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Board » Technical Support » Volvo 70 polars

Posted by
Hirilondë


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2013-05-07 05:19:01 - Volvo 70 polars
I have to think the speeds for close hauled sailing in the game polars for moderate winds are inaccurate. I am sailing in 11.09 kts of wind and I sail faster at 30º twa than at 40º. I have never seen a polar like this before. I can't believe the boats sail well at all at 30º twa, never mind do it faster than 40º.

Valleys in polars occur at angles where one sail is losing efficiency the another has not gained it yet. I can't imagine that a sail change is called for between 30º and 40º in 11 knts. of wind. I know of no boat that would require a sail change between those angles at any wind speed.
Posted by
Tyger / Robert Neilson


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2013-05-07 06:07:58 - Re: Volvo 70 polars
Hiri - I noticed that to but apparently this has been discussed in the past. From what Jakob says I assume it is a legitimate polar. Very strange though. http://www.sailonline.org/board/thread/2902/vo-70-polars-question-for-jakob/?page=1
“We may have arrived on different ships, but we are all in the same boat now!” Martin Luther King Jr.
Posted by
Tyger / Robert Neilson


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2013-05-07 06:36:04 - Re: Volvo 70 polars
.... more discussion here. http://www.sailport.se/board/thread/1364/vo70-v4-and-vo70-polars/?page=1
Seems as though SOL is using the old polar for this race and not the updated version.
Any other SOL race I have been in with the Volvo 70 boat, the polar has been the VO70-v4.
I wonder if RC and the Techs are aware.

--- Last Edited by Tyger at 2013-05-07 06:39:57 ---
“We may have arrived on different ships, but we are all in the same boat now!” Martin Luther King Jr.
Posted by
Tyger / Robert Neilson


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2013-05-07 07:09:49 - Re: Volvo 70 polars
The VO70 polar on the Blur site would suggest that at 11 knots of wind, the upwind VMG would be about 48 degrees and BS of just under 10 knots.

http://www.blur.se/polar/VO70_polar.txt

Very different to the SOL boat.
“We may have arrived on different ships, but we are all in the same boat now!” Martin Luther King Jr.
Posted by
NZL_Scotsman


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2013-05-07 10:26:12 - Re: Volvo 70 polars
Polar doesn't make sense to me either. I thought this generation of VO70 was quite poor upwind, but the polar suggests it is excellent. It also seems to be faster BS closer to the wind in some moderate tws, which definitely does not make sense.
Posted by
Hirilondë


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2013-05-07 12:41:58 - Re: Volvo 70 polars
New or old, I don't believe what we have is accurate, at least not for moderate winds. The rest of the ranges of both angles and wind speeds looks good, or at least plausible.

If I recall, the highest the 2008 boats could point was 36º TWA. The tendency for ocean racing boats is to give up some weatherly efficiency in favor of greater speeds off the wind. This is because they virtually always race in the favored direction around the world (easterly) or for the passage they make. So it wouldn't surprise me if these boats were not as weatherly as the 08 boats.

What ever we use as polars is an approximation, or the polars of a specific boat as they are all slightly different. But regardless, I can't imagine any of them can sail 30º TWA, nor do I believe they lose speed bearing off from 30º TWA towards 40º at any wind speed.
Posted by
Hirilondë


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2013-05-07 22:09:38 - Re: Volvo 70 polars
That looks much better.
Posted by
NZL_Scotsman


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2013-05-07 23:01:31 - Re: Volvo 70 polars
We have switched to the VO70v4 polar. The older polar seems to have problems with the interpolation.
Posted by
Hirilondë


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2013-05-08 12:22:25 - Re: Volvo 70 polars
Thanks for the explanation and following through on this.

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