sportpilot-RCU

My Feedback: (1)

I am interested in knowing why a low wing plane is balanced inverted. I am looking for the proper term.
Recently three of us were balancing a Ryan st in a freinds garage. We knew the plane had to be balanced inverted and this turned into a discussion on why low wings are balanced inverted. After very got it balanced, we checked the balance right side up and it didn't balance the same.

KCFlyBoy

My Feedback: (12)

It is just easier to balance a low wing plane on its top. The weight of the fuse and vertical stab have a pendulum affect which is minimized when it is on its top.

MinnFlyer

My Feedback: (4)

Ditto to the above. When a low-wing plane is right-side-up, it is "topheavy". The top wants to swing around to the bottom. So putting it inverted just starts it where it wants to be anyway.

sportpilot-RCU

My Feedback: (1)

Well the way I looked at this was the weight hanging on the wing, and should be balanced at this point. We realy wanted to hear or read other peoples expressions on the subject. You can ask ten people this question, and get thats what the manual says to do.
Sportpilot

KCFlyBoy

My Feedback: (12)

If you can get it to balance more power to you. I don't like to work that hard. Just my $.02 CB

sportpilot-RCU

My Feedback: (1)

We did get it balanced, using a great planes balancer, and it flyies nice, have to be careful with nose over on the ground though. Using robart struts, we have to push them more forward.
Spotpilot

Giant Scale

I recently had to balance my 35% Giles. Since I usually work alone, the thought of turning the plane upside down and trying to get it on a balancer was not a pleasant thought. I am using a set of super long legs by kollerkraft. It is much easier for me to balance the plane upright than inverted. I posed the same question to Dennis at kollercraft and he told me that some low wing planes have to be balanced inverted because the planes landing gear will hit the balancer. If yours clears the balancer then you can do it upright. I balanced mine upright and it worked fine. I don't understand why it would matter if the plane is upside down or rightside up when you balance it, the CG is in the same place.

sportpilot-RCU

My Feedback: (1)

Well, it did make a difference. Upside down we took off a 1/2 ounce of weight off of the tail. And yes the wheels would have hit the balancer. We did it upright with our fingers, then upside down with the balancer, and it became tail heavy. We left it balanced that way and it flys great
This is turning out to be the same thoughts we had in the garage. There has to be a definate answer here some were
Sportpilot

Woodpile

SportPilot,

Giant Scale is right, the CG is the CG, no matter what and it won't move unless you change something in the plane.

The reason the CG seemed to change is, when the plane is inverted the CG is below the supports. Right side up, it is above. With the CG below the support, you have a greater band in which to find a balance point but it is not as accurate because the plane wants to hang there. With the plane right side up, the band is much narrower, making it harder to find the exact point, but it would be far more accurate. The problem is, any little deviation, such as not being in the same plane (as in geometry, I mean) will throw you off.

Think of it like balancing a broomstick on your hand versus hanging it straight down. When the CG is below your hand, it is tough to get it off center, but when it is above, it can be tough to keep it there...

Ed