# How to analyze a wing spar?

1. Jan 30, 2014

### pegus

I am trying to figure out which is the most accurate way to perform the static analysis of a wing spar. Some partners told me to analyze it in cantiliver and the half of the lift force on the tip, but I do not think this is the proper way because the lift does not act on the tips. I was thinking to put the lift on the middle on the wing. This analysis is for a straight high wing.

2. Jan 30, 2014

### AlephZero

It depends what you want to use the analysis for, and whether you want the results to be "accurate" or "conservative".

A reasonable model would be to assume the lift load is uniformly distributed along the length (or even non-uniformly distributed, depending on the shape of the wing). You might also want to include the weight of the wing, and the twisting loads if the chordwise position of the center of lift is not the same as the spar position.

3. Jan 30, 2014

### pegus

This analysis is to get the safety factor of the spar and the displacement on the tips when the plane is flying. Is a rectangular wing, and the spar will be located on the aerodynamic center (approximately 1/4 of the chord from the leading edge), up to where I know this is where the lift acts.

4. Jan 30, 2014

### cjl

I would (as a first approximation at least) model it as a uniform distribution. This will give you a conservative answer, since in reality the root of the wing will be a bit more heavily loaded than the tip.

5. Jan 30, 2014

### pegus

Ok, so if my total lift force is 30lbs, and half of the wingspan is 51" (because I am analyzing half of the wing as cantilivier), the distributed lift will be (15lb/51"), right?

6. Feb 1, 2014

### Ryoko

I use a rectangular distribution for lift forces when working with spar loading. It gives conservative results and is a reasonably good approximation to wing loading.