Q-2, Q-200 Fuel Filler Cap

This is kind of an old topic, but since some builders are still in process, I thought it would be useful to post a little bit about the fuel filler cap. In the original plans, they ask you to take a plastic 1 pint camping bottle, cut the top off and use the threads and cap for a fuel filler cap. This is proved to be a very bad idea because if the threads should crack, as they will, you are now introducing low pressure air to your fuel system and you're not able to deliver enough fuel to the carburetor. Unfortunately, the pilot only finds this out when he's about two or three hundred feet off the ground, a hair raising experience.

Several people have come up with different ways to make a fuel cap assembly, but I have been using this very simple one for over 20 years and it is working just great and it is dirt cheap. Run down to your hardware store and get a 1-1/2 by 1-1/2 PVC threaded x slip fitting. Then go to the section of the store that has that little plastic nut that you use under your bathroom sink for the drain slip fitting. Finally, take a piece of .030" aluminum and make a little disc that fits into the slip fitting nut. Now you have all the pieces you need to make a fuel filler cap. I think the pictures should speak for themselves more than me cluttering up the airways with a bunch of verbiage.

A short length of PVC is used to connect the fuel filler to the main fuel tank.

Here in the same installation on my auxiliary fuel tank.