The rotor spindle and controls pass through {HEAD ~ a central hole} between {TAIL ~ the spar caps} 
between
The rotor spindle and controls pass through { HEAD ~ a central hole } between { TAIL ~ the spar caps }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL