At times ive noticed that planes will wiggle their tail as they fly. Usually happens after making a change of some sort(cg etc). Why do planes do this.... is something I should be looking out for to correct?

I too would love to know

It can be many things. Rudder servo could be weak , linkages could be loose , pull pull wires could have slack , rudder could be glitching (flopping with a mind of it's own) , could be the wind , controls could be too touchy (may need more expo) ,

what plane? servos? engine? engine mount? rx? , tx?

It's a female plane

Thats a good one!

hm I've seen that happen on one of my foamies :S delta wings no rudder there very odd

Or it could be aerodynamics related... like a too small vertical stabilizer, or an airframe operating outside of it's designed flight envelope. For example, the Kaos is notorious for wagging it's tail when flown to fast. Could be propwash, tip wingtip vorticies, turbulence from the canopy, etc...

It's just a happy plane!

A couple of other terms to describe that:
The plane "hunts" in yaw.
The plane is unstable in yaw.

My Meister Corsair hunts in yaw. They say the full scale one did too. I don't mind a bit.

The early bubble-canopy P-47D was unstable in yaw, and they added a little triangle piece between the vertical stabilizer and the fuselage. Cleared it right up. Not necessary with the razorback P-47 because the fairing behind the pilot provided some vertical stabilizing area.

There's another effect, rudder flutter. I know a guy who built a SPAD with lots of extra rudder area. Wouldn't go faster than about 20 mph before the rudder would flutter like mad.

Interesting phenomena.
Dave Olson

The only times I've seen a "wiggling tail" were due to the following:

- Pilot doing this purposely
- Too much slop on a Pull-Pull setup.
- Flutter ( see previous )
- wind pushing the plane.
- Pilot coming out of another manouver, such as a knife edge.

OUt of those : its might be...flutter(but its at low crusing speed), Wind, or Pull Pull slop.

Ill make sure to check the servo and pull pull tension.

I was seeing my planes doing it today, turned out to be a loose nut behind the sticks, I was bumping the stick when I was using the throttle. It was also happening a lot when I would come out of some stunts, it was me letting go of the rudder too fast. Several other times it was just me fooling around with the rudder. And yes, my planes are all girls!!

Apparently it's called "fish tailing". I had a Protech Sundancer that did it as well. Had something to do with fluid dynamics and the cure was to add split fuel tubing to the edge of the rudder thereby forming some sort of a spoiler. In the end I couldn't be bothered and the aircraft was written off in a mid-air with its tail still wagging....

MAYbe its flirting with you and you are taking notice of its intentions ,,,, It wore an itcy bitsy tinny winny pokodot bikinini
( BLAH BLAH BLAH) and maybe to short a fuselage

I like that, Gray Beard.. A loose nut behind the stick. Yeah, that seems to fit many pilots, me included.

CGr.

CG, I'm not going to put into print what else I did that is going to mess up another month of my flying. {again!!} I'm having a real bad run of operator malfunctions this summer.
Only thing I can say good is my flying was beyond reproch, I was so on I dazzled myself. I even flew my hot rod HOTs a couple of times and for once it didn't get away from me!! I was so proud of myself I came home and made up songs then called my neighbors and sung my praises!! It was one of those days I was even proud to know me.
Well, other then that one little problem anyway.

There is a fine line sometimes between the right proportions and visa-versa for what makes a plane groove........assuming that there aren't any mechanical reasons for a loose rudder.

For yaw stability, the side view of the whole plane needs to be considered. Crude execution of design, like 3/8" slab tail surfaces with blunt edges and crooked fuselages that need rudder trim to correct can't help much. Same goes with hinge gaps

I think the case of the plane with a big nose / too little tail is what creates most of the swimming tendencies that can't be trimmed out or corrected with slop free linkage.

Ugh, you know you've been flying helicopters too much when your first thought is, "he needs to lower the gyro gain."

I don't have enough hands to fly helicopters.. []

Gray Beard.. sounds like you had a good day, considering, eh?

CGr.

Even a blind hog finds an acorn once in a while. Now if I could quit crashing my radio I'm sure I could have more days like that!![>:]

Mainly an aerodynamic thing if all linkages etc. are good. Usually too little vertical fin area.

My Top Flite Corsair did that and all the others I have watched did it. Look up "Dutch Roll" and see if that is what you are asking about.

http://en.wikipedia.org/wiki/Dutch_roll