Alan - it looks like you can get them from pretty much anywhere! For instance looking on eBay I find photographs exactly the same as the ones Brum has posted earlier.
Hi all, before I post pics of all the latest work done today, here's one of how I decided on the exact size of base to make. I originally wanted it to be roughly 4ft x 2 ft to fit the space available in my shed but decided to make it an exact fit to multiples of standard seed trays by laying them out on the plywood I used for the bottom then adding 2 x the thickness of the decking boards used for the sides. This is how it turned out:
A trowel in the hand is worth a thousand lost under a bush.
I worked out that it would take 4 x 25kg bags of sharp sand to fill it to the required depth (4 inches: 2 inches below the heating cable and 2 inches on top.) As that meant the whole thing would weigh over 100kg, very sturdy support would be needed! I used 50x50mm (2x2 inch) timber to make a frame and used steel legs from an old office desk I found in a skip:
Pic below is it in place on top of the frame:
A trowel in the hand is worth a thousand lost under a bush.
Next would be to line it with insulation so that the heat would be retained. I had a roll of polystyrene insulation which was left over after fitting a laminated wooden floor in my conservatory (which has a concrete floor.) This stuff is very cheap and ideal for the job:
First layer stapled in place:
Second layer now stapled (with galvanised 12mm staples) and trimmed:
A trowel in the hand is worth a thousand lost under a bush.
I used a 6m long Parasene soil heating cable as this is the recommended length for a 4'x2' propagator and is rated at 150W:
it needed feeding through 13mm a hole (there is a blue seal on the end of the cable which needs to go through the hole) in the side which was made 2" (50mm) from the bottom of the propagator:
A trowel in the hand is worth a thousand lost under a bush.
Now for the tricky part! Somehow the cable needed laying evenly so it covered the whole area without any loop touching another loop or any crossing cables as these would cause hot-spots. The trick here was to plug the cable in for 10 minutes to let it warm up, making it more flexible. However, it wouldn't stay in place even if I patted it into the damp sand, so I came up with an idea - use pieces of decking to temporarily hold it in place - these will be removed later:
Clever, eh?! Now I filled the gaps between the bits of wood with more sharp sand which would hold the cable in place:
removing the wood left it like this, ready for adding the rest of the sand:
A trowel in the hand is worth a thousand lost under a bush.
The final top 2" layer of sand was then completed:
and depth checked:
Finally, this is it with 8 seed trays in position. Each one is effectively a propagator in it's own right so that it's lid can be removed when seeds show signs of germination, without affecting any of the other trays. To the right you can see the thermostat - this is a fancy one I already had and the probe is on a cable so can be placed inside a seed tray rather than in the sand if I wish. However, it is really an overkill and the standard Parasene thermostat would be fine:
I've set the thermostat to 25C as a test tonight and will check in the morning. I filled one seed tray with compost and put my max-min thermometer on top before covering with the lid. That should give me a good idea of how warm the compost in the trays will actually reach when the sand is at 25C. Fingers crossed!
A trowel in the hand is worth a thousand lost under a bush.
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i am simply doing this as iv been trying to get a smiley box and its just happened i think Daniels got his wand out hope it stays on mipostbox
Alan - it looks like you can get them from pretty much anywhere! For instance looking on eBay I find photographs exactly the same as the ones Brum has posted earlier.
cheers for all that info ,im onto it
Hi all, before I post pics of all the latest work done today, here's one of how I decided on the exact size of base to make. I originally wanted it to be roughly 4ft x 2 ft to fit the space available in my shed but decided to make it an exact fit to multiples of standard seed trays by laying them out on the plywood I used for the bottom then adding 2 x the thickness of the decking boards used for the sides. This is how it turned out:
I worked out that it would take 4 x 25kg bags of sharp sand to fill it to the required depth (4 inches: 2 inches below the heating cable and 2 inches on top.) As that meant the whole thing would weigh over 100kg, very sturdy support would be needed! I used 50x50mm (2x2 inch) timber to make a frame and used steel legs from an old office desk I found in a skip:
Pic below is it in place on top of the frame:
Next would be to line it with insulation so that the heat would be retained. I had a roll of polystyrene insulation which was left over after fitting a laminated wooden floor in my conservatory (which has a concrete floor.) This stuff is very cheap and ideal for the job:
First layer stapled in place:
Second layer now stapled (with galvanised 12mm staples) and trimmed:
I used a 6m long Parasene soil heating cable as this is the recommended length for a 4'x2' propagator and is rated at 150W:
it needed feeding through 13mm a hole (there is a blue seal on the end of the cable which needs to go through the hole) in the side which was made 2" (50mm) from the bottom of the propagator:
Next was a 2" layer of sharp sand:
Now for the tricky part! Somehow the cable needed laying evenly so it covered the whole area without any loop touching another loop or any crossing cables as these would cause hot-spots. The trick here was to plug the cable in for 10 minutes to let it warm up, making it more flexible. However, it wouldn't stay in place even if I patted it into the damp sand, so I came up with an idea - use pieces of decking to temporarily hold it in place - these will be removed later:
Clever, eh?!
Now I filled the gaps between the bits of wood with more sharp sand which would hold the cable in place:
removing the wood left it like this, ready for adding the rest of the sand:
The final top 2" layer of sand was then completed:
and depth checked:
Finally, this is it with 8 seed trays in position. Each one is effectively a propagator in it's own right so that it's lid can be removed when seeds show signs of germination, without affecting any of the other trays. To the right you can see the thermostat - this is a fancy one I already had and the probe is on a cable so can be placed inside a seed tray rather than in the sand if I wish. However, it is really an overkill and the standard Parasene thermostat would be fine:
I've set the thermostat to 25C as a test tonight and will check in the morning. I filled one seed tray with compost and put my max-min thermometer on top before covering with the lid. That should give me a good idea of how warm the compost in the trays will actually reach when the sand is at 25C. Fingers crossed!