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Old Feb 06, 2016, 06:08 PM
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Flight characteristics that cause squirley flight patterns

So I finally completed my Guillows Cessna 150 kit, and went out to maiden it. At first it needed a lot of rudder trim, and so I corrected it, and all seemed well... Tons of power and lift. That's when things went bad, it seemed like the silly thing could not fly level in roll, it would roll over and I would quickly correct, only to have it lurch back down in the direction I corrected with no input, and span downwards. This continued back and forth until the crash. I have no idea what the problem was, maybe the AS3X receiver I was using malfunctioned, but other than that I don't know... I would appreciate any advise or input on this problem. Thanks,
-Mark
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Old Feb 06, 2016, 08:10 PM
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Too large a motor (torque problem)and CG not correct. But there is no way for any of use to know if we weren't there or no video. How much experience do you have? maybe warped wings or ailerons with too much throw...Are you sure the control throws were correct and the as3x was set up correctly as in moving the correct direction in response to movements of the aircraft
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Old Feb 07, 2016, 11:36 AM
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If you have no warps in the wing and have the model balanced slightly nose down when suspended from the CG point indicated on the plans, and you have an appropriate size and weight power and RC system, the model may be able to fly. If the overall weight with battery pack is too much for the wing area, model will tend to stall unless it is flying fast. Small Guillows kit conversions to electric powered RC are not the best beginner's projects.
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Old Feb 07, 2016, 03:12 PM
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I built this model years ago, and it went from unflyable to one of the easiest flying models I have, due to about a 1 degree or so rudder misalignment and incidence mismatch. It was a good learning experience, as the excess positive incidence was on the right panel, compounding with p-factor. Had it been reversed, it may have flown fairly well. The same goes for the rudder misalignment. It favored right hand turns, pushing the tail to the left, along with dropping the tail due to the incidence mismatch. You now have a sidewinder. Had the rudder misalignment been in the opposite direction, I probably could have at least flown continuous left hand circuits. The nearly 1" dihedral is certainly not scale, but works well with RET controls. It could probably be reduced a bit, but probably not much to satisfy 5 degrees (common FF and RET high wing figure). Doing the math with an 11" wing panel using the TAN function, I believe it comes out to nearly 1". Weight wise it is probably on the heavy end, with a sheeted/Ekonokote covered fuse. The 5.2oz AUW is a non issue for this model, other than not being the slowest floater for it's size. I now reduce the positive incidence in these models a hair, although it's not really a problem other than being "trim to speed" sensitive.

Correcting the issues, this is now a "hand a beginner the transmitter" flying model. It's that stable and easy to fly.
Cessna 150 Guillows RC (2 min 39 sec)
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Old Feb 07, 2016, 08:57 PM
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Thanks for the input I am a very experienced flyer, but fairly new to balsa planes. I just finished up piecing the plane back together. I added some weight to the nose to balance it, as it sounds like it was tail heavy from what I've heard. I also replaced the as3x receiver with a standard one, using the same park 180 outrunner and linear 1.7g servos
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Old Feb 07, 2016, 09:01 PM
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Not very pretty but that's it
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Old Feb 07, 2016, 09:57 PM
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Probably a good idea to ditch the AS3X as you mentioned. There's no need for it on a model this size. I'd be concerned about reliability issues, given the added complexity. Tail heavy is certainly another issue also. I hate adding ballast, and had a few models years ago where I finally gave in and added the weight. In more recent times, mounting the gear forward has eliminated the need for ballast on pretty much every build. Sometimes you have to get as creative as chamfering servo horns to fit the servos in the cowl, but it eliminates the need for ballast. Actually overshot the CG on the little 16.5" FW190, and mounted the battery a bit back from where planned. All that effort of fabricating a motor mount box to house the battery, and it turned out not to need it. Good flying model, although at it's size it is a bit squirrely! Video's on the same YT channel as the C150.
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