Here is another situation where we’ve decided to stray from the manual. The factory system is a candy-cane shaped fiberglass spring system, with a linear actuator pushing against it to provide pressure relieve to control stick’s pitch inputs. This spring is reported to be of mixed effectiveness, and of sketchy reliability, so we’ve elected to go with¬†Alex Strong’s pitch trim system¬†instead. This system attaches to the bottom of the control stick instead of up on the canard, which opens up space behind the radio stack. In our case, this mounting slight impinged on the housing we’d built for our fuel shut-off in the keel, but we sanded the foam out of the exterior on top and reinforced this portion of the box, alleviating the interference. The strong system consists of a drive motor that acts through a lead screw, which acts through a pair of springs on either side of the control stick in an ‘override’ assembly.

To install this system, first we had to drill a matching hole in the Strong control stick insert the same diameter as the Velocity aileron attach bolt. Since this is slightly undersized, I wrapped the attach lever with masking tape until it was a snug fit in the control stick, then the stick and Strong system were leveled on the drill press and match drilled. Then the stick was re-installed into the keel, and the strong system was leveled (with the plane leveled) and a mounting hole was drilled into the keel 14 1/2″ aft of the neutral control stick position. Also, I had to modify the Infinity stick grip, to have the wires exit through a grommetted hole on the front of the stick rather than through the bottom.

In out final checkouts, we found that we could not quite get full aileron travel due to the Strong pitch trim system bottoming out on the sides of the keel, so we relieved the sides and made covers. It turns out the trim spring body doesn’t actually protrude, but it need the thickness of the keel.

Later on we had to go back to the factory trim system to get enough trim to land comfortably.

 

Posted By: Brett Ferrell
Friday November 12th, 2004 at 8:03 PM

Categories: Controls
Tags: Building Controls Elevator Fuselage Trim

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