Soil Bed Preparation - Hoops

I had previously talked about our Row Caterpillars as part of the plan for Season Extension.  We believe that we could extend the growing season (which in Indianapolis is 181 days) by 4-6 weeks on either side.  That could push our growing season from 6 months to as much as 9 months!  So how do we go about constructing this tunnel?

There's a couple of things we'll need.

1.  1/2" EMT (Electro Metalic Tube)
2.  10' long rebar
3.  Hack saw
4.  Tape measure
5.  EMT Pipe Bender
6.  Sharpie

Begin by measuring out 5' (half way) on the first piece of rebar.  Use the hack saw to cut the rebar at the measured cut.

Now take all subsequent pieces of rebar and simply line one end up with one of the first cut pieces and cut at the matching end.  The rebar is going to serve as our anchors for the hoops.  We will knock the 5' pieces into the ground until 3' is underground and only 2' is left protruding above ground.

Now that the rebar is cut, it's time to measure the EMT.  The pipe bender has a 10 degree bend angle line, and that's what we're going to use to get our hoops bent.  If we consider one half of the hoop (1/4 circle) the direction change from vertical where it will start at ground level to horizontal where it will meet the other end, is 90 degrees.  Given 10 degree bends, we will need 9 bends in order to make the half hoop.  Given the length of our EMT, we will make these bends every 6" starting at 12" to allow some middle extension to bring the two sides together.  Using the measuring tape, mark at 12", 18", 24", 30", 36", 42", 48", 54" and 60".



Now turn to the other end of the EMT pipe and measure off 18".  This is 18" we're going to cut off to lower the tunnel so as to not have any excess air inside.  Remember that any air inside the tunnel needs to be warmed at night by the passive radiation of the water barrels.  The less air we have the more effective the barrels will be so it's important to keep the tunnel size as small as is practical while still fitting all the components inside.

Now take your other 7 pieces of EMT and align them on the ground with the piece we just marked.

Now, using the Sharpie, simply draw across the other pipes at each mark in order to mark them quickly and efficiently.

Next we position each piece of EMT into the pipe bender in turn.  Align the marker with the Sharpie mark on the short side of the pipe.  I can't stress this enough.  Bending pipe is about leverage so you do NOT want the short side to be the side you're bending.  Once aligned, simply bend the pipe until the longer side aligns with the 10 degree mark.  It's also easier to align when you have the longer side here.  Don't worry about getting the bend exactly at 10 degrees.  By the time you've made 9 bends, I guarantee you your hoop is going to bend 100 degrees plus and you'll have to bend back a little to get it to 90 degrees properly.  Don't worry... it doesn't have to be perfect.

One thing to ensure is that you keep the bent section of pipe level off the ground.  Failing to do so, will cause your bends to form a spiral which isn't good.

Continue until all your EMT has been bent to 90 degrees.

Now cut off the 18" piece at the bottom of the EMT.

After placing the 6 plastic 55 gallon barrels on the north side of the raised soil bed, we hammer the rebar into the ground until 3' is underground and only 2' protrudes above ground.  These form the anchors for the EMT pipes.  One anchor is at each of the 4' sides of the bed.  Given that we're using 9 cinder blocks on the 12' side of the bed, the other two anchors are driven into the ground between the 3rd and 4th cinder blocks as well as between the 6th and 7th blocks.

Once you've driven the rebar into the ground, slide the EMT pieces over the top.  Connect the ends over the bed with a simple coupling connector.  Once the 4 ribs are connected, your caterpillar frame is ready for the plastic cover, but that's a topic for tomorrow.

Joint us again tomorrow as we look at covering the hoops with plastic to complete the caterpillar tunnel.