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:

Roma Giraglia Regata 2026

Our eighth race of nine to celebrate all things Mediterranean - fickle winds, history and olive oil – is another buddy-up; this one with the Circolo Nautico Riva di Traiano . Founded in 1984, as the new Traiano yacht Harbour neared completion, the Circola since then has developed into one of the major yachting competition centres in Italy, and next to the 450nm Roma per Tutti (which SOL buddied earlier in the year), the Roma Giraglia Regata is its other headline offshore event. First raced in 2005, the 210nm course takes competitors from Traiano to a rock on the inside of the Ile de la Giraglia off the northern tip of Corsica and back to the Italian mainland for a finish in the bay of Santo Stefano. We’re racing this one in our Class 40!
Race #2058
INFO by brainaid.de
Class 40 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: MED - SUPBUD - SYC
Race starts: Oct 08th 16:00 Registration Open!

▶ Flash
GO TO RACE

Arctic Tern - Greenland to Antarctica 2025

Welcome to the fifth leg of our MIG series. Now it's time to race the Arctic Terns, on their migration from Greenland to Antarctica, 8300 NM. This is also part of our monthly Ocean Championship, and as such the first race of OCQ4 2026. This race will be sailed in our Maxi Trimaran. Race #2061
INFO by brainaid.de
Maxi Trimaran PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230 Ranking:
OCQ4 - OCCH - SYC - MIG
Race starts: Oct 05th 11:00 Registration Open!
▶ Flash
GO TO RACE

Bornholm PYOC


Welcome to the Baltic Sea, where we are about to hold another sprint race. The course runs from the north to the south of the beautiful Bornholm island. There are only two waypoints, the start and the finish so the choice of which side of the island to sail along is up to you. Our Albin 79s will cover a distance of approximately 23 nautical miles.
Race #2064
INFO by brainaid.de
Albin 79 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SPQ4 - SPCH - SYC
RACE CLOSE: Wednesday,
October 7 at 2300 UTC.
Race starts: Oct 03rd 06:00 Registration Open!
▶ Flash
GO TO RACE

Cross the Convergence 2026 - Masirah to Chagos


Having crossed, re-crossed and re-re-crossed the Convergence Zones of the Pacific and the Atlantic, we now face our second crossing of the Convergence Zone of the World’s third great equator-spanning sea, the Indian Ocean, taking us from the channel between Masirah Island and the Oman mainland to the Chagos Archipelago. It’s 1900nm and we’ll be sailing our very fine Archer 78, and won’t mention that both locations (of departure and arrival) are heavily militarized and the why’s and what next’s concerning that – mindful as always of SOL Netiquette.
Race #1988
INFOby brainaid.de
Archer 78PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: CCZ - SYC
Race starts: Oct 02nd 18:00 Registration Open!
▶ Flash
GO TO RACE

Carib Rum Run 2026


Ahoy, ye landlubbers and seasoned salts! Welcome back to Sailonline’s legendary Carib Rum Run, perfectly timed to kick off on International Talk Like a Pirate Day, 19 September!

This year, we command the magnificent Falkun—the ultimate high-tech superyacht modeled after the iconic Maltese Falcon. This 1759nm slalom takes us through the Caribbean’s rum islands to plunder barrels from local distilleries and deliver them to the rum-parched sands of Cancun.

Join SYC before the finish to disguise yer boat with a pirate name for this race only. Hoist the sails, sharpen yer cutlasses, and plot your winning course!
Race #2060
INFO by brainaid.de
Falkun PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Sep 19th 05:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member KaSToR
  2. Sailonline Yacht Club Member CriticalHippo
  3. Sailonline Yacht Club Member WRmirekd
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member Panpyc
  6. Sailonline Yacht Club Member cdhinman
  7. Sailonline Yacht Club Member rumskib
  8. Sailonline Yacht Club Member rthinman
  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