Has anyone tried the Gunderson AeroDesign Canard Sport Slope Sailplane? I've been eying the banner up in the corner of the slope forum for some time now but I don't remember reading any threads on the plane.

Pete

Same here... unfortunately, it seems that all of the Canards in R/C flying have simple flat-plate canards - no actual lifting surfaces.

That probably doesn't matter too much to the average guy, but I'm an old Burt Rutan fan who loves the concept of having 2 lifting surfaces on a plane... Doing so removes the possibility of some things like true snap-rolls (because its hard to stall both surfaces on the same side of the plane at the same time), but the efficiency of having 2 lifting surfaces is really nice!

Take care,

--Noel

P.S. Sometime this summer, I am *going* to come up with an EPP canard design for the slope... stay tuned!

P.P.S. It occurs to me that having a flat-plate or symetrical foil on the canard has one advantage for R/C flying: Inverted performance will be a little better. Not as much of an issue for full-sized planes...

Well granted it says "first flight", but the video from that site shows some pretty twitchy pitch control.

http://www.gundersonaerodesign.com/v...stflighthq.wmv

Nards do the best flat spins!

I always liked nards but the horizontal in the front is just not a great config for slopers. Unless you fly on a nice mowed grass slope or the nard is made from solid carbon fiber you just end up breaking them on landing.

TFLG

Originally Posted by Cziltang Brone

Well granted it says "first flight", but the video from that site shows some pretty twitchy pitch control.

I noticed that too, but it's hard to tell if it's a flight characteristic or a combination of the pilot being unfamiliar with the plane and too much elevator (canard) throw.

Pete

Originally Posted by TFLG

Nards do the best flat spins!

Uhhh, if they're well-designed they shouldn't... I mean, unless that's a flying quality you WANT.

Rutan's revival of the canard was to make a spin-resistant and stall-resistant design! He did this by designing the planes to ensure that the canard would always reach its critical angle of attack BEFORE the main wing did. This would effectively drop the nose and immediately lower the angle of attack of the main wing - preventing departure from controlled flight.

Now, it turns out that if you don't have the right incidence set up, or you overload the tail of the plane (extreme aft CG), then sometimes you can pull the nose up fast enough to stall both the canard and the main wing. In this case, the weight in the rear of the plane causes it to "deep stall" - essentially falling tail-first in a stable configuration (i.e. it wants to stay that way, and with the air going backwards over the controls you don't have much authority to correct it). A sharp yaw input at the moment of stall is about the only way to stop the deep stall from fully developing; but its a tricky maneuver.

Fun trivia fact: SpaceShipOne also exhibited a potential "deep stall" characteristic in the original design. Additional tail-surface area had to be added during testing to overcome it. The Discovery Channel Special "Black Sky" (available on DVD) is pretty awesome coverage of the development and testing of the plane - and you can see the "event" that Mike Melville gets into (and out of, thankfully) when they found this out during a flight test... Wow!

Take care,

--Noel

P.S. The potential for nose & 'nard damage is why I want to make an EPP design... Its been proven that EPP does not equal low performance, so the extra durability is a big plus IMHO.

Mark drela posted the following:

A canard is really an extreme conventional configuration with the following features:
1) a small highly-loaded wing
2) the c.g. WAY back, at 538% chord or whatever
3) a huge lifting tail to give enough stability with this extreme aft c.g.
If this doesn't sound like an efficient sailplane setup, it's because it isn't.

BTW, those of you who don't knwo who mark drela is, he's an r/c sailplane designer, and a professor of aerodynamics at MIT. He wrote the famous XFoil software that profili and most modellers use to analyze airfoils. He's most famous for his incredibly effecient thermal designs, although he has contributed some to ds theory. In short, he is GOD. my idol to the nth degree. etc.

--Alex

Originally Posted by raptor22

BTW, those of you who don't knwo who mark drela is, he's an r/c sailplane designer, and a professor of aerodynamics at MIT. He wrote the famous XFoil software that profili and most modellers use to analyze airfoils. He's most famous for his incredibly effecient thermal designs, although he has contributed some to ds theory. In short, he is GOD. my idol to the nth degree. etc.

--Alex

Thanks for telling us who this Drela guy is...we would have never known...

Alex -

Yes, Drela is a smart and amazing guy. But he's not infallible and he's prone to the same biases that all humans have. Look at Einstein - the guy thought Quantum Mechanics was a bad idea, yet for all its wackiness it has proven to be sound!

Burt Rutan is also a smart and amazing guy... ANYone who builds and flies an average of 1 new FULL-SIZED airplane design each year (most of them being man-carrying, and one being a sub-orbital spaceship) for nearly 30 years has got some crazy skills and vision. Possible flaws and quirks, yes - but you can't dispute the success-rate.

And have you flown a Canard plane?? 'Cuz I have. I've flown a Cessna 172, a Diamond DA-20 (low-wing composite trainer aircraft), a Piper Archer, and a Rutan VariEze... And the VariEze was by far the most efficient in terms of speed and fuel economy - not to mention being very maneuverable and a blast to fly!

Take care,

--Noel

Originally Posted by NWade

He did this by designing the planes to ensure that the canard would always reach its critical angle of attack BEFORE the main wing did. This would effectively drop the nose and immediately lower the angle of attack of the main wing - preventing departure from controlled flight.

Also preventing full-stall landings, thus increasing landing speeds and distances; and preventing turns at Clmax, thus lowering max turn rate (i.e. maneuverability), etc. Canards have an 'apparent' benefit by potentially reducing trim drag in cruise, but it's not a free thing....and by 'apparent' I mean something that might look like a plus but isn't always so.

Originally Posted by NWade

...sometimes you can pull the nose up fast enough to stall both the canard and the main wing. In this case, the weight in the rear of the plane causes it to "deep stall" - essentially falling tail-first in a stable configuration (i.e. it wants to stay that way, and with the air going backwards over the controls you don't have much authority to correct it).

Uh...'deep stall' is *usually* associated with a stable high AOA condition, usually less than 90 deg AOA (i.e. not falling tail first). The current crop of fighter-type airplanes with canards often get around this by having large throws on the canards to get nose-down control power. Note also that not just canards have the potential for deep stall - F-16 pilots train for deep stall recovery using 'manual pitch override' and pitch rocking.

Not that any of this has much to do with slope soaring - canards at the slope look cool, and for some (myself included) that's enough. Just don't talk yourself into a performance benefit that's probably not there.

Nauga,
with controls released, feet off the rudder, speedbrake in.

Good stuff, Nauga!

For the record, I know what a deep stall is technically - I was using laymen's terms to get the point across; but thanks for correcting me. I guess it would have been more accurate to state that during a deep stall the moving surfaces tend not to have proper airflow over them; so they don't provide effective control for breaking out of the stable (or semi-stable) stall.

Conventional planes are susceptible to deep-stall; but because conventional tails are "negative lift" devices when pitching the nose of the plane up, the tail is flying at a lower angle of attack than the main wing - so the main wing typically stalls before the tail (leaving the pilot with control to break the stall, IF he does it right).

And you're right, there are trade-offs in the Canard design to be sure (there are in any plane - no such thing as a magical design that does everything). The long TO distance and slightly faster landing speeds are definitely things to be aware of.

I also think that some of the aspects of the Rutan Canards are more relevant to powered flight vs. gliding flight. For example, spiralling slipstream and other negative aspects of having a front-mounted engine and propeller are avoided with the pusher configuration of most canards... But with a glider these are non-issues.

Take care,

--Noel

Originally Posted by InTheLift

Thanks for telling us who this Drela guy is...we would have never known...

I wrote that because I don't know how many times I have said "xfoil by mark drela" and the person on the other side said "who?"

--Alex

Noel: I don't mean to take anything away from Rutan. He is an amazing guy. I am goign to college to get my aeospace engineering degree next year, and he is yet another peson I look up to.

Its just that, for our purposes, drela's evaluation of the subject is in line with real world observations.

Did you notice that rutan's "world flyer" is not a canard?

--Alex

Since we are on the subject of canards...and kind of on the subject of sweet rutan designs...here is one of the prettiest!

-hutch

Originally Posted by raptor22

I wrote that because I don't know how many times I have said "xfoil by mark drela" and the person on the other side said "who?"

--Alex

LOL! Just havin' a little fun with you Alex. Drela's work is always worthy of mention.