[Cob] Coblist Digest, Vol 6, Issue 50

[Bernhard Masterson]

Hi Mitch,
   Couple of thoughts on your post.  Using straw is not a problem in subtropical climates for a couple of reasons.  Any good cob fiber has a high tensile strength and low nitrogen, what critters and microbes often consume.  When straw is an available local resource it fits these criteria well as it is just the cellulose fibers of the stalk that supports the seed heads of grain crops.  Cellulose is not attractive to most bugs and microbes.  Further, the straw is coated and encased in clay and sand which makes it hard to get to and moderates the humidity so that as long as the cob stays dry the clay keeps the moisture content  quite low, so that mold/mildew is not a problem.  Other fibers may be better choices based on availability but all should be low nitrogen and high cellulose with high tensile strength.
     My experience with rototiller cob has not been positive.  The rototiller did not do a sufficient job grinding the clay particles in the soil apart to release them to make good bonds and strong cob.  As a result a greater amount of clay soil needed to be added which increased the shrinkage and cracking.  Another drawback was that the tiller chopped the straw fibers to quite short lengths, which is undesirable, as the longer the straw fiber the better the knitting together of cob.

- Bernhard 


____________________________________bernhard_masterson at hotmail.com

Natural building instruction and consultation

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Message: 5
Date: Tue, 13 May 2008 09:04:52 -0500 (CDT)
From: Mitch Ventura <h_anpyp at yahoo.com>
Subject: [Cob] Rototiller
To: coblist at deatech.com
Message-ID: <269377.82351.qm at web36804.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
 
Am still gathering as much info as I can on cob building prior to my cob project sometime in late 2010 (when I should be finished here in Iraq... still a perfect region for cob but may not ever see that technology, ironic as that may seem); this Forum has been a great source for data and links to other sites (my thanks to almost everyone).
   
  Anyway, came across the following website that had a few twists on views that I have previously seen written and argued on in this Forum:
   
  www.islandnet.com/~anngord/builders.html
   
  Never thought of using a rototiller (and would have relegated it to the same negative views that I read on cement mixers).
   
  The use of added straw may not be good for me as I maintain a residence in a subtropical climate (great for bacteria, mold, termites, and other organic consumers).
   
  Wonder if the more technically inclined members of this Forum could voice their opinion on the rototiller and added straw...
   
  Ma'a salama.
   
  Mitch
  (somewhere near Sadr City, Baghdad, Iraq)
   
  P.D. Fellow firefighters laugh at me all the time as I am a bit of a tree hugger, but a realistic one at that... sure the rototiller uses some gas, but how many of us have guzzled gallons of fuel in order to attend an eco-seminar far from home? (LOIL... Lots Of Ironic Laughter)
- Bernhard 


____________________________________bernhard_masterson at hotmail.com

Natural building instruction and consultation



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