Now, the line that is the x axis is called the nose tail line joining the leading edge to trailing
edge by a straight line- can you see that? The nose tail line is the one with reference to which
the section would be defined; mind you, this is the face and this could be form the helicoidal
surface, nose tail line is not a part of the helicoidal surface, the helicoidal surface is still the
face, most of the face, and nose tail line is a line only for defining the section. You can see
there is some area below the nose tail line and some area above and what you observed is that
there is more area above than below, now, if I join the mean thickness line, I will get this
chain dotted line; thickness at any section, t, this t if I cut it into two, this is the middle point
of the section similarly, I define the middle points and join this line, this chain dotted line,
this is the so called camber line