[VSK5] BoatParam.xml

Virtual Skipper 5 offer the possibility to import own boat 3D models.<br>
3D artists and players can now meet here to share models and advices.<br>
Virtual Skipper 5 offre la possibilité d'importer vos propres modèles 3D de bateaux.<br>
Les artistes 3D et les joueurs peuvent maintenant se réunir ici pour partager leurs modèles et conseils.
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maitai
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Post by maitai »

Thanks Diades, that will prove helpful certainly. I am myself using eclipse plus an xml plugin for that.
diades
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Post by diades »

No problem, I have only tested it with the file provided in this thread so please shout if there are any problems. It may also be possible as time goes on to refine it with possible values that are acceptable so that less errors occur.
Liese
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BSCoef

Post by Liese »

Hi all,
I do realize that this thread is quiet old...nevertheless I am starting from (almost) the bottom.

I have Polar Diagrams for the model I want to realize in VSK5.
These Polar data contain Velocity info for following wind strength
(kts) 6, 8, 10, 12, 14, 16, 20
and corresponding Heel data.

I will add my assumption about boat behaviour at 25, 30 and 35 kts.

But HOW DO I INTERPRETATE THE BSCoef data?

Here is my try:
Considering BSCoef(TWS) = f(AWA,OptimalSailAngle-CurSailAngle)
<BSCoefCurves>
<Xs Conv="KnotToMs">5 10 15 20 30</Xs> // <-- Wind force for corresponding coefficients
<Curves2>
<Curve2>
<Xs Conv="DegToRad">25 30 40 50 60 90 120 150 180</Xs> // list of sail angles at TWS = 5 knots
<Curves>
<Curve>
<Xs Conv="DegToRad">0</Xs>// Here it shows that I have no influence of differences [OptimalSailAngle-CurSailAngle] and the BoatSpeed is chosen acc. the Sail Vpp table
<Ys>1</Ys>
</Curve>
<Curve>
<Xs Conv="DegToRad">-5 0 5</Xs> // [OptimalSailAngle-CurSailAngle] for 30° = TWA
<Ys>0.5 1 0</Ys> // at [Opt-Cur] = -5 the VPP will be multiplied with 0 --> 0 kts boatspeed from 5° higher TWA than Opt and 0.5 * VPP if I steer 5° below OptimumTWA.
</Curve>
Are the comments correct?
Before I invest a lot of time...I would appreciate to have a clarification in advance....

Good Winds,
Liese
kiwi_bardy
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Post by kiwi_bardy »

Do you mind me asking what the boat is you are working on?

Just curious to see what is in the pipeline?
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admiral
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Post by admiral »

To lazy to look into the whole BS segment,

but basically there is a predicted velocity (1st curve)
TWS, TWA , Sailangle speed in Knots

aka a TWS and a TWA and a Sailangle give a Boatspeed

BS coeefficient as penalty for deviating from the optimal sail angle. (there are many other curves for BS coefficients aka heelingangle, rudderangle etc)

aka a TWS and a TWA and a deviation from the Sailangle given in 1st curve (above) give a speed factor where 1.00 = 100% and 0.00 = 0%


If you can not know how the boat sails: (Want to make VSK model of a sailing automobile)
Afaik research with "twisted airflow" wind tunnels, should have (be able to) provided some data from which "realistic" theoretical numbers can be predicted. There is some research going on in that area with windtunnels in New Zealend Auckland and i think in Germany Wilhelmshafen.


If you know the boats designer or an owner. (Want to make a VSK model of a real life sail boat)
Empirical data maybe available from any sailboat campaign which plots all data you need. (TWA, TWS, BS, Sail Angle.)

BTW AFAIK rudderangles are not plotted in real life sailing, rudderangle BS coefficients especially shortly applied rudderangles (eg. while turning) are very hard to distinct from other parameters like swell, hull movement etc. You could derive data from known aerodynamic profiles (wing shape) and given angle of attack. (nasa)

If you want your model to be realistic make sure you have smooth curves
with rather more data points then less.

Theoretical derived data from windtunnel models last time i looked was considered to have an accuracy of 25%. If your boatparams can beat that number (25% accuracy) you are a genious.

If you have read this far you should by now be impressed by the amount of work boatbuilders in vsk have put up with to make a vsk boat behave realistically. So make sure you go easy on them when asking updates, features, new models etc :)
Liese
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Post by Liese »

I do not get your point :-)
What is the intension of your answer after Line 6 ?
Up to line 6 - thanks for your help ;-)

I just want to create a boat model.
And I will estimate all relevant data from my experience as soon as I understand the structure of the Nadeo XML file.

Is it right, that the BScoef is not relevant if I sail in Automatic trim mode?
Or do I mix up some things?

Just seen Bardys question before :-)
I will try to create a BALLAD - not much of interest for racers ;-)
(i.e. www.Ballad.de)

Best regards and thanks so far,
Joerg

PS: If anyone knows a 3DSMax guy , who can transform my Ballad from obj file to the required file format for the boatimporter- feel free to send me a PM or email (Liese at vskfun.com)
Rich oot1960
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Post by Rich oot1960 »

This will give you some insight on Polars:

http://www.vsk-aus.com/index.php?option ... Itemid=212

This is a "Explaining XML file" of mine, it is NOT a working XML it is to help explain the in's and out's of an XML.

http://www.box.net/shared/t6nbym9k5o

Good Luck. 8)
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admiral
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Post by admiral »

Is it right, that the BScoef is not relevant if I sail in Automatic trim mode?
Or do I mix up some things?
Automatic trim mode makes no error, hence Boat Speed Coefficent

BSCoef(TWS) = f(AWA,OptimalSailAngle-CurSailAngle)

will tend to 0.

Except for the time needed to adapt the sail trim during course changes. If the Trim delay = 0 then OptimalSailAngle-CurSailAngle will always be 0 and f(AWA,OptimalSailAngle-CurSailAngle) too.

I do not get your point
What is the intension of your answer after Line 6 ?

Bascially to make the model realistic you need realistic numbers for ALL coefficients, and there are much more then your usual VPP curve holds.
So you will have to either guestimate those coeefficients (make inteligent guesses) or you need to know these from experience (sail the model and compare behaviour to the real live boat)

If you have experience with the Ballad you should be able to "guess" all the Boat Speed Coefficients, from rudderangle to heelangle like wise all the other coefficents like for course change, accelaration, behaviour in waves (surfing) etc. etc. etc. etc.

If you have an actual VPP curve then with actual measurements of the boat, shapes of hull and appendages and some scientific data you may be able to derive all the coefficients without having first hand experience of the boat.
kiwi_bardy
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Post by kiwi_bardy »

Liese wrote: Just seen Bardys question before :-)
I will try to create a BALLAD - not much of interest for racers ;-)
(i.e. www.Ballad.de)
Excellent, and thanks for the link. Good luck with the model. I wish more people would pursue models like that - I think the more classes that people actually do their real life sailing on that people build the better.
cotton
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Post by cotton »

There's many ways to use the function, this one has been choosen for nadeo's boat.
Feel free to choose another way.
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