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Re: Elevator Trim Tab

At 04:14  98-06-30 -0500, you wrote:
>Could some of you aero types tell me if this is a bad idea?
>Please see:
>I'm thinking about cutting out a small notch at the trailing
>edge of the elevator.  In this notch will be epoxied an elevator
>hinge.  The trailing edge of the hinge will have sort of a bellcrank
>that is attached via a lightweight rod to a servo that is also
>embedded in the elevator.
>I know I'll have to rebalance the elevators to make this work.
>What sort of flutter problems would one have if the linkage
>connecting had some lash?
>Brian Michalk  <http://www.awpi.com/michalk>
>Life is what you make of it ... never wish you had done something.
>Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
>musician, home-brewer, entrepenuer and SINGLE!

The most of cerified aircraft seems to use aerodynamic trim as the one you
want to build.
The trim mechanisms used in the Velocity only reduce the stick force.
It does not alleviate the hinge moment, that is, the loads on the elevator
torque tube do not change when you trim.
The aerodynamic trim will reduce the hinge moment besides the stick force.
You wouldn't need the heavy trim motor for the aerodynamic trim. The small
and light MAC servor motor would be enough.

The most problems would be the weight balance and the flutter as you worries.

You can embed the trim motor in the canard instead of elevator if you don't
like the weight increase of the elevator.
In this case the torque tube could be a obstacle.

Eung Tai Kim
Aircraft Division  
Korea Aerospace Research Institute
Yoo-Sung P.O.Box 113
Taejon, 305-600, South Korea
Phone) 82-42-860-2345                  Fax) 82-42-860-2006