POLY PIPE CONSTRUCTION
What I wanted was a simple and cheap structure that would enable shade cloth to be hung over the vegetables, but allow it to be removed in winter
I grow many of my vegetables in the ground and have done so for more than 25 years. However, the summer heat is too much for tomatoes and many other vegetables, so I have in the past draped 50% white shade cloth over them, this is not very satisfactory, so at the end of 2018 I set about constructing a shade-house.
I purchased 50 metres of 50 mm agricultural green “poly pipe”, which comes in large 100 m rolls. The irrigation shop was very happy to cut 50 metres of his large roll. This cost $183. I did try 25 mm poly pipe but it was not strong enough to maintain the shape I wanted – rounded hoops about 3 metres high.
To keep the poly pipe hoops in the ground I used 1800 mm fence “star” pickets which cost $7.14 each. Don’t get these from your local garden shop, they will charge almost double; I went to a steel outlet that sold farm and fencing steel. They sold the ‘pickets’ in packs of 10.
I made seven hoops from pieces of poly pipe each with a length of 7100 mm. The base for each is 2200 mm wide, so the height turned out to be approximately 2900 mm which was adequate to pass over the top of the tomatoes. This is easy to work out. If the base is 2200 mm wide, the circle part of hoop will have a height of 1100 mm (i.e. the radius) and the total length will be pi x 1100 mm (remembering it’s only a half circle). Hence we have:
Length of top 3450 mm (pi x 1100 mm)
Sides (7100 – 3450) ÷ 2 = 1825 mm
Total length of pipe 7100 mm
Total height 1100 + 1825 = 2925 mm
I placed the Star pickets 1300 mm apart along each side of the area and 2200 mm from each other, across the structure, forming a nice rectangle. One could use closer gaps or ones that were wider, although I don’t think that gaps greater than 1500 – 2000 mm would be useful.
The Star Pickets were hammered in about 400 mm which was easy since the soil is mainly clay with few rocks – although it is very hard in summer. To bend the poly-pipe without kinking it I laid it out in the sun over lunch. This made it very easy to bend into a nice curve – which was slid over the star pickets.
Since the pipe fitted very nicely over the Star Pickets, it was easy to adjust the height. I simply slid the pipe a little way up the star pickets, and with a self-tapping screw held it in place.
To tie the poly-pipes together one could use a range of materials. I chose 25mm polyvinyl chloride (PVC) water pipe which I painted green. These were held onto the poly-pipe with 25mm saddles, screwed in with 10g x 25mm self-tappers.
I intend to tie the hoops together with five lengths of PVC pipe. I thought I might need internal braces, but with the 50% shade cloth under 75 km winds (we get severe winds in summer here), the structure has not moved an inch.
The (nearly) finished structure.