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Balancing heavys - 2/7/2009 5:05 AM   
YOADRIAN


 

Posts: 96
Score: 100
Joined: 12/26/2007
Last Login: 5/18/2013
From: Miami, FL, USA
Status: offline 		My planes are starting to get big and the cg machine no longer is any good because of the size. using fingers is ok but i would rather be right on with the big ones. Any ideas would be great or has someone come up with a better system.

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RE: Balancing heavys - 2/7/2009 5:25 AM   
exeter_acres



Posts: 7455
Score: 116
Joined: 9/22/2004
Last Login: 9/24/2012
From: Johns Creek, GA, USA
Status: offline 		Have the plane all assembled RTF minus fuel. Find a place where you can put the nose of the plane up against a wall. Take a level and prop up the tail wheel till the fuse is sitting level. Your gonna have to take the hatch off in most cases to set the level on.

Once the plane is sitting level, mark on the ground the two points where the main wheels are with masking tape and draw a line right where the wheels contact the tape. Then make a mark where the center of the tail wheel sits in the same manner. Its gonna be on whatever you propped the tail up with. (I use magazines)
Its also a good time to measure from the wall, how far back the recommended CG is. Save that number for later.

What you are looking for at this point is the distance to each wheel from the tip of the spinner. (which should be touching the wall at this point)
I use a long straightedge to get the distances

Lets say you come up with theses numbers:
LH main - 22 inches
RH main - 22 inches
Tail wheel - 70 inches

Now get a scale and place it under each wheel individually. You will have to re-adjust the other wheels to keep the plane sitting level. Add more magazines.
(If you have three scales you can get the weights at the same time but make sure the plane is level)
Remember to put the hatch on after you level the plane before you weigh each wheel. You gonna wind up with three weights. One for each wheel.

Lets say you come up with these numbers
LH main - 9lbs
RH main - 9lbs
tail wheel - 5lbs

Now its just a simple math problem to find where the CG sits right now on the plane.

Weight x ARM (distance) = Moment
22x9=198
22x9=198
70x5=350

Now add the total of all the moments and the total of all the weights.
Weights 9+9+5 = 23lbs
moments 198+198+350 = 746

Then divide the total moments by the total weights.
746 divided by 23 = 32.43

That number 32.43 is "in inches" how far back from the tip of the spinner to where the plane balances right now.
Compare that to the distance that you measured earlier to the recommended CG location.
If you are off one way or another adjust items then recalculate the weights. The distances (or ARM's) aren't going to change so you already have those numbers.


It may sound confusing and a lot of work but it really only takes about ten minutes to do it.

This is generally how full scale planes are balanced. You cant go lift one of them by your fingers or stick it on a CG machine.

Try it......

Originally written by Wayne Geffon

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RE: Balancing heavys - 2/7/2009 6:50 AM   
YOADRIAN


 

Posts: 96
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Joined: 12/26/2007
Last Login: 5/18/2013
From: Miami, FL, USA
Status: offline 		Not bad at all exeter so i just do what i learned in ap school. Funny I am rebuilding two 1947 cessna 140s i own and it did not even cross my mine to do it the same way lol. Now to look for some small scales. Thanks for the help guy.

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RE: Balancing heavys - 2/7/2009 8:19 AM   
Crash Campbell


 

Posts: 516
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Joined: 4/18/2007
Last Login: 9/28/2012
From: Port MacquarieNew South Wales, AUSTRALIA
Status: offline 		Hi,

There are many ways to skin a cat or find the CofG. This device makes it easy.

http://home.mindspring.com/~the-plumber/Vanessa%20CG%20Machine.htm
Cheers,

Colin

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RE: Balancing heavys - 2/7/2009 8:59 AM   
mimhoff


 

Posts: 234
Score: 100
Joined: 10/9/2004
Last Login: 1/8/2012
From: San Antonio, TX, USA
Status: offline 		Yoadrian Not sure what CG machine you are currently using (Great Planes maybe?) Sig is coming out with a Sig ProBalancer that appears to be quite a bit more robust than the GP CG machine. I have not seen one yet but I have one ordered fromTower for 39.99 scheduled to arrive early this month.



Mark


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RE: Balancing heavys - 2/7/2009 2:20 PM   
sowega flyer



Posts: 359
Score: 105
Joined: 8/1/2006
Last Login: 3/30/2012
From: Pelham, GA, USA
Status: offline 		I use 2 wooden ladderback chairs from the kitchen. Nothing fancy, but uncomplicated and free. My wife supllies an extra pair of hands if needed.

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RE: Balancing heavys - 2/7/2009 8:42 PM   
OldScaleGuy



Posts: 1903
Score: 120
Joined: 12/19/2005
Last Login: 5/19/2013
From: Seymour, IN, USA
Status: offline
quote:

ORIGINAL: exeter_acres

Have the plane all assembled RTF minus fuel. Find a place where you can put the nose of the plane up against a wall. Take a level and prop up the tail wheel till the fuse is sitting level. Your gonna have to take the hatch off in most cases to set the level on.

Once the plane is sitting level, mark on the ground the two points where the main wheels are with masking tape and draw a line right where the wheels contact the tape. Then make a mark where the center of the tail wheel sits in the same manner. Its gonna be on whatever you propped the tail up with. (I use magazines)
Its also a good time to measure from the wall, how far back the recommended CG is. Save that number for later.

What you are looking for at this point is the distance to each wheel from the tip of the spinner. (which should be touching the wall at this point)
I use a long straightedge to get the distances

Lets say you come up with theses numbers:
LH main - 22 inches
RH main - 22 inches
Tail wheel - 70 inches

Now get a scale and place it under each wheel individually. You will have to re-adjust the other wheels to keep the plane sitting level. Add more magazines.
(If you have three scales you can get the weights at the same time but make sure the plane is level)
Remember to put the hatch on after you level the plane before you weigh each wheel. You gonna wind up with three weights. One for each wheel.

Lets say you come up with these numbers
LH main - 9lbs
RH main - 9lbs
tail wheel - 5lbs

Now its just a simple math problem to find where the CG sits right now on the plane.

Weight x ARM (distance) = Moment
22x9=198
22x9=198
70x5=350

Now add the total of all the moments and the total of all the weights.
Weights 9+9+5 = 23lbs
moments 198+198+350 = 746

Then divide the total moments by the total weights.
746 divided by 23 = 32.43

That number 32.43 is "in inches" how far back from the tip of the spinner to where the plane balances right now.
Compare that to the distance that you measured earlier to the recommended CG location.
If you are off one way or another adjust items then recalculate the weights. The distances (or ARM's) aren't going to change so you already have those numbers.


It may sound confusing and a lot of work but it really only takes about ten minutes to do it.

This is generally how full scale planes are balanced. You cant go lift one of them by your fingers or stick it on a CG machine.

Try it......

Originally written by Wayne Geffon


This sounds like a great method and no lifting the plane with cords or balancing it between two items which is much safer! Thanks for posting this, it was a lot of typing for you. I have copied it and saved it on my hard drive to balance the 50%'er that is finally getting close to finished.

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Full size airplanes are real, our models are too.

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RE: Balancing heavys - 2/15/2009 8:35 AM   
Sawmill


 

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Joined: 1/11/2005
Last Login: 2/15/2009
From: Jackass Flats, AZ, USA
Status: offline 		I have both of these balancers offered here... http://www.ezbalancer.com/ They cover all my balancing needs now and in the future. It's a tool. You get what you pay for...and in my opinion, a great investment.

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RE: Balancing heavys - 2/15/2009 3:44 PM   
dhal22


 

Posts: 5132
Score: 138
Joined: 8/28/2006
Last Login: 5/19/2013
From: Roswell, GA, USA
Status: offline
quote:

ORIGINAL: Sawmill

I have both of these balancers offered here... http://www.ezbalancer.com/ They cover all my balancing needs now and in the future. It's a tool. You get what you pay for...and in my opinion, a great investment.



the large one is pricey indeed but very cheap compared to some of the maiden crashes we see occasionally.

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David

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RE: Balancing heavys - 2/15/2009 4:53 PM   
exeter_acres



Posts: 7455
Score: 116
Joined: 9/22/2004
Last Login: 9/24/2012
From: Johns Creek, GA, USA
Status: offline
quote:

ORIGINAL: OldScaleGuy



This sounds like a great method and no lifting the plane with cords or balancing it between two items which is much safer! Thanks for posting this, it was a lot of typing for you. I have copied it and saved it on my hard drive to balance the 50%'er that is finally getting close to finished.



Method works great... as mentioned above...same as full scale...

I cannot take credit though.. was just a copy and paste for me!

Wayne Geffon (IMAC North Central regional director) posted it a while back....

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RE: Balancing heavys - 2/22/2009 9:36 PM   
KW_Counter


 

Posts: 1414
Score: 141
Joined: 2/11/2003
Last Login: 5/19/2013
From: Lake County, CA, USA
Status: offline 		Does this technique work with tricycle gears?
Thanks,
KW_Counter


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RE: Balancing heavys - 2/23/2009 12:57 AM   
Roary m


 

Posts: 718
Score: 107
Joined: 11/26/2002
Last Login: 5/17/2013
From: lancaster, CA, USA
Status: offline 		I have used the Jim archer(Vanessa) device for years; it works very well and is very easy to set up. You just need enough room to move around the plane.

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RE: Balancing heavys - 2/23/2009 5:32 AM   
KW_Counter


 

Posts: 1414
Score: 141
Joined: 2/11/2003
Last Login: 5/19/2013
From: Lake County, CA, USA
Status: offline 		Roary,
My question is wether the technique from Exeter Acres and Wayne Geffon works on planes with tricycle landing gears.
Thanks,
KW_Counter

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RE: Balancing heavys - 2/11/2012 8:16 AM   
sebo


 

Posts: 1962
Score: 111
Joined: 8/24/2004
Last Login: 5/19/2013
From: jacksonville, FL, USA
Status: online 		Just reading through old threads and I found this on balancing........
Here's my technique.......similar to one of the above methods...

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RE: Balancing heavys - 2/11/2012 9:51 AM   
bogbeagle


 

Posts: 816
Score: 148
Joined: 4/21/2003
Last Login: 5/19/2013
From: York, UNITED KINGDOM
Status: online 		Kitchen scales and simple sums is how I do it.

With a bit of care, you can get a very accurate result.

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RE: Balancing heavys - 2/11/2012 12:23 PM   
sebo


 

Posts: 1962
Score: 111
Joined: 8/24/2004
Last Login: 5/19/2013
From: jacksonville, FL, USA
Status: online 		There sure are a lot of ways to do it, and they all achieve the same result!

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RE: Balancing heavys - 2/11/2012 1:03 PM   
Luchnia


 

Posts: 1778
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Joined: 5/17/2009
Last Login: 5/19/2013
From: Amelia, VA, USA
Status: offline
quote:

ORIGINAL: sebo

There sure are a lot of ways to do it, and they all achieve the same result!


There sure are a lot of ways to do the same thing. I made my own Vanessa rig and also regular balancers. Very easy and don't have 30 bucks total in all of them! I have been building things all my life and no way I would invest 229 in a balance rig that I can build for pocket change. I have also seen some nice ones for large gassers using PVC pipe and metal with pipe foam and rubber.

One of the best balancers is a couple of people using their hands and sound judgement. I know some old codgers that balance with hands for the last 30+ years and you could not get a machine to do better. Their planes are pristinely balanced and fly smooth as glass! Which brings up another point. Checking with some of the older guys in the area that have flown for years and years and see what they do. One may find some more unique ideas and money saving tips.

To each his own and that is another great thing about the hobby. There are so many different ways to accomplish the same thing and this gives us great concepts. I am glad there are creative minds out there!

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RE: Balancing heavys - 2/11/2012 3:40 PM   
Lone Star Charles


 

Posts: 178
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Joined: 8/29/2010
Last Login: 5/18/2013
From: Montgomery, TX, USA
Status: offline 		In response to KW_Counter:  Yes, exeter's method will work on tricycle gear as well as tail-dragger.  Just be sure that you measure with the airplane leveled.

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