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

Page: First Previous 3 4 5 6 7 8 9 Next Last

Posted by kroppyer Posts 346 Registered at 2010-02-05 15:25:55	2013-10-15 12:48:46 - Re: Performance loss
	I've run some more tests, and sometimes the models predict a value that is so close to the actual one that it's scary, I've seen a difference of 0.000000004 (I might have missed a zero). Looking at my results, I think we have (almost) unravelled the performance recovery model: new_perf = min(100, old_perf + delta_time3/(20abs(boatspeed))) > new_perf and old_perf in % > boatspeed is actual boatspeed (not boatspeed when perf would be 100%) from previous "server jump" in knots > delta_time: time since previous "server jump", in seconds > abs(x) makes x positive > min(x, y) returns the smallest value of x and y. This formula basically translates to "Your performance will increase with 9/boatspeed% per minute, until you reach 100%" The performance loss model that matches the actual values the best, is really close, but no perfect match: if(tack or gybe and old_perf >= 93) new_perf = old_perf (1 - abs(boatspeed)/200)* else if(normal course change and old_perf >= 93) new_perf = old_perf (1 - dTWA/25)* end if > new_perf and old_perf in % > boatspeed in knots > dTWA is the positive difference between TWA before and after the course change, in radians (1 radian = 180/pi degrees) I think the last thing to unravel is what boatspeed to use in the calculation for performance loss while taking/gybing. > new boatspeed if perf would be 100% > old boatspeed if perf would be 100% > new boatspeed if perf would be the the same as before the tack > old actual boatspeed (with performance the same as before the tack) And there's another thing to do with performance loss that I we haven't tried yet: bbq'ing, I'm not sure why we would want to know the exact performance loss after a bbq, but why not? Attached: > Image with actual values, and values as predicted by 4 different models: - model 1: use current boatspeed for tack/gybe-perf.loss-calculation - model 2: use max boatspeed (when perf would be 100%) for tack/gybe-perf.loss-calculation - model 3: like model 1, but performance loss is directly subtracted from performance (instead of multiplying with the (1 - loss) thing. - model 4: like model 2, but same substraction method as in model 3 model 1 fits best. > Raw data, csv file, can be opened with excel Attachments perflog_1.csv (36.7 KB) perf-model-4_1.png (82.1 KB)
Posted by javakeda Posts 73 Registered at 2013-03-01 03:18:22	2013-10-15 14:08:25 - Re: Performance loss
	Kroppyer wrote: >>>>> The performance loss model that matches the actual values the best, is really close, but no perfect match: if(tack or gybe and old_perf >= 93) new_perf = old_perf (1 - abs(boatspeed)/200)* else if(normal course change and old_perf >= 93) new_perf = old_perf (1 - dTWA/25)* end if >>>>> So, just to complete the logic [and make sure that I am following you] ... If the code falls through the IFs above, we are left with: new_perf = min(100, old_perf + delta_time3/(20abs(boatspeed))) And that implements the 93% rule? Can you determine from the data whether the "recovery" code executes before, after, or instead of the "course change" code? Thank you for your work on this.
Posted by Go4iT Posts 124 Registered at 2011-03-14 23:58:15	2013-10-15 15:03:51 - Re: Performance loss
	Looks like it is about time for the SOL developers to change the performance loss parameters! hehehe
Posted by Rod Posts 392 Registered at 2010-06-24 22:30:48	2013-10-15 16:44:33 - Re: Performance loss
	Why? It wasn't supposed to be a secret, was it? However, it does seem somewhat complicated, unless it was derived from actual data gathered from IRL boats. I would question, however the perf loss from a gybe,, which seems too great, UNLESS it involves dropping and re-hoisting a spinnacker. And a mere change of course should not involve a perf loss of any great amount. The rudder is still a good brake, however! I am going to attempt to reduce the math to two ready-reference graphs, one showing perf loss at any angle and wind-speed, the other showing expected recovery and time to add to any DC to compensate for the loss in distance travelled. 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	2013-10-15 17:16:24 - Re: Performance loss
	Why Rod ? Why Indeed ! The Rationale for this hindrance has been expounded on in the previously linked thread. Wrong Speed VMG Posted by Jakob Kuttenkeuler 2009-02-12 "We introduced this performance loss not to punish normal sailing maneouvers but to prevent boats to tack e.g. once every minute during hours just to ride on a tws that optimizes vmg. The performance loss implementation succeeded in preventing that behavior and is as stated above not a problem for normal maneouvers." But please don't let me stop anyone from actually going to the source material and reading it for themselves as there are even more useful tidbits to be gleaned should one choose to do so. There is merit in spending an equal amount of time reading these Forums as is devoted to contributing in them. None so blind
Posted by javakeda Posts 73 Registered at 2013-03-01 03:18:22	2013-10-15 19:52:44 - Re: Performance loss
	A2R: Thanks for the link to that thread. To think that the PERF formulas have been sitting on the forum since 2009! Ya think we need a search function for this puppy? Or, as you suggested, ya think we need to RTFF? (Note: Those who know me as an avid fan of MAD Magazine will recognize that the first 'F' in the acronym above stands for 'Furshlugginer'.)
Posted by A2 Posts 347 Registered at 2009-10-26 00:39:42	2013-10-15 20:18:38 - Re: Performance loss
	NSA recommends using Google for this purpose site:http://www.sailonline.org/board/ "performance loss" yeilded only only 9 hits when I went looking for it. Today there are 11. Took about all of 20 minutes to find the good stuff. Time well spent considering. None so blind
Posted by kroppyer Posts 346 Registered at 2010-02-05 15:25:55	2013-10-15 20:28:49 - Re: Performance loss
	Performance Recovery new_perf = min(100, old_perf + delta_time3/(20abs(boatspeed))) > new_perf and old_perf in % > boatspeed is actual boatspeed (not boatspeed when performance would be 100%) from previous performance calculation. Speed in knots > delta_time: time since previous performance calculation, in seconds > abs(x) makes x positive > min(x, y) returns the smallest value of x and y. This formula basically translates to "Your performance will increase with 9/boatspeed% per minute, until you reach 100%" Performance loss if(tack or gybe and old_perf >= 93) new_perf = old_perf (1 - abs(boatspeed)/200)* else if(normal course change and old_perf >= 93) new_perf = old_perf (1 - dTWA/25)* end if > new_perf and old_perf in % > boatspeed is the boat speed after the tack, calculated using the old performance. Speed in knots > dTWA is the positive difference between TWA before and after the course change, in radians (1 radian = 180/pi degrees) I believe performance loss only kick in when a command is executed, or when the boat tacks or gybes (when you are sailing cc trough a windshift, your performance drops when you gybe/tack) I think performance recovery is also active in the "server jump" that performance loss is calculated. But the command to change course can be at the start of the server jump, or at the end, or somewhere in between. I'm not sure what boatspeeds are used how in the recovery formula in the same jump performance loss is calculated. I think we have reach the limit now, the server jumps limit us from being more accurate, and I think it's not really of any use to be able to predict performance more accurate. I will, when I caught up with other things I should've done, implement this performance model in my program spinnacer, so that calculations with performance will be easier to do. --- It might be interesting to think of tricks with this model. hmm did his trick with the gybe, but I'm sure there's more: - a 100.3 degree course change will cause 7% performance loss. So when you need to do a sharper turn (without gybing/tacking) you can turn 105 degrees first (perf<93%), and directly after that the rest of the turn (perf does not drop anymore than those 93%) - Performance loss is smaller when your performance is not yet at 100%, but you're faster when you wait for your performance to reach 100% (sailing two times 5 minutes with average performance 98.5% is faster than sailing 10 minutes with an average performance of 97.2%). But what if your perf is lower than 93%, it's of course better to do it at that moment, as it won't do anything with your performance. And then there's an area in between, where part of the perf. loss could be "absorbed" by the 93% rule. - Tacking, and then turning to the right course is extra performance loss, if you tack to the right course in one go, it faster, unless boat speeds differ much.. It's getting complicated.. - It in light winds, it might be better to do two tacks/gybes instead of one course change. Since tacking/gybing doesn't result in a big drop in performance when sailing slow, while a course change always has the same performance drop. - etc.. etc.. I think we have unravelled the model and calculations, now comes the hard part: how to use it in our advantage Anyway, with this we can at least do better calculations for DCs/routing
Posted by Go4iT Posts 124 Registered at 2011-03-14 23:58:15	2013-10-15 23:15:49 - Re: Performance loss
	A2R said @ 2013-10-15 20:18:38: NSA recommends using Google for this purpose site:http://www.sailonline.org/board/ "performance loss" yeilded only only 9 hits when I went looking for it. Today there are 11. Took about all of 20 minutes to find the good stuff. Time well spent considering. Tried that as a search engine in Google and got '404'. What am I doing wrong? --- Last Edited by Go4iT at 2013-10-15 23:16:35 ---
Posted by A2 Posts 347 Registered at 2009-10-26 00:39:42	2013-10-15 23:29:08 - Re: Performance loss
	Go to Google; In the Search bar site: followed without any space by the url of this board then your search terms after that You can also go to the link at the bottom of the Google search page and click the link that says "Advanced Search" There are boxes there to do the same thing, so when you hit search look at how Google has arranged the same business in the Search bar for you. --- Last Edited by A2R at 2013-10-16 00:12:13 --- None so blind Attachments Site_Search.jpg (694.1 KB)

Page: First Previous 3 4 5 6 7 8 9 Next Last

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Manilla to Calbayog 2024

After six years, we welcome you to the race created by sassy63 for the second time. He takes us to the Philippines to race around islands on a 380 nm course. We sail the Italia 14.98 and in Calbayog we'll enjoy our well-deserved Palatan dish and drink it with San Miguel.
Race #1803
INFO from brainaid.de
Italia 14.98 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ2 - ARCH - SUPSOL - SYC
Race starts: Apr 22nd 17:00 Registration Open!

▶ Flash

GO TO RACE

Jakob's Birthday BBQ Race 2024

Sailonline had two founders and Jakob, the more senior of the two, has his birthday in April which we always like to celebrate with a race through the Stockholm Archipelago from Revengegrundet Lighthouse to his mooring at Baggensfjärden. Traditionally also, like other celebrations this time of year, this feast has been “moveable”, so on this occasion we will be racing on a Wednesday in one of our latest high-performance 40-footers, the Carkeek 40. Please join us then for this always tricky 30nm race. Grattis på födelsedagen Jakob!
Race #1794
INFO by brainaid.de
Carkeek 40 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Apr 20th 14:00 Registration Open!

▶ Flash

GO TO RACE

Melbourne to Osaka Prelude 2024

Welcome once again to what these days is Sailonline’s almost annual virtual Melbourne to Osaka Yacht Race. In real life, this double-handed 5500 nm race between these two sister cities, one deep in the southern hemisphere, the other high in the northern hemisphere, is run every four to five years, and is planned to be held again in 2025, so this race is a Prelude in partnership with the Melbourne Osaka Cup 2025 organising committee collaborating with the Ocean Racing Club of Victoria (ORCV), and the Sandringham (SYC) and Osaka Hokko (OHYC) yacht clubs. On this occasion, we’ll be racing the well-known First 40, a popular size of boat for a long-distance double-handed race. With the doldrums unavoidably lying across the track, you can expect to be at virtual sea for at least a month!
Race #1669
INFO by brainaid.de
First 40 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Apr 20th 00:00 Registration Open!

▶ Flash

GO TO RACE

St Nazaire Chasse TIMED Race 2024

Welcome to a "chasse" (hunt) from St. Nazaire to La Baule on the west coast of France! This race was designed by SOLer FR_flouflou in 2010. The KER 40 was introduced to SOL in 2016 by SOLer psail, and the Sol-KER was a welcome addition to SOL’s fleet of 40- footers, as it was to the IRL Ker fleet of eponymous - like KERonimo, KukuKERchu and Ice BreaKER. This is a TIMEDrace, so you may RE-REGISTER HERE to try again, after finishing a run. You will have 13 days and 11 hours to show your skill and decision making after the race opens.
Race #1797
INFOby brainaid.de
Ker 40 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ2 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
27 April at 23:00 UTC
Race starts: Apr 14th 12:00 Registration Open!

▶ Flash

GO TO RACE

The Beagle in the Straits of Magellan 2024

Both before and after visiting the Falkland Islands, the Beagle extensively explored the south eastern coast of South America, hither and thither, from north of the Rio Plate to the tip of Tierra del Fuego, but it was not till the end of June 1834 that the ship made it into the Pacific Ocean, transiting via the Straits of Magellan. Online in 2024, the choice is yours - passage the strait or round the cape; 400nm or more in your Class B Tall Ship.
Race #1753
INFOby brainaid.de
Tall Ship Class B PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SVF - SYC
RACE CLOSE: Sunday,
April 21 at 2300 UTC.
Race starts: Apr 09th 13:00 Registration Closed

▶ Flash

GO TO RACE

Cape Town to Auckland 2024

Welcome to the second leg of this Round The World series 2024. It's also the April edition of this year's ocean race championship. The course is the same as the one sailed in 2023, but this year we sail the iconic Swan 65, as suggested in the concluding RTW race last year.
Prepare yourselves for an epic 30-day journey, navigating through the unpredictable waters of the South Seas. It's essential to take care of provisioning to ensure a smooth and enjoyable race experience. With the longer duration, we anticipate plenty of opportunities for camaraderie, competition, and unforgettable memories.
PRIZE: SMPF
Race# 1789
INFO from brainaid.de
Swan 65 PARTICULARS
WX updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ2 - RTW - OCCH - SUPSOL - SYC
Race starts: Apr 01st 11:00 Registration Closed

▶ Flash

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