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Board » General Discussion » Real Life Honesty Race question

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Posted by
NOR_Jawik


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2008-08-31 20:55:18
2011-04-14 12:04:54 - Re: Real Life Honesty Race question
Gilles said @ 2011-04-14 08:27:29:
Am I crazy?
No you are not. Fix course on Lat/Lon and no rumbline. I like it.
Posted by
BER_Baggus


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2008-12-26 18:46:10
2011-04-14 14:58:57 - Re: Real Life Honesty Race question
@Gilles & 76 - to be honest, the course is probably too short, only a few hours long. What I was after is what wind direction would be best for our polars. I'll see if I can all the GPS coordinates.
Posted by
76Trombones


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2011-04-14 15:15:21 - Re: Real Life Honesty Race question
It's a good exercise! It's not the same as ocean-racing routing, but the tools are similar. Even without shifts and predictors and gribs and such, just identifying favourable prevailing wind conditions is a useful trick.

Totally doable with a spreadsheet. To make life easier for such things it's helpful to fill the area between VMGs (and any other hollows) so that you don't need to worry about tacking.
Posted by
BER_Baggus


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2011-04-14 20:45:46 - Re: Real Life Honesty Race question
It's totally doable with a spreadsheet, assuming someone has that spreadsheet...... ;-)

The routing software is good, but it would only show you the optimum course for the forecast winds. I want too see what the best wind direction would be so that when, probably in 4 months time, it actually blows from that direction, we can make the best time. If that makes sense.
Posted by
Smo


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2009-05-02 21:49:04
2011-04-15 06:03:52 - Re: Real Life Honesty Race question
Should be quite obvious on just cheking wx no need for routers more tricky to get crew there in right time. And good sailing makes it.

--- Last Edited by Smo Smo at 2011-04-15 06:05:01 ---
Posted by
76Trombones


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2011-04-15 19:57:47 - Re: Real Life Honesty Race question
I was going to show how to do this just with pen and paper, but here's an example spreadsheet. Change the leg angles and lengths. This is both clumsier and more complicated than necessary, but maybe can tell what is going on.

;-)
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Posted by
A2


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2009-10-26 00:39:42
2011-04-15 20:15:00 - Re: Real Life Honesty Race question
I am quite interested in All pen & paper solutions to the various sailing conundrums that encompass navigational exercises.

Please show your work :)

P.S.

When I open the .xls file in NeoOffice I get get a series of #ADDIN? errors for the Spline computation in the field as well as the final Best TWD & Fastest Time



--- Last Edited by Hubert Bonisseur at 2011-04-15 20:22:53 ---
None so blind
Posted by
76Trombones


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2011-04-15 20:33:38 - Re: Real Life Honesty Race question
In words:

Convert your polar from knots to minutes/nm. For each leg, multiply the polar by the leg length and transfer to a plot using your dividers. The curve for each leg is added to the one preceding it. The resulting plot reads time, so your best TWD is the minimum.

Here is the data used in the spreadsheet example - the fastest angle in 12kt wind is ~214 degrees.

Course Leg 1 Leg 2 Leg 3 Leg 4
CC 0 45 270 130
NM 3 2 4 5


1/4 Ton 6 8 10 12 14 16 20
52 4.41 5.21 5.75 6.06 6.23 6.34 6.45
60 4.70 5.48 5.97 6.28 6.50 6.62 6.75
75 4.98 5.85 6.33 6.63 6.77 7.01 7.23
90 5.24 6.01 6.48 6.85 7.13 7.27 7.59
110 5.03 5.82 6.32 6.75 7.14 7.55 8.23
120 4.74 5.60 6.16 6.59 6.99 7.40 8.38
135 4.15 5.10 5.80 6.26 6.67 7.05 7.93
150 3.51 4.47 5.25 5.86 6.30 6.68 7.43

Bangle 43.4 42.0 40.4 40.9 40.0 39.3 39.4
BVMG 2.87 3.48 3.87 4.13 4.28 4.38 4.46

Rangle 146.6 152.9 161.6 167.0 172.9 174.7 175.2
RVMG 3.04 3.87 4.62 5.27 5.81 6.22 6.93
Posted by
76Trombones


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2011-04-15 20:42:54 - Re: Real Life Honesty Race question
When I open the .xls file in NeoOffice I get get a series of #ADDIN? errors for the Spline computation in the field as well as the final Best TWD & Fastest Time
-

Yes the posted example uses a plugin for the interpolation functions and I don't think OpenOffice handles it correctly. Hmm...

There's a cubic spline function posted at oooforum.org. Very much worth looking into for sailing spreadsheets. I used a second function to find the minimum, but there areother ways to do that.
Posted by
Rod


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2010-06-24 22:30:48
2011-04-15 20:49:32 - Re: Real Life Honesty Race question
Duuuuh!!! Now I'm feeling stupid! I even taught coastal navigation for a while in the Navy but I do not have any idea what would be needed to get any info out of your spreadsheet. Hands up! How many SOLers know how to do this?
Sorry 76T, but its got to be simpler than that to help ME.
If it breaks, it's not strong enough--if it doesn't, it's too heavy.

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