New canard designs?

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Joe T.

Member
Joined
Jan 27, 2011
Messages
6
Location
Wichita, KS
Canard designs require more effort to optimize performance than a conventional design since there has been virtually no real effort expened in understadning canard aerodynamics. How many canards designs are intensely studied in school? I believe this is a challenge because most folks follow - they do not lead. Most aero engineers want to optimize a well understood design concept. There is not much clean sheet of paper out there. Therefore, every new airplane looks like a standard configuration - main wing forward, aft tail plane.

One of the challenges for a canard concept to meet the LSA rules - especially stall - is to design a configuration that takes the main wing out of the downwash and vortex of the canard. It can be done, but the result is, well, unique. OMAC tried this with the Laser 300 and JetCruzer. If you want to see something even stranger, Google Mig-8.

A Longeze co-planar type design has significant impact on the main wing due to the downwash of the canard. Therefore, the main wing is not creating as much lift as the airfoil utilized could produce. The main wing area which is washed by the canard is effectively at a lower AoA than the outboard sections of the wing. So, one must consider that in the design effort.

Enough for today.

Joe T.
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
Canard designs require more effort to optimize performance than a conventional design since there has been virtually no real effort expened in understadning canard aerodynamics. How many canards designs are intensely studied in school? I believe this is a challenge because most folks follow - they do not lead. Most aero engineers want to optimize a well understood design concept. There is not much clean sheet of paper out there. Therefore, every new airplane looks like a standard configuration - main wing forward, aft tail plane.
I fully agree with your "everybody follows the other guys", meaning all aircraft are pretty much the same.

But I don't think canards should necessarily be given more attention and there's plenty of research for them, though usually at a higher (jet) level. Canards have two fundamental drawbacks; the wing can't make max lift (thus you need a larger/better wing or higher approach/landing speeds) and it's not easy to flap a wing.

Both problems are inherent to a canard and pretty fundamental, unless you go to FBW. As long as canards don't have other advantages (they do, easy pusher integration and better visibility for example) I personally don't see the point in canards in GA, unless you find the advantages very important.

Just to give you an idea; the Dyn'aero MLA's achieve a Clmax of over 3. Most small canards won't go past 1.5
A wing that's twice as large pretty much negates the advantages of a canard.
 

Joe T.

Member
Joined
Jan 27, 2011
Messages
6
Location
Wichita, KS
Auto,

Your comments are typical of the ones I have heard from the aero weenies (a term of endearment!) GA folks I have worked recently. Having spent a lot of my previous career at the Skunk Works, where the 'challenge' is an opportunity to do something radical (and work 80+ hours a week for 40 hours pay!), I find that odd. An optimized canard design is just an engineering challenge. This separates the engineers from the ‘technicians.’ Nothing wrong with technicians, but society is moved forward by engineers. Admittedly, there is not a lot of data available for 'easy' canard designs, compared to 'conventional' designs. Hence, 'technicians' design the vast majority of today’s aircraft, not real visionary engineers.

Just suppose you could come up with a configuration that allows the 'main wing' to work as efficiently as the wing on, say, a C-150 (we are talking about LSA's right now). If you have a main wing out of the influence of the canard, then there is NO reason a flap cannot work as well on the canard design as a 'conventional' design. Again, look at the MIG 8 (ugly as hell, but apparently a great little airplane). I agree that the canard will have to be limited in AoA before the main wing, but one can choose airfoil designs that allow a sharp break with the canard and a much more ‘rounded’ Cl / alpha for the main wing. Thus, two degrees ahead of Cl max for the main wing, where the canard would ‘break,’ results in little lose of lift for the main wing. This may require a graphic to illustrate.

So, how does one eliminate the canard effect on the main wing? A rough (very rough) rule of thumb is that the canard should be about 4' below the main wing (x-axis) and about 6' ahead of the main wing (y-axis). My folks are working that problem today. CFD analysis in a few weeks. Scaled model tests to follow. so, far, looks very promising - thanks Mig-8 and OMAC.

What about a 'tandem' wing? That is just a 'canard' design where the canard carries more of the lift than a in a typical Rutan / Shinden / Ascender design. This opens up even more design space. I am tending towards the tandem wing concept with about 70% lift from the main wing and 30% from the canard. Analysis in work - - - - -

So, enough for tonight.

Enjoy and remember - - -

Life is short, enjoy every moment.

Joe T.
 
Last edited:

Kristoffon

Well-Known Member
Joined
Sep 4, 2009
Messages
348
Location
Brazil
Just suppose you could come up with a configuration that allows the 'main wing' to work as efficiently as the wing on, say, a C-150 (we are talking about LSA's right now). If you have a main wing out of the influence of the canard, then there is NO reason a flap cannot work as well on the canard design as a 'conventional' design.
AFAIK the reason few canards have flaps is that the pitching moment created by the flaps either requires a huge canard therefore inefficient in cruise or that the canard too be flapped which is a huge safety issue in case the main wing flaps extend but the canard's fail to extend for whatever reason.

What about a 'tandem' wing? That is just a 'canard' design where the canard carries more of the lift than a in a typical Rutan / Shinden / Ascender design. This opens up even more design space. I am tending towards the tandem wing concept with about 70% lift from the main wing and 30% from the canard. Analysis in work - - - - -
Tandem wings make very inefficient aircraft. The downwash of the first wing leads the second wing to fly on a downward airstream. There's a reason we don't see lots of them.

Hence, 'technicians' design the vast majority of today’s aircraft, not real visionary engineers.
I, as an engineer, can't take that seriously. There's a reason every aircraft looks pretty much the same: it's what works. In doing my job which so far led me to design several different machines they often look similar to other machines that do the same job. That's because as an engineer it's my job to get to the goal in the least time and money. Not to dream all day about some miraculous thingy that might never work while a workable solution stares at my face.

Of course going into uncharted waters is entirely justified - when both the current solutions aren't suitable and we have the time and the budget to come up with a solution often through trial and error. I believe most people here will agree with me that spending time on the air today is superior to daydreaming about some wonderful aircraft that might take 10 years to build.

You got us engineers confused with someone else, sorry.
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,983
Location
Rocky Mountains
Cat on the keyboard. Now I have to type this all a second time.:ermm: Bad Nessie!

I believe most people here will agree with me that spending time on the air today is superior to daydreaming about some wonderful aircraft that might take 10 years to build.

I'm one of the minority that doesn't share your view. If simply flying was my goal I'd be out flying a spam can.:tired:

Please don't take offense at Joe T's comments. I agree with him 100% but unfortunately our English language just doesn't have words that convey what he is saying in a simple way. I'll try:

A committee of engineers will generally come up with a workable solution to a problem. they take what is known with a high degree of certainty and mold that knowledge into a new product. they make the world go around on a daily basis. They can make new things.

Joe would call these people "Technicians"

An artist, for lack of a better word, are those engineers that have a higher level of curiosity and imagination. They are the ones that are always asking "why not?" or "what would happen if we try this?" They tend to not to produce as much marketable "things".

They are also the ones that are responsible for developing the ideas that the next generation of "technicians" will use to build better "things"

Joe would call these people "Engineers"

The world will survive with only the former, but without the later will never advance.

I've been both in my life. Being a "technician" is boring. :lick:

I've been told 3 times on this forum by engineers with more experience in their field, and higher levels of classical education, that what I was proposing was unworkable. In 2 cases they may be correct.
 

WonderousMountain

Well-Known Member
Joined
Apr 10, 2010
Messages
2,438
Location
Clatsop, Or
I've been told what I'm proposing won't work. Right now I'm not ready to bet my life on it. That doesn't mean they're right, only that I need more budget and time to see it through. So I will make something conventional-drats.

As far as canards go, we have a long tradition of comparing apples to oranges here and are not about to stop. The only way to compare them is devising a non biased mission, and seeing what people come out with. Even then, it will be limited by peoples understanding, and abilities.

The best way to comprehend aircraft is probably to fly them. Designing from the standpoint of a landlubber has been absurdly difficult. The best way to comprehend structures is to use/destroy them.
How come aircraft don't have crash tests like cars ?)

Some of the true innovators are on this site. And we would never make it without those technicians.


Happy building,

Wonderous Mountain
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
Your comments are typical of the ones I have heard from the aero weenies (a term of endearment!) GA folks I have worked recently. Having spent a lot of my previous career at the Skunk Works, where the 'challenge' is an opportunity to do something radical (and work 80+ hours a week for 40 hours pay!), I find that odd. An optimized canard design is just an engineering challenge.

And that engineering challenge will only be solved if you understand the basics. The 2 properties I mentioned are two of those basics of canards and instead of "odd", I'd say that understanding them is a requirement.

Also, your text shows some misunderstandings about canards, but Kristoffon addressed those already. No pun intended, but if you want to do "revolutionary" things; a good understanding is the first step. The one thing Johnson, Rutan and half a dozen of other **** brilliant guys shared was a good understanding of the fundamentals of aero, structures, control & stability and so on.

As for there not having been significant research; well, there certainly is. Point is though, that a canard isn't fundamentally different from another aircraft. Wake interference, stability equations and all the other stuff is exactly the same, though sometimes the signs are reversed. The only things that aren't available at our level (non-NASA) are maybe canard-vortex interference.
 

Joe T.

Member
Joined
Jan 27, 2011
Messages
6
Location
Wichita, KS
Kristoffon,

Suppose it is 1976 and you have only worked on conventional arcraft designs. Now, your boss comes to you and all of the folks at your design company, and says we have to design something that defeats radar. Some crazy guy, Like Denys Overholser, gives you some design guidelines (facets, strict edge alignment, nozzle aspect ratio, inlet grids, etc.). What are you going to do?

I strongly suspect, from your response, that you are truly a follower and would esign a 'stealth' aircraft not unlike what was proposed by General Dynamics / Ft. Worth, Grumman, Vought, or Boeing - a conventional, aerodynamically safe airplane. Not a stealthy aircraft. In other words, here is what works, live with it regardless of whether or not it is adesign meeting the CUSOTMER'S requirements.

It takes a special group of highly motivated and risk taking individuals to really start from a clean sheet of paper and develop a totally new concept, or make an obscure concept work / optimized (remember the Lipisch deltas?). I contend that the canrad concept has not really been 'optimized.' If you truly believe that is not the case, give some examples of intensive design effort and the test results. Don't quote data / info based upon conventional aircraft design. Not relatent.

Enough for tonight,
Joe T.
 

Joe T.

Member
Joined
Jan 27, 2011
Messages
6
Location
Wichita, KS
Hot Wings,

You are very close to what I am trying to convey - but I may not be communicating well.

Most design organizations are very conservative. They do what has been done before - only a little better as their design tools allow. Hence, my term of 'technicians.'

I had the rare fortune of working a long time at the Skunk Works. The old Skunk Works, not today's aberration, truly valued ingenuity and inventiveness. Nothing was considered outside of the box. Each new program had real requirements and the solution was usually totally different from anything previously developed. Look at their legacy (some great, a few not so great. You have to take risks to expand the envelop - frowned upon today): U-2, SR-71, F-117, DarkStar, Single Stage to Orbit (I can't remember the name we had for that vehicle), YF-22 and F-22 and YF-35. Not a bad record. None were clones of a previous design (OK, F-35 has a lot of F-22 technology).

The old Skunks who designed the U-2, SR-71, F-117, YF-22, and Darkstar, were engineers. Each design was unique and truly 'out of the box.' You can't say that for Cessna, Lear, Boeing, Bombardier, Embraer, or Airbus. A tube with wings is a tube with wings.

Good night,
Joe T.
 

WonderousMountain

Well-Known Member
Joined
Apr 10, 2010
Messages
2,438
Location
Clatsop, Or
Most people are still afraid to fly in tubes with wings. Do you expect any of those companies to make something radical? It would take twenty years of cut rate prices before the public would feel comfortable. All those planes you mentioned seem like military designs. As such it's another apples to coconuts debate.

Although, there's probably a lot of highly educated engineers not living up to their potential. Question is this. How does this differ from ever other profession on the face of the planet? Very few accomplish everything they set out to do. And sometime it's hard to get through a day without crying.

I'm sick of it. Why don't you set up a place for designers to excel-if you care about it so much.
I spent all my money on a similar pursuit to empower those I care about. When we're passionate about something we pour everything we have into it. That's as valuable to the world/people/yourself as overworking on a neat project.

Bitter encouragement,

Wonderous Mountain
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
It takes a special group of highly motivated and risk taking individuals to really start from a clean sheet of paper and develop a totally new concept, or make an obscure concept work / optimized (remember the Lipisch deltas?). I contend that the canrad concept has not really been 'optimized.'
You keep telling this. What is not known about canards, apart from the vortex interactions for extremely high aoa flight?
Every aero formula, stability derivative or flight envelope calculation is just as valid for a 3-surface, canard or conventional configuration. They really aren't anything special and we certainly don't lack any knowledge of them. Really, they simply aren't any better. Yeah, a canard can lift on both areas. So can many conventional aircraft and they can have a high-lift wing...

Ask yourself this. Both the sailplane folks and the UAV boom have not seen any serious developments in canards. Both areas are known to be rather revolutionary and far from conservative. Look at the Reaper or a sailplane. Both would benefit from a canard configuration (laminar flow and engine placement). Neither uses them. Been tried, didn't work.

Don't get me wrong, canards in our genre (GA) certainly have their merits. But they also have some serious drawbacks and it looks like that's the reason they're not as popular as conventional aircraft.
 

Kristoffon

Well-Known Member
Joined
Sep 4, 2009
Messages
348
Location
Brazil
Kristoffon,

Suppose it is 1976 and you have only worked on conventional arcraft designs. Now, your boss comes to you and all of the folks at your design company, and says we have to design something that defeats radar. Some crazy guy, Like Denys Overholser, gives you some design guidelines (facets, strict edge alignment, nozzle aspect ratio, inlet grids, etc.). What are you going to do?

I strongly suspect, from your response, that you are truly a follower and would esign a 'stealth' aircraft not unlike what was proposed by General Dynamics / Ft. Worth, Grumman, Vought, or Boeing - a conventional, aerodynamically safe airplane. Not a stealthy aircraft. In other words, here is what works, live with it regardless of whether or not it is adesign meeting the CUSOTMER'S requirements.
This is half correct. I would indeed try for a conventional aircraft first. However the customer must have specified what constitutes a stealth aircraft for him. So if I met with success in my conventional stealth aircraft design this is great. However if that wasn't the case I'd be forced to look for unconventional means to achieve it.

Maybe Hot Wings understood us a little better. If you want to do design for design's sake go ahead. If however my goal is to get an aircraft in the air, with my budged constrained by not being filthy rich myself, don't expect me to go looking into unproven technology when the current one fits the bill.

It takes a special group of highly motivated and risk taking individuals to really start from a clean sheet of paper and develop a totally new concept, or make an obscure concept work / optimized (remember the Lipisch deltas?). I contend that the canrad concept has not really been 'optimized.' If you truly believe that is not the case, give some examples of intensive design effort and the test results. Don't quote data / info based upon conventional aircraft design. Not relatent.
My knowledge of aircraft design doesn't go that far. I do know however that quite a few successful canards were built, some with big budgets (Starship), and common sense suggests that lots of potential design improvements were looked into.

As I said in my first reply "going into uncharted waters is entirely justified - when both the current solutions aren't suitable and we have the time and the budget to come up with a solution often through trial and error". So if you believe there's gold to be found in this particular rainbow, and you have the cash to put into it, by all means go ahead.
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,983
Location
Rocky Mountains

Maybe Hot Wings understood us a little better.

I suspect that we each would agree on more than we disagree. Language has it's limits and gets further compromised by the bits of interaction we are forced to use in this forum.

My first major in college was in architecture. I switched when it became apparent that if I wanted to make any money I'd either have to draw the same old box with slightly different dimensions or find a way to attract customers with enough money to let me be creative. I'm just not enough of a people person for that and switched to Organic chem. Those people that call themselves "developers" when they build another 80 acres of condos aren't "developers", the are "expanders". Just more of the same, with maybe slightly better insulation or counter tops than the last batch. I think the analogy is relevant to this particular discussion.

Trying to get something novel approved by a building and planning commission staffed by people that never took an engineering course in their life is not my idea of fun. I build home built airplanes to satisfy my creative needs, thus I have little interest in what is well proven or common. If I had to make my living designing aircraft I'd probably have a very different set of parameters to work by.

Figuring out a way to build a tandem wing that can generate a Cl of 2.0+? That is a project I find interesting, even if it takes 3 times as long to develop as a conventional design with the same performance.

I like the visibility from the cockpit of a tandem and am willing to trade a few percent in cruise speed for that feature. I would like a better spread between landing and cruise speed than is now available and think significant improvement is possible.
 

topspeed100

Banned
Joined
May 4, 2009
Messages
4,063
Location
Oulu/Finland
Meeting the stall speed requirement seems to be tough enough even for people like Vans and that is using a conventional flapped wing that they take all the way to stall. The need for the canard to be angle of attack limited, compared to the main wing, means that all forms of high lift devices on the main wing are out, due to the complication of trying to apply high lift devices simultaneously in a balanced fashion on 2 different lifting surfaces.

While a canard could be built to meet the requirement, would it be viable ? If the span required is 35 ft vs 26.75, that is going to take a lot of material to build. How would you like the view out front if you needed such a long span canard ? How do you think it would perform in a crosswind with the canard low in front to try to improve forward vision ?

Generally, most canards have been built "hot". They have tiny wings and canards for going really fast and economical cruise. A pusher configuration is commonly used to avoid the complication of the prop wash influencing the lift characteristics of the Canard. But as reality shows, the pusher configuration together with the relatively fragile landing gear and high landing speeds makes walking away from off airport pavement an unlikely affair.

Rutan was king of the canard design and he has basically withdrawn from this configuration. The new work he does is all conventional.

Rutan still is a KING in canard designs...and unconventional designs overall.

Ares was a beautiful assymmetrical MUDFIGHTER..possibly not very practical in attack role but nice looking.

I have two question on my newest design.

Is the landing gear workable..second is the 4 m long flap system ok ?

http://3.bp.blogspot.com/-oJIB0n1T4D8/UO2iU3AUNSI/AAAAAAAABu0/1WLpjKkDrSc/s1600/V-TRIKE-+AERO2_45.JPG
 

ultralajt

Well-Known Member
Joined
May 9, 2009
Messages
1,575
Location
Slovenia
Alright then gentlemens, I give you new canard design! :)

I use a coffe break to make this sketch. I dont want to design something real like that as I am not fan of the canards, but I want to sketch something new..I think I managed.
Dont bother wit cooling air intake location... was just my instant vision....could be different.
Dont bother also with obvious tail heavy apearance. Wing can be moved to match with proper CG.. or wing tips can be sweept backwards a bit...

But it is really new? Did you see anything similar with "split" canards alerady?


new canard 001.jpg

I see some benefits from that layout:
- better view forward
- when aproaching to the stall of canards, downwash will hit outer wing panels and lowering their AoA, so ailerons will work good and wingtips will not stall instantly due aileron acutating.
- main landing gear could be installed inside canard booms in the main wing.
- Canards could be mounted with negative dihedral, in line of pilot sight, so minimal area will obstruct pilots view..actually no canard area will be visible from the cockpit...


What do you think?
Go! Dont be affraid to express your opinions!

Aerodynamic thoughts, structural thougts..

I wonder what surprises I am waiting... :)

Mitja
 
Last edited:

Hugh Lorimer

Well-Known Member
Joined
Feb 14, 2008
Messages
298
Location
Stair, Ayrshire, Scotland.
So the question I have is what kind of flying qualities were actually achieved. There is no info listed regarding the performance of any of the designs. I see the British ultralight class requires a 35kt stall speed, thus harder to achieve than our LSA requirement. The all flying Canard I am sure is beneficial but that can get a bit critical at higher airspeeds for flutter. I'm not sure how that was addressed and there does not appear to be any mass damping going on.

While Hugh used extruded polystyrene in the fuselage and cabin, I presume based on cost and ease of carving, this could be substituted with a better core material for better long term life expectancy. Delamination of extruded polystyrene is pretty common, since it is used in the RV industry in the US and typically doesn't last much more than 10 years if you are lucky and that is on fairly low loaded parts like seats and table tops.

I will take the numbers from the PDF and plug it into airplane PDQ to see what is predicted...
Just found this post, I don't know what PDQ is but I would be pleased and interested in any results if it was a design theoretical predictor.

Hughie
 

Himat

Well-Known Member
Joined
May 5, 2011
Messages
2,868
Location
Norway
Alright then gentlemens, I give you new canard design! :)

I use a coffe break to make this sketch. I dont want to design something real like that as I am not fan of the canards, but I want to sketch something new..I think I managed.
Dont bother wit cooling air intake location... was just my instant vision....could be different.
Dont bother also with obvious tail heavy apearance. Wing can be moved to match with proper CG.. or wing tips can be sweept backwards a bit...

But it is really new? Did you see anything similar with "split" canards alerady?

...

I see some benefits from that layout:
- better view forward
- when aproaching to the stall of canards, downwash will hit outer wing panels and lowering their AoA, so ailerons will work good and wingtips will not stall instantly due aileron acutating.
- main landing gear could be installed inside canard booms in the main wing.
- Canards could be mounted with negative dihedral, in line of pilot sight, so minimal area will obstruct pilots view..actually no canard area will be visible from the cockpit...


What do you think?
Go! Dont be affraid to express your opinions!

Aerodynamic thoughts, structural thougts..

I wonder what surprises I am waiting... :)

Mitja
Nice sketch Mitja!

If it is really new? Not sure, then I have to do some searching to prove otherwise. Of some unknown reason I started to think about "Star Wars...". Second thought, is it Jay’s twin boom airplane that have been reversed?

Looking at the sketch I think that there is those that have designed airplanes that do a sketch and there are those that have not. To me this sketch is from one that has designed airplanes. There are no obvious “will not work” features. You point at weight and balance, which can be solved. I do see two other issues that must be studied. The “one side” canard will load the boom in torsion. That may or may not be an issue. Second, with a “split” canard the aspect ratio get lower that something that maybe bring an aerodynamic efficiency penalty and “interesting” behavior at the extreme of the operation envelope.
 
Top