Wing root fairings

This morning I finished out chapter 41 (wing attach) by installing the fuel vent lines. I opted for Aircraft Specialty vent lines, just to save some time and effort, and I also installed the JD Air fuel vents.

The standard Vans fuel vent design has a fuel line passing from the tank down through the wing fairing, where it’s chamfered at 45 degrees. I’m sure this works great, but there are a couple of downsides. The line has no screen, so there’s a risk of insects or dirt making its way into the fuel line, or even the tank, and causing an obstruction. There’s also a chance I’ll snag the vent on something and damage it. JD Air makes a streamlined vent with a built in screen, so I installed these instead. Aircraft Specialty makes a fuel line that fits the JD Air vent, so that was very convenient.

The vent itself attaches to the bottom wing root fairing using a bulk-head fluid fitting, so it simply screws into position. I was then able to loosely install the fairing, position the fuel line, final torque the fairing screws, then torque the b-nuts on the fuel line to secure it in place.

Everything went well, the only bummer is the gap at the aft end of the fuel vent, caused by the curvature of the fairing. It’s no big deal, it’s just cosmetic, and no one will see it unless they look for it specifically.

I also installed fuel placards and some grip tape on the pilot side of the wing walk area.

After a weeks off for the holidays, I was able to make some more progress this week.

I finished the wing root fairings, and installed the wing root fuel lines. These are the lines that connect the fuel tanks in the wings to the fuselage.

The wing root fairings were fairly straight forward. Getting the right shape on the bottom fairing was probably the biggest challenge.

Soon after getting the shape right I realized that I needed to countersinking the holes on the tank attach bracket. And then I noticed I had more containing to do on the wing top skin, so that the top fairing could be installed.

I brought all my countersinking, drilling, dimpling and riveting equipment to the hangar today and knocked it out. The countersinks are a little tricky because the nut plates are already installed, so a #8 countersink (the correct size) doesn’t work because the pilot interferes with the nut plate threads. I used a #21 count sink bit which seemed to be just the right size to fit into the nut plates. The countersinks are fairly deep because the fairing has #8 dimples that need to nestle down into the countersinks. The aluminum stack up is several layers deep, so there is plenty of material to support the counting depth. The only tricky part was the top, inboard countersink on the tank attach bracket. This was too close to the fuselage to get the counting cage to sit vertical, let alone the drill. I rigged up a long extension, about 18 inches long, a drilled those countersinks without a cage. It was quite easy to see the depth and I just went little by little until it was done.

There are some holes that need to be match drilled, and then 3 nutplates installed on each size. I drilled, dimpled and riveted these.

I found some proseal and used it to glue down the wing spar spacers, after giving them a little shape to conform to the wing skin.

The fuel lines were next on the list. These were pre-bent by Aircraft Specialty, and they fit exactly right. The time consuming challenge was finding a way to get them into position. The line is short and quite inflexible, and the flared ends, which are easily damaged, mate to the aluminum fittings on each side.

I loosened up the fuselage side fitting so I could flex it inboard and create enough space to insert the fuel line. I had to use a wedge to push and hold the fuselage fuel line out of the way enough to insert the new line. Once the line was in position, I torqued everything up and it all looked good.