Would be good if we can know the weight of the equipment taken as the aircraft in order to select appropriate materials to create an aircraft weight close to the rules that are defined and used to pick up tires properly to the size and weight of the aircraft because it is already known that a plane of the same size but different weight. The planes will be lighter than rubber line is smaller than the comparison. Tire rotation and, of course, will stay in the air longer. Therefore, those who are serious about the competition or to build an airplane flying a lightweight indoor lots, it must try to find the device scales used. But the easiest way is to purchase a used scales, which are used as a measure, and a spring scale is a number called the digital weighing scales. I have two computers together. It was the first brand of Tanita Japan country. This brand is quite well known. The price cuts are about thousand baht. Weighing up to 2000 g 0.1 g errors not exceeding 4 AAA battery use cubes for years.