What you do is buy a small (2oz) fuel tank, fit two straight brass tubes (not forgetting to replace the bung) one tube at the top just inside the tank, the other goes to the very bottom without touching.
You mount the tank vertical and connect the vent pipe from the main tank to the brass tube that goes to the bottom of the tank, and the other to the vent pipe outside the aeroplane.
When you fill the main tank the overflow goes into the vent tank and not on the ground, any fuel in this tank will be sucked back in when the turbine is running.
If you carry the model when it is full of fuel sometimes it will leak out the vent pipe, normally all over your trousers ! with the vent tank it cant get out unless it fills the tank first.
Other use for the vent tank is that it can be used as taxi tank, you can let the main tank overfill so the vent tank will be used up first on startup and taxi, so you always have a full tank on takeoff.
Pic below is the one fitted in my Boomerang Intro, with a metal pipe outside for the vent.[/quote]
