The Routing is set to comfort routing NOT fastest time.
The router is trying to avoid uncomfortable sea state, measured as RMS Roll, Vertical Acceleration and Slamming incidence.
It is trying avoid RMS of 4, Vertical Acceleration 0.2 and Slamming Incidence 50%
So if you want more of a straight route, run a route fastest time or uplight the RMS Roll to 5 and Vertical Acceleration to 0.3 using Advanced Comfort settings.
Comfort Routing explained.
Comfort Routing is based on boat motion modelling, which evaluates RMS roll, vertical acceleration and slamming.
The default comfort thresholds are set to avoid RMS roll greater than 4.0°, avoid vertical acceleration greater than 0.2 g, and avoid slamming incidence greater than 50%. Whilst these recommended default settings may not be comfortable, the router will, where possible, avoid unsafe and very uncomfortable conditions. It is very important that you select the best departure day using the departure planning tool first.
When you request a route, the router will first attempt to calculate a route that stays within these comfort limits. If it cannot complete the route within those parameters, it will automatically rerun the route without comfort limits so you still receive a result.
It is important to set up Wave Polars for your boat so the motion modelling works correctly. In your routing preferences, you should enable Wave Polar and enter your boat dimensions, including the type of boat, displacement, LWL (waterline length), beam and draught. These parameters allow PredictWind to model RMS roll, vertical acceleration and slamming more accurately for your specific vessel.