Why Build a Canard?

[Air_is_a_liquid]

Hi Everyone;

 

Newbie here. Wondering why so many people are building Canards? I've managed to find short lists of the advantages and disadvantages of Canards in general, however, what made you choose a canard over a traditional design for your home-built?

 

Here's a list from Desktop Aero:

 

Advantages

 

Possibility for very good stalling characteristics without elevator stops.

 

Sometimes a desirable layout from the packaging standpoint: Main wing carry-through behind cabin, pusher engine installation simplified.

 

Synergistic use of winglets for directional stability.

 

In certain cases a simplified control linkage is possible.

 

When wing flaps are not desired (for simplicity as in ultralights, or competition rules as with standard class sailplanes for example) the CLmax of a canard may exceed that of an aft-tail airplane.

 

For unstable aircraft, canard designs may have a CLmax and/or drag advantage.

 

Control authority is larger for unstable canard aircraft at high CL than for unstable aft-tail designs.

 

Disadvantages

 

Fuel center of gravity lies farther behind aircraft c.g. than in conventional designs. This means that a large c.g. range is produced or that the fuel must be held elsewhere (e.g. strakes near the wing root.)

 

CLmax problems with flaps or margin on the entire wing: Flaps produce a larger pitching moment about the c.g. on a canard aircraft. This results in the need for both large canard aerodynamic incidence change and high maximum canard lift coefficient. Note that since the value of a S is usually larger for canard designs, Cm0 has a greater impact on L than it does on aft-swept designs.

 

Induced drag / CLmax incompatibility: Canard designs can achieve equal or better CLmax values than conventional designs, and similar values of span efficiency. However, the configurations with high CLmax values have terrible values of e and those with respectable e 's have low maximum lift coefficients.

 

Directional stability: The distance from the aircraft c.g. to the most aft part of the airplane is usually smaller on canard aircraft. This poses a problem for locating a vertical stabilizer and may result in very large vertical surfaces. (Note, however, that winglets may be used to advantage in this case.)

 

Wing twist distribution is strange and CL dependent: The wing additional load distribution is distorted by the canard wake.

 

Power effects on canard - deep stall: Accidents have been associated with tractor canard configurations for which the propeller slipstream has prevented canard stall before wing stall. The result is a possible deep-stall problem.

 

Finally, and perhaps most importantly, canard sizing is much more critical than aft tail sizing. By choosing a canard which is somewhat too big or too small the aircraft performance can be severely affected. It is easy to make a very bad canard design

[Spodman]

"Possibility for very good stalling characteristics" History shows the possibility has been realised for the proven Rutan-style designs.

 

"Main wing carry-through behind cabin, pusher engine installation simplified. Synergistic use of winglets for directional stability." Yup.

 

"In certain cases a simplified control linkage is possible." May be referring to the elevon arrangements for the Vari. Didn't work really. Controls are conventional.

 

"When wing flaps are not desired (for simplicity as in ultralights, or competition rules as with standard class sailplanes for example) the CLmax of a canard may exceed that of an aft-tail airplane.

 

For unstable aircraft, canard designs may have a CLmax and/or drag advantage.

 

Control authority is larger for unstable canard aircraft at high CL than for unstable aft-tail designs." Erm, advantage???

 

Disadvantages

 

"Fuel center of gravity lies farther behind aircraft c.g. than in conventional designs. This means that a large c.g. range is produced or that the fuel must be held elsewhere (e.g. strakes near the wing root.)" Yes... that's why the fuel is in the strake, with no great disadvantage to the arrangement.

 

"CLmax problems with flaps or margin on the entire wing: Flaps produce a larger pitching moment about the c.g. on a canard aircraft. This results in the need for both large canard aerodynamic incidence change and high maximum canard lift coefficient. Note that since the value of a S is usually larger for canard designs, Cm0 has a greater impact on L than it does on aft-swept designs." Erm? Wot flaps?

 

"Induced drag / CLmax incompatibility: Canard designs can achieve equal or better CLmax values than conventional designs, and similar values of span efficiency. However, the configurations with high CLmax values have terrible values of e and those with respectable e 's have low maximum lift coefficients." ???

 

"Directional stability: The distance from the aircraft c.g. to the most aft part of the airplane is usually smaller on canard aircraft. This poses a problem for locating a vertical stabilizer and may result in very large vertical surfaces. (Note, however, that winglets may be used to advantage in this case.)" Yep, like those winglets.

 

"Wing twist distribution is strange and CL dependent: The wing additional load distribution is distorted by the canard wake." Not anything I've heard of before, assume effect is negligible.

 

"Power effects on canard - deep stall: Accidents have been associated with tractor canard configurations for which the propeller slipstream has prevented canard stall before wing stall. The result is a possible deep-stall problem." I can see that could be a problem, theoretically. Never heard of the concept before. Just in case I'll be bolting my engine on the back.

 

"Finally, and perhaps most importantly, canard sizing is much more critical than aft tail sizing. By choosing a canard which is somewhat too big or too small the aircraft performance can be severely affected. It is easy to make a very bad canard design" So by building something with many flying examples, and making yours the same as those flying examples (rather than making the canard a meter longer, or out of cardboard) your safety is maximised. They might also be saying conventional aircraft have far more metal bolted far to the rear of the c of g than they need to, coz it would increase safety!

[Jon Matcho]

I think that's a fairly good list of points, but moreso in the context of creating a new canard aircraft design.

 

Many issues with existing Rutan designs and derivatives have been worked out, particularly the "most important" issue:

 

Finally, and perhaps most importantly, canard sizing is much more critical than aft tail sizing. By choosing a canard which is somewhat too big or too small the aircraft performance can be severely affected. It is easy to make a very bad canard design.

You just have to get close enough to keep a new design in the air, and then finish up with:

• Evaluate performance (at one or more CG positions)
• Adjust CG limit or adjust length of canard span, and repeat

The author is right -- this is one area you need to treat with respect. You definitely need to get this part right to realize all the benefits. The good thing is that many designs have proven themselves in this area.

 

Also, regarding flaps, the IBIS has them (as well as the Starship FWIW). The result in both cases is reduced stall speed.

[H.Zwakenberg]

Also, regarding flaps, the IBIS has them (as well as the Starship FWIW). The result in both cases is reduced stall speed.

IBIS sports flaperons, aka single control surfaces that combine aileron and flap functionality. Also, to reduce drag, on IBIS these are used with a -10° cruise configuration setting.

Combining rudder and stick inputs is done with a mechanism called a mixer, of which I include a picture below. This one is from the IBIS that is being built by Dutch friend Hans Holsink.

 

 

bye

Hans

[Wayne Hicks]

The three most important features are missing from the list!!!

(1) Canards are fast cross country cruisers that are relatively inexpensive to build and operate.

(2) Rutan made it possible.

(3) Canards are unique, futuristic looking planes with ramp appeal that never dims.

 

More of us talk about those three things more than anything else on the list. Personally, I chose the Cozy IV because it was the only 4-seat, 200 MPH plane I could build for $500.

[Air_is_a_liquid]

I am also looking at the Cozy IV, as I stand 6'5" tall and weigh 250lbs. Is there another make I should be looking at due to my size and weight? Will the Cozy be a problem for me?

 

I guess I'll have to try some out at Oshkosh this year.

[Wayne Hicks]

So what football team do you play for?

 

There's no dancing room in the Cozy. The width across the hips is 42 inches, with side consoles and a center console to squeeze between. For prospective builders 6 foot 2 and taller, the designer mentions raising the canopy height and moving the front seat bulkhead backwards. The designer set an arbitrary front seat weight limit of 400 pounds. Even though the plane has been demonstrated to safely fly within its CG range with more front seat weight than that, he just felt that anything over 400 pounds would degrade the performance features of the airplane.

 

Yep, they don't call it Cozy for nothing.

[Air_is_a_liquid]

If only I could build everything 1.13% larger with the same Reynolds number.... now i might as well be slinging a neuse or purchasing a Starship off of rutan...

 

Can anyone here imagine what it was like for me in a Cessna 150 in my solo-ing days?

[deuskid]

The three most important features are missing from the list!!!

(1) Canards are fast cross country cruisers that are relatively inexpensive to build and operate.

(2) Rutan made it possible.

(3) Canards are unique, futuristic looking planes with ramp appeal that never dims.

 

More of us talk about those three things more than anything else on the list. Personally, I chose the Cozy IV because it was the only 4-seat, 200 MPH plane I could build for $500.

You are building a Cozy IV for $500? Kwel! ...

 

How ya doin' that?

 

I love the canard design and many of its attributes but haven't yet settled on it or an RV type craft. The Cozy is a little cheaper to build. The RV can use unimproved fields. Both can use similar engines [alternative]. The RV is a little more conventional and not as 'nasty' to build. A canard looks kweler [but I truely believe form follows function]. It is truely still a jump ball for me. Many more RVs in the air. Each can match the other for speed.

 

John

[Chairboy]

Can anyone here imagine what it was like for me in a Cessna 150 in my solo-ing days?

I can commiserate. I flew a Cessna 152 at 6'2, 280#. Not only did I fly it solo like that, but I flew it with a checkout instructor (I learned in a Cherokee, thank goodness) AND I took my mom and sister for a flight. Each flight required special attention to weight and balance. Eg, no full tanks! Good thing my mom and sister are wafer thin.

 

I once flew my sister from Portland, OR to Eugene, OR like this. 120 miles, and the 152 is no Cozy for cruise speed.

 

The plane feels cramped at 6'2, can't imagine what it's like at 6'5.

"Cessna 152: The plane you wear."

[Wayne Hicks]

The RV-10 is a very nice airplane. All the RVs are nice. I started out in '98 wanting a Lancair or a Glasair. However, I didn't have enough $$$ saved up for a kit of any kind. I couldn't afford the down payment.

 

So I bought the Cozy plans for $500 and paid for stuff as I went along.

 

Fiberglass doesn't have to be messy. But you can't quit in the middle of a layup. At least with rivets, you can put the gun down when you need to stop.

 

Fiberglass is easy to repair. I couldn't imagine hammering in the 12,000th and final rivet only to drop the airgun and DENT the wingskin. Can't repair that. Get on the phone and order a new panel.

[ekisbey]

I am also looking at the Cozy IV, as I stand 6'5" tall and weigh 250lbs. Is there another make I should be looking at due to my size and weight? Will the Cozy be a problem for me?

 

I guess I'll have to try some out at Oshkosh this year.

You'll fit. Only just, but there are some options to improve the situation.

 

There are several committed Cozy builders approximately your size from 6'3" and up, and those of us who've sat in a completed Cozy report pretty much the same thing; it's a tight fit, but tolerable. Beats the heck out of a 152, lemme tell 'ya! I'm your size, a bit lighter, and had a good experience in a "stock" Cozy.

 

There are quite a few tried-and-true mods to the interior of the aircraft that can be made to improve dimensions. Adding them together yeilds a surprising amount of space. Changes which alter the exterior dimesions of the aircraft (especially width) have fewer examples and are generally frowned upon, with a few exceptions, such as longer strakes or increasing canopy height. Those two mods alone, however, can yeild significant results.

 

Do a seach for "cabin width" here on the forum, you'll find a lot of info on the subject.

 

These discussions have excellent info to get you started:

http://www.canardzone.com/forum/showthread.php?t=393

http://www.canardzone.com/forum/showthread.php?t=372

http://www.canardzone.com/forum/showthread.php?t=1429

http://www.canardzone.com/forum/showthread.php?t=1249

 

Also, on "that other forum"

http://canardaviationforum.dmt.net/showthread.php?t=1793

http://canardaviationforum.dmt.net/showthread.php?t=2150

[Jon Matcho]

If only I could build everything 1.13% larger with the same Reynolds number...

Believe it or not, I met someone who was scaling up the Cozy by 15% all around. Last I knew they were in the tub stage, and were very serious about this. I forget what they were doing with the wings and canard, but do remember their take on the amount of work being HUGE as well as them recommending NOT to consider going down that route.

 

On the planes that you try on for size, make sure you find out any that have moved the seatback aft any, or have a different/stock canopy. See if they can take the seat cushions out for you (which might be padded up for their skinny 5'7" frame).

 

You can judge for yourself, but don't expect cavernous accomodations (even for us sub-6' guys & gals).

 

I will say that this is one time in my life that I'm happy to be 5'9" tall!

[AP3_C]

Jon,

 

Was/is that the "King Cozy"?

 

Seen a couple of pics on a web site, that thing is big.

 

A short bugger like me would get lost in something like that.

 

Jamie

[Air_is_a_liquid]

I think that making it bigger does not mean scaling everything by x percent... at that point, it's like you have to design a whole other aircraft from scratch!

[ekisbey]

Scaling up the aircraft is indeed akin to desinging a whole different machine. It's also unneccessary.

 

In general, its not the overall size of the Cozy that's the issue; the useful payload is sufficient for persons of larger build and there's plenty of spare legroom. The big problems arise in hip space and shoulder room and the overall shape of the interior. In the Cozy, very tall persons find problems can arise with headroom and range of motion -- your head feels very close to the canopy and the distance from seat to stick is less than the distance from wrist to elbow.

 

These issues have largely been solved over the years by various builders who had similar problems. Many variations of these mods, such removing the center console for more hip room, moving the seatback for extra legroom and seat-to-stick distance, and raising the canopy for more headroom, can be stacked together to free up significant space inside the aircraft. Lengthened strakes such as those implemented by the Cozy Girrrls also help with this issue. Raising the leg cutouts in the IP help those of us with long legs get in and out more easily witout the contortions. Reducing the thickness of the cushions frees up headroom, room in the leg cutouts, and additional legroom.

 

What these mods all have in common is that they either make no changes to the exterior shape or they make changes known to have a negligible impact on the performace/safety of the aircraft. Scaling up the aircraft as a whole has been debated over and over and over again, here and elsewhere. Several people are actully doing it, and one or two are even said to be flying. Unfortunately, not one has (so far) posted hard numbers or evidence from acutal flight testing which demonstrate the safety of their modification. I'd be hesitant to pursue such an approach without further evidence that what I was doing was safe and didn't involve any hidden "gotcha's."

[Jon Matcho]

Was/is that the "King Cozy"?

No.

 

I think that making it bigger does not mean scaling everything by x percent...

That was indeed the premise by which this fellow went forth, but then discovered that certain things do NOT scale, such as the width of the foam, wood in the longerons, and the horsepower of the engine (stronger engine required). There's also the issue of keeping the airflow to the prop free flowing (he was talking about mounting the engine further aft). He also never resolved what to do with the canard, wings, and main gear. Simply put, it's not simple.

 

...at that point, it's like you have to design a whole other aircraft from scratch!

Absolutely true -- and you NEED to TEST it.

 

Completing an aircraft is much more important to me than feeling something rub on my shoulders.

[deronjthomas]

Some of you may remember the problem that my brother and I are having. We both have very wide shoulders. He is 6’1” and 200lbs, and I am 5’10” tipping well over 300lbs. Currently I’m doing Fat Flush so I can take off the weight. I know I’ll have to get down my old High school Football/Wrestling weight of 200-220lbs. But I have about 12 to 18 months before I’ll be able to start the build, and then a few years for the build.

 

1· Adding 6” to 12” to the width of a Cozy Mark IV.

2· Staggering the front seats of the Cozy Mark IV.

3· Modifying the Cozy Mark IV in to a 3 or 2 place plane.

 

Dose any one have AutoCAD DWG files. Once I get my plans I’ll need to redraw parts of the plain to fit my needs.

[Jon Matcho]

Some of you may remember the problem that my brother and I are having.

Yes, I remember the discussion from this thread.

 

But I have about 12 to 18 months before I’ll be able to start the build, and then a few years for the build.

 

1· Adding 6” to 12” to the width of a Cozy Mark IV.

2· Staggering the front seats of the Cozy Mark IV.

3· Modifying the Cozy Mark IV in to a 3 or 2 place plane.

 

Dose any one have AutoCAD DWG files. Once I get my plans I’ll need to redraw parts of the plain to fit my needs.

Your #1 item represents a staggering amount of work -- I recommend not even considering it. The Cozy offers more space than your typical Cessna and most commercial aircraft seats (not First Class).

 

Your #2 item is not as hard as #1, but still a handful of work -- but at least not to do with aerodynamics (aside from center of gravity issues). Look at Steve Wright's StaggerEZ for IDs, or better yet, go to Rough River, see his plane and talk to him about retrofitting the seating into a Cozy.

 

Item #3 is easy, assuming you don't mean to include staggered seating. The view from the rear would not be ideal, but much better than out of a commercial airliner.

 

Currently I’m doing Fat Flush so I can take off the weight. I know I’ll have to get down my old High school Football/Wrestling weight of 200-220lbs.

Great! That's the best/easiest thing you can do to make your aircraft lighter. This should be your top priority, which would make all the options you put forth unnecessary.

 

Good luck!

[ekisbey]

The build itself can cause weight loss -- your first exotherm is gotta be worth at least a pound from the stress.

[Air_is_a_liquid]

What do you mean by flat-flush? Is it like adding maple skids on the nose, in leiu of nose landing gear? How does this help with interior space?

[Nathan Gifford]

I think he said, "fat flush." It sounds like a structural change (one I'm working on too) but it ain't on the aircraft!

 

I think you can get enough space on the simple mods that several people have already done (moving the seat slightly). With the CozyGirrrl Stakes that will probably give you all the room you need.

 

The best solution is to go to the airshows that canards. You will likely get an opportunity to probably sit in one. Two of the better airshows are Oshkosh and Rough River (RR - October). I can attest that RR is well worth going to since there was a pile of builders camping on the airfield.

[deronjthomas]

Just like Grand Master said:

“You no make belt fit you. You make you fit belt!”

 

Every inch I take off my waist the better off I’ll be.

[Bruce Hughes]

You missed another reason to build a canard: It will float.

 

When I started, I lived on Maui and had a son on Kauai and an

occasional urge to get to Honolulu. The little aluminum jobs

don't float. I know of a few that are -18,000 msl. One guy

swam for 18 hours before someone ACCIDENTLY found him -

with sharks circuling around when the coast guard got there.