New canard designs?

[syclone]

My studies indicate that you load the canard to twice the load on the wing. The canard is an airfoil that can operate at Cls up to 2.4 with a flap (elevator). The wing is sized/loaded at half the load of the canard so it never stalls. I hope this helps.

 

[rtfm]

Fore wing loading is a function of CG, irrespective of the airfoil used. The airfoil of choice for the fore wing seems to be the R1145MS so that's also not a mystery. But this still begs the question: fore wing area and/or chord?

 

[Sockmonkey]

Fore wing loading is a function of CG, irrespective of the airfoil used. The airfoil of choice for the fore wing seems to be the R1145MS so that's also not a mystery. But this still begs the question: fore wing area and/or chord?

That area needed depends on where the CG is.
A flea is just a canard type where the canard just happens to carry most of the load. So are lifting tail types like the Gatard statoplan.
They are all species of tandem, and the rule for all of them is that the fore wing have a higher area loading than the aft wing.

 

[rtfm]

Simples...

 

[sming]

I know you like to design but perhaps there is something out there that fit the bill? Why not a vari-ez?
Two french designs come to mind :
The ibis What's an IBIS anyway?
And the composite onyx ?

Is "looking wicked cool" like revealaero a hard requirement?

 

[rtfm]

Hi,
I have researched the Ibis - great little plane. As is the Onyx. The problem I have with the Onyx is that the fore wing is dumping a significant amount of downwash directly onto the main wing - significantly reducing it's ability to produce lift. I'm struggling to understand why the designer would have made this decision. While this is the preferred configuration for Flying Fleas, it isn't exactly perfect for them either, for the same reason.

The Ibis is another great little plane. Rather high stall speed, in spite of it's use of flaps.

In both cases, however, I think a better job can be done:
The Onxy: swap the configuration of the wings, as mentioned.
The Ibis: Too square (could be better aesthetically), landing speed too high, despite the flaps.

Both of them (and all other canards): To build one, I'd have to invest in plans, and then follow them.

My little canard (which has the working name of DMC-01) will (hopefully) improve on these by:

1. No additional cost for plans, and no need to follow its construction methods. The DMC-01 will be built using Western Red Cedar strip planking over formers - exactly the way they build strip planking canoes. At only 2.1kg/m^2 fuselage area, I'm expecting a completed fuselage weight of 15kg (and that's with a solid 6mm skin). Why? Well, for one thing, it's light, it's strong, and best of all, it can be used to produce complex curves - just like composite fuselages.
2. Incorporating a superior wing layout (as mentioned above)
3. (Hopefully) have a stall speed of 35kts, and a cruise speed of 100kts+
4. Folding wings (exactly like a Flying Flea)
5. (Still considering this one...) Incorporate flaps. The problem with flaps is that they cause a strong nose-down moment, which in the landing configuration is the opposite of what one wants. So to balance this, my fore wing will have both the usual elevators, but also be able to pivot as though it were an all-flying wing. However, this pivoting action will only be linked to the flap lever. Drop the flaps, and the fore wing increases pitch to match the nose-down tendency. Obviously, some experimentation will be required in order to get this right.

Good looks a deal-breaker? Absolutely!

This is my first rough sketch of the DMC-01. I'm hoping to significantly refine this in X-Plane, so that I can show you some different angles. I'll also be using X-Plane to model its flying characteristics.


Duncan

 

[cluttonfred]

Duncan, I think one aspect you are not considering in terms of relative wing/canard position is performance at high angle of attack. Using the old 30/60 degree wake estimation for a horizontal tail blanking the rudder, a low canard *could* potentially disturb the flow over the high rear wing right when you need maximum lift from the rear wing at takeoff or landing. The other aspect is visibility...a low canard can block vision down and forward exactly when you need that view on landing, where a high canard like the Onyx is well out of the way except for the narrow struts.

On the pros and cons, I know that Mignet and Delanne and others were trying to get a "slot effect" in other words a beneficial interaction between the two wings caused by the downwash from the upper wing being drawn down into the low pressure area above the lower wing. Whether that is really beneficial for efficiency I cannot say (my gut says it probably hurts a little) but it does seem to contribute to a wide speed range and docile low-speed handling.

Personally my own approach to canard/tandem design is to use the same airfoil and same chord on both wings and follow the 3/2 or 150% rule for front wing loading vs. rear wing loading. That does mean that the rear wing never reaches its full lifting potential so in terms of efficiency a larger forward wing > a 50/50 area > a larger rear wing (canard). I accept that as the price to pay for the potential speed range/CG range/low-speed landing/accessibility/visibility advantages and of course the cool factor of tandems and canards.

 

[rtfm]

As usual, you've picked up something well worth thinking about. Thank you.

 

[rtfm]

Duncan, I think one aspect you are not considering in terms of relative wing/canard position is performance at high angle of attack. Using the old 30/60 degree wake estimation for a horizontal tail blanking the rudder, a low canard *could* potentially disturb the flow over the high rear wing right when you need maximum lift from the rear wing at takeoff or landing.

Just checked - no blanketing of the rudders, but the visibility thing is worth some more consideration. Depends on the precise placement I guess. And on the canard span. I'll be interested to see what the X-Plane cockpit view is like once the model is complete, and flying nicely. In fact, that's one of X-Plane's big strengths. It allows one to tweak this and that till the plane is behaving itself nicely. Kind of like visual programming in real time of the variables instead of simply inputting numbers into a design spreadsheet.

 

[cluttonfred]

To clarify, I didn't mean that there would be rudder blanking, but rather than the canard could blank the main wing at high AOA.

 

[rtfm]

Mmmm, I see what you mean. However, with the canard wing already set to 4 deg incidence, and the airfoil stalling at 13 deg, that doesn't leave a whole lot of AoA left. I'm not sure this is a real world scenario.

 

[Rik-]

Are most "canard" aircraft designed with a swept wing main wing?

What would the characteristics be if a plane had a hershey wing off a Piper for example?

 

[cluttonfred]

I believe that the main reasons for sweeping back the main wing on a canard aircraft are to get the wing out of the way to place a pusher engine closer to the aircraft CG and/or put the vertical stabilizer/rudder surfaces further aft of the CG so they are more effective.



Canard and tandem designs in which the rudder(s) are on boom(s) or a conventional rear fuselage don't need to sweep the wing, ditto for designs that use very light engines or one or more engines placed in other positions on the aircraft.

Are most "canard" aircraft designed with a swept wing main wing?

What would the characteristics be if a plane had a hershey wing off a Piper for example?

 

[cluttonfred]

Duncan, a couple more quick thoughts...some of your other designs have featured a large door rather than a canopy. With this configuration you have an opportunity to make a cockpit as easy to access as any car with no wing, strut, or gear in the way. Also, that tiny canard give me the heebie-jeebies as it would have very little authority and very limited CG range to keep the front:rear wing loading ratio to about 3:2. Here is the Piel Onyx for comparison:

View attachment 113818

 

[cluttonfred]

And just for fun, here is the Latécoère 225, a prototype canard amphibian ultralight that looks like someone found a kit for a conventional pod and boom design without the instructions and put it together backwards. ;-)

 

[rotax618]

Scale this one down.

 

[cluttonfred]

I am pretty sure that a canard that small only counts as a trim tab and that plane is essentially a delta flying wing.

 

[cluttonfred]

Hmmm...what are "splates"?

 

[Blackhawk]

You could scale down something like the "Lockspeiser LDA-01 Experimental Utility Transport"

 

[rtfm]

Morning gentlemen,
You seem to have been busy since I went to bed.

I believe that the main reasons for sweeping back the main wing on a canard aircraft are to get the wing out of the way to place a pusher engine closer to the aircraft CG and/or put the vertical stabilizer/rudder surfaces further aft of the CG so they are more effective.

Hi Cluttonfred,
I have read the justification in bold above, and it has never made much sense to me. The main spar in both a rectangular wing plan and a swept wing pass through the fuselage in the same place. Once external to the fuselage, it doesn't really matter as far as the engine is concerned.
The second justification makes more sense.