Canard airplanes CG

[Targo]

Im currently designing a Canard airplane. I was guiding my project by an Andy Lenon Book.
Now he recomends a couple of calculation to determine the NP and the CG in a Canard airplane. When I follow those steps I got my self with more than 2 pounds to balance the plane ( on a 62" wingspan , 0.46 engine )because of the CG position i got.
I would appreciate a hand on it! Is it really well positioned? I Think that it would better be a couple of inches foward form the leading edge.
Here are the characteristics

main wing area: 720 sq. in
aft wing area : 190 sq. in
main wing chord: 12 in
aft wing cord : 8 in
Distance between 25% MAC : 21 in

Andy Lenon says:
NP (from 25% MAC of main wing) : (190 *21)/((720*0.8)+190)
CG : 25% MAC of main wing foward from NP

That puts the NP 2.25 in front of the leading edge, and 6.25 in to the CG!!!
The engine is placed just behind the aileron, and would be given a real hughe torque with a 19" arm on a 33 in airplane!!!

Please let me know what U think

[Dave Robelen]

Hello Targo,
First, I believe you swapped the front and the aft wing in your post. But assuming the small wing really is in the front (a canard) the numbers you mention make sense. Question? Did you figure in the weight of the battery and controls you can mount forward? How about the landing gear? From what you are dscribing, you might as well plan on building a sturdy canard, and the main wing as lightly as practical.
The issue you are up against is the reason that the full scale designer Burt Rutan used a swept wing on all of his Canard type machines. This is a tremendous help in moving the wing's center of lift aft. Of course you then have the wingtips in a decent location for the vertical tails where they have a substantial moment arm aft of the CG.
Regards, Dave Robelen

[Targo]

U are right about the wing confusion! I just wasn't paying attention to what I was writting.
I should try to move all the equipment and battery as foward as posible... But....i thin k it wont do it.
What about the CG location? Do U think it is apropiate? Have U noticed the torque the engine would do?
I feel like the CG is way foward...

Thanks for the help

[Dave Robelen]

Hello Targo,
It sounds like you are getting sorted out in the layout of parts. Generally the reason the CG is prety far forward on a canard is to make sure the canard surface has a higher loading than the wing. This is critical so that the canard will always stall ahead of the wing. If you end up with a bit of ballast to reach the required CG, and it flies noseheavy, it is no big deal to pull some weight out. If you get off taiheavy with a canard, there is usually no second chance.
Take care, Dave

[Targo]

Thanks for the quick response!!!
Ok ill try it like that and see how the weight grows... If it gets heavier than 7 pounds , I'll put a .60 on it...
Thanks again:D