Hoerner Wing Tip-Tanks on Sonerai – Update

February 2017 - On Saturday, January 23, Steven Craig helped me to cut accesses in the auxiliary fuel tank and the front instrument panel of my Sonerai to house a new fuel quantity sender and a fuel quantity gauge. This begins the winter work to complete the Sonerai II/J3300 for spring 2017. Mercy!

Some of you may remember that I fabricated a pair of Hoerner wing tip tanks to hold about 7 gallons of fuel to restore the aircraft’s flight duration with the Jabiru 3300 engine, which burns more fuel than the 2200 engine.

The tip-tank fuel is pumped into the auxiliary/cruise tank as the pilot sees fit. Therefore it would be possible to overfill the aux fuel tank. However, with the gauge right in front of me I can see the fuel quantity displayed continuously, to start and stop transferring fuel. The gauge may be metric as the outer diameter is 2.054 inches, which is not any fraction I know of. Hand-cutting the hole resulted in the U-shaped bracket not quite engaging the edge of the instrument panel access. I had some .032 aluminum sheet, from which I was able to cut a 2 1/2-inch disc on the drill press, then on the lathe I used a parting tool to cut a 2.060-inch hole in the center of the aluminum disc. It is a close fit over the fuel gauge and tightens up nicely.

The new gauge...

...and sender

The aux fuel tank was emptied, say, three-plus years ago and has no residual fumes. A hole saw will not fit between the fuselage and the auxiliary tank, so a dremel tool was used to carve out a 1.5-inch hole to house the quantity sender. Steven fabricated an anchor 5 nut ring, which was cut in halves for installation. I found this to be better than the sheet metal (PK) screws provided with the sender kit. The sender comes with a cork gasket, but Permatex and others now sell fuel-resistant, room-temperature-vulcanized sealants that have proved to work. Thus there are choices in installations. Somewhere in there I’ll use the cork to make the sender removable. (Both sender and gauge are Bosch.)

The new $20 volt-ohm-millimeter meters have a capacitance function, so the pair was tested before installation was begun.