So I built my wife a forced-air incubator. I originally built it so that the fan was continuous but the fan kept blowing on the heating element and it actually raised the temperature after the heater turned off. I then set it so that the fan turned off when the heating element turned off. The heating element is a 100W PTC heater attached to a large aluminum heat sink with fins. The fan is a 120mm computer fan. I calibrated the thermometers and the temps read 100F when level with the egg. The controller shuts off at 100F. Is this okay? My other option was adding a small 80mm fan that circulates the air continuously but located at the opposite side of the incubator. Another consideration that I might play with is turning the main fan to a lower voltage (maybe 5V) continuously. Anyone else have suggestions? This is our second batch of eggs. The last batch on day 6 didn't have veining EXCEPT for one with some red veins. My wife opened them up after not seeing anything when candling them. We were also thinking maybe they were improperly stored or too old (some of them sat for 7 days). We also thought it might be the temperature because we set it at 99F. We tried a second batch of eggs 12 eggs with the oldest being 24 hours and the youngest being a couple of minutes. She candled them today and said she didn't see any development. She's going to wait until day 10 before making the call. These were set at 100F. Now my thinking is that maybe the eggs are experiencing wild temperature fluctuations due to the fact that the air isn't being continuously circulated. In this situation, maybe we should set the temperature for 102F at the top of the eggs? Any thoughts?