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 » Sailonline Yacht Club » VMC or "by the numbers" in oscillating winds

Page: Previous 1 2

Posted by
AGage


Users avatar

Posts
411
Registered at
2008-12-27 10:31:57
2011-04-11 07:43:01 - Re: VMC or "by the numbers" in oscillating winds
Try these webpages Tom, it is about a technique you describe known as 'wallying the windshifts':
http://www.ockam.com/vmc.html
and
http://wcsailing.blogspot.com/ - near the bottom for this specific issue, but there is also more good stuff....

If you are required to sail the non-favoured tack (ie land forces you to), then you often want to sail higher than VMG - by how much is the magic question, and I cant really give you any general answers. One good way to get a feel though is experimenting with the predictor line.
Set your boat at the max VMG angle, and get to 100% performance. Then point up by 1 degree. After you click 'Send' place the crosshair over the point for 1 hour, and hold it there. When the new course is established and the predictor redraws itself, compare the new 1hr point to the old. For simplicity say you are trying to maximise your course N, and are on Port so want to minimise your Eastward travel (which is further from rhumbline). Well what you want to compare here is the 2 points' latitudes. If the new point is no further S than the original vmg point, then 1 degree higher is better. Now do it again...
Eventually you will find pointing higher slows you too much.
Also using the ruler to record the various points is a good idea, and zoom in so you are measuring as accurately as possible. Also be aware that as you are actually moving N, the points will tend to be more N anyway each time, so factor this in if possible.
And of course you can also do the exact same thing pointing progressively lower than vmg angle, to see visually how sailing a bit faster (but also remember as 76T points out - also further)...

Also download my polar butterfly overlay and experiment using some card as 76T suggest, or a tool I also mention on the blog: MB-Ruler for drawing and moving lines on the screen.
;-)

Regarding books, the best I have ever read is "High Performance Sailing" by Frank Bethewaite - he is a meteorologist and aeronautical engineer, has (IIRC) 5 world championships between his 2 kids and he and his son were largely responsible for the development of the 18" Skiffs here in Aus as well as many other classes. He was also official met for the Aus Olympic sailing team for decades - so while the book is largely detailed toward dinghies, there are also excellent sections on weather reading and waves etc...
When he retired from his job, he and a likeminded group set about trying o understand boats better and to make them sail faster (this was decades ago, before much of what we now know was known), and (one of) the thing i really like about his book is he talks alot about the actual experiments they did to sail faster - and not just 2 boat testing or similar, but actual emperical scientific experiments, like drag tests on foil designs and he even built his own wind tunnels - probably the advance he is most known for inventing/discovering is the wing-mast.
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
AGage


Users avatar

Posts
411
Registered at
2008-12-27 10:31:57
2011-04-11 07:55:49 - Re: VMC or "by the numbers" in oscillating winds
BTW, The Ockam site is chock full of great info - when it mentions using 'strip charts' these are available for SOL by using brainaid's NMEA proxy and NavMonPC, which gives you stripcharts for both wind data and boat performance
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
sol


Users avatar

Posts
297
Registered at
2008-08-14 11:08:14
2011-04-11 09:54:17 - Re: VMC or "by the numbers" in oscillating winds
Thank a lot Aaron. I have seen "Wallying" mentioned, but have put it on the backburner for the time being. Now I find that I already know what it is:)

Thanks for the links, and the trick with the predictor and markers.

I have your Butterfly, but having been a SOTP sailor for almost 50 years - I havn't really figgered out what to use it for. I just print a paper copy of the polar. I will look more into it though. At my age - I'm a slow learner.
Posted by
WhyNot


Users avatar

Posts
51
Registered at
2011-02-03 18:39:54
2011-04-11 09:57:16 - Re: VMC or "by the numbers" in oscillating winds
Ooopss! That was me answering:). To many instances of SOL running at once.

Sorry
Posted by
76Trombones


Users avatar

Posts
362
Registered at
2009-08-03 18:04:56
2012-02-18 20:15:03 - Re: VMC or "by the numbers" in oscillating winds
I'm not actually sure that this is working properly, but here is a quick spreadsheet that I worked up a while ago, allowing you to compare VMG and VMC courses for different shifts and target angles/mark locations. You want the target that'll get you to the mark the quickest, which depends more-or-less on average wind direction. The amount you can foot varies with the amount of shift.
Attachments
Posted by
76Trombones


Users avatar

Posts
362
Registered at
2009-08-03 18:04:56
2012-02-18 20:23:45 - Re: VMC or "by the numbers" in oscillating winds
Updated to show the effect of sailing VMG on the wrong tack. Footing on the wrong side is even worse, obviously.
Attachments

Page: Previous 1 2

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Pantaenius Shetland Race 2025 - Leg 2

After the excitement and fierce competition of the first leg, the adventure swiftly continues! With just enough time to relish the vibrant celebrations in Lerwick, Shetland, sailors set their sights on Bergen, Norway, for the gripping second leg of Sailonline’s exhilarating two-race Shetland Series. Another riveting 190 nautical miles of the unpredictable North Sea awaits, challenging competitors aboard the exceptional Salona 39, crafted in collaboration with Maurizio Cossutti for peak sailing performance. Whether you're strategizing for victory or simply embracing the joy of the voyage, this leg guarantees excitement, tactical depth, and unforgettable sailing moments. Hoist your sails—let the journey home begin!
Race #1927
INFO by brainaid.de
Salona 39 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SHE - SYC
Race starts: Jun 21st 16:00 Registration will open soon
▶ Flash
GO TO RACE

Brisbane to Keppel Tropical Yacht Race 2025


When the winter weather turns cool in southern Australia sailors head up to the warmer waters of The Great Barrier Reef and the big winter regattas at Hamilton Island, Airlie Beach and Magnetic Island. But the race isn’t ‘on’ this year; nevertheless, Sailonline is inviting all racers from RQYS and beyond to race the 343 nm for the fun, this time in our SOTO 40. It might be winter downunder but do put on your shorts and t-shirts before you sit down behind your devices to get into the spirit of it all!
Race #1921
INFOby brainaid.de
SOTO 40 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Jun 19th 01:00 Registration Open!
▶ Flash
GO TO RACE

Pantaenius Shetland Race 2025 - Leg 1

Prepare your sails and brace for exhilaration—it's time once again to embark on the thrilling journey from Norway's stunning outer Korsfjorden to the ruggedly beautiful Shetland Isles! Welcome to the first electrifying leg of Sailonline's celebrated two-race Shetland Series. Spanning nearly 190 nautical miles, this year's challenge features the Salona 39, masterfully designed in collaboration with Maurizio Cossutti. Sailonline proudly partners with this iconic race, bringing sailors from around the globe together to test their strategic prowess and seamanship. Whether you're a seasoned veteran or setting out on your first virtual adventure with us, get ready for an unforgettable race filled with intense competition, breathtaking scenery, and the sheer joy of sailing. The North Sea awaits—let the adventure begin!
Race #1922
INFO by brainaid.de
Salona 39 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SHE - SYC
Race starts: Jun 18th 11:00 Registration Open!
▶ Flash
GO TO RACE

Haugesund to Reykjavik 2025


In late April 2016 Draken Harald Hårfagre, the worlds largest viking ship built in modern times, left her home port in Haugesund, Norway and sailed off for a challenging voyage across the North Atlantic Ocean.
The aim was to explore and relive one of the most mythological sea voyages – the first transatlantic crossing, and the Viking discovery of the New World, more than a thousand years ago. History tells us about the Viking explorer, Leif Eriksson, who discovered America over 500 years before Christopher Columbus. The expedition was all about exploring the world, just like the Vikings did.
Sailonline is racing the 1000 nm first leg, from Haugesund, Norway, to Reykjavik, Iceland in our Farr 400. Let us sail in the wake of history on this epic adventure!
Race #1913
INFO from brainaid.de
Farr 400 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ2 - ARCH - SUPSOL – SYC
Race starts: Jun 16th 17:00 Registration Open!
▶ Flash
GO TO RACE

Africa by Sea - Swakopmund to Maputo 2025


Time again to continue our exploration of Africa by Sea, which now takes us around the tip of the continent at Cape Agulhas and up the coast of South Africa to Mozambique’s marvellous Maputo, where we should find good anchorage in the bend of the Rio Espirito Santo (Umbuluzi) once we’ve cleared the 60m high Maputo - Katembe suspension bridge. It’s 1900nm and we’ll be glad to be sailing our comfortable and sturdy Xp-55, as we will certainly experience more headwinds!
Race #1857
INFOby brainaid.de
Xp-55 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - ABC
Race starts: Jun 11th 17:00 Registration Closed
▶ Flash
GO TO RACE

Marquesas to Young Island 2025

The adventure continues as we launch this fourth leg of the RWW series, racing from Marquesas to Young Island in the Balleny Islands, a group of islands in the Southern Ocean only 62 nm from Antarctica. Get ready for a chilling new challenge as we set sail on the sixth leg of the 2025 Ocean Championship Series! A 4100nm journey of endurance, strategy, and pure sailing excitement. This leg will be pursued aboard the race machine RP66, pushing sailors to their limits. Do you have what it takes to conquer the Southern Ocean? Join us and put your skills to the ultimate test!
PRIZE: SMPF
Race #1909
INFO by brainaid.de
Raichel/Pugh 66 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ2 - RWW - OCCH - SUPSOL - SYC
RACE CLOSE: Saturday,
June 21 at 2300 UTC.
Race starts: Jun 02nd 11:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member CriticalHippo
  3. Sailonline Yacht Club Member KaSToR
  4. Sailonline Yacht Club Member FreyjaUSA
  5. Sailonline Yacht Club Member Patrick70119
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member rafa
  8. Sailonline Yacht Club Member rumskib
  9. Sailonline Yacht Club Member bonknhoot
  10. Sailonline Yacht Club Member Smo

View full list

Series

Mobile Client

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

The mobile client