When balancing ones plane should the fuel tank be empty, full, or somewhere in between? If it is plane dependent, what should it be with my plane - Hangar 9 Xtra Easy? The manual does not specify. Thanks for the help.

Balance your plane with fuel tank Empty. This way when full it will be a little nose heavy and as you fly the tank empties bringing you back to the balance point. Also, if you fly the plane till it runs out of fuel it shouild glide good enough to make a safe landing on the field.
Remember:
A tail heavy plane only flies once, a nose heavy plane will fly again! RORO

Tank should be empty.

Pauly:

The only time the tank should be full for cg is when the plane is a
pusher with the tank and engine behind the cg point.

Randy

:bananahea

Thanks everyone for the replies and valuable information. I'll balance my plane once I run the plane out of fuel. Again, thank you all.

If the tank is in front of the CG, Empty. If it is after the CG then full. If it is on the CG, it really doesn't matter!

Now that you guys brought it up, I have to ask this question. If you were going to build a plane with a pusher prop configuration, would it be more favorable to put the fuel tank on the CG, and run long fuel lines to the back of the plane, or to keep the fuel lines short, and have to add dead weight to the nose to balance with the tank full? Or maybe the question is where is the best tradeoff between length of fuel line and adding weight? I wouldn't think the battery and receiver, even right near the front of the fuse, could offset a rear-mounted fuel tank. Thanks for all the help!!

ptgarcia,

Your one post ("...once I run the plane out of fuel...") seems to indicate that you are leaving fuel in your plane. To prevent engine corrosion, you should completely drain your tank and burn off any remaining fuel in the tubing and engine at the end of each flying day.

To accomplish this, hook your fuel pump up like you are going to fill the tank but run the pump backwards to extract the fuel. Once you get all the fuel out of the tank, turn on your plane and transmitter and open the throttle all the way. SECURE THE PLANE, then start the engine and continue to try and re-start the engine until it won't fire any more. Remember to SECURE THE PLANE via restraint, helper or firm grip before starting at full throttle.

Keep fuel lines as SHORT AS POSSIBLE, unless you're going to be using a pump system to supply fuel. The longer the fuel lines, the more gravity affects your fuel mixture when pulling G's. Some people, and bigger models can use hopper tanks to help with this problem it it becomes extreme on your model.

If you don't mind, I have one more question. If you then mount the engine facing backwards off the back of the plane, and use a pusher prop, what is the proper set up to deflect the exhaust? Can it pass through the prop, without causing problems? Seems it would be difficult to deflect it far enough to avoid the prop.
Thanks again!!

Most mufflers will not fit to exhaust through the prop, you can just exhaust forward, with the muffler mounted normally. It would not hurt to let the exhaust go through the prop, if you can get a muffler to fit though.

I should have been more specific. I always use wood props, and I was thinking it might not be good for the exhaust to be directed back into the flow through the prop. I guess avoiding wood would be the way to go on that setup. There really is no way for the exhaust to miss the flow through the prop, I would think.
Thanks

In a pusher propeller configuration without a pump, I would recommend that you use a main tank on or near the CG and a feeder tank at the firewall. This will allow for a smooth flow of fuel and a more stable balance point.

Geistware,
Thanks for the idea, I have read other threads that have mentioned a feeder tank, too, and didn't think of asking that. Why does the length of fuel line matter from tank to engine, but not from tank to tank? The flow from the main tank to the feeder would have to equal the flow from the feeder to the engine, right?

Thanks again!

Hello,
This is Selcuk from Turkey. I want to ask about the direction of the tank in pusher prop models. I mean that the entries of the fuel lines to the tank should be toward the engine or vice versa. If it is toward the engine and the fuel level is low then all the fuel migrates toward the engine when the plane is climbing. Is there anybody who has any experience about the direction of the fuel tank?

Regardless of where the engine is located, the tank should always face forward, with the clunk towards the rear.

uonlylivetwice,
Sorry it took me 4 months to respond. I didn't see the message. The feeder tank will give low resistance to flow due to the short run to the engine. The feeder tank will have a large, consistent draw from the main tank especially if the main tank uses muffler pressure to assist the flow. What I recommend if you cannot or no not want to use a pump (best solution), you can put a check valve between the muffler and the tank. The max pressure will be at wide open throttle. The benefit is not pressure boost as some people imply, but the pressure doesn't bleed off when you drop to idle. The mixture remains consistent and if the lines are long, doesn't lean out as quick.

I hope this helps!