# How to create a simple forces diagram using only lift and drag forces?

I would like to create a simple forces diagram (like a sketch). The lift produced by the wing depends upon to the distance from the the longitudinal axis, but, in order to make it easier, I’m taking the lift as a constant in the whole wing. Here is the question, I need to calculate the moment produced by the wing taking only the drag and lift forces by the wings, what distance should I take?

Although I think the answer will be a percentage of the wingspan, here is some data if needed.

• Wingspan: 1m
• AR: 11
• Wing configuration: tapered
• Root chord: 0.17m
• Tío chord: 0.12m

Sketch

Since I have the drag and lift forces and Cp, I need to calculate the distance from the x axis to this force application points. How can I estimate those distances?

• You may add drawing of some solutions you thought of and explain what you think about those solution, it would add clarity. For example, it would explicit which moment you are talking about (is it pitch moment, in which case your drawing will show sides of the aircraft, or is it roll moment, in which case your drawing will show either back or front of the aircraft) – Manu H May 25 at 12:20
• In order to determine the moment, you need to find the center of pressure for lift, and the center of drag for drag. These distances from the attachment to the fuselage x the force gives you your moments. These need not be perfectly exact, but close enough to provide a point for realistic overdesign, such as +/- 4G. Knowledge of $Lift$ $distribution$ is helpful here as well. Like Manu H says, start with few drawings, take a picture, and post it here for our review. – Robert DiGiovanni May 25 at 14:27
• I'm using XFLR 5 to calculate Cp and something similar to the center of drag. – VicenteC May 28 at 2:58
• You diagram is weird. for example, does the lift apply on the middle of the left wing or way below the aircraft? Why is your drag vector beginning way in front of any part of the aircraft? See for examples the diagram on this webpage to see how it compares to yours. – Manu H May 28 at 6:52