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:

SSANZ Round North Island Race 2026 - Leg 3

Leg Three of our Round North Island Series, in partnership with SSANZ, keeps the pressure on! From Cook Strait, the fleet turns north for a 187 nautical mile passage up the east coast to Napier. It may look like a quick overnighter, but shifting coastal winds and the ever-lively Cook Strait demand sharp focus. In our responsive Sun Fast 3600s, a proven short-handed racer and powerful downwind performer, tactical decisions and precise timing will make all the difference!

The start time for this race may change at short notice to align with the real race. The confirmed start date and time will be announced via an in-race “L” flag message — Please monitor race communications closely.
Race #2013
INFO by brainaid.de
Sun Fast 3600 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: RNI - SUPBUD - SYC
Race starts: Mar 08th 21:00 Registration will open soon
▶ Flash
GO TO RACE

Dyer Dhow Derby 2026


Most winter weekends, SOLer wsguerin and his friends at the Mamaroneck Frostbite Association venture forth on Long Island Sound to race Dyer Dhows, originally designed as WWII tenders. Indestructible little boats, great comradeship and serious short sharp races of 10 to 20 minutes duration. Sailonline now invites you to experience the joys of the Dhow in winter, virtually, by way of a slightly longer 14nm race: from Mamaroneck to Execution Rocks, over to the Gong Buoy and back to Mamaroneck. And if the wind pipes up to 20kn and beyond, you'll find SOL's customized polar will plane, rather than nosedive!
Race #2017
INFO by brainaid.de
Dyer Dhow PARTICULARS
NAM_AWIP WX Updates:
0245 / 0845 / 1445 / 2045
Ranking: SPQ1 - SPCH - SYC
Race starts: Mar 07th 13:00 Registration will open soon
▶ Flash
GO TO RACE

South China Sea Race 2026


Welcome all to the South China Sea and a virtual chase in Cookson 50’s of the Rolex South China Sea fleet, racing 650nm – as the local red-footed booby flies – from Hong Kong to Subic Bay on the southern tip of The Philippines’ Luzon Island. Chances are it will be a fast downwind ride, so see how you can keep up with the real-life fleet which we hope to be able to follow on our monitors.
Race #2016
INFOby brainaid.de
Cookson 50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SUPBUD - SYC
Race starts: Mar 04th 03:20 Registration Open!
▶ Flash
GO TO RACE

SSANZ Round North Island Race 2026 - Leg 2

Leg Two of our Round North Island Series is where the real challenge begins. After Mangonui, our SOLers face a demanding 491nm passage around the top of the North Island and down the rugged west coast toward Cook Strait. Long miles, exposed waters, and relentless tactical choices will test every SOLer. In our powerful Sun Fast 3600s, a proven short-handed performer and true downwind flyer, endurance, timing, and smart routing will be key to success!

The start time for this race may change at short notice to align with the real race. The confirmed start date and time will be announced via an in-race “L” flag message — Please monitor race communications closely.
Race #2012
INFO by brainaid.de
Sun Fast 3600 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: RNI - SUPBUD - SYC
Race starts: Mar 02nd 21:00 Registration Open!
▶ Flash
GO TO RACE

Iceland to the Falklands 2026

Welcome to an all-new route, the first of three Round the 'Old World' of Europe, Africa, Australia and Asia. To give each leg of the ROW a bit of length we'll try to hug the coasts as little as possible, so starting in Iceland our first leg of the series, which will also be the final leg of our Quarter 1 Ocean Championships takes us 7200nm to the Falklands, the full length of the Atlantic end to end. To make sure we'll get it done within the month we'll be sailing our Maxi Trimaran.
Race #2010
INFO by brainaid.de
Maxi Trimaran PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ1 - ROW - OCCH - SYC
Race starts: Mar 02nd 11:00 Registration Open!
▶ Flash
GO TO RACE

SSANZ Round North Island Race 2026 - Leg 1

Welcome to Leg One of the Round North Island Series in partnership with SSANZ. The four-leg circuit of New Zealand’s North Island is a true test of short-handed skill, and it begins with the 150nm passage from Auckland to Mangonui. This year, our SOLers will be racing the dynamic Sun Fast 3600 – Jeanneau’s renowned racer-cruiser and a proven flyer downwind. A gentle opener on paper… but coastal tactics and shifting breezes will demand focus from the start!
Race #2011
INFO by brainaid.de
Sun Fast 3600 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: RNI - SUPBUD - SYC
RACE CLOSE: Thursday,
March 5 at 2300 UTC.
Race starts: Feb 28th 21:00 Registration Closed
▶ Flash
GO TO RACE

San Diego to Puerto Vallarta 2026

Welcome to California! Established in 1953 this 1000-mile run from San Diego to Puerto Vallarta on the Mexican Riviera has become a tradition and online as well the tradition strengthens with this the fourth time Sailonline is making the race available to virtual sailors. Let's see how our virtual SC70s perform against the real fleet!
Race #2015
INFO by brainaid.de
Santa Cruz 70 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SUPBUD - SYC
Race starts: Feb 28th 20:00 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 rumskib
  5. Sailonline Yacht Club Member vida
  6. Sailonline Yacht Club Member Sax747
  7. Sailonline Yacht Club Member CollegeFund
  8. Sailonline Yacht Club Member rafa
  9. Sailonline Yacht Club Member Panpyc
  10. Sailonline Yacht Club Member sassy63

View full list

Series

Mobile Client

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

The mobile client