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 Support » Extrapolating boat performance

Posted by
thorenj


Users avatar

Posts
3
Registered at
2008-02-26 15:37:52
2013-03-08 14:24:16 - Extrapolating boat performance
Hi all - SOL developers in particular!

As you may have noticed, in the current NYC-SFO race we have had stronger winds than those represented in the boat polar. When I took a closer look at what performance I got in winds of 40 knots or above, it seemed to me that the race server does not extrapolate boat speeds above what can be plotted in the graph in the client. Has anyone else experienced this? If this is an accurate observation, can it be rectified?

best regards,
thorenj
Posted by
Schakel


Users avatar

Posts
183
Registered at
2008-12-19 09:19:00
2013-03-08 23:05:56 - Re: Extrapolating boat performance
Stronger winds don't always translate into higher boat speeds. In 40 knot winds you might want to lower your sails a notch or two.

--
Cheers,
Philip
Posted by
thorenj


Users avatar

Posts
3
Registered at
2008-02-26 15:37:52
2013-03-10 13:24:42 - Re: Extrapolating boat performance
Yes, obviously reefing will be important, but:

a) As far as i know, reefing is already incorporated in the (nature of) polars, the boat speeds on beating wind angles seems to indicate this.

b) The boat speed gets "stuck" to the maximum speed of the polar plot graph. Coincidence?

Since we obviously can't have polars for infinite wind speeds, I believe that extrapolating the highest plotted wind speed will be the most accurate simulation. To improve realism, maybe the extrapolation could in fact be interpolation, but "above" the highest comparing value, to incorporate said reefing and wind angle-dependent factors.

best regards,
thorenj

--- Last Edited by thorenj at 2013-03-10 13:31:57 ---
Posted by
76Trombones


Users avatar

Posts
362
Registered at
2009-08-03 18:04:56
2013-03-10 16:20:08 - Re: Extrapolating boat performance
Many of SOL's more recent polars extend the wind speed range where appropriate, while some of the originals only went to 20 knots. The majority do use 30 knots as the upper limit, beyond which performance is fixed.

Most of the publicly available data that we base polars on stops at 20 knots, so that's definitely a factor.

Practically, for most of our boats the 30 knot curve is already survival conditions. Our best polars do reflect more limited pointing ability/leeway under storm sail, though I'm always a bit surprised at how capable the offshore boats are, and there is less change than you might expect. Downwind is similar. By the time sea states, rigging loads, safe sailing are taken into account very few boats don't "plateau". 30 knots *sustained* is a whole lot of wind!


Posted by
76Trombones


Users avatar

Posts
362
Registered at
2009-08-03 18:04:56
2013-03-10 16:27:50 - Re: Extrapolating boat performance
Three more considerations :)

SOL's polar display used to only go to 30 knots, regardless of how much data was in the polar. Aaron fixed this.

We've made limited use of polar curves that "cross" (as reduced speed higher wind curves would) as there has been concern expressed that the result is confusing.

SOL's interpolation has trouble at extremely wide tacking angles (can work around, but extra care needs to be taken when crafting the polar).

Any effort to "accurise" existing or new polars can count on my full support though! All ears.
Posted by
Sebensa


Users avatar

Posts
70
Registered at
2010-10-06 14:50:36
2013-03-10 16:59:29 - Re: Extrapolating boat performance
I, for one, am so pleased to see that one of the "guru's" of this sailing club, is still watching/alive/interested!
Thanks "76"
R
Posted by
thorenj


Users avatar

Posts
3
Registered at
2008-02-26 15:37:52
2013-03-13 12:06:30 - Re: Extrapolating boat performance
I only have some limited experience working with polars, mainly from my bachelor's thesis in hydrodynamics, but i would suggest something along the lines of:

BS(TWS)=BS(max polar TWS)+(TWS/(max polar TWS))x((max polar TWS)-(2nd max polar TWS))

Hope I got that right... ;-)

/thorenj

--- Last Edited by thorenj at 2013-03-13 12:06:55 ---

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Alicante TIMED Race 2025

Welcome to beautiful Alicante on Spain’s Costa Blanca. Dine on some local tapas and paella before racing your America’s Cup foiling winged-sail AC72 catamaran on this 208nm race out to and around Isla de Formentera returning to Alicante after rounding the mark at Cap de la Nau. There should be some very fast times! This is a TIMEDrace so you may RE-REGISTER HEREto try again after finishing a run. You will have 13 days and 11 hours to test your skill and decision making after the race opens.
Race #1958
INFOby brainaid.de
AC72v2 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ4 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
25 October at 23:00 UTC
Race starts: Oct 12th 12:00 Registration will open soon
▶ Flash
GO TO RACE

Marion Island to Fernando de Noronha 2025

The adventure continues as we launch the next to last leg of the RWW series. This leg takes us from Marion Island to Fernando de Noronha, an island in the world heritage archipelago with the same name, 220 nm off the coast of Brazil. This race doubles up as #7 of RWW and #10 of OCCH. A 4400 nm journey of endurance, strategy and pure adrenaline. The RWW series is as whole, part of the 2025 ocean championship. Get ready for this exhilarating challenge as we set sail on the third to last leg of the 2025 Ocean Championship Series! This leg will be raced aboard the Judel Vrolijk 62, pushing sailors to their limits as they navigate the open ocean. Do you have what it takes to conquer the Southern Atlantic? Join us and put your skills to the ultimate test!
PRIZE: SMPF
Race #1955
INFO by brainaid.de
JV 62 PARTICULARS    
WX Updates:
0430 / 1030 / 1630 / 2230    
Ranking: OCQ4 - RWW - OCCH - SUPSOL - SYC
Race starts: Oct 06th 11:00 Registration Open!
▶ Flash
GO TO RACE

Camel or Balloon - Khartoum to N'Djamena


As there is a lull in the calendar, your PRO has decided to risk an experiment – a balloon race over land, using a workaround to eliminate the recognition of water/land transitions. If it fails, the server may crash, and we abandon PDQ, hopefully after leg 7 of the ABS race to Suez has been decided, and before the start of the 1st OCC of Q4. Camel or Balloon – c 1000 nm from a field on the north bank of the Blue Nile at Khartoum to a field on the north bank of the Chari River at N'Djamena!
Race #1956
INFOby brainaid.de
SOL Balloon PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: none
Race starts: Sep 28th 09:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member vida
  2. Sailonline Yacht Club Member WRmirekd
  3. Sailonline Yacht Club Member KaSToR
  4. Sailonline Yacht Club Member CriticalHippo
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member CollegeFund
  8. Sailonline Yacht Club Member BRENTGRAY
  9. Sailonline Yacht Club Member Sax747
  10. Sailonline Yacht Club Member Panpyc

View full list

Series

Mobile Client

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

The mobile client