John, You have some interesting ideas there. I would have only a gentle bend for the polyhedral like 10-15 degrees so that the ailerons would be more effective. I tried inboard ailerons on a polyhedral wing and they had no control except when full rudder was applied. This was not on a canard set up. I would need electric power on any future glider. The Captain's glider must really look awesome as it floats along. Charles

Originally Posted by John235

I would use flapperon mixing on the ailerons. When needing to dump some lift for landing the ailerons should go up. The flap mixing function would also mix some down elevator on the canard to maintain pitch equilibrium. I have no idea if it works though.

John,

Just to share a couple different set ups I have tried:

On the J1-31 canard plane I built (the blue / purple plane below), I used mixed elevons / canard flaps that are linked to opposite sides. In other words, the right rear elevon surface is linked to the front left canard flap, and vice versa. What is interesting at this is that when pulling the elevator function "back", the rear elevons go up and the front canards go down. This removes significant speed from the plane. Certainly, YMMV because my plane has a VERY large canard surface which contributes to a non-existent stall characteristic. The plane would drop (with throttle cut) at a about a 60 degree angle - VERY steep (and fast enough to warrant some throttle to avoid hitting at that speed / angle) towards the ground, and would do so even with FULL UP elevator on the stick.

On the flip side is the "Sleek EZ Canard" (black / yellow plane below). On that plane I used a singular canard function for elevator, and flaperons for the rear wing. The interesting thing about that configuration was that I could dial in the flaps using the flaps dial on my 6 channel transmitter, which would off course start to pitch the nose down. But given the ample canard surface, I would then pull the elevator back. That bleeds off a lot of speed, and would make the plane pitch about 20 degrees nose up, but fly more slowly, and still provide control using the ailerons. Admittedly, I have only done this a few times on the plane, as I've not had a lot of opportunity to fly it, but it was very stable, and would make nearly pinpoint landings that way. However, this was using some thrust from the aft-mounted pusher motor, so again, YMMV.

Hope that helps somewhat in determining which direction to go with a glider.

Originally Posted by canard addict

I read that a canard aircraft takes 30 percent less power to fly.

That's simply not true. If using a canard layout inherently resulted in anywhere close to this amount of benefit, ALL aircraft would be canards! It would require that airplane designers be intentionally stupid to do anything otherwise.

I figure that this is because there are two lifting surfaces and that the large main wing has a smaller angle of attack and therefore less drag.

Well, if you're making some of your lift with the canard, and make no other changes in the design of the main wing, then for the same airspeed and loading, the lift coefficient and therefore the angle of attack of that wing will be lower for that particular flight condition. However, since the smaller canard can't make lift as efficiently as the larger wing, the total drag of the airplane is greater.

Also, if the job of the wing is reduced because you handed off some of its lift-making task to the canard, then you can make the wing smaller. However, you can't make it as much smaller as the amount of lift you reallocated to the canard, because you still have to make absolutely certain that the wing can never stall. Thus, your total wetted area ends up being greater, which results in more skin friction.

As far as the incidence of the wing being lower, not necessarily. If the canard is making positive lift, then it is also making downwash. Because of this, there is an induced "downdraft" behind the canard that the wing must fly through, which increases the wing's required incidence angle.

To me it follows that the descent ratio will be lower and the canard can stay up longer.

You're increasing total drag, which hurts L/D, which will tend to increase descent rate. Unless you can find some details or side issues that sufficiently offset this, you will suffer a net performance loss.

...If someone could come up with good air brakes, then spot landings would be easier...

There are all sorts of good airbrake designs. Airbrakes don't allow an airplane to slow down more, they just make it come down steeper. You still have to make enough lift to support the plane's weight. There are some "loopholes" in this that can be exploited in certain circumstances, but they have nothing to do with whether or not the plane has a canard layout; in fact, they might be easier to exploit with a conventional layout.

If you put flaps on a canard's wing, you then have to find some way to add more lifting ability to the canard in order to hold the nose up so you can use that extra wing lift from the flaps. However, if the canard has more lifting ability, then you have to figure out how to keep the canard from being able to pull the wing up into a stall when the flaps are retracted. That's what forced such mechanical contrivances as that variable sweep canard, linked through an elaborate jackscrew actuator to the wing flaps, on the Beech Starship.

Don, It looks like three strikes and I'm out on that last post. It seems that I read where a new canard super sonic liner was in the works which had no sonic boom and took 30% less power to fly. I just can't recall which thread or news item had the information. Maybe Airboat Flying Ship can help here. It led me to believe that canard liners were in solid for future high speed travel. As time passed, I must have let the 30% enter into slower canards. We are here to learn and your disscussions are great. Thanks and please don't go away. Charles

Originally Posted by canard addict

... It seems that I read where a new canard super sonic liner was in the works which had no sonic boom and took 30% less power to fly. ...

Maybe in one of the scientific tabloids like P.S., P.M. or S.D.?

Seriously though, the key term in your statement above is "supersonic". The rules for that are totally different.

OK, one item at a time:

About the only way to not make a sonic boom is to keep your speed below Mach 1.

It is possible to try to minimize shock waves, but as long as you are going to go at supersonic speeds, you're pretty much guaranteed one at least at the nose and another one at the tail. They look like giant cones being dragged along by the vehicle, like the v-shaped bow and stern waves in the surface of the water from a speedboat. About the only way to keep folks from feeling/hearing it go past them on the ground (what we call a "sonic boom") is to be so high or so far away (and we're talking a lot of miles here) that the shock wave dissipates before it gets to them.

Anyplace you have a sudden change in the cross sectional area of a supersonic or transonic (i.e.: where the plane is subsonic overall, but close enough to Mach 1 that the local airspeed around bulges, high points on airfoils, etc., can exceed Mach 1) aircraft, another shock wave tends to form, adding additional "wave drag". The added cross section at the wing is one example. The idea behind "area ruling", such as a "wasp-waist" or "Coke bottle" fuselage, is to slim down the fuselage in the vicinity of the wing so that the reduced cross section of the fuselage compensates for the added cross section of the wing. This can dramatically reduce the intensity of the shock waves formed by the wing, and the resulting wave drag.

Another example is the "extended upper deck" on some of the later Boeing 747's. Airliners like that are fast enough to get some local supersonic flow, and theefore they have to deal with wave drag. When they extended the upper deck, it filled in the region between the aft end of the original bulge behind the cockpit and the leading edge of the wing. This smoothed out the cross-sectional area distribution along the forward part of the airplane, which reduced the intensity of the shock waves formed by the aft end of the original bulge and the leading edge of the wing. The longer upper deck actually reduced drag in cruise.

Those "speed fairings" or "Küchemann carrots" on the old Convair 990 airliner served a similar function, smoothing out the cross sectional area plot around the trailing edge of the wing, reducing the intensity of the local shock waves and reducing the plane's wave drag in cruise.

There's a nice discussion of this at:
http://www.aerospaceweb.org/question...cs/q0240.shtml

As far as canards helping efficiency, there is some possibility there when at very high supersonic speeds. In some cases they can arrange the aircraft so that lifting surfaces on the aft portion of the aircraft can "surf" on the shock wave formed by the forward portions of the aircraft, which can help the induced drag (drag that results as a by-product of making lift). The XB-70 was one of the first designs to try to achieve this, with the big delta wing trying to surf on the shock wave from the nose and canard. They also have "waverider" aircraft undergoing study, typically a long parabolic-shaped flying wing, that does this.

There are also hypersonic "aerospike" systems where a small probe on the nose creates a shock wave, and the rest of the airplane sort of hides inside of it.

The Russians have a supercavitating rocket-powered torpedo in service that does something loosely conceptually related under water (in their case using a nose that uses cavitation to create a vapor pocket, and the torpedo then travels through this gaseous vapor instead of liquid water), which allows it to achieve over 200 knots submerged.

However, all of this deals with shock waves and trying to minimize the massive drag that they cause, which is proportionally well in excess of the sort of drag we deal with. None of it applies to the case of a subsonic aircraft. If you don't have any supersonic flow, you don't have any shock waves, so you don't have any wave drag to try to minimize. That's also why things like swept or delta wings don't help efficiency at our typical flying speeds.

Steven Wong has completed his maiden of his Velociraptor, here is the awesome video:

http://www.rcgroups.com/forums/showa...mentid=1362735

Johnnie

What a fabulous video and model!! Many thanks to Steven and Rajoo. You made my day! Charles

Loved the music. How come I don't hear that when I fly my Voyager Long EZ. All I hear are screams. Tommmmmmmmmmmmmmm !

This shows details of the hollow aileron construction of the twin delta canard. Charles

Bought this plane from a friend after he won in it in a raffle yesterday and it wasn't his cup of tea. Chopped and moved the elevator and stab forward and wing further back.Not sure on power system or anything at this point but will post when I am.

Ace, I'm working on a similar model. Plesae give some details on the name and where I can get one. Charles

Charles,your plane is what inspired me

This F-16 look alike is what I started with.http://www.nitroplanes.com/ffijeteparf.html

Thanks ACE for the info. You have done a good looking job on the re-style. I am Delta crazy now and have let Randy build me his exciting Dixie Delta. This is truly an amazing piece of work. Check it out here. http://m-a-e.com/Sub_Pages/Products/...and_Videos.htm Be sure to look at the flat spins near the end of the video. Charles

Thanks Charles. tryed to watch the vid but need a wmv format

Sorry, gang, the F16 EP ARF from Nitroplanes is sold out ... it had been on sale at $40. Still, a beautiful conversion, Mustang Ace!
...and the video is wmv format...just right link and "save target as" to your harddrive...wish they'd edited the soundtrack so we didn't have to listen to the photographer grunting all through the video!

pjw