Cob: Tension Cable Variation of Jelly Logs

[RobertCCardwell at aol.com]

Jelly Roll Design 

By Robert Cardwell, 1/26/02

I have a property in rural Indiana, in a nature preserve area, about 100 
yards from a lake on a hill with many trees.

I have been pondering the idea of building an alternative structure there for 
a few years. I have read about adobe, earth bags, rammed earth, earth ships, 
etc.   I have been very excited by these alternative designs.  However, I had 
two problems with most of them. The first is cost and the second is manpower. 
  I am one poor man.  Most of the projects have some expense or can only be 
accomplished by a group or community action. So the principles of cost and 
manpower have guided my design thoughts.

I have come up with a design idea, which is very eclectic and borrows from 
many of the alternative building ideas.  I wanted to get the economy from 
some designs, environmental empathy from others, strength from some, and ease 
of construction from others.   Finally, I wanted a design which allows 
artistic expression and has the possibility of being very life enriching.

I have come up with the idea of a jellyroll design.  The seed of this idea 
came from a recommendation to mix cob on a sheet and then to use the sheet to 
manipulate the cob.  I came up with the idea of why not just use the sheet in 
the construction. Sheets of plastic, burlap, hemp, cloth, woven fiberglass, 
are relatively inexpensive.  Why not just mix up the substance, tamp and 
compress, roll this up in the plastic, tie off, and viola…you have an earth 
or artificial log.  The size of the log could be determined by the size of 
the workforce.  The log could be laid like earth bags to build the wall.


            I have done a lot of thinking on this design.   It has the 
benefits of earth bags and the ease of cob.  The jelly of the log could be 
very diverse as the sheet depending upon the location and application of the 
log in the structure.  For example, the foundation, or base structures of the 
wall could be built with a plastic sheet and a concrete, earth, or earthcrete 
"jelly".  

As the wall was built up, the material could change.  For example, the upper 
course could be of a more breathable sheet and lighter jelly.  Perhaps, even 
a papercrete jelly could be used with plastic and earth jelly with a burlap 
[or hemp] sheet.

Another key design idea could be what the center of the jellyroll was made 
of.  This center of course would be long and could be made of steel, plastic, 
or wood as need.  For example, a lintel may be made of a fiberglass sheet, a 
concrete jelly, and a rebar "rolling pin".  Perhaps, even a rope of some 
substance [maybe even a steel cable] could serve as rolling pin of sorts and 
the logs could be tied off in a variety of ways. An upper course, or ring of 
a dome roof could be made by a sheet of 6 mil plastic, with a 1 inch PVC pipe 
rolling pin, and a jelly of papercrete.    PVC tube rolling pins could also 
be used in mid wall courses to serve as conduits for plumbing and electrical 
wires.

Most of my design ideas have been centered around building a beehive or domed 
structure.   The jellyroll logs would be laid in rings of decreasing sizes 
until the dome is formed.

Some of my other ideas are to do experiments with the wrapping sheets and 
filler substance. Some possible filling substances: waste paper, wood chips, 
gravel, sand, sawdust, etc.  A chipper could be used to re-cycle a variety of 
substances.

Another idea would be to experiment with the need for mortar.  The mortar 
between the log courses could be as simple as the use of barbwire as in earth 
bag construction.  The mortar could be cob or some other experimental 
substance.

The covering of the external structure could be with adobe, stucco, or earth 
plaster. The interior, windows, doors, and furnishing could be made by using 
"conventional" alternative building designs.

Another thought I have had is to lay out a lattice of strips on the sheet, 
fastened to the sheet with staples.  As the sheet of the jelly roll could be 
many substances, the lattice of strips could be of many different material 
type and elongated shapes.  It could be long poles of bamboo, plastic tubing, 
wood rails, or perhaps even a rope made of various substances. Maybe a lat of 
wooden poles or straight branches would work just as well. Then just lay the 
lattice sheet out, tamp on the jelly of a variety of substances, and roll up 
to form a log. The jelly would provide the compression strength and the lats 
would provide the tensile strength.

These ideas are perhaps the meandering thoughts of a loon, but I would 
appreciate any considered feedback.  

I have toyed with the idea of using a design of tension cables, suspension, 
and chain link fence to build an earthen yurt. Or with designing a system of 
suspension with the centers of the jelly rolls be a rope, cable, or fence 
wire to build a square building. Basically, the four corner poster would be 
set in a heavy concrete footing. Top beams would be attached to this forming 
the structural frame of the box.  As each course of the jelly log were laid, 
the center cables would be attached and then that course would be tied off at 
one end to the corner post, then the tension of the cable would be tightened 
with a winch and then attached to the other corner poster.  For the roof, a 
weave of tension cable  would be attached to the bottom of the top beams in a 
four inch pattern.  On top of this weave of cables would be laid a flat 
course of jelly logs made of 6 mil plastic, a paper crete jelly, and a PVC 
pin. The ends of the jelly logs would butt against the top beam. A second 
layer of paper crete jelly rolls would be laid at a 90 degree angle and 
butted against the top beam.  The cables would be tightened after the paper 
crete rolls have cured compressing against the beams. This would be covered 
with a water proof membrane and serve as the exposed roof.
Thank you for your time in reading this.

Bob Cardwell   
 robertccardwell at aol.com