The designer of a hydraulic box-type boom must attempt to meet the requirements of a capacity chart with load ratings that are as large as possible. To accomplish this, the boom structure must be made as light as possible.To check the validity of known calculation methods for the buckling of cantilevered plate booms, the second section of the boom was manufactured to 0.4184:1.0000 scale. This was done because the physical size of the boom section would have presented difficulty in destructive testing.The boom section was strain gaged by loading on a test stand in exactly the same way as an actual section under normal conditions. The section was tested to destruction. It was found that the failure was initiated in the bottom plate (near the lower pad) as a result of plate buckling in compression closely followed by failure of the vertical plates in buckling caused by the bending and shear force.This test verifies the use of the proposed SAE calculation method for plate booms and suggests some possible modifications to account for corner stiffeners.