Cob: bonding layers

[goshawk at gnat.net]

Well Bob, 
It shows your thinking but in all honesty I don't think I'd use the technique. 
For one I'm not having any trouble with bonding thus I'd go by the old adage, if it ain't broke don't 
fix it. Next it just does not seem easier and less work to me, or any faster. The only function your 
derrick servces is in the placement of the cob, which is the easiest step as well as the most 
created of the steps. You know those lovely shelves, or artistic sculpures and shapes placed in the 
wall. It's the making of the cob that is the slow step, relative to the placement. 

I do generally make my cob a bit wetter than some and I generally can't got more than 8 to 10 
inches max  per day. Since my house is large enough and I generally work by myself or one or 
two others, that fact has never slowed me down once. 

Another small fact to think about, when building with superadobe / earthbags you never get the mix 
wet only damp. The reason for that is that the wet matteral does not compress well, where as the 
damp matterial does compress well. 

Oh well 
Great post Bob.

L&L
Pat



> It seems to me the building of a cob wall could be made easier, less work,
> a little faster, by using a crude derrick, something easily built with
> local materials, no costly machinery.
>  
> 
> The bucket end is dropped to the ground where the cob material mixers fill
> it.  It is then hoisted up over the wall.  From 4 to 6 feet above the wall
> it is dumped onto the wall, the force increasing its bonding.  (When  one
> stuccos a wall the mixture is slung vigorously against the wall and bonds
> to it partly from the force of the  impact.)  Cavities like those made
> with a cob finger could be first made in the top of the wetted previous
> day's wall if necessary.  Using a little wetter mix might also improve the
> bonding.
> 
> The slammed down mix does not slide off both sides of the wall because
> there is a moveable form.  This form is flexible because it is a kind of
> mat made of woven sticks 3/4 to 1" thick and allows any kind of curved in
> the wall.  The form is held in place with cord running from one side of
> the top of the wall to the other which  becomes embedded in the layer
> being built but can be easily pulled out of the "mud" at the end of the
> work on that particular part of the wall so  the form can  be moved to
> another part of the wall. The lower end of the form is held in place by
> the finished wall.  How tight the cord is will determine the taper in the
> wall, tighter a greater taper.
 
Pat Newberry
www.gnat.net/~goshawk