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Old Nov 10, 2004, 12:55 PM
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Bajazz's Avatar
Steinkjer, N-T, Norway
Joined Mar 2001
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Help!
Zagi death spiral

I have a Zagi copy, and all the time I get into death spiral. It fly's very beautiful, but all af a sudden it goes down. I thought it was receiver problem but never experienced glitching otherwise with the Rex. Anyway, I tried a schultze with the signal light showing no problems. Same problem all the time. Fly for some seconds, turns, loops, and suddenly from a nice level flight, for no reason it decides to spiral down. What the heck is going on???
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Old Nov 10, 2004, 01:10 PM
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MGBGTRacer's Avatar
USA, VT, Springfield
Joined Jan 2004
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are you going too slow? CG too far back?
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Old Nov 10, 2004, 01:46 PM
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London Heathrow, Great Britain (UK)
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if you pull too had on the sticks its not hard for one of the elevons to quickly become an air break.
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Old Nov 10, 2004, 03:26 PM
Retired USAF, A&P mechanic
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United States, WA, Puyallup
Joined Jul 2001
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if you are not going to slow, straight and level, and it all of a sudden spirals down, sounds like you have interference problems. either tx or rx or wiring.
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Old Nov 10, 2004, 05:04 PM
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I have heard problems like this over and over main contributors: CG to far aft and too large of elevator control throws, look at these two things first.
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Old Nov 10, 2004, 05:09 PM
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United States, CA, Bear Valley Springs
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What Lightnin said.

mw
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Old Nov 10, 2004, 05:47 PM
Got more toys than my kid
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USA, CA, Fremont
Joined Sep 2004
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Well, assuming it is NOT your radio (though that is my first guess):

How's your hinge-work? If the tape is lifting, it can cause a part of the aileron to rise up and become an air-brake.

How rigid are your wing-tips? If they are of a very thin and flexible material, they may warp at high speeds and cause all kinds of mischief. I had to replace my old-style Zagi wingtips (thin plastic) with 3mm depron to get some rigid yaw stability.

Is your motor-mount secure? (This is just a shot in the dark).

And, as the others say, your CG may be too far aft. You won't notice a problem unless you pick up speed or haul on the elevator.
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Old Nov 11, 2004, 06:38 AM
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Bajazz's Avatar
Steinkjer, N-T, Norway
Joined Mar 2001
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Quote:
Originally Posted by MGBGTRacer
are you going too slow? CG too far back?
No, as I said: "from a nice level flight" it suddenly goes into a spiral. It happens suddenly for no reason at everything from 1/3 to full trottle. As I said, "It fly's very beautiful", that means no CG problems. Trimmed it to float nice.
Quote:
Originally Posted by Ænima
if you pull too had on the sticks its not hard for one of the elevons to quickly become an air break.
Don't pull hard on the sticks. It's set up with small throws for trainer mode.This thing can happen when the wing is floating perfect level at 2/3 trottle and the stick is dead center.
Quote:
Originally Posted by Ronbo
if you are not going to slow, straight and level, and it all of a sudden spirals down, sounds like you have interference problems. either tx or rx or wiring.
I've used both receivers in different planes, never had any problems.
Quote:
Originally Posted by Lightnin
I have heard problems like this over and over main contributors: CG to far aft and too large of elevator control throws, look at these two things first.
Exactly what I did, think I've sorted out those variables at first.
Quote:
Originally Posted by macr0t0r
Well, assuming it is NOT your radio (though that is my first guess):

How's your hinge-work? If the tape is lifting, it can cause a part of the aileron to rise up and become an air-brake.

How rigid are your wing-tips? If they are of a very thin and flexible material, they may warp at high speeds and cause all kinds of mischief. I had to replace my old-style Zagi wingtips (thin plastic) with 3mm depron to get some rigid yaw stability.

Is your motor-mount secure? (This is just a shot in the dark).

And, as the others say, your CG may be too far aft. You won't notice a problem unless you pick up speed or haul on the elevator.
Hingework is fine, very compact, no flutter from links either. Wingtips are coroplast, about 4-5 mm, seems very stiff. Motor is strapped + doublesided taped on. Don't move at all, in fact at the last crash the motormount got torn off, but the motor stayed on the mount.
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Old Nov 11, 2004, 09:20 AM
Got more toys than my kid
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USA, CA, Fremont
Joined Sep 2004
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Well, I'm stumped without being able to witness it myself. One thought is that your power system is generating much more noise than on your other planes, so that a well-tested receiver will still misbehave.

Have a person hold your wing and start working the throttle up and down while you walk away with the antenna down. See how far you get before the holder sees a "bounce" in the elevons. Does the bounce only occur with throttle applied?

Is this a brushed or brushless motor. If brushed, you may need to add some capacitors to the case of the motor to reduce noise.

Another option is to install a "choke" between the receiver and ESC plug.

Is there a carbon-rod on your wing? Make sure your antenna does not run parallel to it.

I'm out of ideas from here.
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Old Nov 11, 2004, 09:33 AM
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Perth, Australia
Joined Mar 2004
872 Posts
Might be a faulty servo, try swapping servos and see if it spirals in the opposite direction.

Ron...
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Old Nov 11, 2004, 09:43 AM
Oldie but goodie
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United States, CA, Orange
Joined Jun 2003
3,890 Posts
At one time I experimented with the motor's thrust angle on my wing.

Normal mounting for my wing is to follow the airfoil (prop pointing slightly downward). If I raised it to more horizontal, the wing would tip-stall quite easily and come spiraling in without warning.
I left well enough alone and she flies great now.
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Old Nov 11, 2004, 10:03 AM
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Well if you have tried all of that and you still have the problem try some larger winglets.
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Old Nov 11, 2004, 10:54 AM
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USA, TX, Leander
Joined Jul 2001
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Friends don't let friends fly Zagis!
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Old Nov 11, 2004, 12:48 PM
"Bible Thumper"
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United States, AZ, Tucson
Joined Mar 2001
1,924 Posts
Pete, Pete, Pete....didn't you pull maggot covered meat trays out of the garbage to build that tiger moth???
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Old Nov 11, 2004, 01:45 PM
Launch high. Fly low.
United States, CA, Lake Elsinore
Joined Aug 2003
4,171 Posts
Yes it might be a faulty servo.
I've had this happen to my Unicorn. I changed the servos and the problem disappeared.

hth,
jc
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