The bottom few boards assembled.
Choice of size is done to use all the wood. The picture
shows 1.8m planks sawn in two to give a 900mm side. If planks 2400
mm long are bought they can be sawn into 3 to produce a side of 800 mm.
It is better to have two or three piles rather than
one so that that a rotation can be made. Sawing planks into 4 produces
a
side of 600 mm which I haven't tried. The ratio of surface to volume
gets higher as the size decreases, increasing heat loss and
slowing composting.
It is also possible
to assemble the planks in a
hexagon. With the 900 mm size this makes a very large pile that seemed
to take about 18 months to fill when I tried it. A smaller size as a
hexagon might be more attractive if the bin will be visible.
The sides are 50%
open. Some material will come
through the gaps when you fill it but once there is material above it
it will stay in place. The boards are simpler to make than shaped
ones that could reduce the gap. The pile will be a bit cooler as a
result but composting gets there in the end. You can also put a fork
though the gaps to aerate the pile.
Materials:
The bins in the photograph below are
made from 19 x 100 mm sawn treated softwood. The nails are 3 inch (75
mm) galvanised nails.
They start out with clout heads but these get sawn off after driving
them in.
Manufacture:
Success in making
these boards requires
that the holes are directly above each other top and bottom of the
board and the distance between the holes is the same on every board. If
this is not so it will be difficult or impossible to assemble them.
Cut up the wood into 3 or 4 pieces per plank. It is not too important
that they are the same size but one end (at least) should be square to
allow a jig or a stop to be used.
If you have a pillar drill:
Clamp a piece of wood 30 mm from the
drill and use this as an end stop. Drill a small hole top and
bottom at one
end only (the square one). These holes form a pilot for the nail. They
should be directly opposite each
other and small enough for the nail to hold in them. (Nail diameters
vary) The 30mm forms an overhang which can be used to separate the
boards when the pile is mature.
Fix a small nail, point up 840 mm (for 900 mm boards) from the drill.
Use this to locate each board on the nail using the already drilled
holes and drill a hole top and bottom at the undrilled end. This keeps
the spacing between nails constant on every board.
If you don't have a pillar drill:
You can do the same things
by measurement but take care: the nail and hole spacing must be the
same on every board. Alternatively make a jig (you have 2 edges on
every board) consisting of a piece of wood with two holes in it
and a stop to position it on the square edge of the sawn boards.
Change the drill to a bigger size, a clearance for the clout nails, and
drill
out the two holes on one edge of
each board. This is the top of the board. Drive the nails half way into
the bottom holes. Cut off the heads leaving a peg. Assemble to taste.
The nails in the bottom board dig into the soil. It is worth putting
them in as next time round they will end up on the top board.
When you come to move your boards on to the next
pile you may find that using a fork to lever on the overhang is a good
way to separate them.
