Joshua
The maximum model weight for Control Line Scale competition in FAI F4B Scale is 6 KG single engine or 7 KG more than one engine. For AMA Control Line scale events the limit is 20 Lbs ready to fly less fuel. For electric power to be ready for flight the batteries must be installed therefore the battery weight is included in the 20 Lb limit.
The reasoning is that an IC engine burns the fuel in flight lightening the model but discharging the batteries does not change the weight of the model.
Note also that the Pull Test and Line Size chart does not go above 20 Lbs.
Clancy
"2.5: Models shall weigh no more than 20 pounds ready for flight, except for fuel."Clancy is exactly right. The C/L Scale rules allow a maximum ready to fly weight of 20 pounds. Key words ... "No more than" "Ready for flight"
For electric models that includes the batteries, which are as much a part of the power system as a fuel tank in an IC model. The model cannot fly without the batteries, so it is not "ready to fly" unless they are included. (how much do the electrons in the battery weigh?)
For IC, not including the fuel in the ready to fly weight is an inherited clause in the rules that dates back to the 60's, if not the 50s. It is the same in aerobatics and carrier, and any other control-line events that have a weight limit ... weight is with an empty tank.
For scale, when you get up near the upper limit in weight, the weight of the fuel is actually a pretty small percentage of the total. Plus, as Clancy said, the model is seldom flying with a full tank. Personally, when I competed I always measured my fuel. I didn't fill the tank, but put in only enough to get through the maneuvers I had planned, plus a little more. Why carry around the extra weight? Not including the fuel in the weight limit for IC power has been around for decades in control-line events and has served us well. I see no need to change it now.
Besides, why would anybody want to fly a C/L model that weighs more than 20 lbs.?? I've flown a 12 lb. airplane. It's brutal. You are concentrating so much on turning the circle and not being pulled over, that you can't do any real precision flying. I just say this, if someone sees some kind of competitive advantage in entering a 20 lb. IC model carrying another 1/2 lb. of fuel, go for it. Good luck.
Mike Gretz
AMA Scale Contest Board Chairman