Canard question

[talkthetorque]

Hi guys

I'm trying to get a specific design to work and need some advice. I have a very good understanding of aerodynamics but all my designs have generally been conventional planes. I'm trying to design a plane that doesnt takes up a lot of space but can carry heavy payloads. I'm going to use 2 GWS Slow Sticks as my planes. I'm alredy working on a low wing version (86") with increased elevator and rudder area but now I think I would also like to test a canard. The front canard will just be a another wing. So basically it will be a wing up front (43") and another wing at the back (also 43"). I will fit 2 rudders ontop of the back wing. Please can someone help me with C of G and any known advice for this type of craft? It will be something like the full size Quickie Q-200

Regards

[MarkusN]

The standard rules for aerodynamic center still apply. If both wings are exactly the same size, CG will be somewhere in front of the mean of the two quarter chord lines. (common wisdom has it that safe locations of CG are 8 to 16% of mean chord in front of A.C.)

[Brandano]

incidentally, that's generally called a tandem wing. Don't put the wings too close together and make sure you get your stagger and incidence angles right, or their interaction might cause nasty surprises.

[talkthetorque]

I was planning to have one up front and one at the rear of the fuze but now I'm wondering having them to far apart might lend itself to being affected by turbulance in the pitch moment. Similar to the thinking of smaller tail areas then longer tail moments and vise versa. If you look at the full scale quickie Q-200 the wings are fairly close together. Any input on that? :)

Regards

[ghoti]

Check out the Flying Flea
http://www.valkyrie.net/~flyingflea/

[MarkusN]

A close-coupled tandem like the flea can show all kinds of nasty behaviour due to the wings influencing each other. Full size fea pilots have suddenly found themselves flying inverted with no sensible possibility to leave that state. (The original concept of the flea has no ailerons; the whole design set out to "exterminate" that "difficult third control function".)

Having the wings too far apart makes for sluggish reactions, though. The Quickie is probably a good compromise.

[allanflowers]

A canard might not be the most efficient configurations for a heavy lift airplane. In order to insure reasonable stability, the front wing has to be significantly higher in loading per unit area. This means it is going to have more drag too.