Finish to finish depency question

[scott.siegler]

I have 3 tasks A, B, and C

Suppose:
Task A begins on Day 1
Task B ends on Day 10

Task C has a duration of 5 days. I want it to have a start to start
dependency with Task A, and a finish to finish dependency + 2 days with
B.

The problem is that Project is scheduling task C to end on Day 12 and
start on Day 7, even though it can potentially start on Day 1. I need
task C to be scheduled on Day 1 because I am going to have another task
with a start to start dependency with task C.

As I am new to Project, I was curious as to how you would model this in
Project to achieve my desired behavior.

Any help would be greatly appreciated.

Scott

 

[Gérard Ducouret]

Hello Scott,
It's not a problem : it's the normal behavior of any planning tool. When a
task (which is not elastic) has several predecessors, it obeys the most
restrictive one. NB : all the links (FS, SS, FF...) are understood "Not
earlier than".
I think that what you are trying to do is a "hammock" task, a task without
any specific duration, an elastic one :
First : you need to create an intermediary milestone between B and C . It's
predecessor : (B id)FF+2d.

Copy the Start date of B
Edit / Paste special / Link on C Start
Copy the Finish date of the milestone
Edit / Paste special / Link on C Finish

Sincerely,

Gérard Ducouret

 

[Haixiang]

It seems that your dependency is arbitrary.
you said " I want it to have a start to start dependency with Task A"
My opinion is the dependency should be as it is in real world.
For example, we can start superstructure only when the substructure is done
(bottom up),so we set FS dependency.
But sometime we do need arbitrary links, mostly for leveling resource usage
some PMs do resource leveling manually rather than by MSP,the way is to set
these arbitrary links.

You'd better learn something about critical path method,a good way is to
calculate (ES,LS,EF,LF,TF,FF...) a small schedule manually. You also need to
learn something about resource. they will give you some ideas what dependency
is

 

[DavidC]

May I ask, are you saying Task C starts at the same time as Task A, BUT
cannot finish until Task B has finished? Alternatively is the logic, Task C
starts at the same time as Task A, and must be finished before the start of
Task D, AND Task B must be finished before the start of Task D? I suspect
the real logic is the later. The question to ask yourself is "When must Task
C finish before which task can start?"