I have a home built incubator that I'm rather proud of. I get a 70% hatch rate out of it and have less than $150.00 in it.
I'm making some modifications to it now such as egg turners, electronic thermostat, and a window. all of which I think will improve my hatch rate. I have a web site that has a break down of parts, several detailed photos. I have started adding construction instructions also.
Visit Kirts website for details on his incubator Kick'n Cornish
