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Platform Assembly Plan.

This is the procedure to construct the ¼ scale model. It is intended to be the same procedure as used to construct the full scale platform, but scaling up usually introduces some new problems. This will be partially debugged on a 4 foot 'dollhouse' model before we attempt the 12 foot version.


One objective is to keep this low-tech enough to be practical to produce in a third-world, poorly industrilized environment, and cheap enough to appeal to low-cost housing and small business structures. In this, it has been only partially successful. The equipment and skills required are modest. The bulk materials are low-tech commodoties worldwide. But some of the materials are only made in well-industrialized contries, eg polyethylene sheet, mylar packing tape. Fortunately, these are relatively compact and inexpensive to transport, and relatively small quantities are required.

The platform (also referred to here as module or tile) is cast literally in a hole in the ground, lined with polyethylene sheet, a small amount of steel remesh, and some (reusable) plywood wall spacers. The casting is done in several stages, resulting in a structure with a skin of normal density concrete, and an interior consisting of a honeycomb of hexagonal rooms. The interior is cast from lightweight cellular concrete. This material is used to raise bouyancy, reduce materials cost, and permit the use of a novel casting technique that is cheaper than conventional mold-building.

This is called 'neutral bouyancy water-bag casting'. First, a layer of normal concrete is poured to form the skin of the underside of the tile. Then a measured amount of cellular concrete is poured over of it. The cellular concrete is formulated to have the same density as water, by controling the volume of air/detergent foam entrained, so it floats on top of the higher density concrete. Next, an array of plastic bags (made from 6 mil poly sheet) is placed on top of the fresh cellular concrete layer and filled with a measured amount of water. Since the water has the same density as the cellular concrete, the bags become spheres suspended in the concrete. When elastic balls are close-packed, they form a honeycomb of hexagonal cells. The walls of this honeycomb are concrete. When the concrete has set, spacers are removed from the perimeter, making room for a layer of normal concrete that will form the skin of the outer walls. This space is filled until it overflows and forms a layer of normal concrete on top of the honeycomb of cellular concrete and water bags. This will be the skin of the top surface. When the assembly has partially cured (5-7 days) the bags are punctured and pumped out. Now we have a small floating building with lots of unfinished interior space.

There are a few more details to take care of:

Stepwise procedure