🔍 Key Concepts

• Mechanical advantage and line doubling in cargo runners • How boom angle and position of the load affect block loading • Difference between thrust along the boom and load on the heel block

💭 Think About

• When you double up a cargo runner, what happens to the load in each part of the line, and what does that do to the load on the block attached to the boom? • As the boom is topped (raised to a steeper angle), does the vertical and horizontal component of the load at the heel block increase or decrease? • Is the stress on the heel block more closely related to the direct line pull of the runner, or to the axial (along-the-boom) thrust forces?

✅ Before You Answer

• Sketch the boom, the heel block, and the cargo runner, and resolve the vertical and horizontal components of the forces at the heel. • Consider whether mechanical advantage increases or decreases the load in the block itself, not just on the hook. • Verify which option confuses thrust along the boom with the reaction at the heel block — that one is likely incorrect.