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Old Nov 14, 2014, 09:01 PM
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Joined Nov 2014
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maiden flight, tandem wing, dual edf instability

can someone help me trouble shoot this scratch built plane and tell me how tune/fix it

basically once it took off it kind of went to the left and throughout the flight it continued to turn left, i had my trim maxxed out for a right hand turn but it still wants to go left

is it my cog?
wing rock?
torque roll?

any ideas would be helpful thanks!!

here is the youtube link
Maiden Flight (2 min 7 sec)
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Last edited by brand_in; Nov 14, 2014 at 09:03 PM. Reason: cant see my video originally attached
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Old Nov 14, 2014, 09:23 PM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
2,856 Posts
It looks like it might be a little tail heavy , try moving the battery forward a little .

Do you have both motors' ESC's going into the receiver on a Y harness ? It could be that the right motor is putting out a little more thrust than the left motor , which would cause it to turn left . You can set up a mix with your throttle and rudder channel , then the rudder stick ( and trim ) will give you variable thrust between the two motors .

Al
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Old Nov 15, 2014, 02:12 AM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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Also, check if the left and right wing (wings) are parallel by looking at the plane from the front.
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Old Nov 15, 2014, 02:26 AM
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Joined Nov 2014
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thanks guys

yes both motors ESCs are hooked to a "y" harness, i will check if one of the motors is stronger, i should probably mix some rudder into the motors anyway.

I will definitely check the wings more closely, when i taped them it seemed to add some dihedral but maybe i didn't tape them quite the same and one has more than the other :/
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Old Nov 15, 2014, 08:31 AM
An itch?. Scratch build.
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South Wales U.K.
Joined Mar 2003
13,773 Posts
Some actual pictures of the model would help, the video shots are too far away to really see what is happening and why.

It looks like it is more a lifting body model, than a conventional model which has the wing area greater than the body area.

Short span models can be prone to roll, (dutch roll ?)

Have you used one of the canard cg calculators ?
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Old Nov 15, 2014, 10:58 AM
gpw
“There’s no place like Foam”
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United States, LA, New Orleans
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Although we know how you guys love LOUD rock , it might be better to actually hear the motors to better help determine what’s happening ... Being Blasted whilst thinking just makes me want to run away ...
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Old Nov 15, 2014, 12:25 PM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
2,856 Posts
Looking at the video , when your wife/girlfriend releases the plane it seems to YAW to the left , which makes me think it's differential thrust more than torque roll - although a narrow wingspan is more sensitive to torque roll .
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Old Nov 15, 2014, 01:22 PM
Fremont, CA
United States, CA, Fremont
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Unequal dihedral isn't that critical - it will just cause the plane to fly in a slight tilt. What I meant about the wings being parallel seen from the front is shown in the pic...
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Old Nov 15, 2014, 04:54 PM
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It could be any of the above (or a combination of all), plus some significant build asymmetry. Like maybe one of the winglets is not perfectly parallel to the center-line of the aircraft while the other is - generating a significant pull to the left. Or maybe there's unequal wing twist, causing a really strong difference in lift between the two wings (fore or aft set) such that you get a really strong left rolling tendency. Also, does it do the same in a power off glide? If yes, that would rule out differential trust issues. Also, are the motors perfectly parallel to the center-line of the aircraft? In any case, just for experimentation sake: Try making your control surfaces much larger so that the trim to the right will have a heftier effect. If that helps to get it flying straight in a power off glide, then you are almost certainly looking at a large asymmetry issue.
In the plane below I had massive asymmetry (very warped foam). I just mechanically set the "neutral" position such that one elevon was much higher than the other (via adjustment of the pushrod length from the servo to the control arm). Not very elegant, but expedient

Flight of Vectored Thrust Delta with takeoff landing (1 min 40 sec)
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Old Nov 16, 2014, 01:57 AM
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here's some pictures, the wings are parallel from what i can tell, there did seem to be some differential thrust so i mixed in some rudder and will be able to trim it in the field, also going to move cog forward, hopefully take it out again tomorrow morning wish me luck! and thx for your input
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Old Nov 16, 2014, 04:03 AM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
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Quote:
Originally Posted by brand_in View Post
here's some pictures, the wings are parallel from what i can tell, there did seem to be some differential thrust so i mixed in some rudder and will be able to trim it in the field, also going to move cog forward, hopefully take it out again tomorrow morning wish me luck! and thx for your input
Let us know how it turns out .

Is it your own design ? Here is one of my favorite tandem wing planes - it has control surfaces on the front wing as well as the back wing , all mixed as elevons for a fast roll rate and quick loops .

RC Flying Car Thing! (3 min 12 sec)
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Old Nov 16, 2014, 07:52 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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Excellent video. Thanks!!
Are plans available for it.??

Gord.
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Last edited by flypaper 2; Nov 16, 2014 at 08:05 AM.
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Old Nov 16, 2014, 03:05 PM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
2,856 Posts
Quote:
Originally Posted by flypaper 2 View Post
Excellent video. Thanks!!
Are plans available for it.??

Gord.
I don't know if RC SuperPowers still sells plans , here's his website

http://www.rcpowers.com/

and here's his email

http://www.rcgroups.com/forums/sendm...member&u=73210
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