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Need help balancing Edge 540T!!! What do these symptoms indicate?

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Need help balancing Edge 540T!!! What do these symptoms indicate?

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Old 10-31-2006, 11:11 PM
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Sessholvlaru
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Default Need help balancing Edge 540T!!! What do these symptoms indicate?

Hey all. I have a 70" Edge 540T with a YS 140 Sport. I have three flights on it. First two were extremely nose heavy, as I had to apply quite a bit of up elevator to keep her in a straight line (1/3 stick). I knew it was going to be nose heavy, but I figured I would see how bad it was. I ended up moving the motor mount behind the firewall (Dubro anti-vibe), putting the motor about 1 1/4 inches further back. This put the CG within in manufacterers recommeded range, but I don't trust the very poorly written instructions. I had also already moved the battery as far back as I could. I flew her this way today for the first time. She needed just a tad of up trim (3 clicks) to track straight. Shallow decent when inverted. Flew good in 'lazy flight mode.' However, when I applied full up elevator, it would do a 'wall' so to speak. It would instantly go vertical while not gaining any altitude and stall. Full rudder in a knife-edge also ended up making her stall/act funny. I do not have a crazy amount of deflection either, around 25 to 30 degrees. It just seemed much more squirrely than similar aircraft (Extras, Lasers) I have flown in the past. Does this sound like it still might be a bit nose heavy? The CG is not on or past the furthest recommended mark, so I don't think it is tail heavy..... Any advice would be appreciated. Thanks!
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Old 10-31-2006, 11:26 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

G'day Mate,
Did you go to full power when you gave it full up elevator, & it stalled?
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Old 10-31-2006, 11:42 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

No, this happened when traveling at about 1/3 to 1/2 throttle in level flight, then applied full elevator. 1/3 or so up elevator gave me a nice loop. Great for 'wall to hover' manuevers, but it was an extremely fast/almost violent transition to vertical. I am kind of boggled since it still decends slightly when inverted, making me think it is not tail heavy yet. However, the symptoms sound tail heavy, eg super touchy rear control surfaces. It floats in nice for landings now, and I almost tip stalled it. No down elevator needed to land. Guess I need a bit more than idle to keep it straight. I am going to try and dial in some expo, but I am confused by this. Thanks!
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Old 11-01-2006, 07:33 AM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Measure the airplane and enter the measurements into this online application. It will give you the NP location. Keep the CG at least 10% forward of that NP and you'll be safely "noseheavy".

http://www.geistware.com/rcmodeling/cg_super_calc.htm

The measurements are simple. They're explained in the application.

The NP (neutral point) is a simple thing. It's just not simple to calculate. However, the application does all the calculations. The NP is also not something that is based on opinion. It's proven. It works for Boeing, Rutan, Cessna, etc. and us.
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Old 11-01-2006, 07:37 AM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Keep in mind, however, that when you move the CG aft from a noseheavy location, the elevator is going to become more effective.

Newbies usually interpret this as the airplane losing stability. In fact, all that's happening is that the airplane's elevator moves less for the same effect. So, duh...... Expect to have a more effective right stick, and either reduce the elevator throw to begin with or simply move the stick less. The stability of the airplane isn't really getting less until the CG gets to the NP or aft of it.
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Old 11-02-2006, 08:22 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Well it officially balances at 4.25 inches from the LE. The instructions call for 3.5 to 4.35. Do you think I should experiment with moving the CG slightly forwards?
I broke the cheap ***** landing gear, so I will be unable to fly her until I can afford new gear. Here is a pic. Thanks!
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Old 11-02-2006, 08:36 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Your "wall" has pointed to the aft c.g. limit..
Move the c.g. forward, and reduce your elevator travel, unless you really need it for vigorous snap manuvers.
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Old 11-03-2006, 09:01 AM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

One thing that no one has asked is.......:

Have you checked your thrust? Have you done a thrust line?

On my 80" Yak I kept thinking it was too noseheavy when the CG was near tailheavy. Turned out that I had to add a little up thrust to the firewall (rebuilt before) to get it to trim out. Now it's a dream to fly with no input upright or inverted. This also caused it to land pretty hot since the thrust was pointing down when upright. Just something to check on.
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Old 11-03-2006, 09:10 AM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

The amount of throw you describe is a lot. Not a lot for 3D high rate, but a lot for regular flying. Set a lower low rate for normal flying.
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Old 11-03-2006, 12:40 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

I'm with the thrust angle theory. Moving the engine back 1 1/4" sounds too excessive from normal setup. Since the elevator isn't cantilevered and you're only using 1/3 elevator, it's got to be somewhere else. What corrections did you have to make during full bore level flight and inverted ?
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Old 11-03-2006, 12:56 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Just a few clicks of up elevator to fly level. Inverted flight was normal, with a slight decent.
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Old 11-03-2006, 01:28 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Yes, your CG to to far back for what you're used to/the amount of throws being used or both.
Inverted flight should need a resonable amount of down elevator with short coupled scale type designs.
Even long coupled F3A designs are dialed in to use some.
If you get it to far back they become squirrely and lack direction. It far far worse with IMAC types. They just become nasty little *******s when you get to far back.

The amount of up trim isn't alway a good reference because you could well have the incorrect incidence on the wing.
Find the datum line, lock the plane down and measure the wing incidence. You need at least .05deg positive. More likely 1deg.
Set it up and retrim.

You can't, in away have and aeroplane set up for both normal precision flying and 3D.
Everybody I know, and all the famous guy's QQ, CPLR etc etc all have two completely different set-ups for each discipline ( or should that be 1 discipline and a circus)
There are many pictiures showning the lead weights guys attached to their planes before the TOC freestyle events.
Only then do they move it back some.
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Old 11-03-2006, 06:33 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Your CG sounds like it's pretty far back.

Steps to test for CG:

1) Get your plane neutral by chopping the throttle back to idle and flying straight down. This will tell you if you have a wing incidence issues. If the plane pulls to the belly or canopy then you need to adjust the wing angle (or flaperons to cheat). Adjust until your airplane flys/falls straight down without pulling.

2) Chop the throttle and fly down at a 45 degree angle. If the nose drops you are nose heavy. If the plane pulls out (up) then you are tail heavy. If the plane continues without deviation then you are perfect. (make sure to chop the throttle when doing this and only at a downward angle.
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Old 11-03-2006, 07:12 PM
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Default RE: Need help balancing Edge 540T!!! What do these symptoms indicate?

Sounds good. I appreciate all the input....as soon as I get a new set of gear I will be sure to try these tips out as I can't wait to get her dialed in. Thanks again!
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