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Old Mar 27, 2015, 03:06 PM
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Basic Guy

[QUOTE][/Could someone discuss the similarity between canard and delta wings. To my mind they are about the same with the deltas having big flat body between the canard and the main wing. QUOTE]

Rutan must have considered the advantages of filling in the space between standard canard wings with a delta on the Long EZ. It has the advantage of moving the CG to the center so that elevator and rudder controls have plenty of leverage about the CG. Also with a central balance there will be little tendency for the main wing to stall while the canard continues to fly. The canard and main wing fly as a unit as I see it and at high angles of attack the delta section continues to lift with high drag. In this arrangement, the canard need not have much incidence if any because it will stall before the main wing drops too much and restore normal flight.

Charles
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Old Mar 27, 2015, 06:02 PM
What could possibly go wrong?
nickchud's Avatar
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Charles, here's my two penn'orth.....

I think the incidence of the canard is a function of how much load that wing has to carry. Whatever incidence you start out with, you will have to trim in flight to make up for the load you're putting on the canard by the placement of the C/G. That's for straight and level flight.

At the point of stalling, if the main wing is a delta, you will be confident that it can manage a high AoA before it stalls and, at that high angle, it's more likely that the canard will stall first.

Something that has bothered me with my various Starship efforts is the problem of Reynolds numbers. I don't think I can get away with such a small canard. However, a swept canard might help to increase the Reynolds number.

What d'you think?

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Old Yesterday, 12:16 AM
who has rabbit ears down
Captain Canardly's Avatar
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sweeping the canard has nothing to do with renold #s.they are how many molecules going over the chord/depth- ya know, that compounded calculus stuff.!
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Old Yesterday, 02:40 AM
What could possibly go wrong?
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Well, what I was wondering was 2 things: One, if the canard is swept, the chord is greater, the molecules have further to travel than with the same canard if it is not swept. And second, do swept wings stall at a higher AoA? In other words, can I get away with a narrower canard if it's swept?

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Old Yesterday, 05:17 AM
Ayn Rand Sez.............
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What got me thinking of the similarity between Delta and canard was when I home brewed a Delta with a lot higher AOA at the nose than at the tips. I thought, that is the way that a canard is designed.

Nickchud, I am all for a delta or swept canard wing. After all the plane is a delta and a canard.
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Old Yesterday, 12:04 PM
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Nickchud

[QUOTE][/At the point of stalling, if the main wing is a delta, you will be confident that it can manage a high AoA before it stalls and, at that high angle, it's more likely that the canard will stall first.
QUOTE]

I agree

Quote:
Something that has bothered me with my various Starship efforts is the problem of Reynolds numbers. I don't think I can get away with such a small canard. However, a swept canard might help to increase the Reynolds number.
The more you sweep the wing back, the lower the lift and probably the lower the Reynolds number as I see it. The Reynolds number is proportional to speed and chord and is large for full scale planes. Given the same viscosity of the air, our models need to be light with lots of area to float on air with low speed.

Regarding the incidence of the canard, it must be higher on canards like the GWS Slow Stick with the CG well forward of the main wing. The canard will be carrying a heavy load at a high AOA to assure that it will stall before the main wing reaches it's maximum lift point. I do feel that high speed canards might work OK with less canard area and positive incidence.

Charles
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Old Yesterday, 01:32 PM
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Quote:
Originally Posted by nickchud View Post
However, a swept canard might help to increase the Reynolds number.

What d'you think?

It's the opposite. Sweep makes a lot of span-wise flow, such that the local chord-wise flow is lessened, increasing chances of stall (especially outboard). Various strategies are employed to minimize span-wise flow. The most obvious/visible is vertical "fences" on the wing like seen on the Mig-15 (looking this up will provide a fairly good understanding of span-wise flow on swept wings).
So why is sweep ever done? Answer: Less drag at higher speeds. It's also especially useful at trans-sonic speeds (too complex to explain in a few words).

Where do we see all this in its most obvious form? Swing-wing aircraft (F-14, F-111, etc.) - at low speed the sweep is minimized. At high speed it is swept back as much as possible.
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Old Today, 02:22 AM
What could possibly go wrong?
nickchud's Avatar
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Aha, thanks chaps.

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Old Today, 10:41 AM
Lookin' up at the centerline
taildragger1589's Avatar
Lawrenceville, Georgia
Joined Feb 2005
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Quote:
Originally Posted by nuteman View Post
Sweep makes a lot of span-wise flow, such that the local chord-wise flow is lessened, increasing chances of stall (especially outboard).
In other words, too much sweep and you'll need a dust pan.
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