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

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?
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!
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.


Next Race: 00d 00h 00m

Current Races:

Victoria to Maui 2022
The Victoria to Maui International Yacht Race, first contested in 1968, is the pinnacle of Pacific Northwest ocean racing, running every two years. This year, Sailonline invites the SOL fleet to race the 2300nm course in Delphia 47s, from Victoria, British Columbia to Hawaii, finishing off Lahaina Maui.
Race #1596
INFOby brainaid.de
WX Updates:
0430 / 1030 / 1630 / 2230
Race starts: Aug 09th 19:00 Registration Open!

▶ Flash

Brisbane to Hamilton Island Yacht Race 2022

Time once again to head for the warm waters inside The Great Barrier Reef, but this year not only online but together with our buddies at the Royal Queensland Yacht Squadron and their friends from across the world, in the iconic Brisbane to Hamo! Online we’re racing maxi’s to give you a chance to cover the 550 glorious blue water nautical miles in a time to best some of the fastest monohulls on the planet including Andoo Comanche, Black Jack and Hamilton Island Wild Oats . Fair winds, all!
Race #1606
INFOfrom brainaid.de
Super Maxi 100 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Aug 05th 01:00 Registration Open!
▶ Flash

Sailonline’s 15th Birthday Balloon Race
Sailonline offers a huge variety of boats to sail in. One of the more unusual ones has got to be SOL's Balloon, which was polarized by past SOLmaster 76Trombones. Notably, the SOL Balloon will actually ‘sail’ in other directions other than straight downwind, although it will not 'sail' over land or beyond a 'beam reach'. Like in 2013 and 2018, we will be taking the Balloon across the Atlantic from St. John's and 'land' it in the sea off the Cliffs of Moher.
Race #1605
INFO by brainaid.de
WX Updates:
0430 / 1030 / 1630 / 2230
Race starts: Aug 01st 19:00 Registration Open!

▶ Flash

Simonstown to St Helena 2022
This is a copy of a traditional South African December yacht race, but this time we will be racing in the middle of European summer. SOLers are invited to race 1712nm in our GB90s from Simonstown, RSA, to the exotic and remote island of St Helena - an island paradise with warm, friendly, hospitable islanders!
Race #1593
INFO by brainaid.de
WX Updates:
0430 / 1030 / 1630 / 2230
Race starts: Aug 01st 18:00 Registration Closed

▶ Flash

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member Pit8008
  3. Sailonline Yacht Club Member rafa
  4. Sailonline Yacht Club Member FreyjaUSA
  5. Sailonline Yacht Club Member GREATSKUA
  6. Sailonline Yacht Club Member Vida_Maldita
  7. Sailonline Yacht Club Member Sax747
  8. Sailonline Yacht Club Member HappyHour
  9. Sailonline Yacht Club Member Satori
  10. Sailonline Yacht Club Member Kipper1258

View full list


Mobile Client

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

The mobile client