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 » Technical Discussion » Performance loss

Page: Previous 1 2 3 4 5 6 7 Next Last

Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-11 01:27:15 - Re: Performance loss
I just did two gybes in a row in the start of the Kergulen timed race. In the first I forgot about the 93% and my perf dropped below 85%. I started the second gybe with a perf of 89% and stepped around in about 4 or 5 steps, completing my gybe at a perf of 90% increasing my perf at each step.
I contend this is vital information that should be known to all, that it cannot be derived by direct observation, or by prior knowledge of how a sailboat performs in reality!
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2013-10-11 13:10:37 - Re: Performance loss
These discussions have occurred in the past but it tends to run in cycles so that when it re-emerges often what was once public knowledge can subside into a quasi state of urban lengend.

Finding these nuggets in this Forum can be a challenge even if you are looking for something that you yourself have posted.

=========================
Wrong Speed VMG

Posted by
Jakob Kuttenkeuler
2009-02-09

(discussing performance loss model)

"Well, the current model determines
if the maneouver is a tack or a gybe
or just a minor change in twa
(dTWA is the twa change).
If (tack or gybe)
{e = 1.0-self.bs/200.0}
else
{e = 1-abs(dTWA)/25.0}.
perf = perf*e.
However if perf<0.93
no further maneouver loss is done. something like that."

--- Last Edited by A2R at 2013-10-11 13:48:19 ---
None so blind
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-11 14:29:14 - Re: Performance loss
Many thanks, A2R!!!!
That is the information that we should have had right at the beginning of this whole discussion. I hope that it will be incorporated in the Manual in a prominent position.
I have inquired about the perf loss problem several times over the last three four years and, until now, never received even a hint of an answer
P.S. I will attempt to generate a diagrammatic representation of this situation for the benefit of those among us who are more comfortable with diagrams than equations.
P.P.S. Now all we need to find out is the rate at which the Performance returns to 100% after a Tack, Gybe, or Course Change.
I do hope someone will post the info---in the meantime I will experiment in the Kergulen screen (there are no good windows in the time remaining.)

--- Last Edited by Rod at 2013-10-11 14:33:17 ---

--- Last Edited by Rod at 2013-10-11 14:41:56 ---
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2013-10-11 14:41:26 - Re: Performance loss
Well depending on your Point of View it was either hiding in plain sight or it was a needle in the haystack, so to speak.

I found it because I went looking for it, plain & simple, as anyone could have done.


None so blind
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-11 14:59:10 - Re: Performance loss
You can only look for things that you suspect do exist. My point is that there is nothing in the performance of a sailboat during a change in course that would lead anyone to suspect that the loss of speed would be reduced by dividing the course change into two steps.
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2013-10-11 15:16:09 - Re: Performance loss
I neither knew that it existed or that it did not exist. Looking is a choice as is not looking. I found more than I expected to, so let's move forward from here.
None so blind
Posted by
captjack1942


Users avatar

Posts
239
Registered at
2008-01-18 03:24:03
2013-10-11 16:32:10 - Re: Performance loss
Rod said @ 2013-10-11 14:59:10:
"You can only look for things that you suspect do exist."
No accounting for Serendipity, eh Rod?
;-)
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2013-10-11 18:25:24 - Re: Performance loss
Relying on Serendipity makes you a "Prince of Serendip". I am no 'prince'...science does not rely on just good luck. It needs observation, reasoning, and experimentation. Good luck may happen---then you win the lottery and don't have to worry about anything except greedy relatives.......
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2013-10-11 18:37:05 - Re: Performance loss
Initiative often succeeds where rationalization cannot.
None so blind
Posted by
WIN


Users avatar

Posts
357
Registered at
2009-07-09 23:32:07
2013-10-11 18:40:38 - Re: Performance loss
ciao ALL my friends ;)

just a little contribution from me on this subject :

I remember a few years ago a french soler discovered that jybing in several steps was reducing the perf loss, so I tried to see how it worked ......I did it once only and never again .

two main reasons for that :

1) by so doing the boat runs a longer course , and some of your perf loss saving is gone already, and the time at lower speed below VMG during the maneuver eats away another portion of the saving

2) ( and this is the main reason ) ....after the jybe your angle towards the next mark will no longer be the same and could be worst .......for longtime.

It is very true that also the contrary of item 2) may occur , but item 1) still stands .

IRL an offshore jybe is " smoothed" not so much for performance , but maily for smoothing the maneuver by the crew and keep the spi flying ......whilst , in-shore jybing around a mark smoothing the jybe could cost a number of positions .

Hope you all accept it as an opinion and contribution ..

ciaooooooooooooo ;) ;) ;)

Piero

PS : I did win quite a number of races in SOL , but never because I smoothed jybing or tacking to reduce perf loss..;)

Page: Previous 1 2 3 4 5 6 7 Next Last

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

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 starts: Jul 27th 15:00 Registration Open!

▶ 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 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 Open!
▶ 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 Open!
▶ Flash
GO TO RACE

Juventud TIMED Race 2026

Welcome to Isla de la Juventud (Isle of Youth), Cuba’s second largest island after mainland Cuba. Known as a haven for pirates, the island was the inspiration for novels “Treasure Island” and “Peter Pan”. The circa 120nm course runs clockwise around the island.
This is a TIMEDrace so you may RE-REGISTER HEREto try again after finishing a run. You will have two weeks to test your skill and decision making after the race opens.
Race #2049
INFOby brainaid.de
The boat for this race is the sporty Mini 6.5p Foil PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ3 - TRCH - SYC
RACE CLOSE: Saturday,
1 August at 23:00 UTC
Race starts: Jul 19th 12:00 Registration Open!
▶ Flash
GO TO RACE

Alaska to Easter Island 2026

Welcome to yet another all-new series. The initial leg of the RNW (Round the New World), Alaska to Easter Island, also part of our Ocean Championship. The first race of OCQ3 2026. This race will be sailed in our revised 'version 2' Imoca 60 Foil. Race #2042
INFO by brainaid.de
Imoca 60 Foil v2 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ3 - RNW - OCCH - SYC
RACE CLOSE: Saturday,
August 1 at 2300 UTC.
Race starts: Jul 06th 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 cdhinman
  5. Sailonline Yacht Club Member Panpyc
  6. Sailonline Yacht Club Member bonknhoot
  7. Sailonline Yacht Club Member rafa
  8. Sailonline Yacht Club Member ms0689
  9. Sailonline Yacht Club Member ita10267
  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