Redmine

I have added some issues to my project and I have established some relations between them. (ie. issue two follows issue 1)
My wish is to set up a starting date for my first issue and the estimated time, and then, I need Redmine to calculate automatically when issue 2 must start, considering:
- starting time of issue 1
- estimated time issue 1 (in hours)
- how many hours we work a day (ie. if my estimated time is 16 hours, but we only work 8h. per day, Redmine should calculate that it will take two days, and then establish starting date for issue 2 as 3rd day of the project)

So far my gant diagram only shows issues with a fixed starting and finishing date...

Am I doing something wrong or Redmine does not have the functionality of what am trying to get?

Thanks for your help!
Sara.