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Old Jun 16, 2007, 04:31 AM
who has rabbit ears down
Captain Canardly's Avatar
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I have never had a canard failure with my full flying canards
johnny
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Old Jun 16, 2007, 12:00 PM
Rhinebeck CD-99,00,01,02
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New Bern, NC
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Nor did I with my FireBat Johnny. It would just do a little dip on a high speed pass, and with the stock speed 400 it wasn't much of a high speed pass at all. Darn thing flew great. Had a guy watching me fly it at NEAT a few years ago and come to find out he was a Great Plane rep and was impressed with the way mine flew. Many guys trashed theirs early on. It just needed to get on step before doing anything fancy. It looked like a jet, but had the power of a Cub. Anyone got a new one in box for sale? I would love another one with a MEGA brushless on the tail. Tom
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Old Jun 20, 2007, 12:46 AM
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Captn Canardly, I am curious about your canards. Have you ever flown a canard in an electric glider competition? If you did, what do you think would be the best way to implement brakes to help get maximum landing points?
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Old Jun 20, 2007, 10:39 AM
who has rabbit ears down
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John!
i quit competing in my early sobriety, but if you need brakes, I would go with a split rudder, or flaps and lots of elevator authority installed.
the best method for brakes and canards is none.- Just become aquainted with it's envelope, and slightly higher flight speeds!
Johnny
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Old Jun 21, 2007, 09:40 AM
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Thanks captain, there are a number of competition glider flyers at my local electric only field. The guys are always playing around with their flap mixes to get the most accurate landings. There are no canard flyers, though it always gets me thinking about the design issues and challenges.
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Old Jun 21, 2007, 10:04 AM
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Quote:
Originally Posted by John235
... There are no canard flyers, though it always gets me thinking about the design issues and challenges.
The problem is that in order to have safe stall characteristics, you have to limit the max lift of the wing in ALL situations so that the wing can never stall in ANY situation. As a result, a canard configuration ends up needing more wing area to do the same job at low speeds than a conventional layout needs. This extra wing area (and the resulting skin friction) hurts your performance at high speeds, such as during launch, or penetrating wind.

In addition, the fact that you must make a significant amount of lift from the smaller flying surface up front (which, because it is smaller, is a less efficient producer of lift than the main wing, so using it results in a reduction in the aircraft's overall lift-making efficiency), and because the wing has to fly in the downdraft induced by the canard, the net result of both of these factors is that the total induced drag tends to be higher, which hurts your low speed performance.

In addition, some of the experiments with canard sailplanes indicated that they had problems with not enough cues to the pilot when they encountered updrafts. IIRC, that was one of the problems with the canard full-scale sailplane Rutan tried years ago.

The net result is that canard layouts have not proven to be very successful for sailplanes. That does not mean that one couldn't be in certain applications with some sort of special requirements, but in general it hasn't been a good design solution so far.
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Old Jun 21, 2007, 11:15 AM
who has rabbit ears down
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Sorry Don!
I haven't had great success with Standard configuration!
Johnnyhttp://www.rcgroups.com/forums/showthread.php?t=701060http://www.rcgroups.com/forums/showthread.php?t=701060
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Old Jun 21, 2007, 02:36 PM
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Elevon Set Up for Short Coupled Canards

First, Let me say that Dave aka Magic 612 furnished me with this idea and gets full credit for it.Today, I recieved my new Airtronics RD 6000 Super and followed Dave's advice for my Double Delta Canard. Since the canard wing is close to the COG, it needs help from the main wing to control elevation. This set up will give elevon control to both surfaces and allows the rear wing to deflect opposite flap action relative to the canard flaps. The aileron action is the same on both surfaces which should give exciting roll performance. I am excited and anxious to see this in action. If the canard wing is large enough and has long coupling to the wing as on Dave's new canard Despretz J1-31( see post#781, page 53) the canard should be able to handle elevation by itself. Charles
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Old Jun 21, 2007, 03:08 PM
Bernoulli+Newton=Lift
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Quote:
Originally Posted by canard addict
John's new canard Despretz J1-31( see post#781, page 53)
Pssst... Charles, I posted that. And it's "Dave", not "John". Although I did always like that name. If my parents had named me John, I'm sure I'd have been okay with it.

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Old Jun 21, 2007, 05:13 PM
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Apology

Dave, Please forgive me. I have lot's of respect for both you and John. I see you gave me the method on page 54, post#804. I have corrected my erroneous post. Charles
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Old Jun 21, 2007, 05:48 PM
Bernoulli+Newton=Lift
magic612's Avatar
Somewhere south of Chicago, IL
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Quote:
Originally Posted by canard addict
Dave, Please forgive me. I have lot's of respect for both you and John. I see you gave me the method on page 54, post#804. I have corrected my erroneous post. Charles
Not a big deal, Charles. I seriously thought John had given you that info, until I read the page and post number info, and though, "Wait, that sounds like where my post would have been." Went and checked, and thought, "Hmm... I think he's confusing me with someone else!"

Again - no biggie, and thanks for the corrections. I can't wait to hear the flight report and get your thoughts on the interconnected elevons / canard flaps. Looking forward to it!
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Old Jun 21, 2007, 08:41 PM
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Don, Thanks again for the post. Although I have heard those comments previously, I think you are absolutely right to bring them into the discussion. My building schedule is pretty full at the moment, so I won't be putting together an electric glider this year at least. I realise that a canard electric glider has a few challenges as you wrote in your post.

Model aircraft has some differences with real life gliders. Mainly the stall of model aircraft is much more likely to take the pilot by surprise, since there is no airspeed meter and you don't get any of the same sensations as flying a real airplane. Personally I think that safe stalling behavoir is very desirable for model aircraft. I can see some potential advantages for the electric glider competition such as 1) When flying at maximum altitude, where you can hardly see the model. 2) In the final descent it may be easier to nail the landing marker, assuming ideal safe stall behavior is maintained with brakes on and off.

For me it would simply be a design investigation, and it might well end up being an exercise in proving exactly why your points are valid. I am still interested to know of others who have built canard gliders.
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Old Jun 21, 2007, 10:10 PM
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Canard efficiency

I read that a canard aircraft takes 30 percent less power to fly. 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. To me it follows that the descent ratio will be lower and the canard can stay up longer. I also read from some material from Dereck Woodward that the canard gliders have had success in competition. If someone could come up with good air brakes, then spot landings would be easier. JUst my two cents. Charles
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Old Jun 22, 2007, 11:00 AM
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OK I'll work them in!http://www.rcgroups.com/forums/showthread.php?t=701060
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Old Jun 23, 2007, 02:20 AM
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The idea I had in mind was to make a polyhedral wing using a flat centre section and ailerons on the tip panels. 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. Crow flap mixing is an obvious possibility for braking, but that means adding control sufaces on the inboard wing panels, which I prefer to avoid.

Another idea I had was to use aileron differential. That should work well on a canard because it not only adds a braking effect to control yaw, but also reduces the need for up elevator on the canard. These two effects together will hopefully improve the efficiency when banked in a thermal.
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