Subject: Re: American Ingenuity Domes

From: [email-masked] (Nick Pine)
Date: 22 Mar 1995 15:44:06 -0500

<[email-masked]> wrote:

>Some alternatives:

>My brother-in-law has built many domes using a process from some construction
>company in Texas...

Yup, that's Monolithic Constructors, Inc.

>First, pour the foundation, and inflate the balloon on top of it...
>I've heard they will make custom shapes.

True, with some physical limitations, eg convexity.

>From inside the balloon, you spray the inside with 6 inches of foam.

Actually, they start with an inch or so, and that's probably all you need,
altogether, if you passive solar heat the dome. They usually use 3" of foam.

>Once the foam has hardened, the balloon shape is supported by the foam.

True, but more interestingly, perhaps, is that small pieces of sheet metal
with protruding wires ("skyhooks") are stuck on the foam while it is still
very sticky. These later serve as supports for wiring up reinforcing rod,
which I feel is probably not necessary.

>Then you weave reinforcing rods against the inside surface...

[Wiring it up to the skyhooks]

>Next spray concrete on the inside of the shell...

Too much concrete, I think. They use 2". Seems like it could be 1/4",
over wire mesh, not rebar. The 2" of concrete makes it fairly earthquake-
proof and tornado-proof and nuclear-weapon proof, but many houses don't
need that and aren't designed for that. I'd rather have a very inexpensive
house with ordinary structural performance than a house with normal
cost and super performance.

And it seems to me that all this would work better for small domes if
they started with a lightweight geodesic wood frame, covered that with
poly film, evacuated the structure slightly, sprayed on an inch of foam,
added the skyhooks, stapled wire mesh on the flat triangles, troweled on
1/4" of cement, and nailed thin galvanized metal on the outside.

Nick