OK, let's talk VMG wind vs WCV. Both are the result of a vector addition. Most GPS units show WCV as VMG. Think of it as VMG waypoint or VMG GPS.
VMG wind is velocity made good directly upwind or directly downwind. This is useful for racers on windward/leeward race courses. VMG wind requires wind and boat speed through water inputs. It is independent of GPS data. You must have a good sailing instrument system to see VMG wind. WCV is waypoint closure velocity. It is the velocity at which you are approaching the GPS waypoint. It's nice for cruising and point to point races but less useful for W/L races. The issue with WCV or GPS VMG is that, as you approach the layline, WCV tends to zero since you are sailing 90 degrees to your direct course to the mark. So it works good at the start of the leg but tends to fail at the end of the leg. It also requires you to reset the mark (waypoint) after each rounding. However, there is a way to use GPS based VMG for W/L races. Once the course is announced by the race committee, proceed to the center of the start line and set a waypoint 20-50 miles directly up the course. Setting a mark a long ways away will minimize the inaccuracy as you approach the upwind mark, I.e. layline. It will also work on the downwind leg but your VMG GPS might show as a negative number. Dennis C. Touche' 35-1 #83 Mandeville, LA On Oct 31, 2016 2:01 PM, "Charlie Nelson via CnC-List" < [email protected]> wrote: Hey all; Although I have VMG (or at least its approximate equivalent) available from my Garmin 746 Chart plotter and can display it on one of my 4 Garmin displays above the companionway, I find it difficult to see it with crew in the cockpit and I don't like putting my head into the boat looking down at the chart-plotter mounted above the binnacle while I am trying my best to go hard on the wind. OK-OK--I know this hardly qualifies as a serious problem!! Nonetheless, I am looking for the simplest solution that allows me to see the VMG either on my iphone (hard to read with sunglasses on), or a 'smart watch' which may have the same problem. I realize I could use another battery powered GPS but I would need to mount it and operate it while trying to get my head in to the race at the same time. Ideally glasses with a heads-up display of it would have it in front of me no matter what else was going on. Any listers have solutions or ideas? My simpleminded thought is to put the RC or starting line in as a MOB mark and then use either the largest negative VMG upwind from it to guide me at the helm and the largest positive VMG downwind from it find the best AWA. This would likely give me the best course to steer no matter how true the course is to windward. Thanks, Charlie Nelson Water Phantom C&C 36 XL/kcb 1995 [email protected] _______________________________________________ This list is supported by the generous donations of our members. If you wish to make a contribution to offset our costs, please go to: https://www.paypal.me/stumurray All Contributions are greatly appreciated!
_______________________________________________ This list is supported by the generous donations of our members. If you wish to make a contribution to offset our costs, please go to: https://www.paypal.me/stumurray All Contributions are greatly appreciated!
