[GSBN] straw bale dimensions - Hand made bales

[martin hammer]

Hello Andy,

Glad to hear things are progressing.  Given my experience with the handmade
bales in Pakistan and Haiti, I recommend 12²x12²x24² (300mm x 300mm x 600mm)
bales.  I wouldn¹t go much less, especially if insulation is an issue (for
heating climates).  And during construction it feels like a wall any thinner
might be pushing it in terms of structural stability for an 8¹ (2450 mm)
high wall for load bearing walls.

That said, in tropical climates like Haiti, where insulation isn¹t so
important (although still an issue for keeping the interior cool, or even
warm in the mountain regions) Andy Mueller and I discussed how small we
think we could go, in order to be more resource efficient.  We¹ve considered
trying 10²x10²x20² (250mm x 250mm x 500mm) bales, but haven¹t tried yet.
Going this thin or thinner you would have to see what works for out-of-plane
stability.  Either with some type of mesh, or the frequency of external
pinning (presumably bamboo where you are).  On the other hand, if this is
post and beam with straw bale infill, it makes the prospect of thinner bales
(even less than 10², 250mm) more plausible.

Regardless of the thickness, I like the length to be twice the thickness for
a good running bond and ease of turning corners.  Also, when making your own
bales I like the thickness to be the same as the ³height².  Or I can¹t think
of a good reason to do otherwise.  If nothing else you can put bales ³flat²
or ³on-edge² and they are the same thickness and height.  I¹ve found there
are sometimes reasons to mix the orientations within the same wall or
building.  

One other thought on going small with bales, at some point smaller bales
mean more labor and hassle dealing with more units (even though you might be
saving material).  I¹m not sure where the threshold of diminishing return
is, but I suspect it¹s somewhere around the 12² (300mm) or maybe the 10²
(250mm) thickness.  I suppose one could also experiment with thin bales with
a length three times their thickness, in order to have fewer units, but I
think they might become flimsy.

My experience tells me the same density as ³normal² bales works well for
small bales (7-8 lb/cu.ft or 110-130 kg/cu.m).

This brings up the proprietary Oryzatech Stak Block, which are highly
compressed, self binding, interlocking, and 12²x12²x24² (300mm x 300mm x
600mm).  Being developed by a California architect and entrepreneur, I think
the material/system has great promise but it hasn¹t gotten off the ground
yet.  This is a whole other subject, but is worth seeing at
http://www.oryzatech.com/stakfacts.html

I hope this helps. Darcey or Andy might have opinions also. My best advice
is to experiment for your circumstances, and trust your observations and
instincts. 

Best.

Martin



On 3/5/12 7:31 AM, "Andy Horn" <andy at ecodesignarchitects.co.za> wrote:

> Hi all 
> The project in the highlands of Lesotho, which I got some excellent input on
> from the Network ­ thanks especially to Darcey Donovan and Habib ­ for making
> hand made bales using a lorry jack press is at last staring to inch forward.
>  
> The project manager is trying to get a prototype together for the press design
> and is asking how small he can go with a baleŠ.
>  
> I am not familiar with small bales and our typical standard 2 string bales
> here are typically 900mm long x 450mm wide x 350mm high. Smallest I would say
> I have come across were as I recall about 850 long x 420mm wide by 340mm high.
> (Sorry no imperial dimensions for those of you in the StatesŠas we into metric
> system here).
>  
> Any input about if one goes smaller and what are the rules???
> Does one need to and can one make a more compact bale if one goes smaller?
>  
> Is there a recommended / ideal size for making hand pressed bales.
>  
> Kind regards,
> 
> Andy Horn
> 
>  
> 
>  
> 
> 
> 
>  
> 
> 
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