Dave:

For stability the forward wing should have a higher AoA.

Yes, but....

I have the feeling that propwash is a very significant factor. I expect the upwash of the main wing was only important to the canard when gliding. Also, it's possible to trim just a little up-elevator to provide the necessary raised AoA. The elevator panel was the same as the original Duck..

I got away with murder by adding or reducing the throttle. In fact, I would go so far as to say that a main wing stall before the canard is not the end of the world. With Charles' wingplan design flat spins and other fun and games are all possible. Just give it some more power to get back to normal.

Over the time I've had my Starship I've flown with quite a range of CoG positions, sometimes by mistake. The canard incidence is +1.5 deg. My favorite CoG was arrived at by trial and error (sorry!) and I now stick with it. I recently tried a stall in roughly level flight, just to demonstrate the safety of the canard arrangement. To my surprise, the wing stalled first, suggesting that I've arrived at a too rearward setting. It was easy enough just to open up the throttle. In particular, my landings are gentler like this. Perhaps I'm wrong, but I found that, with the canard stalling first, I used to dive into the ground. Whereas now I can slide in at stall speed.

Hi Charles,
I am building (i have already made the fuselage and main wing) a rear powered design and i have found the canard CoG calculator.
So what you are telling me is that i will need to use a 3.5 degrees of decalage (AoA difference between wings), right?

I must add that i plan on adding dihedral at the tips of the main wing.
Bad thought?

O boy I love this forum! Nick u r right I was speaking generally as most canards I think are pushers. Canard so close to prop brings many engineering issues which u guys have mastered to your benefit. That being said I want to design for the most reliable engine first - gravity, and then, if at all possible, consider prop wash effect. We may very well end up with a difficult to control aircraft just when our hands are full dealing with an engine out!

If I may, remember incidence is different to AoA!

For example on a swept wing you may have same incidence at root and tip but the AoA can be quite a bit different root to tip, because as you go outboard the local airflow becomes tilted up and the stagnation point migrates aft under the Leading Edge.

In other words you may have built an untwisted wing, but as far as mr Airflow is concerned your wing is twisted.

you may have same incidence at root and tip but the AoA can be quite a bit different

. Yes, I'm sure the reason I've had such a long and reliable life out of my Starship, in spite of being a destructive pilot, is the following:

In relation to a notional datum line along the fuze, tip incidence is zero, root is +1.5deg, canard is +3deg and thrust line is zero. Main wing airfoil is semi-symetrical, S-3021 and the canard is more or less flat bottomed, Selig 7055. (In the post above, I referred to canard incidence of 1.5, I meant relative to the root chord.)

The Delta Duck, IMHO owes a lot of its fun to having the motor at the front.



PS Many, many thanks for the good advice I got from this thread back in Sept 09.

nick im too lazy to go and look, what r ur incidences, thrust line, etc, on the delta and chudle duck?

Almost all modelers agree that the clean air feeding the front motor not only makes it more efficient, but also makes it much more quiet, always a good thing!

The additional benefit of the canard channeling that high velocity prop wash onto the wing can be really gr8, as long as the angles r set to give the desired power on/power off characteristics.

For safety some would want a slight down power/pitch couple, others like me want as little power/pitch couple as possible and others want a slight up power/pitch couple with a close coupled canard that helps keep stall speed very low.

I was looking at the vid on the jet powered Aerostar (real) and they say like Boeing, they want a slight up power/pitch couple. I thought most designers wanted it the other way though.

Keep up the good work!

Here is the original drawing that Charles gave me to copy.

I think all the variants had the wing and thrust line at zero incidence. The original Delta Duck had +1.5 deg or +2 deg for the canard. Mine was at zero because I didn't want to deflect the airflow right behind the prop.

At least, that's how I remember it.

I still have mine, though I borrowed the wing to build another variant, the Polar Duck, which owed a lot to the Polaris.

Cheers

Nick

This is just guessing, but in line with what I was saying about gravity, in other words designing around gliding, if I were to set up canard about + 3 degrees or whatever works best for a glide and then setting the thrust line to approximate the airflow in level flight how would that work?

I see the polar duck as just replacing the Polaris wing with the exact (maybe slightly lower canard, with 1 to 3 degrees incidence) delta duck wing/canard config. That way you end up with a 3 surface giving us the thrust vectoring of the Polaris with the slot effect of the canard.

Nice artwork!

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA063819

Info on different canard configurations.

On page 2 it says that the close coupled canard has a 65% increase in Cl than the pure delta F-106 delta dart.

to sumarise the article, the most lift was with the TE of the canard just ahead of the LE of the wing at a height of between .1 to .25 of chord, center to center above the wing.
For an easy ballpark, if the space between bottom of canard and top of wing is .1 of chord you are on the right track.

It also said that when an up canard deflection is coupled with a flap down position of the elevons the lift is the greatest.

The most important point to consider is that the negative downwash effect of a long coupled canard is not produced by a short coupled canard but instead turns it into a positive effect.

Happy flying.

teopbako

I am building (i have already made the fuselage and main wing) a rear powered design and i have found the canard CoG calculator.
So what you are telling me is that i will need to use a 3.5 degrees of decalage (AoA difference between wings), right?

Yes, because the canard needs to reach stall angle before the main wing.

teopbako

I must add that i plan on adding dihedral at the tips of the main wing.
Bad thought?

Where are your vertical stabilizers? Why add dihedral out there unless it's for lateral stability due to the wing's shape? Dihedral at the tips will slow down the aileron roll rate. If you need the dihedral, then use long ailerons with a bit of extra width.

Charles

Here's a couple of historic canard planes to consider..

Bleriot V 1909


Wright Military Flyer 1909


I've had an interesting time browsing around the internet in search of an early canard and those two look like practical modelling propositions to me, especially the Bleriot 5 with the fin which was added after the first crash and just before the second. It wasn't a big success by any standards. But it looks as if it ought to fly quite well. Here is a source of good info..

I am resolved to avoid my usual approach of getting out of trouble by overpowering my models. Bleriot had less than 20hp to play with.

Nick

Nick, Thanks for the interesting link. One of my phases of modeling interests was trying to make my planes go at small scale speed which, as I was told, was not possible. I experimented with large light weight models with barely enough power to fly. One of those had a 63 inch span with Speed 400 power. Another was so slow that no one could stay behind it. Later, my interest turned briefly to speed. At present I am happy with graceful flight and three point landings. One of my goals now is to enhance my appreciation of the hobby by being aware of everything associated with it and not just the interest in airplanes. I look forward to your visit.

Charles

Thanks Charles

In recent weeks I've had a lot of fun with a DH115 (fast) and a DH1 (slow). I'm enjoying scale-ish models. What I'm considering now is something I can build and fly in a couple of weeks when I visit Georgia at Christmas. It has to be a canard, in honor of the godfather of this thread, from which I have learnt so much. For speed, how about a Depron Long EZ?

Long EZ build (3 min 42 sec)

On the other hand, something unusual like the Bleriot V looks like an interesting idea. Plan it before I come. I sheet of Depron and an 800 MaH Lipo should do it.

Nick