(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?
(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.
Here's a look at the primary ways to shorten the critical path of a project http://ow.ly/TL6Ox
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To each his own, I suppose, but the example of trench digging and pipe laying is exactly what we use in our training course to demonstrate how and why to avoid using any predecessor links except Finish - start with 0 lag.
There are FS, FF, SS, SF links and each can have positive lag, zero lag and negative lag, so there are 4 x 3 possible combinations, and out of those 12, 11 are not necessary, and especially avoid the four with negative lag.
With the trench and pipe, it is not the elapse of a certain amount of time after digging starts that allows laying to start. It is the existence of a certain distance of trench.
Trench digging should be two tasks, trench A and trench B, and pipe laying should be two parts pipe A and pipe B, where trench A is FS0 predecessor of both trench B and pipe A, and trench B is FS0 predecessor of pipe B.
If tempted to use anything other than FS0, probably the tasks need to be broken down into a finer level of detail.
The link above is very simplistic and forgets that to overlap activities needs extra resources to allow work on both at once. For a more comprehensive discussion see: http://www.mosaicprojects.com.au/WhitePapers/WP1059_Schedule_Compression.pdf
And always remember, it is far easier to play around in the software to make a schedule look OK than it is to change the way work is undertaken in the real world of the project.
Email: PPadmin@planningplanet.com
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