怎样削螺旋桨(航模制作)（How to cut propellers）.doc

怎样削螺旋桨(航模制作)（How to cut propellers） How to cut an airplane propeller First, some basic concepts of propeller When we look at the propeller as a rotating wing, we can understand the basic working principle of propeller with the help of known aerodynamics. 1. pitch, power pitch and geometry pitch Pitch: in a broad sense, it can be understood as the straight distance that the propeller rotates in the direction of the propeller axis a week. Traditionally, the pitch value at the 70% radius of the propeller is called the value of the call. It has the significance of marking. Dynamic pitch (Hg): the pitch of the blade rotates one week, as seen by model aircraft (see Figure 1). When designing a propeller, the dynamic pitch value must be determined first. Geometric pitch: (H): when the chord line angle of attack is zero, the propeller rotates a week (also shown in Figure 1). It represents the actual size of the blade angle and is the actual parameter of visible and tangible. Generally speaking, the geometric pitch of the model drawing is the main basis for the propeller elimination. The relationship between 2. power pitch and geometric pitch Since the propeller operates near the favorable angle of attack and the angle difference between the zero and the zero angle of attack, the dynamic pitch is less than the geometric pitch. The relationship between geometric pitch and dynamic pitch is geometric pitch (H) = 1.1 to 1.3 times dynamic pitch (Hg). That is to say, when designing a model aircraft, the geometric pitch of the propeller can be estimated by the above formula when the dynamic propeller pitch is determined. 3. commonly used propellers are equal pitch paddles with equal geometric pitch values. The advantage is that it is easy to design and manufacture, but the disadvantage is that the work efficiency is inferior to the unequal pitch propeller. Because the geometric pitch and pitch angles of the unequal pitch segments are different, even though the efficiency is high, th