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HELP Larry and guys

Old 10-05-2009, 12:16 AM
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hillbillynamedpossum
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Default HELP Larry and guys

Hey guys,

Larry this is all your fault...I want to build a canard plane. But I want to do it "on paper a few times before I cut any foam. Im thinking 1/2" sturdy-r flat wings. (I did some experiments here : http://www.wattflyer.com/forums/showthread.php?t=50356 )The canard's control surface is going to run on the elevator channel, and the main wing's control surface will be on the aileron channel and I will use a rudder. I attached a jpeg generated off of autocad, and this is my first time doing that so I'm sorry if that doesnt work out.

I plugged my dim's into this http://adamone.rchomepage.com/cg_calc.htm
page and came up with 231 sq in of wing and control surface. and the c/g located between 10.25" and 11" from the leading edge. I calculated the weight of my wings and control surfaces to be around 4 oz. With 16 oz all up the calculator says 15.6 MPH stall at 24 oz all up the stall would be 19.1 MPH.


I just used the W.A.G. system to size the control surfaces. You all look everything over and tell me if you think the surfaces need to be larger on the canard or anything else.

Thanks
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Old 10-05-2009, 12:39 AM
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Larry3215
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Id say your over all design looks fine to me.

EDIT: Actually I might be tempted to mae the distance between the canard and main wing a little longer. That will make it more stable/tamer in pitch. Depends on how you want to fly it.



However, you need to use a special CG calculator for canards as they work differently.

http://adamone.rchomepage.com/cg_canard.htm

Enter all your dimentions and that one will give you a safer CG

Id start with a static margin of 10.

Id make the fin/rudder about 10-15% of the total wing area.
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Old 10-05-2009, 01:33 AM
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thanks, Larry,

I knew there was a canard calculator on that site somewhere, but I just couldnt find it. I will make the distance from L/E to L/E 12" instead of 10"

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Old 10-05-2009, 02:02 AM
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That should get you in the air. Then after you fly it you can see if it needs tweeking.

Keep us posted!
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Old 10-05-2009, 02:35 AM
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should the canard be in the same plane as the main wing?

I was thinking maybe 2" lower than the main wing to help with weight bias/balance.

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Old 10-05-2009, 03:21 AM
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Im not sure what your trying to accomplish weight wise by lowering the canard. I doubt it will make much difference where you put it.

The vast majority of the weight will be in the motor and battery. Where they go will be the main factors as far as weight distribution.

Id put the canard where ever you think it looks best and is easiest to do as far as linkages and mounting.

Actually, before you get too far into that decision, Id decide if its going to be a pusher or tractor. Thats the major weight distribution question. Pick your motor and batteries out. Then play with how the plane balances with the motor on front or in back. That will tell you where the packs must go. Then design the rest around pack placement.

Too many times Ive skipped over that step only to find that the only place the packs can go already has a linkage in the way or landing gear or a brace or something. Its always something thats NOT easy to move!

From my experience, it will look better as a pusher. More jet like. But it will be easier to fly - especially if you hand launch - if its a tractor. You will also be able to fly slower if its a tractor - you'll have more airflow over the controlls at slooooow speeds from the prop.

As usual - each design step is a trade off
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Old 10-05-2009, 03:32 AM
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Well, I actually meany to say above....I mean to mount the canard above the main wing and build a profile fuse. Im not planning to use landing gear, just a skid on the fuse. It will definatly be a tractor...

As you can see on the DWG I'm thinking of a 2" stagger and the big bump on the bottom will give me enough clearance to keep from breaking a 9" prop...I hope. (unless I do a FAMOUS yard dart landing)

If I upped the stagger some more...lets say to 5" I wouldnt need so much "bump"and I could cut down some more weight/drag.....do you think it would help/hurt?

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