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Polars for Bandit IF


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#1 Kayo

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Posted 09 August 2017 - 02:27 AM

Hi everybody.

 

I am looking for a polar (i think it is the name) for the bandit IF (speed/AWA).

 

Anybody knows if this information is available somewhere?

 

Thx you in advance.

 

Kayo


Kayo

Celtica Team (Kayo & Laured)

"Si me dan a elegir, entre todas las vidas yo escojo la del pirata cojo, con pata de palo,con parche en el ojo, con cara de malo. El viejo truhan, capitan de un barco que tuviera por bandera un par de tibias y una calavera"


#2 vIv

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Posted 09 August 2017 - 04:06 PM

hey Kayo,

A polar chart gives you theoretical speed for a given wind speed across all points of sail, measured as an angle relative to the true wind direction.

Liveskipper, an online sail simulation, provides polar charts for all the boats featured in the game, for all the sails configurations for each boat (e.g. Solent, Staysail, Genoa, Spinnaker, Reacher, Runner...) It is presented in a little tool that lets you see the best sail configuration for a given wind speed and angle, as well as the VMG (see sample below) 

I like it as it is quite educational... You can see how the polar chart shape changes as the wind strength fluctuates.. It is never linear, which means there are important tactical implications in racing conditions regarding bearing and choice of sails...

 

But I havent seen any for the IF...

 

To build such graph, one needs to point in a direction and measure the stabilized speed...

Easiest way to proceed, IMHO, is to point one way (straight West for instance) and have the wind shift gradually by 5º or 10º.

 

A good spot to do so is to start from "Norse Basin" sim... You will have 25 or 30 sims to cross going straight West, enough time to check a fair number of sail points!

A good chart should include mapping for both jib and spinnaker.

I would map out the following wind speeds: 15 knots, 18 kts, 21kts, 11kts. 

When you are done, you can repeat with a crew ;)

An then repeat with autopilot engaged...

 

You will finally know everything about the IF performances. maybe a year from now though ;)

Cheers ;)

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Edited by vIv, 09 August 2017 - 04:13 PM.

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#3 LucyInTheSky Afarensis

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Posted 09 August 2017 - 06:11 PM

A good explanation on polars here: http://www.ockam.com...hat-are-polars/and why they are based in TWA, not in AWA.

But once you have boat speed, TWA and wind speed, you can calculate AWA with the vectorial sum: vector(AWA) = vector(wind) - vector(boat)


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#4 Kayo

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Posted 10 August 2017 - 02:16 AM

Thank you both.

I will start doing some testing, mainly for the downwind. This is where i have a lot of issues. 

Additionally i am wondering as well the impact of the hike in crew. It seems to make a good difference.


Kayo

Celtica Team (Kayo & Laured)

"Si me dan a elegir, entre todas las vidas yo escojo la del pirata cojo, con pata de palo,con parche en el ojo, con cara de malo. El viejo truhan, capitan de un barco que tuviera por bandera un par de tibias y una calavera"


#5 vIv

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Posted 10 August 2017 - 03:35 AM

I dont have much experience sailing the IF with crew, but even hiking solo makes a (big) difference... depending on the strength of the wind, you should position yourself differently to gain those 10th of knots which make the difference on the finish line...

With most races run with stiff winds, everyone is always hiking out to the max, without giving it a second thought, but when you start sailing with less wind, you find out there are subtleties...

And remember, downwind, the boat speed reduces the apparent wind, so it is like sailing with lesser wind...  

 

As you said, you need to experience it by yourself, running some tests... Fair winds ;)


Edited by vIv, 10 August 2017 - 03:41 AM.


#6 Alice8200

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Posted 17 August 2017 - 07:57 PM

I'm working on a polar plot for the IF. Took a test run today and collected 1 700 data points which ended up in about 600 after removing outliers.

 

It will need a few more runs to generate good data.






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