set both the dihedral of
the wings (may be different for upper and lower) and you set the wash in wash
out of the tips. In some cases the rigging can affect minor amounts of sweep
back in the wings.
If you need more details I can dig up the large collection of information that
is used on the Pitts/Eagle series of biplanes
tscottme
lift in level or cruise flight. I'd suspect the angle of incidence is
lower for the bottom wing. It would be interesting to know if this sort
of setup complies with the aircraft's Type Certificate.
HLAviation
>and this one is rigged a bit differently than most.
>He designed the thing so that in LEVEL flight, you'd
>be flying on the top wing ONLY, so as to give a
>heavier wing loading".
>I understand "heavier wing loading" but am at a loss on how the plane flies
>only on one or the top wing due to rigging. I assume "rigging" is the
>tension/compression loading of the flying wires and struts??
Thats only part of it, and the reason you take these actions is the true
meaning of rigging. The alignment of the surfaces to one another and the
fuselage is the meaning of rigging. One wings angle of incidence can be set to
produce lift while the other ones doesn't. "Rigging" applies to every surface
on the aircraft. Ever fly a "Crooked" airplane, one wher you have to apply
opposite rudder to the aelioron to fly straight and the ball is still a little
out, but if you center the ball you're in a turn? Thats out of rig as well as
planes that fly as if you're balancing them on a marble. It used to be
difficult to get a plane in perfect rig because you need a perfectly flat datum
plane to measure off. Now it's easy, you go down to the construction rental
place and rent a laser transit setup and adjust the plane to level with the
tire pressures and then measure at the datum points dictated in the rigging
section of the service manual. Most older planes gain several knots after
getting the rig checked and aligned, not to mention they fly nicer.
Charles K. Scott
"Dick Ripper" <RWRi...@prodigy.net> writes:
I can only guess Dick, but the only way to make a wing not fly is to
point the nose down, in other words, have a negative angle of
incidence. Don't know why one would want this.
Most all biplanes assume the proper rigging attributes simply by
bolting the wings, cabine struts and wing struts together along with
the right flying and landing wires.
The angles of incidence and the dihedral are usually a function of the
lengths of the cabine struts and the brackets bolted to the fuselage.
You can modify things like washout by cranking the wing struts for
adjustment but in general, if the upper wing is supposed to be straight
with the dihedral coming from the lower wings, you don't have a lot of
choice here.
So I guess I'm saying that by the time you bolt the wings on, using the
designed cabine struts, wing struts and flying wires, there might not
be a whole lot of adjustment left except to try to adjust washout for a
heavy wing.
No idea why anyone would want to make one of the wings of a biplane
quit flying when in cruise unless it's a method of reducing drag. If
this is successfull, why don't all biplanes get rigged that way?
Corky (I'm not an aerodynamics expert, the above is simply my
comprehension) Scott
Mark S. Jennings
> lift in level or cruise flight. I'd suspect the angle of incidence is
> lower for the bottom wing. It would be interesting to know if this sort
> of setup complies with the aircraft's Type Certificate.
The whole story sounds inplausible. If each wing in a biplane normally
contributes equal lift and if the lower wing is adjusted to provide zero
lift, then the upper wing would have to provide double the normal lift.
This would equivalent to doubling the weight of the plane or constantly
pulling a 2G turn. If the biplane has enough power to pull a constant 2G
turn, then perhaps it would fly, but just barely.
And I doubt you could adjust a biplane this way if you tried since it would
require a large negative angle of incidence in the lower wing.
- Mark
Ed Sullivan
Some biplanes such as the Bücker Jungmeister do have the wings rigged
at different angles of incidence, in fact I think the top wing on the
Bücker is rigged with a slight negative angle. I am not sure of the
reasoning, however it may have to do with inverted performance.
Ed Sullivan
Bill Nelson
I do know that some biplanes had a highter anlge of incidence on the bottom
wing than the top wing. The thought was that at the stall, the bottom wing
would stall first, leaving you with a parasol airplane. Hence the airplane
would be reluctant to drop a wing during the stall. Remember, most biplane
were conventional gear, and you tried to always execute a full-stall landing.
Dropping a wing in the landing just upped the degree of difficulty. Other than
that I can't account for different AOI.
William R. Nelson ATP, CFI, DPE.
wrn...@aol.com
HECTOP
> I do know that some biplanes had a highter anlge of incidence on the bottom
In any case biplane pilots have the upper hand in those neverending low/high wing
hangar arguments ;)
--
HECTOP
PP-ASEL/BOFH
http://www.maxho.com
maxho_at_maxho.com
Ed
> The whole story sounds inplausible. If each wing in a biplane normally
> contributes equal lift and if the lower wing is adjusted to provide zero
> lift, then the upper wing would have to provide double the normal lift.
> This would equivalent to doubling the weight of the plane or constantly
> pulling a 2G turn. If the biplane has enough power to pull a constant 2G
> turn, then perhaps it would fly, but just barely.
Can't resist this one. You miss a key point in your train of logic. In
level flight, the total lift being produced is 1G. So if each wing were
contributing equal lift, then each wing is producing 1/2G worth of lift.
Eliminating the lift from the bottom wing does double the lift on the top
wing. But, the total lift on the top wing is now 1G. There is no doubling
of weight, just a reduction of lift.
Ed
bottom[?]) wing stalls first, while the other wing is still flying. I
recall that this had to do with improving stall recovery characteristics,
and that a plane rigged the other way around might not be able to recover
from stalls (bottom wing blocking airflow to the top wing?).
As for how you would make it do so, you would mount the wings so the top and
bottom chord lines were not parallel. The top and bottom wings would then
produce different amounts of lift, since the AoA for each wing would be
different for a given relative wind. If you set it up so that the bottom
wing had an AoA of zero at cruise speed while the top wing had an AoA
sufficient to generate 1G of lift, there you go.
As for whether this is practical, desirable, or even mechanically feasible,
that is beyond my level of knowledge and my willingness to speculate.
--
---
"Dick Ripper" <RWRi...@prodigy.net> wrote in message
news:95kfoo$9dfa$1...@newssvr06-en0.news.prodigy.com...
Mark S. Jennings
> level flight, the total lift being produced is 1G. So if each wing were
> contributing equal lift, then each wing is producing 1/2G worth of lift.
> Eliminating the lift from the bottom wing does double the lift on the top
> wing. But, the total lift on the top wing is now 1G. There is no
doubling
> of weight, just a reduction of lift.
Where is Peter Garrison when we need him?
Yes, it all depends on where you start from. I was viewing the problem from
the top wing's POV and from this POV, it would have to produce twice as much
lift as it was when the bottom wing was contributing half. So from the
wing's POV, it is like pulling a 2G turn. Or, IOW, if the bottom wing of a
biplane were to suddenly fall off and the pilot were to adjust the AOA to
maintain level flight, the top wing would "feel" just like it would feel in
a 2G level turn.
Now, on to that question of in a downwind turns.
- Mark
stuart
for what I feel is a safety element. In a dive, just at VNe (about 252 kts)
you absolutely cannot maintain nose down attitude. Even with a 200 lb guy
pushing on the yoke, it will push back at you into an up elevator position
and the aircraft's nose comes up. Any explanations?
"Mark S. Jennings" <mark...@NOSPAMhalcyon.com> wrote in message
news:95loik$ceb$1...@brokaw.wa.com...
Charles K. Scott
"stuart" <hyde...@home.com> writes:
> One interesting aerodynamic feature built into later Staggerwings allowed
> for what I feel is a safety element. In a dive, just at VNe (about 252 kts)
> you absolutely cannot maintain nose down attitude. Even with a 200 lb guy
> pushing on the yoke, it will push back at you into an up elevator position
> and the aircraft's nose comes up. Any explanations?
Yes, more lift is developed at that speed than the elevators can
counter. Same thing used to happen when B-17's were dived to get to
the deck in a hurry; it took both pilots all their strength to hold the
nose down. Big wing, lots of lift.
Corky Scott
Corky Scott
Jeffrey Lo
"Ed" <hayw...@hotmail.com> wrote in message
news:7%pf6.7750$5H.14...@typhoon2.ba-dsg.net...
> I have read that many biplanes are designed so the top (or is it the
bottom[?]) wing stalls first,
> while the other wing is still flying. I recall that this had to do with
improving stall recovery
> characteristics, and that a plane rigged the other way around might not be
able to recover from stalls
> (bottom wing blocking airflow to the top wing?).
>
> As for how you would make it do so, you would mount the wings so the top
and bottom chord lines
> were not parallel. The top and bottom wings would then produce different
amounts of lift, since the
> AoA for each wing would be different for a given relative wind. If you
set it up so that the bottom
> wing had an AoA of zero at cruise speed while the top wing had an AoA
sufficient to generate 1G of
> lift, there you go.
>
> As for whether this is practical, desirable, or even mechanically
feasible,
> that is beyond my level of knowledge and my willingness to speculate.
Curtis Pitts (designer of the Pitts Specials) holds the patent (long since
expired, I'm sure) on how you do this for an aerobatic biplane. Since the
wings are staggered, you want the forward wing to stall first (uprigth or
inverted) so that the stall produces a pitch down, rather than a pitch up,
aggravating the stall. You could (as has been suggested) put a little more
incidence into the top/forward wing to cause it to reach the critical AOA
before the lower/rear wing, but this gets reversed when you are inverted.
The clever way Curtis did it was to use slightly different airfoils for the
two wings, so that the critical AOA for the top/forward wing was slightly
less than the critical AOA for the lower/rear wing. This way, the wings
could be rigged with the same incidence, yet the top/forward wing would
stall first, either upright or inverted.
Jeff Lo
jlo -at- pacbell -dot- net
1988 Pitts Special S1S N230MP, Reno race #6
Richard Lamb
But my plans show both wings rigged at 0 degrees.
and only one rib pattern...
--
Richard Lamb
email: lam...@flash.net
web: http://www.flash.net/~lamb01
highflyer
That is accomplished by rigging the top wing at a greater incidence
angle than the lower wing. At cruise speed the upper wing still has
a positive angle of attack, but the lower wing is at its zero lift
angle of attack and in not contributing to the overall lift.
That supposedly reduces the drag of the lower wing and minimized the
interplane interference. By effectively increaseing the wing loading
at cruise it makes the airplane ride a bit better in turbulence.
"Rigging" applies to all of the adjustments that control the relative
angles of attack of the various surfaces, along with their twist or
"washout" and "washin."
Rigging a biplane is one of those "sciences" that verges on "art."
--
HighFlyer
Highflight Aviation Services
highflyer
>
> > My guess is that the bottom wing is rigged so as to provide little net
> > lift in level or cruise flight. I'd suspect the angle of incidence is
> > lower for the bottom wing. It would be interesting to know if this sort
> > of setup complies with the aircraft's Type Certificate.
>
> The whole story sounds inplausible. If each wing in a biplane normally
> contributes equal lift and if the lower wing is adjusted to provide zero
> lift, then the upper wing would have to provide double the normal lift.
> This would equivalent to doubling the weight of the plane or constantly
> pulling a 2G turn. If the biplane has enough power to pull a constant 2G
> turn, then perhaps it would fly, but just barely.
>
Very few biplanes are designed so that both wings provide the same lift.
Generally there is a "decalage" or difference in the angle of incidence
between the two wings. If the lower wing has a lower angle of incidence
it will always fly at a lower angle of attack than the upper wing.
This is commonly done to ensure that the upper wing, which is usually
forward of the lower wing, stalls first. This ensures the nose will
drop when the airplane stalls.
> And I doubt you could adjust a biplane this way if you tried since it would
> require a large negative angle of incidence in the lower wing.
>
Most wings are designed so that the angle of attack at cruise is quite
small. If the lower wing is set at, say two or three degrees less
incidence than the upper wing, and the airfoils are the same, when the
upper wing is at the bottom of its drag bucket at cruise, the lower
wing will be pretty close to zero lift.
If you look at biplane plans, you will see that two or three degrees
difference between the upper and lower wing is not at all unusual.
highflyer
In my Stinson Reliant, to get to Vne requires two guys pushing for all
they
are worth on the yokes! Relax at all and it pops up like a cork! :-)
Ealanier
quit flying when in cruise unless it's a method of reducing drag.
The biplane will fly more stable if more lift is generated by the upper wing.
It is like the high wing Cessna design with center of lift above the center of
gravity. If you want to do aerobatics without the plane fighting you, the
center of lift needs to be set closer to center of weight.
macel...@gmail.com
ji...@specsol.spam.sux.com
> On Monday, February 5, 2001 7:59:03 AM UTC+11, Dick Ripper wrote:
>> I'm researching a personal project and have run across the following
>> statement which I don't understand and wonder if someone could explain it to
>> me:
>> "Most people don't know how to rig a biplane (I don't)
>> and this one is rigged a bit differently than most.
>> He designed the thing so that in LEVEL flight, you'd
>> be flying on the top wing ONLY, so as to give a
>> heavier wing loading".
>> I understand "heavier wing loading" but am at a loss on how the plane flies
>> only on one or the top wing due to rigging. I assume "rigging" is the
>> tension/compression loading of the flying wires and struts??
>>
>> Thanks , Dick
> It is fairly common for the built in angle of incidence of the top wings
I am pretty sure in that in the 14 years that have passed since the
question was asked that it was answered.
--
Jim Pennino