yeap sure do... you can see one on my byc page. it's being used right now to hatch 6 eggs (started small)
I should know by next friday if it worked as expected.
If you want better hatches go a head and put a fan in it. I have better hatcher since I added a fan. All you need is a computer fan and a cell phone charger.
I have considered putting a fan it but I'm not sure yet. I'm hopefully building it this weekend and I'll be able to set it up and test it out before eggs go in it on the 6th.
Do I just splice the car charger and the fan together?
Be sure that the fan voltage is not lower than the voltage from the wall charger; otherwise the fan motor may burn out. If the charger voltage is lower than the fan voltage, the fan will run slower, but that may be okay. If the charger voltage is lots lower than the fan voltage, the fan may not run at all. Also make sure that both charger and fan are either both AC or both DC. Also, if the charger current out is less than the fan requires, the charger may burn out. Bottom line is that you really should match the voltage and current from the wall wart to the fan you are using.