TinnerFlow™3rd YearYELLOW · Check FirstWide Rectangular 45 Reinforcement
Wide, shallow angled fittings need enough stiffness to hold shape. If the panel oil-cans, stop and add approved reinforcement or get the fitting remade heavier.
A wide flat panel on a 45° fitting takes a lot of air impact and mechanical stress. If the throat or heel plate is too flat and unsupported, it can buckle, boom, or oil-can under airflow.
Recovery is usually approved external stiffeners, internal tie support, heavier-gauge replacement, or a revised fitting detail. The fix must preserve the duct shape without creating an internal obstruction.
Do not ignore oil-canning on a wide angled fitting and bury it above a finished ceiling.
Panel buckling can create noise, fatigue cracks, air leaks, and airflow problems.
Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.