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Strawbale Archive for March 2002
489 messages, last added Tue Nov 26 17:42:50 2002

[Date Index][Thread Index]

SB: Re: Re: Blown bales and an introduction of Hank, Anita, and Melissa.




----- Original Message -----
From: "Hank Carr" <hank@dna.ca>
To: <strawbale@crest.org>; <marcus1@sonic.net>; "Ben Polley"
<info@harvesthomes.ca>
Sent: Saturday, March 09, 2002 2:01 PM
Subject: SB: Re: Blown bales and an introduction of Hank, Anita, and
Melissa.

<snip>

> I can only give you our reasons.
>
> By stacking on edge you get a slightly thinner wall which we feel
> improves the aesthetic of the walls, along with the door and window
> openings.


 You get less of that tunnel effect from a 16" wall vs a 19"
> wall.

Just a note--we vary the depth of window placement (sometimes) according to
the size of the window and somewhat according to the size of the room.  The
"tunnel" effect can be controlled in this manner.  Larger windows, and
definitely window seats, can be placed more toward the outside; smaller
windows to the inside.  We always set windows in at least 6", more often 8",
to maitain the nice scruptural effect of a bale wall.

>Thinner walls also slightly increase the total floor area of the
> building.  Stacking with bales on edge reduces the total number of
> strawbales used in the building which doesn't make a huge difference
> since we paid $2.50 CAN per bale stored over the winter and delivered to
> our site as needed (within reason).

I once calculated the area taken up by bales to be about 2-3% of the cost of
the building (mostly for foundation under and roof over).  That would give
you a savings of about 0.5% of the cost of the house by flipping on edge.

>
> The vertical orientation of the straws within the bales reduces the
> total amount of compression required to stabilize the wall before the
> application of the plaster and we believe will reduce any settling after
> the plaster is applied.

Now, I believe we're getting into myth, unless the Moosehuggers are
carefully feeding your straw into the baling machine to make sure all the
straws line up.  Our rice farmers adamently told us, and our own
investigatative team has verified, that they are random.  Certain crops, and
barley may be one of them, tend to be sticking up a bit straighter than
others when cut, and so make for a more orderly bale (we wouldn't want
disorderly bales, now would we?).  And whether the straw is winnowed prior
to baling will make a difference, but the idea that the straw is all
pointing in one direction, in the bales we've torn open, is largely an
illusion created by how they are cut and bundled.

 We also feel that the reduced compressibility
> of the narrower cut and folded edges compensates for the fact that they
> are 20% narrower than bales stacked on their faces.
>We believe that the
> higher compressibility at the edges of the faces of the bales make face
> stacked and edge stacked walls equally stable.

More myth, I think.  Since the bales are restrained on all four sides (and
the straws oriented somewhat or totally randomly), the ultimate pressure of
compression would be almost the same regardless of whether the bale is flat,
sideways or on end.  If there is a difference in initial compressability,
it's probably overrated.  Data about compression needs to be carefully
considered, because of the Principle of Creeps Over Time, which states that
if someone or something is under pressure for long enough, he, she, or it
will get creepy. A wall could be Big, Strong and Tough immediately after
it's been squeezed, but come back later and it will be different--the bales
creep and the straw may crush until an equlibrium is reached.  We don't know
what that equlibrium is, or exactly the relationship between heavy
compression and creep, but we do believe that it's more a factor of the
straw than of how it's baled and/or compressed. The Hot Tub Gang plans to do
some testing in this area, too, just as soon as we get out of the tub.

> Additionally, we feel
> that the much touted slippery side surfaces of the straws make the face
> stacked bales much more likely to slip against each other in the stack
> that edge stacked bales which lock together

Slip won't be an issue until or unless the bales come under very large sheer
stress; which is to say that this isn't an issue unless you are making a
really high performance bale wall.  Slip is mitigated by compression; after
compression you have two flat hard surfaces grinding into each other, which
is probably adequate.  Shear within each bale is minimized by restraint
along the wobbly direction--ie, bales can get snakey on edge, but not when
flat.  We generally consider this a minor issue, but for "high performance"
would favor flat bales  Like Marcus said, it doesn't make too much
difference, not enough to get us out of the hot tub.

<snip>

>  We feel that the danger of a wind
> load failure of a wall is very unlikely once it's stacked, wire
> compressed, fenced, and faced with a minimum on an inch of cement and
> lime plaster on two side (the power of stressed skin panels in action.)
> We will be building our building as stacked boxes so the unsupported
> wall height will be only ten feet for the first floor and eight feet for
> the second.

You do have a protected site.  Sounds lovely, and you seem to have an army
of pigs nearby to protect against the bad wolf.  But understand the the
bottom floor of a two-story is going to take more than twice the loading of
a single story, and it's all in how it's been detailed to hold together.

<snip>

>
> Hank.
>
> P.S.  Kind of got off topic there.  H.
>
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