I don't really know. I have no personal information about bobtail, and the information I can find about it is inconsistent.
According to what
@nicalandia said earlier in this thread, I would expect your cross to give black chicks in both genders.
But there's an article I found on the internet that describes bobtail as acting sex-linked:
https://www.cochinsint.com/uploads/8/8/2/1/8821267/ci_-_bobtail_cochins.pdf
If that one is correct, you might get black sons and daughters that are bobtails or that have some bobtail traits.
I really don't know which is right.
If you try it, please post photos so we can all learn from them