rtfm
Well-Known Member
Thanks for that. I see what you mean. However, two pylons at the rear for the rear wing wouldn't be the end of the world. It would be interesting to model all three.
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Kiwi303
Well-Known Member
If you're thinking of low rear wing, Look at the Diehl XTC
rtfm
Well-Known Member
I thought I'd sought out every canard plane on the web, so this was a pleasant surprise. Thank you. A very interesting design. Is that canard wing able to pivot? Looks like it. But then again, he's fitted it with fowler flaps, so maybe not.
Also interesting (to me) are:
Also interesting (to me) are:
- Rudders inboard (7'2" apart, allowing the outer panels to be removed.
- No rear wing sweep (All Rutan-inspired rear wings have quite large sweep)
- Rear wing dihedral
The Waspair Tomcat layout adapted to a sleek fuselage pod could be an interesting approach.
Kiwi303
Well-Known Member
I don't know much about them, just saw the thread posted a couple months back and it stuck in my head. It really looks cool, but truthfully for the role I'd probably plumb for a Micro Aviation B22 Bantam with floats.
but an interesting plane nontheless.
There are two owners on this thread Diehl XTC who could likely tell you more about the canard. to me it looks from the photos that it is solidly bolted on the for brace with two bolts each brace, one above the other. If so any pivot must be internal to the canard, not at the connection between canard and posts.
DaveK
Well-Known Member
What about the Falcon? High wing with low canard. 
The primary reason that most of Rutan's canards have so much rear wing sweep is to mount the engine near the center of gravity. The alternative is a huge cut out in the wing root trailing edge (ala. Vari-Viggen)
A secondary reason is to mount vertical tails farther aft.
rtfm
Well-Known Member
For the canard-gurus:
Rear swept wings look stunning. However, the greater the rear sweep, the less need for dihedral to the point where the rear wing can actually have negative dihedral. Mostly, though, the rear wing has zero dihedral, which to my eyes looks naff.
On the subject of a canard plane's rear wing:
I understand that the forward pitching moment produced by the deployment of flaps can easily overpower the lifting ability of the fore wing, but if one had an all-flying fore wing mechanically linked to the flaps, this might resolve this issue?
[EDIT] I think I've answered my own question in the preceding paragraph. On the other hand, one could mechanically link flaps to the canard elevator?
On the subject of take-off/landing speeds:
I'm still unclear about why canard planes have such high take-off/landing speeds. Some have suggested this is because the fore wing floats in ground effect. This might explain faster landing speeds, but not faster take-off speeds. Others have suggested that canard planes have no way of slowing down because they have no flaps.
Question: if one had two quite closely spaced rudders (like on the Revelaero), could one not have split rudders with each rudder splitting into two leaves to act as a speed brake?
Regards,
Duncan
Rear swept wings look stunning. However, the greater the rear sweep, the less need for dihedral to the point where the rear wing can actually have negative dihedral. Mostly, though, the rear wing has zero dihedral, which to my eyes looks naff.
On the subject of a canard plane's rear wing:
- A non-swept wing is a LOT easier to build and to mount to the airframe, and it allows a bit of dihedral which looks "proper".
- Aesthetically speaking, I also don't much care for the exaggerated wing-tip winglets/rudders + it makes it very difficult to fold the wings, because those winglets get in the way
- Placing the rear wing high seems to me to be the optimal configuration, since it keeps the downwash of the fore wing well away from the rear wing, even though one has to contend with the interference drag of the two wing masts required to raise the wing above the rear fuselage. I'm not sure, but the lessened canard downwash may compensate for the added drag of the wing masts. Dunno, but it seems possible.
- I'm not convinced that strakes are a great idea. Yes, it provides space for fuel tanks, but (1) they are destabilising, and (2) they are difficult to build. The Apollo, for example, dispenses with them altogether for these reasons.
- Most canard-equipped planes employ elevators on the fore wing. But what are the benefits (other than ease of building) of a all-flying canard (like Hugh Lorimer's Iolaire)? If any...
[EDIT] Ihave just come across this summary from Orion (2003)
I understand that the forward pitching moment produced by the deployment of flaps can easily overpower the lifting ability of the fore wing, but if one had an all-flying fore wing mechanically linked to the flaps, this might resolve this issue?
[EDIT] I think I've answered my own question in the preceding paragraph. On the other hand, one could mechanically link flaps to the canard elevator?
On the subject of take-off/landing speeds:
I'm still unclear about why canard planes have such high take-off/landing speeds. Some have suggested this is because the fore wing floats in ground effect. This might explain faster landing speeds, but not faster take-off speeds. Others have suggested that canard planes have no way of slowing down because they have no flaps.
Question: if one had two quite closely spaced rudders (like on the Revelaero), could one not have split rudders with each rudder splitting into two leaves to act as a speed brake?
Regards,
Duncan
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Kiwi303
Well-Known Member
Rather than the split rudders, make panels on the rear canopy, so your engine inspection panels maybe open up like a jet fighters fuselage airbrake.
On the subject of landing speeds: As the canard must stall first, it follows that the main wing must have some margin between actually achievable AoA and it's stall - that margin is lift you cannot access. In addition, the downwash from the canard will reduce the AoA of the inboard section of the wing, further reducing it's lift contribution.
Also, thje 'common canard' today is built for efficient (fast) cruise, not low-speeds.
rtfm
Well-Known Member
Quite a few variables...
The idea I've seen somewhere was to use the variable-sweep canard - it is swept at cruise and then 90 degrees to the fuselage at landing...
This is the Beech Starship.
rotax618
Well-Known Member
This is a successful canard.
rtfm
Well-Known Member
Perhaps - but that very large fore wing will be dumping all its downflow directly onto the main wing. No wonder it has to be so large...
rtfm
Well-Known Member
I'm designing a small, light, simple canard. This is way overkill for me.
This canard looks like it was inspired by Burt Rutan's first canard: Vari-Viggen. But it includes a couple of improvements. First, the engine is mounted higher, obviating the need for a cut-out in the trailing edge. Secondly, the crew sit farther forward for balance. Finally, the canard is larger. They probably wanted to mount the canard even farther forward, but were limited by pilot visibility.
Note that the latest generation of fighter jets (various Mirage III modifications, Rafale, SAAB VIggen and Griffin) are deltas with short-coupled canards. The canards generate vortexes that re-attach airflow to the main wing at high angles of attack. Since high-angles of attack produce huge amounts of drag, they are probably not relevant to amateur builders.
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canardlover
Well-Known Member
Duncan , the higher landing and takeoff speeds are a result of the Canard/Foreplane ( in most cases/designs) being loaded twice as heavily as the wing to insure it stalls before the wing thereby preventing deep stall.
The inboard rudders ( as in my Voodoo/Orion designs aka Revelaero ) could be split to serve as airbrakes but would entail a pretty complex control linkage design. I will be employing the inner 1 foot of the trailing edge of the outer wing panel , inboard of the aileron. as a split speed brake. This will provide a little over 300 sq inches of area deflected.
rotax618
Well-Known Member
Read about it.
rtfm
Well-Known Member
Hi. The main reason I'm embarking on this canard design exercise is because I saw the Revelaero designs, and it was love at first sight. So this is great.
I agree (after thinking through the implications) that the split rudder idea is not that great. However, I'm a little puzzled by your choice of using the TE inboard of the aileron for the speed brake. Should one of the brakes fail, you are going to have a major asymmetry issue.
My preference would be to have this between the rudder and the fuselage. Based on my initial preliminary drawings, I should be able to have 237 sq inches (per side) of braking area. Bearing in mind that this is to be a very small plane (fuselage is just over 11 ft long), powered by my trusty 50hp motor, this is probably sufficient.
Question:
How does one size the fore wing? I understand that there is a trade-off between max Cl, wing area and wing loading - but what is one aiming for relative to the main wing?
Regards,
Duncan
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