How to make nylon-cement shells
How to create a hemispheric nylon/cement shell out of a nylon fishing mesh/cement composite over a male sand/earth mold:
1. Use a a string attached to a stake to draw a circle in the sand/earth.
2. Lay down a large piece of cardboard, large enough to completely cover half the circle. Glue several layers together if necessary to make the carboard rigid.
3. Cut out half the circle from the cardboard, leaving the half-circle as a negative space in the remaining cardboard.
4. Pile the sand/earth to the desired height, and shape it to a rough half sphere. Rotate the card board form up and over the pile, smoothing the sand/earth into a uniform sphere. Fill any gaps as necessary.
5. Once you have a satisfactory male mold, overlay it with a layer of nylon cement, as described by Bill Birdsall (1)
6. Once the shell hardens, you should still be able to cut out hatches, windows, etc.
7. Create a second shell the same way.
8. You could join the two shells by leaving a layer of mesh exposed extending beyond the edge of one of the shell. Once the shells have hardened, you could put the shell with the lip of mesh on top of the other, and then cement the lip to the bottom.