In this section we mounted the front aileron control torque tube support bracket on the inside of the keel, centered in the whale tail, but down about 5/8″ (this measurement isn’t really that critical for Fixed Gear aircraft). We also mounted the Roll Trim motor through the whale tail, and the control bracket to the whale tail. However, we later decided to convert to a different system. Here’s the factory roll trim setup.

We, however, wanted to get more assured trim movement (we’d heard from several builders that the string/motor setup provided by the factory was prone to slippage), as well as indication. To do this, we selected a 1.2″ Ray Allen electric servo, which has built in indication of travel/position. This required a fair amount of modification. The whale tail had to be trimed to allow the servo to fit through, and to allow the servo arm to fully extend. We also had to create a sliding bar that would hold the trim springs while the servo moved. This way, the trim system does not move the flight controls, it merely adds or removes pressure from the control stick, acting through the springs. This bracket then had to be connected to the servo through a slot that we machined in the factory torque tube bearing support. The servo comes in two pieces, the servo and the relay deck, and to facilitate easy installation and removal, we installed each unit with DB9 computer style connectors.

Aileron Control Bracket & Bell Crank	Roll Trim Motor on Whale Tail
Aft Aileron Controls	Planning the Roll Trim Conversion
Connecting the Roll Trim System	Permanently Mounting the Whale Tail
Computer Connector Wiring (DB series)

Posted By: Brett Ferrell
Monday June 10th, 2002 at 1:52 PM

Categories: Keel
Tags: Building Fuselage Keel