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Foreplane to wing incedence on a canard

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Foreplane to wing incedence on a canard

Old 06-11-2013, 06:36 PM
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tdstaf
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Default Foreplane to wing incedence on a canard

I'm looking to design a canard and was wondering if there was some basic incidence guide lines on the foreplane to wing?

Thanks Tim
Old 06-11-2013, 11:43 PM
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alasdair
 
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Default RE: Foreplane to wing incedence on a canard

Like with all R/C aeroplanes the CG HAS to be ahead of the Neutral Point.
A consequence of that is
    [*]Foreplane must have more incidence, or more camber, (or both) than the wing[*]It is normal for the foreplane to use a more cambered section than the wing[/list]
Old 06-12-2013, 07:34 AM
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Lone Star Charles
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Default RE: Foreplane to wing incedence on a canard

I suspect that the incidence of the foreplane with regard to the incidence of the wing has some 'rules of thumb'; however, I do not know what they are. Most of my aircraft have been aerobatic and have had incidences of 0,0,0 for engine, wing, tail. I would almost think that a 0,0,0 might be a good starting point for experimentation of a canard design. Obviously, the incidence of the foreplane can be adjusted by using a control surface or by making the canard a fully flying design (i.e. stabilator) in order to achieve stability. I think that the most important design consideration would be one that does not have any non-recoverable instabilities - or - a design that would not permit those instabilities to occur. It is my understanding of Burt Rutan's design of the VariEZ is that the canard always stalled prior to the main wing, thus creating an inability of the main wing to stall. Seems like a good idea.

I would love to see a fully aerobatic canard design. One that could perform rolls, loops, and snaps - both upright and inverted. Wonder what the design considerations for that would be.
Old 06-12-2013, 01:32 PM
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Rotaryphile
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Default RE: Foreplane to wing incedence on a canard

I have experimented extensively with glider and rubber power canards. They are just as capable of all aerobatic maneuvers as a normal tractor layout aircraft, if the CG is correct.

For a fully aerobatic canard, I, too, would start with 0-0-0. incidence and thrust. CG can be determined by building a simple cardboard hand-launched glider with adjustable elevators on the canard. I designed a canard pusher fully aerobatic pattern model for .60 power, which needed some sweepback to get the CG right.

Finished the detail drawings, but never built it. All models eventually crash if you fly them enough, and even a low-speed crash with a canard could be non-repairable, since the heavy parts tend to be rearward. On their path to terra firma during a crash, they will tend to demolish the canard and the front of the fuselage.

Having no control surface are in the propwash to counter torque, canards cannot hover, and torque reaction is much heavier than with a tractor.

My calculations and experiments indicated that its performance would be no better than with a normal tractor layout, and, also, pusher engines tend to overheat. In retrospect, there appeared to be no advantage, except for its startling visual impact at the field.
Old 06-12-2013, 07:55 PM
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Default RE: Foreplane to wing incedence on a canard

Apparantly on the full size Long-EZ (or however it's spelled) sizing the foreplane for stall behavior was important.

Part of the design and testing was that for the given desired CG range the foreplane was sized so that it would stall before the mainplane, so it would drop it's nose into the stall rather than it's tail. On a model you could probbaly just keep moving the CG forward and backwards until that stall characteristic was achieved??
Old 06-13-2013, 01:46 AM
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Default RE: Foreplane to wing incedence on a canard

Zero, Zero, Zero is not the answer, unless the last Zero means zero Stability. (yes I know you mean the engine thrustline, but which end is the engine?)

You need the foreplane at a couple of degrees positive to the wing, maybe more.
I would also advocate using a wing section with little or no pitching moment, like a symmetrical section, a 5-digit NACA, or an Eppler reflexed.

I have built s series of canard delta models (called Candel, as I'm not good with original names). They all flew, but improved with development.
They all had a tractor engine, small foreplane, delta wing.
The first had elevators on the flat plate foreplane, set at +2 to 3 degrees.
The second had BIG elevators, later an all moving foreplane.
The third had elevators on the foreplane and elevons on the wing
The fourth had a fixed foreplane (Clark Y thinned to 9%) and was controlled purely by elevons. It also had rudders. The foreplane was part of a front hatch for acess to tank/radio, and its flat bottom was rigged at Zero, like the symmetrical wing.

You don't need to be "careful" with the foreplane section/size. The foreplane will ALWAYS stall before the wing, because it is always more heavily loaded. Unless of courseyou go crazy with the foreplane section, and fit a very undercambered foreplane like a NACA 6409 or something.

What is a much more common problem on tail-firstmodelsis the foreplane stalling prematurely, before the wing gets anywhere near its stalling angle.
The problem with having e.g. a flat plate foreplane is that it stalls early. So on landing, instead of flaring out for a nice touchdown the foreplane stalls early and drops the nose hard on the runway.

I would advocate a symmetrical wing, or a 5-digit NACA with 1 or 2% camber, and a cambered foreplane like a thinned Clark Y, either all moving or with an elevator.

Seems we don't get photos again today. I'll try later
(Friday, photo upload working again)
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Old 06-13-2013, 05:55 AM
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Rotaryphile
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Default RE: Foreplane to wing incedence on a canard

I set up all my conventional layout aircraft with 0-0-0 wing incidence, stab incidence, and thrust offset. I regard any need for thrust offset as an admission of design deficiency. When an aircraft is inverted, downthrust becomes upthrust, and right thrust becomes left thrust; a rather odd setup.

The last thing that a full-out aerobatic aircraft needs is pitch stability. Pitch stability causes the nose to drop when airspeed decreases, and to rise when airspeed increases, making aerobatic line holding more difficult. With zero pitch stability, with hands off the controls, the nose tends to stay nailed to the same angle. This requires a far more aft CG; not too far ahead of the absolute aft limit where the aircraft becomes dynamically unstable in pitch.

My preceding incidence/thrust recommendations apply only to aerobatic aircraft. A free flight or R/C trainer-type canard would need greater incidence in the canard stab, a CG location that is well ahead of its neutral stability location, and probably some nose-lowering thrust offset.

Canards are frequently claimed to be safer, because the canard stab tends to stall before the main wing, causing the nose to drop, thus retaining a safe airspeed. In reality, exactly the same thing can be achieved with a conventional tractor layout, simply by locating the CG well ahead, so that the stab is unable to produce sufficient download to force the wing into a stall. The trade off, of course, is increased landing speed. A canard's stab supplies an up force at landing speed, and thus does not fight the wing, so that a canard with a forward CG location could have a slightly lower stall speed than a tractor layout would provide.

Canard homebuilt aircraft seem to suffer at least as high an accident rate as those with tractor layouts. In a tractor layout, the heavy parts hit the ground first in a crash, and the nose, which needs to carry the weight of the engine, is much stronger. In a canard, the pilot may be crushed and chewed up by a rear-mounted engine and propeller.

My experiments seemed to indicate little, if any, aerodynamic advantage to a canard configuration. My canard gliders produced no better sink rate than my conventional tractor gliders did. With so much fuselage side area is ahead of the CG, canards also need far greater vertical stabilizer area than tractors need, causing higher drag.
Old 06-13-2013, 06:34 AM
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Villa
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Default RE: Foreplane to wing incedence on a canard

Hi tdstaf
I designed and flew a Coroplast pusher Canard for about 8 years, with an OS-46FX engine. It had vertical stabs and rudders on the main wing tips. I started with a conventional main wing and later changed to a swept wing. With either wing there always was a right to left wobble that I could not get rid of; a Dutch Roll may describe it. I finally decided that the Canard wing may have been sending turbulant air to the main wing. I was thinking of lowering the Canard wing to eliminate this turbulance, but never got around to it. I had two bad experiences I would like to warn you about; I was trying to do a loop while in knife edge and had been moving the CG back to make it possible-this was with the straight wing. At one point the plane whent into an inverted flat spin that I could not recover from. On another, with the swept wing main wing, I was doing a high speed climbing turn when the plane snap rolled, and changed direction 180 degrees. I managed to save it. I concluded I had experience a high speed stall, due to too much elevator. I reduced the elevator travel so it could do any type of loop with no stall. One day a lelephone pole pop up in front of it and totaled the plane. I have never rebuilt it. Maybe someday. I used 2-3 degrees of positive incidence for the Canard wing, and zero on everything else.
Old 06-13-2013, 09:12 AM
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Default RE: Foreplane to wing incedence on a canard

Sounds as if Villa's canard lacked sufficient vertical tail area. Conventional, tractor configuration aircraft tend to Dutch roll if they are a bit shy of vertical tail area. Canards usually need far larger vertical tails to counteract the yaw-destabilizing effect of the fuselage area ahead of the CG. Their vertical tails are also normally much closer to the center of lateral pressure, reducing their effective moment arm. I found winglets or tip plates on the tips of the main wing of canards to be very helpful, particularly if the main wing has some sweepback. They can add badly needed lateral area, while reducing induced drag, thus partially offsetting the additional drag that they cause.
Old 06-13-2013, 10:36 AM
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Villa
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Default RE: Foreplane to wing incedence on a canard

Hi Rotaryphile
Thanks for your input. My Canard has a very small fuselage crossection, as you can see from the attached photos. If you still feel that more vertical stab area would help with the Dutch Roll, I'll try it next time. Unfortunately I could not upload my photos. There is some type of system error.
Old 06-14-2013, 12:11 AM
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Default RE: Foreplane to wing incedence on a canard

I too found that I had to increase the V-stab area beyond what looked normal.
You can see from my photos added to my post abovethat my first model had one fin, but subsequent models had two. A double sized fin would have looked daft, I felt,

Boeing with their 787, and Airbus with the new, today, A350 strive for the absolute maximum efficiency obtainable, and yet the layouts are conventional.
There are quite a few delta canard fighters around, but no successful canard transport aircraft that I can think of. No aerobatic canards either: all your Edge, Pitts, Extras are conventional.

It is common for conventional aerobatic models to be rigged 0,0,0 and carry uptrim for positive lift and downtrim for negative lift (inverted)

I usually rig mine +0.6 on the wing, with the engine and tail both at Zero.

Anyone know the angles for the Edge 540, Extra etc?
The Pitts has both wings at +1.5 degrees tailat zero, (all plus or minus 0.5). I asked the owner of a 1982 Pitts S2, and he looked it up for me.
Old 06-14-2013, 04:38 AM
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Default RE: Foreplane to wing incedence on a canard

The nice part of canards ?
they will flat spin nicely
recovery is problematic tho
Old 06-14-2013, 06:19 AM
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Villa
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Default RE: Foreplane to wing incedence on a canard

No doubt about it, a Canard is "different". Sometimes, due to high gusting winds, my Canard was the only one in the air. I would do 10 or more touch and goes each flight. I have wondered why I don't see more Canards at our field. Mine was exceptionally rugged because it was a SPAD. The 1" square aluminum fuselage was extremely rugged. Ugly? Yes, but I never thought that. I concluded that my Canard could not do a conventional snap-roll. It would knife edge all day long. Another characteristic I woulds like to warn others about is the tendancy for the nose to bounce into the air during a bad landing. The end result could be a total dissaster. But it is also a challenge. My plane once ended up with the nose in the soggy ground and the rest of the plane sticking up in the air, with the engine still running. It was hillarious. I learned that if a landing starts to be difficult, then at the instance that the mains touch the ground, I go to full down elevator. Since down elevator moves the elevator up on a Canard, the nose gets glued to the ground to prevent any nose bouncing. I flew mine for about 8 years. A Canard is different, and a challenge. I'm guessing that this nose bouncing during a poor landing has destroyed many balsa Canards, and may be the reason I see almost no Canards at our field. Now that you have the secret to prevent the nose bounce, try a Canard. I need a push to rebuild mine. At my current age of 77 it is more difficult to start a heavy project. Think of it; if I can fly a Canard it could not be all that difficult. Plus I have told you all of the bad habits.
Old 06-14-2013, 08:04 AM
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Default RE: Foreplane to wing incedence on a canard


ORIGINAL: Villa

No doubt about it, a Canard is "different". Sometimes, due to high gusting winds, my Canard was the only one in the air. I would do 10 or more touch and goes each flight. I have wondered why I don't see more Canards at our field. Mine was exceptionally rugged because it was a SPAD. The 1" square aluminum fuselage was extremely rugged. Ugly? Yes, but I never thought that. I concluded that my Canard could not do a conventional snap-roll. It would knife edge all day long. Another characteristic I woulds like to warn others about is the tendancy for the nose to bounce into the air during a bad landing. The end result could be a total dissaster. But it is also a challenge. My plane once ended up with the nose in the soggy ground and the rest of the plane sticking up in the air, with the engine still running. It was hillarious. I learned that if a landing starts to be difficult, then at the instance that the mains touch the ground, I go to full down elevator. Since down elevator moves the elevator up on a Canard, the nose gets glued to the ground to prevent any nose bouncing. I flew mine for about 8 years. A Canard is different, and a challenge.
Any photos?

As for the flat spin, my first would do it - and didn't recover. But it was so light and slow that landing in the heather did no damage.
I think it was due to the inertia. With the engine at the front and battery at the back, and yaw turned it into a spinning dumbell with the mass at each end maintaining the spin.

My Candel models, especially the later ones, were models I would fly in any conditions. Delta wing is especially good in a blustery wind as it is less sensitive to gusts than a wing of higher aspect ratio. Candels had to undercarriage, but later ones had a wire skid that allowed touch and goes. They didn't bounce on landing.
Old 06-14-2013, 11:14 AM
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Default RE: Foreplane to wing incedence on a canard

I'll try to load photos again.
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Old 06-14-2013, 06:59 PM
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Default RE: Foreplane to wing incedence on a canard

Thanks for all the input. I think I'll start with a NACA 24016 to 24011 for the wing and use a NACA 0010 for the for plane set at 2 deg. positive. The control throws would be the opposite from the standard elevator for the foreplane correct?

Here is a picture of what I'm trying to make.
I know its been done before Koyushu J 7 shindin

With a Fan.
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Old 06-16-2013, 10:41 AM
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Default RE: Foreplane to wing incedence on a canard

Since the Shinden has an EXTREMLEY small fore plane you're going to find that the CG location will be well back and likely somewhere on the first 10 to 15% of the main wing's MAC.

To get a feel for this try out this Canard Calculator;

http://adamone.rchomepage.com/cg_canard.htm

An all balsa chuck glider might not be a bad way to go to get a feel for the CG location as well. Something around 12 to 16 inch span with a flat 1/16 main wing and a 1/16 forewing with some "Clark Y" sanding done to the fore plane to give it a hint of camber. Make the fore plane angle adjustable by some means and play with the CG range to find out where it has pretty much neutral pitch stability. IE: When it stalls slightly it drops the nose and dives in with little or no attempt to recover.
Old 06-18-2013, 01:02 AM
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Default RE: Foreplane to wing incedence on a canard

Yes, observe where the main wheels are positioned!!
They are well BEHIND the CG to prevent it from tipping back, so you can see that the CG is WELL forward, as BMathews said.

The foreplane is SO small that a reflexed section (as you would use on a tailless aircraft) would by my choice. Think of it as a flying wing, with a tiny bit of help from that small foreplane.

I still think a cambered foreplane (e.g. NACA 2409 or a Clark Y thinned to 9%) would be better than NACA 0010
Old 06-18-2013, 12:04 PM
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Default RE: Foreplane to wing incedence on a canard

From the drawing I found at http://notasperdidasenlaweb.blogspot...1-shinden.html it looks like the final CG location will be pretty near or only slightly back from the leading edge of the rear plane wing root airfoil. This being based on the idea that the main gear would be located on a line swept back from the vertical through the CG at around a 15 degree angle

Your selection of a 24016 or 24011 would likely be controlled by the size of the model. All else being equal the thinner airfoil would do better on a smaller size model such as a smaller to medium size electric or glow powered model. Once you get up to a 5 foot span or larger the Reynolds numbers become high enough that the thicker 16% section would do well.

Alasdair, the 240xx series are a lower or neutral pitching moment style and should be fine for this sort of use. But I agree that making the fore plane with a postive camber airfoil would be a wise option. Tim something like a NACA 2410 would not be a bad option for the foreplane. Or on a smaller model just use 1/8 to 1/4 sheet surface depending on the model size and sand in a reasonable approximation of a Clark Y.
Old 06-19-2013, 04:15 PM
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Default RE: Foreplane to wing incedence on a canard

Thanks B Matthews and Alasdair,
The plan is to have a span of about 54.5 with the NACA 24016 as the Root and NACA 24011 as the tip rib as this seems to work well on my Ki 61 of the same size and seems to be the normal practice on its larger counter part.It has worked well on some of my other warbirds using other airfoils.

So I should figure on making it some sort of lifting foreplane with a few degrees of incidence. One question though, the addition of a moving control surface won't affect this? And the other question is should I concider some washout in the main wing or leave it do to the nose stalling first?

Tim
Old 06-20-2013, 01:46 AM
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Default RE: Foreplane to wing incedence on a canard


ORIGINAL: BMatthews
Alasdair, the 240xx series are a lower or neutral pitching moment style and should be fine for this sort of use. But I agree that making the fore plane with a postive camber airfoil would be a wise option. Tim something like a NACA 2410 would not be a bad option for the foreplane. Or on a smaller model just use 1/8 to 1/4 sheet surface depending on the model size and sand in a reasonable approximation of a Clark Y.
Yes I realise that the 5 digit series were designed for a low pitching moment, but it is still there, and still negative, so it loads the tinyforeplane a little
Compufoil gives Cmo as -0.013 and zero lift at -1.09 degrees

For a small electric model of the Shinden I would be tempted by something like an Eppler E182, but thickened up towards the root. It has Cmo of +0.006 and zero lift at -0.29 degrees, but its 1.7% camber will give a better CLmax than a symmetrical section

just BTW, I'm thinking of changing from symmetrical to NACA 130xx for my next Candel development
Old 06-20-2013, 02:32 AM
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Default RE: Foreplane to wing incedence on a canard


ORIGINAL: tdstaf
Thanks B Matthews and Alasdair,
The plan is to have a span of about 54.5 with the NACA 24016 as the Root and NACA 24011 as the tip rib as this seems to work well on my Ki 61 of the same size and seems to be the normal practice on its larger counter part.It has worked well on some of my other warbirds using other airfoils.
So I should figure on making it some sort of lifting foreplane with a few degrees of incidence. One question though, the addition of a moving control surface won't affect this? And the other question is should I concider some washout in the main wing or leave it do to the nose stalling first?
Tim
Tim, the Shinden is a very brave undertaking and I admire you for taking up the challenge.
Will your model be electric pusher, EDF, or will you use a micro turbine like Jetcat P-20 or a Kolibri?? Go on, be brave!!!

What about undercarriage? Will you miss it out (likeI would) but then how do you protect the fins under the wing?

From the "Incomplete Guide to airfoil usage...." at http://agert.homelinux.org/~fredrik/...t.html#canards
the full size Shinden's wing uses
"LB 510215/RAF-30 mod/NACA 23010"
I don't know the LB 510215, but the RAF30 is symmetrical 12.6% thick with max thickness at about 30%. My guess would be that's a root section and the 23010 (probably with 1 or 2 degrees washout) is the tip section.
The Incomplete Guide does not list the canard section

The photo on the Wikipedia page http://en.wikipedia.org/wiki/Kyushu_J7W makes the wing sections look quite thin. Are you sure you want to go to 16% thick on what should be a low Reynolds Number model? I'd stick to 12% at the root and 9 or 10% at the tip myself. And I'd be tempted to 1 degree, possibly 2 degrees washout.

On my club's website http://www20.brinkster.com/gvmac/ look on "Alasdair's Section" and you will find a Tail Lift spreadsheet that runs on Excel. Right click, Save as, and open it in Excel, and on the second tab at the bottom you will find that it caters for canards.
In the grey shaded area you change all the numbers in redto suit your model (numbers in black self calculate).
Using the gross foreplane area will give you a rough working CG, but try changing to the net area for a better idea of the foreplane lift coefficient for a range of overall aircraft Cl values (0 to 1.2 is a valid range for your model). At high speed you should get overall Cl 0.1 (jet) or 0.2 (E-prop) and the wing will stall in the 1.0 to 1.2 region.
[The nose area (difference between net and gross foreplane) helps destabilise the aircraft but doesn't help lift the nose up.]

Putting in rough figures from the scale drawing in BMathews' link makes me think your foreplane will need a Clf at high speed of 0.2 (jet) or 0.3 (prop). That implies a 2% cambered section with chordline at zero or +1.
BMathews' suggestion of NACA2410 (or my idea of a Clark Y thinned to 9% with 2.7% camber, and a flat bottom) would be good with the chordline at +1 or +2 (flat bottom at zero to wing).

If the top speed is high enough you might need a touch of down trim (up elevator) but it should be perfect in a fast cruise and keep the nose up long enough on landing, but at that low Reynolds number it will still stall before the wing.

Old 06-23-2013, 10:21 PM
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Default RE: Foreplane to wing incedence on a canard

Ok. MANY misconceptions of Canard being put forth here:

1) CG, NP, MAC for canard is calculated the same as for a tail dragger or a tricycle gear
Draw the diagram with the lift components and moment in the correct orientation and viola exact same simple equation. Get those signs right. How "touchy" your Canard will be the exact same as on a normal plane.

2) A high pitch moment airfoil is just fine on a canard.
There is 0 need to obtain a "zero" pitch airfoil section. Stating one needs this, doesn't understand point number 1).

3) Vhtc(Vertical tail coefficient) needs to be SUBSTANTIALLY increased over that of a rear empenage design. Rotaryphile posted this up above. This is especially true of dutch roll as posted above. Increase by 50% over a normal Vtc! otherwise you will be rolling your plane right... into.. the .... dirt. Been there, Done that. Ain't no fun. +++75% wouldn't be wrong either! 25% is TOO DANGED LOW. 50% minimum increase from scaled planes guys. If you can SWEEP your wings backwards to increase your Vtc; do so. Draw the diagram. You will quickly see why. A Yaw on a normal plane will have the entire fuselage length as a lever arm and likewise will have MUCH longer time in which to react, visual clues especially to ground based controlers, before a complete flat spin is initiated. On the canard, the visual clues just are not there. Add in most canard designs have very "thin" fuselages already further decreasing side area requisite to counter yaw. On a straight wing with NO sweep, you have 0, nada, zilch, lever arm until your plane is ALREADY IN a spin!

4) Canard aircraft suck at aerobatics unless you go for a completely Unstable setup. Even then they are hampered by the lack of rudder yaw control making them near useless as aerobatic planes. WOO HOO they can roll and loop.

5) A) Main reason no commercial aircraft will ever be built using canard configuration is that at cruise, the horizontal tail already has next to 0 lift on it. Its called wing sweep along with super critical airfoils that at cruise essentially when the whole planeform is added up, creates 0 moment and low drag. Modern commercial aircraft are essentially flying wings already except with a long tube and these additional blobs used for low speed maneuvers. Those blobs are already LOCKED out of the controls at high speed along with all aileron function. Small changes are created by changing the flap over the engine. Slightly larger changes are done via said flaps and tiny portions of the vertical horizontal stab down near the APU. We even were considering using steerable thrust on said APU on the 787, but the cost benefit was just not there when one already had to have partially moveable vertical stabilizer(rudder). It did provide a cruise boost though, though VERY small.
B) See 3 above for landing purposes = horrific drag penalties at high speed with the need for more area, though this could be done by wing tips that "bend up" for landing.
C) Sideslip landings with a canard airplane because of 3) above are VERY hard as the arm length requires far harder throws on the vertical stabilizers = need to be much stronger and likewise the gear needs to be beefier to throw the stabilizer around faster to compensate for the short lever arm to counter act yaw. This equals WEIGHT.
D) You see canard on delta wings(Eurofighter, Boeing Sonic Cruiser). The reasons should be readily apparent to most as delta wing configurations televons pretty much suck for longitudinal control
E) Vertical fins on wings put even higher stress on the wing adding Huge additional weight penalties.

There is one and only one requisite to a stable canard aircraft differentiating itself from others. Canard must STALL first. If main wing stalls before canard your plane falls out of the sky or at best does a loop before you can assume control again. As pointed out above, one can do this by using a thicker camber airfoil for main wing or by picking a different airfoil. You cannot do this via incidence ALONE. I will now discuss why.

Camber increases thickness of airfoil and will generate a lower angle and higher Cl at which it will stall(generally). THE CANARD airfoil therefore MUST be a thicker airfoil generally if you are staying in the same family, but there is one MAJOR caveat especially in RC problems. Reynolds number vastly changes in normal flight(high speed stall conditions) compared to landing. So staying in the same family is for all practical purposes impossible other than the fact that all RC airplanes are so overpowered in the end it doesn't really matter. So, in short, when the wing is at max, the canard is stalled and therefore you CANNOT STALL THE MAIN WING.

For instance you can place slats/flaps on canard as well, but the rotation angle for slats essentially means you cannot use them as the prop just shaved itself a couple inches shorter. Half extended slats on main wing combined with dual flaps on canard and main wing will work. Full slats on main could work as well along with half slats on canard if one wanted to do a real STOL version of a canard. It can be done. If you want to see pictures of such a plane let me know, I can go digging in my files. Video is VHS, so sorry, no can do. Plane easily took off in half the length when flapped and likewise SLOWED down on landing. Get ready for some interesting linkages on your canard though or placing the servo in the small canard.

Ok, why you cannot use incidence alone to prevent main wing stalling before canard. Under static conditions with a piece of paper and a pencil this would take care of the problem, but when doing a yo-yo this incidence difference can vanish. Think Landing here guys where high speed change in input is done. Can blow right past max lift stall angle on canard and go completely into separated flow lift/stall that will still achieve enough lift to increase AoA and stall the main wing. If one has two ways in which said canard stall first, then you are ahead of the game. It is certainly not a deal breaker. For near all RC airplanes, one can simply just add incidence to the canard and it will fly beautifully. You wouldn't see my butt flying in such a plane, but for RC purposes it is fine.
Old 06-24-2013, 01:38 AM
  #24  
alasdair
 
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Default RE: Foreplane to wing incedence on a canard

BFoote,
Reality check!!
tdstaf is building a Shinden. See post #16 photos

At 54.5" wingspan I'd estimate his foreplanechord to taperfrom 4.6 to 2.4 inches. At 30 mph its Renolds number will be 40k tip, 80k root.
Suggest a section, and a rigging angle, and tell us what its maximum lift coefftmight be.
Old 06-24-2013, 10:52 AM
  #25  
BMatthews
 
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Default RE: Foreplane to wing incedence on a canard

I wouldn't be too harsh there alasdair. BFoote raises some very pertinent canard points.

As in the cambered airfoil will work. My only reason for agreeing with the use of the original's lower pitching moment airfoil for the rear plane is that the negative pitching moment of a "regular" airfoil simply puts a greater load onto the fore plane. Which, as already pointed out, is pretty small in this particular case.

On the veritical fin issue there may be good reason for increasing the size of the twin fins over the original size. It's known that prop discs have an equivalent side area effect. And the more "solid" the disc due to using multiple blades the greater the virtual area effect. So switching from the original's 6 blade prop to a typical two blade model prop of smaller than scale diameter could well require the fins to be increased in area in order to make the model stable in yaw.

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