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C.G help

#1
I'm working on extending an Experimental Airlines Synapse fuselage to 30 inches with canards. I have no idea how to determine center of gravity on a plane like this. Any ideas?

Also, I have increased the wing sweep to 30° if that makes any difference.
 

earthsciteach

Moderator
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#2
You can give this a shot:
http://adamone.rchomepage.com/cg_canard.htm

One of the biggest advantages to canard aircraft is they can be made "stall proof." Burt Rutan took advantage of this to great extent with his designs. The canard is given a higher angle of attack than the main wing so that it stalls first. When the canard stalls. the nose drops, preventing the main wing from stalling. Of course, it isn't just as straight forward as angle of attack. It also is a function of the airfoil profile.
 

CrashRecovery

I'm a care bear...Really?
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#4
What Ed does is before the wing gets mounted he puts everything in its place on the fuse and then takes the flat wing and then balances the fuse on the top of the wing. You now have the basic cg for the plane
 
#5
What Ed does is before the wing gets mounted he puts everything in its place on the fuse and then takes the flat wing and then balances the fuse on the top of the wing. You now have the basic cg for the plane
I thought about that, but being ignorant of rear wing/canard type planes.. I wasn't sure i could get it right.



Just a few more cuts and the wiring. Wanna take bets on whether or not it crashes and burns?
 

Craftydan

Hostage Taker of Quads
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#6
Aiidan,

Nice looking bird! Always liked the lines of a good canard.

No bets on the crash . . . who'd want to see a beauty like that get dinged!


CR,

That is a dead simple way to guess CG for a standard straight wing, but it stops working for swept, and canards just don't behave the same way -- I've even seen Canard CG's recommended in front of the LE!

Anything straight and simple, keep using EA's method (just too easy to ignore!). Anything complicated, run it through a calculator.
 

Craftydan

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#8
Brother, if you've got the running and the wooshing, and the gunning, you're 3/4 of the way there!

Good luck setting her free from this nasty ol' ball of mud!
 
#9
It flew. I'll need to make a few changes. Even with a spar, the flat canard fluttered at high speed. Also, the new canard will not have a control surface. I don't think it's needed.

 

Craftydan

Hostage Taker of Quads
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Mentor
#13
First of Beauty of a flight! trim 'till you're happy with it, but she's a keeper!

Also, the new canard will not have a control surface. I don't think it's needed.
But isn't that your elevator? I can see a plane with THR/EL/RUD or THR/EL/AIL, but you might as well be a 1 channel (or free flight) if you ditch that.
 
#14
I'm using elevons.

First flight- Canard fluttered badly enough to tear elevator hinges.

Second flight- Extreme dutch roll below 3/4 throttle. Installed *thingamajigs on wing tips.

Third flight-Mild Dutch roll below 1/2 throttle. Extended winglets to 4 inched below wing tips.

Fourth flight- Aborted. Deans to XT60 adapter broken.

Fifth flight - Smooth, stable, glides forever, but kinda hard to land. It seems to create a ground affect lift whachamacallit near the ground.

Why aren't airliners built this way? Captain Sum Tin Wong could have possibly made it to the runway in a plane like this.

*See photo