The rocket stoves were built on a base that was about 12″ in height that was constructed out of rock and termite mound clay. The base was build a few days before the class to allow the mud to set and for the cracks to be repaired. Although the base is not a necessary element to the stove, it was designed in to raise the height of the burners for ease of use.
The base for these two stoves was extended quite a ways at the front. This is to accommodate the length of wood commonly used at the centre. The extended base will allow for the wood to remain flat while being fed into the burn chamber.
Each of these two stoves has a slightly different design. The one on the left has a side entry primary air intake and the one on the right has the primary air intake located below the tile, directly under the wood burning chamber. These two different designs were used to demonstrate alternative options in construction. Benjamin has implemented both designs in Uganda and has received differing opinions on which design is better.
He decided to demonstrate both models so the kitchen could test them and decide for themselves. When selecting the tile or metal for the model on the right it’s important to choose a size that will be covered at the side by clay in the final design. The shelf, which separates the burn chamber from the air intake has to be secure, but additionally it cannot extend outside of the clay, or cracking will occur from the excessive heat fluctuation from the inside to the outside of the stove.
The stoves themselves will be constructed out of cob, which was a mixture of termite mound clay, water and straw. The forms for for the burn chamber and air intakes were a combination of reed bundles and banana stems. Once the stoves are fully dried, in about 2 weeks the forms holding the stoves shape will be removed.
Benjamin demonstrating the difficulty of lifting full pots from ground level and the importance of building a stove to the correct height.
As an important side note, the diameter of the bundles used to build the forms is directly related to the diameter of the pot that will be used for cooking. The bundles need to be about 1/3 the diameter of the base of the cooking pot.
The next step was to start mixing the cob, which in the 30+ degree heat was a very welcome activity for everyone, including the dogs.
A spa treatment for sure!
The mixed cob was then applied around the forms as compact as possible. The name of the game is to throw the cob in with a strong arm to remove any air pockets that can contribute to cracking in the ovens as the cob dries.
Throwing and pounding to release the air from the cobb as it is applied to the forms.
Located about two-thirds the way up the burn chamber the secondary air intake form is added. This increases efficiency creating a secondary burn, the most important element in reducing the harmful smoke generated when burning wood.
The secondary air intakes are built using banana stems creating a passage located at the side of the vertical burn chamber and they are angled slightly upwards.
Once the air intakes are installed and the cobb has been applied level with the reed forms, the pots are rested on top to complete the burner section of the stove. The cobb is molded around the pot to create a basin that will direct heat to where it is needed, increasing the efficiency for cooking.
Once the pot has been surrounded to a depth of two thirds the pot is removed and 1″ spirals are carved out to hold the pot and allow for heat and air circulation.
Then it was time to smooth out the cobb and decorate!