How to Build an EcoPropagator

Latest Update 3rd March 2017.

The EcoPropagator (the one in the middle of the photo above) uses its external 9mm marine ply walls to contain the water tank instead of using a bin.

External plantation pine (42 x 19mm) horizontal bracing is used to support the front and back walls.  I use five 30mm gal button head wood screws to fix each brace to a wall and 75mm gal c\sunk wood screws to secure the end walls to the bracing (1 in each end).

The same plantation pine timbers are used to make the frame for the propagator's cover, and 75mm gal c/sunk wood screws are used to join the horizontal and vertical members (2 per joint).  The frame is covered with 0.9mm polycarbonate sheet in winter and 75% shadecloth in summer.  Blocks are fitted to the underside top of each vertical leg so the frame doesn't slide off the propagator.
The whole area inside the cold frame can be used for propagating by using 2 layers of 200 ┬Ám plastic sheet as a liner for the water tank.

The plastic liners (which rest on the ground) are suspended in position by stapling them along their top edges to the walls of the propagator.  The design of the filling, distribution and overflow unit is similar to that used in full sized Ecobeds.  The water tank depth is 160mm.
This picture shows the tank being filled with rainwater and Scoria.  When the water starts to overflow, more Scoria is added until they are both the same level.

A piece of horticultural fabric is placed over the Scoria and cut 25mm oversize on each edge so it can be turned up the sides of the unit to seal the tank when the compost is added.
About 100mm of sieved compost is added to the bed.  This compost stays moist at all times as water is wicked up from the water tank.  Up to 90 mini pots and small jiffy (fibre) pots containing seedlings growing in organic potting mix are buried up to their rims so that moisture and beneficial microbes can migrate from the biologically active compost into the seedling's root zone.  Here the microbes quickly establish symbiotic relationships with the seedlings.

A timber frame is covered with vegenet for the warmer months.  It keeps insect pests out of the propagator and shades delicate seedlings from hot sun.  In the cooler months, the vegenet is replaced with 0.9mm thick polycarbonate sheet to trap sunlight and maintain a moist warm environment inside the unit.  To maximise the heat gain, black plastic sheet is pinned to the back wall during those months.
Vents are installed in the top corners of the propagator to remove air if it gets too hot on sunny days in the cooler months.