Inboard Edge Nutplates, Fuel Sender Fitting, Conduit Runs

Got some good work done recently, but it took longer than expected.  First, I noticed that when running through the steps that had already been completed on the QB, I didn’t notice that the inboard wing nutplates (for the wing/fuselage fairing) were missing.  Installing them requires countersinking the skin/doubler/rib combo, #40 for the nutplate attach rivets and #8 for the screws.  I hadn’t used the #8 countersink—it removes a ton of material, as you can imagine.  The rearmost nutplate goes through the skin only, so the #8 holes are dimpled on it.  I should have installed this one before installing the flap fairing, so unfortunately I had to remove the little stiffener at the inboard edge to get the nutplate in, then re-rivet the stiffener with the MK-319-BS blind rivets.

Next  up was fitting the fuel senders (the things that tell you how much fuel is in the tanks).  It’s basically a float that pivots across a potentiometer, which shows the fuel level as varying resistance between two terminals, which are wired to the engine management system (EMS).  This thing is a huge pain, because you have to adjust the wire holding the float “just right” so that the float can go from top to bottom, not hitting the vent tube and stiffeners.  There’s not much margin for error, and the only way to check is to attach it, then stick something in the drain hole to move the float to the top or bottom, then look in the hole, then detach, adjust, and repeat.  I think I did this about 10 times per side.  If you build the fuel tanks yourself (non-quickbuild), the plans tell you to install and adjust the senders before attaching the rear of the tank, which would be significantly easier.  Here’s a picture of each sender adjusted.  The wire isn’t pretty (note the differences in the 90 degree bends), but it works.

Interestingly, there is a “left” and “right” fuel sender part–they’re identical, except for the hole pattern on the mounting plate.

Lastly, we installed the conduit in the wings.  This was pretty easy: just drill a small holes near the second lightning hole in each rib, drag the conduit through, then tie it at each hole with safety wire.  We used the nylon conduit that Van’s sells.  It’s light, cheap, and easy to work with.

Kelly did the safety wire on the right wing by herself, while I started looking at the bottom skins.