Will need
To assemble the arched frame of the greenhouse, we select, based on considerations of ensuring the necessary load-bearing capacity and minimizing costs, round PVC pipes with a diameter of 15 mm. Both the arches themselves and the longitudinal element will be made from them, which will connect the arches to each other and create a load-bearing structure of sufficient rigidity and strength, designed to withstand the maximum snow load and wind pressure.
For a greenhouse measuring 1220x2440 mm, three arches are enough. If your region has snowy winters and strong winds, you can add another arch to give your greenhouse frame additional strength and rigidity. The ends of the arches can be fixed both outside the wooden base and inside. To be certain, we will choose the last option.
Determining pipe length
To determine the length of arch blanks in the form of a semicircle or so for a greenhouse with a width of 1220 mm, we use the mathematical relationship between the circumference (C) and the diameter (D), which in our case is equal to the width of the greenhouse, that is, 1220 mm.
C = πD = 3.14 × 1220 = 3831 mm.
Then the length of the pipes (L) from which we are going to make arches will be equal to half the length of the circle we calculated:
L = C/2 = 3831/2 = 1916 mm.
If you want to make the greenhouse a little higher, then the sufficiently obtained length of the pipe blank from which the arches will be made should be increased slightly, for example, to a size of 2150 mm. Then the cross section of the greenhouse, instead of a semicircle, will have the shape of an elongated semicircle, i.e., a semi-oval. We cut 3 or 4 pieces with a length of 2150 mm.
To select the length of the longitudinal element that will connect the arches at the top, we lay a three-meter pipe on the base parallel to the long side. We rest the end of the pipe against the cross member of the base from the inside. After that, at its other end we make a mark at a distance of 25 mm from the other inner edge of the crossbar to the larger side and cut off the excess with a hacksaw. This additional 25 mm will be needed to securely connect the longitudinal element to the arches.
Making a greenhouse
To secure the arches, we drive in pieces of reinforcement with a diameter of 12 mm and a length of 500 mm in the four inner corners of the base and in those places where the intermediate arches will be installed, leaving a 150 mm pin above the ground.
Next, we fix one end of the arch blank one by one on the pin, bend the pipe and put the second end on the mating pin.
Before attaching the longitudinal element of the greenhouse frame to the arches from below, we put plastic plugs on its ends, which will protect the plastic film from tearing when it is stretched onto the finished frame.
Then, using metal U-shaped clamps of a suitable size, we fasten the places where the longitudinal element intersects with the arches. Considering the elasticity of plastic pipes, it is enough to tighten the clamp nuts by hand, but you can also tighten them slightly with a wrench.
Now you can stretch the plastic film over the assembled frame so that a strip of film remains on all sides.
We'll tell you why this is needed a little later. To increase the reliability of shelter for plants, polyethylene film can be secured to the arches in several places using pieces of rubber tube 75-80 mm long and cut to length on one side. To prevent the tubes from flying off under gusts of wind, they can be secured using suitable clamps.
We collect the remaining strip of plastic film around the perimeter of the base and press it down with various weights (pieces of reinforcement, bricks, stones, etc.).
This will further strengthen our structure, especially when snow falls, which will further press down the film and, moreover, give the greenhouse and the surrounding land a neat appearance.
