[RadPig94]

The Soviet Union used the metric system, thus 1/16th inch (1.6 mm) thick sheet aluminum and proper rivet lengths were unavailable. The corresponding metric-gauge metal was thicker; as a result, the Tu-4 weighed about 3,100 lb (1,400 kg) more than the B-29, with a corresponding decrease in range and payload.
talk about a knock-off