Rethinking the Wing

[Jac Mac]

Hi Folks,

 

Is there anyone on here that has looked into an airfoil that would allow slower speeds on these aircraft, even at the cost of top end either in actual scale models or real aircraft.

 

I,ve read 'Riblett' and feel it can be done as long as the canard is balanced to the main wing. The main reason to do so comes from the need to operate from grass strips & shorter runways. Obviously the landing gear ( wheel dia ) would need a rethink ( perhaps along the lines of the Mono-wheel ).

 

I would like to place the canard low @ the front and the main wing high at the rear similar to a dragonfly in side profile, but with the L- E, Velocity etc configuration in plan form with pusher prop etc. With the prop c/l up high the Mono wheel configuration would not necessarily have to be retacted.

 

Not looking for 200 mph here, 160/170 mph would be plenty on say 125/140 hp. Stall or min S/L to comply with our LSA would be slow enough.

 

Any thoughts?

 

Jac Mac

[Marc Zeitlin]

Is there anyone on here that has looked into an airfoil that would allow slower speeds on these aircraft.....I,ve read 'Riblett' ....

Did Riblett address the issue of maximum CL (Lift Coefficient) for given airfoils (sans flaps) and it's effect upon airspeed capabilities?

 

....The main reason to do so comes from the need to operate from grass strips & shorter runways.

This exact topic has been addressed within the last couple of days on the other canard web-forum. Get a Glastar or Zenith.

 

Obviously the landing gear ( wheel dia ) would need a rethink ( perhaps along the lines of the Mono-wheel ).

I don't know why that's obvious, except for the nose gear.

 

I would like to place the canard low @ the front and the main wing high at the rear similar to a dragonfly in side profile, but with the L- E, Velocity etc configuration in plan form with pusher prop etc. With the prop c/l up high the Mono wheel configuration would not necessarily have to be retacted.

Since you're redesigning the whole aircraft here, both aerodynamically and structurally, just make the wing large enough to get you the speed you want.

 

Not looking for 200 mph here, 160/170 mph would be plenty on say 125/140 hp. Stall or min S/L to comply with our LSA would be slow enough.

LSA are restricted to 1320 lb. Max. Gross and 120 kts max speed.

 

Any thoughts?

Just these few.

[Jac Mac]

Did Riblett address the issue of maximum CL (Lift Coefficient) for given airfoils (sans flaps) and it's effect upon airspeed capabilities? ( Riblett seemed to question some of the airfoils used in some canard applications in respect of this, yet did not come to a definite conclusion on the subject. )

 

This exact topic has been addressed within the last couple of days on the other canard web-forum. Get a Glastar or Zenith. ( I dont want either of these )

 

I don't know why that's obvious, except for the nose gear. ( A means of accomodating a larger tyre footprint without a huge drag penalty, you would have to land on some of our grass strips in the winter to comprehend. )

 

Since you're redesigning the whole aircraft here, both aerodynamically and structurally, just make the wing large enough to get you the speed you want.( This is what I was suggesting /asking )

 

LSA are restricted to 1320 lb. Max. Gross and 120 kts max speed. ( In the USA , yes but these standards have not been adopted worldwide yet, We still have our own microlight category which has no fixed upper limit ' yet' speed wise.)

 

Just these few.

 

Cheers

Jac Mac

[Marc Zeitlin]

Riblett seemed to question some of the airfoils used in some canard applications in respect of this, yet did not come to a definite conclusion on the subject.

My point was that without lift augmentation devices such as flaps, it doesn't make much difference what airfoil you use - you'll max out the CL around 1.6.

 

I dont want either of these

Perfectly understandable - neither do I :-).

 

A means of accomodating a larger tyre footprint without a huge drag penalty

You can put 6.00x6 wheels/tires on these aircraft without any difficulty - it's been done, but the problem is the nose gear, so without a major redesign of the nose gear system, soft grass is NOT a viable option.

 

Since you're redesigning the whole aircraft here, both aerodynamically and structurally, just make the wing large enough to get you the speed you want.( This is what I was suggesting /asking )

No, you asked about airfoils, not wing size. But if you're willing to redesign the whole plane, then you can certainly size the wings for whatever speed you'd like to fly.

 

In the USA , yes but these standards have not been adopted worldwide yet, We still have our own microlight category which has no fixed upper limit ' yet' speed wise.

Where is "we"? Your profile does not list a location, so I wrongly assumed you were in the USA.

[Jac Mac]

Sorry Marc, When I joined last week our Broadband ' dropped' me ,as I was about to do the profile thing. I'm from New Zealand, way down south.

 

Im not locked in to either basic canard configuration ( If you consider the Q2/ Dragonfly one type & the LE , E-Racer etc the other type ).

 

Take the Q2/ -D/fly setup for a start, Fit a large monowheel ala Europa & retain some small/light wheels in the canard tips for taxi purposes. Use thicker airfoils,& or longer spans to achieve the speed goals as reqd. In this configuration the goals may be more achievable due to the similar size of canard & main wing whereas the L.E. has a large size difference between canard/main wing and harder to balance for flight @ both ends of the speed range. With these we would have to arrange weight in order to keep fuel /passenger at the cof g.

 

Jac Mac

[rpellicciotti]

It is certainly possible to design a canard aircraft that can land slow and have STOL characteristics. The Rutan Grizzly and the Colin Chapman/Lotus Microlight come to mind.

 

It would basically have to be a new aircraft design. Modifying a Long-EZ is probably not the best route to take. The construction methods (moldless composite) could be used.

 

I am not familiar with the Sport Pilot rules in OZ but the US rules say, maximum 2 place, max gross 1320 pounds (not much different than the original Long-EZ gross weight). fixed gear and a stall speed of 51mph (45 knots). For practical purposes, the empty weight needs to be around 750 pounds in order to accomodate 2 people, some baggage and fuel. Again, this is not too far from the original Long-Ez design empty weight.

 

I would enjoy discussing this further as I have a lot of experience with both Long-EZ's and LSA aircraft. Either on the forum or offline.

 

Regards,

[Jon Matcho]

I would enjoy discussing this further as I have a lot of experience with both Long-EZ's and LSA aircraft.

I would enjoy following the topic!

 

Either on the forum or offline.

Hopefully online as much as possible, otherwise it's hard to follow.

 

Here's Perry Mick's page dedicated to the topic: http://www.bridgingworlds.com/LSA.htm

[rpellicciotti]

Online is fine with me, Jon. I just wasn't sure if it was an appropriate topic for your forum. I will dig out some of my references and we can get started!

 

Rick

[satch]

+1 vote for online discussion / participation where possible.

[Jon Matcho]

I just wasn't sure if it was an appropriate topic for your forum.

It is absolutely a good topic -- imagine an LSA plans or kit canard? I'd be interested, mainly in a plans option. I don't know how commercially viable that would be -- the designer would have to be fueled on passion (or something else). This would be a great "Open" project to start. Let me know if you want an Open-LSA sub-forum setup.

 

I don't consider this "my" forum; it's definitely not my forum -- it's yours, his, and hers. I am here just to coax it along and try to keep things organized.

[Jac Mac]

Jon & Rick,

Good to see that I have sparked some interest, I think that there are probably many more who have asked themselves the same Questions.

 

I agree that we are looking at a fresh design here probably incorporating the best of many feature's including a few from the 'backward canards'.

 

To get you on the same train of thought that I'm on think along these lines, I will use the Europa as an example not because I like them but it does contain a few of the feature,s I have mentioned.

 

Chop the Fuselage off @ the trailing edge of the wing, and again @ the firewall. Now graft the Firewall Fwd components on to the rear of the main wing complete with pusher prop. This would have the prop c/l at the same height as the top of the canopy. Now graft the old Tailcone ( Minus vertical fin and with the Horizontal Stabiliser reversed to become your canard ) on to the old Firewall. Add your vertical fin/s to your wingtips or on two tailbooms with inverted 'V'. Put some sweepback if desired ( not too much, we should all know why). The ' Main' Monowheel will now have to be moved slightly rearward in the centre 'Tunnel' and the nose wheel [steerable] mounted so that in a taxi configuration the a/c has a definite nose down attitude.

 

With this setup I know we are getting close to a Flying wing rather than canard, however the undercarriage system described would allow the landing / takeoff distances to be shortened considerably. On touchdown the a/c could immediately be 'pushed over' on to the nosewheel ,killing the lift on the main wing and allow hard braking if required. At takeoff the flying attitude should be able to be assumed earlier also. Flap,s may be able to be incorporated that only work during the takeoff phase .

 

The Canard would need some arrangement where the range of movement (limits) could be controlled by a load sensor or linkage on the U/C.

 

Hows that for a starter.

 

I had better go earn some $$ now , catch you later.

 

Jac Mac

[Jon Matcho]

Hows that for a starter.

Not to take the wind out of your sails (or foils), but without a drawing you don't have more than a recipe for a clay sculpture. So make it, take a picture, and post here.

 

The most work done towards this goal has been by Perry Mick at the link I noted in an earlier post. He's gone so far as to design an X-Plane model. Next step would be a real-life model. Maybe he's working on it?

 

The IBIS supposedly had LSA qualities (or met the spec.), but the designer has chosen not to sell plans in the US.

 

If this thing has any legs I'll gladly open up a new sub-forum for the discussion.

[deronjthomas]

Did any one give thought to variable swept wing designed? Or even variable swept Cannared?

[rpellicciotti]

It is absolutely a good topic -- imagine an LSA plans or kit canard? I'd be interested, mainly in a plans option. I don't know how commercially viable that would be -- the designer would have to be fueled on passion (or something else). This would be a great "Open" project to start. Let me know if you want an Open-LSA sub-forum setup.

 

Jon, I have already written to you about the OPEN-EZ project and what a great idea I think it is. I have been getting some files together to send you that will go along with what you have already posted. Things like CP newsletters, a collection of drawings from people that have made mods to the airplane, etc. At some point, I will burn a CD and send it to you.

 

Based on my activitiy in the LSA world, I can tell you that there has been a lot of push back from people on the price of the new S-LSA airplanes. At the same time though, there doesn't seem to be much interest in kit LSA planes or homebuilts that are LSA compliant. It could be that the "right" airplane just hasn't come a LONG yet. A lightly built, long-ez looking, airplane with generous wing area, fixed gear, a modern engine (rotax 912 or Jabiru 3300), and modest runway requirements would be COOL.

[Jon Matcho]

Jon, I have already written to you about the OPEN-EZ project and what a great idea I think it is.

Yes, thanks!

 

I have been getting some files together to send you that will go along with what you have already posted. Things like CP newsletters, a collection of drawings from people that have made mods to the airplane, etc. At some point, I will burn a CD and send it to you.

That would be great. I'll review and look to factor into the next release.

 

Based on my activitiy in the LSA world, I can tell you that there has been a lot of push back from people on the price of the new S-LSA airplanes. At the same time though, there doesn't seem to be much interest in kit LSA planes or homebuilts that are LSA compliant.

Sounds like "reality" speaking up.

 

It could be that the "right" airplane just hasn't come a LONG yet. A lightly built, long-ez looking, airplane with generous wing area, fixed gear, a modern engine (rotax 912 or Jabiru 3300), and modest runway requirements would be COOL.

I think Perry is on to a very nice design. I like the straight main wing, with rudders in the duct-thing. Straight wings are slightly easier to build -- you can use the same templates for multiple sections of the wing. A minor improvement, but those minor improvements do add up. Perry is basing his work on the Solitaire, which is a proven design. How about a design/mission profile for this thing?

 

Did any one give thought to variable swept wing designed?

Not during waking hours.

 

Or even variable swept Cannared?

Actually, Burt Rutan did and implemented it on the Beech Starship. However, a system like that would be far too complex to be worthwhile for a first generation LSA. This design would need to be entirely simple -- less is more.

[chasingmars]

Might be tough getting landing speed down to 45 kts necessary for LSA compliance with no flaps (pretty much a given on a canard)... at 1320 lbs gross, that would need (2 W = V^2 x A x rho x Clmax) ... about 120 sq feet of wing area... More than the much heavier cozy... then again, you're only going to be going 120 kts, so maybe that's fine.

[rpellicciotti]

I've been running some numbers and have come up with about the same thing that you have. One thing that is a given is that canard aircraft are not STOL airplanes. It can be easily demonstrated that for a given wing area and weight, the stall speed or minimum speed for a canard configuration will be higher than a conventional configuration aircraft. This is due, of course, to the canard airplane's inability to get the maximum lift that is available from the main wing.

 

I think it is significant to note that most all of Burt's follow on designs were fairly conventional in configuration or they were 3-surface designs. I like the 3-surface designs as it retains the "stall fuse" feature of a canard airplane but is able to perform more like a conventional airplane. For a good comparison between the two configurations, look at the Starship and the Piaggio Avanti. Both aircraft are about the same size but the Avanti out performs the Starship in most every respect.

 

There is no doubt that our canard airplanes are efficient and get high speed from the available horsepower (I run with the 200hp RV's around here with no problems in my IO-320 powered Long), but the RV can certainly land slower and take off in 1/3rd the distance of my airplane. I also have a very broad C.G. range compared to the RV. It is simply a case of a design that is optimized for one particular mode of flight (long distance cruise at high speed) versus STOL with moderate speed/efficiency.

[rpellicciotti]

If you can believe their figures, this canard airplane meets the LSA rules:

 

http://www.fabenet.com.br/english/bumerangue.htm

 

It would have to have fixed gear and a "climb" pitch prop.

[karoliina]

My point was that without lift augmentation devices such as flaps, it doesn't make much difference what airfoil you use - you'll max out the CL around 1.6.

 

This is an old thread, but I just found it accidentally. Interesting topic indeed. You say getting more than 1.6 CL is not feasible. How about this (see attachment) - it is the airfoil used in all Diamond models (from motor gliders to DA-42 Twin Star).

fx63137sm.txt

[Ron Springer]

You say getting more than 1.6 CL is not feasible.

That's not exactly what he said. It is definitely feasible to get a CL above 1.6 or even 2.0. There are a large number of airfoil sections that max out "around" 1.6, which is probably why he selected that number as a typical value.

[deronjthomas]

What about wing design similar to a British Spitfire, or a P-51 Mustang. The slight angle should help with performance, and help with the stall speeds.

[Spodman]

What about wing design similar to a British Spitfire, or a P-51 Mustang. The slight angle should help with performance, and help with the stall speeds.

Eh? I'd say the mission of a fighter is a bit different to a Cozy. Is the slight angle you speak of the dihedral? No effect (except slight increase) on stall speed.

[Richard Schubert]

This is an old thread, but I just found it accidentally. Interesting topic indeed. You say getting more than 1.6 CL is not feasible. How about this (see attachment) - it is the airfoil used in all Diamond models (from motor gliders to DA-42 Twin Star).

If you examine the trailing edge of this airfoil, you will see the rear 30% is deflected downward almost like a built in flap. This will raise the CL at the expense of a high pitching moment. IIRC the modification to the eippler airfoil for the ez consisted of flattening the bottom to remove the curvature and, I have heard it said, to reduce the pitching moment.(speculation?). For canard aircraft, a low pitching moment main airfoil will reduce the amount of lift the canard must produce.