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Board » Technical Support » Bluewater soft

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Posted by
Joshua_Pig


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2009-09-25 16:58:15
2010-07-20 09:02:09 - Re: Bluewater soft
Hi Exmer,

I still don't understand why I have so much differences between Sol and BW wind... so I tried to make it work for the Chicago-Mckinac race.

1st file shows you what I got with Brain's file, 2nd one with Ugrib file

The 3rd one is what I got after having removed and reinstalled BW entirely... still no improvement !

What can I do wrong ?

Thanks a lot
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Posted by
Exmeromotu


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2008-12-10 15:22:17
2010-07-20 10:58:25 - Re: Bluewater soft
Joshua,

I will look into it. I haven't gone to the Chicago Mac race area yet so I don't know what the weather is like. But I kept doing my Expedition and Bluewater comparison on the Scurry race with interesting results. I used brainaids grib files for both software programs. I modified Bluewaters polars as per Bluewaters manual ( The 2nd TWA in a line is the best VMG upwind angle for that windspeed. The
2nd to last TWA is the best VMG downwind angle for that windspeed). Once again expedition had to be "coaxed" into routing on water with the addition of exclusion zones. Miraculously Bluewater routed over water, and didn't hit any land! I selected the Scurry race at this time because of the upwind scenario and a shift that required navigate close to land to see how each software performed. No human intervention. Bluewater tended to use better upwind angles than Expedition with the Bluewater routed boat getting to Sea Lion island nearly 1 mile directly upwind of the Expedition boat. Expedition liked to point a more into the wind than necessary, however both softwares had strectches with crazy TWA's (25 deg.) Attached is a pic of the comparison. Later today I will do the comparison downwind to see how they perform on the gybing angles. The blue track is the Bluewater boat (Green Onions) the red track is the Expedition boat (Exmeromotu). Both programs interpolated the wind extremely close to the SOL wind.

Cheers
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Posted by
Exmeromotu


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2008-12-10 15:22:17
2010-07-20 11:47:24 - Re: Bluewater soft
Joshua

Your case is a mystery to me! I went to the Chicago Mac race and the weather from Bluewater is pretty much the same as SOL's. Check the attached pics with weather readings at the start mark.

SOL weather at 12 Z on Start Mark: 3.3 kts @ 242
BW weather at 12 Z on Start Mark 3.4 kts @ 243

These are the "cursor" readings at the location.
For Bluewater I used brainaids grib file weather_51_global_gfs_20100720_1030.grb

BW weather reading at cursor is in the picture at the lower right hand corner. SOL weather reading at cursor in the picture at upper right hand corner.

Cheers


--- Last Edited by Exmeromotu at 2010-07-20 11:55:05 ---
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Posted by
sol


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2008-08-14 11:08:14
2010-07-20 13:01:54 - Re: Bluewater soft
Huh - I didn't know that brain's weather was sol weather. It works perfectly for me as well.

A couple of ideas:

Bluewater does strange things interpolating the weather timewise. The default timestep is 3h or so. I don't know how much penalty you pay for reducing this, but anything more than ~10m is going to cause problems.

There are about 6 different places to select zulu time and true North...

Exmer - when you are seeing angles inside VMG in Expedition are they in ()? Most routing allows for a tack or gybe on a leg, which exp indicates with brackets. The twa is the average.

Watch out for the above on polar-hops as well.

Posted by
76Trombones


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2009-08-03 18:04:56
2010-07-20 13:03:43 - Re: Bluewater soft
Argh
Posted by
Joshua_Pig


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2009-09-25 16:58:15
2010-07-20 17:01:43 - Re: Bluewater soft
Thanks again Exmer and 76, I did everything I could imagine to get the right wind, but there is still very big differences between Sol and BW datas...

Did you change something after the installation of BW in the settings for the grib files ?
Posted by
Exmeromotu


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2008-12-10 15:22:17
2010-07-20 20:09:15 - Re: Bluewater soft
Joshua,

Go to the Tools menu on Bluewater, select Preferences, on that window check your time as Zulu time and click Save. I have all my settings and all my inputs are in ZULU time, it just makes it easier. Make sure all your times are in Zulu time on the Route Manager and on your individual routes. Now load a grib file (preferably the one from brainaids site due to its relationship with SOL weather) and verify that the weather matches. The only reason for your weather not matching must be that your date and time are out of whack somewhere as 76T implies. Let me know a day and time that time you are active on the chat so we can work through it.

Regards,

Posted by
NZL_undercover


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2009-07-31 03:29:32
2010-07-20 20:15:28 - Re: Bluewater soft
Hi 76,

What do you mean by Polar Hops?

Here's a picture of Expedition how I have it set up with Brainaides info feeding into it.

Cheers Undercover
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Posted by
sol


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2008-08-14 11:08:14
2010-07-20 20:57:27 - Re: Bluewater soft
We try to avoid sailing in any "dent" on the polar, like the one that typically shows up ~120 between up and downwind sail suits. Last entry on 76trombones.wordpress.com has a quick discussion.

If you are using a 10m timestep and the routing wants you to sail 150 for 5m and 90 for 5m, it'll return 120twa. No blindly following the numbers!

Different software deals with this (and the upwind cases etc) in different ways. Obviously none of the commercial ones are intended for sailing with "perfect" wind, so to-the-second timing isn't really necessary.

That's quite the tactical setup! :)

Posted by
Green_Onions


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2010-05-20 17:29:32
2010-07-20 21:02:27 - Re: Bluewater soft
Sorry It's Exmer didn't notice that 76T had already answered your question UC. Cheers!!

--- Last Edited by Green Onions at 2010-07-20 21:18:30 ---

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