Flex generates propulsion, like a dolphins tail, producing forward drive.

Flexible forms can change shape while in motion. It’s the closest possible thing to a living creature, like a sea bird which will extend its wings to soar, tuck them to dive at speed, half extend them to perform a hi speed turn. A fish will alter its shape to perform turns and power drives on the hunt for prey. Jet fighters change their wing form in flight. So do jumbo passenger planes. Using flex you can get a whole range of drivelines, from short and vertical, to long extended acceleration.