sailboat polar data

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DOWNLOAD POLAR FILES If you don’t want to create your own polar file, you can download them. If you miss any boat, please contact us at [email protected]

Download polar files here

A polar diagram describes how fast a sailing boat may go at different wind speeds (TWS) and in different angles to the wind (TWA). Every type of boat has its polar diagram (or VPP, velocity prediction program), computed from hull shape, weight, rigging and a sail setup. Seapilot uses the polar diagram to compute the fastest choice of path at a given forecast for wind (and current). The polar diagram is imported to Seapilot as a polar file in text format (.txt, .csv or .pol). The name of the boat type or the specific boat is suitable to use as a name of the file (for instance J80.txt). Here at our website you can get access to polar diagrams for more than three hundred boat types. More are coming with time. You may also find polar diagrams at manufacturers, vendors, class associations and others. If you miss any boat, please contact us at  [email protected]

For more polars, visit jieter.github.io/orc-data/site  where you can find polars for almost any boat.

Polar file formats

A polar file contains a table representation of the polar diagram. You can also get data to your polar file for instance from a measurement certificate, from the maker of the boat or from your class association.

If you don’t have the data in tabular form, but as a diagram, you can at every given TWS do readouts at a number of different TWAs (for instance 30, 45, 60, 90, 120, 150 and 180 degrees).

Choose the format (1 or 2, see below) that best corresponds to the format of the data that you have got.

• Create a new file in Excel.
• Replace blue text with your own numbers, let the black text remain.
• TWS should be true wind in knots.
• TWA should be true wind angle in degrees.
• BSP should be optimal boat speed in knots.
• TWS should be ordered from lowest to highest.
• TWA should be ordered from smallest to biggest.
• If needed, add new lines and/or columns.

In particular for format 1: The first line should indicate the wind speeds (TWS) valid for all following lines. Delete lines 2-3 and the two last if data for beat angle/beat VMG and gybe angle/run VMG respectively are missing. Note that beat and run speed should be given as speed in direction of the wind (VMG), not as boat speed (BSP).

Template Format 1  (non editable)

In particular for format 2: There must be the same number of TWA-BSP pairs in every line. Every TWA should be directly followed by the correpsonding BSP (for the TWS valid for that line).

Template Format 2  (non editable)

When you are ready: remove unused columns and lines. Choose File/Save as; choose File format Text (tab delimited) (*.txt). Use your boat type as the name of the file.

Import polar files to your smartphone/tablet

To provide polar data for Seapilot may be simple, and it may be complicated. Choose an alternative in the following order until you find one that is working.

A. If you have a polar file (with file type .txt, .csv or .pol)

• Send the file as an e-mail attachment to yourself.
• Open the e-maíl on your seapilot unit and tap on the attachment. (On iPad/iPhone furthermore: tap the share symbol in the upper right corner and choose Seapilot as the target for the import.)
• Check to see the message ”Import saved OK” meaning that the file format and the data were correct.
• If the import did not succeed you need to reformat the file (see next section).

B. You find your boat type among more than 300 polars on seapilot.com

• Open a web browser on a PC or Mac and go to seapilot.com.
• Choose Features / Polars and Download polar files.
• Click the desired polar/boat type.
• Open an e-mail agent on the same unit.
• Send an e-mail to yourself with the downloaded polar file as an attachment (you find it in Downloads on both PC and Mac).
• Open the e-mail on your iPad/iPhone/Android unit(s) and continue as described i A 2-4.

C. If you have polar data as a table on paper

• Write these data into one of the Excel templates available om seapilot.com and follow the instructions found there.

D. If you have polar data as a table in .pdf format or similar

• Do as in case C; or copy, paste and edit the data using for instance Word or Excel into a format as described in the next section.
• Save as .txt and go on as in case A.

E. If you have polar data only as a diagram

• Use a ruler and do readings in the diagram for a number of TWSs and TWAs.
• Use for instance Excel to do scaling and save in a template as in case C.

F. If you have polar data for a closely resembling boat

• Do as in case A.
• Correct your polar using the parameters Performance upwind and Performance downwind (see the description of the Auto route menu above).

G. None of the above and cannot get data from the designer, the boat builder, a vendor or the class association

• Download iPolar from App store (at a cost of about 12 USD; Seapilot takes no responsibility for this app).
• Choose the Boat tab and give a name to the boat.
• Under Parameters, record boat’s length, displacement and sail areas.
• Check the polar data created by the program under Polars and Values.
• Tap the letter symbol and send data (will be as a .txt file) to your own e-mail address.
• If you want a spinnaker to be included in your sail setup you must use the two files Main+Jib.txt and Main+Spin.txt to create a new .txt which in every position contains the maximum of the corresponding values in the two other files.
• Continue as in case A.

Beware any error messages when you use the polar file for the first time (see section Autoroute in the manual).

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Boats & Polars

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Polars & Performance

Below is a collection of polar diagram from various sources.

Mostly in numerical format to easily plug into routing software. They’re published here just to play around with. For serious/real use you should get a real one for your specific boat. Also some links to tuning guides and other perfomance related info. Share and enjoy!

• 1D35 ( North , UK , Quantum )
• 606 ( Gransegel , Hamel , North )
• 806 ( trimguide )
• Albin Express ( Sten Bergqvist , Edman , North , Ottosson , UK Syversen )
• Albin Nova ( Blur )
• Beneteau 25 ( North )
• Capri 22 ( Ullman )
• Catalina 22
• Catalina 36
• Dehler 38/Pacer 376
• Drake ( Høj Jensen , North Tuning Guide )
• Etchells ( Doyle , North , Quantum )
• Farr 36 ( Farr Performance Prediction )
• Farr 40 ( Doyle , Farr PP , North , Quantum )
• Farr 395 ( Doyle , North )
• Fenix ( trimguide )
• Finn Flyer 36 Club
• First 34.7 ( Farr PP )
• First 36.7 ( Doyle , Farr PP , North , Quantum / pdf , UK / pdf )
• First 40.7 polar1 polar2 ( Farr PP )
• First 44.7 polar1 polar2
• First Class 8 ( North )
• H-båt ( Edman , Henrik Lundberg . Høj Jensen , North )
• IF ( Edman , North )
• IMX-40 ( X-yachts )
• IMX-45 jib only
• J/22 ( Haarstick , North , Quantum )
• J/24 ( Doyle , Haarstick , Jardine , North , Quantum , Shore , UK , Ullman )
• J/27 ( Ullman )
• J/35 ( Quantum )
• J/80 ( North , Shore , Quantum , UK , Ullman )
• J/105 ( Doyle , North , Quantum , Ullman )
• J/109 vpp-od / vpp-genua ( Doyle , North , North England , Quantum )
• J/120 ( North , Quantum )
• J/122 ( polar + pleliminary IRC cert )
• J/133 ( vpp )
• Landmark 43

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• Melges 24 ( North , Quantum , Ullman )
• Melges 32 ( North , Quantum )
• Mumm 30/Farr 30 polar1 polar2 ( Doyle , Farr PP , North , Quantum + Cookbook
• Nelson-Marek 43
• Olson 25 ( Scot Tempesta )
• Prima 38 ( Quantum Tuning Guide )
• Santana 20 ( Ullman )
• Soling ( Doyle , North , UK )
• Sun Fast 3200
• Sydney 36CR
• Sydney 38 ( North )
• Swan 42 “ClubSwan” ( North , Quantum )
• Swan 45 ( B&G , Hall . North , Quantum )
• Tartan 10 ( Doyle , North , Sobstad )
• Ultimate 20 ( Ullman )
• X-35 polar1 , polar2 ( B&G , North )
• X-99 ( North , X-yachts )
• X-332 ( trimguide )
• X-332 Sport
• Yngling ( Doyle , Høj Jensen , North , Ullman )

Various sources for IMS ratings with VPP-data:

Just for reference I collected a bunch if IMS certificates here .

I also collected lots of IRC numbers, just for reference. Sorted by boat type and sorted by Time Corrector (TCC) .

Pelle Lindell did some excellent comparisons between LYS, IRC, IMS, ORC Club and PHRF: “ Käpp eller rullator, handikapp för seglare – En jämförelse av olika handikappsystem ” + spreadsheet .

Various sources on trim/tuning (Swedish):

• Bodings lilla röda
• Hamel trimtips

Various polars from Sailinline.org .

• Albin Express
• Bavaria 38 Match
• Comfortina 38
• Dynamic 3000
• Finngulf 33
• Grand Soleil 341
• Grand Soleil 37
• Grand Soleil 40
• X-41 ( assy for pole )

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49 Comments

blur » Blog Archive » Polardiagram Dec 18, 2006 @ 12:17

[…] Jag har sammmanställt en del polardiagram för olika båtar här. Kan vara intressant att labba med om man skall byta båt (eller bara på kul). […]

blur » Blog Archive » Wrap Up 2006 - bloggen Dec 28, 2006 @ 22:18

[…] Sökt på Google: vad är det folk har sökt på när de kommer till blur.se? I fallande ordning ‘Maria Cattiva’ (>500 klick), ‘polardiagram’, ‘Tjörn Runt’, ‘Blur’, ‘x-35′, ‘Albin Nova’, ‘Bengt Falkenberg’, ‘Hermanö Runt’, ‘Gotland Runt’ och över 2.000 andra sökord. […]

Trimguider « Aiming First Apr 23, 2007 @ 22:06

[…] Jump to Comments Her er en liste over trimguider på nett. Les og kos […]

Hi, I went to your Web page looking for polar diagram or data for Tartan 10. I found the tuning guides but not the performance prediction. If anyone has one please let me know.

Thanks, Ron

I also am looking for T-10 polars; are any available?

Hi guys, given that there’s a lot of people from Scandinavia here I figured I’d ask the question; Has anyone come accross the polars for the dJUICE VO60 or any of the other last generation VO60’s. Please let me know,

Hi Euro, I have ORC polar data for VO 60 but only in paper format, so I have to rewrite them and then send it to you.

Please, let me your e-mail.

Peter, Det finnes et ferskt IMS-målebrev for IW 31 FIN 6313: http://www.avomeripurjehtijat.fi/certlist/?boat=L-6313&content=pdf

Jeg har plottet polardiagrammet her: http://iw31.blogspot.com/2007/10/s-fort-br-vi-seile-polardiagram-for.html

Anyone with polars for :

Benateau One Ton ?

Would appreciate it.

[email protected]

I’m looking for polars for an Etap 30. I’m hoping someone across the Atlantic that races an Etap 30 might be able to help me.

Thanks! Carl

Please, is it possible the polars for X-40 with genoa 135% or genoa 105%.

Thanks Lakis

Do you know where I can get a polar diagram for Capri 22?

Noen som kan hjelpe med å tyde polardiagrammet for First Class 8?

I am looking for catalina 38 polar diagrams? Or suggestion how to calculate them ?

any one have a polar or tuning guide for a Delher 22/Dehlya 22? thanks

Any polars/performance for the new First 45 with Carbon Rig and deep keel?

Here are some Dehlya 22 polars from IMS VPP (with oversized 36 m2 spinnaker). Displacement and RM are not accurate, but I found the target speeds to be OK.

The boat is very fast for it’s size and age when the wind is 10 kn or less. In stronger winds it’s speed is limited by the short waterline and the hull form that is very difficult to get out of displacement mode.

TWS, BSP, TWA, BSP, TWA 6, 3.79, 43.9, 3.67, 148 8, 4.63, 43.4, 4.61, 150 10, 4.77, 40.5, 4.81, 165 12, 4.85, 39.4, 5.17, 170 14, 4.91, 38.8, 5.52, 172 16, 4.95, 38.6, 5.80, 173 20, 4.98, 39.2, 6.35, 172

Joakim. Thanks for these figures! As a new owner of a Dehlya 22, I’m interested in the target speeds of my boat. But how can I transfer these numbers into a polar diagram? Do I need specific software for this? Do I read it right as TWS = True Wind Speed, BSP = Boat Speed, TWA = True Wind Angle? As I understand the angles, they represent the wind angle producing the maximum boat speed when tacking, and reaching. But what about the other wind angles?

Eric, you can use a spreadsheet like Excel to present these figures in graphical format. You would of course need the “other” angles too, they are found in the boats ORCc/i certificate – maybe Joakim can help you to find one?

Here are all the data for Dehlya 22. Note that TWA includes leeway. Hope you can read it. I don’t see any use of making the polar diagram. Just pick some values from the table and compare.

Wind Velocity 6 kt 8 kt 10 kt 12 kt 14 kt 16 kt 20 kt Beat Angles 44,0° 43,5° 40,3° 39,1° 38,5° 38,2° 38,5° Beat VMG 2,65 3,28 3,58 3,72 3,81 3,87 3,89 52° 4,15 4,89 5,19 5,38 5,48 5,54 5,59 60° 4,57 5,06 5,37 5,58 5,69 5,75 5,81 75° 4,80 5,35 5,64 5,76 5,95 6,07 6,17 90° 5,00 5,49 5,81 6,00 6,10 6,19 6,46 110° 4,91 5,40 5,76 6,07 6,35 6,55 6,77 120° 4,75 5,28 5,67 5,98 6,30 6,59 7,04 135° 4,15 5,00 5,43 5,77 6,07 6,37 7,01 150° 3,52 4,54 5,10 5,49 5,80 6,09 6,67 Run VMG 3,05 3,93 4,59 5,04 5,40 5,69 6,22 Gybe Angles 147,6° 149,5° 164,6° 169,7° 171,5° 172,9° 172,3°

Polar diagram might come handy, if you are intrested in optimising VMC, on longer offshore legs perhaps…

Otherwise, it’s just as Joakim says, pick your target and compare. You will however have to calculate your target speed: TBS=VMG/cos(TWA). And note also, that in the range 0…10 kn the TBS changes quite rapidly, so the wind (TWS) should also be measured accurately.

Thanks a lot! Now I can compare my performance, and check the best course! As you say, the graph is not necessary, It’s the data I need.. It will help me to improve my sailing :-) Eric

Looking at the data, I’m not sure I understand it all :-( TWA 90° means: wind 30°; course my GPS 120° for example? And: if the wind blows 6 kt, and I sail 90° wind angle, I should be able to do 5 kt? I was comparing the data to the Dutch ORC-data I have for Dehler Sprinta ( http://www.watersportverbond.nl/data/8F2_Sailspeed.xls ), and it is suggested that the Dehlya is faster, allthough smaller??? Thanks again for explaining, and helping me! Eric, Senior; but Junior Racer…….

As I said this data was with an oversized spinnaker, which is actually 38 m2 with the ORC formula compared to 33 m2 of Sprinta Sport, which should do 5,0X kn at 6 kn 90 (checked two boats).

Even with a more typical spinnaker of 28 m2 the Dehlya 22 should do 4,89 kn at 6 kn 90. As I said it is a very fast boat for its size and age in light winds. Size doesn’t count that much in light winds and you should be able to sail faster than many bigger boats at 6kn.

Any polars for a mumm 36?

4 or 5 at http://www.ssf.se/tk/pdf/cert2008.asp

Hej! Nu finns det polardiagram för Beneteau First 32s5 här http://www.sailstarck.com/Forum/tabid/53/mid/369/threadid/7/scope/posts/Default.aspx#43

Noone has any polars or tune details for the Beneteau First 45 with carbon rig and deep keel ?

I’m looking for polars for X 40 (1985) with 120% genoa. Who can help me? 11 Lakis: have ever had an answer? Thanks, Frank

I’m sorry, I mean 130% genoa (N° 29)

Thanks for the Dehler 22 info the boat is very quick in light air

Does anyone have polars for Scampi Mark IV.? Help.

Any polars for First Class 10????

Good Morning,

Any polars for a Bavaria 34, long keel, year 2000 manufacture?

Bernard Bodin

Joakim you state that a Delher 22 is difficult to get out of displacement mode could you give an explanation and ideas on optimizing for this condition. thanks

What kind of optimiazation are you talking about? The hull form is not designed for semiplanning speeds, thus it needs big waves to get over 7 kn and still the average speed will be below 7 kn. At least I was newer able to sail faster than 7 kn for more than a couple of minutes or so and that was in ~15 m/s wind with the big spinnaker.

I have not had the opportunity to sail my boat in strong down wind condition but other than a rather fine entry and the stub keel it would appear that it should be quite easy to sail fast down wind. I calculate a D/L of under 150. I was wondering if it is worth raising the keel or using a masthead chute. As this is a rare boat here in the states there is not much in English to go on. I rate in PHRF 234 which is very generous when looking at how fast the boat is in light conditions but not sure if it’s worth the penalty for a larger chute. My boat is rather bare below so no excess weight . Thanks for you response my blog for the boat is http://mysorellina.wordpress.com/ I also race on a Kirby 25

I think the D/L-ratio is close to 200. The waterline is about 5.5 m and the displacement in sailing condition (without crew) likely around 1,2-1,3 tn. I did never put my Dehlya on a scale, but I did quite a lot of queries from the German owners and ended up estimating my Dehlya to 1,3 tn. The official value is 950 kg (or even 900 kg), but it is not clearly stated whether it contains the 200 kg of water ballast. But then using the official WL of 5.2 m with 950 kg ends up close to 200 as well. Thus it is not a light boat! Or have you better knowledge of the displacement?

I don’t know much about PHRF and the fleet is very different here, but picking up some familiar boats 234 sounds very easy to sail to: http://www.ussailing.org/phrf/Tool_%20HI_LO_AVG%20Report.pdf I had a LYS of 1.02, which meant I needed to be 2% faster than Albin Vega, 1% faster than Avance 245 and equal to Beneteau First 24. With that rating I did well under 5 m/s and lousy over 6 m/s.

Sure it might help to lift the keel, but it takes quite long and also reduces stability quite much, thus not very safe when it blows. The mast has quite a long unsupported part and putting masthead chute to that needs some care. The boat does not carry well a big chute when it blows.

Instrument & routing på 5 kvällar | BLUR Jul 25, 2009 @ 22:51

[…] svensk segling och kappsegling Skip to content HomeBoats & PolarsAlbin NovaJ/109Gallery 2007Gallery 2008RacesFærderseilasenGotland RuntSkagerrak TwoStarTjörn […]

Yacht polars | Purepassionbyk Jun 12, 2012 @ 23:02

[…] Boats & Polars | BLURPolars & Performance Below is a collection of polar diagram from various sources. … For serious/real use you should get a real one for your specific boat. […]

Polar Files | RudderNut Jun 25, 2012 @ 16:40

[…] files for various boats can be found on the internet. Here is an example file Catalina 36 from the http://www.blur.se site. The file is text, and though this example has a “.txt” extension Tack Pad […]

Polar Tables - SailNet Community Nov 20, 2012 @ 01:40

[…] Polar Tables Not much help to the OP, but here's a site with quite a list: Boats & Polars | BLUR __________________ ".. there is much you could do at sea with common sense.. and very […]

Understanding the Polar Diagram - Page 2 - SailNet Community Nov 10, 2013 @ 17:53

[…] image while searching Polar speeds, look at manufacturers boat catalogs, on site like this one> Boats & Polars | BLUR On a ORC certificate you will not get a polar but something similar to what Bob Perry posted about […]

Appar sjöväder och prognoser - tips för seglare Mar 17, 2016 @ 09:33

[…] Vilken är högsta farten på alla bogar i alla vindar? Två bra källor till polärdiagram är: http://www.blur.se/boats/ och http://www.orc.org/index.asp?id=1 (där man behöver logga in och ibland betala för […]

I’m looking for Polars for a Cal 35 MK1

Hey Matt, any luck to find them? Im looking for the same Polars

Hi. I´m Fernando from Argentina. I have a J/24 I am looking for the J / 24 polar chart.

Here in Argentina we sail with jib 0% and a maximum crew of 340kg. So, the polars that I need would be with jib and not genoa. Do you have the information? Thank you very much.

Fernando & Crew.

Any information for Sprinta Sport? An E.G. Van derStat one design built by Dehler. Thanks.

Hi just wondering if anyone has come across the polars for Sun Odyssey 389 standard keel

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HOW DO POLAR PLOTS WORK ON A SAILBOAT?

This is an excerpt from the NauticEd Electronic Navigation Course . The course is FREE when you buy the Bareboat Charter Master bundle of courses. Or a la carte, it is only $25. In this section, we are discussing Max VMG – that is the Max Velocity Made Good towards an upwind or downwind destination, the optimum true wind angles to sail, and how to use polar plots to attain these important numbers.

The polar plot is the navigator’s friend. It’s essentially a graph that shows how fast your boat can go in a range of wind speeds and angles. Polar plots are published by each manufacturer for each model of boat with their various sail plans. Below is an example of one particular boat for three true wind speeds; 16 knots, 12 knots, and 8 knots.

HOW TO READ A POLAR PLOT

Move your finger radially along any true wind angle. Stop when you reach the boat performance line associated with the true wind speed you are experiencing. Now, read back around the concentric boat speed circles to the vertical axis and read off the expected performance boat speed (through the water) for that given true wind angle and that given true wind speed. This is the speed at which your boat “should” be sailing and is the speed to which your sail trimmers should try to achieve: the target boat speed.

For example: If you were traveling at 60 degrees off the wind, below would be your boat speeds (through the water) at the various wind speeds:

• 16 knots wind: 8.8 knots boat speed
• 12 knots wind: 8.2 knots boat speed
• 8 knots wind: 7.2 knots boat speed

Observe the following animation. Click on any TWA (true wind angle) on the right and watch:

• The boat icon move to that position on the polar plot
• The wind meter boat speed and TWA

Additionally, what is great about this is that the optimum true wind angle for upwind and downwind legs are easily found by drawing a horizontal line at the highest polar point for upwind and the highest for downwind. In this case, you are maximizing your VMG (Velocity Made Good in the direction of the true wind).

In the plot below, for the 12-knot wind speed example, the max VMG is 5.2 when the boat is properly trimmed, sailing at 7.4 knots through the water and sailing at 45 degrees off the true wind. When sailing at any other angle, the VMG will decrease. If you sail closer to the wind, you are sailing a better angle but your VMG drops along with your boat speed. If you “crack off” the wind a little, your boat speed goes up but your VMG decreases because you are sailing a worse angle. For an upwind course then, the optimum true wind angle for the boat is the highest point the curve reaches because you are maximizing your VMG in the upwind direction.

In this example, when sailing upwind, the optimum true wind angle is 45 degrees (aka Target True Wind Angle ) and the Target Boat Speed is 7.4 knots. Thus, upwind, the navigator calls to the helms person to steer 45 degrees to the true wind and tells the trimmers to trim to attain 7.4 knots of boat speed through the water (not SOG).

Downwind, the optimum (target) true wind angle is 135 deg and the target boat speed is 8.1 knots.

It can be easily determined from the above plot that a downwind heading to a downwind destination is not the fastest way to get to the downwind destination, instead, head off a little and do several gybes. But how much to head off?

In the polar plot example shown, a horizontal line that touches the max boat speed touches at 135 degrees. At this point, reading around the concentric circle, the boat speed is 8.1 knots (assuming it is properly trimmed). Reading across to the vertical line the VMC is 5.7 knots. Comparatively, another sailor that takes a course directly downwind would achieve a boat speed and VMC of 5.0 knots.

In the video below, we sail the boat at specific angles and measure the speed. Then we compare those speeds with the polar plot of the boat. We also show you through a polar plot so that you can exactly understand how one works.

If you’re getting stuck on this a little, don’t worry too much.  The two main points to understand are the optimum upwind true wind angle and the optimum downwind true wind angle.

Some units have built-in example polar plots which you can change and add to match your boat. Although, you might ask your installation specialist to input these for you.

To learn more, register for the NauticEd Electronic Navigation Course ›

### Updated 11/23/2022

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• Yachting World
• Digital Edition

5 tips on developing your polar diagrams to improve your boat speed

• May 25, 2016

To help minimise your losses you need to sail your boat to its target boat speeds. Jonty Sherwill asked designer Mark Mills for his tips on polar diagrams

© ROLEX/Daniel Forster

Sails are fresh, the bottom is clean, there’s a good crew, but you’ve been losing out to similar boats on the downwind legs. The helmsman is sailing as close as possible to the target speeds displayed so why is it not doing the trick?

But who sets these target boat speeds and why do you sometimes fail to match them and at other times do so much better? Most of us are familiar with polar diagrams showing a boat’s potential speed on each point of sailing, but how do you put this information to good use?

For those who sail dayboats or small cruiser-racers without a log or wind instruments, judging speed and sailing angles is largely intuitive, as you observe the progress of other boats around you. An electronic compass and depth sounder may be as high-tech as it gets.

Although this ‘seat-of-the-pants’ ability remains an essential part of sailing larger yachts, the information made available by more advanced electronics provides a far better understanding of how the conditions are affecting performance.

Even if the boat has top-of-the-range instruments and came with a set of polars from the designer or an ORC rating certificate this will be just a starting point. Some budget electronics packages won’t provide target boat speeds from within the software, but this doesn’t prevent you developing your own data.

Either way it seems there’s no quick fix and if someone’s bragging how they always sail faster than their targets, good sailing may be part of it, but it’s just as likely to be that the instruments need calibrating and time should be spent developing the polars.

2. Calibration is king

There is no point in having targets if your boat speed is inaccurate. Good instrument calibration is vital, a daily task on top-level raceboats where crew are looking to get within +/– two per cent accuracy.

It’s unlikely many club level racers get consistently close to this target without regular calibration checks, yet what would people say to a designer claiming targets not even accurate to +/–2%?

The calculations that even the most basic system carries out rely on inputs from the log, compass and masthead wind sensor so the calibrations for each should be checked at least at the start of each season and probably more often.

2. Don’t believe the VPPs

Basic parametric VPPs (velocity prediction programs) often used to generate target boat speeds or ORC handicaps are not particularly accurate when compared with programs used for grand-prix boats using CFD (computational fluid dynamics) to simulate the flow of water around the hull. They may be under-predicting, so don’t be satisfied just because you are ‘sailing to targets’.

Also be very sceptical of comparing new models based solely on targets; you have no guarantee that they reflect the actual boat being considered.

3. Theory to reality

Even if very high-quality, a set of polars can only reflect the computer model they started with, and express it in a set of targets unique to that boat. A different displacement, sailplan, alloy or carbon rig, shallow or deep keel type, or crew weight, will lead to more or less different results.

If the targets weren’t created for your boat and configuration don’t expect too much from them, though they may be a good starting point. Output varies from program to program, and remember they aren’t set in stone, so amend your targets.

4. Good sailing

Even the best polars and instruments cannot substitute for natural sailing ability and, by getting to know your boat, you can build an invaluable guide for the helmsman and trimmers just from your own data.

Having good targets on a laminated sheet in the cockpit can put you in better shape than many more expensively equipped boats. However, eyes out on the racecourse and the competition is often more valuable than eyes down on the instruments.

5. Build your own polar diagram

Either start with targets for something similar or note your own performance expectations based on experience (eg, ‘7.2 upwind in 18kn is about right’) and then start paying attention and updating those numbers as you learn what works better – that’s what the pros are doing.

To establish a basic set of polars for your boat there are tablet apps (eg, iPolar) that can provide a starting point and, by noting actual performance from the log (boat speed, not GPS), a pretty accurate set of targets can be developed during the season for a range of wind conditions and sea state.

Mark Mills is a designer well known for winning designs such as Mariners Cove, Tiamat, Alegre, and production designs such as the King 40 and DK 46. Originally from California, Mills studied yacht design at the Southampton Institute, before launching his first design, Aztec, in 1996. Now based in Ireland, he was named 2009 Irish Sailor of the Year for ‘exceptional achievements’.

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Understanding Polar Diagrams: Sailing by The Number to Maximize Performance

Remember studying for that high school math test and wondering why you had to learn stuff that you would never use again?

Well, surprise! It turns out that math is at the very heart of the sailing experience. Indeed, your Leopard is essentially a massive collection of calculations and equations slicing through the water.

TSW, TWA and VPP

Perhaps the most helpful bit of seafaring math to understand is your Leopard’s polar diagram. A polar diagram shows how fast a sailboat could potentially travel at different wind speeds (TWS=True Wind Speed) and various angles to the wind (TWA=True Wind Angle). Every sailboat model has a unique polar diagram, which displays the results obtained using a  velocity prediction program (VPP) based on the craft’s weight, hull shape, rigging and sail setup.

You can find your Leopard’s polar diagram below: 

Link to Leopard 42 polar diagram

Link to Leopard 45 polar diagram

Link to Leopard 50 polar diagram

The calculations represented in your boat’s polar diagram are a powerful tool for charting a course, estimating passage times, and choosing your sail plan for maximum efficiency.

Choosing the right sail

"The polar is an excellent way to answer the question, should I still be sailing with a jib, or should I switch to a spinnaker or a reacher,” says yacht designer and naval architect Alexander Simonis. “Everybody knows that when you sail downwind, the jib is not that efficient. You go to a spinnaker, an asymmetric spinnaker, a gennaker, as a downwind sail. But when you want to know something more specific, such as, what sail is best on a reach in 25 knots of wind? Or should I switch now to another sail? That’s where the polar can help.”

Following the polar diagram correctly

While a polar diagram can look daunting at first glance, it’s actually pretty simple to follow. 

A polar consists of three data indicators — straight lines, circles and curves. The straight lines that radiate out from the center represent the True Wind Angle (TWA). The circles, which also spread from the center, represent boat speed through the water (STW).

The colored curves, overlaid on the grid created by the straight lines and circles, plot the boat’s predicted speed at various combinations of TWS and TWA. The colors represent different sail plans.

The diagrams are usually divided into upwind and downwind sections.

To read the Leopard 45 polar diagram shown here, start by looking at one of the colored curves — say the blue line, which tracks the mainsail and jib sail plan. As you trace that curve through different TWAs, you can see the predicted boat speed with that sail configuration. At 50 degrees TWA, for example, your Leopard 45 should be making 10 knots. At 120 degrees, the boat should travel at 12 knots.

If you’re not making those speeds, your sails may need to be trimmed.

Keep the data close

The velocity prediction data displayed on a polar diagram can also be presented in table form. One way to get maximum use from data is to laminate a copy of your VPP table and post it near the helm for quick and easy reference. 

According to Simonis, the popularity of using polar diagrams has only recently increased with recreational sailors. Why? Maybe it’s another example of how we’ve come to embrace the power of data in our lives. 

Or maybe math teachers are just doing a better job of selling their subject.

Topics: FAQ

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• Introduction to Polar Diagrams and Optimum VMC
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A polar diagram is a graphic presentation of a sailboat’s sailing performance in various wind conditions. But how do you interpret it?

The same information is also often presented in the form of a table or spreadsheet, which is how the data are originally collected or computed, which in turn is then plotted on a polar diagram as shown below. Programs that compute this data are called velocity prediction programs (VPP).

Continue reading at DavidBurchNavigation.blogspot.com and see a video tutorial below.

David Burch

David Burch is the owner and courses director of the Starpath School of Navigation. An author and authority on weather and navigation, he has more than 70,000 miles of ocean experience ranging from the Arctic ice edge to Tahiti and Australia in the Pacific and from New York to Panama in the Atlantic.

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Take Your Polars Offshore

• By Stan Honey
• Updated: June 3, 2008

In the April ’08 issue we covered how to use your boat’s polar data and target boatspeeds to get to the next mark more efficiently. This month we’ll look at applying the same concepts to an offshore race, where the marks are farther down the course and there are a few more variables to contend with.

Let’s assume you’ve done your prep work and have your target cheat sheet posted in the cockpit and at the nav station. The trimmers and helmsmen are all on the same page. Everyone’s goal is to get to the finish as fast as possible. Your tactician or navigator will have already entered target waypoints into his routing software to best take advantage of projected and current weather conditions.

A common offshore strategy is to maximize your boatspeed to that next “mark.” We call this velocity made good to course (VMC). As it was for your buoy race, the polar curve you’ve gotten from your designer, or with US SAILING’s Performance Package, is a useful graphical tool. You can make a transparency of the polar plot, center it on the boat position on your chart, and align its vertical axis with the wind direction. If you then create a line perpendicular to the rhumb line to the next mark, shift the line until it is tangent to your polar curve. This will show you the wind angle that gives the greatest vector component in that direction. As shown in the diagram at right, this is easy to do with a pair of drafting triangles.

In our example, the rhumbline direction is 60 degrees. The solid black line is perpendicular to 60 and tangent to the polar curve at approximately 69 degrees. This is your heading to maximize VMC. You will not be heading directly to the mark, but somewhat further off the wind. The tactical expectation is that with all the wind shifts likely to occur over the course of this leg, opportunities will arise to compensate for not heading straight to your mark.

Calculation of optimum routes The most prevalent offshore use of polars is in conjunction with gridded binary weather data (GRIB files) to compute the optimum course for your boat. Software packages commonly used for this application include Deckman for Windows, Expedition, and Maxsea.

The polar file used with your routing software should reflect the boat’s actual average performance, including the fact that in light air offshore there is often a sloppy sea state, and in heavy air the boat is often sea-state limited and cannot be pushed above a seamanlike speed upwind in the typical sea-state associated with heavy air. Further, the boat’s average performance includes the full mix of helming skills, not just the performance of the best helmsman. So the polars you use for routing will end up being a separate file from your target polars. The routing polars need to be achievable. If you run a route on a GRIB file, and it turns out the first four days of the GRIB file forecast are accurate, in four days the boat actually needs to be exactly where the router calculated it would be. If your polars consistently overestimate your boat’s performance, and you don’t actually get to where the router calculates you will be at various times in the future, then the calculated route will not be relevant for your boat, and the routing software will be “playing” shifts you will never experience. There are, however, many pitfalls in computing optimum routes from polars. Lets look at them individually.

The weather forecasts (GRIB files) are not perfect. A typical GRIB file from the U.S. Global Forecast System (GFS) will contain forecast data extending out 15 days. The GFS data will be good for the first four days or so, but is less accurate further out in time. The routing algorithms don’t consider this decreasing certainty of the forecasts with extended forecast time. So, if you take a 15-day GFS GRIB file, and compute a transoceanic passage, you may find the router recommends an unconventional route based on the weather pattern that is forecast 10 to 15 days in the future. You know, but the router does not, that the 10- to 15-day forecast is much less certain than the forecast from 0 to 5 days. So the human navigator has to provide “genuine intelligence” (as opposed to the router’s artificial type). The human navigator has to consider the standard meteorological patterns and work out where you want the boat to be five days into the future based on standard climatology. The routing program can do a very nice job of optimizing how to play the near-term weather patterns to best get there.

Routing programs don’t adjust their computed routes for risk. For example, if there is a light-air area (e.g. high pressure) in your way, the routing program will skirt the area of calm very closely to minimize distance sailed. The routing program doesn’t consider that if the forecast is slightly wrong you could be becalmed, whereas sailing a few miles extra distance to position the boat slightly farther from the high could substantially reduce the likelihood of becoming becalmed due to an inaccuracy in the forecast. Some folks address these problems by editing the boat’s polars to artificially reduce performance in light and heavy air. That is one approach, but it has the disadvantage of causing the routing program to work less well in situations where you are forced to sail in light or heavy air. In such situations, if the polars do not reflect the boat’s actual performance, the router will not accurately estimate the boat’s future position and will calculate erroneous routes as a result.

So one of the most helpful uses of polars is the calculation of optimum routes, but the navigator must only use the router as a tool. It is still up to the navigator to consider the risks of the calculated route (very light air or very heavy air), and to consider the increasing uncertainty of the forecast with time. Often the best use of computer routing is for the navigator to calculate the route and then work with the router, trying different starting times, trying different sets of polars, putting in various artificial waypoints to force the route into a different area, and working out the estimated time en route (ETE) for various courses so that the navigator ends up with a clear intuitive understanding of what the weather is doing, what the best route is, why that is the best route, and how much better it is than the alternatives. The objective is for the navigator to completely understand the trade-offs and risks of the various routes in order to make a reasoned decision.

One technique to quickly understand the nature of the optimum route is to set up the routing software to display the forward and reverse isochrones. Take a look at the diagram above; the forward isochrones plot the locus of all the points, for each hour in the future, where the boat could be depending on the path it sails. So the forward isochrones are a family of curves surrounding the boat’s starting location. The reverse isochrones plot the locus of points for each hour prior to the boat’s expected arrival at the destination waypoint. When the forward and reverse isochrones are both plotted, the navigator can tell by inspection how important it is to sail the optimum route. If the forward and reverse isochrones run parallel to one another for a section of the course, for that region there is lots of flexibility in course selection that can be used to take advantage of local shifts or to cover competitors. If the forward and reverse isochrones just touch each other like the center of a figure eight, then according to the routing algorithm, it is important to take the optimum course. In this situation it is critical for the navigator to have a complete understanding of what weather characteristics are causing the optimum route to be so critical.

It is often useful to calculate the heading to sail to achieve the maximum instantaneous closing velocity to the next waypoint. If you know the wind will not change, you are better off pointing directly at the waypoint if on a reach, or sailing your VMG target angles and tacking or jibing if you are on a beat or run. If you are confident in the forecast, then you are better off calculating a route with your polars and the forecast GRIB file. If, however, you are sure that the wind will be shifty but you don’t know how and when, then it makes sense to sail whatever heading achieves maximum instantaneous closing velocity to the mark. This can be the case in light air when the wind is wildly shifty, or in locally turbulent conditions when no forecast makes any sense. You just shrug and do whatever you can to maximize your closing rate to the next mark. The logic is that all else being either equal or unknown, you might as well get as close to the mark as you can.

This calculation of the heading to achieve maximum VMC to the mark with the present wind direction and speed can be done from polar data by many instrument systems, by routing software packages, or can even easily be done graphically using the polar curves that come with the US SAILING Performance Packs. Instructions and examples are included with the Performance Packs.

Even on long offshore legs when you are sailing a computed route from GRIB files, it often makes sense to refer to the optimum VMC angle. If the boat’s heading is not between the direct course to the waypoint and the optimum VMC angle, it is important for the navigator to understand exactly why that is. Having said that, there are certainly reasons to sail courses that are outside the VMC angle; the first third of the Transpac nearly always requires such a course.

Performance assessment As described earlier in this article, when beating or running, the target table provides a good reference for the boat’s performance. If the boatspeed is not very close to the target values, that is a wake-up call to the crew to work out why. Maybe the boat isn’t trimmed correctly, maybe a sail change is necessary, maybe the boat has weed on the keel or rudder, or sometimes there is an unusual wind sheer or sea state causing the discrepancy. To assess performance on a reach you have to use the polar tables themselves. Many instrument systems can display on deck a reaching performance percentage number. This is simply the current boatspeed displayed as a percentage of the boatspeed predicted by the polars for the same conditions.

Just as with the target table when beating or running, this percentage performance number can provide the crew with a rapid indication that the boat is underperforming. If your crew is more able to quickly detect a trim, sail selection, or weed problem than your competitor, you will enjoy a significant advantage. This is particularly true when you are racing offshore or at night and cannot easily compare your performance to nearby similar boats.

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When it comes to boat velocity prediction, the “One Size Fits All” concept does not work.

Avalon VPP is able to calculate precise velocity predictions for your boat. It takes into consideration your boat precise characteristics (additional displacement, propellor type, sail type, etc …) as well as your sailings habits (maximum healing, number of crew, etc.…). Another advantage of using polars calculated with Avalon VPP is that you will then get the forecasted healing and reefing for every route point.

Calculate your boat VPP here

The best weather router on a tablet ?

Avalon vpp video tutorial.

• This system is a real VPP, based on the equilibrium of aerodynamical and hydraulic forces for a pre defined set of TWS (True Wind Speed) and TWA (True WInd Angle).
• Given the complexity of those calculations, it make take up to 30 seconds to produce a set of VPPs. This may increase in case of strong demand. If this happens, we will improve our process to calculate the polars.
• There are about 250 pre-loaded boats that can be used as models. If you do not find your boat in this list, you can pick any other one, close to yours and then change the data and save it as your boat.
• If you do not know the exact data for some fields, you can click on the related « default » button » and the field will be set to a defaulted value. Most of the missing but required information can be measured during the yearly careening of your boat (mostly for keel and rudder measurements).
• As this is the first version of the system, it is possible that the system cannot find some results. If this happens, please notify us and we will investigate why the problem occured.

There are about 470 boat polars (VPP) in the database of polars of Avalon Router. We add polars on demand for the users of Avalon Offshore (mono hull boats).

Those polars are provided free of charge to Avalon Navigation users who are free to use them or not. They are not guaranteed.

If you have your own VPP file(s) you can load them into Avalon. Procedure is described in the users guide.

Bonjour, Si vous avez les polaires de l'architecte, vous pouvez les rentrer dans un fichier csv. Il y a un…

Bonjour, Quel conseil donneriez-vous pour le calcul de polaire ou la saisie de polaire connue (graphe) dans Avalon pour un…

Hello, We have replaced the trial codes by a free version (Avalon Offshore Basic) available on AppStore or Google Play.…

Hi, I would like to try the routing software for races in the Salish Sea in Vancouver area

Love the reality glasses ! So cool to work with it !

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Notes on marine navigation and weather

Tuesday, February 22, 2022

Introduction to polar diagrams and optimum vmc.

A polar diagram is a graphic presentation of a sailboat's sailing performance in various wind conditions. The same information is also often presented in the form of a table or spreadsheet, which is how the data are originally collected or computed, which in turn is then plotted on a polar diagram as shown below. Programs that compute this data are called velocity prediction programs (VPP).

macdavid@iMac Downloads % cat -e etap39.csv  twa\tws,6,8,10,12,14,16,20^M$ 0,0,0,0,0,0,0,0^M$ 46.5,4.61,0,0,0,0,0,0^M$ 45.8,0,5.42,0,0,0,0,0^M$

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Generate your own polars

• Thread starter Jackdaw
• Start date Mar 26, 2018
• Forums for All Owners
• Ask All Sailors

Thats pretty cool, especially for smaller boats without navigation systems. As a data guy my first thought would be to record the wind speed, record apparent wind direction, heading, and speed over ground, etc. With this use regression to report polars with observed data, seems easy for larger boats with electronic installed. The report would be specific to the boat measured, versus an ideal boat.  

BobbyFunn said: Thats pretty cool, especially for smaller boats without navigation systems. As a data guy my first thought would be to record the wind speed, record apparent wind direction, heading, and speed over ground, etc. With this use regression to report polars with observed data, seems easy for larger boats with electronic installed. The report would be specific to the boat measured, versus an ideal boat. Click to expand

Davidasailor26

Very nice. Glad it came out before our boat launches so I can take the underwater measurements. I have the iRegatta numbers so I'm curious as to how they compare.  

Am going to work on this over the season. Thanks for the pointer!  

LeslieTroyer

The yacht devices N2K data logger will also generate polars based on data collected from instruments connected to NMEA 2000 (or SeaTalkNG)  

Jackdaw said: .......BlueJ, ......[blah blah]......will pop up in 20 knots. Click to expand

Will Gilmore

I find this post very interesting, but I'm curious about the data contributed by sog? Wouldn't that throw off the overall view? I mean, unless you're on a currentless lake. -Will (Dragonfly)  

Will Gilmore said: I find this post very interesting, but I'm curious about the data contributed by sog? Wouldn't that throw off the overall view? I mean, unless you're on a currentless lake. Click to expand

LeslieTroyer said: The yacht devices N2K data logger will also generate polars based on data collected from instruments connected to NMEA 2000 (or SeaTalkNG) Click to expand

https://www.yachtd.com/news/plot_polar_diagram_and_wind_rose.html YDVR-03 or YDVR-04.  

LeslieTroyer said: https://www.yachtd.com/news/plot_polar_diagram_and_wind_rose.html YDVR-03 or YDVR-04. Click to expand

Scott T-Bird

This looks great and I hope to get a chance to take specific measurements so I can have polars calculated for my boat. In the meantime, the C&C 27 looks like it is the most similar of any boats listed. It is good to have the default numbers from that boat as a check against my measurements. It looks like the trickiest mesurements to get might be max cross-section area, wetted surface, beam at waterline & displacement. It appears that I have the weight of the lead keel imprinted right on the keel, but light displacement seems like it would have to be from the brochure and the weight of cruising gear is going to be an outright guess. There is another thread talking about fairlead placements for head sails, so I am left wondering why this isn't a factor that should be included for calculating polars. Doesn't upwind performance depend heavily upon correct sheeting angles? Our boat has the fairlead track on the rail, which is far outboard of an optimal position, it would seem. Are these calculations based on the assumption that optimal sheeting angle will be manipulated by inhauls, or whatever, to correct the bad positioning that may have been built into the boat?  

Scott T-Bird said: This looks great and I hope to get a chance to take specific measurements so I can have polars calculated for my boat. In the meantime, the C&C 27 looks like it is the most similar of any boats listed. It is good to have the default numbers from that boat as a check against my measurements. It looks like the trickiest mesurements to get might be max cross-section area, wetted surface, beam at waterline & displacement. It appears that I have the weight of the lead keel imprinted right on the keel, but light displacement seems like it would have to be from the brochure and the weight of cruising gear is going to be an outright guess. There is another thread talking about fairlead placements for head sails, so I am left wondering why this isn't a factor that should be included for calculating polars. Doesn't upwind performance depend heavily upon correct sheeting angles? Our boat has the fairlead track on the rail, which is far outboard of an optimal position, it would seem. Are these calculations based on the assumption that optimal sheeting angle will be manipulated by inhauls, or whatever, to correct the bad positioning that may have been built into the boat? Click to expand

Nice! Now I have to get out the tape measure! With the J/24, it was easy, You are either passing or getting passed. ;-)  

I have a feeling I speak for at least one other person when I ask... What’s a polar?  

It’s a diagram that tells you how fast your boat should go if your as skilled as @Jackdaw  

LeslieTroyer said: It’s a diagram that tells you how fast your boat should go if your as skilled as @Jackdaw Click to expand

Try this @Kermit http://www.mysailing.com.au/cruising/what-use-are-a-yacht-s-polar-plot-for-cruising  

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Navigation Software To serve your performance

Optima, speed polars of a sailboat

The indispensable tool for creating polars actual sailboat..

Show laylines, know the target speed of the boat and the angle that achieves the VMG or calculate a route, it is all possible thanks to Adrena essential navigation polars.

So how do you create and use a polar in Adrena? Several options are available to users…

Calculate the polar

Optima, the calculation tool integrated into Adrena software, uses data recorded automatically during navigation to establish the polar curves of the boat. Rare feature among navigation software, this powerful tool provides excellent accuracy for the display and use of the actual performance of the boat. The calculation process is divided into three steps:

• the load of the tracks used for the calculation. It may be all the recorded data or only a portion (eg only regatta tracks)
• the calculation of the curves by the software and any manual corrections
• the registration of the polar file newly calculated.

We can thus create different files to have a polar “crew” or “cruising solo” or even depending on the sea state (dedicated buttons are provided for this).

Activate a polar

Once the boat’s polar file is created, the crew can immediately use its data contained by activating the polar in Adrena software. In the menu “Tools> Activation polar” software provides the ability to activate a different polar for the start phases and phases of navigation. If you do not have a specific polar for each phase, then the same file is activated in both case.

Theoretical polar and VPP, use them as reference!

In some cases, there is only theoretical polar – or VPP – recovered from the manufacturer or the architect who designed the boat. It is a good base to start racing and get performance values around the potential of the boat. These polars can be activated to be used immediately. When there is not enough tracks recorded to cover all ranges of use of the boat, it will be useful to complete the “holes” left by the lack of data in certain circumstances. Thus the active polar initially based on theoretical data of the polar reference will be refined over the navigation by the speed recordings.

In Optima menu it is possible to define a reference polar, it is not the software active polar. It is used in the window “calculation of polars”, by ticking the box “replace missing data with reference polars” to complete the calculation.

              Theoretical polar                                      Missing data inserted                          Final calculated polar

Difference between theoretical and calculated polar

   Theoretical polar                                          Calculated polar

What if I do not have any theoretical polar ?

When the theoretical polars are missing, last solution is based on mariner’s experience and knowledge of his boat : it is to write its own polar. From an Excel pivot table, you define the boat’s target speeds according to the wind angles and the wind speed.

The table should be as following:

The table should star tat first line, fisrt column of the first sheet of your excel file.

Save your file in text format (tab delimited) ( .txt )

Retrieve in Windows explorer the file and select it. Modify the extension from «  .txt  » en «  .pol  »

Then, you can activate the polar in Adrena.

The description of how to use those tools can be found in the user manual delivered on every ADRENA software CD or in our website in the FAQ .

How Adrena is using the polars?

Laylines display on departure line 

Layline display and VMG heading to waypoints

Performance data display 

Target duration display

Weather routing calculation

Written by Adrena

Adrena is a company providing a large range of products - Octopus, First, Standard and Pro to the world of sailing. Thanks to a complete and progressive offer that fits any level of sailing, our software satisfies the amateur through to professional teams alike.

Create hyper-accurate polars using AI

Polars explained

Boat polars represent the performance of your boat in different wind and wave conditions and are critical to creating accurate weather routing results.

Automated AI Polars

Our new AI Polars reference real-time data to learn the way you sail your boat, to create hyper-accurate weather routing.

Up until now this was limited to the realms of professional navigators. PredictWind now makes it simple and easy to get accurate, personalised polars for your boat. This ensures your boat’s location matches the predicted weather route, resulting in a more accurate forecast.

How it works

Simply plug in the PredictWind DataHub to your boat's instruments and turn on the automatic AI Polars. PredictWind will then track your boat’s real-time data and automatically create an optimised boat polar for your unique vessel and sailing style.

More than just wind

AI Polars also factor in wave conditions (wave height, period & direction) to create a hyper-accurate polar that is a realistic representation of the boat's offshore performance. Accurate polars are critical for giving the most accurate routing on earth.

Night Polars

AI Polars will adapt to the unique way you sail at night. Typically, sailing at night will mean reduced speeds, as we sail more conservatively and it is harder to sail at optimal levels. AI Polars analyses how you sail at night and factors this in to your polar data, providing the most accurate polars for day and night.

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Sailing polar performance.

Polar Sailing Data

How to make polar performance data work for me!

Polar Performance Sailing Suggestions

• Try pre-made tables if available. You can modify them to suit your achieved performance using them as a starting point.
• If no performance data is available you might find a table for another model that is similar to your boat.
• Record your sailing performance as you are out in a variety of conditions - perhaps you can improve the tables by downgrading your pre-made table to reflect your cruising reality (older sails, conservative decisions, to much gear stowed on deck etc)
• Examine “close hauled”. This was one situation where tables seem inaccurate for us. We cannot point as well as theory and tables suggest. We have 4-6 knots on the nose so want to be close on the wind. I tweak all I can but just get 27 degrees apparent. Pretty good I think but nowhere close to what our table predicts. We should make 19 degrees AWA (apparent wind angle) which is 32 true. If we use this with the routing software it will have making unrealistic headway.
• Garbage in, garbage out. The best routing solution from a weather router to software like Predictwind or others will only be able to suggest a good route if they know how fast you will sail in different conditions and headings. With proper polar data these routing services are a great idea (routing Blog to follow!)
• Polar performance data from the boat manufacturer is quite likely to be somewhat optimistic. They are trying to sell boats and show just how well a model could perform IF everything was perfect. This is not how we will sail shorthanded on the ocean with the boat loaded for a 3 week crossing…

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2 Weather Routing Apps Go to Sea

Weather 4d and luck grib apps get a chance to strut their stuff during a sailboat delivery..

During a recent delivery from Punta Gorda, FL to St. Augustine, FL I had the opportunity to compare two routing apps, one of them recently updated—Weather 4D and Luck Grib, which we introduced in our recent report on satellite communication at sea (see “ Weather Routing with Iridium Go ,” May 2020) and one of our favorite routing apps PredictWind. Weather 4D is intended to be a very robust all-in-one program that performs three essential functions; chart plotter, GRIB download/viewer and weather router. As of this review there is no product that performs all these functions.

Half-way through writing this article, Luck Grib notified us of a new version of their software that provides all the same functionality except chart plotter. Instead of evaluating the two products separately, this article will compare and contrast the two, with the noted difference of the chart plotter feature. The best of the two was used on a Punta Gorda to St. Augustine delivery of a Sabre 386. As Capt. Ron of eponymous film fame puts it: “If anything is going to happen, it’s going to happen out there!”

The benchmarks used to evaluate 4D’s chart plotter functions were Navionics and iNavx apps. For GRIB handling and routing, the two apps were compared. Before we get too far along, I need to emphasize this caveat: It is important to remember routing software will never relieve the vessel’s master of the responsibility for planning. The software provides a valuable second opinion.

Loading 4D and LG onto the iPad was straightforward. The challenge is loading 4D’s cartography (charts). First, the cartography is a separate annual subscription. For a NOAA subscription the annual fee is $35. When loading charts, one goes to Global Settings>Navigation>Maps Settings> where there are abbreviations for various chart providers.

Weather routing requires the vessel’s polars, or at least a generic polar that is close to yours. The version of the 4D program we tested had four polars pre-loaded, including a First 31.7, X37, and a Hanse 495. We attempted to load different versions of the polar for my Tartan 33 and had errors.  Because 4D does not include a polar editing feature, we could not adapt one of their polars for our test boat.

LG uses a different approach. From the initial drop-down menu, one selects the “Routing” option. This brings a sub-menu where you define a vessel. We added our boat, then I went to the “Sailing Polars” menu where we imported the same file that was rejected by 4D. Had we not wanted to import the polar, or if we did not have a polar,we could have gone to the “Sailing Polar Diagram Catalog” option. The LG polar catalog lists about 100 different vessels. 

Motoring polar

LG also offers a “Motoring Polar” menu. For those not familiar with the concept of a motoring polar, every boat operates differently under power. Also, when hopping across the bay, you may run at 2300 RPM, but on a crossing you would run at 1800 RPM to save fuel.

The user enters into an input screen the following information, calm air boat speed, boat speed with 25 knots and true wind angle (TWA) of 0, 90, and 180 degrees, and boat speed with winds 35 knots and TWA of 0, 90, and 180 degrees. This importance of this feature was made clear in our sea trial of the product.

Neither LG nor 4D track GPH, or cumulative fuel consumption. The ability to compare that to allotted tankage, would be a great planning tool. For example, if the model forecasts 80 hours of motoring and, based on user input, the vessel burns 0.75 GPH and the tankage is 60 gallons, then you know that either additional fuel is needed for a safety cushion, or you will need to sail slowly.

What We Tested

These abbreviations are not well explained. While we may know our local ones, like NOAA and WaveyLine, one is left to search the Internet to determine what charts the other abbreviations provide. Selecting “NOAA” launches a selection page. I initially selected the charts for Jacksonville to Cape Canaveral for downloading. After 20 minutes I aborted a download.

Thinking that was an anomaly, the area from Cape Canaveral south to Marathon was selected and downloaded. This took 50 minutes. While 50 minutes felt like a long time, it is not an objective benchmark.

To benchmark, the same area of charts in Navionics application was deleted on the same iPad. This removed the vector charts, the sonar charts, and other layers of charts for this area. The area from Cape Canaveral to Marathon area was then selected for downloaded in Navionics. The download took 15 minutes on the same network, that download was over 4 GB of enhanced data that Navionics presents in multiple views. Stated differently, it took less than 1/3 of the time, for significantly more data.

Another download comparison was done versus iNavx. Unfortunately, one cannot offload a section of charts in iNavx, nor can one download a section of the East Coast NOAA charts. So, the entire iNavx app was deleted, re-downloaded and then raster charts for the entire east coast of the US, Puerto Rico and the U.S. Virgin Islands were downloaded. Downloading that entire section of charts took 12 minutes, and the Gulf of Mexico charts took about 5 minutes.

Based on these objective standards, the time to download the 4D charts is excessive. Additionally, the server only offered the older style Raster charts, it is not clear if, or how the new vector charts will be supported. Nor is it clear how often these charts will be updated. From experience, my Navionics and iNavx charts find updates every 30-45 days.

I consider myself fairly techno-savvy, and based on my experience 4D does not follow many of the existing conventions and nor are the menus intuitive. Let’s start with something as simple as going to a waypoint. Normal convention is to move cursor and select the desired location using a button or tapping the screen. After the location is selected, a pop-up menu appears with an option to navigate, or sometimes create route to the selected location. Not with 4D.

As shown in the examples (see page 19 “Familiarization is Key to Using Routing Apps”), the menu structure of 4D is cumbersome. Another example of a design issue is changing the charts.

To change charts, one clicks on the center drop-down menu.

This will launch another drop-down menu. Under the “Display Options” section, one selects “Map.” One would normally expect to see only those maps that have been downloaded. Instead of seeing only those charts that are downloaded, one is offered a selection of all charts that are available in the server. The options are presented in no specific order. Finally, if the user selects a chart that has not been downloaded, the app presents a black screen. It would enhance usability if the drop down only offered downloaded charts.

When 4D was connected to the instruments on my boat via the Vesper WiFi, 4D displayed all the sensor information and AIS targets. Unfortunately, the AIS targets are poorly presented. A long press on a Class B target will display Closest point of approach (CPA), speed over ground (SOG), course over ground (COG) and other info, but not the name of the vessel. Nor does it immediately display if the target is Class A or B.

In the real world, these are significant issues. For example, returning from Bimini, on a quiet night crossing of the Gulf Stream one can reasonably expect to counter at least five large vessels. Especially at night, being able to call a ship by its name is much safer and efficient. Being able to call “ Knock Nevis , Knock Nevis , Knock Nevis . This is the sailing vessel Road Kill on your bow, would you like a one whistle pass?” versus “vessel five miles off my stern, this is the sailboat Road Kill …” (Since Knock Nevis is the largest vessel ever built, I’d appreciate a little more help avoiding collision.)

Because the 4D’s menus are not intuitive, you really need to use the help system to learn it. One example is that onboard my boat, I connected the device to my Wi-Fi. When I got back home and tried the program, a “disconnect alarm” began. One would think that acknowledging an alarm would be under “Navigation>Alarms” menu. It isn’t. Instead it is under “Settings (upper left corner)>Navigation (not the one on the home screen a different one)>NMEA Settings>NMEA Inputs>Depth- missing data alarm

In summary, I was not impressed with 4D’s ability to act as a chart plotter. There are other products out there that are better at this function. But I did not want to dismiss the program altogether.

Luck Grib vs. Weather 4D

Grib downloader/viewer.

The balance of this article will compare 4D versus the newest version of Luck Grib (LG), and discuss the use of gridded binary files (GRIBs), compressed files that contain weather data.

One good test of routing programs is to see how they handle islands and shallow areas. For the purpose of the evaluation I selected from Ft. Lauderdale to North Caicos and then back. Both programs handled the outbound passage well—although LG did offer an option to sail between Eleuthera and Paradise Island. On the return, both routed across the flats south of Andros.

This is where LG sets itself apart from any other product. The user can add boundaries. These boundaries are treated as no-go zones by the routing software. I set boundaries around the shallow areas in the Bahamas. Once these boundaries were set, the program routes appropriately. The value of this feature cannot be overstated.

On a longer passage, I download weather twice a day and update my routing. By having defined boundaries, I am reasonably sure I will not be routed over shallow water or through an island. As previously stated it does not relieve you of the obligation to check that the recommended routing is safe.

Hands down Luck Grib outperformed 4D in routing and ease of use.

Compared to the streamlined operations found on chart plotters, some of the navigation features on apps that we tested were clunky, requiring several steps to carry out basic function. But it becomes easier as you gain familiarity with all the functions.

• Using Weather 4D, to “go to” a location, one launches the application and then taps the icon on the lower left corner to unlock the screen, thereby allowing the user to pan or move the display area (see red arrows). One then moves the screen to find the destination. Then instead of simply tapping on the screen to select a location, one must tap on the crosshairs in upper right of the screen, this will bring down a drop-down menu that allows various options for the selecting tool. For simplicity, I selected “Center of Screen.” Once the desired destination is under the crosshairs in the center of the screen, one then taps on the rose in the upper left to open one of the two “Navigation” options in the program. This brings another drop down menu, on this menu one selects “Go to target.” In fairness, if you do not change any of the options selected, one can simple center the screen on the next destination, click on the upper right and select a new “Go to.”

• This is where Luck Grib app sets itself apart from any other product. The user can add boundaries. These boundaries are treated as no-go zones by the routing software. I set boundaries around the shallow areas in the Bahamas. Once these boundaries were set, the program routes appropriately. The value of this feature cannot be overstated. .

• By closing the weather routing view on Luck Grib, the suggested route was easier to distinguish. This image, sprinkled with wind barbs gives a good view of the planned route. This view clearly shows that swinging east around Cape Canaveral is faster than following the rhumb line for the given current and wind conditions.

Grib downloader/Viewer:

All GRIB downloaders/viewers work equally fast when connected to the Internet. The real challenge is downloading when connected through an Iridium GO device. Both 4D and LG downloaded a Global Forecast System (GFS) GRIB for our Fort Lauderdale to North Caicos passage in about 90 seconds. But, as in any satellite download, you have to be careful about the size of the file, or amount of data requested. If you keep the download under 46kb, downloads are about the same.

Weather 4D required a second weather subscription for ocean current data. Clearly, any routing app will fall short without this data—particularly one that involves a major current like the Gulf Stream, as mine did.

I am also a fan of having two or three GRIBS to review. One is the large pressure picture that lets me see what fronts are coming—in the winter it is the Canadian lows, in the summer it is the fronts from the north and the hurricanes. If a current is a factor in my routing, having a current GRIB is essential. The ability to switch between the latest local weather, the ‘big picture’ pressure and have ocean currents is a huge. Unfortunately, only Luck GRIB supports multiple GRIBS.

A Satellite Tracking App

While not the primary focus of this review, 4D offers a product called iWatchSat for $15. This app is simply a must have for anyone using Iridium satellite communication. This app tracks the Iridium satellite umbrella and shows coverage for your location. You can see the satellite coverage and know the best time to start a download.

Why is this important? Satellite coverage with Iridium is still spotty at times. I’ve found that I can have good coverage at one minute and three minutes later I will lose it. If you use the Iridium network for downloads or e-mail, this app is well worth the $15.

Help Documents

Since these programs are intended to be used when you are well offshore, the ability to access the help document is critical.

Weather 4D downloads their help to Apple Books app. But if you access their help documents offshore, the Apple Books app gives an error. The work-around is easy, simply close the error dialog box. This will then bring you to the help doc. It is fairly well written and searchable. But the developer insists on making the user suffer through various videos to get answers.

The video is well done, but the speaker speaks slowly and clearly. For example, if one wants to find out how to set a way point, there is no simply list as appears in this article. I admit that because the program does not follow many conventions, the video helped. But there should be a well written text explanation for easier reference. Sometimes, when things are getting weird offshore, we don’t have time or the quiet environment to listen to a video.

Luck Grib uses a hybrid approach. The help document for the routing module can be fully downloaded. In addition, the program has question marks “?” or help tips embedded in the program. This multi-level system works. Because the program is fairly intuitive, there is little need to access the help documents. One criticism of LG’s help documents is that the help document only tell how to use the program. It does not explain how best to leverage its features.

As the computing ability of tablets increases it is possible to do more on them. LG is an extremely robust program packed with features. But the iPad’s screen is still only 10 inches. The program returns extremely useful data, but some of it gets lost in a busy screen.

Only by being “out there” using the program 2-3 times a day to recalculate the route that I became proficient at using it. These lessons are discussed below.

Based on my at the dock trials, I decided to use Luck Grib to route my delivery. The sea trial was for a Sabre 386, for which I’d need polars.

Since LG did not have the Sabre 386 polar, I selected the pre-loaded polars for a Tartan 37. If I wished, I could have modified that polar by entering data in the editing tool. The curmudgeons are saying “huh some test”. Well they are almost correct.

When the owner asked for my Punta Gorda to St Augustine float plan, it was generic.  The plan called for us to go out Boca Grande Pass, south to the west end of the Moser Channel, then to Marathon and north to St. Augustine. For the Marathon to St. Augustine leg my plan was pass just north of Sombrero Key Light and follow Gulf Stream to Lake Worth, head for a point 5-10 miles off Cape Canaveral and enter St. Augustine Inlet. As always, my float plan was ‘subject to weather’.

The Motoring Polar

On the actual delivery, the winds were intermittent and light. Not exactly what one would expect to be a good test of a routing software for a sailboat. But, Luck Grib uses a motoring polar, a sailing polar, the downloaded wind GRIB and the downloaded current GRIB to develop it’s routing. The software’s ability to merge all that data was impressive.

To review, the motoring polar (see page 18) uses the “speed in calm wind” as its baseline. I determined the approximate speed the boat will make with a modest fuel consumption. Then I estimated what speed the boat will make as the wind picks up. This is not precise. Through careful logging, a vessel owner could develop an accurate motoring polar. But for a delivery guy, this approach works.

Because the winds were so light, and because I factor in a large cushion, we ran at a fuel sipping 1600 RPM for all but the last six hours of the run. Even at this slower speed, we completed the Marathon to St. Augustine leg in 2 days 4 hours. When we apply this time to the shortest course over ground distance of 360 nautical miles, our ‘effective average velocity,’ which sailors call velocity made good (VMG), was 6.67 knots at 1600 RPM. Not too shabby!

How did LG do that? The program takes data from the sailing polar, the motoring polar, the Ocean Current GRIB and the GFS GRIB and then develops the most efficient routing.

Using GPX Data

The next step in using a routing software is applying the result or following the route. It is possible to export the LG route as GPS exchange format (GPX) data, download the GPX data to the chart plotter, and then have the chart plotter direct the autopilot. If the iPad or Mac is integrated into the boat’s data network, this is fairly easy. Without having your iPad or Mac fully integrated to the vessel’s chart plotter and/or autopilot there are several steps that need to be taken. I am not sure the effort is worth the enhanced efficiency.

A more efficient way to use routing software is to follow the concept of the routing. This requires the user to understand the hows and why of weather routing. Understanding weather routing begins with a careful review of the current and wind GRIBs to understand what the program is trying to accomplish. Based on that review, a waypoint is set 4-6 hours ahead of the boat, or at the next major turn, and we lay for that location.  Often reaching that waypoint requires dodging vessels or pop-up storms.

Offshore we download new weather GRIB files twice a day. On coastal runs we download whenever we regain cell coverage. Either at a waypoint, or after a download we move the starting point to the vessel’s current location and run a new routing. In this manner, any inefficiencies are minimized. While purist will eschew this process, on a delivery it ensures we are running as efficiently as possible.

Re-running the routing is simple, click on the location mark on the top-center of the screen, and the vessel’s current location is presented on the display. One moves the routing start point to there, and the APP recalculates your routing based on where you are.

You’ll be surprised how frequently the fastest route is not the rhumb line, or even the route you thought would be the fastest.

The Luck Grib displays windless areas in purple shading. These areas are zones where you can expect to motor. Because our run was a delivery, we motor-sailed the entire run and had speeds of over 9 knots in the Gulf Stream.

This brings us to the summation. What’s on my iPad for a delivery? I will continue to carry Predict Wind as it is the only product that uses the full European Model for weather routing. But, Luck Grib is becoming a very formidable product.

The ability to support multiple GRIBs and recalculate without connecting to the server via satellite is huge. This feature allows us to recalculate using existing GRIBs based on the vessel’s current location, maximizing our velocity made good. Finally, my iPad now carries iWatchSat so I can track the Iridium satellites and only do GRIB downloads or fetch emails during best coverage periods.

The cost for Luck Grib is $25 for the base application, $50 for offshore module that allows for the satellite downloads and $50 for routing. If you do not plan on using the satellite feature the cost is $75 for the product- quite reasonable! If heading offshore $125 is downright cheap

For recreational sailors, the new Luck Grib routing app is an incredible value. Experienced sailors can confirm their routing, and even seasoned sailors can see how what they thought was the best route, isn’t. All of us, including me! Can hone their routing skills by using a weather routing tool such as Luck Grib.

USCG Capt. William Herrmann ( www.uscgmaster.com ) is a delivery skipper and an American Sailing Association instructor.

RELATED ARTICLES MORE FROM AUTHOR

You could start the article by mentioning that the software compared will not run on Windows or Android, and indeed Weather 4D won’t even run on a Mac. This would have saved me the read and interest in the story, and the frustration at having to figure it out. It also would have been great to have at least a sidebar to compare it to the OpenCPN grib plugin (which unlike the products compared runs on a variety of platforms).

You need to check out Sailgrib on Android. I have used it on multiple Ocean races, including winning Annapolis to Newport, using it on my Samsung tab active tablet and comparing to Expedition routing on the boat pc. Very similar routes in each app.

No other program does all three functions?Guess you haven’t checked out Expedition software, which does all three and more. And more better too!

My apologies for the delayed response. I was on a delivery and was told someone was replying to queries.

I just finished an on-line review of Expedition software, as I was going to buy it for my racing and deliveries. Expedition has some unique features that are great tools for racers. While it does provide routing, my reading the Expedition Marine website indicated one had to I port the GRIBs. I did not see where Expedition offered the various models that Predict Wind does. Notably, the full European Model.

If I do buy Expedition it will be for crunching data after a race or perhaps during a race.

But on deliveries, I will still rely on Predict Wind Pro.

Please forgive typo— should be “one had to import the GRIBs.

Contacting Editor to… edit

iWatchSat is an iphone ONLY app. 70% world uses Android. Telling use would be helpful information.

Sorry for the delayed response. I was told that someone was covering these wheel I was on a delivery. I am sorry that there is no Android version. FYI per statista.com 53.66% of the world is on iPhones and 46% on Androids.

In future reviews, I will check to see if Android versions are available

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