Screw Propeller foundry pattern (partial)

Title: Screw Propeller foundry pattern (partial)
Type: Navigation Artifacts
Description: Foundry patterns like this were carved from plans by pattern-makers. The finished pattern was placed embeeded halfway into fine sand in a frame, then another frame was set atop the first and more fine sand was packed around the top half of the pattern to fill the frame until the sand held its shape when the frames were pulled apart. With the frames separated, the pattern was removed, leaving a cavity in the sand. The frames were put together again, a hole was dug through the sand in the top frame and molten metal was poured through the hole to fill the cavity producing a new object in the shape of the pattern.