Sonex 1404

Posts Tagged ‘square

The wing box has to be perfectly level at the root and tip. Also, the aft spar attach point has to be exactly 19″ from a reference point on the main spar to ensure the whole structure is square. I bought two long spirit levels and a right angle from Home Depot to set up the structure for skinning.

IMG_0314 IMG_0315 IMG_0317

I used several wood pieces to keep the assembly level and square.

IMG_0319 IMG_0321

Once everything was square, I clecoed the pre-drilled top aft skin to the rear spar and worked towards the main spar.

IMG_0324 IMG_0330 IMG_0331 IMG_0365

The wing then went back on to the saw horses so I could flip it upside down to attach the bottom aft skin.


I had an EAA Tech Counselor come visit to see my project at this time. Bob Steffen is a serial offender and has built several RVs. He complimented me on my workmanship and gave me several suggestions, chief of which was that I should put wiring into the wing if I planned to install lights in the future. I had planned on Sonex 1404 being a day VFR only airplane, but following his advice, I decided to install wiring and the position lights right now. I went ahead and ordered the AveoFlash Powerburst lights that Sonex recommends, and also the wingtips with the integrated mounts for those lights. I also ordered tubing, snap bushings and wires to run through the wings.

Bob Steffen


I flipped the wing over on my workbench and squared it up again. As with the top aft skin, the bottom aft skin was drilled from back to front.

IMG_0374 IMG_0378 IMG_0380

The structure went back on the saw horses so I could drill through the spar caps. It is impossible to do that while the wing is on the bench – I am not tall enough! Also, I updrilled half the holes to 1/8″ so I could replenish my stock of silver clecoes.


I got the wing tip lights from Wicks at this time. These are integrated nav, position and strobe lights and are very compact. They also don’t need a light on the tail since both of them have white lights at the rear and these are visible from the back of the airplane with the proper mounts. I enlarged the machining holes on the nose ribs and inserted snap bushings.

IMG_0385 IMG_0387

After drilling the holes through the spar caps, I put the wing back on the bench and draped the leading edge skin and clecoed it to the main spar. Unfortunately, the skin bent in the middle while carrying it resulting in a small crease across the leading edge. The pictures don’t show it too well, but it looks worse in person.

IMG_0390 IMG_0391

I ordered another skin from Sonex, but proceeded to drill and cleco the leading edge skin with the idea that I would just swap the new skin for the old one. I first inserted the tubing into the rib holes. This will carry the wires for the lights.

IMG_0402 IMG_0404

Another view of the crease right in the middle of the picture.


My wife helped with the clecoing while I drilled – makes everything so much faster than doing it alone.

IMG_0408 IMG_0409

I turned around the wing and used some ratchet straps to get the holes to line up with the main spar. More drilling and clecoing followed until it was done. I noticed that the crease in the middle didn’t look so bad anymore, probably because the skin is now stretched a little. I decided to cancel the order for a new skin. I’ll see what I can do to remove what’s left of the crease. The options I have are

1. Cut it out and put the landing light in there – I don’t like this option because I want the landing light on the left wing – not the right

2. Leave it as it is

3. Paint the wings and smooth out the crease in that process

I like 2 or 3, but haven’t made up my mind yet.

IMG_0413 IMG_0414 IMG_0415 IMG_0417


I also finished up the “unfinished business” on the ailerons – the two holes that I thought I couldn’t reach. With a combination of force and finesse, and also some luck, I riveted the holes in both the ailerons. The Tech Counselor had said I could go ahead and put a rivet in the middle of those two and ignore the holes, but I am glad I could get this done per plan.

IMG_0375 IMG_0376

As it turned out, one of the lights wasn’t working properly. The strobe and position lights don’t work together on the right side light. I sent back the unit to AveoUSA and am waiting for a warranty replacement.