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 » VO70-v4 and VO70 Polars

Posted by
Zembu


Users avatar

Posts
41
Registered at
2008-12-15 20:58:27
2009-01-12 14:11:40 - VO70-v4 and VO70 Polars
Question for Kalle as he part answered my chat question (12/1/09). The old VO70 polar had the 9 and 15 knot wind speed lines showing boat speeds greater than the boat speed shown by the 30 knot wind line for TWA from 0 to 30 and 40 degrees respectively. So we could expect that a current wind speed line from above 6 to 15 knots would likely show intermediate boat speed similarly. The new VO70-v4 polar shows boat speeds for all permanent wind speed lines increasing as the wind speed increases for all angles of TWA. So today I was surprised to see the 21.8 wind speed line plotting outwith the 30 knot line for TWA from 0 to 40. I'm sending a screen shot of the polar. Is the new VO70-v4 polar operating correctly?
Attachments
Posted by
jakob


Users avatar

Posts
364
Registered at
2007-09-04 10:05:30
2009-01-12 14:50:16 - Re: VO70-v4 and VO70 Polars
Hi, well my name is not Kalle but I am a also one of the guys behind the game and maybe I can help. Your observations are correct and I understand your question. The colored curves we have chosen to show does not at all have to show maximum boat speeds, it is in fact extremely unlikely. Thus, your observation is correct and the polar might be "fairly ok too" :-) ok?
...one of the guys behind the game...
Posted by
Zembu


Users avatar

Posts
41
Registered at
2008-12-15 20:58:27
2009-01-12 15:38:09 - Re: VO70-v4 and VO70 Polars
Jakob, Thanks for your reply. But looking at your manual, para 1.7 "The boat performance" you imply there that the polar diagram is accurate - e.g. you say "For a certain wind speed and TWA you can read the corresponding boat speed..." Your current response implies that we cannot rely on the boat speed curves you have shown. As I said - the old VO70 polar showed that for lower wind speeds up to 40 TWA we could expect greater boat speed than for the 30 knot wind curve. The new VO70 does not give any indication that the same could occur. Old VO70 attached.
Attachments
Posted by
jakob


Users avatar

Posts
364
Registered at
2007-09-04 10:05:30
2009-01-12 16:10:06 - Re: VO70-v4 and VO70 Polars
Well, two things. 1) The old polar is just that - old. We changed the polar since it behaved a little strangely at low twa:s. The new polar is better in that respect. 2) The actual performance routine in the code is continuous in the sense that the boatspeed can be calulated for all combinations of twa and tws. The graphical representation of that we call the polar is accurate (!) but not showing the boat speed at all combinations of twa and tws. ok?
...one of the guys behind the game...
Posted by
Zembu


Users avatar

Posts
41
Registered at
2008-12-15 20:58:27
2009-01-12 17:43:45 - Re: VO70-v4 and VO70 Polars
Thanks Jakob, I guess I have to accept it. Reason I'm so fussy is that as an Excel exercise, I was trying to build an Excel file to help me get best course, and a fundamental of that has been to make a print of the polar and scale off the data, have the Excel do graphs - get equations from these, enter the formulae into a look up table etc etc. I see from your answer to Frank Putman on 15Mar2008 that you don't give out the tabular data, so there's no point in asking you for it I guess.
Posted by
jakob


Users avatar

Posts
364
Registered at
2007-09-04 10:05:30
2009-01-12 19:42:27 - Re: VO70-v4 and VO70 Polars
Well yes, so far we have not given away the tabulated data. if you are doing the interpolation yourself try to use cubic splines in both twa- and tws-directions to get results resembling mine ;-)
...one of the guys behind the game...
Posted by
Zembu


Users avatar

Posts
41
Registered at
2008-12-15 20:58:27
2009-01-13 16:03:56 - Re: VO70-v4 and VO70 Polars
Hi Jakob,

Thanks again for your advice. I will see what I can do and maybe will email you with results if I think I'm successful.

Best wishes,

Andy

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Skimmer Dragonfly - India to East Africa 2026


In the autumn, when the rains stop and the tourists thicken in Goa and along the north western coast of India, globe skimming dragonfly climb to the skies (up to 1500m) to catch the high-altitude ITCZ winds and glide south west to East Africa. We’ll stay at sea level, where alas the winds will be less predictable, and race them there, the whole 2400nm of the way, in Carkeek 40s.
Race #2062
INFOby brainaid.de
Carkeek 40 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: MIG - SYC
Race starts: Nov 11th 11:00 Registration Open!
▶ Flash
GO TO RACE

Fiji TIMED Race 2026

Welcome to Fiji for this month’s TIMED race. Sail our 90 foot Monohull over the almost 200nm course beginning in Lucala Bay and ending in Labasa in your attempt to turn in the fastest time.
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 #2069
INFOby brainaid.de
PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ4 - TRCH - SYC
RACE CLOSE: Saturday,
21 November at 23:00 UTC
Race starts: Nov 08th 12:00 Registration Open!
▶ Flash
GO TO RACE

Bar-Tailed Godwit - Alaska to New Zealand 2026


Welcome to the autumn return flight of our bar-tailed Godwit, reflecting the bird's annual migratory route. This is the penultimate leg in our migration series. (The concluding leg is coming up simultaneously, 'Skimmer Dragonfly', start on the 11th of November. Not part of the 2026 OCCH). This race, at hand, is the next to last leg of the 2026 Ocean Race Championship. The voyage promises to be not only a test of skill and strategy but an immersive experience in the beauty of the vast Central Pacific Ocean. Join us as we push the boundaries of seafaring prowess on this epic adventure.
Let's fly like a Godwit!
Race #2065
INFOby brainaid.de
GunBoat 90 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
OCQ4 - OCCH - SYC - MIG
Race starts: Nov 02nd 11:00 Registration Closed
▶ Flash
GO TO RACE

Mad Max by Balloon 2026 - Across the Outback


Mad Max Rockatansky doesn’t get to go in a balloon in any of the Legends of the Wasteland, and the Wasteland is not necessarily the Outback of Australia, but Mel Gibson and film director George Miller indubitably are… of Australia, and ballooning as reconnaissance is a main feature of the Mad Max spin-off video game, so here goes: 1500nm in a balloon from somewhere on the edge of the Outback, Goondiwindi, to cross a finish line at Fitzroy Crossing, somewhere on the edge of the Outback!
Race #1974
INFOby brainaid.de
SOL Balloon PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: BOL - SYC
RACE CLOSE: Tuesday,
November 17 at 2300 UTC.
Race starts: Oct 14th 13:00 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 rafa
  4. Sailonline Yacht Club Member rumskib
  5. Sailonline Yacht Club Member cdhinman
  6. Sailonline Yacht Club Member rthinman
  7. Sailonline Yacht Club Member Panpyc
  8. Sailonline Yacht Club Member BRENTGRAY
  9. Sailonline Yacht Club Member brandystrega
  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