Dihedral canard-why?

[nadt770]

What is the reason for going to a canard with dihedral? I'm just curious.

 

John

[Jon Matcho]

The theory is that by doing this the ailerons will have more undisturbed air crossing them, which will increase the roll rate/authority. However, the theory is not yet a proof and most are keeping their canards straight.

[Marc Zeitlin]

The theory is that by doing this the ailerons will have more undisturbed air crossing them, which will increase the roll rate/authority. However, the theory is not yet a proof and most are keeping their canards straight.

That may have been the original theory, but the folks that have the dihedral canards say that they can't tell any difference whatsoever from the straight one. Mostly, it's for looks.

[Jon Matcho]

Mostly, it's for looks.

But... what about those that don't think it looks better? I, for one, am not smitten with the look.

[Marc Zeitlin]

But... what about those that don't think it looks better? I, for one, am not smitten with the look.

I'm with you - I think it looks like crap, but that's what makes the world go round.

[Jack Morrison]

I agree with Jon and Mark. The wings are straight, why a dihedral canard, just does not follow any form as I see it.

 

Jack Morrison

E Racer 113

[nadt770]

Thanks for the input guys. I also like the looks of a straight canard.

[Wayne Hicks]

Vance Atkinson (Cozy III) is on record in the CSA newsletters as saying:

1. The dihedral canard is more complex to build.

2. Takes longer to build.

3. He saw NO performance gains from his previous straight canard.

4. Would never do it again, wasn't worth it.

[jperryfly]

I think Rutan's airfoil guru is the one that came up with it. I've got one so I'm one that is all for it.

[Lifessamsara]

I had no idea that people had constructed AND flown with dihedral canards?

Has anyone experimented with swept canards to anyones knowledge, and if so, the results/comments?

 

Cheers,

 

Bruce.

[Richard Riley]

A swept canard would be significantly more complex to build. It could be done, and it might look snarky, but it wouldn't be faster.

 

You'd have to do a different canard attach system, since it would put torque on the current lift tab system. Since the elevators would no longer be in line you'd have a more complex way of activating them. Since span would be reduced you'd be creating more induced drag for the same lift.

[Lifessamsara]

Is there any substance in the theory that the dihedral Canard reduces the wash over the strakes/wings and therefore reduces drag?

 

Bruce.

[Marc Zeitlin]

Is there any substance in the theory that the dihedral Canard reduces the wash over the strakes/wings and therefore reduces drag?

 

Bruce.

No performance difference has ever been measured on any aircraft that has changed from a straight to a dihedral canard.

[Lynn Erickson]

I had no idea that people had constructed AND flown with dihedral canards?

Has anyone experimented with swept canards to anyones knowledge, and if so, the results/comments?

 

Cheers,

 

Bruce.

yes, the beech starship and the zunni at chino have sweep canards. done to shift center of lift

[Richard Riley]

No performance difference has ever been measured on any aircraft that has changed from a straight to a dihedral canard.

In theory, there's a clear advanatage for the dihedral canard. By raising the tips, the canard wingtip vortex passes over the strakes with more clearance.

 

Now, in theory, there's no difference between theory and practice. In practice - Marc's correct. Any difference in performance is not measurable.

[Lynn Erickson]

In theory, there's a clear advanatage for the dihedral canard. By raising the tips, the canard wingtip vortex passes over the strakes with more clearance.

 

Now, in theory, there's no difference between theory and practice. In practice - Marc's correct. Any difference in performance is not measurable.

there was a study on a long eze done by a collage student and that study deterined that the tips needed to be 14" higher to make a difference

[Marc Zeitlin]

there was a study on a long eze done by a collage student and that study deterined that the tips needed to be 14" higher to make a difference

I think you're referring to these two "reports":

 

http://users.wpi.edu/~stay1or/INTROW.html

 

and:

 

http://users.wpi.edu/~stay1or/canard2.htm

 

We've discussed these a couple of times here, once a year and a half ago at:

 

http://www.canardzone.com/forum/showpost.php?p=11252&postcount=74

 

and again a month ago at:

 

http://www.canardzone.com/forum/showpost.php?p=16827&postcount=53

 

I wouldn't use any of the "conclusions" that were drawn in these papers (and I couldn't find any reference to a 14" canard height above the main wing in them, but I didn't kill myself looking) as an indication of what anyone should or shouldn't do regarding full scale aircraft (or even models, for that matter). As I said, these were interesting undergrad experiments, but they're far more useful as a learning experience in how to use wind tunnels for the experimenter than they are as information sources for aerodynamicists.