An unmanned aerial vehicle according to certain embodiments generally includes a chassis, a power supply mounted to the chassis, a control system operable to receive power from the power supply, at least one rotor operable to generate lift under control of the control system, and a winch mounted to the chassis. The winch includes a reel and a motor. The reel has a line wound thereon, the line having a free end. The reel includes a circumferential channel in which a wound portion of the line is wound onto the reel. The circumferential channel includes an inner portion, an outer portion, and a passage connecting the inner portion and the outer portion. The motor is operable to rotate the reel under control of the control system to thereby cause the line to wind onto and off of the reel, thereby causing the free end of the line to raise and lower.