I agree that hatching by broody is the easiest way, but also as you said they go broody when they please. The biggest advantage I find with the incubator is the one can hatch more eggs, when one wants. I laughed when you said you had enough chickens at 37. I am up to 36 and was done, but wait!!! I have a broody! I'll move her to the broody coop tomorrow (too hot today and that coop is great in the spring, but in direct sunlight all afternoon in the summer). Should be a bit cooler in a few days. I wanted her to hatch in her regular coop, but when I would toss her out for water, she would come back and go into the box with one wooden egg.
So, how many eggs do I place under a large fowl?
Someone put 27 (or allowed that many to collect there) But only 9 hatched. So I would say 9 - 12 would be the max for good hatch rate. However, how many chicks do you really want? I don't want ANY, so I am going to give her 4- 6 and hope for 50% hatch rate. Just a chick or two to break her broodiness....and I'll pray for all roos, so I can EAT them. I really, really don't have space for any more birds. But I bet she could cover 15 with no problem ,she's a BIG girl....but who needs that many chicks this late in the season?
Now if Ray's flaky friend would get her act together and take the 2 hens I promised her, I would have more space.