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:

Alicante TIMED Race 2025

Welcome to beautiful Alicante on Spain’s Costa Blanca. Dine on some local tapas and paella before racing your America’s Cup foiling winged-sail AC72 catamaran on this 208nm race out to and around Isla de Formentera returning to Alicante after rounding the mark at Cap de la Nau. There should be some very fast times! 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 #1958
INFOby brainaid.de
AC72v2 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ4 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
25 October at 23:00 UTC
Race starts: Oct 12th 12:00 Registration will open soon
▶ Flash
GO TO RACE

Marion Island to Fernando de Noronha 2025

The adventure continues as we launch the next to last leg of the RWW series. This leg takes us from Marion Island to Fernando de Noronha, an island in the world heritage archipelago with the same name, 220 nm off the coast of Brazil. This race doubles up as #7 of RWW and #10 of OCCH. A 4400 nm journey of endurance, strategy and pure adrenaline. The RWW series is as whole, part of the 2025 ocean championship. Get ready for this exhilarating challenge as we set sail on the third to last leg of the 2025 Ocean Championship Series! This leg will be raced aboard the Judel Vrolijk 62, pushing sailors to their limits as they navigate the open ocean. Do you have what it takes to conquer the Southern Atlantic? Join us and put your skills to the ultimate test!
PRIZE: SMPF
Race #1955
INFO by brainaid.de
JV 62 PARTICULARS    
WX Updates:
0430 / 1030 / 1630 / 2230    
Ranking: OCQ4 - RWW - OCCH - SUPSOL - SYC
Race starts: Oct 06th 11:00 Registration Open!
▶ Flash
GO TO RACE

Camel or Balloon - Khartoum to N'Djamena


As there is a lull in the calendar, your PRO has decided to risk an experiment – a balloon race over land, using a workaround to eliminate the recognition of water/land transitions. If it fails, the server may crash, and we abandon PDQ, hopefully after leg 7 of the ABS race to Suez has been decided, and before the start of the 1st OCC of Q4. Camel or Balloon – c 1000 nm from a field on the north bank of the Blue Nile at Khartoum to a field on the north bank of the Chari River at N'Djamena!
Race #1956
INFOby brainaid.de
SOL Balloon PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: none
Race starts: Sep 28th 09:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member vida
  2. Sailonline Yacht Club Member WRmirekd
  3. Sailonline Yacht Club Member KaSToR
  4. Sailonline Yacht Club Member CriticalHippo
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member CollegeFund
  8. Sailonline Yacht Club Member BRENTGRAY
  9. Sailonline Yacht Club Member Sax747
  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