Hello DF, thank you for a very informative response. I have gone back and re-read your earlier notes as well, and have continued research. I have been trying to understand what is needed.
Found some basic sail games of possible interest-
National Geographic (adobe flash req.). 2d game, can adjust the sail and the rudder
http://www.nationalgeographic.com/volvo ... index.htmlVery basic program (I tested on Win 98). adjust rudder only.
http://www.image-ination.com/SimpleSail/from here
http://www.image-ination.com/sailcalc.html (also has technical sailboat data)
After seeing these, it seemed logical that there could be an easier route to a FG sailboat. I thought rather then trying to directly simulate the forces, model the boats speed and direction based on pre-compiled data and 1 user input (like Adlers program seems to). The rudder input, and wind direction, could come from FG, but it would require a table of data based on real or predicted sailboat data. (along the lines of what is shown graphically here
http://scitation.aip.org/journals/doc/P ... _1fig5.jpg (a speed polar diagram)
Which reminded me of the earlier article-
http://scitation.aip.org/journals/doc/P ... 38_1.shtmlThere are simple and complex speed-prediction computer programs.
Such calculations are confirmed experimentally, with a degree of accuracy that depends on the sophistication of the model and on how much the program has been tuned for a specific kind of sailboat.
This lead to looking at Velocity Prediction Program (VPP). programs used for predicting sailboat forces/performance. These have both aerodynamic and hydrodynamic models to compute the forces on the mast and hull. This caused me to question how YASim could compute the resulting force and velocity, if it does not have hydrodynamic model for sailboat hulls.
Theory and background section is good. These two have basic a basic VPP (not GPL though)
http://www.barefootsworld.net/windwalke ... gcalc.htmlanother basic VPP program
http://www.wb-sails.fi/news/SailPowerCa ... tm#ResultsThis has a much longer VPP description.
http://www.sailinganarchy.com/YD/2003/vpp.htmThe VPP consists of input values, some independent variables, the aerodynamic and hydrodynamic models, and the big daddy of them all; the solution subroutine. The program works by adjusting the independent variables until a particular set of equations is solved, balancing the aerodynamic and hydrodynamic forces of a yacht. These equations govern the physics of the sailing yacht, and must be solved together so that the boat sails in a ‘steady’ state.
I found a GPL VPP here, though it is written for Matlab.
http://sourceforge.net/projects/gvpp/With the output data of a VPP, or similar recorded data about a sailboat, perhaps the location of the sailboat could be adjusted directly. In other words, calculate velocity and location just using the rudder orientation and the direction of the wind (and leave other complications for later).