How does increasing the sling angle from horizontal affect the stress in the sling?

• A. Increases
• B. Decreases
• C. Has no effect
• D. Varies with load

Answer: (B)

When slings share a load, how much tension each sling carries depends on the sling angle. If you have two slings supporting a weight, the vertical balance requires the sum of the vertical components of the sling tensions to equal the load. If α is the angle each sling makes with the horizontal, the vertical component of each tension is T sin α, so 2 T sin α = W, giving T = W / (2 sin α). As α grows from 0 toward 90 degrees, sin α grows from 0 to 1, so the tension T decreases from very large toward W/2. In other words, increasing the sling angle from horizontal makes the sling bear less tension (stress). Keep in mind that excessively large angles can introduce other concerns like side loading, so practical angles must be chosen safely.