ok i built my incubator and everything is great thinking about putting in a fan but what is the advantage of forced air vs a still air incubator will still work ok
Still air does not circulate the air so the temperature is not distributed. You generally need to run it at a higher temperature - around 100-101 degrees. With a fan, the air is circulated so the eggs get a constant temperature across all of them. With a fan you can keep the temperature at 99-100 degrees. I would put the fan in if you can. Below is a picture of an egg on day 5 that I just took tonight. It is not completely focused, but if you look close you can see the veins on the right by the light. I placed 16 eggs on Saturday, lost one on Monday (cracked) and so far see veining in all but two eggs.