Tandem-wing Airplanes

[Phil J]

Here's another question for you engineers out there. Traditional
airplane design has the tail pressing down, so the tail is fighting
the work that the main wing is doing. A tandem-wing airplane in which
both front and rear wings are lifting upward is a more efficient
design, which is one reason Bert Rutan chose the canard configuration
for so many of his designs. But in the canard configuration, the
front wing is smaller than the rear wing. This is what I don't
understand. It seems to me that a design in which the front wing was
larger and the rear wing was smaller would be more stable in pitch.
The smaller rear wing would automatically damp pitch excursions like
the fins of an arrow. So why is the canard the most successful tandem-
wing design flying?

[Bertie the Bunyip[_24_]]

Phil J > wrote in news:e5efb14f-c2c5-41c7-a127-
:

> Here's another question for you engineers out there. Traditional
> airplane design has the tail pressing down, so the tail is fighting
> the work that the main wing is doing. A tandem-wing airplane in which
> both front and rear wings are lifting upward is a more efficient
> design, which is one reason Bert Rutan chose the canard configuration
> for so many of his designs. But in the canard configuration, the
> front wing is smaller than the rear wing. This is what I don't
> understand. It seems to me that a design in which the front wing was
> larger and the rear wing was smaller would be more stable in pitch.
> The smaller rear wing would automatically damp pitch excursions like
> the fins of an arrow. So why is the canard the most successful
tandem-
> wing design flying?
>

Well, it isn't a tandem wing, for one thing. It's a canard. It's front
"wing" is called a canard and not a wing. You could say it's a tomato
tomato thing, but that's the definition. A Bleriot could also be called
a tandem wing aircraft if you used the same standard. It's tail lifts.
So do most free flight models. These airplanes have very large stabs (or
wings, if you prefer), and very far aft CGs as compared to a a
"conventional" aircraft and usually very long fuselages.
Aircraft like the Bleriot were not very stable in pitch, and RC
conversions of old time free flight airplanes with the original FF CG
are very twitchy in pitch if elevator is used.

The basic principle is that more of the horizontal surface ( multiplied
by it's arm) has to be behind the CG to get the thing going in the
direction you want it to. Think horizontal weather vane.
That's pretty simplistic, but basically it's the way it works. The
horizontal weather vane principle also explains why conventional
aircraft get nasty when their CG is moved aft. Never mind any rubbish
Jepeson might tell you about the elevators making lift the wrong way.
..
I'm not exactly sure what the definition of a tandem wing is, percentage
wise, but basically if it looks like one then it is one. That is, the
wings should be in the neighborhood of each other area wise.
The Flying Flea would be a good example.

Bertie

[Phil J]

On Feb 2, 1:59*pm, Bertie the Bunyip > wrote:
>
> Well, it isn't a tandem wing, for one thing. It's a canard. It's front
> "wing" is called a canard and not a wing. You could say it's a tomato
> tomato thing, but that's the definition. A Bleriot could also be called
> a tandem wing aircraft if you used the same standard. It's tail lifts.
> So do most free flight models. These airplanes have very large stabs (or
> wings, if you prefer), and very far aft CGs as compared to a a
> "conventional" aircraft and usually very long fuselages.
> Aircraft like the Bleriot were not very stable in pitch, and RC
> conversions of old time free flight airplanes with the original FF CG
> are very twitchy in pitch if elevator is used.
>
> *The basic principle is that more of the horizontal surface ( multiplied
> by it's arm) has to be behind the CG to get the thing going in the
> direction you want it to. Think horizontal weather vane.
> That's pretty simplistic, but basically it's the way it works. The
> horizontal weather vane principle also explains why conventional
> aircraft get nasty when their CG is moved aft. Never mind any rubbish
> Jepeson might tell you about the elevators making lift the wrong way.
> .
> I'm not exactly sure what the definition of a tandem wing is, percentage
> wise, but basically if it looks like one then it is one. That is, the
> wings should be in the neighborhood of each other area wise.
> The Flying Flea would be a good example.
>
> Bertie

OK. But why on the canards flying these days is the little wing in
front of the CG, and the big wing behind it. It seems like it would
be more stable in pitch if the little wing was behind the CG. Putting
the little wing in front of the CG seems like it would make the
airplane inherently unstable in pitch. Looking at Rutan's designs, it
looks like he countered this by using a swept main wing. But that
would have been unnecessary if he had put the smaller wing in back.
The only reason I can think of to put the smaller wing out front would
be for pilot visibility, so maybe that's the explanation?

Phil

[Bertie the Bunyip[_25_]]

Phil J > wrote in news:75220ca0-969d-4a58-8dac-
:


>
> OK. But why on the canards flying these days is the little wing in
> front of the CG, and the big wing behind it. It seems like it would
> be more stable in pitch if the little wing was behind the CG.


Then it wouldn't be a canard.


Putting
> the little wing in front of the CG seems like it would make the
> airplane inherently unstable in pitch. Looking at Rutan's designs, it
> looks like he countered this by using a swept main wing. But that
> would have been unnecessary if he had put the smaller wing in back.
> The only reason I can think of to put the smaller wing out front would
> be for pilot visibility, so maybe that's the explanation?


No, it's because he wanted a canard. I explained above that having a
lifitng stab, even a great big one, makes for a twitchy airplane. I'm
sure that could be managed if you wanted, but it's not ever going to be
a very happy airplane. The smaller "wing",on a canard is called a
canard. It's primarily a stabilsation surface that also contributes to
overall lift. It is not a wing
There are probably several reasons that Rutan elected to sweep the wing.
One, it gives good stability without sacrificing manueverability. two,
it expands the CG limits and in the case of this aricraft, allows a
shorter fuselage than would be the case if the weren't swept. .
So, tu summarise, if you put the "smaller wing" (sic) in the back, it';s
a tail unless it;s lifting. If it's lifting it needs to be fairly large
to be useful. make it large enough and you have problems with handling,
one solutuion for this problem is to reduce the sizre of the forward
wing and move the CG aft. Voila! you have a canard!


Bertie

[[email protected]]

On Feb 2, 2:21 pm, Bertie the Bunyip > wrote:
> So, tu summarise, if you put the "smaller wing" (sic) in the back, it';s
> a tail unless it;s lifting. If it's lifting it needs to be fairly large
> to be useful. make it large enough and you have problems with handling,
> one solutuion for this problem is to reduce the sizre of the forward
> wing and move the CG aft. Voila! you have a canard!
>
> Bertie

Seems to me that lifting tails are, and have been, illegal for
long time. The regs call for the aircraft to automatically settle into
a glide if the power should fail, to prevent stalling. A lifting tail
just won't do this. As the airplane slows it will drop, raising the
nose, and the airplane will stall, and almost certainly enter an
unrecoverable spin. If the pilot does manage to establish a glide, the
nose will drop further as glide speed increases, opposite to what we
know in our airplanes, and totally unstable. Some early airplanes were
built this way, and after they'd killed enough pilots the designers
decided to make things differently.
See FAR 23 (U.S.) or CAR 523 (Canadian) for the details.

Dan

[Bertie the Bunyip[_25_]]

wrote in news:ac796136-f9af-4608-a9ad-
:

> On Feb 2, 2:21 pm, Bertie the Bunyip > wrote:
>> So, tu summarise, if you put the "smaller wing" (sic) in the back,
it';s
>> a tail unless it;s lifting. If it's lifting it needs to be fairly
large
>> to be useful. make it large enough and you have problems with
handling,
>> one solutuion for this problem is to reduce the sizre of the forward
>> wing and move the CG aft. Voila! you have a canard!
>>
>> Bertie
>
> Seems to me that lifting tails are, and have been, illegal for
> long time.


Well, i wouldn't have thought so.

The regs call for the aircraft to automatically settle into
> a glide if the power should fail, to prevent stalling. A lifting tail
> just won't do this. As the airplane slows it will drop, raising the
> nose, and the airplane will stall, and almost certainly enter an
> unrecoverable spin. If the pilot does manage to establish a glide, the
> nose will drop further as glide speed increases, opposite to what we
> know in our airplanes, and totally unstable. Some early airplanes were
> built this way, and after they'd killed enough pilots the designers
> decided to make things differently.
> See FAR 23 (U.S.) or CAR 523 (Canadian) for the details.


Wel, yeah, if you just put one one on a 172 and move the CG back you're
going to have problems. , but lots of free flight airplanes use this
system with no problems. They do get very twitchy n pitch if you put a
radio elevator on them though.
this is a typicl old time FF airplane with a lifting stab.

http://www.rcgroups.com/forums/attachment.php?attachmentid=1670799

These don't spin even with elevator and rudder (wel, not easily) and as
you can see are arranged very different from a modern lightplane. They
are also extremley sensitive to CG variations which would make this
arrangemetn undesirable on full size aircraft.


Bertie

[Kyle Boatright]

"Phil J" > wrote in message
...


>OK. But why on the canards flying these days is the little wing in
>front of the CG, and the big wing behind it. It seems like it would
>be more stable in pitch if the little wing was behind the CG. Putting
>the little wing in front of the CG seems like it would make the
>airplane inherently unstable in pitch. Looking at Rutan's designs, it
>looks like he countered this by using a swept main wing. But that
>would have been unnecessary if he had put the smaller wing in back.
>The only reason I can think of to put the smaller wing out front would
>be for pilot visibility, so maybe that's the explanation?

>Phil

The pitch and yaw stability of an aircraft have to do with the relationship
of the center of gravity and the center of pressure. The farther ahead of
the CP the CG is, the more stable an aircraft will be.

The swept wing on rutan designs serves 2 purposes. First, it moves the
center of lift (and center of pressure) aft in order to accomodate the aft
CG caused by the rear mounted engine. Second, sweeping the wing places the
vertical surfaces farther aft, giving them more authority.

KB

[Barry]

> Seems to me that lifting tails are, and have been, illegal for
> long time. The regs call for the aircraft to automatically settle into
> a glide if the power should fail, to prevent stalling. A lifting tail
> just won't do this. As the airplane slows it will drop, raising the
> nose, and the airplane will stall, and almost certainly enter an
> unrecoverable spin. If the pilot does manage to establish a glide, the
> nose will drop further as glide speed increases, opposite to what we
> know in our airplanes, and totally unstable.

A good reference for this subject is "See How it Flies". It's not true that a
tail with positive lift will necessarily lead to instability:

"The biggest contribution to angle of attack stability is decalage. The thing
in back flies at a lower angle of attack than the thing in front. The thing in
back may, but need not, fly at a negative angle of attack."
http://www.av8n.com/how/htm/aoastab.html#sec-aoastab-summary

The pitch stability discussion is at:
http://www.av8n.com/how/htm/aoastab.html#sec-pitch-equilibrium

[Michael Henry[_2_]]

Phil J wrote:
> Here's another question for you engineers out there. Traditional
> airplane design has the tail pressing down, so the tail is fighting
> the work that the main wing is doing. A tandem-wing airplane in which
> both front and rear wings are lifting upward is a more efficient
> design, which is one reason Bert Rutan chose the canard configuration
> for so many of his designs. But in the canard configuration, the
> front wing is smaller than the rear wing. This is what I don't
> understand. It seems to me that a design in which the front wing was
> larger and the rear wing was smaller would be more stable in pitch.
> The smaller rear wing would automatically damp pitch excursions like
> the fins of an arrow. So why is the canard the most successful tandem-
> wing design flying?

There are a couple of "tandem wing" designs I can think of:

1) Samuel Pierpont Langley's "Aerodrome"
http://home.att.net/~dannysoar2/Langley.htm

2) The Mignet Pou du Ciel (Flying Flea)
http://www.flyingflea.org/

The Aerodrome was made to fly briefly after heavy modification by Glen
Curtiss. The Pou du Ciel, which is now a generic term covering a family
of designs using similar configuration, has been flying since the 1930s.

I'm not an aeronautical engineer (I wish!) but from my reading of your
post you are implying that the canard configuration is less stable in
pitch. The way I figure it is that while having a lifting surface ahead
of the CG is dynamically unstable (movement away from a stable "neutral"
configuration will produce forces which accelerate the movement away
from neutral) there is still the main wing behind the CG which will
produce a much greater force and return the aircraft to the neutral
position.

This sentence: "The smaller rear wing would automatically damp pitch
excursions like the fins of an arrow" applies to a normal
"downward-pushing" elevator too. However I don't think you can just make
a blanket statement along the lines of "this is less efficient because
it's working against the wing". I suspect other considerations such as
stability and control come into play here. One only has to look at the
design of modern airliners to see that those other considerations
override the potential efficiency gains of eliminating the
downward-pushing elevator.

[William Hung[_2_]]

On Feb 2, 11:59*am, Bertie the Bunyip > wrote:
> Phil J > wrote in news:e5efb14f-c2c5-41c7-a127-
> :
>
>
>
> > Here's another question for you engineers out there. *Traditional
> > airplane design has the tail pressing down, so the tail is fighting
> > the work that the main wing is doing. *A tandem-wing airplane in which
> > both front and rear wings are lifting upward is a more efficient
> > design, which is one reason Bert Rutan chose the canard configuration
> > for so many of his designs. *But in the canard configuration, the
> > front wing is smaller than the rear wing. *This is what I don't
> > understand. *It seems to me that a design in which the front wing was
> > larger and the rear wing was smaller would be more stable in pitch.
> > The smaller rear wing would automatically damp pitch excursions like
> > the fins of an arrow. *So why is the canard the most successful
> tandem-
> > wing design flying?
>
> Well, it isn't a tandem wing, for one thing. It's a canard. It's front
> "wing" is called a canard and not a wing. You could say it's a tomato
> tomato thing, but that's the definition. A Bleriot could also be called
> a tandem wing aircraft if you used the same standard. It's tail lifts.
> So do most free flight models. These airplanes have very large stabs (or
> wings, if you prefer), and very far aft CGs as compared to a a
> "conventional" aircraft and usually very long fuselages.
> Aircraft like the Bleriot were not very stable in pitch, and RC
> conversions of old time free flight airplanes with the original FF CG
> are very twitchy in pitch if elevator is used.
>
> *The basic principle is that more of the horizontal surface ( multiplied
> by it's arm) has to be behind the CG to get the thing going in the
> direction you want it to. Think horizontal weather vane.
> That's pretty simplistic, but basically it's the way it works. The
> horizontal weather vane principle also explains why conventional
> aircraft get nasty when their CG is moved aft. Never mind any rubbish
> Jepeson might tell you about the elevators making lift the wrong way.
> .
> I'm not exactly sure what the definition of a tandem wing is, percentage
> wise, but basically if it looks like one then it is one. That is, the
> wings should be in the neighborhood of each other area wise.
> The Flying Flea would be a good example.
>
> Bertie

I was gonna mention the Flea. The Frogs seam to like the Fleas.

Wil

[Bertie the Bunyip[_24_]]

William Hung > wrote in news:356251e4-f6d9-420e-a4d8-
:

> On Feb 2, 11:59*am, Bertie the Bunyip > wrote:
>> Phil J > wrote in news:e5efb14f-c2c5-41c7-a127-
>> :
>>
>>
>>
>> > Here's another question for you engineers out there. *Traditional
>> > airplane design has the tail pressing down, so the tail is fighting
>> > the work that the main wing is doing. *A tandem-wing airplane in
which
>
>> > both front and rear wings are lifting upward is a more efficient
>> > design, which is one reason Bert Rutan chose the canard
configuration
>> > for so many of his designs. *But in the canard configuration, the
>> > front wing is smaller than the rear wing. *This is what I don't
>> > understand. *It seems to me that a design in which the front wing
was
>> > larger and the rear wing was smaller would be more stable in pitch.
>> > The smaller rear wing would automatically damp pitch excursions
like
>> > the fins of an arrow. *So why is the canard the most successful
>> tandem-
>> > wing design flying?
>>
>> Well, it isn't a tandem wing, for one thing. It's a canard. It's
front
>> "wing" is called a canard and not a wing. You could say it's a tomato
>> tomato thing, but that's the definition. A Bleriot could also be
called
>> a tandem wing aircraft if you used the same standard. It's tail
lifts.
>> So do most free flight models. These airplanes have very large stabs
(or
>> wings, if you prefer), and very far aft CGs as compared to a a
>> "conventional" aircraft and usually very long fuselages.
>> Aircraft like the Bleriot were not very stable in pitch, and RC
>> conversions of old time free flight airplanes with the original FF CG
>> are very twitchy in pitch if elevator is used.
>>
>> *The basic principle is that more of the horizontal surface (
multiplied
>
>> by it's arm) has to be behind the CG to get the thing going in the
>> direction you want it to. Think horizontal weather vane.
>> That's pretty simplistic, but basically it's the way it works. The
>> horizontal weather vane principle also explains why conventional
>> aircraft get nasty when their CG is moved aft. Never mind any rubbish
>> Jepeson might tell you about the elevators making lift the wrong way.
>> .
>> I'm not exactly sure what the definition of a tandem wing is,
percentage
>> wise, but basically if it looks like one then it is one. That is, the
>> wings should be in the neighborhood of each other area wise.
>> The Flying Flea would be a good example.
>>
>> Bertie
>
> I was gonna mention the Flea. The Frogs seam to like the Fleas.

Definitely not my cup of tea, but the early ones have a funky look
that's irresistable! The French were fodn of Tandem wings period. There
was a guy named Delanne who made a few in the thirties and forties. and
there was a light plane called the Payen tht was near enough a Tndem
wing that made no difference. I don't know much about how either one
flew, but Delanne made a lot of different airplanes and I think a few
Payens were made and flew for a good few years.


Bertie

[Phil J]

On Feb 2, 4:22*pm, wrote:
> On Feb 2, 2:21 pm, Bertie the Bunyip > wrote:
>
> > So, tu summarise, if you put the "smaller wing" (sic) in the back, it';s
> > a tail unless it;s lifting. If it's lifting it needs to be fairly large
> > to be useful. make it large enough and you have problems with handling,
> > one solutuion for this problem is to reduce the sizre of the forward
> > wing and move the CG aft. Voila! you have a canard!
>
> > Bertie
>
> * * * *Seems to me that lifting tails are, and have been, illegal for
> long time. The regs call for the aircraft to automatically settle into
> a glide if the power should fail, to prevent stalling. A lifting tail
> just won't do this. As the airplane slows it will drop, raising the
> nose, and the airplane will stall, and almost certainly enter an
> unrecoverable spin. If the pilot does manage to establish a glide, the
> nose will drop further as glide speed increases, opposite to what we
> know in our airplanes, and totally unstable. Some early airplanes were
> built this way, and after they'd killed enough pilots the designers
> decided to make things differently.
> * *See FAR 23 (U.S.) or CAR 523 (Canadian) for the details.
>
> * * * *Dan

OK, this makes sense. Since a small lifting tail would be a long way
from the CG (compared to the main wing), it would experience a much
higher angle of attack when the aircraft pitched up. It would be very
difficult to make the main wing stall before the tail.

Phil

[Bertie the Bunyip[_25_]]

Phil J > wrote in
:

> On Feb 2, 4:22*pm, wrote:
>> On Feb 2, 2:21 pm, Bertie the Bunyip > wrote:
>>
>> > So, tu summarise, if you put the "smaller wing" (sic) in the back,
>> > it';s
>
>> > a tail unless it;s lifting. If it's lifting it needs to be fairly
>> > large to be useful. make it large enough and you have problems with
>> > handling, one solutuion for this problem is to reduce the sizre of
>> > the forward wing and move the CG aft. Voila! you have a canard!
>>
>> > Bertie
>>
>> * * * *Seems to me that lifting tails are, and have been, illegal
> for
>> long time. The regs call for the aircraft to automatically settle
>> into a glide if the power should fail, to prevent stalling. A lifting
>> tail just won't do this. As the airplane slows it will drop, raising
>> the nose, and the airplane will stall, and almost certainly enter an
>> unrecoverable spin. If the pilot does manage to establish a glide,
>> the nose will drop further as glide speed increases, opposite to what
>> we know in our airplanes, and totally unstable. Some early airplanes
>> were built this way, and after they'd killed enough pilots the
>> designers decided to make things differently.
>> * *See FAR 23 (U.S.) or CAR 523 (Canadian) for the details.
>>
>> * * * *Dan
>
> OK, this makes sense. Since a small lifting tail would be a long way
> from the CG (compared to the main wing), it would experience a much
> higher angle of attack when the aircraft pitched up. It would be very
> difficult to make the main wing stall before the tail.


Actually, it wouldn't. It's easy. You're not talking about nailing a
lifting tail to a Cessna. You're talking a bespoke design and you
wouldn't have a small stab either. A lifting stab requires an aft CG and
so a completely different config anyway.

Bertie

[Phil J]

On Feb 2, 3:21*pm, Bertie the Bunyip > wrote:
> Phil J > wrote in news:75220ca0-969d-4a58-8dac-
> :
>
>
>
> > OK. *But why on the canards flying these days is the little wing in
> > front of the CG, and the big wing behind it. *It seems like it would
> > be more stable in pitch if the little wing was behind the CG.
>
> Then it wouldn't be a canard.
>
> *Putting
>
> > the little wing in front of the CG seems like it would make the
> > airplane inherently unstable in pitch. *Looking at Rutan's designs, it
> > looks like he countered this by using a swept main wing. *But that
> > would have been unnecessary if he had put the smaller wing in back.
> > The only reason I can think of to put the smaller wing out front would
> > be for pilot visibility, so maybe that's the explanation?
>
> No, it's because he wanted a canard. I explained above that having a
> lifitng stab, even a great big one, makes for a twitchy airplane. I'm
> sure that could be managed if you wanted, but it's not ever going to be
> a very happy airplane. The smaller "wing",on a canard is called a
> canard. It's primarily a stabilsation surface that also contributes to
> overall lift. It is not a wing
> There are probably several reasons that Rutan elected to sweep the wing.
> One, it gives good stability without sacrificing manueverability. two,
> it expands the CG limits and in the case of this aricraft, allows a
> shorter fuselage than would be the case if the weren't swept. .
> So, tu summarise, if you put the "smaller wing" (sic) in the back, it';s
> a tail unless it;s lifting. If it's lifting it needs to be fairly large
> to be useful. make it large enough and you have problems with handling,
> one solutuion for this problem is to reduce the sizre of the forward
> wing and move the CG aft. Voila! you have a canard!
>
> Bertie

OK, it's a canard if its primary function is stability rather than
lift. I guess Rutan's Quickie is more like what I was thinking
about. On that airplane the front wing contributes 60% of the lift,
so it's a true wing. And there you have the larger wing in front and
the smaller wing in back. I don't know much about the stall
characteristics of that airplane, but it definitely seems to be an
efficient design. With a 64-horsepower engine it has a 140-mph
cruise.

Phil

[patrick mitchel]

"Phil J" > wrote in message
...
On Feb 2, 3:21 pm, Bertie the Bunyip > wrote:
> Phil J > wrote in news:75220ca0-969d-4a58-8dac-
> :
>
>
>
> > OK. But why on the canards flying these days is the little wing in
> > front of the CG, and the big wing behind it. It seems like it would
> > be more stable in pitch if the little wing was behind the CG.
>
> Then it wouldn't be a canard.
>
> Putting
>
> > the little wing in front of the CG seems like it would make the
> > airplane inherently unstable in pitch. Looking at Rutan's designs, it
> > looks like he countered this by using a swept main wing. But that
> > would have been unnecessary if he had put the smaller wing in back.
> > The only reason I can think of to put the smaller wing out front would
> > be for pilot visibility, so maybe that's the explanation?
>
> No, it's because he wanted a canard. I explained above that having a
> lifitng stab, even a great big one, makes for a twitchy airplane. I'm
> sure that could be managed if you wanted, but it's not ever going to be
> a very happy airplane. The smaller "wing",on a canard is called a
> canard. It's primarily a stabilsation surface that also contributes to
> overall lift. It is not a wing
> There are probably several reasons that Rutan elected to sweep the wing.
> One, it gives good stability without sacrificing manueverability. two,
> it expands the CG limits and in the case of this aricraft, allows a
> shorter fuselage than would be the case if the weren't swept. .
> So, tu summarise, if you put the "smaller wing" (sic) in the back, it';s
> a tail unless it;s lifting. If it's lifting it needs to be fairly large
> to be useful. make it large enough and you have problems with handling,
> one solutuion for this problem is to reduce the sizre of the forward
> wing and move the CG aft. Voila! you have a canard!
>
> Bertie

OK, it's a canard if its primary function is stability rather than
lift. I guess Rutan's Quickie is more like what I was thinking
about. On that airplane the front wing contributes 60% of the lift,
so it's a true wing. And there you have the larger wing in front and
the smaller wing in back. I don't know much about the stall
characteristics of that airplane, but it definitely seems to be an
efficient design. With a 64-horsepower engine it has a 140-mph
cruise.

Phil

[patrick mitchel]

"Phil J" > wrote in message
...
On Feb 2, 3:21 pm, Bertie the Bunyip > wrote:
> Phil J > wrote in news:75220ca0-969d-4a58-8dac-
> :
>
>
>
> > OK. But why on the canards flying these days is the little wing in
> > front of the CG, and the big wing behind it. It seems like it would
> > be more stable in pitch if the little wing was behind the CG.
>
> Then it wouldn't be a canard.
>
> Putting
>
> > the little wing in front of the CG seems like it would make the
> > airplane inherently unstable in pitch. Looking at Rutan's designs, it
> > looks like he countered this by using a swept main wing. But that
> > would have been unnecessary if he had put the smaller wing in back.
> > The only reason I can think of to put the smaller wing out front would
> > be for pilot visibility, so maybe that's the explanation?
>
> No, it's because he wanted a canard. I explained above that having a
> lifitng stab, even a great big one, makes for a twitchy airplane. I'm
> sure that could be managed if you wanted, but it's not ever going to be
> a very happy airplane. The smaller "wing",on a canard is called a
> canard. It's primarily a stabilsation surface that also contributes to
> overall lift. It is not a wing
> There are probably several reasons that Rutan elected to sweep the wing.
> One, it gives good stability without sacrificing manueverability. two,
> it expands the CG limits and in the case of this aricraft, allows a
> shorter fuselage than would be the case if the weren't swept. .
> So, tu summarise, if you put the "smaller wing" (sic) in the back, it';s
> a tail unless it;s lifting. If it's lifting it needs to be fairly large
> to be useful. make it large enough and you have problems with handling,
> one solutuion for this problem is to reduce the sizre of the forward
> wing and move the CG aft. Voila! you have a canard!
>
> Bertie

OK, it's a canard if its primary function is stability rather than
lift. I guess Rutan's Quickie is more like what I was thinking
about. On that airplane the front wing contributes 60% of the lift,
so it's a true wing. And there you have the larger wing in front and
the smaller wing in back. I don't know much about the stall
characteristics of that airplane, but it definitely seems to be an
efficient design. With a 64-horsepower engine it has a 140-mph
cruise.

Phil

[patrick mitchel]

Now about that Piaggio avanti....... Pat

[Bertie the Bunyip[_25_]]

Phil J > wrote in news:ad6eb94e-4e9e-46a8-b608-
:

> On Feb 2, 3:21*pm, Bertie the Bunyip > wrote:
>> Phil J > wrote in news:75220ca0-969d-4a58-8dac-
>> :
>>
>>
>>
>> > OK. *But why on the canards flying these days is the little wing in


>
> OK, it's a canard if its primary function is stability rather than
> lift. I guess Rutan's Quickie is more like what I was thinking
> about. On that airplane the front wing contributes 60% of the lift,
> so it's a true wing.


OK, that's right. I had forgoten about them. Yeah, That's a true tandem
wing.


And there you have the larger wing in front and
> the smaller wing in back. I don't know much about the stall
> characteristics of that airplane, but it definitely seems to be an
> efficient design. With a 64-horsepower engine it has a 140-mph
> cruise.

Yeah, I kow someone who built a Q200 and it cruises at about 160 mph on
100 hp! Superb.
The decalage, as with the canards, is arranged so that the front wing
reaches critical angle first thus lowering the nose. So, they don't
realy stal in the same way that a conventinal airplane does. I've never
flown one, though I have a standing offer to fly this one if I ever get
into his neighborhood. I would have thought that the rear wing was
taking more of the load, though, but i can't find any info on that on
the net. The thing that always made me nervous about those things is the
pounding the front wing must take on the ground..

Bertie

[Bertie the Bunyip[_25_]]

"patrick mitchel" > wrote in news:fo50mi$2bl2$1
@zook.lafn.org:

> Now about that Piaggio avanti....... Pat
>
>
>

Canard, . And I think the reason you're confused about Canards is this: The
canard is not there to provide stability. Not in the same way as a stab on
a stadard airplane. It's there to provide control. The wing provides the
stability in the way you understand it.


Bertie

[Phil J]

On Feb 3, 12:31*pm, Bertie the Bunyip > wrote:
> "patrick mitchel" > wrote in news:fo50mi$2bl2$1
> @zook.lafn.org:
>
> > *Now about that Piaggio avanti....... Pat
>
> Canard, . And I think the reason you're confused about Canards is this: The
> canard is not there to provide stability. Not in the same way as a stab on
> a stadard airplane. It's there to provide control. The wing provides the
> stability in the way you understand it.
>
> Bertie

I think you are referring to me rather than Pat, but I understand what
you are saying. On a canard design, the main wing functions like a
stab since it is behind the CG. OTOH, trying to figure out the
Piaggio seems like a good way to get a headache. It's amazing what
they were able to do with compound curves in aluminum on that
airplane, though.

Phil



Thanks to everyone who posted on this.

[Bertie the Bunyip[_25_]]

Phil J > wrote in
:

> On Feb 3, 12:31*pm, Bertie the Bunyip > wrote:
>> "patrick mitchel" > wrote in news:fo50mi$2bl2$1
>> @zook.lafn.org:
>>
>> > *Now about that Piaggio avanti....... Pat
>>
>> Canard, . And I think the reason you're confused about Canards is
>> this: Th
> e
>> canard is not there to provide stability. Not in the same way as a
>> stab on
>
>> a stadard airplane. It's there to provide control. The wing provides
>> the stability in the way you understand it.
>>
>> Bertie
>
> I think you are referring to me rather than Pat, but I understand what
> you are saying. On a canard design, the main wing functions like a
> stab since it is behind the CG. OTOH, trying to figure out the
> Piaggio seems like a good way to get a headache. It's amazing what
> they were able to do with compound curves in aluminum on that
> airplane, though.

Yes, that's pretty much it. The Piaggio is pretty, allright!

Bertie

[Bertie the Bunyip[_25_]]

"Marc J. Zeitlin" > wrote in news:47a60ac9$0
:

>
>> Dan_Thomas wrote:
>
>>> Seems to me that lifting tails are, and have been, illegal for
>>> long time.
>
> This is not true. There are no regulations that prohibit lifting
> tails, or in fact in any way prescribe which way the lift vector needs
> to point on any lifting surface.
>
>>> ... The regs call for the aircraft to automatically settle into a
>>> glide if the power should fail,to prevent stalling.
>
> What reg would that be? What airplane does NOT glide when the power
> fails? Your plane is trimmed for whatever speed you're flying - chop
> the power, and you'll continue to fly at that speed, albeit
> descending. There may be some trim changes on aircraft that have
> their engines mounted substantially above the CG (Lake Buccaneer, or
> the equivalent) or that have substantial thrust angles, but the
> principal holds.
>
> Stalling and gliding are independent activities - one is not related
> to the other. You can stall while gliding or under power, and you can
> glide while unstalled or stalled.
>
>>> ... A lifting tail just won't do this. As the airplane slows it
>>> will drop, raising the nose, and the airplane will stall, and
>>> almost certainly enter an unrecoverable spin.
>
> That's incorrect. In a conventional tailed aircraft, the tail may
> have a downforce, no force at all, or an upforce, depending upon the
> design of the aircraft, the relationship of the aerodynamic center to
> the CG, and the flight regime. There is no intrinsic reason why a
> lifting tail (or a tail that in a given situation is producing no
> lift) would cause the aircraft to do what you state.
>
>>> ... If the pilot does manage to establish a glide, the nose will
>>> drop further as glide speed increases, opposite to what we know
>>> in our airplanes, and totally unstable.
>
> Incorrect. The pitch stability of an aircraft is not determined by
> whether or not the tail lifts - it's determined by the relative
> position of the aerodynamic center and the CG (CG always ahead of AC),
> and the relative angles of the front and rear wings. See:
>
> http://www.av8n.com/how/htm/aoastab.html
>
> As long as the front wing is operating at a higher angle of attack
> than the rear wing - tail, wing, 2nd wing of a tandem; makes no
> difference - which is usually achieved by correct settings of the
> angle of incidence and ensuring that the front wing has a higher lift
> curve slope than the rear wing, then the aircraft will be statically
> stable in pitch.
>
> The above web site has some VERY good explanations and pictures of
> these situations, including canards. Consider a tandem aircraft to
> merely be a canard or conventional aircraft that has it's tail/canard
> to be about the same size as the other wing.
>
>>> ... Some early airplanes were built this way, and after they'd
>>> killed enough pilots the designers decided to make things
>>> differently.
>
> Hmmm. I wonder how my COZY MKIV canard aircraft maintains pitch
> stability, then, and in fact is extremely stall resistant. Scaled
> Composites' "Proteus" aircraft is essentially a tandem wing airplane -
> the front and rear wings are very close in size. The Piaggo Avanti
> has both a canard flying surface AND a tail.
>
> There are numerous examples of tandem, canard, and three surface
> aircraft that are completely stable in pitch, and have benign stall
> characteristics.
>
>>> See FAR 23 (U.S.) or CAR 523 (Canadian) for the details.
>
> Yes, see 23.302, which specifically references the canards and tandem
> wing aircraft. If they were "illegal", as you claim, there shouldn't
> be any reference to the rules with which they must comply. There are
> no other part 23 FARs that state what you claim.
>
>
> Phil J wrote:
>
>> OK, this makes sense.
>
> No, actually very little of what's been written in this thread makes
> any sense. There's a lot of misinformation about what makes aircraft
> work. The web site I pointed to above, while not perfect, has some
> excellent explanations of many aerodynamic points about which there is
> much misinformation, confusion, and clears up a lot of things that
> people know that just isn't true.
>
> Kyle Boatright was just about the only one to write something that
> made aerodynamic sense.


Beg yer pardon, but I posted pretty muc the same thing as you but in my
native tongue..

Bertie

[[email protected]]

On Feb 3, 11:43 am, "Marc J. Zeitlin" >
wrote:
> > Dan_Thomas wrote:
> >> Seems to me that lifting tails are, and have been, illegal for
> >> long time.
>
> This is not true. There are no regulations that prohibit lifting
> tails, or in fact in any way prescribe which way the lift vector needs
> to point on any lifting surface.
>
> >> ... The regs call for the aircraft to automatically settle into a
> >> glide if the power should fail,to prevent stalling.
>
> What reg would that be? What airplane does NOT glide when the power
> fails? Your plane is trimmed for whatever speed you're flying - chop
> the power, and you'll continue to fly at that speed, albeit
> descending. There may be some trim changes on aircraft that have
> their engines mounted substantially above the CG (Lake Buccaneer, or
> the equivalent) or that have substantial thrust angles, but the
> principal holds.
>
> Stalling and gliding are independent activities - one is not related
> to the other. You can stall while gliding or under power, and you can
> glide while unstalled or stalled.
>
> >> ... A lifting tail just won't do this. As the airplane slows it
> >> will drop, raising the nose, and the airplane will stall, and
> >> almost certainly enter an unrecoverable spin.
>
> That's incorrect. In a conventional tailed aircraft, the tail may
> have a downforce, no force at all, or an upforce, depending upon the
> design of the aircraft, the relationship of the aerodynamic center to
> the CG, and the flight regime. There is no intrinsic reason why a
> lifting tail (or a tail that in a given situation is producing no
> lift) would cause the aircraft to do what you state.
>
> >> ... If the pilot does manage to establish a glide, the nose will
> >> drop further as glide speed increases, opposite to what we know
> >> in our airplanes, and totally unstable.
>
> Incorrect. The pitch stability of an aircraft is not determined by
> whether or not the tail lifts - it's determined by the relative
> position of the aerodynamic center and the CG (CG always ahead of AC),
> and the relative angles of the front and rear wings. See:
>
> http://www.av8n.com/how/htm/aoastab.html
>
> As long as the front wing is operating at a higher angle of attack
> than the rear wing - tail, wing, 2nd wing of a tandem; makes no
> difference - which is usually achieved by correct settings of the
> angle of incidence and ensuring that the front wing has a higher lift
> curve slope than the rear wing, then the aircraft will be statically
> stable in pitch.
>
> The above web site has some VERY good explanations and pictures of
> these situations, including canards. Consider a tandem aircraft to
> merely be a canard or conventional aircraft that has it's tail/canard
> to be about the same size as the other wing.
>
> >> ... Some early airplanes were built this way, and after they'd
> >> killed enough pilots the designers decided to make things
> >> differently.
>
> Hmmm. I wonder how my COZY MKIV canard aircraft maintains pitch
> stability, then, and in fact is extremely stall resistant. Scaled
> Composites' "Proteus" aircraft is essentially a tandem wing airplane -
> the front and rear wings are very close in size. The Piaggo Avanti
> has both a canard flying surface AND a tail.
>
> There are numerous examples of tandem, canard, and three surface
> aircraft that are completely stable in pitch, and have benign stall
> characteristics.
>
> >> See FAR 23 (U.S.) or CAR 523 (Canadian) for the details.
>
> Yes, see 23.302, which specifically references the canards and tandem
> wing aircraft. If they were "illegal", as you claim, there shouldn't
> be any reference to the rules with which they must comply. There are
> no other part 23 FARs that state what you claim.
>
> Phil J wrote:
> > OK, this makes sense.
>
> No, actually very little of what's been written in this thread makes
> any sense. There's a lot of misinformation about what makes aircraft
> work. The web site I pointed to above, while not perfect, has some
> excellent explanations of many aerodynamic points about which there is
> much misinformation, confusion, and clears up a lot of things that
> people know that just isn't true.
>
> Kyle Boatright was just about the only one to write something that
> made aerodynamic sense.
>
> > ... Since a small lifting tail would be a long way from the CG
> > (compared to the main wing), it would experience a much higher
> > angle of attack when the aircraft pitched up.
>
> Not so. The distance of a lifting surface from the CG has no bearing
> whatsoever on the AOA that the surface sees in a static situation.
> During the dynamic rotation, there would be a slight difference, but
> it's not particularly meaningful. See the web site listed above for a
> great description/explanation of pitch stability (among many other
> things).
>
> > ... It would be very difficult to make the main wing stall before
> > the tail.
>
> Not so. See the explanations above. I have a canard aircraft. The
> canard wing (in front) has a higher incidence angle and lift curve
> slope than the rear wing. As long as I keep the CG ahead of the
> rearmost CG position, the aircraft will be stable in pitch, and the
> front wing will ALWAYS stall first. When this happens, the nose
> drops, and the rear wing maintains an appropriate AOA and doesn't stall.
>
> Same thing happens on tandem wing aircraft, or conventional aircraft
> with lifting tails.
>
> Hope this helps clear things up.
>
> --
> Marc J. Zeitlin
> http://www.cozybuilders.org/
> Copyright (c) 2008 http://www.mdzeitlin.com/Marc/


Here are two conflicting statements you made:

> In a conventional tailed aircraft, the tail may
> have a downforce, no force at all, or an upforce, depending upon the
> design of the aircraft, the relationship of the aerodynamic center to
> the CG, and the flight regime. There is no intrinsic reason why a
> lifting tail (or a tail that in a given situation is producing no
> lift) would cause the aircraft to do what you state.


> The pitch stability of an aircraft is not determined by
> whether or not the tail lifts - it's determined by the relative
> position of the aerodynamic center and the CG (CG always ahead of AC),
> and the relative angles of the front and rear wings.

I was talking about airplanes that appear conventional, like
the lightplanes we have now. With a lifting tail the CG must be behind
the AC, not ahead of it, and stability would be negative. I was not
talking about canards like the Cozy or any other Rutan-inspired
design, or the tandems. Some early conventional-layout airplanes used
lifting tails and were deadly.
Which "conventional tailed aircraft" would have any upforce
in level flight?

Dan

[Bertie the Bunyip[_25_]]

wrote in news:f886c681-9425-48a9-831d-
:
>
>
> Here are two conflicting statements you made:


They arent conflicting. They're the same statement made two different ways.

>
>> In a conventional tailed aircraft, the tail may
>> have a downforce, no force at all, or an upforce, depending upon the
>> design of the aircraft, the relationship of the aerodynamic center to
>> the CG, and the flight regime. There is no intrinsic reason why a
>> lifting tail (or a tail that in a given situation is producing no
>> lift) would cause the aircraft to do what you state.
>
>
>> The pitch stability of an aircraft is not determined by
>> whether or not the tail lifts - it's determined by the relative
>> position of the aerodynamic center and the CG (CG always ahead of AC),
>> and the relative angles of the front and rear wings.
>
> I was talking about airplanes that appear conventional, like
> the lightplanes we have now. With a lifting tail the CG must be behind
> the AC, not ahead of it, and stability would be negative.



Nope, because th estab is part of the AC and the stab on a lifting stab
arrangement is significantly larger thna it's conventional counterpart.



Bertie

[WingFlaps]

On Feb 3, 10:11*am, Phil J > wrote:
> On Feb 2, 1:59*pm, Bertie the Bunyip > wrote:
>
>
>
>
>
> > Well, it isn't a tandem wing, for one thing. It's a canard. It's front
> > "wing" is called a canard and not a wing. You could say it's a tomato
> > tomato thing, but that's the definition. A Bleriot could also be called
> > a tandem wing aircraft if you used the same standard. It's tail lifts.
> > So do most free flight models. These airplanes have very large stabs (or
> > wings, if you prefer), and very far aft CGs as compared to a a
> > "conventional" aircraft and usually very long fuselages.
> > Aircraft like the Bleriot were not very stable in pitch, and RC
> > conversions of old time free flight airplanes with the original FF CG
> > are very twitchy in pitch if elevator is used.
>
> > *The basic principle is that more of the horizontal surface ( multiplied
> > by it's arm) has to be behind the CG to get the thing going in the
> > direction you want it to. Think horizontal weather vane.
> > That's pretty simplistic, but basically it's the way it works. The
> > horizontal weather vane principle also explains why conventional
> > aircraft get nasty when their CG is moved aft. Never mind any rubbish
> > Jepeson might tell you about the elevators making lift the wrong way.
> > .
> > I'm not exactly sure what the definition of a tandem wing is, percentage
> > wise, but basically if it looks like one then it is one. That is, the
> > wings should be in the neighborhood of each other area wise.
> > The Flying Flea would be a good example.
>
> > Bertie
>
> OK. *But why on the canards flying these days is the little wing in
> front of the CG, and the big wing behind it. *It seems like it would
> be more stable in pitch if the little wing was behind the CG. *

So now you want both wings behind the CG generating lift? How do you
think it will balance?

Cheers

[Phil J]

On Feb 3, 10:45*pm, WingFlaps > wrote:
>
> > OK. *But why on the canards flying these days is the little wing in
> > front of the CG, and the big wing behind it. *It seems like it would
> > be more stable in pitch if the little wing was behind the CG. *
>
> So now you want both wings behind the CG generating lift? How do you
> think it will balance?
>
> Cheers

No. I was talking about the larger wing being in front of the CG, and
the smaller wing behind the CG.

Phil

[[email protected]]

On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
wrote:

> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
> behind the main wing AC. There are many aircraft that when flown at
> rear CG positions and low speeds will have the tail producing lift.
> Gliders, in particular. Off the top of my head, I don't know of any
> in particular, although I remember being told that a C-172 will have
> an upforce on the tail at low speeds and rear CG. Can't cite it, though.

Even with the CG at its most aft position, a 172's AC is still
behind the CG. CG range is typically 25-33% of MAC, while AC is around
40%.

>
> The web site I indicated:
>
> http://www.av8n.com/how/htm/aoastab.html
>
> explains all this.

That's a good site that I've used for more than four years. I
think we're talking about two different things here and there's a
misunderstanding that leads to argument.
I find a fairly widely-held opinion that the aft CG can be
(legally) at or behind AC. This isn't true for any "modern"
lightplane. FAR 23.173 requires that the airplane return to trimmed
speed after being slowed or accelerated using pitch inputs only and
releasing them; this won't happen in a CG-behind-AC situation. As the
wing slows its AC moves forward due to the breakup of the boundary
layer toward the trailing edge, the CG therefore ends up even farther
behind the AC, the situation gets worse as the nose rises with the
forward-moving AC, and it eventually stalls. This is what I meant by
the illegality of a lifting tail.
Here's an example of some common miperceptions:
http://answers.yahoo.com/question/index?qid=20080109225927AAfYZDU
Even the first answer, the one the voters liked, says that the CG is
12" ahead of the AC even in the most-aft position, This is extreme;
it's a lot less than that, but it's still forward. Other posters think
that with the CG at the aft position the tail must produce lift.

Dan

Dan

[Bertie the Bunyip[_25_]]

wrote in
:

> On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> wrote:
>
>> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
>> behind the main wing AC. There are many aircraft that when flown at
>> rear CG positions and low speeds will have the tail producing lift.
>> Gliders, in particular. Off the top of my head, I don't know of any
>> in particular, although I remember being told that a C-172 will have
>> an upforce on the tail at low speeds and rear CG. Can't cite it,
>> though.
>
> Even with the CG at its most aft position, a 172's AC is still
> behind the CG. CG range is typically 25-33% of MAC, while AC is around
> 40%.
>

We're not talking about a 172.


Bertie

[[email protected]]

On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
> wrote :
>
> > On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> > wrote:
>
> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
> >> behind the main wing AC. There are many aircraft that when flown at
> >> rear CG positions and low speeds will have the tail producing lift.
> >> Gliders, in particular. Off the top of my head, I don't know of any
> >> in particular, although I remember being told that a C-172 will have
> >> an upforce on the tail at low speeds and rear CG. Can't cite it,
> >> though.
>
> > Even with the CG at its most aft position, a 172's AC is still
> > behind the CG. CG range is typically 25-33% of MAC, while AC is around
> > 40%.
>
> We're not talking about a 172.
>
> Bertie

OK. I'll leave now.

Dan

[Ken S. Tucker]

On Feb 4, 6:53 am, wrote:
> On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> wrote:
>
> > Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
> > behind the main wing AC. There are many aircraft that when flown at
> > rear CG positions and low speeds will have the tail producing lift.
> > Gliders, in particular. Off the top of my head, I don't know of any
> > in particular, although I remember being told that a C-172 will have
> > an upforce on the tail at low speeds and rear CG. Can't cite it, though.
>
> Even with the CG at its most aft position, a 172's AC is still
> behind the CG. CG range is typically 25-33% of MAC, while AC is around
> 40%.
>
>
>
> > The web site I indicated:
>
> > http://www.av8n.com/how/htm/aoastab.html
>
> > explains all this.
>
> That's a good site that I've used for more than four years. I
> think we're talking about two different things here and there's a
> misunderstanding that leads to argument.
> I find a fairly widely-held opinion that the aft CG can be
> (legally) at or behind AC. This isn't true for any "modern"
> lightplane. FAR 23.173 requires that the airplane return to trimmed
> speed after being slowed or accelerated using pitch inputs only and
> releasing them; this won't happen in a CG-behind-AC situation. As the
> wing slows its AC moves forward due to the breakup of the boundary
> layer toward the trailing edge, the CG therefore ends up even farther
> behind the AC, the situation gets worse as the nose rises with the
> forward-moving AC, and it eventually stalls. This is what I meant by
> the illegality of a lifting tail.
> Here's an example of some common miperceptions:http://answers.yahoo.com/question/index?qid=20080109225927AAfYZDU
> Even the first answer, the one the voters liked, says that the CG is
> 12" ahead of the AC even in the most-aft position, This is extreme;
> it's a lot less than that, but it's still forward. Other posters think
> that with the CG at the aft position the tail must produce lift.
> Dan

My experiments with models vindicate Dan's
explanation where a conventional planform is
concerned. Setting the CG = AC can cause a
screwy stall, such as nose pitch-up.
Ken

[Bertie the Bunyip[_25_]]

"Ken S. Tucker" > wrote in
:

> On Feb 4, 6:53 am, wrote:
>> On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
>> wrote:
>>
>> > Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
>> > behind the main wing AC. There are many aircraft that when flown
>> > at rear CG positions and low speeds will have the tail producing
>> > lift. Gliders, in particular. Off the top of my head, I don't know
>> > of any in particular, although I remember being told that a C-172
>> > will have an upforce on the tail at low speeds and rear CG. Can't
>> > cite it, though.
>>
>> Even with the CG at its most aft position, a 172's AC is still
>> behind the CG. CG range is typically 25-33% of MAC, while AC is
>> around 40%.
>>
>>
>>
>> > The web site I indicated:
>>
>> > http://www.av8n.com/how/htm/aoastab.html
>>
>> > explains all this.
>>
>> That's a good site that I've used for more than four years. I
>> think we're talking about two different things here and there's a
>> misunderstanding that leads to argument.
>> I find a fairly widely-held opinion that the aft CG can be
>> (legally) at or behind AC. This isn't true for any "modern"
>> lightplane. FAR 23.173 requires that the airplane return to trimmed
>> speed after being slowed or accelerated using pitch inputs only and
>> releasing them; this won't happen in a CG-behind-AC situation. As the
>> wing slows its AC moves forward due to the breakup of the boundary
>> layer toward the trailing edge, the CG therefore ends up even farther
>> behind the AC, the situation gets worse as the nose rises with the
>> forward-moving AC, and it eventually stalls. This is what I meant by
>> the illegality of a lifting tail.
>> Here's an example of some common
>> miperceptions:http://answers.yahoo.com/question/index?qid=
2008
>> 0109225927AAfYZDU
>> Even the first answer, the one the voters liked, says that the CG is
>> 12" ahead of the AC even in the most-aft position, This is extreme;
>> it's a lot less than that, but it's still forward. Other posters
>> think that with the CG at the aft position the tail must produce
>> lift.
>> Dan
>
> My experiments with models vindicate Dan's
> explanation where a conventional planform is
> concerned. Setting the CG = AC can cause a
> screwy stall, such as nose pitch-up.

Sorry Dan, but that pretty much wraps it up. Ken agrees with you. You
need to crack the books!

Bertie

[Bertie the Bunyip[_25_]]

wrote in
:

> On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
>> wrote
>> innews:dad75380-7e0e-40c6-965a-

>> om:
>>
>> > On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
>> > wrote:
>>
>> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
>> >> behind the main wing AC. There are many aircraft that when flown
>> >> at rear CG positions and low speeds will have the tail producing
>> >> lift. Gliders, in particular. Off the top of my head, I don't
>> >> know of any in particular, although I remember being told that a
>> >> C-172 will have an upforce on the tail at low speeds and rear CG.
>> >> Can't cite it, though.
>>
>> > Even with the CG at its most aft position, a 172's AC is
>> > still
>> > behind the CG. CG range is typically 25-33% of MAC, while AC is
>> > around 40%.
>>
>> We're not talking about a 172.
>>
>> Bertie
>
> OK. I'll leave now.

Why? Ken likes you!

Seriously, I know what you're talking about, but your head is stuck in
the standard issue light airplane. You're not exactly wrong, but you're
missing the point. The OP is talking about putting an airplane together,
not loading one up.


Bertie

[[email protected]]

On Feb 4, 12:41 pm, Bertie the Bunyip > wrote:
> wrote :
>
> > On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
> >> wrote
> >> innews:dad75380-7e0e-40c6-965a-
>
>
>
>
>
> >> om:
>
> >> > On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> >> > wrote:
>
> >> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
> >> >> behind the main wing AC. There are many aircraft that when flown
> >> >> at rear CG positions and low speeds will have the tail producing
> >> >> lift. Gliders, in particular. Off the top of my head, I don't
> >> >> know of any in particular, although I remember being told that a
> >> >> C-172 will have an upforce on the tail at low speeds and rear CG.
> >> >> Can't cite it, though.
>
> >> > Even with the CG at its most aft position, a 172's AC is
> >> > still
> >> > behind the CG. CG range is typically 25-33% of MAC, while AC is
> >> > around 40%.
>
> >> We're not talking about a 172.
>
> >> Bertie
>
> > OK. I'll leave now.
>
> Why? Ken likes you!
>
> Seriously, I know what you're talking about, but your head is stuck in
> the standard issue light airplane. You're not exactly wrong, but you're
> missing the point. The OP is talking about putting an airplane together,
> not loading one up.
>
> Bertie

I suppose I missed the point. But it disturbs me that Ken
agrees with me. Either he's right for once or I'm way off base.

Dan

[Morgans[_2_]]

> wrote >
> I suppose I missed the point. But it disturbs me that Ken
> agrees with me. Either he's right for once or I'm way off base.

The fact that he makes this determination based on his observation of model
planes further reinforces his lack of real and tangible knowledge of the
subject at hand.

And anyway, even a stopped clock is right once (or twice) per day.

I would be disturbed, too. Don't take it too hard, though. It was a lucky
guess.
--
Jim in NC

[Ken S. Tucker]

On Feb 4, 12:09 pm, wrote:
> On Feb 4, 12:41 pm, Bertie the Bunyip > wrote:
>
>
>
> > wrote :
>
> > > On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
> > >> wrote
> > >> innews:dad75380-7e0e-40c6-965a-
>
> >
>
> > >> om:
>
> > >> > On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> > >> > wrote:
>
> > >> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
> > >> >> behind the main wing AC. There are many aircraft that when flown
> > >> >> at rear CG positions and low speeds will have the tail producing
> > >> >> lift. Gliders, in particular. Off the top of my head, I don't
> > >> >> know of any in particular, although I remember being told that a
> > >> >> C-172 will have an upforce on the tail at low speeds and rear CG.
> > >> >> Can't cite it, though.
>
> > >> > Even with the CG at its most aft position, a 172's AC is
> > >> > still
> > >> > behind the CG. CG range is typically 25-33% of MAC, while AC is
> > >> > around 40%.
>
> > >> We're not talking about a 172.
>
> > >> Bertie
>
> > > OK. I'll leave now.
>
> > Why? Ken likes you!
>
> > Seriously, I know what you're talking about, but your head is stuck in
> > the standard issue light airplane. You're not exactly wrong, but you're
> > missing the point. The OP is talking about putting an airplane together,
> > not loading one up.
>
> > Bertie
>
> I suppose I missed the point. But it disturbs me that Ken
> agrees with me. Either he's right for once or I'm way off base.
> Dan

Berties OP wasn't bad, but it's primitive.
He ignored (or is ignorant) of Rutan twisting
the main wings on his Veri-Eze 4degrees +,
at the tip. That "feeds-back" in the CL to pull
it backward to alleviate the CL going forward
when the main begins stalling at the hip, that
Dan (the BIG HEAD) described surprisingly
well.

Score +1 for BIG HEAD, Bertie -1.

What I do is calculate the CL off the geometry
of the model A/C adjust the CG and fly them.
Saves a lot of crashing and burning.
Ken

PS: Dan, you thawing out your nuts yet?

[Dan Luke[_2_]]

"Bertie the Bunyip" wrote:

> Ken agrees with you.

Eeewww!

Usenet cooties!

[Ken S. Tucker]

On Feb 4, 1:39 pm, "Ken S. Tucker" > wrote:
> On Feb 4, 12:09 pm, wrote:
>
>
>
> > On Feb 4, 12:41 pm, Bertie the Bunyip > wrote:
>
> > > wrote :
>
> > > > On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
> > > >> wrote
> > > >> innews:dad75380-7e0e-40c6-965a-
>
> > >
>
> > > >> om:
>
> > > >> > On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> > > >> > wrote:
>
> > > >> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
> > > >> >> behind the main wing AC. There are many aircraft that when flown
> > > >> >> at rear CG positions and low speeds will have the tail producing
> > > >> >> lift. Gliders, in particular. Off the top of my head, I don't
> > > >> >> know of any in particular, although I remember being told that a
> > > >> >> C-172 will have an upforce on the tail at low speeds and rear CG.
> > > >> >> Can't cite it, though.
>
> > > >> > Even with the CG at its most aft position, a 172's AC is
> > > >> > still
> > > >> > behind the CG. CG range is typically 25-33% of MAC, while AC is
> > > >> > around 40%.
>
> > > >> We're not talking about a 172.
>
> > > >> Bertie
>
> > > > OK. I'll leave now.
>
> > > Why? Ken likes you!
>
> > > Seriously, I know what you're talking about, but your head is stuck in
> > > the standard issue light airplane. You're not exactly wrong, but you're
> > > missing the point. The OP is talking about putting an airplane together,
> > > not loading one up.
>
> > > Bertie
>
> > I suppose I missed the point. But it disturbs me that Ken
> > agrees with me. Either he's right for once or I'm way off base.
> > Dan
>
> Berties OP wasn't bad, but it's primitive.
> He ignored (or is ignorant) of Rutan twisting
> the main wings on his Veri-Eze 4degrees +,
> at the tip.

Correction that should be -4 degrees.
The wing tip has a REDUCED AoA.
A 1000 pardons....

> That "feeds-back" in the CL to pull
> it backward to alleviate the CL going forward
> when the main begins stalling at the hip, that
> Dan (the BIG HEAD) described surprisingly
> well.
>
> Score +1 for BIG HEAD, Bertie -1.
>
> What I do is calculate the CL off the geometry
> of the model A/C adjust the CG and fly them.
> Saves a lot of crashing and burning.
> Ken
>
> PS: Dan, you thawing out your nuts yet?

[Bertie the Bunyip[_25_]]

wrote in
:

> On Feb 4, 12:41 pm, Bertie the Bunyip > wrote:
>> wrote
>> innews:da30af89-15c1-4b7b-8841-

>> om:
>>
>> > On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
>> >> wrote
>> >> innews:dad75380-7e0e-40c6-965a-
>>
>>
>>
>>
>>
>> >> om:
>>
>> >> > On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
>> >> > wrote:
>>
>> >> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC,
>> >> >> but behind the main wing AC. There are many aircraft that when
>> >> >> flown at rear CG positions and low speeds will have the tail
>> >> >> producing lift. Gliders, in particular. Off the top of my
>> >> >> head, I don't know of any in particular, although I remember
>> >> >> being told that a C-172 will have an upforce on the tail at low
>> >> >> speeds and rear CG. Can't cite it, though.
>>
>> >> > Even with the CG at its most aft position, a 172's AC is
>> >> > still
>> >> > behind the CG. CG range is typically 25-33% of MAC, while AC is
>> >> > around 40%.
>>
>> >> We're not talking about a 172.
>>
>> >> Bertie
>>
>> > OK. I'll leave now.
>>
>> Why? Ken likes you!
>>
>> Seriously, I know what you're talking about, but your head is stuck
>> in the standard issue light airplane. You're not exactly wrong, but
>> you're missing the point. The OP is talking about putting an airplane
>> together, not loading one up.
>>
>> Bertie
>
> I suppose I missed the point. But it disturbs me that Ken
> agrees with me. Either he's right for once or I'm way off base.


Well, you are and you aren't. If you put a lifting stab and an aft CG in
a 172 it's not going to be a happy airplane.
You have to include the lifting stab as a wing in it's own right..


Bertie

[Bertie the Bunyip[_25_]]

"Ken S. Tucker" > wrote in
:

> On Feb 4, 12:09 pm, wrote:
>> On Feb 4, 12:41 pm, Bertie the Bunyip > wrote:
>>
>>
>>
>> > wrote
>> > innews:da30af89-15c1-4b7b-8841-

>> > .com:
>>
>> > > On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
>> > >> wrote
>> > >> innews:dad75380-7e0e-40c6-965a-
>>
>> >
>>
>> > >> om:
>>
>> > >> > On Feb 3, 9:05 pm, "Marc J. Zeitlin"
>> > >> > > wrote:
>>
>> > >> >> Any aircraft in which the CG can be ahead of the AIRCRAFT AC,
>> > >> >> but behind the main wing AC. There are many aircraft that
>> > >> >> when flown at rear CG positions and low speeds will have the
>> > >> >> tail producing lift. Gliders, in particular. Off the top of
>> > >> >> my head, I don't know of any in particular, although I
>> > >> >> remember being told that a C-172 will have an upforce on the
>> > >> >> tail at low speeds and rear CG. Can't cite it, though.
>>
>> > >> > Even with the CG at its most aft position, a 172's AC
>> > >> > is still
>> > >> > behind the CG. CG range is typically 25-33% of MAC, while AC
>> > >> > is around 40%.
>>
>> > >> We're not talking about a 172.
>>
>> > >> Bertie
>>
>> > > OK. I'll leave now.
>>
>> > Why? Ken likes you!
>>
>> > Seriously, I know what you're talking about, but your head is stuck
>> > in the standard issue light airplane. You're not exactly wrong, but
>> > you're missing the point. The OP is talking about putting an
>> > airplane together, not loading one up.
>>
>> > Bertie
>>
>> I suppose I missed the point. But it disturbs me that Ken
>> agrees with me. Either he's right for once or I'm way off base.
>> Dan
>
> Berties OP wasn't bad, but it's primitive.

Yes, it is.


> He ignored (or is ignorant) of Rutan twisting
> the main wings on his Veri-Eze 4degrees +,


No I didn;'t , because it's irrelevant, fjukkwit.


> at the tip. That "feeds-back" in the CL to pull
> it backward to alleviate the CL going forward
> when the main begins stalling at the hip, that
> Dan (the BIG HEAD) described surprisingly
> well.


>
> Score +1 for BIG HEAD, Bertie -1.


Just shoot yourself now Dan.

Bertie

[Bertie the Bunyip[_25_]]

"Ken S. Tucker" > wrote in
:

> On Feb 4, 1:39 pm, "Ken S. Tucker" > wrote:
>> On Feb 4, 12:09 pm, wrote:
>>
>>
>>
>> > On Feb 4, 12:41 pm, Bertie the Bunyip > wrote:
>>
>> > > wrote
>> > > innews:da30af89-15c1-4b7b-8841-

>> > > ps.com:
>>
>> > > > On Feb 4, 8:48 am, Bertie the Bunyip > wrote:
>> > > >> wrote
>> > > >> innews:dad75380-7e0e-40c6-965a-
>>
>> > >
>>
>> > > >> om:
>>
>> > > >> > On Feb 3, 9:05 pm, "Marc J. Zeitlin"
>> > > >> > > wrote:
>>
>> > > >> >> Any aircraft in which the CG can be ahead of the AIRCRAFT
>> > > >> >> AC, but behind the main wing AC. There are many aircraft
>> > > >> >> that when flown at rear CG positions and low speeds will
>> > > >> >> have the tail producing lift. Gliders, in particular. Off
>> > > >> >> the top of my head, I don't know of any in particular,
>> > > >> >> although I remember being told that a C-172 will have an
>> > > >> >> upforce on the tail at low speeds and rear CG.
>> > > >> >> Can't cite it, though.
>>
>> > > >> > Even with the CG at its most aft position, a 172's AC
>> > > >> > is still
>> > > >> > behind the CG. CG range is typically 25-33% of MAC, while AC
>> > > >> > is around 40%.
>>
>> > > >> We're not talking about a 172.
>>
>> > > >> Bertie
>>
>> > > > OK. I'll leave now.
>>
>> > > Why? Ken likes you!
>>
>> > > Seriously, I know what you're talking about, but your head is
>> > > stuck in the standard issue light airplane. You're not exactly
>> > > wrong, but you're missing the point. The OP is talking about
>> > > putting an airplane together, not loading one up.
>>
>> > > Bertie
>>
>> > I suppose I missed the point. But it disturbs me that Ken
>> > agrees with me. Either he's right for once or I'm way off base.
>> > Dan
>>
>> Berties OP wasn't bad, but it's primitive.
>> He ignored (or is ignorant) of Rutan twisting
>> the main wings on his Veri-Eze 4degrees +,
>> at the tip.
>
> Correction that should be -4 degrees.
> The wing tip has a REDUCED AoA.


Either way, it;s irrelevant.


Bertie

[Bertie the Bunyip[_25_]]

"Morgans" > wrote in
:

>
> > wrote >
>> I suppose I missed the point. But it disturbs me that Ken
>> agrees with me. Either he's right for once or I'm way off base.
>
> The fact that he makes this determination based on his observation of
> model
> planes further reinforces his lack of real and tangible knowledge of
> the subject at hand.
>
> And anyway, even a stopped clock is right once (or twice) per day.
>
> I would be disturbed, too. Don't take it too hard, though. It was a
> lucky guess.



He's wrong, oh so wrong in this case as well.


Bertie

[Bertie the Bunyip[_25_]]

"Dan Luke" > wrote in news:13qf47hr26ig515
@news.supernews.com:

>
> "Bertie the Bunyip" wrote:
>
>> Ken agrees with you.
>
> Eeewww!
>
> Usenet cooties!
>
>
>

I know, it's got to be every poster's worst nightmare.

I think there may be a recovey group for this somewhere.



Bertie

[Morgans[_2_]]

"Bertie the Bunyip" > wrote

> He's wrong, oh so wrong in this case as well.

I'm not surprised at that, either. He had not been right about anything,
that I had noticed.

To tell the truth, (no surprise) I have not been reading this thread for
content. I've mainly just been skipping to the next message without really
reading them, to get them marked off as read.
--
Jim in NC

[Bertie the Bunyip[_25_]]

"Morgans" > wrote in
:

>
> "Bertie the Bunyip" > wrote
>
>> He's wrong, oh so wrong in this case as well.
>
> I'm not surprised at that, either. He had not been right about
> anything,
> that I had noticed.
>
> To tell the truth, (no surprise) I have not been reading this thread
> for content. I've mainly just been skipping to the next message
> without really reading them, to get them marked off as read.

well, it must be at least a bit interesting for an experimenter. The rocket
man posted som salient stuff there and understanding the relationship
between CG and the aerodynamic center is a very useful thing for a builder.
Not strictly neccesary, of course, but definitely nice to know. Less so for
a pilot...

Bertie

[Morgans[_2_]]

"Bertie the Bunyip" > wrote

> well, it must be at least a bit interesting for an experimenter. The
> rocket
> man posted som salient stuff there and understanding the relationship
> between CG and the aerodynamic center is a very useful thing for a
> builder.
> Not strictly neccesary, of course, but definitely nice to know. Less so
> for
> a pilot...

I feel I have a good grip on the relationship between CG an AC for
conventional planforms. I have no interest in canards or tandem lifting
wings.

I did pay a bit more attention to a few of the posts, though, and his being
some of them.
--
Jim in NC

[Ken S. Tucker]

On Feb 4, 3:04 pm, "Morgans" > wrote:
> "Bertie the Bunyip" > wrote
>
> > He's wrong, oh so wrong in this case as well.
>
> I'm not surprised at that, either. He had not been right about anything,
> that I had noticed.
>
> To tell the truth, (no surprise) I have not been reading this thread for
> content. I've mainly just been skipping to the next message without really
> reading them, to get them marked off as read.
> --
> Jim in NC

C&B!!!!!!!!

[Bertie the Bunyip[_25_]]

"Ken S. Tucker" > wrote in
:

> On Feb 4, 3:04 pm, "Morgans" > wrote:
>> "Bertie the Bunyip" > wrote
>>
>> > He's wrong, oh so wrong in this case as well.
>>
>> I'm not surprised at that, either. He had not been right about
>> anything,
>> that I had noticed.
>>
>> To tell the truth, (no surprise) I have not been reading this thread
>> for content. I've mainly just been skipping to the next message
>> without really reading them, to get them marked off as read.
>> --
>> Jim in NC
>
> C&B!!!!!!!!
>
J&B!!!!!!!


Bertie

[Morgans[_2_]]

"Morgans" > wrote

> I feel I have a good grip on the relationship between CG an AC for
> conventional planforms. I have no interest in canards or tandem lifting
> wings.
>
> I did pay a bit more attention to a few of the posts, though, and his
> being some of them.
I did not look at the link he provided, the first time. I went back, and
checked it out.

Most is pretty straight forward aerodynamic stuff that a person that has
done some reading on the subject will already know. It was a pretty good
site, though. Good read for a person that has not done that much reading on
aerodynamic stability.
--
Jim in NC

[Bertie the Bunyip[_25_]]

"Morgans" > wrote in
:

>
> "Bertie the Bunyip" > wrote
>
>> well, it must be at least a bit interesting for an experimenter. The
>> rocket
>> man posted som salient stuff there and understanding the relationship
>> between CG and the aerodynamic center is a very useful thing for a
>> builder.
>> Not strictly neccesary, of course, but definitely nice to know. Less
>> so for
>> a pilot...
>
> I feel I have a good grip on the relationship between CG an AC for
> conventional planforms. I have no interest in canards or tandem
> lifting wings.
>
> I did pay a bit more attention to a few of the posts, though, and his
> being some of them.


Well, it's relevant to conventional airplanes in an indirect sort of way,
which is my point. If you truly understand the principles involved, you
then thoroughly understand enough to trim your homebuilt. My own airplane
is notorious for needing stab adjustments after the first flight. A real
PITA since the stab is welded into position ( I plan to make mine
adjustable with shims) Now, the stab on my airplane has a negative
incidence, while the top wing is set at zero and the bottom is set at plus
2 degrees. Doesn't seem to add up, does it? The stab is flat plate, BTW.
So, waht's all that about?



Bertie

[Blueskies]

> wrote in message ...
> On Feb 3, 9:05 pm, "Marc J. Zeitlin" >
> wrote:
>
>> Any aircraft in which the CG can be ahead of the AIRCRAFT AC, but
>> behind the main wing AC. There are many aircraft that when flown at
>> rear CG positions and low speeds will have the tail producing lift.
>> Gliders, in particular. Off the top of my head, I don't know of any
>> in particular, although I remember being told that a C-172 will have
>> an upforce on the tail at low speeds and rear CG. Can't cite it, though.
>
> Even with the CG at its most aft position, a 172's AC is still
> behind the CG. CG range is typically 25-33% of MAC, while AC is around
> 40%.
>
>>
>> The web site I indicated:
>>
>> http://www.av8n.com/how/htm/aoastab.html
>>
>> explains all this.
>
> That's a good site that I've used for more than four years. I
> think we're talking about two different things here and there's a
> misunderstanding that leads to argument.
> I find a fairly widely-held opinion that the aft CG can be
> (legally) at or behind AC. This isn't true for any "modern"
> lightplane. FAR 23.173 requires that the airplane return to trimmed
> speed after being slowed or accelerated using pitch inputs only and
> releasing them; this won't happen in a CG-behind-AC situation. As the
> wing slows its AC moves forward due to the breakup of the boundary

>>>>> layer toward the trailing edge, the CG therefore ends up even farther
>>>>> behind the AC, the situation gets worse as the nose rises with the

****The CG is in front of the AC****

> forward-moving AC, and it eventually stalls. This is what I meant by
> the illegality of a lifting tail.
> Here's an example of some common miperceptions:
> http://answers.yahoo.com/question/index?qid=20080109225927AAfYZDU
> Even the first answer, the one the voters liked, says that the CG is
> 12" ahead of the AC even in the most-aft position, This is extreme;
> it's a lot less than that, but it's still forward. Other posters think
> that with the CG at the aft position the tail must produce lift.
>
> Dan
>

[Morgans[_2_]]

"Bertie the Bunyip" > wrote in message
...
> "Ken S. Tucker" > wrote in
> :
>
>> On Feb 4, 3:04 pm, "Morgans" > wrote:
>>> "Bertie the Bunyip" > wrote
>>>
>>> > He's wrong, oh so wrong in this case as well.
>>>
>>> I'm not surprised at that, either. He had not been right about
>>> anything,
>>> that I had noticed.
>>>
>>> To tell the truth, (no surprise) I have not been reading this thread
>>> for content. I've mainly just been skipping to the next message
>>> without really reading them, to get them marked off as read.
>>> --
>>> Jim in NC
>>
>> C&B!!!!!!!!
>>
> J&B!!!!!!!

The only thing Ken would be knowledgeable about would be giving B. J.'s
!!!!!!!!!
--
Jim in NC

[[email protected]]

On Feb 4, 3:52 pm, Bertie the Bunyip > wrote:

> Just shoot yourself now Dan.
>
> Bertie

Bang.

Dan

[Ken S. Tucker]

On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
> "Morgans" > wrote :
>
>
>
>
>
> > "Bertie the Bunyip" > wrote
>
> >> well, it must be at least a bit interesting for an experimenter. The
> >> rocket
> >> man posted som salient stuff there and understanding the relationship
> >> between CG and the aerodynamic center is a very useful thing for a
> >> builder.
> >> Not strictly neccesary, of course, but definitely nice to know. Less
> >> so for
> >> a pilot...
>
> > I feel I have a good grip on the relationship between CG an AC for
> > conventional planforms. I have no interest in canards or tandem
> > lifting wings.
>
> > I did pay a bit more attention to a few of the posts, though, and his
> > being some of them.
>
> Well, it's relevant to conventional airplanes in an indirect sort of way,
> which is my point. If you truly understand the principles involved, you
> then thoroughly understand enough to trim your homebuilt. My own airplane
> is notorious for needing stab adjustments after the first flight. A real
> PITA since the stab is welded into position ( I plan to make mine
> adjustable with shims) Now, the stab on my airplane has a negative
> incidence, while the top wing is set at zero and the bottom is set at plus
> 2 degrees. Doesn't seem to add up, does it? The stab is flat plate, BTW.
> So, waht's all that about?
>
> Bertie

I hear a candiate screamin for the Darwin Awards.
Leave flying to us pro's, you stay in outhouse.
.......

[Bertie the Bunyip[_25_]]

wrote in news:1e9f68a1-fd54-4824-9eeb-
:

> On Feb 4, 3:52 pm, Bertie the Bunyip > wrote:
>
>> Just shoot yourself now Dan.
>>
>> Bertie
>
> Bang.
>
> Dan
>

Better?

Bertie

[Bertie the Bunyip[_25_]]

"Ken S. Tucker" > wrote in
:

> On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
>> "Morgans" > wrote
>> :
>>
>>
>>
>>
>>
>> > "Bertie the Bunyip" > wrote
>>
>> >> well, it must be at least a bit interesting for an experimenter.
>> >> The rocket
>> >> man posted som salient stuff there and understanding the
>> >> relationship between CG and the aerodynamic center is a very
>> >> useful thing for a builder.
>> >> Not strictly neccesary, of course, but definitely nice to know.
>> >> Less so for
>> >> a pilot...
>>
>> > I feel I have a good grip on the relationship between CG an AC for
>> > conventional planforms. I have no interest in canards or tandem
>> > lifting wings.
>>
>> > I did pay a bit more attention to a few of the posts, though, and
>> > his being some of them.
>>
>> Well, it's relevant to conventional airplanes in an indirect sort of
>> way, which is my point. If you truly understand the principles
>> involved, you then thoroughly understand enough to trim your
>> homebuilt. My own airplane is notorious for needing stab adjustments
>> after the first flight. A real PITA since the stab is welded into
>> position ( I plan to make mine adjustable with shims) Now, the stab
>> on my airplane has a negative incidence, while the top wing is set at
>> zero and the bottom is set at plus 2 degrees. Doesn't seem to add up,
>> does it? The stab is flat plate, BTW. So, waht's all that about?
>>
>> Bertie
>
> I hear a candiate screamin for the Darwin Awards.
> Leave flying to us pro's, you stay in outhouse.



Yeah, how have I cheated the odds so long? I must be the luckiest
******* aloive to have been flying 2 and a half years without killing
myself.


Bertie

[Morgans[_2_]]

"Bertie the Bunyip" > wrote

> Well, it's relevant to conventional airplanes in an indirect sort of way,
> which is my point. If you truly understand the principles involved, you
> then thoroughly understand enough to trim your homebuilt. My own airplane
> is notorious for needing stab adjustments after the first flight. A real
> PITA since the stab is welded into position ( I plan to make mine
> adjustable with shims) Now, the stab on my airplane has a negative
> incidence, while the top wing is set at zero and the bottom is set at plus
> 2 degrees. Doesn't seem to add up, does it? The stab is flat plate, BTW.
> So, waht's all that about?

This is a Hartz biplane, as I think I recall? The incidence you describe
sounds like it must have negative stagger, no?

If it were me, I think I would make your stab hinged at the rear, with an
arrangement to move the leading edge up and down for trim, which would take
care of your needing to adjust the incidence.

Do you think that could be adapted to your plane?

I'll have to look that Hartz up, if that is what it is.
--
Jim in NC

[Bertie the Bunyip[_25_]]

"Morgans" > wrote in
:

>
> "Bertie the Bunyip" > wrote
>
>> Well, it's relevant to conventional airplanes in an indirect sort of
>> way, which is my point. If you truly understand the principles
>> involved, you then thoroughly understand enough to trim your
>> homebuilt. My own airplane is notorious for needing stab adjustments
>> after the first flight. A real PITA since the stab is welded into
>> position ( I plan to make mine adjustable with shims) Now, the stab
>> on my airplane has a negative incidence, while the top wing is set at
>> zero and the bottom is set at plus 2 degrees. Doesn't seem to add up,
>> does it? The stab is flat plate, BTW. So, waht's all that about?
>
> This is a Hartz biplane, as I think I recall? The incidence you
> describe
> sounds like it must have negative stagger, no?

Nope, it's a pisitive stagger biplane.
>
> If it were me, I think I would make your stab hinged at the rear, with
> an arrangement to move the leading edge up and down for trim, which
> would take care of your needing to adjust the incidence.

Well, some guys have done this, but I'm not that crazy about the piper
jackscrew system in an airplane that will be turned up side down. The
plan is to have it hinged at the rear as you suggest, and then have a
attachment at the front that's shimmable and get it right that way.
>
> Do you think that could be adapted to your plane?

Yeah, a couple of guys have done that, I think .
>
> I'll have to look that Hartz up, if that is what it is.


www.weebeastie.com


Bertie

[Jim Logajan]

Bertie the Bunyip > wrote:
> wrote in news:1e9f68a1-fd54-4824-9eeb-
> :
>
>> On Feb 4, 3:52 pm, Bertie the Bunyip > wrote:
>>
>>> Just shoot yourself now Dan.
>>>
>>> Bertie
>>
>> Bang.
>>
>> Dan
>>
>
> Better?
>
> Bertie

The above brings to mind the title and lyrics of the song for the movie and
TV series M*A*S*H.

[Bertie the Bunyip[_25_]]

Jim Logajan > wrote in
:

> Bertie the Bunyip > wrote:
>> wrote in news:1e9f68a1-fd54-4824-9eeb-
>> :
>>
>>> On Feb 4, 3:52 pm, Bertie the Bunyip > wrote:
>>>
>>>> Just shoot yourself now Dan.
>>>>
>>>> Bertie
>>>
>>> Bang.
>>>
>>> Dan
>>>
>>
>> Better?
>>
>> Bertie
>
> The above brings to mind the title and lyrics of the song for the
> movie and TV series M*A*S*H.

Heh heh. Wheras Kenny's theme song is "I wanna be sedated"


Bertie

[Morgans[_2_]]

"Bertie the Bunyip" > wrote

> Nope, it's a pisitive stagger biplane.

That's strange. Every positive stagger biplane I have looked at had the top
wing with a couple degrees more incidence than the lower wing. Know why it
is like the opposite?

> Well, some guys have done this, but I'm not that crazy about the piper
> jackscrew system in an airplane that will be turned up side down. The
> plan is to have it hinged at the rear as you suggest, and then have a
> attachment at the front that's shimmable and get it right that way.

You could do it without using a jackscrew, I would think. How about
something like a cam on each side, with a shaft turning a cam on each side,
and a belcrank to turn the shaft. You could limit the range of motion
possible, so that even if something broke, it would be flyable. I
understand not wanting to trust a jackscrew.

It would probably add some complexity and weight, though, but it would be an
advantage for top speed, I would think.

--
Jim in NC

[Bertie the Bunyip[_25_]]

"Morgans" > wrote in
:

>
> "Bertie the Bunyip" > wrote
>
>> Nope, it's a pisitive stagger biplane.
>
> That's strange. Every positive stagger biplane I have looked at had
> the top wing with a couple degrees more incidence than the lower wing.
> Know why it is like the opposite?


Nope, almost never, in fact. The reason being that the bottom wing's
flow is affected by the top's. I'm guessing you thought they had the top
wing at a higher incidence probably because you heard that the top wing
should stall first to ensure a stable stall, which is patly true, but
that doesn't factor in the airflow in the "slot" between the wings,
which effectively lowers the angle of attack of the lower wing even
though it's incidence is higher than the top. Likewise the stab is
affected, and though a negative angle of attack is required for
stability, the airflow around the tail is affected by the wings and a
bit of down stabiliser is called for. Most guys find that the incidence
on the plans isn't enough, in fact.

>
>> Well, some guys have done this, but I'm not that crazy about the
>> piper jackscrew system in an airplane that will be turned up side
>> down. The plan is to have it hinged at the rear as you suggest, and
>> then have a attachment at the front that's shimmable and get it right
>> that way.
>
> You could do it without using a jackscrew, I would think. How about
> something like a cam on each side, with a shaft turning a cam on each
> side, and a belcrank to turn the shaft. You could limit the range of
> motion possible, so that even if something broke, it would be flyable.
> I understand not wanting to trust a jackscrew.
>
> It would probably add some complexity and weight, though, but it would
> be an advantage for top speed, I would think.


What 86 instead of 85? Nah, weight is all impertant in this airplnae
since the power will be low. Also simplicity. The bits for the
adjustable incidence are already in place, anyway.. Never head of a cam
system before. Should work ok, though, once no slop was allowed.
In any case this is a traditional airplane using all traditional
materials. The only concessions to modernity I can think of are the disc
brakes and the nylon rags. Aside from that, it's a 1930 airplane in
every way.


Bertie
>

[Big John[_2_]]

On Mon, 4 Feb 2008 18:06:56 -0800 (PST), "Ken S. Tucker"
> wrote:

>On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
>> "Morgans" > wrote :
>>
>>
>>
>>
>>
>> > "Bertie the Bunyip" > wrote
>>
>> >> well, it must be at least a bit interesting for an experimenter. The
>> >> rocket
>> >> man posted som salient stuff there and understanding the relationship
>> >> between CG and the aerodynamic center is a very useful thing for a
>> >> builder.
>> >> Not strictly neccesary, of course, but definitely nice to know. Less
>> >> so for
>> >> a pilot...
>>
>> > I feel I have a good grip on the relationship between CG an AC for
>> > conventional planforms. I have no interest in canards or tandem
>> > lifting wings.
>>
>> > I did pay a bit more attention to a few of the posts, though, and his
>> > being some of them.
>>
>> Well, it's relevant to conventional airplanes in an indirect sort of way,
>> which is my point. If you truly understand the principles involved, you
>> then thoroughly understand enough to trim your homebuilt. My own airplane
>> is notorious for needing stab adjustments after the first flight. A real
>> PITA since the stab is welded into position ( I plan to make mine
>> adjustable with shims) Now, the stab on my airplane has a negative
>> incidence, while the top wing is set at zero and the bottom is set at plus
>> 2 degrees. Doesn't seem to add up, does it? The stab is flat plate, BTW.
>> So, waht's all that about?
>>
>> Bertie
>
>I hear a candiate screamin for the Darwin Awards.
>Leave flying to us pro's, you stay in outhouse.
>......


*****************************************

Lets throw the D-17 in the discussion and why it was so fast in it's
time frame.

Big John

[Blueskies]

"Bertie the Bunyip" > wrote in message ...
>
>
> Well, it's relevant to conventional airplanes in an indirect sort of way,
> which is my point. If you truly understand the principles involved, you
> then thoroughly understand enough to trim your homebuilt. My own airplane
> is notorious for needing stab adjustments after the first flight. A real
> PITA since the stab is welded into position ( I plan to make mine
> adjustable with shims) Now, the stab on my airplane has a negative
> incidence, while the top wing is set at zero and the bottom is set at plus
> 2 degrees. Doesn't seem to add up, does it? The stab is flat plate, BTW.
> So, waht's all that about?
>
>
>
> Bertie

Probably the incidences are set up that way to reduce roll couple in knife edge, an attempt to keep each axis separate
from the others...

[Phil J]

On Feb 5, 5:53*pm, Big John > wrote:

>
> Lets throw the D-17 in the discussion and why it was so fast in it's
> time frame.
>
> Big John

Based on what I learned over in the Why Airplanes Fly thread, I guess
it cost a lot of money!

Phil

[Bertie the Bunyip[_25_]]

"Blueskies" > wrote in
t:

> "Bertie the Bunyip" > wrote in message
> ...
>>
>>
>> Well, it's relevant to conventional airplanes in an indirect sort of
>> way, which is my point. If you truly understand the principles
>> involved, you then thoroughly understand enough to trim your
>> homebuilt. My own airplane is notorious for needing stab adjustments
>> after the first flight. A real PITA since the stab is welded into
>> position ( I plan to make mine adjustable with shims) Now, the stab
>> on my airplane has a negative incidence, while the top wing is set at
>> zero and the bottom is set at plus 2 degrees. Doesn't seem to add up,
>> does it? The stab is flat plate, BTW. So, waht's all that about?
>>
>>
>>
>> Bertie
>
> Probably the incidences are set up that way to reduce roll couple in
> knife edge, an attempt to keep each axis separate from the others...
>
>
>
Nope. It's beacuse the flow from the fairly large wings on thei relatively
short coupled airplane is flowing down at a significant angle when it
reaches the tail.


Bertie

[Bertie the Bunyip[_24_]]

Big John > wrote in
:

> On Mon, 4 Feb 2008 18:06:56 -0800 (PST), "Ken S. Tucker"
> > wrote:
>
>>On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
>>> "Morgans" > wrote
>>> :
>>>
>>>
>>>
>>>
>>>
>>> > "Bertie the Bunyip" > wrote
>>>
>>> >> well, it must be at least a bit interesting for an experimenter.
>>> >> The rocket
>>> >> man posted som salient stuff there and understanding the
>>> >> relationship between CG and the aerodynamic center is a very
>>> >> useful thing for a builder.
>>> >> Not strictly neccesary, of course, but definitely nice to know.
>>> >> Less so for
>>> >> a pilot...
>>>
>>> > I feel I have a good grip on the relationship between CG an AC
>>> > for
>>> > conventional planforms. I have no interest in canards or tandem
>>> > lifting wings.
>>>
>>> > I did pay a bit more attention to a few of the posts, though, and
>>> > his being some of them.
>>>
>>> Well, it's relevant to conventional airplanes in an indirect sort of
>>> way, which is my point. If you truly understand the principles
>>> involved, you then thoroughly understand enough to trim your
>>> homebuilt. My own airplane is notorious for needing stab adjustments
>>> after the first flight. A real PITA since the stab is welded into
>>> position ( I plan to make mine adjustable with shims) Now, the stab
>>> on my airplane has a negative incidence, while the top wing is set
>>> at zero and the bottom is set at plus 2 degrees. Doesn't seem to add
>>> up, does it? The stab is flat plate, BTW. So, waht's all that about?
>>>
>>> Bertie
>>
>>I hear a candiate screamin for the Darwin Awards.
>>Leave flying to us pro's, you stay in outhouse.
>>......
>
>
> *****************************************
>
> Lets throw the D-17 in the discussion and why it was so fast in it's
> time frame.

Ponies!


Actually I thnk it had more to do with the careful attention to the
fillets and a relatively small frontal area on the fuse. Probably used a
fairly thin wing section as well.


They just got it all right with that one, didn't they?


Bertie

[Big John[_2_]]

On Wed, 6 Feb 2008 06:02:58 +0000 (UTC), Bertie the Bunyip >
wrote:

>Big John > wrote in
:
>
>> On Mon, 4 Feb 2008 18:06:56 -0800 (PST), "Ken S. Tucker"
>> > wrote:
>>
>>>On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
>>>> "Morgans" > wrote
>>>> :
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> > "Bertie the Bunyip" > wrote
>>>>
>>>> >> well, it must be at least a bit interesting for an experimenter.
>>>> >> The rocket
>>>> >> man posted som salient stuff there and understanding the
>>>> >> relationship between CG and the aerodynamic center is a very
>>>> >> useful thing for a builder.
>>>> >> Not strictly neccesary, of course, but definitely nice to know.
>>>> >> Less so for
>>>> >> a pilot...
>>>>
>>>> > I feel I have a good grip on the relationship between CG an AC
>>>> > for
>>>> > conventional planforms. I have no interest in canards or tandem
>>>> > lifting wings.
>>>>
>>>> > I did pay a bit more attention to a few of the posts, though, and
>>>> > his being some of them.
>>>>
>>>> Well, it's relevant to conventional airplanes in an indirect sort of
>>>> way, which is my point. If you truly understand the principles
>>>> involved, you then thoroughly understand enough to trim your
>>>> homebuilt. My own airplane is notorious for needing stab adjustments
>>>> after the first flight. A real PITA since the stab is welded into
>>>> position ( I plan to make mine adjustable with shims) Now, the stab
>>>> on my airplane has a negative incidence, while the top wing is set
>>>> at zero and the bottom is set at plus 2 degrees. Doesn't seem to add
>>>> up, does it? The stab is flat plate, BTW. So, waht's all that about?
>>>>
>>>> Bertie
>>>
>>>I hear a candiate screamin for the Darwin Awards.
>>>Leave flying to us pro's, you stay in outhouse.
>>>......
>>
>>
>> *****************************************
>>
>> Lets throw the D-17 in the discussion and why it was so fast in it's
>> time frame.
>
>Ponies!
>
>
>Actually I thnk it had more to do with the careful attention to the
>fillets and a relatively small frontal area on the fuse. Probably used a
>fairly thin wing section as well.
>
>
>They just got it all right with that one, didn't they?
>
>
>Bertie


************************************************** **************
Bertie

Thought someone would talk about the negative stagger and inter action
between the two wings and rigging, etc :o)

Almost bought one, one time. Had a friend who did buy a run out one
and had overhauled and recovered in Panama when we were stationed
there. There was a shop who did a excellent job for bottom dollar
price. It took them about 6 months to do between other jobs to keep
price down. Can't find those economical places any more even over
seas.

Big John

[Bertie the Bunyip]

On Feb 6, 10:07*pm, Big John > wrote:
> On Wed, 6 Feb 2008 06:02:58 +0000 (UTC), Bertie the Bunyip >
> wrote:
>
>
>
>
>
> >Big John > wrote in
> :
>
> >> On Mon, 4 Feb 2008 18:06:56 -0800 (PST), "Ken S. Tucker"
> >> > wrote:
>
> >>>On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
> >>>> "Morgans" > wrote
> >>>> :
>
> >>>> > "Bertie the Bunyip" > wrote
>
> >>>> >> well, it must be at least a bit interesting for an experimenter.
> >>>> >> The rocket
> >>>> >> man posted som salient stuff there and understanding the
> >>>> >> relationship between CG and the aerodynamic center is a very
> >>>> >> useful thing for a builder.
> >>>> >> Not strictly neccesary, of course, but definitely nice to know.
> >>>> >> Less so for
> >>>> >> a pilot...
>
> >>>> > *I feel I have a good grip on the relationship between CG an AC
> >>>> > *for
> >>>> > conventional planforms. *I have no interest in canards or tandem
> >>>> > lifting wings.
>
> >>>> > I did pay a bit more attention to a few of the posts, though, and
> >>>> > his being some of them.
>
> >>>> Well, it's relevant to conventional airplanes in an indirect sort of
> >>>> way, which is my point. If you truly understand the principles
> >>>> involved, you then thoroughly understand enough to trim your
> >>>> homebuilt. My own airplane is notorious for needing stab adjustments
> >>>> after the first flight. A real PITA since the stab is welded into
> >>>> position ( I plan to make mine adjustable with shims) Now, the stab
> >>>> on my airplane has a negative incidence, while the top wing is set
> >>>> at zero and the bottom is set at plus 2 degrees. Doesn't seem to add
> >>>> up, does it? The stab is flat plate, BTW. So, waht's all that about?
>
> >>>> Bertie
>
> >>>I hear a candiate screamin for the Darwin Awards.
> >>>Leave flying to us pro's, you stay in outhouse.
> >>>......
>
> >> *****************************************
>
> >> Lets throw the D-17 in the discussion and why it was so fast in it's
> >> time frame.
>
> >Ponies!
>
> >Actually I thnk it had more to do with the careful attention to the
> >fillets and a relatively small frontal area on the fuse. Probably used a
> >fairly thin wing section as well.
>
> >They just got it all right with that one, didn't they?
>
> >Bertie
>
> ************************************************** **************
> Bertie
>
> Thought someone would talk about the negative stagger and inter action
> between the two wings and rigging, etc *:o)

I would if I knew! You'd have to ask someone with a lot more knowledge
than me for a definitive answer. My own view is that like all
airplanes ever built it was a case of comprimise and integration. The
deisrability of a stagger and the slightly better negative stagger
configuration ( for drag, if not lift) went nicely hand in hand with
the desire to increase, if only slightly, in flight visibility ( over
say, a Waco UIC) and tied in well with the wing mounted gear which
allowed a relatively simple retract system. It was simply a well
thought out airplnae which balanced the pros and cons of each element
of the configuration and brougth them all together into one slick
machine. I'm struggling to think of something comparable that did it
quite so beautifully. Having siad that, if you put that and a WACO SRE
in front of me, I think I'd choose the WACO>

>
> Almost bought one, one time. Had a friend who did buy a run out one
> and had overhauled and recovered in Panama when we were stationed
> there. There was a shop who did a excellent job for bottom dollar
> price. It took them about 6 months to do between other jobs to keep
> price down. * Can't find those economical places any more even over
> seas.

Nice. Kicking yourself now, eh? A friend of mine bought a project B17
with the Jake in it and gave up on it after a few years and sold it. I
was really hoping to get to fly it!

Bertie

[Big John[_2_]]

On Thu, 7 Feb 2008 14:41:38 -0800 (PST), Bertie the Bunyip
> wrote:

>On Feb 6, 10:07*pm, Big John > wrote:
>> On Wed, 6 Feb 2008 06:02:58 +0000 (UTC), Bertie the Bunyip >
>> wrote:
>>
>>
>>
>>
>>
>> >Big John > wrote in
>> :
>>
>> >> On Mon, 4 Feb 2008 18:06:56 -0800 (PST), "Ken S. Tucker"
>> >> > wrote:
>>
>> >>>On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
>> >>>> "Morgans" > wrote
>> >>>> :
>>
>> >>>> > "Bertie the Bunyip" > wrote
>>
>> >>>> >> well, it must be at least a bit interesting for an experimenter.
>> >>>> >> The rocket
>> >>>> >> man posted som salient stuff there and understanding the
>> >>>> >> relationship between CG and the aerodynamic center is a very
>> >>>> >> useful thing for a builder.
>> >>>> >> Not strictly neccesary, of course, but definitely nice to know.
>> >>>> >> Less so for
>> >>>> >> a pilot...
>>
>> >>>> > *I feel I have a good grip on the relationship between CG an AC
>> >>>> > *for
>> >>>> > conventional planforms. *I have no interest in canards or tandem
>> >>>> > lifting wings.
>>
>> >>>> > I did pay a bit more attention to a few of the posts, though, and
>> >>>> > his being some of them.
>>
>> >>>> Well, it's relevant to conventional airplanes in an indirect sort of
>> >>>> way, which is my point. If you truly understand the principles
>> >>>> involved, you then thoroughly understand enough to trim your
>> >>>> homebuilt. My own airplane is notorious for needing stab adjustments
>> >>>> after the first flight. A real PITA since the stab is welded into
>> >>>> position ( I plan to make mine adjustable with shims) Now, the stab
>> >>>> on my airplane has a negative incidence, while the top wing is set
>> >>>> at zero and the bottom is set at plus 2 degrees. Doesn't seem to add
>> >>>> up, does it? The stab is flat plate, BTW. So, waht's all that about?
>>
>> >>>> Bertie
>>
>> >>>I hear a candiate screamin for the Darwin Awards.
>> >>>Leave flying to us pro's, you stay in outhouse.
>> >>>......
>>
>> >> *****************************************
>>
>> >> Lets throw the D-17 in the discussion and why it was so fast in it's
>> >> time frame.
>>
>> >Ponies!
>>
>> >Actually I thnk it had more to do with the careful attention to the
>> >fillets and a relatively small frontal area on the fuse. Probably used a
>> >fairly thin wing section as well.
>>
>> >They just got it all right with that one, didn't they?
>>
>> >Bertie
>>
>> ************************************************** **************
>> Bertie
>>
>> Thought someone would talk about the negative stagger and inter action
>> between the two wings and rigging, etc *:o)
>
>I would if I knew! You'd have to ask someone with a lot more knowledge
>than me for a definitive answer. My own view is that like all
>airplanes ever built it was a case of comprimise and integration. The
>deisrability of a stagger and the slightly better negative stagger
>configuration ( for drag, if not lift) went nicely hand in hand with
>the desire to increase, if only slightly, in flight visibility ( over
>say, a Waco UIC) and tied in well with the wing mounted gear which
>allowed a relatively simple retract system. It was simply a well
>thought out airplnae which balanced the pros and cons of each element
>of the configuration and brougth them all together into one slick
>machine. I'm struggling to think of something comparable that did it
>quite so beautifully. Having siad that, if you put that and a WACO SRE
>in front of me, I think I'd choose the WACO>
>
>>
>> Almost bought one, one time. Had a friend who did buy a run out one
>> and had overhauled and recovered in Panama when we were stationed
>> there. There was a shop who did a excellent job for bottom dollar
>> price. It took them about 6 months to do between other jobs to keep
>> price down. * Can't find those economical places any more even over
>> seas.
>
>Nice. Kicking yourself now, eh? A friend of mine bought a project B17
>with the Jake in it and gave up on it after a few years and sold it. I
>was really hoping to get to fly it!
>
>Bertie
************************************************** *************************

You don't have to rub it in :o(

It takes a PILOT to fly one with it's take off and landing
characteristics. Not a beginners aircraft. The WACO
would be a more comfortable and relaxing bird to fly I'm
sure but wouldn't attract the crowd of gawkers when you
landed at a GA airport :o).

Big John

[Bertie the Bunyip[_24_]]

Big John > wrote in
:

> On Thu, 7 Feb 2008 14:41:38 -0800 (PST), Bertie the Bunyip
> > wrote:
>
>>On Feb 6, 10:07*pm, Big John > wrote:
>>> On Wed, 6 Feb 2008 06:02:58 +0000 (UTC), Bertie the Bunyip
>>> > wrote:
>>>
>>>
>>>
>>>
>>>
>>> >Big John > wrote in
>>> :
>>>
>>> >> On Mon, 4 Feb 2008 18:06:56 -0800 (PST), "Ken S. Tucker"
>>> >> > wrote:
>>>
>>> >>>On Feb 4, 4:39 pm, Bertie the Bunyip > wrote:
>>> >>>> "Morgans" > wrote
>>> >>>> :
>>>
>>> >>>> > "Bertie the Bunyip" > wrote
>>>
>>> >>>> >> well, it must be at least a bit interesting for an
>>> >>>> >> experimenter. The rocket
>>> >>>> >> man posted som salient stuff there and understanding the
>>> >>>> >> relationship between CG and the aerodynamic center is a very
>>> >>>> >> useful thing for a builder.
>>> >>>> >> Not strictly neccesary, of course, but definitely nice to
>>> >>>> >> know. Less so for
>>> >>>> >> a pilot...
>>>
>>> >>>> > *I feel I have a good grip on the relationship between CG an
>>> >>>> > AC *for
>>> >>>> > conventional planforms. *I have no interest in canards or
>>> >>>> > tandem lifting wings.
>>>
>>> >>>> > I did pay a bit more attention to a few of the posts, though,
>>> >>>> > and his being some of them.
>>>
>>> >>>> Well, it's relevant to conventional airplanes in an indirect
>>> >>>> sort of way, which is my point. If you truly understand the
>>> >>>> principles involved, you then thoroughly understand enough to
>>> >>>> trim your homebuilt. My own airplane is notorious for needing
>>> >>>> stab adjustments after the first flight. A real PITA since the
>>> >>>> stab is welded into position ( I plan to make mine adjustable
>>> >>>> with shims) Now, the stab on my airplane has a negative
>>> >>>> incidence, while the top wing is set at zero and the bottom is
>>> >>>> set at plus 2 degrees. Doesn't seem to add up, does it? The
>>> >>>> stab is flat plate, BTW. So, waht's all that about?
>>>
>>> >>>> Bertie
>>>
>>> >>>I hear a candiate screamin for the Darwin Awards.
>>> >>>Leave flying to us pro's, you stay in outhouse.
>>> >>>......
>>>
>>> >> *****************************************
>>>
>>> >> Lets throw the D-17 in the discussion and why it was so fast in
>>> >> it's time frame.
>>>
>>> >Ponies!
>>>
>>> >Actually I thnk it had more to do with the careful attention to the
>>> >fillets and a relatively small frontal area on the fuse. Probably
>>> >used a fairly thin wing section as well.
>>>
>>> >They just got it all right with that one, didn't they?
>>>
>>> >Bertie
>>>
>>> ************************************************** **************
>>> Bertie
>>>
>>> Thought someone would talk about the negative stagger and inter
>>> action between the two wings and rigging, etc *:o)
>>
>>I would if I knew! You'd have to ask someone with a lot more knowledge
>>than me for a definitive answer. My own view is that like all
>>airplanes ever built it was a case of comprimise and integration. The
>>deisrability of a stagger and the slightly better negative stagger
>>configuration ( for drag, if not lift) went nicely hand in hand with
>>the desire to increase, if only slightly, in flight visibility ( over
>>say, a Waco UIC) and tied in well with the wing mounted gear which
>>allowed a relatively simple retract system. It was simply a well
>>thought out airplnae which balanced the pros and cons of each element
>>of the configuration and brougth them all together into one slick
>>machine. I'm struggling to think of something comparable that did it
>>quite so beautifully. Having siad that, if you put that and a WACO SRE
>>in front of me, I think I'd choose the WACO>
>>
>>>
>>> Almost bought one, one time. Had a friend who did buy a run out one
>>> and had overhauled and recovered in Panama when we were stationed
>>> there. There was a shop who did a excellent job for bottom dollar
>>> price. It took them about 6 months to do between other jobs to keep
>>> price down. * Can't find those economical places any more even over
>>> seas.
>>
>>Nice. Kicking yourself now, eh? A friend of mine bought a project B17
>>with the Jake in it and gave up on it after a few years and sold it. I
>>was really hoping to get to fly it!
>>
>>Bertie
> ************************************************** ********************
*
> ****
>
> You don't have to rub it in :o(
>
> It takes a PILOT to fly one with it's take off and landing
> characteristics. Not a beginners aircraft. The WACO
> would be a more comfortable and relaxing bird to fly I'm
> sure but wouldn't attract the crowd of gawkers when you
> landed at a GA airport :o).
>

I think I could manage a 17 OK, It's the performance of the WACO I'd
prefer, I think ( runway and climb) And I prefer it's looks. Having said
that it;s like choosing between two supermodels..


Bertie