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 » RRS rules about mark roundings

Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2015-06-23 20:21:39 - RRS rules about mark roundings
28.2 A string representing a boat’s track from the time she begins to
approach the starting line from its pre-start side to start until she
finishes shall, when drawn taut,
(a) pass each mark on the required side and in the correct order,
(b) touch each rounding mark, and
(c) pass between the marks of a gate from the direction of the
previous mark.
She may correct any errors to comply with this rule, provided she has
not finished.

This was in response to a question that arose in the Practice Race at Kiele on 23 June 2014.
Do the SOL rules state it the same?

--- Last Edited by Rod at 2015-06-23 20:40:08 ---
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
kroppyer


Users avatar

Posts
347
Registered at
2010-02-05 15:25:55
2015-06-23 23:25:51 - Re: RRS rules about mark roundings
No.

One difference is that sol uses rhumb lines between marks. I'm sure that when drawing this imaginary string taut, it would follow a GC line, not a rhumb line. There might be more differences (I'm not sure because I find the RRS rule ambiguous).

In sol the course to be sailed in drawn on screen, order of roundings and direction of roundings is clear. While racing you can either round the next mark, or unround the previous, other marks are not in play.

Unrounding happens* when you cross the rounding line in the wrong direction and after crossing you've crossed the rounding line as many times in the correct direction as in the incorrect direction.

Rounding happens* when you cross the rounding line in the correct direction and before crossing you've crossed the rounding line as many times in the correct direction as in the incorrect direction.

Say we have marks A, B, C (in that order), then the rounding line of B is a line starting at B, moving away from A, B and C. Additionally, the rounding line lays on the bisector of angle ABC.

*) This is how I understand it should happen. I'm not entirely sure that this is the case when you sail multiple laps around the mark.

In any case, you should be able to round your next mark by sailing around it in the correct direction until it says "rounded", i.e. there's no "going in the wrong direction to unround". If you have trouble rounding the mark, it means you've already rounded in the wrong direction, all that's left is sailing around the mark in the correct direction.

----

Two more things:
- I don't like the RRS wording/theory.

- PRs are different.

--- Last Edited by kroppyer at 2015-06-23 23:34:20 ---
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2015-06-29 01:35:48 - Re: RRS rules about mark roundings
My interest stemmed from a consideration of the logic behind ANY mark rounding rule on the computer. If the SOL rule was to be applied to a spherical Earth, the projected 'rounding line' would circle the Earth and enter the mark from the rear, thus making the "miss, return and round correctly" of the RRS impossible. The field of action would have to be limited in total area to make it possible.
If the map used was to be a Mercator's projection, then no area limitation would be required.
In the case in point, if the turn mark had been just a small distance (3 pixels?) off shore, then the island could indeed have been rounded the "wrong" way,and all requirements for a successful rounding could have been met.
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
kroppyer


Users avatar

Posts
347
Registered at
2010-02-05 15:25:55
2015-06-29 13:00:55 - Re: RRS rules about mark roundings
Rounding lines in SOL are loxodromic (straight on Mercator projection). This has previously resulted in some weird DTF numbers. It is indeed very hard to define rounding a mark on a sphere. Gates almost always work, so I'd say that rounding a mark is similar to sailing through a gate with the mark to be rounded on one side, and some point on the course boundary on the other.

If there is a mark 3px offshore from an island, and only the rounding direction of the mark is specified (nothing about the island), you could indeed round the mark correctly, while 1) not rounding the island or 2) rounding is opposite to the mark. Sol doesn't work with islands that way. If we want to have a course round an island, we place the mark on the island, forcing your to round the entire island.

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Easter Island to Tristan da Cunha 2026

Welcome to the second leg of our RNW series, rounding Cape Horn. This middle-most leg Round the New World, from Easter Island to Tristan da Cunha, is also part of our Ocean Championship, and as such the second race of OCQ3 2026. This race, like the previous race in the RNW series, will be sailed in our revised 'version 2' Imoca 60 Foil. Race #2050
INFO by brainaid.de
Imoca 60 Foil v2 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ3 - RNW - OCCH - SYC
Race starts: Aug 03rd 11:00 Registration Open!
▶ Flash
GO TO RACE

Magical Mediterranean 2026 - Benghazi to Korcula

We return to Antiquity’s Middle Sea for a seventh celebration of all things Mediterranean - fickle winds, history and olive oil. This time we will sail from ancient Benghazi, whence once grain shipped continuously to feed Rome’s urban masses, to the medieval Venetian thalassocracy’s port of Korcula, birthplace of Marco Polo; 700nm in classy Club Swan 50s!
Race #1978
INFO by brainaid.de
Club Swan 50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: MED - SYC
RACE CLOSE: Friday,
August 7 at 2300 UTC.
Race starts: Jul 27th 15:00 Registration Closed

▶ Flash
GO TO RACE

Red Eye 2026 - Georgian Bay

Welcome to the sensational scenic Georgian Bay of northern Lake Huron, the first area of the Great Lakes to be visited by Europeans in 1615, so former SOLer A2R informed us when he designed this geometrically tortuous course of 317nm criss-cross through its island maze. Originally known as Lake Manitoulin, in 1822 the bay was renamed after King George IV after his succession to the throne. This time we’ll take the very flashy Fareast 31R, which hopefully should keep you wide awake!
Race #2051
INFOby brainaid.de
Fareast 31R PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: RED - SYC
RACE CLOSE: Monday,
August 3 at 2300 UTC.
Race starts: Jul 26th 08:00 Registration Open!
▶ Flash
GO TO RACE

Tall Ships 2026 - Stavanger to Aalborg


Welcome to the fourth of four virtual Tall Ships Races in European waters which are concurrently being organized in-real-life by Sail Training International . This fourth race is from Stavanger in Norway into the Skaggerak to a finish off Denmark’s Aalborg and perhaps an Aquavit to toast the adventure afterwards – a final circa 250nm in Sailonline’s classic Clipper 240.
NOTE: Starts and Finishes in tall ships racing are always offshore to avoid conflict with shipping and shipping lanes; online and real-life may not match exactly.
Race #1995
INFO by brainaid.de
Clipper 240 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: TSI - SUPBUD - SYC
Race starts: Jul 25th 16:00 Registration Closed
▶ Flash
GO TO RACE

Chinook Salmon - Canada to Andreanovs


A year after spawning in the upper reaches of the rivers of British Columbia, Chinook Salmon develop the age-old urge, so familiar to SOLers, to go to sea, heading for different parts of the northern Pacific Ocean. This race catches up with a particular school with an instinctive memory for the Andreanov Islands far west on the Aleutian Islands chain, as they depart the Salian Sea between Vancouver Island and the San Juans. It’s 2200nm and we’re taking the 60ft Trimaran, in the hope we can keep up!
Race #2048
INFOby brainaid.de
60ft Trimaran PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: MIG - SYC
Race starts: Jul 21st 11:00 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 Panpyc
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member cdhinman
  7. Sailonline Yacht Club Member rthinman
  8. Sailonline Yacht Club Member ms0689
  9. Sailonline Yacht Club Member BRENTGRAY
  10. Sailonline Yacht Club Member Sax747

View full list

Series

Mobile Client

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

The mobile client