lml@lancaironline.net Mailing List Archive

Consider the vertical position of the CG of the surface relative to the point from which it is being supported during balancing. Assume a surface that is perfectly symmetric in the z direction. If you remove a hinge pin (1/4" bolt on the elevator, for example) and hang the the surface by wire run through the hinge hole, the CG is below the support point and a balanced surface will tend to return to level. If the same surface was balanced by setting it down on hinge pins (360 rudder, for example), the CG would now be above the support point and the surface will be difficult to keep level. If truly balanced on the hinge center line, it will stay in any position.

In reality the vertical CG position is not always known. If the surface will not stay in position, look at which direction it wants to fall when released from a level position. If the surface does attain a stable position it is easy to see which end is heavier.

Chris Zavatson

N91CZ

360std

www.N91CZ.net

From: Jim Nordin <panelmaker@earthlink.net>
To: lml@lancaironline.net
Sent: Tuesday, February 21, 2012 8:30 AM
Subject: [LML] 360 rudder balance

Hummmm … correct me if I’m wrong.

Balance of control surfaces is attained when the component (aileron or elevator for example) hung at the center of rotation and given a perturbation (trailing edge pushed down) minimally returns to the level condition or better a small nose down condition. Any other condition (leading edge high above level, trailing edge below level) warrants adding weight to make the nose (leading edge) to settle below level.

Nose heavy is the point here. Any other condition may result in flutter.

Jim

From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Charles Brown
Sent: Tuesday, February 21, 2012 8:02 AM
To: lml@lancaironline.net
Subject: [LML] Re: 360 rudder balance

They should stay in any position where you let them go. They should not return to level. If they are out of balance, they will have some preferred orientation (as you say, will move up or down).

Charley Brown

MS Aero/Astro Engineering

On Feb 20, 2012, at 6:51 AM, Bill Bradburry wrote:

I have a question about balancing the flight surfaces. If they are in balance, should they return to level from where ever you move them to, or should they just stay where you put them.

I assume that if they are out of balance they will either move up or down from level depending on whether you need to add or remove weight.

Bill B