Tandem wing for high efficiency? Case Proteus

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Autodidact

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LS-1; http://www.worldofkrauss.com/foils/1810 -0.21Cm@10° -0.135@0° alpha0L=-5°
GU; http://www.worldofkrauss.com/foils/1391 -0.26Cm@10° -0.155@0° alpha0L=-6.5°

Original Quickie (single seat) template level lines:
E 1212 main wing
BL-10 = 0.46 degrees positive
BL-52 = 0.22 degrees negative
BL-100 = 1.9 degrees negative
LS-1 canard
BL-10 = 1.68 degrees positive
BL-51 = 0.49 degrees positive
BL-92 = 0.0 degrees
GU canard
BL-10 = 0.07 degrees positive
BL-49 = 0.22 degrees negative
Bl-88 = 0.74 degrees negative
As you can see, the GU (Glasgow University) airfoil has about 1.61° less
incidence than the LS-1 at what I'm assuming is 10% of the semi-span from the
canard's root. If you look at the charts for these two airfoils on World of
Krauss
you'll see that they have about that amount of difference in their
respective zero lift angles. The LS-1 airfoil has an alpha0L of approx. -5°
making the actual angle of incidence approx. 6.68°. The decalage measured from
the airfoils datum and not the zero lift line is actually pretty trivial and
is a result of individual airfoil charactaristics. The decalage is set by
computation and is what it will be depending on the needs of the design;
you can't copy it from one plane to another. The importance of the airfoil
chosen would be its lift/drag charactaristics since for a specific PLANFORM
and cg location, the angle of its zero lift line w/respect to the fuselage datum would
be about the same regardless of airfoil as evidenced in Hot Wings post (also partly dependent on the main wing's moment coefficient).

Here's an interesting article:
Design of two Airfoils for a Canard Airplane

I really think you should have started your own thread, since this one is about
whether the tandem wing is the best configuration for aircraft efficiency and
not about what airfoil is best for tandem wing efficiency. Perhaps if there is
some growth in the direction DangerZone has gone in the moderators will start
a new thread for us. This is an excellent subject in my opinion and I would
like to see a good discussion in a dedicated thread where it is not muddled by
older, semi-related questions.
 
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Apollo

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There's plenty of real world examples, the EZs, the Berkut, the Quickies, the Amsoil Racer or its never beaten rival the Beck Mahoney Sorceress, then the Dragonflies, Flying Fleas of all sorts or small less known tandem wings and canards, but not so many of them proved to be quite succesfull. The biggest problem was the same that Rutan faced, even with the best aerodynamicists and engineers he had trouble in finding the most efficient airfoil to use in a canard configuration. A combination of airfoils that would provide both a low stall speed and a very fast top speed, using all the advantages of the tandem/canard configuration AND have a high efficiency at the same time. So I was just wondering if there are any more people who found some good solutions to this challenge..?
Dangerzone, I've searched for a "better" airfoil than the Eppler 1230 used on the Long-EZ/Cozy. I used Airfoil Optimizer to identify possible replacements and then ran them thru Airplane PDQ. The modified E1230 is pretty close to ideal. I found airfoils that could increase cruise speed by as much as 10 kts, but they also raised the stall speed. The E1212 lowered the stall speed a couple knots but did not increase cruise speed. I analyzed dozens of candidates and there was no airfoil that could simultaneously increase cruise speed and reduce stall speed.

My solution was to design two separate airfoils: A laminar flow airfoil for the wing root and a turbulent flow airfoil for the wing tip. Each airfoil is customized for its operating RN. This was the only way I could achieve lower drag AND a lower stall speed. I'm working on a website that will provide more details - someday. If you haven't been to the UUIC website, they have a database (the Incomplete Guide to Airfoil Usage) that shows the airfoils used on various canard aircraft. Try this link:

The Incomplete Guide to Airfoil Usage
 

karoliina.t.salminen

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This question about designing a tandem wing airplane that has 65 km/h stall speed and can cruise 300 km/h in my opinion should go to a separate thread like someone else suggested, it would be interesting as such. Moderator feel free to move my comments there if such is created.

But to answer question, why different incidence angles: simple,
- the airfoils in question have different steepness of lift curve slope and the combination of the two wings needs
to stall so that the forward wing stalls always before main wing, and airfoil selection and wing geometry will
affect the incidence angles needed to satisfy this requirement.

And there is by the way no magic there and no magic airfoil combination that will make your requirements work.
To get stall speed low enough, you need to do large enough wing (both wings on tandem needs to be larger).
Large enough wing will produce some drag, and that may limit your cruise speed with the fixed power you have concluded to be available.

Also keep in mind: the Roncz airfoil for Cozy is antique. Roncz has developed since better airfoils. The Eppler airfoil is even more antique.
State of the art in section L/D is in the modern gliders at the moment.

With tandem wing you have one thing that you can do that you would avoid with conventional configuration:
In tandem configuration the forward wing can have very strong pitching moment, enabling high clmax for the forward wing and also you can operate the forward wing at high Cl at cruise. At higher Cl typically the L/D is higher on a strongly cambered airfoil. You can achieve rather high cruise L/D with the forward wing, but your rear wing will be in downwash of the forward wing and also the rear wing has Cl max limit because you can not use flaps on the rear wing. The total Clmax of the configuration is lower than the conventional or three surface configurations, therefore requiring you to create bigger wings to satisfy your stall speed requirement, which will result in more drag and to satisfy the cruise speed requirement with the fixed power available, you need to optimize the L as high as possible and the D as small as possible in the L/D.

For your low stall speed the lower Reynolds number needs to be also consideration, because at lower Re, your Clmax will be lower and section L/D is lower too and it may have implications for your airfoil selection.

I don't believe the RMT Bateleur is as good as advertised. Also it is not a tandem wing like Quickie or Proteus, looks like it is more or less delta with a trim canard.

The reason why some canards, such as Berkut, are fast, is simple:
- They are very small aircraft and they have small wetted area to drag around and at the same time relatively high engine power (like Berkut typically has). It is not the configuration that makes it cruise more than 200 kts, but simply a small plane has small wetted area. It is not because it is a canard, other configurations would result also small airplanes, which could also be fast with same design parameters.
- It does not mean that for example Berkut would be any bad aircraft, in fact the contrary, I would really love to have one. It would be a fun aircraft and it looks cool. Maybe not my ideal travel machine since I have used to that I can carry quite a bit stuff around. But there is no prop on the front spoiling the view and the performance is comparatively awesome (comparing to e.g. the Diamond that I fly). However, same performance could be achieved with a different configuration also on equally small and equally high power to weight airplane. If you park the Diamond and the Berkut side by side, you can quite clearly see that the Diamond is huge in comparison. Then you bring C172 to the side again, and it is even bigger (despite being smaller from inside than the Diamond). And if you park a Cozy to the side, it also is a small airplane - it is a Cozy airplane, not a big one. Big airplane, big wetted area, lots of drag, small airplane, low wetted area, less drag. However, there is no magic here either, scaling down is not as effective as it might look. If you want to know more, you can read the Austin's story (the maker of the X-plane, story is on the X-plane web page) about his Jet design and how he concluded that it is not worth it (with jet engine, in the small scale).

My original question about Proteus was that if there was a special corner case where the tandem wing would have been superior to conventional configuration, knowing that the total Clmax of the airplane will be lower and it will need a bigger wing. The original question was that what if it does not matter in certain conditions, such as at very high altitude where you a need large wing anyway and if you don't care about certain usual design parameters (like optimizing the stall speed - cruise speed -ratio). However, it was answered several times that the justification for this configuration really wasn't this. But at least Proteus proves one thing; it is possible to design an aircraft with this configuration that is good enough to fly at this very high altitude. However, it does not rule out that the same could have been done with other configurations as well. But still, there is something in Proteus, it makes me think of Pterodactyl, I was a dinosaur-fan when I was young. It even has the dihedral-anhedral change in the wing, almost like the flying dinosaur. The curved nose section especially makes it awesome sight. And it has two black eyes too (the circular windows). And when you look it upside down, interesting shapes. And if you look it right side up, and the nose only, it starts to look like a dog. Burt Rutan has always been doing interesting things on the styling side. And I really also like the last "window" on the right hand side of the Boomerang. Check it out, if you haven't looked closely.

As Apollo said above, to get most out of this configuration, you can't retrofit some airfoil on it, you have to design airfoils for this particular configuration and purpose taking most the out of it.

 

Tom Nalevanko

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...But there is no prop on the front spoiling the view...
As you have introduced aesthetics into the thread, I couldn't help from commenting on this. I fly quite a few different planes, some with tractor props, some not and I never felt that the prop spoils the view, at all. Usually, for views, I will be looking off to the side as I want clear air and blue sky up front so as not to hit anything.
 

Rick McWilliams

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Tandem wing configuration airplanes must have the forward wing at a much higher lift coefficient than the main wing. The Aerodynamic neutral point is about 1/3 of the way aft from the canard wing toward the main wing. The position depends on relative areas and aspect ratios. The center of gravity must be ahead of the neutral point for static longitudinal stability. The canard will normally use a highly cambered fully flapped wing section. The main wing will have much less camber and operate at a much lower lift coefficient. At minimum speed, stall, the canard wing might produce a CL=2 while the main wing will be at CL=0.8. It is just about impossible to design a tandem wing airplane where the main wing will stall first.
 

Rick McWilliams

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I love airplanes with good visibility. I fly a little seaplane that has a very low cut canopy that gives excellent forward, side and downward views. The view is not as good as my wifes little red Robinson helicopter. The R22 VNE is limited by the canopy deforming and inverting under air loads.

Forward propeller does not bother me it is the big engine or instrument panel. What were they thinking when they designed the C172 panel? I one time wanted a better view down and rolled my Christen Eagle inverted. It is very uncomfortable to look straight down when inverted. My face also turns red when inverted for more than a few seconds.
 

karoliina.t.salminen

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About aesthetics of forward visibility: the forward visibility has high impact on the view.
Flying the Diamond is more like computer game or adjusting some process machinery (when flying IFR), you look the instruments and then look out just to see if there is other traffic. I was flying ultralights (similar to US LSA) before and some of them had a better forward visibility than typical bigger planes do because it extends further down (lower instrument panel). From my experience, the vision around you, has impact on the enjoyability on the view. Similar to on a house, big windows make a big difference compared to small windows.

I also shoot videos from the plane, and due to rolling shutter of CMOS sensor, the rotating propeller in front view is a obstacle, especially when coming down to landing and the prop speed decreases. The long shutter speed (motion blur) helps, but does not fix the problem. The prop is an obstacle in any case, and having engine and prop in front, typically makes the instrument panel layout high and rules out unconventional layouts for "panel" where you would have better forward visibility both down and up, because it does not need a Sherlock to look how cars have evolved out of "panel" idea many tens of years ago to a instrument deck that is aesthetically more pleasing and also provides better visibility outside which increases safety and enjoyability of the view, especially when flying IFR over the clouds. They are absolutely beautiful, and the whole impact of this beauty can not be seen when looking to the side, and if you look too much to the side, you will lose your altitude assignment unless you are not really flying but riding along, letting the autopilot fly (I usually fly by hand (when I don't need to engage autopilot due to other tasks) despite having autopilot, because I have paid a lot to fly the plane and not just ride along). And in many cases, it is important to see also down front and not only up front, traffic might be below you on front, if we rule aesthetics out.

Ideal view has 360 degree obstacle free view out. It is impossible. I am looking for better compromise, and already for that purpose, no prop in the front is the conclusion. Therefore my concept, regardless if it is tandem, conventional configuration or something else, it will not have propeller on front of the cockpit and it will not have wing above the cockpit (like Cessna) such way that it would block the view to left up and right up. I want to see up also to maximum number of directions, not only front up. For my personal aesthetics, even if flying IFR, this is important, one of the reasons to fly in the first place (it is for fun, and for the enjoyment of the view really), and IFR is in many cases in beautiful weather above the clouds, since it would be moron factor and population control to stay inside the cloud for long periods of time if I borrow words from my mentor from North Atlantic trip, and I also have three experiences with icing already with my relatively short history of spending time inside cloud, even with this rule "stay inside cloud minimum time", so even for IFR flight, forward visibility and aesthetics of the view has paramount importance on the desirability of the airplane as a product, and I think this is one of the contributing factor why it is not so desirable for general public, and why there is a constant decline on number of pilots, many current airplanes simply don't compare to the aesthetics of other vehicles of today, and that is not because of aerodynamics, but because of shaping structural blocks together purely from engineering perspective instead of any understanding on industrial design. To revitalize personal aviation, breakthroughs are needed not only in efficiency, but also in the desirability of the airplane as a product.

There are simple comparison for why: After flying the quite modern better class certified general aviation plane around, and then driving home from airport with the Toyota Prius, the Prius is a whole lot different experience than the plane. The car is so smooth, with so great visibility forward that the plane feels like some bulldozer in comparison and the rattle of the Lycoming feels like a bad joke of last century. Still it is the best plane I can fly at the moment, so I don't complain, but I want to do better myself.
 
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Tom Nalevanko

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Frank Thalman thought the same way you do, 40+ years ago. Prop up front, but no engine or panel blocking forward view....

This aircraft had very good performance. If Frank would only not have been flying around in snowstorms, we all might know it today.
 

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DangerZone

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I doubt. Such reduction in induced drag simply mean that the eqivalent span of a monoplane is increased by a factor of 1.29. One can imagine such result only if the interaction of the downwash fields of two equal wings, producing equal lifts, is almost completely suppressed. This means that these tandem wings must be greatly displaced both vertically and horizontally, by a distance comparable with a semispan. I cannot image a practical airplane with such extreme layout.
Further, one should judge the structural weight penalty against an equivalent monoiplane wing. A single wing of twice the area, same airfoil thickness and aspect ratio most likely will be lighter than two equal tandem wings, but its span will be larger by a factor of 1.41, and the induced drag will be further reduced. A conventional configuration is again a winner.
Good point. Yet, is the conventional configuration a winner because it is more efficient or because the tandem configuration is not yet explored/optimized as much as it could be..?

When Arnold compared his AR-5 and the EZ he concluded that the reason for AR-5's better efficiency is reduced interference drag. So, if that is the case and someone builds a tandem wing configuration with minimal induced drag and similar weight&power, would that be good to compare efficiencies..?

Or, the tandem/canard wing configuration of the Beck Mahoney Sorceress which Rutan tried to beat with the Amsoil Racer showed that there is another thing that even great minds miss. Could it be that the idea of the conventional configuration being more efficient is just because noone exploited the tandem/canard configuration to its fullest maximum yet..?
 

DangerZone

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OK I remember I did a lot research to build a plane a few years ago, and came to the conclusion that 3 degrees was pretty standard. I tried to find the exact decalage just now on Google search but couln't find for you (of EZs Berkut and Cozy. )
However I can tell you this. Once you have the plane flying, the position of the elevator will give you a hint of if you got it right. If the elevator is down a few degrees, then you have not enough incindence.(this might equate to a very small adjustment, like .2 degrees)
So whatever you decide to incorporate, test fly the airplane, but don't mess around with slow flight untill you take a look at the elevator angle, in level normal flight. You might want to install the canard with keeping in mind you may change the angle later. In other words don't do 100 hours of glossy finish all around it.
But here's another thing which makes this less critical than you may think; If a too small of decalage causes you to use more elevator, the chances are you are going to have an even earlier trailing edge stall (on the canard) than if you had more decalage. So in my mind it all sort evens out. I screwed around with models and found it was actually very hard to make the rear wing stall first on a plane that is actually flyable. But of course you eventually want to adjust it so it has nuetral elevator in normal level flight.
I wish i could give you the exact degrees for those planes, as that would be nice. Hope the the above stuff helps.
Yes, it all sorts out even. Yet, why do I have the impression that it all sorts out even better on tandem wings than on canards with a bigger wing/canard disparity..?
 

DangerZone

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Dangerzone, I've searched for a "better" airfoil than the Eppler 1230 used on the Long-EZ/Cozy. I used Airfoil Optimizer to identify possible replacements and then ran them thru Airplane PDQ. The modified E1230 is pretty close to ideal. I found airfoils that could increase cruise speed by as much as 10 kts, but they also raised the stall speed. The E1212 lowered the stall speed a couple knots but did not increase cruise speed. I analyzed dozens of candidates and there was no airfoil that could simultaneously increase cruise speed and reduce stall speed.

My solution was to design two separate airfoils: A laminar flow airfoil for the wing root and a turbulent flow airfoil for the wing tip. Each airfoil is customized for its operating RN. This was the only way I could achieve lower drag AND a lower stall speed. I'm working on a website that will provide more details - someday. If you haven't been to the UUIC website, they have a database (the Incomplete Guide to Airfoil Usage) that shows the airfoils used on various canard aircraft. Try this link:

The Incomplete Guide to Airfoil Usage
Yes, I have seen the UUIC website and it is a good source of basic info on most airfoils. Did you also notice that there is a ton of good conventional configuration airfoils yet only 3 or 4 good tandem/canard ones..?
 

DangerZone

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This question about designing a tandem wing airplane that has 65 km/h stall speed and can cruise 300 km/h in my opinion should go to a separate thread like someone else suggested, it would be interesting as such. Moderator feel free to move my comments there if such is created.
Ok. I wasn't asking about designing a tandem wing but about highly efficient airfoils of tandem wing aircraft. The question of 'which airfoil' just emphasizes the fact that there are less such airfoils than fingers on one hand. The specifications I mentioned are quite typical for most ultralights so the question was just a practical one, one familiar to me because of a similar project I have been working on. Please don't mind if I jumped into your interesting thread or if I lack knowledge how this forum community usually posts, I will hopefully learn in time.
 

orion

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The canard/tandem has been explored ad nauseam by small aircraft manufacturers and by the mainstream industry as well. Outside of the very few and limited benefits that I mentioned earlier, the only benefit to general aviation products is simply that the configuration allows designers to design an airplane that does not look like every other airplane on the tarmac. But this does not require a deep understanding of aircraft design theory - just requires a good view and understanding of flows and interactions, as well as practical application and aircraft operations.

But all these discussions must be held in context. For instance, if you're designing a simple light airframe such as an ultralight, the efficiency loss of the canard/tandem versus any benefits of a more conventional arrangement are almost negligible so the bottom line there is simply do what you like. If you like the tandem and are attracted to the lines or configurational possibilities then that particular classification of airplane will not suffer to any measurable degree as a function of that choice.

If however you're looking at more performance and/or variability of operations, then the canard/tandem is certainly not optimum. But again, if you like it and are willing to live with a few minor compromises (longer paved runways, flat unobstructed approaches, higher landing speeds, shorter allowable CG range, etc.), then the canard will offer you a chance to stay on the unique side of things. It is a configurational preference and as the designer, if it meets your goals, then the design has merit.
 

DangerZone

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LS-1; Airfoil Investigation Database - Showing NASA/LANGLEY LS(1)-0417 (GA(W)-1) -0.21Cm@10° -0.135@0° alpha0L=-5°
GU; Airfoil Investigation Database - Showing UNIVERSITY OF GLASGOW GU25-5(11)8 -0.26Cm@10° -0.155@0° alpha0L=-6.5°



Design of two Airfoils for a Canard Airplane

I really think you should have started your own thread, since this one is about
whether the tandem wing is the best configuration for aircraft efficiency and
not about what airfoil is best for tandem wing efficiency. Perhaps if there is
some growth in the direction DangerZone has gone in the moderators will start
a new thread for us. This is an excellent subject in my opinion and I would
like to see a good discussion in a dedicated thread where it is not muddled by
older, semi-related questions.
Am I in minority seeing a strong correlation between the two..?

The fascinating fact that there are more than 2000 conventional and less than 20 tandem/canard proven airfoils gives
an idea how conclusive such an answer would be. Combine that with basing the conclusion only on the case of Proteus
without considering other practical tandem/canard aircraft and everyone who understands elementary logic sees what
kind of result may outcome.

Ok, you are right. I guess I should have opened another thread but thought smart people here would concentrate on
the matter rather than the form. Would you mind if we proceed with the topic now and have a wider view?
 

DangerZone

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The canard/tandem has been explored ad nauseam by small aircraft manufacturers and by the mainstream industry as well. Outside of the very few and limited benefits that I mentioned earlier, the only benefit to general aviation products is simply that the configuration allows designers to design an airplane that does not look like every other airplane on the tarmac. But this does not require a deep understanding of aircraft design theory - just requires a good view and understanding of flows and interactions, as well as practical application and aircraft operations.

But all these discussions must be held in context. For instance, if you're designing a simple light airframe such as an ultralight, the efficiency loss of the canard/tandem versus any benefits of a more conventional arrangement are almost negligible so the bottom line there is simply do what you like. If you like the tandem and are attracted to the lines or configurational possibilities then that particular classification of airplane will not suffer to any measurable degree as a function of that choice.

If however you're looking at more performance and/or variability of operations, then the canard/tandem is certainly not optimum. But again, if you like it and are willing to live with a few minor compromises (longer paved runways, flat unobstructed approaches, higher landing speeds, shorter allowable CG range, etc.), then the canard will offer you a chance to stay on the unique side of things. It is a configurational preference and as the designer, if it meets your goals, then the design has merit.
Isn't the canard not just optimum but superior to conventional airplanes when it comes to high variability operations of modern jet fighters..?
 

Autodidact

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Ok, you are right. I guess I should have opened another thread but thought smart people here would concentrate on the matter rather than the form. Would you mind if we proceed with the topic now and have a wider view?
It's not for me to "mind", I just thought you would get a better hearing with a new thread as that is how it is usually done and often the moderators do split something like this into a new one, keeps things organized. Whatever works out best is fine with me, though. And welcome to the forum, by the way.
 

orion

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Isn't the canard not just optimum but superior to conventional airplanes when it comes to high variability operations of modern jet fighters..?
It really depends on what characteristic you're after but in general yes, you are correct. I touched upon that earlier in this discussion (see post #12). But the benefit is not so much due to mission variability but more so a benefit to agility and energy management.
 

Autodidact

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I suspect you could design a pretty decent canard using a very ordinary symmetrical airfoil like the NACA 0012 on both wings. But that doesn't mean it couldn't be improved with more suitable airfoils. Karoliina's insight in her original post in that an airfoil with a very high pitching moment works well as a canard foil is interesting because the GAW series airfoil is usually thought of as a poor choice for general aviation "conventional" aircraft because it has the high pitching moment but is apparently a reasonable choice for a canard. The other half of the problem is the main wing; part of it is in the down wash of the canard and part is in the free stream and there is part in the transition between the two. I think Apollo made a crucial point about designing the wing with different airfoils for the inner section and outer section if for no other reason than to keep the geometric twist to a minimum.

A wing with a plain flap, which is what a Rutan type canard foil is, has a limit to the angle of attack it can reach before stalling. The more flap (in this case, elevator) you crank in, the less alpha you can have before the canard stalls. I wonder if you could have a canard foil with a very high lift flap such as a fowler for the elevator, and at the same time be able to greatly reduce it's angle of attack so that you could get more AOA to the back wing and thus a higher overall CLmax, i.e., be able to reconfigure the aircraft so as to optimize it for both cruising and low speed flight? You'd probably have to add a small amount of flap to the rear wing as well to keep it from stalling before the front and that would reduce it's max alpha as well. I'm sure all of my musings above have been well examined by others before I even thought of them!
 
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orion

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A wing with a plain flap, which is what a Rutan type canard foil is, has a limit to the angle of attack it can reach before stalling. The more flap (in this case, elevator) you crank in, the less alpha you can have before the canard stalls. I wonder if you could have a canard foil with a very high lift flap such as a fowler for the elevator, and at the same time be able to greatly reduce it's angle of attack so that you could get more AOA to the back wing and thus a higher overall CLmax, i.e., be able to reconfigure the aircraft so as to optimize it for both cruising and low speed flight? You'd probably have to add a small amount of flap to the rear wing as well to keep it from stalling before the front and that would reduce it's max alpha as well. I'm sure all of my musings above have been well examined by others before I even thought of them!
Dangerous thought process here. First of all, the moment of the section really has little to do with all this so we can pretty much ignore all that. Yes, it's a part of the stability equation but the mechanism at work here is simply that you are trying to maximize the difference between the stall angle of the canard and the stall angle of the main wing. What complicates this whole process is that the inboard part of the main wing is in the down-wash field of the canard so some of the design elements that have to be considered get a bit involved since what this is doing is essentially loading up the tips more than the root. That could not only lead to early stall back there, it could also lead to tip stall - although on second thought in this case it's not that much a consideration since any stall on the main wing will put it into an unrecoverable tumble.

In developing a design where the canard stalls before the main wing, it is absolutely incorrect to put a flap on the main wing "to keep it from stalling" since the addition of the flap will reduce its stall angle and thus negate the whole process, making the aircraft actually more dangerous. The simple fact is that you actually do not want "more AOA to the back wing" since you do not want to get it anywhere near the stall condition. This is the very root of what makes the canard less efficient and functional than a conventional layout and trying to defeat it, especially in an amateur environment, is a road to disaster.
 
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