Sailonline.org - Online Sailing

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!

Tweets by @sailonline

Board » Technical Discussion » Performance loss

Posted by Rod Posts 388 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 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 Posts 388 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 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 Posts 388 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 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 Posts 238 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 Posts 388 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 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 Posts 262 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:

Migaloo Migration 2020
For many years, SOL has followed the migrations of the Pacific gray whale along the western coast of North America from its northern feeding grounds to its southern breeding grounds off Mexico. Down under in the far opposite corner of the Pacific, Migaloo, the white fella, and his humpback whale kin, exhibit exactly the same (or diametrically opposite) migratory habits between feeding grounds in Antarctic waters and breeding grounds off the coast of Queensland, Australia. We followed Migaloo's springtime track north for the first time in 2019 and this year we repeat the experience, now in 60ft Trimarans. Only 3200 nm. If a whale can do it, so can you!
PRIZE: SMPF
Race #1344
INFOby brainaid.de
60ft Trimaran Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
OCCH-OCQ2-SUPERSOL-SYC
ALT. CLIENT:Classic
Race starts: Jun 05th 17:00 Registration Open!
New HTML5 Client GO TO RACE

A3 2020 Leg 6 - Airlie Beach to Cairns
SOL's gift to AGage's memory is the A3 - Agage's Around Australia Series. This race is Leg 6 of the series - a 295nm sprint in Seacart 30 Trimarans from Airlie Beach, inside the Great Barrier Reef up to Cairns.
Race #1353
INFO by brainaid.de
Seacart 30 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: A3 - SYC
ALT. CLIENT: Classic
Race starts: Jun 01st 18:00 Registration Open!
New HTML5 Client GO TO RACE

SoCal 300 2020

The SoCal 300, raced in the waters of California on the US West Coast is usually one of San Diego Yacht Club's most challenging races meaning that we have our work cut out for us to be competitive in our Santa Cruz 52s. This year, due to #COVID19 the real race won't be running which means that some of the real competition may well find their way to race against us in virtuality!
Race #1349
INFO by brainaid.de
Santa Cruz 52 Particulars
NAM_AWIP WX Updates:
0245 / 0845 / 1445 / 2045
Ranking: SYC
ALT. CLIENT:Classic
RACE CLOSE: Wednesday, 3 June at 2300utc
Race starts: May 28th 19:00 Registration Closed
New HTML5 Client GO TO RACE

Go to race archive

SYC Ranking

View full list

Series

Mobile Client

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

The mobile client