in the segmental section the back is part of a circle, this is many times used where there
is a requirement of a, typically these sections are used in propellers for trollers where you
require not only free running speed, but also some amount of pull that one must exert such as,
hauling a troll net or something like that. In many propellers there is a combination of both
aerofoil section and segmental section that is, aerofoil sections up to a certain radius and then
the section slowly change to segmental section- we will see some of these propellers later on