Intro To Prop Theort

Question 1

What are the five factors that thrust is produced by?

Answer 1

Angle of attack, speed of prop, shape, area of airfoil, and density.

Question 2

What are the two theories that explain the operation of propellers?

Answer 2

Blade Momentum theory and blade element theory.

Question 3

What is blade momentum theory?

Answer 3

When a propeller blade is rotated by the engine, a pressure differential is produced between its back and face which accelerates and deflects the air. The amount of thrust is determined by the change in the momentum of air passing through the propeller, multiplied by the area of the propeller disc.

Question 4

What is blade element theory?

Answer 4

The propeller blade is made with infinite numbers of airfoil sections with each section located a specific distance from the axis of rotation of the propeller. Each blade element travels at a different speed because of its distance from the center of the hub, and to prevent the thrust from increasing along the length of the blade as its speed increases, the cross-sectional shape of the blade and its blade pitch, or blade angle, vary from a thick, high pitch angle near the low-speed shank to a thin, low pitch angle at the high-speed tip.

Question 5

Describe blade face and blade back

Answer 5

Blade face-The Flat portion of a propeller blade.
Blade Back-The curve portion of the propeller blade

Question 6

Propeller blade tracking is the process of determining?

Answer 6

The positions of the blade tips relative to each other

Question 7

How can an out of track wooden propeller be corrected?

Answer 7

Place shims between the inner flange and the propeller of the rearward tracking blade.