Cob: Re: Cutting holes in cob

[baco@pacinfo]

A guy I work with was just telling me this story:

He needed to make a crawl space under a hundred year old house in order to
work on a floor joist problem. He cut a hole in a closet floor and used a
shop vac and small digging tool to tunnel in. He got the idea after watching
a city crew use a "snorkle" to drill hole for a power pole. The Snorkle is a
huge truck mounted vacuum that is used to clean catch basins. The city crew
used a fire hose to make mud and then sucked up the mud (and rocks) with the
snorkle.

My thought is: What if you used a pressure washer to cut through the wall?
If you were in an area where the water runoff would be an issue, you could
use a wet/dry shop vac or a diaphraghm pump to remove the water and clay.
Costco carries a nice little unit for about $100.

Now that I think about it, a high pressure of stream low flow water might be
usefull in mixing cob as well.

Today I found a house on a flat half acre with access from two streets,
front and back. If I can make the deal, I can have my hippy dippy cob
wonderland in the back and still have the urban tract house that my urban
princess wife wants. Wish me luck Cobbers!

Brian Bray
Eugene Oregon




----- Original Message -----
From: "Shannon C. Dealy" <dealy at deatech.com>
To: <coblist at deatech.com>
Sent: Friday, July 04, 2003 11:15 PM
Subject: Cob: Cutting holes in cob


> On Fri, 4 Jul 2003, Taylor Publishing-DirtCheapBuilder wrote:
>
> [snip]
> > Elishiva said  the cured cob was so hard it took 3 long weeks with a
> > pick ax (tough manual labor) to open a small window portal through the
> > thick cob.  They assumed it would be easy too...we all keep trading this
> [snip]
> > Anyone else have an easier time of it? We need anecdotal evidence so the
> > real work tally can be known.
>
> The difficulty is going to vary greatly depending on your mix
(particularly
> if there is alot of rock in it), how dry it is, and how you approach
> making the changes.  Depending on what you are trying to do, different
> tools and approaches may be better.  Some things I have done:
>
>   - 3" hole through a wall using a hole saw and electric drill, worked
>     fine until it hit the core of the wall which still hadn't dried,
>     then the cob would fill up the hole saw and I would have to stop every
>     minute or two to clean out the hole saw blade unit.  Time to drill
>     a 3" hole through 16 inches of cob was about 30 minutes.
>
>   - removing cob from under a window frame to relieve stress due to
>     an unexpected degree of shrinkage and settling.  Used an old
>     (junk) broad bladed wood chisel and hammer to cut the cob away.
>     It took quite a bit of time, but mostly due to making small cuts
>     in order to avoid damaging the window frame.   It works quite well
>     for precise triming of areas.
>
>   - Reciprocating saw (sometimes called a "saws-all") with a heavy duty
>     blade works pretty good for many applications
>
>   - Small hole in a hurry (such as for running wire through a wall), a
>     piece of solid steel rod longer than the wall is thick can be driven
>     through the walls with light weight hand sledge in about a minute.
>
> I haven't had need of any larger scale holes, though I will need one about
> a foot across in the near future.  I suspect that the fastest approach
> might be to get or make a large broad bladed chisel with a really long
> shaft and drive it through the wall repeatedly to cut the outline of the
> hole, then knock the center out with a large/heavy sledge hammer, and trim
> the hole afterwards with a reciprocating saw.  Alternatively, it might be
> possible to do it directly with a good reciprocating saw and some really
> long blades (though probably you would have cut the hole from both sides
> in order to get all the way through the wall).  It might be interesting to
> try using a wood splitting wedge (I think I have seen some with long
> handles) and a sledge hammer to cut the hole.
>
> FWIW.
>
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
>                       |    Embedded Systems, Real-time, Device Drivers
> Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
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>