Chuck and Ryan's Build Tips

[ceslaw]

Tight Fits

1. Torque Tube. The torque tube was too snug to fit the torque tube masts. After reading posts about the tube getting stuck before it could be properly placed, I approached this step forewarned. Measurements of the tube revealed it was in the range of 1.501 – 1.502 while the mast opening was just barely 1.500. 220 grit sandpaper was used to sand the ends of the torque tube so it was just barely under 1.500. It took a fair bit of sanding to reach a point where it would just slide in.

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We sanded a couple of inches from the end of the tube so that the torque tube blocks would also fit properly, but shimming later proved necessary. That will be a topic for another day.

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2. Fuel Selector. The fuel selector has three fittings. Two are straight but on the bottom an angled AN9142D is used which must be pointed in a forward direction. The fitting supplied with the kit would not reach a snug point when pointed forward.

To solve the problem a couple of extra AN9142D fittings were ordered from Aircraft Spruce. It seems that there is some variation in the way the threads are cut so different fittings may end up in different positions when tightened. By swapping fittings one that snugged up in the correct position was found. (I now have some extra fittings I will gladly part with). The following images illustrate the different points where three fittings just began to snug up. The first came from Aircraft Spruce while number 2 and 3 came from Cubcrafters.

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The manual refers to using E Z Turn fuel lubricant on the threads. I used that stuff on the first plan and over time noticed that the lubricant tended to turn blue at the joints, suggesting there was some seepage. On this plane Loctite 567 was used which is a methacrylate sealant; a preferred solution.

Fitting number 1 worked perfectly. Twisting it back and forth helped massage the threads a bit, then the Lotcite 567 was applied, and it was turned a bit less than 180 degrees after it started to snug to its final forward facing position, where it was nice and secure.

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