Fuel Tank Plumbing page 1

The fuel and sight gauge lines must be run from the tank through the root ribs (ribs #1 and 2). As stated previously, it is important that the tank be offset to the outboard side of the tank bay to give you maximum room to work in.

It starts with installing the tank fittings and some  fuel resistant lubricant/sealer.  Fuel Lube (Aircraft Spruce sells it as "EZ Turn") is lightly applied to the threads to prevent galling and to ensure proper sealing of the threads.

Warning: Do NOT use teflon tape for the fuel system connections. Little pieces could be cut off by the threads and contaminate the fuel system.

At the inboard end of the tank we have finger strainers and AN fittings as shown here:

Note that the aft AN fitting is a 45 degree elbow.  The reason for this will be shown later.

One note of caution:  When tightening the finger strainers with a wrench, install a plug or AN fitting inside the finger strainer to support it against the pressures of the wrench. Also DO NOT use the open end of a wrench, use the box end.  If you don't follow the above advise, you run the risk of collapsing the finger strainer, rendering  it unusable. Don't ask me how I know this, I don't want to talk about it. :-(

Now, with the fittings installed, you can position the fuel tank in the tank bay and tighten it all the way down with the tank straps:

Note once again, that the tank is offset to the outboard side of the tank bay to allow room for the fittings.

As previously shown, the aft AN tank fitting is a 45 degree elbow. The reason is that hole lines up with the edge of a rib lightening hole. Take a minute and look at drawing #2 in the plans and you will see that the tank is offset to the outboard side and that the aft fuel line is angled aft before finally passing through the root ribs.

Now we need to figure out exactly where to make the fuel line clearance holes in ribs #1 and #2. Here is how I did it.  Take a straightedge ruler and align it with each fuel tank fitting. Draw a line with a Sharpie marker onto the wing skin.  Here we are drawing the line for the 45 degree fitting:

The depth from the wing skin to the center of the fitting is measured and marked next to the drawn line. In this case, the fitting was 1" below the wing skin:

Repeat this for all four tank fittings. Here are the forward main fitting and the fuel sight gauge fittings marked:

Here are all of them marked:

Now, remove the fuel tank and transfer the marks on to the #2 rib, including the depth.  The holes were cut in the #2 rib using a unibit. I made 1" holes for the main fuel lines and 3/4" holes for the fuel sight gauge lines.

Next, draw straight lines from rib #2 to the root rib #1. Mark the hole locations on root rib #1 and drill those holes.  The root rib holes were drilled to the proper size for rubber grommets. For the 1/4" sight tube lines you need AN931-4-7 grommets and drill a 1/2" hole. For the 3/8" main fuel lines you need AN931-6-10 grommets and drill a 3/4" hole.

Next we will prepare our aluminum lines with flare fittings.

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