[Ferro List] Flipped Boat Wallls

[Lloyd Turner]

Chuck and Chris,

At first glance it may sound hard to do but here is a relatively easy  
way to end up with any of the shapes you are thinking about using low  
pressure airforms.

Make a careful hard model of the exterior of your curvilinear design  
at a scale of, say, 3/8" = 1'  On its' surface draw lines representing  
the gores to make an inflatable airform of this shape.

Use just enough air pressure to make the fabric push out (or suck in  
wherever you think it can use a slight vacume) to the shape you have  
designed.  You don't want high pressure.  You are not trying to  
stretch the fabric, nor do anything more than for it to take the shape  
of the model (witch it will do).

In drawing the gores on the curved surface of the model, start with  
the widest width of your fabric (your choice) and skinny it down as  
the seam travels across the shape.  Mark the seams every foot in order  
to design them, cut them out, and register them with adjoining gores  
when they are being fastened together.  Use Tyvek for the airform.  
Tape or sew the gores together.  Tyvek is dirt cheap.

Anchor the finished A/F down around the base.  Inflate it just enough  
for it to take the desired shape.  Rely on bent splines where there  
are abrupt changes in the warped planes. This is the time to modify  
the airform if you see something you want to change. You can do this  
in the air with a mat knife and a pliers stapler.  The airform does  
not have to look neat.

When it looks just right, lock the airform into a rigid structure by  
applying urethane foam to the interior IN THIN LAYERS.  The first  
layer is just to wet the surface, make one quick pass from one end of  
the structure to the other.  The second layer is just like the first.   
The third layer can be much thicker.  It doesn't take any longer to do  
it this way than it does to apply a full 3 or 4 inches of foam while  
standing in one spot.  But a thick pass is very likely to deform the  
outer surface of a low pressure A/F such as this.

Now turn the fan off.  You now have a foam structure.

Hang rebars and apply shotcrete for a permanent structure.  Or  
alternately, use ferrocement.

Since Tyvek does not inhibit water vapor drive, the airform can be  
left in place when the final outer surface is added.

I've left out a thousand details.

Lloyd -



On Feb 21, 2008, at 9:38 AM, Christopher Glasspool wrote:

> Chuck,
> This was an idea that grew from a discussion on tilt up walls, of  
> which I was contemplating doing for my workshop.These flip up boat  
> shapes, are really the same thing, only with a boat shape the tilt  
> up wall also becomes a tilt up wall and roof. One can look at nature  
> for similar designs. The two that first come to mind are flower buds  
> and mollusks, such as clams. The man made example is the Sydney  
> Opera House. The boat shape is a rough description, and when you  
> start looking at it, you can see a football shape cut into sections,  
> and formed to meet function. Playing with the shapes allows you to  
> see the function of maneuverability of being tilted into position.  
> You can design these to fit together to make a domed structures, or  
> turn them in different directions to get solar orientation, or a  
> cooling breeze, northern light, or to take advantage of a panoramic  
> view. If one had the time and money (lots of it), then all of these  
> could be tuned in for one
> project.
> Ferrocement isn't fragile or brittle, but it still very heavy, so  
> having or hiring the tools necessary to move these structures around  
> would be a big project in itself. A steep slope would require even  
> more engineering for the maneuvering of the pieces. It is a fun  
> fantasy in any case. - chris
>
>
>       
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