Monthly Archives: February 2016

After the final small priming job – main spar flanges – I’ve assembled the ribs onto the main spars, ready for riveting. I 3D printed thirty of the custom nylon clips (15 left-hand and 15 right-hand) and fitted these to the ribs. These clips have provision for a 20mm wiring conduit, two smaller holes for either air lines or coaxial cable, together with a slot through which a cable tie can be anchored. I inserted each rib in position and held it in place with the bolts and cleco’s. I’m waiting on some tooling before I drive the main spar rivets, in the meantime there are plenty of other jobs to go on with.

I did look forward in the plans and pulled some parts required for later on. One of these items, the aileron bell-cranks, showed up a problem. There is a brass bush about which the bell-crank pivots, held in place with an AN4-32A bolt. One of the bolts has a slight bend in it, which is enough to make it not go through the brass bushing. Rather than force it or otherwise work around the problem, I’m going to organize a replacement bolt, since this is a fairly important part of the control linkages.

De-burr, scarf joint, dimple right wing bottom skins. That’s it – all wing skins are done!

De-burr, scarf joint, dimple right wing top skins. 3 skin sets down, 1 to go.

De-burr, scarf joint, dimple left wing top skins. 2 skin sets down, 2 to go.

I de-burred and dimpled the first pair of wing skins in the last few days – in this case the left bottom skins. I started with a bottom skin pair in case I messed up the scarf joint. To do this joint, I decided to leave all the power tools alone and file it by hand. That was the right approach for me – giving plenty of control over what was going on. It might seem counter-intuitive to file in a direction from the outside in, but with the skin clamped down to a flat surface it works just fine. Tape up the end of the file, and around the area to be taken down, and use light, slow, deliberate strokes with the file.

I used a micrometer to check on the cut depth for each skin at the overlap point, and checked the final result by matching the skins against a scrap piece of 0.032 Alclad.

I had my second clumsy accident of the build, putting a very small ding into the skin with the end of a clamp. It didn’t look like much, but under a magnifier it looked worse, so I drilled it out #40 to take out the stress point(s) and dimpled the hole. It’s on the bottom skin after all, I’ll just fit an ‘A’ rivet to it and live with the fact that it isn’t perfect.

It took me 7.5 hours to do all this work with one pair of wing skins. There are three other pairs left to do.

Couldn’t resist riveting together a few sub-assemblies on a day I decided to not do any more wing parts priming. These are the inside ribs for the left and right wing, and the aileron hinge bracket assemblies.

A few wing sub-assemblies

I checked the fit of both the left and right outboard leading edge assemblies to their respective main spars, and match drilled the rib-to-spar holes. By doing this step now, I don’t have to do any more drilling through the main spars. I replaced some rivets and generally cleaned up the outboard assemblies. I’m waiting on some parts, and a simple vacuum pump, in order to fix the leaks in the outboard tanks. In the meantime, I’ve set them aside.

I still need to de-burr and prime the skins, but because I have such a large backlog of priming already I’m going to go ahead and prime all the wing internal components, as well as the long sections and spars. To do this I rearranged the workshop into priming mode, ready to start the de-grease/etch/rinse/prep/prime cycle tomorrow.