{TAIL ~ A related object} of the invention is to have the last step in {HEAD ~ the series} have a simple recess aft of it to thereby minimize wetted area resistance 
{ TAIL ~ A related object } of the invention is to have the last step in { HEAD ~ the series } have a simple recess aft of it to thereby minimize wetted area resistance
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH