Flop tube installation

02 Jul 2004 Flop tube installation

Normally you only need a flop tube when you plan to fly upside down for extended (more than about 30 seconds) period of time. I probably won’t be doing this anytime soon, since I’m not yet aerobatic qualified, and the engine I have chosen does not yet have an inverted fuel system. However, just to be on the safe side, I’ve decided to install a flop tube in the right fuel tank.

I chose the right tank totally by chance – it’s the wing that was closest when I grabbed one to start work.

What I did today was to install the “trap door” and one of the “anti-hangup” guides.

Here is the trap door, and the plans. The plans are for the left tank, and I’m doing it on the right tank, so there is some reversal of the images. Notice the plans also show the anti-hangup guides.

Squeezing the pop rivet puller into the tank. Not much room here for the rivet on the right, so I had to fabricate a special device to extend the reach of the puller. You can see where I squeezed the hinge to make sure the pin does not slide out. Not too elegant, but I think it will stay in there.

A couple of shots of the anti-hangup guide. The plans seem to call for a strip of aluminium, but I found using a bit of angle would be easier. I had to put a nutplate on one end since I could not get the pop rivet puller in the right angle to install a pop rivet there. I’ll use a 6-32 Torx screw.

Here are a couple of shots of the door in, and the guide. Turned out ok. I did the best I could deburring, and vacuumed out the chips, but I will do some serious flushing before I finalize the installation of the tanks. These were QB tanks, of course. I found an unused rivet in there when I first opened the tank. No telling what else is in there.