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 » General Discussion » VMC

Posted by
JimGodders


Users avatar

Posts
3
Registered at
2011-11-06 17:56:14
2018-09-11 20:30:24 - VMC
Hi all,

I've been reading about a little as I'm looking to improve, and have zeroed in on VMC as an interesting concept. But, for the life of me, I can't seem to get my head round it properly and I have a few questions that I'm sure you fine folks will be able to answer for me.

As I understand it, sailing to VMC maximises the boat's speed over the ground in the defined direction. Considering 2 boats, starting at the same point at the same time with both wanting to get as far north as they can, if 1 is sails to VMC, they will be further north than the other sailing due north, though the boat sailing to VMC will also be off to the left or right.

What I'm struggling to understand is how this is useful in racing. I know there's little point in sailing VMC direct to a mark if the wind ins't expected to shift as you'll lose whatever time you've gained on the leg trying to get back to the mark.

I've seen some suggest that in shifting wind, a reasonable VMC target is to sail to half the shift. I don't understand what this means though. I've tried google but to no avail - this doesn't seem to be a topic that is easily accessable. Could someone please explain what the VMC target would be if trying to get a mark due north, with a wind veering from NW to W over the course of the leg please?
Posted by
Bimmer


Users avatar

Posts
447
Registered at
2015-02-23 15:38:27
2018-09-12 07:05:40 - Re: VMC
Posted by
JimGodders


Users avatar

Posts
3
Registered at
2011-11-06 17:56:14
2018-09-12 18:50:34 - Re: VMC
Thanks very much Bimmer. I had seen that article already, and others on the same blog and this is what is leading to my confusion!

Let's take this article. Outlaw has chosen to VMC to a bearing of 280*. For the given wind conditions, sailing a course over the ground of 307* gets Outlaw furthest down a line drawn from his/her current position on a bearing of 280*, though they will be to starboard of a point on a direct 280* bearing from their current position. Nevertheless, sailing a course of 307* gets them farthest up the 280* bearing.

Now, I understand that 280* was chosen as this is the TWD that Outlaw will tack at. But this is what I can't quite get my head around. A TWD of 280* seems incorrect - that could happen anywhere along the leg, and not necessarily in the best tacking position. Does he mean he'll tack when the bearing to the mark is 280*? I often see mentioned that a tack/gybe should be done when VMC = VMG. Why is this not a consideration here?

I feel like this is a missing piece of the puzzle for me, so I'd love to try and understand it better!
Posted by
outlaw


Users avatar

Posts
33
Registered at
2012-06-01 13:37:55
2018-09-13 21:48:43 - Re: VMC
1. I prefer 'his'. Not that I've ever claimed to be human.
2. The only claim is that if I sail a couple hours at a set VMC, and arrive at point A, it is fundamentally impossible to beat me to point A. Bimmer could sail to point B, then have the faster path to the finish. Happens.
3. The causality for picking the target IS confusing. In an ocean race I could decide to go 'west', wade thru bird entrails until I come up with VMC280, and tack at TWD280 because that's how the VMC function works.

OTOH in a round the buoys type race I could just do an SOTP estimate where/when I'm going to tack, determine the TWD @tack, and use that as the target. Post tack the boat would just point in the general direction of the mark, bearing ~240, probably.

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Cape Town to Rio 2026

Welcome to South Africa and RCYC's classic transatlantic Cape2Rio Race from Cape Town, South Africa, to Rio de Janeiro, Brazil. First run in 1971, this run is buddied with the IRL, Cape2Rio 2025 arranged by the Royal Cape Yacht Club with the cooperation of the
Iate Clube do Rio de Janeiro Despite this being announced the 2025 race (starting dec. 27) it is the 2026 SOL championship kickoff. This virtual version, will be raced once again in Mark Mills' 74ft speedster, the stunning C2R74.
Race #1996 INFO
by brainaid.de
C2R74 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
OCQ1 - OCCH - SUPBUD - SYC
Race starts: Dec 27th 12:00 Registration Open!

▶ Flash
GO TO RACE

ORCV Melbourne to Hobart 2025

Welcome to the legendary Westcoaster, a true test of endurance and seamanship that’s challenged sailors for over 50 years! Spanning 435 nautical miles, this iconic race takes the fleet from Melbourne, across the wild Bass Strait, and around Tasmania’s rugged west coast to Hobart. Organized by the Ocean Racing Club of Victoria, this year our SOLers will be racing the sleek and powerful Dehler 46—a fast, elegant regatta cruiser built for both speed and adventure. Get ready for an unforgettable offshore classic!
Race #1952
INFO by brainaid.de
Dehler 46 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Dec 27th 02:30 Registration Open!
▶ Flash
GO TO RACE

Tasman Double 2025 - Sydney to Hobart

Christmas in Summer? Indeed! Kick off the first leg of our two-leg Tasman Double series in the classic 625nm Sydney to Hobart race, this year in the upgraded SuperMaxi 100v2. Inspired by Neville Crichton’s legendary Alfa Romeo II and her near-sister Wild Oats XI, these yachts blaze across online and real-world waters alike. Feel the thrill even in storm-force winds as you tackle the Tasman Sea—dock in Hobart victorious, or at least in time for a well-earned post-Christmas drink!
Race #1953
INFO by brainaid.de
Super Maxi 100v2 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: TD - SYC
Race starts: Dec 26th 02:00 Registration Open!
▶ Flash
GO TO RACE

Valletta Sprint 2025


We invite you once again to this SOL classic around the Middle Sea, departing from and returning to historic Valletta. Loseley modelled on an IRL classic often sponsored by a luxury wristwatch purveyor, our c 600nm course takes us north as far as Stromboli, then west of Sicily and south to Lampedusa and back to Valletta probably via the strait between Malta and Gozo. This year we will race it all in very Meddy Dufour 40’s!
Race #1949
INFO by brainaid.de
Dufour 40 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
RACE CLOSE: Monday,
December 29 at 2300 UTC.
Race starts: Dec 20th 11:00 Registration Closed
▶ Flash
GO TO RACE

Chatham Island TIMED Chase 2025

The final TIMED race of 2025 takes us to the isolated and mysterious Chatham Islands archipelago 430 nm east of New Zealand’s South Island. There promises to be plenty of breeze from every point on the compass as we sail the Farr 38 around Chatham Island, Pitt Island, and The Forty Fours on this 124 nm course. 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 #1990
INFOby brainaid.de
Farr 38 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ4 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
27 December at 23:00 UTC
Race starts: Dec 14th 12:00 Registration Open!
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member KaSToR
  2. Sailonline Yacht Club Member WRmirekd
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member bonknhoot
  6. Sailonline Yacht Club Member vida
  7. Sailonline Yacht Club Member CollegeFund
  8. Sailonline Yacht Club Member Sax747
  9. Sailonline Yacht Club Member pepsPV5
  10. Sailonline Yacht Club Member Panpyc

View full list

Series

Mobile Client

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

The mobile client