Negative wing incidence in biplane
Lee
30 size Waco to put a P.A.W. .29 size diesel so I could play around
with a diesel engine. The Waco was an ARF. After completing the model
I checked the incidence of both wings. The horizontal stabilizer was
leveled in both axis. Both top and bottom wings have a minus 1.5 to 2
degrees of incidence. I wrote the company, The Hobby People. Here
are the emails that were sent and received.
>I built the biplane per instructions, both wings have a minus 1.5 to
2
>degrees of incidence, with tail and motor level. The only way to fix
this
>is to make major modfications to the model. I am very unhappy with
this
>product! What can be done?
>
>Thanks
>Lee
>
Dear Mr. Clements:
As promised, I asked our product manager about the incidence of the
wings.
He replied that you have the correct incidence because it is built in
to
compensate for lift/pitch changes created by the wing through the
speed
envelope. The wing is semi-symmetrical, not full symmetrical so it
trims
differently when compared to planes like the Ultimate.
I would suggest flying it as is and see how it performs.
Customer Service
The product manager's reply might have some validity but I have never
heard of building in negative incidence. The Waco is marginally tail
heavy so I do not want to fly it until I have more information about
negative wing incidence. Any thoughts you might have about this
matter would be greatly appreciated.
Thanks
Lee
l...@dbtech.net
Edwin Smith
would be to examine where the stab would be while flying. If you take your
model shift the angle such that the wings are 0 deg. then you would have a
positive incedence on the stab. I know there are several planes that do
this by design. The goldberg sukoi is one. The full scale B-24 is another.
Its hard for me to see the reasoning in this because I have the sukoi kit
still to be built and have tons of past msgs about stab incedence.
Something about the plane tucking one way or another while knife edge.
Other opinions?
Edwin
"Lee" <l...@dbtech.net> wrote in message
news:7405d777.02022...@posting.google.com...
Don Hatten
Don
"Lee" <l...@dbtech.net> wrote in message
news:7405d777.02022...@posting.google.com...
> I have a question about wing incidence. About a month ago I ordered a
> 30 size Waco to put a P.A.W. .29 size diesel so I could play around
> with a diesel engine. The Waco was an ARF. After completing the model
> I checked the incidence of both wings. The horizontal stabilizer was
> leveled in both axis. Both top and bottom wings have a minus 1.5 to 2
> degrees of incidence. I wrote the company, The Hobby People. Here
> are the emails that were sent and received.
<snip>
PRECEPTER
monowing planes. Go ahead and fly it. It should slow down nicely
eddie
Paul McIntosh
line? Incidences are usually measured against a set datum line. When I
design, I use the main wing incidence and set everything else from that. A
small positive stab incidence relative to the wings is a good way to limit
or control pitch changes due to speed changes. Another way is to add down
thrust.
Go fly it and see if you need any excessive up trim to make it fly level at
1/2 throttle.
--
Paul McIntosh
Desert Sky Model Aviation
ARFs, engines, bearings, etc
http://fly.mcintoshcentral.com
"Lee" <l...@dbtech.net> wrote in message
news:7405d777.02022...@posting.google.com...
CDT6426
>From: l...@dbtech.net (Lee)
>Date: 02/28/2002 11:41 AM Pacific Standard Time
>Message-id: <7405d777.02022...@posting.google.com>
>
>I have a question about wing incidence. About a month ago I ordered a
>30 size Waco to put a P.A.W. .29 size diesel so I could play around
>with a diesel engine. The Waco was an ARF. After completing the model
>I checked the incidence of both wings. The horizontal stabilizer was
>leveled in both axis. Both top and bottom wings have a minus 1.5 to 2
>degrees of incidence. I wrote the company, The Hobby People. Here
>are the emails that were sent and received.
>
>>I built the biplane per instructions, both wings have a minus 1.5 to
>2
>>degrees of incidence, with tail and motor level. The only way to fix
>this
>>is to make major modfications to the model. I am very unhappy with
>this
>>product! What can be done?
Let's turn your results around, and you will see that the wings are at zero and
it is the stab which is set at a positive incidence. This, as the manufacturer
stated, is to lift the tail of the plane and negate some of the lift from the
wings to aid in trimming the plane for level flight throughout the airspeed
range.
You also did not state (in your original post) whether you checked the
incidence of the engine thrust line or firewall in relationship to the wings
and stab. You may find a bit of down-thrust also, or it may be the same as the
wings.
Either way, you should not have a problem with the Waco flying well for you.
When building biplanes, I always meaure the bottom wing first, then the stab,
then the top wing and firewall.
Good luck with your Waco, and
Happy Landings!!
Rich (AKA: Captain Dumb Thumbs)
Richard Kletnieks
Normally its the top wing that has a negative incidence, but I am not
familiar with that particular plane so I can't say if its correct or not. I
would go ahead and fly it as is, you probably won't have any problems. If
the plane needs lots of trim at high speed compared to normal flight speeds
then contact Hobby People and tell them, at least then you will have some
proof that there is something wrong with the plane.
"Lee" <l...@dbtech.net> wrote in message
news:7405d777.02022...@posting.google.com...
David Larkin
wings are at negative. The deisgner may have said that the wings are
positive and the tail even more positive. It's not unuual in biplanes,
for example the Fokker D VII. The tail is sited in the downwash from the
wings.
Doucoursey
positve in the stab, with 1/2 degree positive incidence on the motor. the
goldberg bipe also calls for 0 incedence on the wings and 1 degree positive on
the stab. i think the 1/2 degree on the motor is to help it hover better.
DOUG
Mathew Kirsch
> I have a question about wing incidence. About a month ago I ordered a
> 30 size Waco to put a P.A.W. .29 size diesel so I could play around
> with a diesel engine. The Waco was an ARF. After completing the model
> I checked the incidence of both wings. The horizontal stabilizer was
> leveled in both axis. Both top and bottom wings have a minus 1.5 to 2
> degrees of incidence. I wrote the company, The Hobby People. Here
> are the emails that were sent and received.
Actually, you need to level the thrust line of the airplane to check
for incidence. All you have done is measure the RELATIVE incidence
between the stab and the wings.
According to Dave Patrick, many planes, especially bipes, are designed
with some positive incidence in the horizontal stab because it's
catching the downward slipstream from the wings, and is actually
flying with negative incidence in the slipstream.
If you level the plane on the actual thrust line, you'll probably find
out that the bottom wing is at 0, the top wing is at -.5, and the tail
is at +2.
Hans Meij
http://home.hetnet.nl/~meijhmb/projects/images/pitts/pittsstabangle.gif
Website of the manufacturer
Greetings,
Hans Meij
http://home.hetnet.nl/~meijhmb
PigeonHoleProd
A Clark Y airfoil, normally considered a "flat bottomed" section, will
generate lift to negative 8 degs. this can be appreciated if a chord line is
drawn thru the center of the TE and the leading edge and rotated to level. it
can now be seen to approximate a semi-symetrical section. Several Curtiss
biplanes of the '30's, such as P-1 thru P-6E, and Falcon used the Clark Y in
negative incidence set up. BTW, you didn't say what Waco your arf is but most
Waco's, from 1930 on also had Clark Y, but usually at O deg relative incidence.
One last item, all of the above real a/c have adustable tail incidence (trim),
usual range is neg 2-3 deg. to 3-4 deg . positive. I believe our models will
tolerate a much wider incidence range than is commonly belived, but you may
want to keep a more scale (read slightly more fwd) CG than the typical 33% of
mean chord. the farther aft, within reason of course, your cg is, the more
positive incidence at the stab can be used.
I believe you shoud be alright with the way your model is set up.
Phil
emc...@yahoo.com
adjusted the wings to a negative incidence in relation to the tail.
Fly it. If it flies fine, don't worry about it.
Malcolm L
David Larkin <dsla...@blvl.igs.net> wrote in message
news:3C7ED484...@blvl.igs.net...
> It is a matter of semantics. You say that the stab is at zero and the
> wings are at negative.
>
>
> > I have a question about wing incidence.
Semantics aside, a friend once asked me (a long, long time ago) this same
question about another model. He built it according to the kit instructions
and plan. It came out with the top wing with "negative incidence" - much as
you did. It looked very odd. We decided to contact the kit maufacturer who
confirmed in a rather wooly response that they had sold thousands of this
kit without a problem. As I knew the designer of the model, I was able to
contact him. His response was terse, "Build it according to my plan and it
will fly fine." We did - and it did ! MalcolmL
Pe Reivers
first, the tail is positioned in the downwash of both wings, and should have
positive incidence to be neutral. Because there is one high, and one low
wing, shifting the stab up or down in a design does not help much in
correcting yaw coupling.
Second, the top wing prevents the bottom wing from stalling, so the bottom
wing may have a slightly larger incidence than the top wing.
In flight, this result in a larger angle of attack for the lower wing, as
compared to the top wing, and the stab will be neutral
--
Pé, from Arcen, south-east Netherlands
www.mvvs-nl.com/index.html
to reply : prei...@mvvs-nl.com
"David Larkin" <dsla...@blvl.igs.net> schreef in bericht
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Malcolm L
nearly hit you in the back, I had a similar experience with a WWI bipe from
a wellknown kit maker made by a friend who is an experienced builder. He
asked me to do the honours at the field. After doing the pre-checks, we
went for it. Immediately it started climbing steeply and was soon almost
looping over my head. Throttling back, I found it could be flown (just
!!!) with full down trim AND full down stick. Luckily I was able to land
without any damage. After taking out about 5 or 6 degrees of wing
incidence, the model flew fine after that. MalcolmL
<emc...@yahoo.com> wrote in message news:3c7fb0fd...@news.twave.net...
PigeonHoleProd
>incidence, the model flew fine after that.
What no pre-flight eyeball BEFORE its first flight???
Phil
Ed Cregger
"scale" that he/she used the original airfoil and
incidences? This is precisely what will happen if you use
the incidences of some real airplanes in a model. The scale
builders just can't accept that things behave differently in
a much smaller size.
Ed Cregger
ecre...@hotmail.com
"PigeonHoleProd" <pigeonh...@aol.com> wrote in message
news:20020303114008...@mb-fe.aol.com...
Charlie Dilks
Cregger at ecre...@hotmail.com wrote on 3/3/02 2:33 PM:
> Have you ever met a scale enthusiast that was so into
> "scale" that he/she used the original airfoil and
> incidences? This is precisely what will happen if you use
> the incidences of some real airplanes in a model. The scale
> builders just can't accept that things behave differently in
> a much smaller size.
Tell me all about it. ;) I crashed a Stearman on it's first flight and
totalled it on it's second because I didn't believe the negative incidence
of the top wing in the supplied jigs and put in positive because that's how
the real one was.
http://charlie_dilks.tripod.com/eplanes/id11.html
--
Charlie Dilks Newark, DE USA
pcoopy
I build mostly all bipes. Some kits, some scratch. It is my
experience that generally in addition to a little positive stab, that
some negative on the top wing relative to the bottom wing will help
the bottom wing stall first (higher angle of attack) and cause the
plane to "hang" on tne top wing which will make any bipe much stable
on landing. It also helps prevent premature lift off before rotation.
Phil AMA609
PigeonHoleProd
>> > "scale" that he/she used the original airfoil and
>> > incidences? This is precisely what will happen if you use
>> > the incidences of some real
>airplanes in a model. The scale
>> > builders just can't accept that things behave differently in
>> > a much smaller size.
>> Tell me all about it. ;) I crashed a Stearman on it's first flight and
>> totalled it on it's second because I didn't believe the negative incidence
>> of the top wing in the supplied jigs and put in positive because that's how
>> the real one was
While I agree with Phil AMA609's comment about bipe rigging, I've never heard
such claptrap (above) in all my modeling and flying life.
A scale model with scale airfoils, incidences, thrust, CG and comparable power
and weight loading WILL fly very much like the real thing (evenif not at scale
speed). If it worked in full scale it can be made to work in models. that
some people can't get them to work is a much more likely scenario. If models
didn't behave as their full scale counterparts, there would have been no need
for wind tunnel research 1900 to present day(mostly done with models).
what the stearman modeler should note, and I've seen it in several PT-17
models, is that they fly crappy, hey...JUST like the real airplane. they won't
manuver because they are too stable (that's why some have a full span stall
strip upper wing LE). I would bet you your model crashed for some other reason
than mere scale incidences. It's a poor workman that blames his tools.
Phil
The Natural Philosopher
PigeonHoleProd wrote:
>
> A scale model with scale airfoils, incidences, thrust, CG and comparable power
> and weight loading WILL fly very much like the real thing (evenif not at scale
> speed). If it worked in full scale it can be made to work in models. that
> some people can't get them to work is a much more likely scenario. If models
> didn't behave as their full scale counterparts, there would have been no need
> for wind tunnel research 1900 to present day(mostly done with models).
Wind tunnels have to try and match the reynolds numbers, and even so,
its not a perfect art.
Not particularly saying anythiung about the rigging ogf bipes, BUT its a
known fact that models flying at different reynolds numbers will not
behave like the full size.
Even flying at the same ones, I would guess that factors like wing
stiffness etc would also drastically affect performance, especially with
thin 'undercambered' wings.
Plus the fact that we don't know if the riggers on WWI biplanes
'tweaked' the turnbuckles to get the planes to fly better: Aerodynamics
at that period were a black art...
Charlie Dilks
pigeonh...@aol.com wrote on 3/4/02 1:19 AM:
> I've never heard such claptrap (above) in all my modeling and flying life.
Great way to get your point across. I'm sure people hang on your every word.
:}
> I would bet you your model crashed for some other reason than mere scale
> incidences. It's a poor workman that blames his tools.
If you had actually read the part of my page that I referenced you would
have seen what I attributed the crash to.
From the page:
"The problem was that it kept ballooning up. I had to keep the stick well to
the front. This wasn't a familiar position for my thumb and it eventually
got the best of me."
PigeonHoleProd
I am sorry if I offended you personally. that was not my intent.
We've all been the victim of "dumb thumbs", new model preflight jitters,
impatience, and "No guts no glory" syndrome, etc. ALL of which usually result
in a disasterous, less than hoped for results. succesfull model flying, just as
in successful full scale flying depends on paying attention to ALL of the
little details. If we don't pay strict attention we get slapped soundly (I am
sure we can appreciate that a modeler's learning curve is so much for forgiving
!).
From what I gathered from earlier posts was that the model flyer (you?) said
his Biplane model crashed because of too much positive incidence. Couldn't this
condition have been spotted before the flight attempt? Shouldn't it have been?
If the incidence was scale (which seemed to me to be the inane target of the
other post), could it be that the CG was not located properly, or the
thrustline, the decalage improper, improper wash out, or the...???
i build and fly models (rubber scale, cl, ff, RC) as well as full size(antiques
and a few homebuilts). I see a direct connection between the models and the
real thing, CONSTANTLY, even if "air molecules don't scale down". My
experience is if the real set up is stable, the model will be. if the real
aircraft exhibits viscious stall charactoristics, the model will too. however,
with a little commen sense, experience, and application of universal, yet
relatively simple, aerodynamic priciple, the model can be successfully flown in
a scale like manner.
The problem , as I see it is that too many modelr's assume a certain real a/c
CAN'Tpossibly be modeled because of long standing ill conceived perceptions,
predudicing their views and poisoning the pool of collective modeling thought.
Really don't care if modelers hang on my every word. in forty plus years of
aviating both big and little, I've noted there are those that say can't and
those that say can. the former seem to talk loudest (yell?) and the crowd
seldom listens to the latter.
Phil
Ed Cregger
things do not scale up or down equally well. Models are poor
predictors of full scale performance.
Claptrap indeed! <G>
Ed Cregger
ecre...@hotmail.com
"PigeonHoleProd" <pigeonh...@aol.com> wrote in message
news:20020304011949...@mb-fw.aol.com...
jsk
PigeonHoleProd
>Ed Cregger wrote:
>One of the first things that an engineer learns is that
>things do not scale up or down equally well. Models are poor
>predictors of full scale performance.
Do engineers ever learn to listen?
No one is denying that models DO perform differently than their full scale
counterparts. That, in this disscusion, has NEVER been the issue. what is at
issue is; can scale airfoils, incidences, thrustlines, work in a successfull
model of its prototype? by and large, the answer is a RESOUNDING YES. Its done
all the time!
Phil
Paul McIntosh
well as model racing airfoils. Full scale airfoils are much thinner in
section and will stall at a much lower AOA. Also, most of the benefits of
laminar flow airfoils is lost on scale sizes because we usually don't
approach the laminar separation airspeeds.
--
Paul McIntosh
Desert Sky Model Aviation
ARFs, engines, bearings, etc
http://fly.mcintoshcentral.com
"PigeonHoleProd" <pigeonh...@aol.com> wrote in message
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High Commander
"you can always tell an Engineer..... but not much!!"
"PigeonHoleProd" <pigeonh...@aol.com> wrote in message
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______________________________________________________________________________
Posted Via Binaries.net = SPEED+RETENTION+COMPLETION = http://www.binaries.net
The Natural Philosopher
And in *some* cases, my guess is that if they are *all* scale, the
answer is a resounding *THUMP*.
You can get away with having *some* things to scale, if others aren't.
Like C of G for example. Likewise a wing designed to do mach 3+ and a C
of G that would make the full size plane unflyable without a
computer...is going to be an interesting proposition tootling around at
under 100mph....
From what I have read, and what little I know of aerodynamics, the sorts
of models that should be able to be scaled easily are those in the
period 1930-1960. Before that aerodymanics was a black art, and lots of
planes had vicious habits. After that, speeds got so high that the
factors necessary to enable the aircraft to cope with transonic
supersonic and hypersonic speeds mean that the reynolds numbers are so
different, and the effects of the sound barrier so different at scale
speeds, that its going to be a bit of a gamble.
The Thunderbolt reputedly could be put into a dive where the airflow
over the tailplane approached supersonic, at which point the controls
reversed. Tales of pilots going over 90 dgreees into inverted dives,
never to be seen again, are not uncommon...
I think its a great idea to *try* and copy everything exactly, but I
also think one should be prepared to tweak some things - washout, C of
G, and in extreme cases wing sections, and tail feather areas, in order
to get a flyable aircraft.
It begs the question of what a 'scale model' really is supposed to be,
doesn't it?
Out with the lathes, chaps, and star carving out magnetos for that 1/4
scale 'Le Rhone' :-)
And will it run on 'scale petrol' or what?
> Phil
The Natural Philosopher
High Commander wrote:
>
> You know what they say about Engineers....
>
> "you can always tell an Engineer..... but not much!!"
An engineer is someone who can do, for sixpence, what any damned fool
can do for a quid..
Neville Shute Norway..:-)
DC3Gooney
I have a scratch-built laminar-flow wing for my
GP P-51, just like the full-scale, with the max
camber at approx 55% of chord. Some guy at
the field built it, but was scared to fly it. Now
that I know it scales down fine, I'll try it on my fuse.
Thanx
DC3
---------------
Pe Reivers
Example: The 6-series NACA, like the 63-012 shows a pronounced tendency to
burble and stall without warning at higher Ca levels (Ca=> 0.4) These high
values are required to pull out of a dive, and while landing. Both are
situations where you do not want a stalled wing. Even below Ca 0.4 the foils
do not perform better than the much used NACA 2412.
Unless built extremely accurate, for model airplane use I would stay well
clear of the laminars, especially in fighters with their inherent higher
wing loads.
--
Pé, from Arcen, south-east Netherlands
www.mvvs-nl.com/index.html
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"DC3Gooney" <dc3g...@aol.comnomail> schreef in bericht
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Robert McCoy
to know is what happened to Lee's Waco when he flew it????