{TAIL ~ The foremost edge} of the hydrofoil comprises a slot covered by a continuously adjustable gate for controlling {HEAD ~ the overall drag} imposed by the turbine 
{ TAIL ~ The foremost edge } of the hydrofoil comprises a slot covered by a continuously adjustable gate for controlling { HEAD ~ the overall drag } imposed by the turbine
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH