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 » Minimum constant Boat Speed.

Posted by
JB


Users avatar

Posts
305
Registered at
2013-03-07 08:54:34
2014-04-07 11:32:29 - Minimum constant Boat Speed.
For the moment it’s not possible to fix Waypoints in the SOL navigation system as also is not possible to “reduce” sail area in order to obtain a particular Boat Speed (“BS”), but with a little work I think it would be possible to impose a minimum constant Boat Speed (“mcBS”) during a period of time you previously define.

It would be the same as reducing/trimming the sail area (some reefs on the mainsail plus a smaller genoa, jib or gennaker, whatever) to have the boat underpowered and moving under a constant BS.

Knowing the exact distance between turning points, with a constant Boat Speed (“BS”) is equal to know the exact ETA’s on every waypoint you need to change the boat Course Over Ground (“COG”) as Time of the leg is obtained dividing de Distance to be made by the Speed in that run, that’s simple kinematics.

I’ll give a simple example to illustrate better my wish for the new SOL navigation utility.
The race is the Race 2 on the SSANZ B&G Simrad Series 2013 where you have to round the Little Barrier Island by night - see picture in the attachment.
Coming from South and the wind blowing from the 100º quadrant, you’ll have to make at least #2 changes in COG to round the island back to South.
Some of the sailors will have to make some DC’s (“Delayed Commands”) to perform that task.

In this case, the main problem to make the correct DC’s is to perform the exact calculation of the (will be) Boat Speeds (BS’s) after changing the boat COG in the turning points, knowing the distances between them. If you over calculate your BS you’ll end up going aground. If, by the contrary, you underestimate it, you’ll waste a lot of precious miles going way from the exact points of turning (the picture illustrates precisely booth cases with the same boat tracking).

Looking to the Boat Polar (“BPo”) you can estimate that during the period of rounding the island your minimal BS would be 6 knt (let’s say, dead downwind) and the maximum 10 kn. If you don’t want to take risks on using several estimated Boat Speeds in your calculations, the solution will be to use a unique mcBS for calculating the “ETA’s” in the turning points and impose it in the navigation to perform.

But, if for instance, your imposed mcBS was above the minimum permitted by the BPo during that period of turns, the mcBS would be that precise minimum and so, corrected during the crossing for all efects.

I imagine the utility of that tool on a race like the Turkey one, with two (dire) straits in a row.
Sail Fair.
Attachments

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

West Papua to Oregon 2026

Our next race in our Ocean Championships is the first of a series of great natural migrations we will track in 2026. The leatherback turtle is the most widely distributed marine reptile on planet Earth, and chooses to breed in warm tropical waters, but prefers to forage in more temperate habitats, travelling thousands and thousands of miles effortlessly annually to maintain this way of life. Our race will follow one of the typical trips of this turtle, from breeding grounds in the seas off West Papua to the coast of Oregon. It’s only 5900nm, so to keep up, but in comfort, we’ll follow in our Gunboat 90.
Race #2006
INFO by brainaid.de
GB 90 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ1 - OCCH - MIG - SYC
Race starts: Feb 02nd 11:00 Registration Open!
▶ Flash
GO TO RACE

Race to Up Helly Aa 2026

A-OI!!! The fiery spirit of Shetland’s legendary Up Helly Aa returns, and Sailonline’s annual race to Lerwick is once again upon us. Covering 383 nautical miles from Aberdeen, SOLers will tackle winter waters steeped in Viking tradition. This year, we race the classic Frers 33, a proven cruiser-racer born from the golden era of offshore racing and still a sturdy performer both on the virtual and real water. Can you master the course and reach Lerwick in time for the flames?

SAILING NOTE: Gruney may be approached from any direction but must be passed for rounding purposes as indicated on the chart.
Race #2005
INFO by brainaid.de
Frers 33 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SYC
Race starts: Jan 30th 17:00 Registration Open!
▶ Flash
GO TO RACE

Red Eye - Hobart Convict Run 2026

Back in 2010, one of our SOLers of the first hour, AUS_Scott76, came up with this ‘Convict Run’ out from Hobart, past Cape Raoul and the penal colony of Port Arthur, round Tasman Island, up and back down the east coast of Tasmania, to finish with a tight technical run – so Scott called it – up the picturesque D'entrecasteaux Channel, home to Hobart once again. It’s 250nm, ideal for a bit of ‘Red Eye’ in comfortable Finngulf 43’s, and if the original idea was to pick up some convicts on the way for a bit of R&R and sea air, you may always drop’m back before returning to Hobart!
Race #2002
INFOby brainaid.de
FG 43 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: RED - SYC
RACE CLOSE: Monday,
February 2 at 2300 UTC.
Race starts: Jan 27th 12:00 Registration Open!
▶ Flash
GO TO RACE

New Ice Age 2026 - Longyearbyen to Browerville


Although we have by no means exhausted the possibilities of ice boating on lakes at high latitudes or high altitudes, it was noticeable that as our 2025 Series progressed, there were calls from time to time for longer-distance challenges, and so in response to these calls we will pretend that global warming has reversed and as a result the coastal waters of Antarctica and Russia and Canada have fully (and smoothly!) frozen over offering us the possibility of a 4-race New Ice Age series in our trusted no-PL DN machines. Our first leg takes us 2600nm from Svalbard’s Longyearbyen east to North Alaska’s Browerville. You’ll be a few days on the ice, so dress warmly and take some provisions; go!
Race #1968
INFOby brainaid.de
DN PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: NIA - SYC
RACE CLOSE: Monday,
February 2 at 2300 UTC.
Race starts: Jan 22nd 07:00 Registration Closed
▶ Flash
GO TO RACE

Cross the Convergence 2026 - Robinson Crusoe to Galapagos


Welcome to our first race of a new series of ocean voyages across the World’s convergence zones, this first race taking you north from south of the Tropic of Capricorn to the Equator-straddling Galapagos, home of magical iguanas and other exotic fauna (but no mythical kings, Dory) Departing from the island where in 1704 adventurer Alexander Selkirk inspired Daniel Defoe to write the best-seller "The Life and Adventures of Robinson Crusoe", by debarking off the unsound "HMS Cinque Ports", four months before she foundered off the coast of present-day Colombia, we will sail the 2200nm in our decidedly sounder and faster than the " Cinque Ports",
Ocean 50 !
Race #1983
INFOby brainaid.de
Ocean 50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: CCZ - SYC
RACE CLOSE: Friday,
January 30 at 2300 UTC.
Race starts: Jan 16th 18:00 Registration Closed
▶ 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 Sax747
  6. Sailonline Yacht Club Member rumskib
  7. Sailonline Yacht Club Member bonknhoot
  8. Sailonline Yacht Club Member vida
  9. Sailonline Yacht Club Member Panpyc
  10. Sailonline Yacht Club Member Kipper1258

View full list

Series

Mobile Client

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

The mobile client