Hey I just joined today (building a new foam stealth plane from scratch), and I have some questions about CANARD placements / designs...

I know for the canard to have maximum performance, they need to be some distance in front of the wings. (like this one)


I noticed a lot of modern fighter jets have canards on the fuselage beside the intake exhaust ports, rather than near the cockpit.
Could someone please tell me WHY they are placed in this location? Is there some kind of benefit having the canards further away from the main fuselage body?
Could it be because they don't want the disrupted air going into the intake ports?
EXAMPLES:




Also, I noticed some planes have canards (ones on the main fuselage body near the cockpit) either above or below the wing location. I'm assuming this is to avoid the turbulent wind from the canards flowing over the main wings during level flight and positive pitch movement ???
Anyways, I'd appreciate an explanation on this concept as well.
EXAMPLES:




I already know you don't want the disrupted airflow going into the intake ports...

So, any answers to these questions would be greatly appreciated!

I believe the photo you posted earlier w/ the canards further from the wing provide a greater pitch stability which is needed for "general" aviation type planes that dont have fly-by-wire computer systems.
Fighter jets are typically un-stable until you install and fine tune the fly-by-wire system. The in-stability allows for greater manueverability and the shorter distance between the canards and the main wing allow more control authority with less stabillity, which equates to more manueverability.

Okay, so I'm probably going to put canards close to the wings for greater maneuverability on my model.

Because my wings are a diamond shaped (almost exactly) like the YF-23 (not the F-22)...
Should I place the canards a little above the main wings to prevent the broken air from entering the intake ports?


If I finish the sketch of the plane, you might have better ideas to improve the airflow of my plane?

Canards are usually placed so that their downwash disrupts as little as possible. And anything behind them, intakes or wings, can be influenced by either the direction or turbulence of that downflow.

Is it better to have downwash on the top or bottom of the wings (if it cannot be avoided)?
I know zero downwash is best because the airflow is so turbulent from the vortices created by the canards, which disrupts lift on the wings.

Just not sure if I should make horizontal canards on the same level as the wings just in front, or have them angled upwards above the wings (like on the YF-19 and SV-51 [bottom 2 images]).

The reason I want canards is because I will have zero vertical stabilizers / tails, so I'm going to need as much horizontal stabilization, and allow thrust-vectoring control the yaw movement of the plane.
In a sense, the canards will provide some vertical stabilization at very high angles of attack, proving some roll stability ??? [sm=confused.gif]

What do you mean by "vertical stabilization"?

You need yaw, roll, and pitch stability. Only one of those is much affected by canards, unless there is large dihedral or anhedral to them, and then they provide some yaw instability because they're in front, not aft.

You plan to have no vertical surfaces?

It's my understanding that the close spaced canards on things like the Northrop and Soviet 3 views you showed are more for airflow control at extreme angles of attack. In effect the canards act like leading edge slots for the big main body of the aircraft and to some extent aid in pitch control. Note that both those craft use rear pitch control surfaces in conjunction with the canards. Also if you do some more research you'll find writeups on these wide body craft indicating that 50% or more of the lift comes from the body during high speed flight compared to what we consider as the wings.

Some time back I seem to recall a report about an F15 or something actually losing a wing from a mid air collision or anti aircraft fire or something like this and the pilot was able to still fly back and land the plane. Not something you could do unless the fuselage center body was providing a lot of the lift.

Meanwhile you're other canards with props are a more classic form where the forward wing is actually providing some of the lift. It's a whole different use of the surfaces compared to the military styles.

EDIT- If it helps think of the military designs as a very low aspect ratio flying wing with center body airflow control slots rather than being a true canard. Movement of the "canards" in connection with main wing rear surfaces provide more of a camber alteration for pitch control than a true difference in angle of attack changes as seen on more "normal" configuration canards. As such you can't really apply the usual design tools to determine correct center of gravity for them like you can with the more wide spaced "non overlapping" canards where the two wing surfaces are spaced apart by at least a couple of major wing chord lengths.

hI dredogol
Have you built and flown other R/C planes.

No, I have never flown a REAL RC plane yet, nor have I built one yet.
I've only flown the RC Simulation planes.
However, I have tweaked with the mixers and stuff... can do some pretty cool MODs to the existing planes. =D

I know what materials I need, I just want to get a good stable design on paper FIRST, before I spend the money and waste my foam.

Again, I'll post pics of my plane design sketches (paper) when I get it done.

The simulators leave a lot out. Keep that in mind.

You're far better off to start out with conventional designs to avoid any surprises. Learn to fly FIRST then play with unique designs.

Hi dredogol
Learning to fly properly is not the easiest thing in the world. Some people catch on very quickly, others take years before they can consistanly make good landings and are comfortable with the other things. As has been suggested, learn the conventional way. I fly a SPAD canard of my own design and have a ball with it. You can see it at http://www.rcuniverse.com/forum/m_73...tm.htm#7388836

It took me about one year and maybe 50 crashes to learn to fly. This was before trainer cords/radios.

A thought.

Bill

Do you have a reverse crank in that engine or is that not the prop you intend to fly with? Just curious.

That particular engine runs backwards but without reversed crank. Note the position of the carb and front housing.

Bill

The airplane has a number of flights with and without canard. The engine is a .45, airplane weights 8 pounds and take off performance was marginal. The canard added noticeable take off drag. The airplane now has a .50 engine and still needs more reserve during take off. It also appears that dirty air off the wing reduces maximum rpm.

Hi Bills.
Does that mean you are using a standard prop mounted backwards? On my pusher Canards the engine will overheat on the ground. In the air it is OK. I use OS 46FX and AX with a APC 11x6 pusher prop. When I adjust the engine with the two needle valves I replace the pusher prop with an APC 11x6 standard prop. I can then adjust the engine as long as it takes. Then I replace the prop and take off. Could be you are not getting all out of your engine. With your canard wing in place, do you readjust the CG as needed for a canard?

Yes standard prop mounted backwards. The two backwards .45’s that have been flown on the airplane appeared to be sensitive to heat. The .50 with pusher now being flown requires the use of a smaller pusher than tractor prop. Normally I would use a 10 x 8 or 10 x 7 tractor but a 10 x 6 pusher is required for the .50. A 10 x 7 pusher will simply not come up to speed reliably. I suspect a combination of heat and bad air from the wing. There is always the possibility that the APC pusher is not an exact reverse image of the tractor.

I didn’t change the CG but I also did not disconnect the elevator. Control was good while in the air. I damaged the airplane several times before collecting much canard data due to inadequate take off power. Take off seems to be ok now and the canard is off while I master the art of no bounce landing.

Bill

Hi BILLS
Is the plane you pictured the NitroModels Bobcat 50? The specs indicate the weight at 5.5# and your's is 8#. Why? I have always liked that Bobcat 50. Hard to believe it is a $99 ARF. Why so low a price?

The stated weight by NitroModels should not be believed. The finished weight of Bob Cats reported in forum starts about 7 1/2 # and goes up to about 10 #. The manufacturer probably never flew the model. Without engine and radio gear the stated weight would be approximately correct.

Bill

A rather non-aerodynamic reason for the canard placement may also be in play on the full size designs. Moving the canards a it forward would restrict pilot visibility.

In combat, "seeing" your enemy is the first step. Even with modern equipment, there is no real replacement for the Mark I eyeball.

Alright, it's been a while, but I manged to finish the design I was talking about. I present to you the:
YF-24

This is drawn in AutoCAD, so you'll have to excuse the poor render quality.

This is almost the final version of my RC airplane design. Just needs some minor dimension changes, mainly the fuselage size (width).

Summary:
1) ~40 inch wingspan length
3) ~55 inch total length
4) all plane angles based on 40 degree dimension
5) Two 6x4 props
6) 3D Thrust Vector Engines
7) Taileerons move with engine nozzles (up/down Only)
8) Canards and Tailerons allow for PITCH
9) Split aierons and engines allow for YAW control
10) Split ailerons and Tailerons allow for ROLL


So... here's the design concept:

http://fc38.deviantart.com/fs38/f/20...y_Dredogol.jpg


So, what do you guys think?

You are certainly enjoying autocad. Nice work. How soon will you have the plane finished? Have you ordered all of the parts?

I first need the money to get my Remote, Batteries, Chargers, Servos, etc.

When I get the money to get that stuff (like $300), then I can build.

Don't worry, there'll be a video.

Just subscribe to my YouTube account:
http://www.youtube.com/user/dredogol

Before attempting a design without a rudder, make sure to create a chuck glider prototype so you can see if it will even work. Not point in needlessly waste gear on a flawed concept.

Back to your original question, the 'canards' are not really canards, as they are not large enough or far enough forward to be loaded as a tail first type airplane. They are used for maneuvering, as you have guessed, and are there to augment the wing lift by creating a vortex over the wing to maintain an energetic flow of air over the surface so that higher angles of attack can be maintained during high speed, high 'G' flight. What benefit they would be for a model, at the low speeds and loadings that models use, is probably more cosmetic than practical, but if you operate them from a mix, and show everyone what they do, you can probably fool most of the casual observers into thinking that they just gotta have 'em...
Evan, WB #12.