Building incubator, Fan or no Fan? that is the question

[cowgirlqt96]

I am building an incubator with my son so we can get a better experience with our chickens. I have seen many different homemade incubators and some have fans some dont. Which should I choose to do, Fan or no fan? plz help

 

[Yiannisk]

With a fan you have better air distribution and uniform temperature imo