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:

Silverrudder 2025


Ahoy, SOLers! Get ready for the epic Silver Rudder – Challenge of the Sea! This 125nm single-handed race around Denmark’s island of Funen is back—shallow waters, narrow straits, and shifting winds await. This year, we trade up to our single-handed X-99s—can you master their power where precision counts most? It’s the world’s largest solo regatta, and your virtual helm is calling! Chart your course, trust your instincts, and race for glory in this ultimate test of seamanship!

It is imperative that you read AND understand these special Starting Conditions for SILVERRUDDER 2025:
Starting Conditions!!
Race #1948
INFO by brainaid.de
X-99 Single-handed PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Sep 19th 09:00 Registration Open!

▶ Flash
GO TO RACE

Rome to Tripoli 2025


The next race in the ARCH series will take us almost straight from Rome to Tripoli. But don't expect this 550nm race to be an easy one. The Mediterranean always offers some surprises. So let's prepare your Lagoon 55 with due care and... Fair Winds.
Race #1943
INFO from brainaid.de
Lagoon 55 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ3 - ARCH - SUPSOL – SYC
Race starts: Sep 15th 17:00 Registration Open!
▶ Flash
GO TO RACE

Carib Rum Run 2025

Welcome to the Caribbean and Sailonline’s legendary Carib Rum Run! This year we trade tall ships for pure speed as we race our sleek Santa Cruz 70s on a 1759nm slalom through the rum islands. Yer mission: plunder barrels from the region’s finest distilleries and deliver ‘em to the rum-thirsty sands of Cancun, Mexico. Finish on or before International Talk Like a Pirate Day, 19 September, to etch yer name in legend! Join SYC before race end and ye scallywags can disguise yer boat with a pirate name for this race only! Hoist the sails, sharpen yer cutlasses—the rum run awaits!
Race #1944
INFO by brainaid.de
Santa Cruz 70 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Sep 15th 00:00 Registration Open!
▶ Flash
GO TO RACE

Roslagen TIMED Sea Race

Welcome to quite possibly the most challenging TIMED race of the year. This month finds us in Sweden with lots of islands and narrow passages when we sail our Seacart 30 trimaran over the 86nm from Lidingö outside Stockholm to the beautiful coastal village of Öregrund. Consider yourself a winner if you complete the course nonstop! 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 #1945
INFO by brainaid.de
Seacart 30 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ3 - TRCH - SUPSOL - SYC
Race starts: Sep 07th 12:00 Registration Open!
▶ Flash
GO TO RACE

The Vineyard Race 2025


For the first time since first hosting a virtual Vineyard in cooperation with Long Island's Stamford Yacht Club back in 2010, due to an operational calendaring error, Sailonline has missed the start of the real life race, the USA’s Labor Day weekend this year unusually falling across the turn of August. Silly SOL! So, a week late please join us anyway for a virtual rerun of Stamford’s iconic annual overnighter from their club line out the sound to Buzzard's Bay Light near Martha's Vineyard Island and back again, leaving Block Island to starboard. This year, Sailonline is making its magic MC 38 available to competitors, a race boat with a quirky polar that will require you to stay wide awake as you speed around the c 250 nm course, in rockstar style!
Race #1946
INFO by brainaid.de
MC 38 PARTICULARS
NAM_AWIP WX Updates:
0245 / 0845 / 1445 / 2045
Ranking: SYC
RACE CLOSE: Sunday,
September 14 at 2300 UTC.
Race starts: Sep 06th 17:05 Registration Closed
▶ Flash
GO TO RACE

Great Nicobar to Marion Island 2025

The Adventure Continues – Leg #6 of the RWW Series.
We’re setting sail on the next stage of the RWW Series: a 4,400-nautical-mile passage from Great Nicobar to Marion Island. This demanding leg will test endurance, strategy, and seamanship at the highest level. As part of the 2025 Ocean Championship, this marks the ninth legendary challenge in the series — and one of the most exhilarating yet. The race will be contested aboard the Archer 78’ ketch, a vessel built to push sailors to their limits across the vast Indian Ocean.
PRIZE: SMPF
Race #1942
INFO by brainaid.de
Archer 78 PARTICULARS    
WX Updates:
0430 / 1030 / 1630 / 2230    
Ranking: OCQ3 - RWW - OCCH - SUPSOL - SYC
Race starts: Sep 01st 11:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member vida
  2. Sailonline Yacht Club Member WRmirekd
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member KaSToR
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member BRENTGRAY
  8. Sailonline Yacht Club Member Sax747
  9. Sailonline Yacht Club Member Panpyc
  10. Sailonline Yacht Club Member CollegeFund

View full list

Series

Mobile Client

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

The mobile client