airbusdrvr

Bax,
I was considering using an OS FT-120 Gemini II in a kit build. However, the tank location instructions for the engine state:

"The ideal tank location is with the top of the tank 1/4-3/8" above the needle valve. However model design will usually require the tank to be located higher than this and there should be no trouble with such a tank location provided that you do not pursue spectacular aerobatic flight."

My flying has never been described as "spectacular aerobatic flight." So I should be OK on that requirement. However, it appears that were I to use the motor in this plane, the tank would be very high.

My question is this. In the picture below I have positioned the motor on the plans and drawn the desired vs the lowest possible tank location. It appears the motor would not be acceptable on this plane. What is your advice?

Bax

My Feedback: (11)

Well, we normally would want the fuel tank set up so that the centerline of the tank would be level with the needle valve or about 3/8" lower, at max.  We'd consider your "ideal" location a bit too low.

As long as you don't get too much mixture change as the fuel is drawn from the tank, and as long as you don't get much fuel siphoning from the tank when on the ground, the tank on the bottom of the compartment should be OK.  To prevent siphoning, just have the fuel tubing make a loop above the top of the tank, and then reverse-prop the engine after shutdown.  If the fuel line's empty, it won't siphon, then.

airbusdrvr

I see you said "centerline" and the manual says "top" of the tank when referring to the 1/4 to 3/8" below carb. I guess I will just have to set up a test stand to duplicate the install and see what happens.