They are actually a lot more than pens as they provide for all the needs of the chickens while they are on the mandala beds. The cover over the domes provides their shelter and hides their roost where the chickens spend the night. We will talk more about the chickens and caring for them at another time.
In her book The Permaculture Home Garden, Linda Woodrow sets out a design for the domes, using six meter lengths of (I think) 20 mm high pressure PVC pipe. I have used electrical conduit at 4 meter lengths, as it is more available and cheaper but the domes do suffer from the lessened strength of the conduit. We have overcome this shortfall as I will explain later, but this too comes at a cost in extra materials. Conclusion? Draw your own! But wait till the end of the page.
|Feeder. waterer and nest box ( grass catcher).|
The base of the dome is approximately four meters in diameter. Pi x diameter = 3.141 x 4 = 12.564. We have used three 4 meter lengths to make the circumference of the bottom circle 12 meters - which is what you get using two x 6 meter lengths too.
The circumference of the other two circles according to Linda's book are 10.6 and 7.4 meters although I have found that the "step -in" can be quite high if you are a short person and adjustment need to be made to the circumference to fit it closer to or further from the ground level on the finished product.
|Installing the roost.|
The arches are made from one and a half lengths of conduit to make a six meter length. These join in their middle at the top of the dome and the ends are attached to the base and two other circles equidistant.
I originally attached the tubes using 5/32 screws and nuts but have found that fencing wire lasts much longer and works well. I also notched the circles were they met with the arches and glued them for added strength but found the weakening of the tube was not worth the extra strength of the joint.
Cheap wire netting is best as it is more flexible and lighter. Have as few joins as possible as they seem to damage the tarp cover with sharp edges. I have found that starting along an arch and doing each side with pleating more than cutting and joining, works best.
We used cheap poly tarps from the "chinese" hardware shop for a while but they broke up and we had pieces of blue tarp all over the garden after a wind. We went to a better quality and more expensive tarp and they seem much better value in the long run and much kinder to the environment.
These we tied to the embedded wore as shown previously though as the wire has started to rot at ground level we are looking at other ways and pegging is now necessary.
The failure in the design comes in windy areas as the strength of the dome is tested by a strong sideways beeeze. This can cause the dome to collapse on itself and break the conduit.
I have overcome this by fitting a solid roost made with 25 x 10 mm pine and fitting a prop under this roost to give extra strength in strong winds. The prop stops the sides from collapsing inwards and avoids damage to the dome.
This has been very effective although after six years and because of damage before the modifications, the domes are now ready for replacement. I have started work on some geodesic domes to replace not only the chook pens but also serve as poly domes for extending the season into the colder months of the year.