Canard Forum: Show,Discuss, Learn - Page 51 - RC Groups
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May 16, 2007, 06:52 PM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar
Thanks Charles, and thanks to all who chimed in with positive feed back on their Voyagers. Mine truly flies like a piece of cake. I may bring it to Morriston next weekend, but I have a few models I was hoping to bring up there to sell, so I am not sure just what I can fit in the Prius. Tom
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May 16, 2007, 10:31 PM
3d and EDF, some scale
MustangAce17's Avatar
Tom,I'd love to see the 55" Voyager at Morriston, I'll try to have my design and my 36" LEZ flying along with some other neat birds.
May 16, 2007, 10:44 PM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar
I really want to bring it, but being a one piece model, it takes up a lot of room in my car. I have a few models I want to sell and was hoping to bring therm too. I may come both days. Saturday to sell stuff and Sunday to fly, or vice versa, depending on the weather. I have a new 1911 Taube that is flying beautiful now and would like to show that one too. I need a truck. Whatever, I'll be there. See ya next weekend Kyle. Tom
May 16, 2007, 10:52 PM
3d and EDF, some scale
MustangAce17's Avatar
Will be good to catch up, the Taube sounds nice
May 17, 2007, 08:17 AM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar

1911 Taube

Taube in German means pidgeon, and this thing looks like one when it is flying. I have a geared Astro 15 in her running on 3s 4200mah lipos. Rudder, elevator, and throttle for controls. The original aircraft had wing warping. But the Voyager is soooo cool.
May 17, 2007, 09:47 AM
3d and EDF, some scale
MustangAce17's Avatar
neat Tom! see ya there
May 18, 2007, 08:33 PM
That motor isn't hot...
rosco's Avatar
Maidened the canard this morning, it was a sinch!
Thanks to all for their input.
I calculated the C.G. with 15% static was very stable.
Maybe 10% would have been fine
We did a hand launch from the roof of a small shed, just for a little bit of height, but it wasn't needed.
It only needed 1 click of down and it was right!

It had 3 degrees of positive incidence on the canard and because it is a pretty lifty main wing, I took someones idea on board and added a about 3mm (1/8 inch) upward reflex on the ailerons.

No tip stalls or easy as pie to land as well, as the wing loading was fairly low.
May 19, 2007, 06:34 AM
Registered User
Congratulations, Rosco!!!. Welcome to the canard world. You can now take your basic design and expand it to different styles. You may be able to remove the reflex and return the elevator to neutral. Charles
May 21, 2007, 03:50 AM
Registered User
Markus Meier's Avatar
Hi there

just wrote about the new Graupner Canary here

Greetings Markus
May 21, 2007, 07:21 AM
Dr John
pmpjohn's Avatar
Pretty nice Markus. FWIW that is how the rudders on the full scale Long EZ work.

May 21, 2007, 07:06 PM
Registered User
Markus,Thanks for the great report. The model looked like it wanted to nose down in the video, maybe a little nose heavy or in need of UP trim. It seemed the crash was not meant to be a landing. I would leave the rudders neutral and add ailerons to mine. Charles
May 21, 2007, 08:50 PM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar
Flew my Voyager Long EZ again today. Take off was a non event, and she handled the winds pretty well. Whoever said a canard can't stall is incorrect. Mine will. I wanted to see how much I could slow it down so I reduced throttle to 1/4 and started bulling the nose up. Of course, I was plenty high, just in case. She slowed very well and then dropped the right wing and did one full spiral pointing straight down. I let it drop a bit and pulled up elevator, while stopping the rotation with the aileron, and it recovered nicely, but lost about 50' in the process. So, it stalls, but you have to be crawling to do it. Normally, I would never fly a model that slow. Getting use to it's look in the sky too. At first, on the down wind legs of my flights, it was hard to tell if the plane was level or not. Today, the fifth flight on the machine, I had no problems what so ever with orientation. It's a hoot to fly. Tom
May 21, 2007, 10:36 PM
Registered User
Don Stackhouse's Avatar
Originally Posted by Tom Smith
... Whoever said a canard can't stall is incorrect. Mine will... She slowed very well and then dropped the right wing and did one full spiral pointing straight down...
The fact that you had a rotation indicates that the main wing stalled asymmetrically, but the fact that you still had aileron authority indicates that the stall was not too severe.

The concept that a "canard can't stall" goes back to the idea that (properly set up) the canard stalls before the wing, in the process making it impossible to increase the angle of attack any further, so the main wing can never be stalled.

However, if the C/G is moved aft far enough, the canard has enough authority to pull the nose high enough to make the wing stall. At that point the wing could stall asymmetrically (i.e.: one wing stalls before/more than the other), resulting in a spin. This sounds like what you described.

In extreme cases, the wing can stall completely, before the canard, causing the plane to try to "swap ends". Definitely not good!

The cure is to move the C/G forward (puts more load on the canard, causing it to stall sooner and the wing to stall later), then trim some "up" in the elevator and/or canard incidence to get the hands-off flying speed back where you want it.

Any canard can stall (i.e.: stall the main wing) if it isn't specifically designed and set up to make it impossible. As you discovered, it isn't something that happens naturally or inherently in a canard layout, it's something that MUST be designed in. And, the consequences of not designing it in properly can be very severe.

The down side of making the wing totally stall-proof is the same as for any other type of airplane with this artificial limitation. If you limit the wing's ability to increase angle of attack enough that it always stays at some margin of safety below stall, then that means that you can never quite get max lift out of that wing (you come up short by the amount of safety margin included). This means that to achieve the same low speed performance, you need to compensate with more wing area, and with it more wing weight, wetted area and skin friction. As always, in airplane design there is no free lunch.
May 21, 2007, 11:31 PM
Rhinebeck CD-99,00,01,02
Tom Smith's Avatar
Thanks Don, I was hoping you would read that. After reading my last post again I remembered that it stalled to the left, not the right. I was sure glad it pulled out. Pointing straight down I thought, oh no, could this be the end. But she pulled out just fine and I flew her around for another 5 minutes or so. My CG is at 15.75 and I think I will leave it there because I really had to work hard to get that thing to stall today. I believe my current setup is safe for normal sport flying. Last week I added a little up in the canard, a bit of reflex in the ailerons, and it flies hands off at 1/2 throttle. I'm a happy camper. Next flight I will try flying her inverted. This is a really neat model for the price. Tom
May 22, 2007, 07:27 AM
Indifferent User
pjwright's Avatar

Canard Stall

You might take a look at post 664, Tom ... referencing Tom Lennon's airfoil recommendations for a canard design. In line with Don's post, the point that Mr. Lennon is making is that properly designed (right airfoils and correct AoA's), the canard-equipped aircraft will self-recover from a stall, since the mainplane keeps "flying" after the foreplane stalls.
But Don's point about the relationship of the CG location to the amount of lift the foreplane provides is an important factor in how squirelly the canard will be. Too small a foreplane (as canard addict has pointed out) will push the CG aft, and decrease the "safety margin" - something that was experienced in the Curtiss XP-55 Ascender:
"Initial flight testing revealed that the takeoff run was excessively long. In order to solve this problem, the nose elevator was increased in area and the aileron up trim was interconnected with the flaps so that it operated when the flaps were lowered."
This reveals two points that Charles (canard addict) has made regarding canards: canard elevator area and aileron reflex. The XP-55 report goes on:
"On November 15, 1943, test pilot Harvey Gray was flying the first XP-55 through a series of stall tests when the aircraft suddenly flipped over on its back and fell into an uncontrolled, inverted descent. Recovery proved impossible, and the plane fell out of control for 16,000 feet before Gray was able to parachute to safety. The aircraft was destroyed in the ensuing crash."
Sounds exactly like the "worst-case" that Don described. Curtiss attempted to improve the stall characteristics on the third prototype:
"It was found that stall characteristics could be improved by adding four-foot wingtip extensions of greater area and by increasing the limits of nose elevator travel. However, the first flight revealed that the increased elevator limits resulted in the pilot being able to hold such a high elevator angle during takeoff that the elevator could actually stall. After modifications, stall tests were performed satisfactorily, although the complete lack of any warning prior to the stall and the excessive loss of altitude necessary to return to level flight after the stall were undesirable characteristics."
As you can see, the XP-55 with it's comparatively small canard was a handful to fly, and never went into production due to a combination of handling problems and the cancellation of the prototype Pratt and Whitney engine around which the airframe was designed.
I'll be stopping by the Kalamzoo Airzoo next month to take photos of the completed XP-55 restoration.

pj wright

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