How do you determine that the control surface is balanced? Should
the surface stay where you left it, or should it move from where ever you put
it to a level position?
Bill B
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of rwolf99@aol.com
Sent: Wednesday, April 22, 2009
9:27 AM
To: lml@lancaironline.net
Subject: [LML] Re: Balancing MkII
Elevators
I, too, was surprised at how much lead I needed to balance my 360
ailerons. In fact, I have those lead half-rounds going nearly full-span
(two of them, flat surface to flat surface). But let's stop to think
about it. We need as much "moment" (mass x distance) in
front of the hinge line as behind it. In practice, we have more weight
(balance weight) forward of the hinge line than we do behind it (the control
surface itself) since the CG of the control surface is generally much further
behind the hinge line than the balance weights are forward of it. This is
certainly the case with the ailerons, but less so for the rudder and elevators,
since they have those forward overhangs for aerodynamic balance.
For preliminary design purposes, my airplane design group assumes that the
balance weights weigh 1.5 times the weight of the control surface alone.
Bottom line -- your balance weights need to be at least as heavy as the control
surface, and up to 50% more.
Yup, it's a lot.
- Rob Wolf