Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » Technical Support » wrong VMG

Page: Previous 1 2 3 Next

I use the VMG all the time.

SOL is ocean racing, not harbour racing.

Certainly there are times when VMG is not critical, but on broad reaching it is critical as well as when close hauled beating.

If sailing dead downwind, then you are naturally very slow, and at TWA=180, BS will equal -VMG, but who would ever sail that slow?

At TWA=90, there VMG=0.0 as you are sailing exac6tly across the wind, neither upwind nor downwind.

Try setting your TWA=0.0 and see how fast you can go!


--- Last Edited by Paul Rosser at 2009-04-21 11:01:09 ---
If it breaks, it's not strong enough!
I am curious how you use - VMG when close and broad reaching, can you please explain. Doesn't the polar give you the best course to sail when reaching when the - VMG is just a -ve number that is neither a maximum or a minimum.
That's for sure. Looking at the weather is essential. And that's why SOL would not be mechanical with VMC as a previous poster claimed. But showing the VMC would help to judge losses and gains on detours due to weather.


--- Last Edited by dunbur at 2009-04-21 16:24:48 ---
Great discussion. SOL listens carefully and follows the debait but are not yet convinced to implement vmc. :-) We want to be unambiguous, fair and not too detailed in the info since we want sailor skills to be vital.
...one of the guys behind the game...
Before developing any VMC, I would prefer development of the predicted course indicator to include any DELAYED COMMANDS. Currently the predicted course "bends" when a TWA is being steered, which is a great first step. However once you enter a delayed command, the course predictor indicator becomes useless because it does NOT show that planned change and its effect.

Showing planned changes is very important if tacking or gybing betwwen islands, rounding marks etc.

I would be happy to limit the course prediction indicator to Delayed Commands that exist for the next 6 hours, as per existing course predictor indicator limitation.

This I see as far more useful and important for "ALL" sailors.

VMC will not be used much, but if used, it will be used only by a few. Once you move off a planned course, the old course becomes irrelevant and is of historical and limited use.

Racing Navigation is always about where you are NOW and that "NEW" best course to the next mark. Who cares where you planned to be yesterday? That's gone forever. Your "here" now and what is your next plan? How are you going to get to the next mark faster is all that matters.

Last weeks meals are of little importance if you are hungry today!!!!

The wind is the most important factor, follows by planned course. Thus boat speed and VMG to the "wind" is MOST critical.

--- Last Edited by Paul Rosser at 2009-04-21 20:22:40 ---
If it breaks, it's not strong enough!
I hear you Paul and add the request to the list.
...one of the guys behind the game...
I am curious how you use - VMG when close and broad reaching, can you please explain. Doesn't the polar give you the best course to sail when reaching when the - VMG is just a -ve number that is neither a maximum or a minimum.
REPLY:
The polar is a great diagram but it is hard to be accurate, given the small scale, when trying to read off resultant speed prediction.

Press the "wheel" icon and as you move the course, the polar diagram shows the Boat Speed and VMG to 2 decimal places, far more accurately.

I am quite happy to beat you by sailing x.01knots faster, as long as I'm faster!!LOL (My current leaderboard position is not necessarily my planned one!! LOL)

When reaching, Boat Speed and VMGs are a trade off, with VMG becomming progressively less important as TWA approaches 90 degrees. Therefore where VMG is maximised is generally at about 45 degrees upwind and 135 degrees downwind. BUT, and it is always a big "BUT", this does not apply in all wind strengths and IRL with different wave patterns. VMG to windward maximises between 30 to 50+ degrees dependant upon wind stength and boat design, weight and trim. In SOL waves, weight and trim are not factored in.

Planning a course needs to consider both bearing and VMG speed. Hence gybing down wind to maintain "hot" (faster) angles is very important e.g. Americas Cup or any match racing shows this up critically. 2nd is still "LAST". Fleet racing clouds the effect a lot as you may be trying to cover several boats at once. It's all down to trigometry and how accurate your wind forecast and hence boat speed forecast on the other leg will be.

When to tack or gybe or adjust course, especially with wind shifts, is what is the difference between 1st and ALL other positions.

--- Last Edited by Paul Rosser at 2009-04-21 20:54:49 ---
If it breaks, it's not strong enough!
Before developing any VMC, I would prefer development of the predicted course indicator to include any DELAYED COMMANDS.
Oh yes, I second that. I also would wish for the course predictor to extend to e.g. 12 hrs rather than six. But I would give the inclusion of delayed commands higher priority. Then an extension of the course predictor and last but not least I would rather have VMC than VMG.
HI Paul, great discussion going on here.

I like he idea of including the delayed commands in the course predictor. But this might give people the impression that its fail safe. Then the course predictor plots out their exact course and they start thinking less about the course. (not the veterans of course).

I think this is the same by extending the course prediction to 12h, now its a clear indicator of the 6h blocks the weather comes in. Showing more might lead to the illusion that the course shown will always be true.

--- Last Edited by Jeroen Tiel at 2009-04-22 06:52:11 ---
I provide feedback and am admin of Sailonline.
hometown: Groningen, The Netherlands
If the courses are all "COMPASS" courses, then the predictor is very accurate and the margin of error is indeed small.

If "any" of the commnads (current or delayed) are TWA based, then with wind shifts, increases and decreases the accuracy of prediction decreases.

In that case a wavy line (lke a current arrow on a chart) should be used to indicate a widening course of probability with the hourly circles getting larger in area. Perhaps a widening arrow but this could obscure some boats. So a wavy line that widens further out will show greater uncertainity of future course.

So with combinations of CC & TWA delayed commands, the course predictor could have a most interesting look. Would you like a diagram example?


However with most SOL Racing, it is very rare to have lots of different commands with many tacks and gybes within any 6 hour period. Certainly I have used many commands (say up to 10 if one is using Sail Planner) but these DC's are generally minor course alterations on the same basic course / tack. Just minor and slow increments in changing the TWA to suit a weather front or major wind shift as it passed by. Three or four DC's if sailing between islands.

--- Last Edited by Paul Rosser at 2009-04-22 10:27:07 ---
If it breaks, it's not strong enough!

Page: Previous 1 2 3 Next

Please login to post a reply.

Races

Next Race: 00d 00h 00m


Current Races:

Garagiste's Test Lab

Welcome to Newport, RI, one of the great sailing centers of the world. This TIMED race takes us around Nantucket Island in RC 44s to celebrate the life of Capt. Bartholomew Gosnold who, among many other things in his short life, named Cape Cod for the teeming fish he encountered there, and Martha’s Vineyard for his daughter. This is a TIMEDrace so you may RE-REGISTER HEREto try again after finishing a run. You will have 13 days and 11 hours to test your skill and decision making after the race opens.
Race #1939
INFOby brainaid.de
RC 44 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ3 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
23 August at 23:00 UTC
Race starts: Aug 10th 12:00 Registration will open soon
▶ Flash
GO TO RACE

Patricks Test

Welcome back to race two of the SSANZ Triple Series—it's time for the Lewmar 100! Our dynamic fleet of Young 88s returns for another exhilarating 64 nautical mile battle across the stunning waters off Auckland, New Zealand. Once again, our skilled Sailonline racers will test their strategic minds and endurance against seasoned sailors from the Young 88 Association. With intense competition, shifting conditions, and plenty of tactical decision-making, this race promises high-energy sailing and edge-of-your-seat excitement from start to finish!
Race #1933
INFO by brainaid.de
Young 88 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SSANZ - SYC
Race starts: Aug 03rd 08:00 Registration Open!
▶ Flash
GO TO RACE

Joanne's Test Race Zone

In 1947, Hugh McLean & Sons of Gourock, Scotland built a radical racing yacht for John Illingworth, soon-to-be Commodore of the RORC, to a design by Laurent Giles. With a masthead rig, giving her ‘free’ sail area per the rules of the time, and short overhangs reducing pitching, Myth of Malham went on to win The Fastnet that year and again in 1949, and to compete in numerous Admiral's Cups. In 1958, in honour of the yacht, the Myth of Malham race was conceived - a mini-Fastnet to the first lighthouse on a rock west of Cowes, Eddystone, rather than the second, to be held in non-Fastnet years. IRL this year it has been raced already, but this stops us not from “Red Eye” racing its online 230nm in Fareast 31Rs, leaving how to deal with the Isle of Wight open to your own discretion.
Race #1847
INFOby brainaid.de
Fareast 31R PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - RED
Race starts: Jul 25th 12:00 Registration Closed
▶ Flash
GO TO RACE

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 😊.
Race #1935
INFO from brainaid.de
Riptide 50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ3 - ARCH - SUPSOL – SYC
Race starts: Jul 21st 17:00 Registration Open!
▶ Flash
GO TO RACE

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
INFO by brainaid.de
29er_XX PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SPRQ3 - SPRCH - SUPSOL – SYC
Race starts: Jul 19th 15:00 Registration Closed
▶ Flash
GO TO RACE

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
INFOby brainaid.de
60ft Trimaran PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - ABS
Race starts: Jun 03rd 11:30 Registration Open!
▶ Flash
GO TO RACE

Gulf of St Lawrence - test - Mirek
-
Race starts: Apr 21st 17:00 Registration Open!

▶ Flash
GO TO RACE

Stefan's Duck Pond

 Get ready for an exhilarating new challenge as we set sail on the eighth leg of the 2025 Ocean Championship Series! This leg takes us from Cape Town South Africa to the bay of Belbuhan on the south West coast of Java - a 5100 nm journey of endurance, strategy, and pure sailing adrenaline. This leg will be raced aboard the 125 ft Orange catamaran, pushing sailors to their limits as they navigate the open ocean. Do you have what it takes to conquer the Indian Ocean? Join us and put your skills to the ultimate test!
PRIZE: SMPF
Race #1900
INFO by brainaid.de
Orange 125 PARTICULARS    
WX Updates:
0430 / 1030 / 1630 / 2230    
Ranking: OCQ3 - OCCH - SUPSOL - SYC
Race starts: Feb 06th 00:00 Registration Closed
▶ Flash
GO TO RACE

Trapped Camel
-
Race starts: Aug 21st 15:03 Registration Open!

▶ Flash
GO TO RACE

Caravanserai
-
Race starts: Aug 08th 17:00 Registration Open!

▶ Flash
GO TO RACE

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
INFO by brainaid.de
First 47.7 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Aug 03rd 08:00 Registration Open!
▶ Flash
GO TO RACE

Mirek's Mess & Canteen
music deleted
Race starts: Apr 26th 18:00 Registration Closed

▶ Flash
GO TO RACE

Antarctica 1 of 3
-
Race starts: Jan 27th 21:57 Registration Open!

▶ Flash
GO TO RACE

Flinders Island TIMED Race 2024

In the southern reaches of the Bass Strait between mainland Australia and Tasmania, you will find the Furneaux Group of islands, largest of which is Flinders, both named after famed British navigators. Your mission, should you choose to accept it, is to race your Ocean 50 catamaran a course of c 106nm around Flinders in the fastest time. This is a TIMED race, so you may RE-REGISTER HERE to try again, after finishing a run. This course will self-destruct in 13 days and 11 hours after opening for entrants.
Race #1776
INFO by brainaid.de
Ocean 50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ1 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
27 January at 23:00 UTC
Race starts: Jan 14th 12:00 Registration Open!
▶ Flash
GO TO RACE

Tasman Double 2023 - Hobart to Sydney
music deleted
Race starts: Jan 02nd 02:00 Registration Open!

▶ Flash
GO TO RACE

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
INFOby brainaid.de
Super Maxi 100 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
OCQ3-OCCH-SUPSOL-SYC
Race starts: Sep 01st 04:00 Registration Closed

▶ Flash
GO TO RACE

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.
RE-REGISTER HERE to race again after finishing a run
Race #1700
INFO by brainaid.de
R/P 66 PARTICULARS
NAM_AWIP WX Updates:
0245 / 0845 / 1445 / 2045
Ranking:
TRQ3 - TRCH - SUPSOL - SYC
RACE CLOSE: Sunday, 18 August at 23:00 UTC
Race starts: Aug 05th 12:00 Registration Closed

▶ Flash
GO TO RACE

ZONA DE PRUEBA DE MANUEL

Welcome to the Shorthanded Sailing Association of New Zealand's 2022 Evolution Sails Northern Triangle series, which, unfortunately, to comply with latest NZ government COVID restrictions, has been reduced to a duo, commencing with this short prologue of approximately 35nm on the waters of Auckland's Hauraki Gulf. As so often with SSANZ events in the past, online we will be racing the event in ever-young Young 88 one-designs. Have fun!
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
INFOby brainaid.de
Young 88 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - NTR
Race starts: Jan 10th 14:00 Registration Closed
▶ Flash
GO TO RACE

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
INFOby brainaid.de
Delphia 47 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Mar 05th 17:00 Registration Open!

▶ Flash
GO TO RACE

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.
RE-REGISTER HERE to race again after finishing a run.
Race #1444
INFO by brainaid.de
Club Swan 50 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
RANKING:
TRQ1 - TRCH - SUPSOL - SYC
RACE CLOSE: Sunday, 28 February at 23:00 UTC
Race starts: Feb 15th 12:00 Registration Closed

▶ Flash
GO TO RACE

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
INFOby brainaid.de
X-362 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SYC
ALT. CLIENT:Classic

Race starts: Dec 21st 16:00 Registration Open!

▶ Flash
GO TO RACE

Antarctica 3 of 3
-
Race starts: Sep 16th 11:13 Registration Closed

▶ Flash
GO TO RACE

BLANK POLAR
Race starts: Feb 16th 00:00 Registration Open!

▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member kenza
  2. Sailonline Yacht Club Member bonknhoot
  3. Sailonline Yacht Club Member rumskib
  4. Sailonline Yacht Club Member zero
  5. Sailonline Yacht Club Member WINSTON_4
  6. Sailonline Yacht Club Member rafa
  7. Sailonline Yacht Club Member longreacher
  8. Sailonline Yacht Club Member Henrys
  9. Sailonline Yacht Club Member Smo
  10. Sailonline Yacht Club Member Neuroman

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client