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:

ORCV Melbourne to Hobart 2024


Welcome to the legendary "Westcoaster," a race that has tested sailors for over 50 years. Spanning 435 nautical miles, this iconic journey takes racers from Melbourne, across the formidable Bass Strait, and around Tasmania's rugged west coast to the finish line in Hobart. Organized by the Ocean Racing Club of Victoria, the Westcoaster is renowned for its challenging conditions and adventurous spirit. This year, our SOLers will tackle the course in the swift and capable First 47.7, a yacht launched by Beneteau in 2000, built for speed and endurance in long ocean races. Get ready for an exhilarating ride in one of Australia’s most celebrated yacht races!
Race #1841
INFO by brainaid.de
First 47.7 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Dec 26th 23:00 Registration will open soon
▶ Flash
GO TO RACE

Refeno Rally 2024


Although since 1986 this 300nm course from Recife, Brazil, to Fernando Noronha Island has been run many times IRL, we have only used this route twice in SOL. This time it will be the route of the last race in the ARCH 2024 classification.
Although the winner of the general classification can already be determined, the fight for the next places on the podium should be fierce. There are several contenders and Dofour34 have them at their disposal. Since we are starting in Vida_Maldita's home waters, he will give us a 30-minute handicap. Or maybe we should give it to him? 😊
Race #1865
INFO from brainaid.de
Dufour 34 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ4 - ARCH - SUPSOL - SYC
Race starts: Dec 23rd 17:00 Registration Open!
▶ Flash
GO TO RACE

Tristan da Cunha TIMED Race 2024

Originally designed by NZL_Scotsman, we head for the remote outpost of Tristan da Cunha where gales and storms may come and go but the sea is everlasting. This 64nm TIMED race has been raced on several occasions before, and this time we will be doing it in Rustler 36s.
RE-REGISTER HERE to race again after finishing a run
Race #1875
INFO by brainaid.de
Rustler 36 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ4 - TRCH - SUPSOL - SYC
REGISTRATION CLOSE: Saturday, 28 December at 22:00 UTC
RACE CLOSE: Saturday, 28 December at 23:00 UTC
Race starts: Dec 15th 12:00 Registration Open!
▶ Flash
GO TO RACE

The Beagle in the Azores 2024


And west the Beagle went one final time to round the Cape of Good Hope on May 31 1836. Ashore, Darwin met up with the Astronomer Royal, Herschel, who just happened to be in South Africa at the same time mapping the southern skies. After sounding out his many ideas on evolution and extinction with Herschel, the Beagle now sailed north, stopping briefly in St Helena, Ascension and Brazil, and the Cape Verdes again, to reach the Azores on September 19, 1836. Fitzroy and Darwin at this stage were in a hurry to get back to Britain, but online in 2024 we will stay a little longer to explore this final remote archipelago in our virtual Tall Ship Class B Beagle, 630nm round and about the islands, minding as always in these waters not to bump into any large cetaceans!
Race #1758
INFOby brainaid.de
Tall Ship Class B PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SVF - SYC
RACE CLOSE: Friday,
December 27 at 2300 UTC.
Race starts: Dec 14th 13:00 Registration Closed
▶ Flash
GO TO RACE

Christmas(W) to Christmas(E) Island 2024

Two waypoints, start and finish, and between them 5827 NM of two oceans. Not much time if we want to sit at the Christmas Eve table. You will need to maintain an average speed of over 10 knots, so prepare your 90ft well and choose the best of the many possible routes. Hands up everyone who knew there were TWO Christmas Islands?! OK, maybe you have sailed this Sailonline course before... but it's time to get ready for the 2024 challenge of a reversed race, starting in the Indian Ocean, racing to the Christmas Island in the Pacific! It also marks the conclusion of our prestigious Ocean Race Championship 2024. Please have fun! Fair winds!
PRIZE: SMPF
Race #1868
INFO by brainaid.de
90ft Monohull PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ4 - OCCH - SUPSOL - SYC
Race starts: Dec 02nd 11:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member FreyjaUSA
  3. Sailonline Yacht Club Member Vida_Maldita
  4. Sailonline Yacht Club Member CriticalHippo
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member Satori
  8. Sailonline Yacht Club Member Sax747
  9. Sailonline Yacht Club Member BRENTGRAY
  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