Building an airplane – August 1

Jonathan and I essentially finished the wing assemblies today (sorry, no pics yet!) after finally getting a packet of more 3×16 mm rivets (actually 1/8″ x 5/8″ according to the U.S. system). Just a couple of significant loose ends in the wings:

  • We need to chase down some slightly longer 5-mm bolts (not easy to find a wide selection of metric bolts locally) to anchor the internal wire bracing, as a couple of the wires got cut a few millimeters too short.
  • We found that the first ribs on the inboard end collide with the bracing cable as shown below.  We believe that the ribs were placed exactly as specified in the plans; nevertheless, a mere 1/2″ displacement in the outboard direction would have avoided the collision.  Still pondering what to do – the ribs are firmly riveted and epoxied into place so can’t easily be moved; at the same time, we’re loathe to cut into the end bracket to create a notch for the cable to pass through. We’re waiting for advice from Chip.
  • We want to add custom hard mount points near the wingtips before covering so that we can conveniently and securely mount instruments there, if desired.  This customization would be far harder to add after the wings get covered.
  • Oh, and we haven’t actually secured the curved wingtips themselves yet – OK, there’s more left to do than I immediately remembered!

But apart from those things, the lift and tail strut assemblies, and a few other odds and ends on the fuselage that we’ll probably want help from Chip with on his next visit (TBD), we’re done with the bulk of the mechanical assembly phase.

Useful trick: if you have  half-full squeeze bottles (with tapered nozzle) of hardener and epoxy, just mix the two in one of the bottles, and then use it to squirt the epoxy mix directly onto the parts being joined. Much faster and more accurate than applying with a brush, though a brush can be used for spreading and for picking up excess. Regardless of how you do it, be sure to use 30-minute epoxy, otherwise you’ll never get done before it starts to set up!

We’re now looking ahead to covering the control surfaces and horizontal stabilizer (the rudder and vertical stab have already been covered, though not shrunk or painted yet). We’ll cover the wings last, not only because it’s the biggest and most important covering job but also because of the aforementioned customization we’re still thinking about.

For those interested, we’re using Stewart System EkoBond adhesive to attach Dacron fabric which is subsequently shrunk with heat and then coated with Latex exterior primer and gloss finish paints. You can find good videos online of how the covering process works using EkoBond, which makes the covering process almost miraculously easy compared with more traditional adhesives.

In the meantime, there’s also paperwork to fill out and file with the FAA.  We will be registering the plane as an amateur-built experimental and have requested N13UW as the registration number: ‘UW’ for the University of Wisconsin, and ’13’ because it was the first free number available with the UW suffix and also happens to be the floor I work on in my building (no, I’m not superstitious!).   I have also begun making contact with an FAA-designated inspector to sign off on the construction.

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