Propeller naming convention

     One way manufacturers specify their props is to use a standard naming convention. You might see a prop listed as a 7x4 for example. 

     The first number is the diameter of the propeller (commonly in inches or milimeters) and the second number relates to the pitch of the blade also measured in a unit of length. This may seem a bit unusual to have an angle defined as a length but what this means is how far forward the propeller will go in one full revolution. To picture this imagine the propeller is immersed in something like jello, as the propeller turns it cuts through the jello and screws itself forward. The distance it travels is related to the angle of the blade thus a distance is given for the pitch. A higher pitch blade has a steeper angle and vice versa. 

     The blade tip moves faster than the root so to avoid creating larger loads on the blade, the tips are of less of an angle. If your highest load is at the tip then it acts as a lever and creates an amplified stress at the root. To get more thrust with less pitch just increase the blade length which also decreases the torque on the motor.