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Elevator trim

The standard Sonex elevator trim is what we are implementing, despite all the little tweaks from the standard design, at some point you have to just stop modifying and just build the plane.

OK, a few changes but really just minor. The “swivel” at the control arm end is called out as a standard part from Asuza. It’s fine but we had modified the Bowden cable mounts on the engine and the experience with that design provided an easy modification to an AN bolt that has a more positive clamp on the cable.

We’ll have to add some detail on the design, should it be worthy of being copied.

Below are a couple photos of the design and implementation.

This is the trim tab from the bottom with added reinforcement and showing the swivel constructed from an AN3 bolt. Why not just use the “Z” bend on the bowden center cable? Mike Smith changed his out and the assumption is that the bend could be problematic. Not sure if the change is justified.

The control handle is basically the same as what is shown on the Sonex plans. It works well as is. The only change is the swivel.

Control handle with only minor changes from plans. The swivel is a modified AN3 bolt
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Control Rod UHMW Guide Blocks

The UHMW guide blocks for the elevator control rod will squeak at the two extremes of the motion. The hole in the blocks are a straight bore. The control rod moves up and down slightly with the mounting pivot arm. Dan’s solution is to bevelthe bore slightly to allow the change in height of the control rod. The rod is still supported and no squeaking due to interference.

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Welding Control Rods Bolt End Style

Dan has some experience with ox-acetylene welding.  He purchased a new small tip.  We had purchased a bunch of left over drops of 4130 tubing from Wicks to practice on.  I cannot find this item on their website right now.  Dan tells me that the thicker tubing is easier to weld.  The thin wall sizes are tricky since you can melt a hole in the tube if not paying attention.

One end of some of the control rods have a Grade 8 bolt welded into the tube.  The tube is cut so tabs can rest on the hex head faces.