Jester241

Ever notice your planes tail seems to sag during level flight somedays? I noticed on a couple planes at different times thier tails seem to sag. Seems to happen randomly on different days. Makes them kinda climb when turning too. Either I'm crazy or my planes get tired and the tails drag [sm=bananahead.gif]. I thought maybe it could be the air temperature or pressure or wind or something. I usually keep my planes pretty nose heavy too,and they seem to fly great most of time except for that stange day....and the next day I dont notice it again. Any know what makes this happen? Could it just be I'm nuts and thier tail heavy? I would think it would take a REALLY tail heavy plane to actually make the tail visually sag in flight....

thoughts?

Gray Beard

My Feedback: (-1)

????? Odd but yes, kinda? I never gave it a lot of thought, I'm not a real deep thinker but I have always wondered why I can fly a plane and have it in perfect trim today and the next day I have to give it a couple of beeps of trim. Doesn't happen a lot in the summer?? Weather?? Now you have me wondering and doing that thinking stuff, makes my head hurt!!

Jester241

Yeah....if I had to guess it think it does happen more when its cold maybe. I dont know though,probly just nuts......


and I've been starting alot of posts with "yeah" lately. Dont know whats up with that either.......

Live Wire

Temperature and humidity do change control action.

dignlivn

Jester,

I've noticed on my GP 40 Stik, and it
is slightly nose heavy also.

Bob

nobodytwo

The term is called adverse yaw. It is caused by the down aileron increasing the drag on that wing, and resists the turn, so the plane acts like its tail heavy. The colder the air the more the drag. Either manually add a little rudder with your ailerons or add a "mix aileron and rudder" and the sagging tail will go away.

Happy Landings!

RCVFR

My Feedback: (7)

Its probably gravity surges. Or could be the effect of Solar Flares.

w8ye

My Feedback: (16)

I have thought about this for some 50 years and I'm firmly convinced that it is the effect of left over residual from the Big Bang

opjose

Many ARF's have the fuel tanks just aft of the firewall but in front of the C.G.

As the fuel runs down the plane gets heavier towards the tail, but not so much that the plane is uncontrollable.

In turn as the plane slows down, the lift generated by the elevator diminishes, and when coupled with the aft c.g., you get a pitch up of the nose sometimes just before landing...

You could move the C.G. forward to offset this.

When the air is colder the effect is more pronounced as the main wings continue to develop lift in the denser air, but the flat tails stall out earlier.

This leads to what you've seen, particularly on 3D type planes.

I have a few planes purposely set up for 3D and this happens all the time with them.

-

Or


Isn't "tail sag" something that happens to women over a certain age?

w8ye

My Feedback: (16)

I have had several Ultra Sticks and at low throttle settings they will fly noticeably tail low. You give them full power and they are fine.

I have had a LT40 ARf for some 10 years and it didn't fly tail low when slow because it had about 8 degrees positive incidence in the wing. but at higher power settings the trim would change and the plane would climb. I made a shim to go under the rear of the wing to reduce the tendency to climb. Now it goes around tail low when flying slow. It is a great landing plane though

snacker

I have noticed this on my first real 3d plane myself. I noticed on the first flight that the tail was drooping after about ten minutes of flying. I knew it had to be a change of cg due to the tank emptying out.

Now I just use it to know when its time to bring it in. Built in timer I guess...

Stickbuilder

Take a look at the LT 40 photo. Notice the relationship of the bottom of the wing to the horizontal stabilizer. Imagine what the airplane would do if you were to either raise the leading edge of the horizontal stabilizer, or raise the trailing edge of the wing. All airplanes have what is called incidence, and that term is used to describe the wing or other horizontal flying surface relative to the datum line of the airplane. That datum line is normally an imaginary line drawn from the front to the rear of the fuselage, and is based on the centerline of the engine crankshaft, and or the fuselage crutch. If the leading edge of the wing is higher than the trailing edge, then the wing in flight will still try to remain flat (level) and you can see what the airplane will try to do relative to the wing. Now look at the horizontal stab, and you can see the effect of the wing being level. On the LT 40 in the photo, the leading edge of the stab will be low (incidental to the wing bottom), and the airplane will try to climb (which will make the tail appear to be draggy). The more throttle you give the plane, the more this ballooning is evident. You might try adding a shim to the trailing edge of the wing to raise it slightly (don't get carried away here), or remove a little of the down thrust in the engine (again don't get carried away). Sometimes this is a design flaw of the model, and you just have to add down trim, and live with it. It's good that you newer guys are noticing these things, and are asking questions about it, rather than just trimming it out and figuring that it's something that they all do. They do not.

Bill, AMA 4720
WACO Brotherhood #1

jetmech05

yes as I get older I have noticed this.....but I never pointed it out....

BigHog

My Feedback: (1)

Yes, before I was married, and I was much younger. After a few beers, does it really matter?

goirish

I had a soggy one, once.

CGRetired

My Feedback: (1)

Hey Irish.. Mine drags.. not sags.. ha.. oops.

CGr.