The plane I'm building has the engine mounted at 90 degrees. Do I also rotate the fuel tank 90 degrees or does it matter? The construction manual just say's to install the tank parallel with the thrust line and in alignment with the carburator. I don't quite understand this fully.

Thanks,
Pete Killingsworth
Peshtigo, Wisconsin

Engines do not really have an up or down side. There is no real right-way-up. The right way up is the way that fit's mosrt conveniently on your plane.

TThe only real recommendation is that the center of the fuel tank should line up as close as possible with the carb of the engine. Even this though is not really necessary any more. There is one concern with the pressure line from the muffler of the engine. If this is installed below the fuel line in the tank, then there is the possibility of syphoning when the engine is not running.

Bottom line: install the engine as is most convenient. Install the tank in-line with the carb, and make sure that the pressure line from the muffler is as high up as possible on the tank. It is often convenient with the pressure line to install it in such a way that turning the plane upside-down allows you to pump out all the fuel when the day's flying is over.

gus

Don't worry about the engine being mounted at 90 degrees. Install the tank upright. and at the same level as the carb. Try and get the tank as close to the engine as possible. This will help fuel flow. As an extra precaution add a fuel filter to keep little bits out of your engine in the line from the tank.

I have a pattern plane with the engine inverted the tank 2 inches higher and 9 inches behind the engine above the wing saddle. Needless to say this does not work without a cline regualtor/pump. Perry also makes something that works for tanks in wierd places. Chances are you wont need either.

Best of luck

As has been mentioned, the only thing that is important is the vertical relationship of the tank to the carburetor. Other than that, you can rotate the tank and the engine independently of each other to suit the application. For example, Sullivan tanks have a bubble on top, but often I have to install these tanks sideways because the tanks are wider than they are tall and sometimes the fuselage is too narrow.

Of course if you do rotate the tank, you have to rotate the vent tube so that it points up (inside the tank) or you won't be able to fill the tank all the way.

Thanks guys, now I know just what to do. Excellent sugesstions.

Many thanks,
Pete