1.  Choose an actual shell to model. You  need to pick a shell where you can get a good picture of a cross section of the inside of the shell, so for example you may use any of the shell X-rays.

2.  Measure the shell to get the parameters necessary to write the equation for the helical spiral going through the center of the shell.  Plot this curve on Maple.

        (note--while I suspect in the long run the equations may be easier in cylindrical coordinates, most of the resources you will be using do things in terms of cartesian coordinates, so probably best to stick with that, at least to start.)

3.  Compute the Frenet frame at some convenient point on the curve.  Plot this with the curve on Maple.

4.  Find the normal plane at the same point, and plot this with the curve on Maple.

5.  Find a the equation of a circle with center at that point and lying in the normal plane and plot it with the space curve on Maple.

6.  Plot several circles of diminishing size up the helical spiral.