When you look into the optimal route results you will see those 'too close' tack angles between brackets. Here you need to tack your way up or gybe down. 
Not sure when Exp will actually show the tacks and gybes in the course and in which cases you have to find out by seeing these numbers between brackets.   Maybe Exp only shows the tacks/gybes visually on the optimal course in case there is a tactical preference for which side to go first?   Hopefully someone else can chime in here.

Last edited by ZeeZee (2/11/2017 12:12 pm)

That's correct Ernie.    Would be interested to get the understanding when they are shown and when not (assuming the prefer tacks & gybes checkbox is checked).
I wasn't aware there is possibly a difference in the grib and iso based routing regarding this issue.  But I just ran some tests and indeed the 'numbers between brackets' seem to happen more in the grib routing (based on my not very representative quick tests.. ;-)

OK - am I understanding this correctly?  The numbers in parentheses indicate that I need to tack or gybe to sail that segment of the route - so I am sailing either left or right of the optimal based on my VMG - What i am missing are the time to sail that segment and the distance sailed based on the line shown by Optimal - or are they based on the boat polars for what the boat can actually sail?  I tried editing my polars to show zero BSP below 40 TWA, but it was still showing a routing with low TWAs - even though my BSP should have been 0 at the TWAs shown,  i had motoring turned off and set to 0 to make sure it wasn't having me motor.

I am trying to run routes for the upcoming RORC 600.  I could only use the Grib option for the entire route - which gave me the low TWAs.  When i broke it down into smaller segments i was able to run isochronal which gave me a more realistic answer and let me place race notes to avoid land.  From the start round green island up to the first mark off Barbuda the isochronal showed a long tack to the SE, and then another long tack up to Green Island - which is reasonable (but not what i would actually do because of waves and current effects around the island), but the grib model had the issue of low TWAs.  The isochronal model had a distance of 49.2 miles for a 41 mile course, whereas the grib model had a distance of 43 miles and about 40 minutes faster - it was showing a couple of tacks from TWA -20 to +37 then to +21 then to +5 .  The entire difference is in the first leg into the wind up to green island.  I have prefer tacks and gybes at marks selected in configuration.  Am I missing something - or doing something wrong?