Expedition Navigation Software 
1 of 1- crc1965
- Expert
Offline - Registered: 5/20/2016
- Posts: 14
Polar Development and impact leeway on VMG
I am tweaking my polars. Especially upwind in heavy air 20+ knots shorthanded I don't make anywhere near the model data.
I use strip chart to record data.....but I end up with TWA and BSP. If I enter this into Expedition Polar it will calculate a VMG for me which doesn't take into account the fairly large leeway (light boat, feathering, significant sea state). Strip chart has recorded VMG; can I use that instead of having expedition do the calculation?
Thanks,
C
- ZeeZee
- Expert
Offline
- Registered: 3/30/2016
- Posts: 321
Re: Polar Development and impact leeway on VMG
The TWA as recorded in Expedition does already include leeway. Therefore your calculated VMG is also including leeway..
Of course you need to make sure your instruments supply leeway to Expedition or you should have Expedition calculate your leeway based on heel and BSP (assuming your instruments deliver heel data).
The TWA as e.g. shown on an ORC Certificate also includes leeway, so that makes the polar data (and data shown in number boxes) from Expedition directly comparable to these ORC polars.