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Posted by AGage  |
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Well, VMC = Velocity Made to Course recognising that course legs arent always directly up or down wind. IRL we all use this concept downwind when there is a local shift just prior: Sail the gybe that takes us closest to the mark. Or either upwind or downwind to tack on the headers (lifts downwind): coz VMC is decreased and increased on other tack/gybe. So VMC is the component of your current velocity (being a vector with magnitude and direction) in the direction of you next most immediate waypoint/mark on your course, VMG is with respect to the wind direction. So, no it doesnt assume one is on a direct course, great circle or otherwise, to the next waypoint, but rather uses that direct course instead of the wind direction. In a windward/leeward course set exactly to the wind VMC = VMG. If a shift has occured and you are on the favoured tack/gybe then VMC > VMG, converely on the unfavoured tack/gybe VMC < VMG. If you can, say, reach directly to the next waypoint/mark then VMC = BS. And in the case where that firection is 90 degrees to the wind, VMG = 0. Say the TWD is 0, but the heading to the mark is at 15. You're heading at 40degrees doing 10kn. Then VMG = cos(40-0) * 10 = 7.66kn, and VMC = cos(40-15) * 10 = 9.06kn. Now say we footed off 5 degrees and our BS increased to 10.6kn. our VMG is now cos(45-0) * 10.6 = 7.49kn, our VMC is cos(45-15) * 10.6 = 9.18kn. So our VMG has decreased, but VMC has increased by footing off for more speed. And to illustrate what you said about sailing directly to the next mark not always being optimal, imagine the heading to next mark IS 40 degrees above. Sailing directly toward it, VMC = BS = 10kn (cos(0)=1). By footing to 45@10.6kn our VMC is cos(45-40) * 10.6 = 10.55kn, so we will get there faster heading 45, even though over a 30nm leg we will sail an extra 1nm approximately (the cosine(angle) function automatically accounts for extra distance, but assumes no manouvering penalty). So given performance penalaties for for tacks/gybes, the longer the leg the more the benefit will be, and if the leg is short enough you WILL still get there quicker going straight for it. This is my understanding of the term VMC, again maybe I am missing something, then pls inform me of it. Of course, on really long legs a straight line on the mercator map will not be the shortest distance no, but you can still calculate a fastest heading, convert it to a great circle heading, and slowly follow the circle. And of course you can always pick an arbitrary point to calculate VMC to, like if you need to round a headland before you get to a waypoint, then use that instead. C can stand for any chosen course, but we usually like to sail the course set by the RC, so it is usually that which we choose to use (or deviations due to obstructions). Yes, High performance dingies, some cats, and performance yachts will now always reach the leeward mark faster by tacking downwind. That is simply the concept of VMG put to practical use downwind (if vmg > at an angle off 180) And that is such a good thing! I hated the 'processional runs' in the Junior classes I sailed. Downwind is now the leg generally least understood, which can provide good opportunities for gains, but equally for losses. I dont think I have yet seen a boat on SOL that doesnt benefit from tacking downwind... IRL main trouble is determining the best angle downwind... We have developed excellent methods to do this upwind, but not down... Its easy when you have a nice polar and that is the only thing that contributes to performance... Add in to that handling, trim, wave surfing etc etc and its quickly gets very complicated. Not to mention some boats like the ones I sail, benefit more if you dont sail ANY straight line, but a snake course, up first to increase the apparent windspeed and swing it more toward the beam (even the bow), then head down to decrease distance sailed... Headache time! 
High performance skiffs (18s, 49er etc) effectively never sail downwind, as the apparent wind is always coming from the bow, and this impacts handling and trim enormously... Gettin too far off topic here, maybe we should start a 'Sailing Terms' Thread? I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__ |
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Posted by ernissss  |
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Excellent explanation, think no new thread needed.
Ernestas ernissss LT |
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Posted by Jawz  |
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Please guys do something about the zooming issue. Not being a routing sailor I rely on accuracy and shortness of course to keep my efficiency high. With this new system I cannot get this right at all. In my humble opinion this feature has taken us a step backwards and not improved the game engine at all. Lets take a step backwards and rebuild please!
Thanks George |
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Posted by jakob  |
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Hi. What zooming issue? ...one of the guys behind the game... |
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Posted by AGage |
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Jakob, there is an issue with the steering tool line, where it changes the length of the line shown on screen, depending on the zoom level. Some have commented that at maximum zoom it disapperas completely, but I have not personally seen this particular issue, only that it gets shorter with more zoom... I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__ |
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Posted by jakob |
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Can I get some screenshots of that please. I cannot reproduce... jakob@sailport.se ...one of the guys behind the game... |
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Posted by jakob |
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Can I get some screenshots of that please. I cannot reproduce... jakob@sailport.se ...one of the guys behind the game... |
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Posted by Schakel  |
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Note where the cursor is and where the line ends.
Schakel |
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Posted by jakob |
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Ahh, now I understand. Thanks!! ...one of the guys behind the game... |
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Posted by LiquidMotion |
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Hi - Thanks for all the hard work.
I was wondering if it would be possible to overlay 'real terrain', something like Raymarine does on the chart plotter. Or incorporate Google maps. Just a thought. Dan. aka LiquidMotion |
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Marstrand to Cowes 2025
We invite you to another race, which will kick off the third quarter of our ARCH series. We'll set off from Marstrand, Sweden, which, along with Skagen, Denmark, marks the line commonly recognised as the border separating the Baltic Sea from the North Sea. The 650nm route will take our Ripitide 50 across the North Sea and the English Channel to Cowes, England. Watch out for the fast ferries crossing the Channel from Calais to Dover 😊.
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Nantucket Sprint 2025
Welcome to Nantucket, from whence Herman Melville’s Cap’n Ahab sailed round The Horn into the northern Pacific Ocean to hunt the gray whale - whose migrations are celebrated elsewhere in SOL’s Q4 schedule - he never to return. And whaling too, as the 19th C progressed, like Ahab disappeared from Nantucket as the harbour silted up and mainland Massachusetts whaling stations benefited from rail connections. But beach life, yachting and nostalgia has rescued the island from oblivion, so to celebrate leisure, SOL gives you the Nantucket Sprint - 25nm in 29er_XX’s from east of Tuckernuck Island across the sound to a finish just inside the mouth of the harbour. Enjoy!
Race 1936
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Puil's Practice Palaver
Nearly there; only 2500nm to go, round the Horn and up the Red Sea to Suez into what will more than likely be more headwinds for this sixth leg of our African circumnavigation, to be followed in September by a final sneaky dash up the canal back to where we started all those months ago. We’ll be sailing a not entirely appropriate-for-upwind-work 60ft Trimaran!
Race #1859
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Gulf of St Lawrence - test - Mirek
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Stefan's Duck Pond
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Race #1900
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Trapped Camel
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Caravanserai
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Patrick's Playpen
Welcome to the legendary "Westcoaster," a race that has tested sailors for over 50 years. Spanning 435 nautical miles, this iconic journey takes racers from Melbourne, across the formidable Bass Strait, and around Tasmania's rugged west coast to the finish line in Hobart. Organized by the Ocean Racing Club of Victoria, the Westcoaster is renowned for its challenging conditions and adventurous spirit. This year, our SOLers will tackle the course in the swift and capable First 47.7, a yacht launched by Beneteau in 2000, built for speed and endurance in long ocean races. Get ready for an exhilarating ride in one of Australia’s most celebrated yacht races!
Race #1841
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Mirek's Mess & Canteen
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Antarctica 1 of 3
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Flinders Island TIMED Race 2024
Race #1776
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Tasman Double 2023 - Hobart to Sydney
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Race starts: Jan 02nd 02:00
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John's Test Zone
It's time to test your ocean racing skills in a variety of weathers as we head the 6400 NM between Hong Kong and Auckland in a fast Super Maxi 100. We'll be heading from a northern summer to a southern winter so keep plenty of cold weather gear and warm rum on board!
PRIZE: SMPF
Race #1597
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calm's Practice Race
Last raced in 2021, we return to Boston for another race to Newport. And just like in 2021, the chosen boat is once again the speedy R/P 66. This is a TIMED race so pick your winds wisely and see how quickly you can complete this 132nm run! For reference, the winning time in 2021 was 6:12:28.
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Race #1700
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ZONA DE PRUEBA DE MANUEL
Please note the displayed course is provisional; the actual course will be set after the IRL course is announced at the skipper's briefing 48 hours before the start, and no later than 24 hours before the start.
Race #1561
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San Sebastian to La Rochelle 2021
Once again, our SOL race will be shared with a group of Polish sailors, representing one of the stages of their Virtual Training Cruise around Europe. 171 nm in Delphia 47s across the not always calm Bay of Biscay from San Sebastian to La Rochelle will undoubtedly be one to test their skills. Welcome/Witajcie and we wish you all fair winds.
Race #1441
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Aland Sea TIMED Race
Norrtalje Segelsallskap, 70km NE of Stockholm was founded in 1920, and time was when the society’s season opened with a challenging offshore race from the club line off Flaten island at the mouth of the long and narrow Norrtaljeviken, out onto a triangular course around the Aland Sea, to finish at Simpnas slightly to the north on Bjorko island - some 78nm in total. A fine race that SOL, being from these parts, ran annually up until 2013. Last run in autumn 2018, we return here to race the course again in the form a TIMED RUN in spanking new Club Swan 50s.
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Race #1444
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Bimmer's Test Zone
What about a speedy X-362 380nm race in the waters off S America, just to blow cobwebs away!!
Race #1415
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Antarctica 3 of 3
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BLANK POLAR
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