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Old Oct 09, 2012, 05:50 PM
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royalstar05's Avatar
United States, MA, Haverhill
Joined Jun 2012
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going to the left on takeoff

I have built 3 planes now and have noticed one thing before they crashed. All the planes on take off want to roll to the left. The planes that was using didnot say anything about offsetting the engine to the right. Is there something I am missing when building the planes. I have flown gas engine planes for 7 years all kits you buy pre cut. I have built 2 trainer plans both without ailerons and one low wing plane with ailerons. thanks for the help
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Old Oct 09, 2012, 06:35 PM
James L
TANGOSIERRAROM's Avatar
Beck Row Mildenhall
Joined Mar 2009
787 Posts
Assuming you managed to fly your ic engine planes OK, then yes when you are building foamies or indeed any model the motor will often need a bit of right thrust for a tractor set up, to counter torque / p effect or whatever you want to call it. However it could also be that you are tipstalling so without seeing what is happening it is difficult to say it is definitely this or that.
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Old Oct 09, 2012, 07:29 PM
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United States, OH, Troy
Joined Jan 2008
77 Posts
Most likely what is happening is a combination of things.

1. If you try to take the airplane off the ground too early the airplane will rise off the ground a little bit, until the lift decreases to a point that it can no longer fly. This would happen because as you take off you fly out of ground effect.

Ground effect: http://en.wikipedia.org/wiki/Ground_effect_(aircraft)

But, I'm guessing on your experience you already knew that, whether formally or informally.

2. Assuming the airplane is at an acceptable flying speed when the airplane is flying straight forward, the instant you rotate the nose up to take off, the p-factor of the propeller increases, pulling the nose to the left. This would cause the left wing to stall because you are increasing the relative wing sweep to the oncoming air. Positive sweep (wing tip goes back as it moves out from the fuse) decreases lift more than negative sweep (wing tip is forward of the root on the fuse). Because the left wing is stalled and the right wing is not, it would snap to the left and crash.

P-factor: http://forums.jetcareers.com/threads...iagram.102699/

Another possible cause would result if you didn't know the information from section 1. This could be problematic now because usually most trainers and kit planes are very forgiving airframes. If you rotated too early on the takeoff roll it would be okay because the airplane would have accelerated enough to fly away once it had left ground effect. There is no guarantee of this on a scratch built airplane.

I would suggest a little right thrust on those "bad boys", it can't hurt too much.

Hope this helps, and happy modeling!
Scott
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Old Oct 10, 2012, 07:02 AM
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United States, MA, Haverhill
Joined Jun 2012
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Thanks I thought that is what I need to do last night I move the rudder trim all to the right and the plane took off straight. With a little right thrust on the new plane build I should be fine
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Last edited by royalstar05; Oct 10, 2012 at 07:47 AM.
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Old Oct 10, 2012, 12:00 PM
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United States, OR, Salem
Joined Jan 2012
286 Posts
It took my son about 5 crashes on take off for him to listen to me and not give it full throttle. Any of my foamies will pull hard left if you slam the throttle forward. Easing into the throttle really helps.
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Old Oct 11, 2012, 01:57 PM
no points for speed
Auckland, New Zealand
Joined Oct 2009
22 Posts
I have an aerobatic park flyer that weighs about 14 oz. It also turns left on the takeoff run. It's a tail dragger and the best way I have found to keep it going straight is holding full up elevator to keep the tail wheel planted. And I hold some right rudder too. With all that up elevator it pops off the ground. I quickly back off the elevator to keep it in a shallow climb.
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