Quote:
Originally Posted by serenagh
Clarifying question on "backed by" - must all (5") of bumper plywood be touching metal structural elements? Would a 1" rim be enough? In the diagrams, it doesn't seem like there are continuous metal pieces on the frame, and the frame perimeter is also defined by an upward projection).
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There is no specified minimum. So theoretically it could be a knife edge. But it needs to be "robust" which is a judgment call. We routinely use 1" box channel for our frame perimeter. That has never been questioned.
There is also a 1/2" minimum on the corners. Once again that is linear and an area.
As others have said: It to your advantage to make sure your bumpers are roboust.