BarksKT

My Feedback: (8)

There is a difference of opinion at the field on a CG issue. Some say to balance the Aircraft with the fuel tank empty, some say balance it with the tank full. The tank on most glow aircraft will be forward of the cg location making the aircraft nose heavy at takeoff and tail heavy at landing with a nearly empty tank.
Please give me some input.

da Rock

I doubt there have been any models the designer suggested be balanced with the fuel tank full. The fact you've got guys at your field saying that suggests your field isn't the best place to go for advice.

Do some searches in these forums for CG location and you'll see the subject has been covered again and again and always pretty much comes out the same. Tank empty.

You most often land after burning off fuel, and sometimes you land after burning it all. Had your plane been balanced with it all there, the landing on an empty tank would probably not have any roll out at all.

There is no winning argument for balancing with a full tank, or even a half full tank. And a winning argument for empty.

Lnewqban

BarksKT,

The empty tank approach is correct, unless your plane is a canard configuration.

The reason is that during flight the CG moves towards the tail as the fuel is used.
There is a limit for that aft position of the CG, beyong which the plane becomes very unstable.
Then, we measure the location of the CG for the worst condition (empty tank), when the CG is all the way back, but not beyond that limit.

This applies for glow, gas or any liquid fuel powered model.

In summary: any balance should be done for the tail heaviest condition, which is when the fuel tank is empty, for a conventional model of wet power.

"...making the aircraft nose heavy at takeoff and tail heavy at landing with a nearly empty tank" is not an accurate statement.
We understand as a tail heavy condition the inestable condition that any flying machine shows as soon as the location of the CG is aft the Aerodynamic Center.
During the flight, the balance of the plane should change from more to less nose heavy, but it should never reach a tail heaviness condition.

These two RCU articles explain it better:

http://www.rcuniverse.com/magazine/a...?article_id=84

http://www.rcuniverse.com/magazine/a...article_id=601

Regards

1320Fastback

Listen to these guys not those guys

99.99% of planes are balance with the tank empty. Some exceptions might be pusher prop jets or other exotic designs.

BarksKT

My Feedback: (8)

Thanks guys I appreciate your input and expertise.

invertedlowpass

My Feedback: (1)

so I should balance my electric plane with a dead battery?

1320Fastback

Only in the transmitter!

Jim Thomerson

A dead battery is lighter than a charged battery. I raised this point on a control line forum, being humorous. One of the guys at the Fermi Lab did the calculations. E=MC*2, you know. It is a microscopic, gazillionths of a nano whatever amount.

pimmnz

Thats because you've used up all the smoke in the smoke tank.
Evan, WB #12.

invertedlowpass

My Feedback: (1)

smoke tank? is that where the smoke comes from when my ESC blows up?

cfircav8r

My Feedback: (1)

Magic smoke is what makes all electronics work. The proof is when you see the smoke leak out it stops working, so it has to be true.