Is there any aerospace engineer out there who can tell me the difference between a canard and a foreplane?

Thanks!

Not an aerospace engineer... but:

They are virtually interchangeable terms. when referring to the front wing on a airplane that has the main lifting surface to the rear and te horizontal stabilizer in front.

The term "Canard" actually refers to the whole aircraft, but is often used to refer to the horizontal stab on a Canard design. It means litereally "duck" in French... and was a descriptive of the apearance of one airplane in flight overhead. ("That looks like a duck"... someone who knows French translate completely... and you got what the guy said. The name stuck.)

Foreplane can also refer to the front wing in a design such as the "Quickie" where you get about equal lift from the front wing and the rear wing. (its an odd looking airplane... doesn't really fit the definition of a Canard.) There are about 4 or 5 model designs of this nature... only one full scale I have seen.

Having designed aircraft models using both, it's my understanding that these are not interchangeable terms...

An aircraft which uses the forward surface to control pitch is using a canard. (i.e., the Long EZ)

An aircraft such as the Piaggio "Avanti" is a 3-lifting-surface design, and the front surface, (the foreplane ) is not used for pitch control, but rather as a balancing force, allowing the wing area (and thus drag) to be reduced. It has slotted flaps, and uses them only for takeoff and landing.) As a bonus, this allows the horizontal stab (an inverted airfoil) to fly at almost zero lift in cruise. (again, reducing drag)

Practical effects in modeling are:

A canard aircraft has to be built in such a way that the canard is effective, and this means that the canard chord should not be below about 4.5 inches, to be effective. As a scale enthusiast, it follows that to build a scale canard design, you need to build it large. (Even at 1/3rd scale, the canard on a scale Long EZ is only about 4.25" chord ! )

A 3-lifting-surface design, such as the "Avanti" can get around this requirement, if built carefully, because the horizontal stabilizer/elevator still controls the pitch.

Of course, there are other canard configurations, such as the jet "Eurofighter", "Rafale", and others, but in those cases, the flight control system is integrated anyway, and I believe that the elevons also play a part in pitch control.

So what I have seen as common useage... is further from the technical terms than I thought...

****

BTW... using the above definition...

Can you replicate a Canard design, on a scale where the "canard surface" is ineffective (under 4.5 inches), shift the balance a bit (so it flys) and have a flying wing with a foreplane? Or is it a Canard still... with a foreplane instead of a Canard surface?

HI FH HUBER! First of all, the literal translation of foreplane means an aerodynamic surface in front of something, we will guess the wing is meant to be THAT something, so I'm with you about the terms being interchangeable. I recently built a 1/2A canard with a "rudimentary appendage" hanging off the front that I tried to use for pitch control. In order to acheive a certain futuristic fighter look, I made the forplanes 3" by 6" for each half, with a taper towards the tips. I gave the surfaces a lifting airfoil, and hinged it at 25% of the cord. To make a long story short, it didn't work very well. It was very unresponsive when I tried to set the CG forward[like you would for a classic canard design], and when I tried moving the CG back it became too sensitive. I never found a sweet spot.. I'm with you again about canards , and going below the magic number for getting some lift out of it. I'm sure you could go smaller than 4.5" IF the wing loading was low enough. Anyway, I sliced off the foreplanes and ended up with a good flying ZAGI type thing with an .049.

My last was a trick question... I've done it. It can be made to fly.

I experimented around a LOT in the late 1970s ( aLOT of people did...) trying to make a sorta-scale X-wing fighter. I did mine in control line and it would fly nice straight and level... however its "turn" radius was abysmal... so no loops.

Wish I still had a copy of my plans of it... may have to go through it again and make one for RC. (new problem of Yaw stability will be a #$%^& Those lines really helped there.)

A lot of things can be made to fly, but that's not a good "canard" design.

A properly set up canard aircraft will have a wider CG range than the equivalent "normal" plane. That's one of the advantages of the type.

The above mentioned control line canard aircraft is an example. The lousy "turn radius" mentioned indicates a lack of canard elevator authority.

So far, all of the canard design aircraft that I've seen [that supposedly flew well enough to become published plans], in the .15 size and under range were fairly ugly looking tandem wing type things. By the time my 1/2As' tiny canard was deflected enough to cause a change in pitch, it was also acting like an air brake. Being close coupled to the CG didn't help either. The dream of a cool looking, compact futuristic fighter went down the tubes until I "circumsized the foreplane"!

No doubt someone will correct me if I am wrong...

The maneuverability of a canard must (I think) be directly a function of the ability of the foreplanes to carry a wide range of loads....

So if I give up elevator, the effect is to try and shift the cg around the centre of lift (MAC I think would be more correct. This means that the lift being generated by the foreplanes must be increased.

In the instance given by Combattpigg obviously the foreplanes that he was working with could not generate that increased lift so, in his words they became more airbrake than control surface.

The two rules that I have been given (from many years back) are -

The foreplane must not stall before the mainplane

The foreplane must be capable of generating more lift per unit area than the mainplane.

The vector equilibrium for a canard has the foreplanes carrying considerably more ( a greater proportion) of the total lift load than does the tailplane on a conventional aircraft.

For that reason, the conventional thinking about tailplane size and lift has to be seriously abandoned if you are to get a canard to fly.




BTW I think (MHO) the Quickie is a canard.


BTW2 Canard is the aircraft type
Foreplane is the part of the aircraft
But that is just me being pedantic. Does it really matter?

HI PROBLIGO! Thanks very much for the explanation! It is interesting that the foreplane should generate more lift per unit area than the main wing, that's the first time I have heard that mentioned. I will bear that in mind if I ever go back to the drawing board. I guess the easiest way to execute that idea would be to have a flat bottom airfoil on the foreplane, and let's say a semi symetrical foil on the wing. If I had such a wing that was 30" by 9", what would be a good size for the foreplane, and how far forward would you place it? The plane would weigh no more than 13 ounces.

For stability... The foreplane MUST stall before the mainplane... this results in the typical canard "sine-wave" stall pattern. If the mainplane stalls first, the canard COULD go into a tail-first spin, which is virtually unrecoverable.

The foreplane will often have a more efficient airfoil than the mainplane n an attempt to corect for the natural scale effect changing the load carrying capability of a given airfiol at a given speed.
(just as you must have a lighter wing loading on a 20% CAP 32 than what you can carry with a full scale... the foreplane , being smaller than the mainplane, {normally... btw is a Quickie a Canard?} is somewhat less efficient at making lift)

It is virtually impossible for the foreplane to carry a heavier per square inch load than the mainplane.

Many of the current fighter aircraft in service that have canards are delta wing aircraft. Those of you familiar with this type of lifting body knows that this type of configuration is not as stable as a more convention setup (ie--it loses a lot of speed in tight turns). The Eurofighter is a prime example. However, the maneuverability of this craft is exceptional due inpart to using canards in conjunction with elevons and possibly force vectoring nozzles. Delta and canard fighters have non linear control. Meaning the control curve is smooth until you reach a certain point and then it jumps rather drastically. I may have used some terms incorrectly, but I think you get the idea.

[sm=spinnyeyes.gif]Errr FH, I said that????

You are absolutely right - that is why my ff canard has the foreplane at +7* and the wing a 0*

To the world at large - sorry. Take out the "not" and it makes sense.

From a "lively" discussion on canards, full-scale and models, on the 'net...
"For your application, been there, done that. Use a conventional layout. At model plane
Reynolds numbers, don't have the smallest surface working the hardest,
as will be the case with a canard. All else equal, a bad idea."
.
And as I've mentioned, the fragile end gets to the crash site first!

I found... on models, especially smaller canards, that you want the Canard at +1 to +3 vs the mainplane when trimmed for level flight. This has the plane balanced a bit further back than the larger decalage. The foreplane then has a bit more authority to change pitch for maneuvering. The forplane actually has a chace to pitch the nose up enough to loop, rather than stalling out of every attempt.

If the foreplane is +7 to the mainplane... since the mainplane will tend to be at +3 AOA for level cruise. (most of the models I have done anyway) then the foreplane would be cruising at +10, which is already near stall in some cases. Put a bit of downward deflection on the canard control surface (up elevator function)... and it stalls the foreplane "right quick."

Paul may be right.

Caution, everybody reading this thread. There is a bunch of bad information here, along with some true information. I refer everyone seriously interested in getting these configurations to work right to read all the tested and proven data in Andy Lennon's book, "The Basics of RC Model Aircraft Design". (available through Model Airplane News - http://www.rcstore.com/rs/general/li...id=8&catego=BO I always suggest Andy's book, because his numbers work, and this one book can give you a good understanding of the proper configuration for many types of aircraft that all fly well. Your airplanes can look any way you like, but the aerodynamics and balancing considerations cannot be ignored. Air molecules have not changed, along with modern technology, so although new ideas are great, it doesn't mean you can completely ignore or re-write known aerodynamics. ...And, as modelers, we're a little more handicapped, due to the effects of Reynolds numbers.

• It certainly is possible, and typical, with canard aircraft, that the canard will have a higher loading per unit area than the wing. It's simply because the canard is sharing the lift, and for those of us who have built large canard and foreplane-equipped planes, it's a known fact.

• Many modelers have built small parkflyer-size canard aircraft, and claimed that they flew well, violating some known canard configuration data. I haven't seen any that really do. There is some video going around of a nice electric-powered scale canard aircraft in which the builder says he "likes the way it flies", (I won't mention him, because I like his work, regardless) but during the entire flight, the aircraft is oscillating in the normal canard stall/recovery pattern. It's not performing well, and is stalled at least 50 percent of the time. These crazy concepts with high thrust angles and extreme surface incidences are NOT the answer. What you end up with is a draggy, sluggish, airplane that destroys the whole concept of the canard, which was to reduce drag by sharing the lift and enabling a reduction of the main wing area.

• It is a fact that canard aircraft intended to fly with authority (that is, not "flitty", or "scary" ) need to be set up properly, and somewhat more carefully than a conventional layout. That means that Reynolds numbers cannot be ignored, and to work right, the canard needs a chord over approximately 4.5 inches. (Bigger is better) The canard is providing lift, not just balancing the wing with a download. There is plenty of published data on the airfoils you need, (in Andy Lennon's book, in NACA reports, and in the results of flying tests by those of us who have built them) to find what you need. It just takes a little more homework than your typical sport plane. Once set up properly, the are a joy to fly, and often quite fast.

• If you research those canard-equipped models that work well, you'll see that all these things apply. I specifically have experience with the Berkut/Long EZ at 33% scale, as well as a Piaggio "Avanti" at 1/6th scale, and have built non-scale canard aircraft based on Andy Lennon's notes. When rigged properly, a canard aircraft will have a wider CG range, and good elevator response right up to the stall. Dick Rutan does aerobatics in his Long EZ, for example.

• Airfoils matter a lot with these ships. As one example:
I built a 33% scale Berkut-Long EZ ( http://homepage.mac.com/mikejames/rc.../berkut01.html ) As expected, the scale canard, with the scale "slotted flap"-type configuration, was completely ineffective, and the plane would not rotate. A scale-size canard with an enlarged elevator got the plane flying, but it was struggling to maintain level flight at full power. A "Clark Y", with the chord increased 1 inch (to about 5 inches) was substitued for the scale airfoil, with little improvement. Finally, when the canard airfoil was switched to an Eppler 197, the plane transformed from a "dog" to a "beauty". It had good elevator authority even in the deadstick mode. When you're doing canard aircraft, details matter more than a conventional layout.

Short version of the canard story...

At typical model sizes and Reynolds numbers, they don't work too well. So if you want to build one that really flies nice, build them large. And, when you want reliable answers, be sure and check your information against a known source. (i.e., Andy Lennon, NACA, whatever) Any time you have a public forum, you're going to have people who jump in with their opinions, and that's fine... But it doesn't make them right. "Get a second opinion."

.

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Key to a TINY "canard"... (so you don't have the dog) Since the foreplane is not efficient... the CG range is near nothing.. gotta be DEAD ON.

Its backward to the larger ones, because of that 4.5 inch rule.

You do lose maneuverability. (which will turn a lot of people off from wanting to mess with it)

But it sure does look neat.[8D] And sometimes... thats the whole point... get the neat looking thing to fly in a reasonably controlled manner.

Greetings!

Have anyone tested TurnKeyRC's XP-55 (http://www.turnkeyrc.com/), Chris Golds' Shinden or Stengele's Lockspeiser LDA-1? I'm contemplating designing a canard - probably a freelance could be stand way off scale transport style plane - and I would like to make it as small as possible, but not smaller. I've read Andy Lennon (and Martin Simons, Stinton, ...) a few times so I have some idea about what to do and not to do .

I guess that free flight canards can get away with having a almost stalled canard - no fiddling with the controls during flight .

Soft landings.

I ran across a very good reason to not use canards for much of anything while researching this stuff..
Something like this:
"A canard makes good sense when you have a munition to deliver, and want to steer it while it falls. Fitting the munition and steering surfaces into existing weapon's bays almost demands something with no extra structure which can be fit the bay as it is. Two ways to do this are have a folding wing/tail assembly, or spring-loaded pop-out fins at the front and back as seen on "smart bombs" such as the GBU-10. The front fins control the glide path, and permit the standard bomb to fit in existing bomb bays on fighters.
Folding wings are used more for munitions which cruise levelly to the target area rather than are guided along what is essentially a ballistic path (Tomahawk, ALCM, etc). For anything else, a conventional configuration does the same job simpler and cheaper."
.
but canards ARE neat, different, and "entertaining" trying to get them to work.
As long as the limitations are recognized, there's no reason to not play with them.

Canard is the French word for "duck." The term canard was not meant to refer to any particular structure of the aircraft. It was originally used to describe the long neck, duck-like look of an airplane with a small lifting surface in front of the main wings. So I would think that foreplane would be the more accurate term to describe a lifting surface that is in front.

This is my Sig Tristar with OS .25fp. It has a flat-plate airfoil foreplane with a chord that measures 5" at the root and 3" at the tip and about 3 degrees incidence (too much incidence in my opinion). It loops in about 10 feet and is very aerobatic. It even does a nice flat spin that recovers immediately after I let go of the sticks. It's ability to flatspin really surprised me since it doesn't have rudder control.

Hi ya'll,
Allthis input about canards reminds me of the experimenting and developing I did several
years ago, Bottom line was a canard that exhibited superior performance to a similiar airplane.
Only one unusual problem was encountered during developement and that was cured by
increases foreplane chord size.
If you would like to see a most successful in all respects canard craft would suggest you make
the effort to review the report and plans for the "Kanardeze"
It ws in Model Aviation 5/95
Comparison performance flying was done with an excellent similiar airplane and Kanardeze.
Pleased to say the canard performance was better in all respects.
Guys, this style aircraft needs much further looking into and developemnt!
Good luck,

Hal deBolt [email protected]

Geez Craig, ain't you got enough manners not to introduce FACTS into a lively internet discussion? Everybody knows canards are dogs, not ducks!

I sure am glad I didn't know enough way back in '82 and '83 to drop my 2 scratch built canard projects like hot potatoes. I just used the S.W.A.G. method on the 1st one (a 1/2A powered 200 sq. in. jobbie with a 2.5" avg. chord canard surface, 1 deg. in the canard, 0 deg. in wing and thrustline) and 'ol Ronnie Van Putte's formulas on the 2nd .40 powered 575 sq. in. one. Both were pushers and flew very well indeed! Matter of fact, the little one actually won a spot landing contest at a funfly and I got PROTESTED because it wasn't a "REGULAR" airplane....I wuz CHEATIN'!

The 2nd one eventually flew on floats, (very well) won 2nd place in a 29 mile cross-country race (lotsa room on the CG for a big fuel tank!) and went on to 2 other owners and was still flying up until a few years ago. Looking at your Tristar pic, I'm amazed how similar they look. The guy at Sig must not have known what he was doing either!