Hydraulic Dump Trailer Blueprints (12' x 6'4" - Model 12HD) Box Size: 12'x6'4" w/3 sides Bed Capacity: 8+ cubic yards Gross Capacity: 12,000 lbs; Empty Weight: 3450 lbs Empty Tongue Weight: 300 lbs Frame: 2"x6" Rectangular Tubing; Upper Rim: Angle Steel, 11ga