Building, testing and operating an experimental aircraft

Fuel Vent Tube Installation

28 Aug 2011

When we started the process of installing the vent tube we were unable to find detailed suggestions on how to proceed. There are probably many good ways to do this, but the following is what we came up with. We are not suggesting this is the best way to do it, but it worked for us.

Fuel Tank Vent Tube Fuel Tank Vent Tube

The tubing comes from Van’s in a coil. Unroll about 52 inches. The vent tube needs to be straight to pass through the snap bushing you will install in the ribs. In a workshop at Oshkosh we asked about the best way to straighten the coiled tubing. We were told to just “work it with your hands”. This will get the tubing somewhat straight. If you want to get it straighter the best way we found was to roll it between two flat surfaces, such as on your workbench with a 2x4 about the same length as the tube. This will get it straight enough to stick right through the snap bushings.

Flare, Sleeve and Nut Flare, Sleeve and Nut

Once the tube is straight, slip on a sleeve and nut and flare one end. Then install the snap bushings in the ribs. With both the inboard and outboard ribs removed, push the tube through the ribs with the flared end on the inboard side. Install the vent tube fittings on the inboard rib and cleco the rib in place. Now pull the vent tube back toward the fitting until the flare is even with the end of the fitting. Mark the vent tube where it exits the snap bushing on the second rib and where it appears it should be bent to come in line with the fitting. Measure the distance from the end of the tube to the fitting to see how much it should be bent to meet the fitting.

Measuring for the Bend Measuring for the Bend

Now remove the inboard rib and pull the tube out far enough to use your tube bender. Make two bends the distance apart required to bring the tube in line with the fitting. Note your mark on the tube where it exits the second rib and be sure to make your bends far enough away so that the tube can be reinserted in the rib snap bushing.

Bending Tubing Bending Tubing

When the bends are made, push the tube back in and reinstall the inboard rib. Bring the flare up to the fitting and check how you did. You may need to re-bend the tube a little or work it with your hands, but if you measured and bent accurately, you should be pretty close. Once the tube meets the fitting, hand tighten the nut.

Bend Complete Bend Complete

Now go to the outboard end. The tube will be sticking out past the outboard rib location and probably will be close to, but not in, the clip you installed on the fuel cap flange. Mark the tube where it will exit the clip when it is clipped in and where it needs to be cut so that the outboard rib can be installed. Unscrew the fitting on the inboard rib and push the tube as far as possible outboard. You should have just enough space between your two marks to get your bender on.

Bending Bending

Bend the tube slightly upward so that the end mark is above the high fuel line and then bend it level again, as shown on the plans. You may have to rotate the tube to get the bender on. If so, mark the “to be installed” position on the tube so you can orient the bends correctly and return the tube to it original location.

Bent and Trimmed Bent and Trimmed

Once you are satisfied with your bends, push the tube back in and reattach the inboard fitting to the tube. Finally, work the tube into the clip and cut it off as shown in the plans. Install the outboard rib to check the fit.

comments powered by Disqus