CJKling

My Feedback: (1)

Hey guys,

Interesting problem I'm having---

Funtana .40, Saito .82, Sullivan Flying Wires kit on the tail, Hitec HS-645MG Hi-torque servos all around except throttle (single elevator servo)

My problem-

Whenever I pull hard up elevator, whether in a bank or going vertical, in a loop, etc......, the plane banks to the right pretty hard. I've checked my lateral balance and it appears to be fine and I do not have any program mixes on my transmitter that cause the plane to do this. When I attempt to do a loop, it comes out looking more like a barrel roll. The only things that I could think of was the lateral balance and possibly(?) the elevator flexing slightly......I do not know what to do? any suggestions?

Thanks guys

Dealspeed

My Feedback: (17)

Strang mine did the same thing couldnt figure it out so i sold it and got a harrier

richohealey

dude, it's snap rolling. i'd bet the servo is on the right half??? you either need two servos or a stronger elevator setup.

CJKling

My Feedback: (1)

How would you suggest strengthening the elevator?

Banche

There was two other threads about this that I have seen and it all makes really good sense. It is a problem with all the planes. The elevator is week, push down on the right half when it is fully deflected and the left one also and decide for yourself!!!!

use two servos!!!

idvir

I'm flying a funtana 40 w/ an O.S 91 4 strok. when you pull up you give it full thrutle, the plane banks to the right because of the torque of the engine. you can program you transmitter to correct left rudder when you push the thrutle all the way.
try that first. i have only one servo on my funtana. i wouldnt put another servo before i check what i told you.

just my opinion...

Not24

My Feedback: (1)

For what it's worth, the 90 size has two elevator servos and it does the same thing if you are rough on the sticks. That's why mine is hanging on the wall and my gear is in another plane. Go figure.

3dbob37n

We have three Funtana 90's and a 40 flying at our club and they all, I mean all, pull to the right when you pull up quick.
No, it's not torque. Torque would pull it to the left, not the right. It can't be weak elevators either because not all of the Funtana's would have a weak right elevator.
All of our's have exactly the same amount of up elevator on both sides.
They do it on high rate as well as low rate.
Personally, I wonder if it is connected in some way with disturbed air flow over the vertical fin.
Go figure.
If anybody can come up with an answer, please let us all know because it seems all Funtana's have the same problem.

3dBob

TT2

My Feedback: (13)

Guys, I'm willing to bet that the planes are snapping out when the elevator is yanked. If the setup is correct (equal amount of throw through entire elevator travel, sufficient servo torque, lateral balance checks out OK) then it's most likely a CG and wingloading issue since the amount of elevator throw is probably the same for all planes. I've seen this tendency in nearly EVERY plane I've owned in the past six years or so of flying 3D aerobatics.

It seems the trend is to put grossly overweight engines on these airframes for more power. When the larger engines (like Saito 150s and OS 160fx) are used the takeoff weight is going up AT LEAST 1.5 lbs. That's going to change the flight characteristics BIGTIME. It will detract from the 3D performance and elevator induced snaps will be more prevalent.

Also, the elevators are more effective as the CG moves aft and the snapping tendency will lessen. Try this experiment: Decrease your high-rate elevator servo travel just until the plane will no longer snap when ONLY full-stick elevator is applied. Now, shift the CG rearward a small amount. Remember your elevator rate setting. Add more elevator travel back in. You will be able to add more elevator throw and not snap with the CG further aft. I flew my prototype 30% Edge 540 (1440 sq in wing, 87" span, 15.02 lbs RTF dry) for the first time on Monday. With a fairly conservative CG the plane wanted to snap a bit in walls and wing rock in harriers...always favoring the right side. I moved the CG back for test flights 4,5, and 6 on Saturday. Not a major CG change, but it was a phenominal improvement! There wasn't the slightest hint of wing rock in harriers and walls were extremely crisp with the wings ending up totally horizontal with not even the slightest twitch. The CG is still a bit more forward than 'pitch neutral' (it still drops toward the ground when inverted flying dead level) so I still have TONS of latitude for improving the 3D qualities. I'm tickled to death!

Anyway, when you do the experiment, BANG the sticks quickly...applying the elevator too slowly can lead to another 'problem'. I was having a discussion with a few guys at a fly-in on Saturday regarding snapping during walls. One was flying a 35% Carden Extra 300L, one a 40% Carden Edge 540, one flying a 40% Carden CAP 232...I was flying my 'little' 30% Edge 540 prototype. My buddy flying the CAP noticed that unless he 'forced' the plane into a wall, the plane would snap. The conclusion that we all reached is that it's better to pull HARD into walls not just because it looks cooler, but because it stalls both wings quicker and more predictably. If the elevators are applied more gently, one wing half may stall before the other resulting in snapping. It is possible that the lifting and stalled wing could shift from side to side...this oscillation is referred to as 'wing rock' but is usually more noticeable in a harrier since the maneuvers' duration is longer. I have had my share of planes that wouldn't enter a harrier unless you BANGED the elevator to get the wings stalled quickly...you couldn't just gently pull back the stick and wait for it to stall.

Keep it light, move the CG back and don't be a sissy when entering walls and harriers, and I'm willing to bet that the problems go away. Keep us posted on the progress. I don't fly a Funtana 90 any more (gassers and foamies for me) but I think they are an excellent platform for learning 3D flight and a tremendous value.

-Tom

Razor-RCU

My Feedback: (50)

Another thought....

Engine thrust

TT2

My Feedback: (13)

Whoops...missed that one! Good call.

-Tom

CJKling

My Feedback: (1)

OK, thanks all, I'll try moving the CG back slightly and see what happens...And keep you posted, there is a tremendous amount of engine thrust in this plane..