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help on balancing low wing planes

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Old 11-05-2012, 02:50 PM
  #51
da Rock
 
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Default RE: help on balancing low wing planes

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ORIGINAL: Bozarth

da Rock (I still don't know your real name),

I applaud your diligence. But it falls under the TLAR method if you apply science to part of the equation, and experience to the other. Specifically, how are you determining what the coefficient of lift is for your wing and tail? Or the wing's pitching moment coefficient? My guess is you are estimating. Which then leads to an estimated SM, which then leads to an estimated desired CG location. Which I would bet, falls somewhere between 25 to 35% of the MAC.

How do you learn of these coefficients for ARFs? I bet you estimate based on your experience. And I bet you know how it should feel when you fly it. And I bet you recognize there is a trade-off between maneuverability and stability, etc.
There is no ''correct'' cg provided it is within the static margin.

Measuring a cg location to the nearest 1/16'' means nothing. How do you like how the plane flies?

Measuring the cg to the nearest nth degree is like measuring how much hair the barber cut off.

Kurt
Sorry, Bozarth, but the important details pertaining to pitch stability imparted by the CG are really pretty simple. They're the wing chord, wing area, tail area and tail moment. None of the things you list affect static margin. It's pretty easy to see what does. Take a look at the list of inputs any of the online applications ask for so they can provide information as to where your model would need the CG to be for the SM you wish. A good one to look at would be http://www.geistware.com/rcmodeling/cg_super_calc.htm
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Old 11-05-2012, 03:08 PM
  #52
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Default RE: help on balancing low wing planes

We can't see the equation being used in the model. Coefficient of lift is normally one of the considerations. I bet they are set at an estimated value.

Kurt
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Old 11-05-2012, 03:16 PM
  #53
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Default RE: help on balancing low wing planes


Quote:
ORIGINAL: da Rock
The written word is about the worst communications us humans flog each other with.

What at least one of the most ''opinionated people'' has for motives is to provide enough detail that every beginner who comes through this swamp doesn't leave with just wet feet.

The point is for everyone to have a chance to understand most of this isn't an individual's opinion, and to understand how to find the mfg's suggested CG location with sufficient accuracy.
I _may_ understand your motives. The questions is, was it really necessary? The questions asked was simple and the answers would have been simple enough for anybody to understand. Now we are going into MAC and other parameters that would glaze over a newbie's eyes.

All the OP wanted to know is why the airplane needed to be balanced up-side-down, and if the nose needed to point up or down. The techniques and aeronautical terms could have been left out. Now it is really confusing for anybody trying to read thru this mess.

Rafael
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Old 11-05-2012, 03:27 PM
  #54
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Default RE: help on balancing low wing planes

Quote:
ORIGINAL: Rafael23cc


Quote:
ORIGINAL: da Rock
The written word is about the worst communications us humans flog each other with.

What at least one of the most ''opinionated people'' has for motives is to provide enough detail that every beginner who comes through this swamp doesn't leave with just wet feet.

The point is for everyone to have a chance to understand most of this isn't an individual's opinion, and to understand how to find the mfg's suggested CG location with sufficient accuracy.
I _may_ understand your motives. The questions is, was it really necessary? The questions asked was simple and the answers would have been simple enough for anybody to understand. Now we are going into MAC and other parameters that would glaze over a newbie's eyes.

All the OP wanted to know is why the airplane needed to be balanced up-side-down, and if the nose needed to point up or down. The techniques and aeronautical terms could have been left out. Now it is really confusing for anybody trying to read thru this mess.

Rafael

Party pooper........oh, wait. Go Chiefs.
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Old 11-05-2012, 04:11 PM
  #55
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Default RE: help on balancing low wing planes

"All the OP wanted to know is why the airplane needed to be balanced up-side-down, and if the nose needed to point up or down. The techniques and aeronautical terms could have been left out. Now it is really confusing for anybody trying to read thru this mess.

Rafael"

If the OP's eyes glaze over at this point (25 years operating and building acccording to his profile) he needs cataract surgery. He isn't a newbie and newbies can benefit from the exchange of ideas.

Bob

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Old 11-05-2012, 04:23 PM
  #56
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Default RE: help on balancing low wing planes

If you want your planes to fly level then you must balance and c.g. them level.
Ted
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Old 11-06-2012, 03:34 PM
  #57
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Default RE: help on balancing low wing planes

Quote:
ORIGINAL: retransit

''All the OP wanted to know is why the airplane needed to be balanced up-side-down, and if the nose needed to point up or down. The techniques and aeronautical terms could have been left out. Now it is really confusing for anybody trying to read thru this mess.

Rafael''

If the OP's eyes glaze over at this point (25 years operating and building acccording to his profile) he needs cataract surgery. He isn't a newbie and newbies can benefit from the exchange of ideas.

Bob
You'd be horribly surprised with some of people I have encountered in the 20+ years of me being in this hobby. They are quite content with what they know, and could care less about the rest.

Quote:
ORIGINAL: Bozarth
Party pooper........oh, wait. Go Chiefs.
I spend my time at the field or learning about my hobby, not watching grown men running around.

Rafael
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Old 11-06-2012, 03:54 PM
  #58
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Default RE: help on balancing low wing planes

We all bow down!

Kurt
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Old 11-07-2012, 07:36 AM
  #59
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Default RE: help on balancing low wing planes

Quote:
ORIGINAL: Rafael23cc

Quote:
ORIGINAL: retransit

''All the OP wanted to know is why the airplane needed to be balanced up-side-down, and if the nose needed to point up or down. The techniques and aeronautical terms could have been left out. Now it is really confusing for anybody trying to read thru this mess.

Rafael''

If the OP's eyes glaze over at this point (25 years operating and building acccording to his profile) he needs cataract surgery. He isn't a newbie and newbies can benefit from the exchange of ideas.

Bob
You'd be horribly surprised with some of people I have encountered in the 20+ years of me being in this hobby. They are quite content with what they know, and could care less about the rest.

Quote:
ORIGINAL: Bozarth
Party pooper........oh, wait. Go Chiefs.
I spend my time at the field or learning about my hobby, not watching grown men running around.

Rafael
I can't be surprised anymore. I'll give you some examples.

After informing a fellow flier about the care and feeding of Rx batteries on several occasions, he subsequently goes and flies and has a fly away. Dollars to doughnuts, the battery gave up the farm. I can't prove it because the plane is lost somewhere. On another occasion another flier was heard to say on a video that his batteries were at minimal voltage and that was good enough. After having his throttle stuck full open, he proceeds to fly around using up his batteries by performing maneuvers until he runs out of fuel. The batteries won that race. The result was a full bore lawn dart into the the earth. Another flier crashes when his plane is obviously tail heavy, fails to recognize the symptoms and continues to keep the aircraft aloft until he can no longer sustain any kind of control.

Fifty-five years in the hobby and no, I can't be surprised anymore. Talking to these people is fruitless.

Bob

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Old 11-07-2012, 09:48 AM
  #60
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Default RE: help on balancing low wing planes

retransit,

You are starting to sound like Tired Old Man.
You know everything, and can't tolerate the ignorance of your peer group.

Greg
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Old 11-07-2012, 02:25 PM
  #61
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Default RE: help on balancing low wing planes


Quote:
ORIGINAL: OldRookie

retransit,

You are starting to sound like Tired Old Man.
You know everything, and can't tolerate the ignorance of your peer group.

Greg
Don't confuse ignorance with stupidity. Ignorance stops when advise is given. Stupidity follows.

Rafael
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Old 11-07-2012, 02:50 PM
  #62
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Default RE: help on balancing low wing planes

I never mentioned stupidity. Don't add things I didn't mention.

My original observation of your comments on this post still reflect your personality.

Still standing by my original comment.

Just saying...Ha.

Greg
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Old 11-07-2012, 06:11 PM
  #63
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Default RE: help on balancing low wing planes


Quote:
ORIGINAL: OldRookie

retransit,

You are starting to sound like Tired Old Man.
You know everything, and can't tolerate the ignorance of your peer group.

Greg
To the contrary, I do not know everything and will be the first to admit it.

I can stand the ignorance. We learn from other's experience and knowlege, and that includes me as the student. What I cannot tolerate is a mind set where a bit of attention to detail will defuse a bad situation concerning a fundamental safety issue. If you want to crash your plane due to unsafe practices, go ahead, but don't do it with others around and in a setting that can have a detrimental effect on those people.

Bob
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Old 11-08-2012, 06:42 AM
  #64
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Default RE: help on balancing low wing planes


Quote:
ORIGINAL: OldRookie

I never mentioned stupidity. Don't add things I didn't mention.....
Greg
Missed the point completely....

Have a good day.

Rafael
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Old 11-08-2012, 07:04 AM
  #65
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Default RE: help on balancing low wing planes

Agreed.

Bob
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Old 11-09-2012, 08:51 AM
  #66
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Default RE: help on balancing low wing planes

Hi!
Long fingers???
What do mean? Just hold the fingers under the wing at the supposed C of G What could be more difficult?
If the plane sits okay go out and fly it! If it doesn't behave good...change the C of G (Move servos and batteries )and go out and fly again. Repeat this process untill you are satiesfied with the flight caracteristics.
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Old 11-09-2012, 01:28 PM
  #67
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Default RE: help on balancing low wing planes

My answer to that is, get it right the first time and you won't have to move components. Even if you do, it can be limited to a battery pack, which is easy to do. Servos require changing mounting location and pushrods if you want to fly to confirm your CG choice.

I've said it before, but it bears repeating. It is difficult to hold a 23lb. plane with two fingers, especially if it is covered with fabric. I wouldn't want to place that concentrated force on the fabric. That is why I use the hook, cord and plumb bob. By using a balancing device, no matter what it is, you can move components while on the balancer.

Bob
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