2011 rule changes - blade-style roll hoops 03 February 2011
This blade-style roll hoop design (main drawing) was introduced by Mercedes in 2010 in order to improve airflow to the rear wing. For 2011 the FIA has decided such solutions could prove dangerous in incidents of cars rolling on a soft surface such as grass or sand, where the blade could cut into the ground. A minimum cross section has thus been imposed, to discourage similar designs.
FIA Technical Regulation
15.2.4 - The principal roll structure must have a minimum enclosed structural cross section of 10000mm², in vertical projection, across a horizontal plane 50mm below its highest point. The area thus established must not exceed 200mm in length or width and may not be less than 10000mm2 below this point.