restart; with(plots):

g := [cos(s),sin(s),s];

sigma := expand(g + diff(g,s)*t); #Tangential Developable of g

P := plot3d(sigma,s=0..2*Pi,t=0..1,grid=[30,3],axes=boxed,color=blue):

Q := plot3d(sigma,s=0..2*Pi,t=-1..0,grid=[30,3],axes=boxed,color=green):

display({P,Q});