I am debating hatching our next round of eggs with hens or my homebuilt incubator. The hens make the job easier – I don’t have to turn eggs three times a day. But that takes them out of production and means I lose about 22 eggs per hen that I divert to hatching eggs.
I’ve had very good results with my homebuilt incubator with duck, chicken and guinea eggs. My incubator is a large picnic cooler with a thermostatically controlled light bulb for heat and computer muffin fan for circulation. The bottom two thirds of the cooler is filled with gallon jugs of water for thermal mass and humidity control. I use a min-max thermometer with a humidity indicator. The last part isn’t necessary but fun.
Originally I also had an aquarium air pump introducing fresh air to the cooler but I don’t think it is necessary. When I open and close the cooler three times a day to turn eggs (after each meal) I think it does plenty of air exchange.
I built it out of common parts I had but you can buy the parts (fan, bulb, cord, thermostat for a furnace, etc) at a hardware store. The circuitry is pretty simple and if you are handy with such things you can figure it out. Put the fan to only come on when the bulb comes on to avoid overheating. I have promised someone that at some point I’ll write up plans and schematics – I’m waiting for the figurative rainy day. :) Seems there is never enough time.
The upgrade I would add to it is to make a automatic egg turner. Then I’ll need to add the aquarium pump back. This is on our to-do list for homeschool but may not happen for another year.
The cost is about the same as the commercial small incubators but it is much larger so it does a lot of eggs at a time.
61째F/45째F Light Rain