http://solfans.org/blog/races/a-bee-line-to-the-finish/ fans of sailonline.org Fri, 18 Aug 2017 11:09:21 +0000 hourly 1 https://wordpress.org/?v=4.2.34 http://solfans.org/blog/races/a-bee-line-to-the-finish/#comment-20 Thu, 25 Sep 2014 15:09:58 +0000 http://solfans.org/?p=297#comment-20 Hi Solfans,
I approached this problem Javakeda describes as follows.
1/ I downloaded the VBA code for a few Excel UDF’s from a site I found trawling the interweb called Great Circle Navigator by Ed Williams (http://williams.best.vwh.net/index.htm ).
2/ Well before the finish I enter the lat and lon coords of the finish extremities A and B into a standard spreadsheet that I made that uses these UDF’s.
3/ As I round the last mark or get to an on course position where I start to wonder what end of the line should I aim for, I copy and paste bonk’s position and local weather (TWS, TWD) over from Brainaids into this spreadsheet.
4/ The spreadsheet now calc’s the course and distance to each end using Ed’s UDF’s and to any position along the line between A and B.
5/ The spreadsheet also picks up the speed bonk will do along each course from an interpolatable polar BS table as determined by TWA (I know the CCs and I know TWD) and TWS.
6/ BS x distance tells me how long it is going to take. The spreadsheet immediately tells me whether it is quicker to aim for A, B or midline. If say A is best, I then change the midline option to say 0.3 from A and see if this is better again or worse. Etcetera. A few manual iterations and the problem is solved.
7/ But in the Vineyard, I must confess, although with the very short run in to the line there was an ideal opportunity to make this pay, I sailed bonk in SOP, just watching Dingo!

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