Fuel Tank Test, Wing Conduit and Bottom Skins

Fuel Tank Test

One fairly critical component of the QB inspection includes testing of the fuel tank for any leaks.  These tanks are notoriously challenging to build and get sealed up, luckily Vans does this for you on the quickbuild but highly suggests you test them yourself.  To accommodate this Vans sends you a testing kit with your shipment.  Since I removed the tanks from the wings to inspect it makes it fairly painless to run the suggested tests.  I did have to reach out to the VAF forum with a few questions about the process.  There are several methods you can use to test the tanks but I decided to go with the one the kit is for.  One issue that wasn't clear to me was the kit requires you to have the tank fuel filter installed to use one of the caps. Once that was figured out the rest went smoothly.

Tester Kit Parts

The picture above shows the parts of the testing kit; fill stem you screw on, cap for the fuel filter and a balloon cable tied to the tank vent line.  Now the purpose of the balloon is to ensure you don't over pressurize the tank, so if it pops then that's too much pressure... if it doesn't fill then you have a big leak somewhere.  I used an air compressor turned down to the lowest PSI setting to fill, would fill for about 5 seconds and wait and repeat until the balloon was inflated.  Then it's like testing a tire, you just spray soapy water all over the place and look for bubbles.   The only bubbles I had were around the balloon since the cable tie wasn't air tight. Happy to saw that both tanks passed their tests and are ready to be reinstalled onto the wings.

Wing Conduit

The subject of conduit for both the wings and the fuselage is something that I really struggled with.  Searching the internet you find that everyone does it a bit different and some don't do it at all.  For me this plane I plan on having for a very long time and would anticipate a number of avionic upgrades so conduit is a must.  Right sizing of the conduit is also a must, you don't want to end up with too little, and you really don't want to end up with a mess of conduit to have to work around.

What I ended up doing is running 1/2 CPVC down the wings in the factory drill holes, it's an extremely tight fit, it's light weight and large enough to accommodate all my wiring needs.  I went ahead and put a break in the conduit where the bell cranks go which allows me to run wires from that area down the conduit as well.

1/2" CPVP Conduit, SB-375-4 bushing for AoA and Pitot lines

Something else that needs to be resolved before closing up the wings is your Pitot situation.  I plan to use a heated Pitot/AOA combo meaning I need to install a mounting bracket for that.  I went with the Gretz Aero kit because it's compatible with multiple vendors so if I decided to stray away from Garmin I'll be able to use a Dynon or some other vendor.  The instructions seems a bit confusing but if you look at the pictures you get an idea of what you need to do and it only took about two hours to go through and get it all mounted.  That includes making the bracket, etching and priming.

The Pitot/AOA combo also requires running two separate air lines.  I decided to use the standard run already drilled on the kit and then make an additional hole to run the second line.  Now I would be lying if I said this was easy because the inboard holes on rib three and four which is covered with a skin was a tad challenging.  I ended up using an additional drill head and connected that within the cavity I was drilling... okay that probably doesn't make sense, a better method would be to get a foot long 3/8 inch drill bit.

The final step before I could close the skins was to mount the autopilot roll servo bracket and the Aileron trim. Will have to connect them all later but for the time being all done.

Bottom Skin

This section is all old hat to me.  Although very time intensive, it's not overly challenging from a process perspective but requires quite a bit of ninja skills if you're going to solo rivet.  The gap fairings went on well with the only hangup getting the last four rivets on the flap fairing.  I had help but it was to no avail with trying to get a bar at the very top... In the end I used pop rivets for the four rivets.  Standard builders would have no issues since the inboard bottom skin wouldn't have been attached yet.

Those are the four pop rivets

My cousin who flies C17's down in Altus was up and helped me get started on the actual skins and jstiffners.  We rocked through all the match drilling in about 3 hours.  I saved him from the agony of the deburring and dimpling, he would like to build a plane at some point and those two processes might have quickly changed his mind.

Here's the Gretz Pitot mast after match cutting a hole in the skin.

It was a tad confusing on the actual riveting process.  After reading the plans a good 10 times and looking for pictures online I figure out that you started in the middle, worked your way to the sides at the top and then down... ignoring the three outboard bays.  That's because to get to those you roll the skin back and hit those when you can.  I would suggest having help, but then again I was able to do it solo with only a few minor cuts and bruises.  I'm very happy with how my rivets turned out, only about two dings per side.

All buttoned up