you dont need a timer and never will....if you know your engine.
your engine will give you warnings that its running out of fuel
it will rev higher all of a sudden without throttle input, aka lean out due to the fact the engine is now sucking air and fuel. when this happens you usually have around 1 min of fuel
it wont spudder like most would think, if it does sputter, its to late and your out of fuel.
the best way to learn the engine is put a small amount of fuel in the engine and start her up, then listen as it starts to run out of fuel. its more noticible in the air due to the fact your throwing the plane all over the place. or just put her in the air and guess when she will be out of fuel, when you hear a throttle spike land and you should be fine
that being said
you should be able to land 90% of planes deadstick without any damage, some of them really need the power or they drop like a rock
The point here, jimmyjames, is to teach proper methods of flying RC. Trying to learn to understand engine sputter as the tank runs dry, is defininely not the way to go. What happens if you are in a turn, way downwind, and run out of fuel? Are you going to land it in the trees or bushes, or in someone's back yard? It's hard enough when it happens by accident, but to intentionally allow this to happen is not the worst technique I've ever heard of, but it is right there with them.
The best way, by far, is to time the flight and to get it on the ground safely before it runs out of fuel. Having an ounce or so of fuel left in the tank is not a sin, it is just plane good flying practice.
CGr.