The trough has {HEAD ~ width} substantially corresponding to that of the take off location and has a bottom and sidewalls which preferably converge in {TAIL ~ the shape} of a funnel 
The trough has { HEAD ~ width } substantially corresponding to that of the take off location and has a bottom and sidewalls which preferably converge in { TAIL ~ the shape } of a funnel
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH