Variable section & twist

Is the sketched section of the solid to be perpendicular to the central spine of the solid, to a neutral plane, or another feature? There are at least three different ways to do this, depending upon the geometry you want to create, all different, and none quick or easy to explain. You may be best getting someone to come & show you.

John hello, thank you for your reply. yes, the section is perpendicular to the axis of the solid. I did something following these steps: extrusion of the section to form the solid warp in which I twisted the solid I would need to reduce the section along the extrusion axis. Is it a correct procedure? Would this other way be possible?: drawing of bottom and top sections on two datum planes at a defined distance, and then blend them. Anyway it's for a turbine blade (different section and different incidence angle at the two sections). Thanks Gio

Depending on contingencies ... You might look at a Variable Section Sweep; "chord axis" primary trajectory and, maybe, section normal, a helical curve controlling section and x-vector. You could get more complex and have one curve controlling x-vector (twist) and another controlling section. Or maybe a simple Swept Blend or Boundary Blend (start and end sections req'd for either).

Some contingencies: What is (are) the section curve(s), spline, conic curves, etc? Linear taper and twist or something more complex? Start and end sections similar or something more complex?

It's a pity posting binaries (models, pics, etc.) isn't an option here (personal preference; I like usenet groups and a news reader vs. html or email exploder interface). Since it isn't; if it's not "secret stuff" I might suggest you try McadCentral or some place where you can post binaries. Information can get lost in verbal only translation. Knowing if this is simply a learning excercise or something else might also be helpful.