AC9S Rotatable Dipoles
This close-up of the broken Bencher Skyhawk boom shows the point of failure.... it appears there was a quarter inch gap (creating a single wall thickness) between the two reinforcing inner tubes; given the inner tubes were apparently designed to fit only one way and are secured by a horizontal bolt extending through the boom's outer and inner tubes, this quarter inch gap cannot be explained as a owner assembly problem. Email AC9S for details.