Asymetric Spinnaker

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.
GBR13697
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Asymetric Spinnaker

Post by GBR13697 »

I have asked about this a couple of times before, with no response. The only working example in VSK5 is on the ACC and, whilst the BoatParam has been made available, we have no details on how the 3D mesh of this sail is created.
I have tried every permutation I can think of, but I have been unable to get a working asymetric. Could we have some clues please? I assume it is a 3D mesh, because all my attempts at a 2D mesh have remained completely flat, although a fore/aft alignment seems to work. My 3D attempts never align correctly, wherever I place or align the sail and the pivot points. It is obviously difficult to align a 3D mesh fore and aft, and it does not seem to work anyway.
Can anyone tell me how the sail and its pivot points are placed and aligned? Nadeo/Sunburn?
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SpiAsym

Post by TOM2 »

Hello GBR,

The concept is the same like the Spi in VSK4. The BodyAxis is on top of your geometrie but the vertical direction of the Axis must have a Angle in the Sideview. This is the rotation Axis for the Spiasym.

The 3D-Geometrie have the Position for 180° TWA in the 3ds File.

The last step is the config of the Boatparam.xml. You have to modify the Parameters of "Optimal Sail Angles".

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Post by admiral »

SpiAsym

X is lateral
Y is longitudal
Z is vertical

Rotation axis SpiAsym is between head and tack)

BoomSpi origin X ,Y = SpiAsym Head X,Y"

BoomSpi origin is at the front of the mast, the height Z depends on what you want to do with the BoomSpi.

The head of the sail is also attached to the front of the mast. The heads Z is usualy at the top of the mast, can be lowwer with fractional rigs.

The SpiBoom Z depends on wether it will be

a) a SpiAsym flown from SpiBoom aka rotating freely above deck.

b) (UNTESTED) a SpiAsym flown from SpiBoom aressted to the deck, protruding on one side of the front stay (Spinaker Boom used as a bowspritt)

c) an extendable bowsprit protruding from the hull below deck.

BoomSpi rotation axis = X,Y (aka vertical, though it could be usefull to tilt the axis forward in cases as it lowers the tack at tighter wind angles)

For a SpiAsym with a static bowspritt you can use a transparent BoomSpi.

BoomSpi angle = AWA/TWA , BoomSpiAngle an Array wich must be set in BoatParam.xml.
- When a SpiBoom masques for an extendable bowspritt you'll
have to make the BoomSpiAngle 0 at all AWA/TWA
- If the BoomSpi is to be arrested to the deck on either side of the front stay
the BoomSpiAngle has to be a static value at all AWA/TWA

Ofcourse the BoomSpi end connects to the Tack
BoomSpi end (X,Y,Z) = SpiAsym Tack (X,Y,Z)
The origin of the BoomSpi can be outside the body of the BoomSpi (you only need the body you want to see, incase of a bowsprit)

For the BoatParams concerning SpiAsym i rever to the BoatParams.xml of the ACC posted by SunBurn somewhere in this forum.
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Post by maitai »

For a SpiAsym with a static bowspritt you can use a transparent BoomSpi
You can also completely remove it, by putting <Unassigned> as a mesh name.
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Post by GBR13697 »

Thanks all. These are the principles I have been using but, so far, without success. If you have done it this way it must be possible. I will just have to persevere.
If, as Tom says, the "3D-Geometrie have the Position for 180° TWA in the 3ds File", this will be the gybing position with the sail flapping like a flag out in front of the boat. Is this correct?
If so, am I also to assume that SpiAsym is a flat mesh, and that the shape is put in by the game physics?
I think that this may be the root of my problem. I have been unable to make a flat mesh assume any curvature at all in the game. However, I have also been unable to symetrically position an asymetric 3D shape (as you might expect!)
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Spiasym

Post by TOM2 »

Hello GBR,

No, You need a 3d geometrie that looks like your boat sailing with TWA180 not a geometrie that flat out in front of the Boot. :-)

If you don`t find a way to realize the Spi send me a PM (TOM) on VSKFun.com

I give you my Mailaddress and you can send me your Model and boatparam.xml. Its easier to modify your model and send it to you with a small documentation whats wrong.

TOM
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Post by GBR13697 »

I am trying to create an Asymetric with a BoomSpi that rotates around the mast, similar to the ACC.
The pivot point will be at the head of the sail, and will run to the tack of the sail, the tack being where the sail joins the end of the BoomSpi.
This will obvously mean that the pivot line will slope forward along the Y Axis.
I would normally expect this pivot line to be on the Y Axis centerline of the boat, and not to be off to one side. This was the case with a normal spinnaker, where the sail was placed squarely in front of the boat, with the Pivot line running from the head down the centre of the sail, with perhaps a little slope forward.
However, if I place the SpiAsym in the position for 180 TWA, but not in the mid-gybe position, the BoomSpi and the tack of the sail will be to one side, and not on the Y axis centreline of the boat. This will mean that the pivot line will slope off the centreline in the X axis as well as the Y axis. Is this what is meant?
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Post by admiral »

?? phew.. ok let me try... (psst. i know your boat is done :)

- sail pivots along line from head to tack (end of SpiBoom)

- SpiBoom pivots around vertical line at front of mast

- Mesh is build in position where it would be at 180° TWA

The pivot line depends on where the Spi or SpiAsym is, especially the tack, and thus the BoomSpi end. It is only on the centerline when the tack is on the centerline, as with a bowsprit, or a SpiBoom pointing straight ahead.
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Post by GBR13697 »

Hi Admiral - Yes, the Fireball is done, but I am thinking of a 49er. At the moment, I am just experimenting with SpiAsym using the Fireball as a testbed.
What you describe is the same as I believe Tom has been saying. I just can't get it to work in practice, but I will keep trying. Otherwise, I will have to take up Tom's offer.
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Post by admiral »

I just can't get it to work in practice
In practice you will have to elaborate, as it's a bit hard guessing about where you do things different.
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Post by GBR13697 »

The SpiAsym flies on the wrong side of the boat, and gybes around the back of the mast, among other problems!
I have sent it to Tom now. I am sure he will correct it for me.
Thanks all.
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Post by Witch Doctor »

Yikes! the site must have been going really slow.
We have enough youth. What we need is a fountain of smart!
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Post by GBR13697 »

It was going slow, but I had not noticed it post my message 4 times!
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Post by Camster »

:D I deleted 3 of 'em
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Post by GBR13697 »

Cheers Sandy (once!)
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