## Manual de Usuario del Sailcut CAD

### Robert Lainé

### Jeremy Lainé

### Joan Gelpi

Translation

Sailcut CAD 1.5.0 - 23 de marzo de 2025

## 1. Introducción

### 1.1. Sobre el Sailcut CAD

Sailcut es un software para el diseño de velas desarrollado para paños planos. El Sailcut se puede usar tanto para velas de cuatro lados tipo cangreja como para mayores y foques Marconi de tres lados.

La primera versión del Sailcut fue desarrollada en 1978 y usada por Robert Lainé para fabricar las velas de su barco "Flying Sheep III", un ¼ Ton IOR. Sailcut ha estado disponible en la web desde 1994 y es utilizado por muchos fabricantes de velas, tanto amateurs como profesionales, para cruceros, regatas y recientemente para barcos de radiocontrol.

Sailcut se basa en una única definición matemática para la superfície vélica que asegura un perfil aerodinámico y uniforme.

### 1.2. ¿Cómo obtener el Sailcut CAD?

Se puede descargar la última versión del Sailcut CAD desde la página principal en http://www.sailcut.com/. También está disponible en binario (compilado) y en código fuente.

### 1.3. Información técnica sobre el programa

Sailcut CAD se ha escrito con la intención que sea transportable. El programa fuente es el C++ utilizando la librería Qt de Trolltech para los gráficos y el OpenGL para la visualización en 3D de las velas. Sailcut CAD se puede compilar y funcionar bajo GNU/Linux, Microsoft Windows y MacOSX.

## 2. Usando el Sailcut CAD

### 2.1. Últimas notas

Al igual que la versión 0.6.5, el Sailcut CAD usa diferentes extensiones para cada tipo de archivo instalado en lugar de los finales con extensión ".xml". Si deseamos abrir nuestras velas creadas con la versión anterior del Sailcut CAD debemos renombrar el archivo de definición de vela así como las extensiones con ".saildef". Al abrir el archivo resultante, todos los archivos se conservarán excepto los datos para el molde.

### 2.2. Preferencias de usuario

#### 2.2.1. Preferencias de archivo

Las preferencias se almacenan en un archivo llamado `.sailcutrc`. Bajo UNIX este archivo se localiza en el directorio raíz y en Windows está en `Documents and Settings\USUARIO`.

#### 2.2.2. Internacionalización

Como en la versión 0.5.5, el Sailcut CAD tiene soporte para la internacionalización. Al arrancar el programa, podemos seleccionar el idioma que nos interese en el menu Ver->Idioma.

## 3. Crear una vela

Cuando iniciamos Sailcut CAD, se presenta una vela por defecto y en la parte superior de la ventana encontraremos menús desplegables. El menú ARCHIVO se usa para cargar una vela existente, GUARDAR los parámetros de la vela y EXPORTAR los paneles desarrollados.

Se puede modificar las dimensiones de la vela utilizando el menú Ver->Dimensiones.

Con el menú Ver->Molde podremos modificar el perfil de la vela.

Y en el menú Ver->Aparejo visualizaremos varias velas con diferentes aparejos.

### 3.1. Pantalla Dimensiones (menú Ver->Dimensiones)

El programa permite diseñar tanto una vela triangular como cuadrangular. La clásica vela Marconi se diseña esencialmente igual que una Cangreja pero con un pequeño puño de driza.

La superficie de la vela se genera desde unas sencillas ecuaciones que definen el perfil en todas las alturas. Dichos perfiles se basan en los extremos de las velas que han sido definidos por la longitud y alunamiento en cada lado y por el twist de la vela. En la ventana "Dimensión" hallaremos los parámetros que definen la vela.

Al pulsar el botón "Calcular" el programa evalúa y visualiza los datos auxiliares. Estos datos aparecen en pestañas de color y que pueden modificarse. Si el color es rojo, significa que el valor excede del límite superior; si es amarillo indica que está por debajo del límite aceptable y debe cambiarse.

Una vez finalizada la entrada de datos de dimensiones, pulsamos OK para visualizar la vela en formato 3D.

#### 3.1.1. Pestaña "Geometría del Aparejo"

El primer paso es seleccionar el tipo de vela con la que vamos a trabajar y entrar los datos que definen la geometría del aparejo y el plano vélico (ver la Figura 1.)

Seleccionar el tipo de vela marcando bulón deseado:

- FOQUE para cualquier vela de proa,

- MAYOR para cualquier vela envergada en el mástil,

- ALA para cualquier tipo de cometa simétrica.

The rig data are used for displaying the sails in their proper relative position with the "rig viewer".

Figura 1. Sailcut plan definition

#### 3.1.2. Pestaña "Dimensiones de la vela"

Aquí es donde se introducen las dimensiones de la vela.

En una vela mayor, el valor mínimo para la longitud de la percha (galleta del puño de driza) es de 5mm. Cualquier valor inferior dará siempre por defecto 5mm. El ángulo de percha viene definido como el ángulo entre el mástil y la baluma que puede ser hasta 90 grados.

El alunamiento del pujamen, la baluma y la percha extiende la vela más allá de su línea recta.

El alunamiento negativo equivaldrá a un hueco en la parte exterior de la vela.

La posición del alunamiento se expresa en porcentaje en el correspondiente lado de la vela calculado desde la parte más baja o más externa del lado.

Figura 2. Sailcut edges definition

Dimensions and angles defining the sail plan are expressed in millimetre and degrees.

Length of the sail sides and diagonal are the 3D straight line distance between the corners of the sail.

The actual length on the finished sail lais on the floor can be slightly longer depending on the shape of the sail. For example, the foot length entered in the screen below is 3600 mm. If the foot camber is null then that will be the actual distance between clew and tack (straight foot) of the finished sail. If a 10% camber is entered for the foot depth, then the actual foot will be the length of the arc which has 10% camber, that is 2.7% longer than the straight line foot length.

Having entered the sail main dimensions you can press on the "Compute" button to obtain additional informations on the sail, like the X-Y coordinates of the corners of the sail, the perpendicular length LP measured from the clew to the luff as well as IRC racing rules width.

The X-Y coordinates of the sail corners are usefull to quickly adjust the data entered. For example if you find that the clew height (Y) is way below or above the height of the tack when you would like it to be leveled, then you can substract or add the difference to the leech length.

#### 3.1.3. "Layout" box

Click on the radio button corresponding to the desired layout of the sail. The layout of the panels does not affect the shape of the sail which is defined by its dimensions and its mould. Except for the Radial cut layout, the number of panels is determined by the cloth width and seam width entered in the "Cloth" box.

- The most commonly used layout is the "Crosscut". The panels are laid perpendicular to the straight line joining the peak to the clew of the sail.

- The "Twist foot" layout is similar to the cross cut except that the lower panels are rotated such that they do not intersect the foot of the sail.

- The "Horizontal cut" layout lay the seams in the horizontal plane. This option can be used to visualise the profile of the sail at various levels and to output files with the 3D coordinates of the sails for use by CFD tools.

- The "Vertical cut" layout places the panels parrallel to the straight line joining the peak to the clew of the sail. This is the favorite layout for the old timer's main sail.

- The "Mitre cut" layout is the favorite for the old timer's genoa. The sail is divided in two parts by a line joining the clew to the mid point on the luff and the panels organised to be perpendicular to the foot in the lower part of the sail and perpendicular to the leech in its upper part.

- The "Radial cut" is used mostly for competition as the cloth is mostly aligned with the directions of maximum strain. When using the Radial cut option it is important to understand the definition of the number of sections, number of radial gores and number of luff gores (see figure below).

Figura 3. Radial cut gores definition

#### 3.1.4. "Sail shape" box

You enter there the depth of the sail at 3 levels, near the foot, in the middle of the sail(the exact position being defined in the mould screen) and near the top of the sail.

The twist angle is the angle expressed in degrees by which the top of the sail is rotated with respect to the foot. The twist is globally determined by the amount by which the apparent wind at the top of the mast is rotated with respect to the apparent wind at deck level. For a jib the twist is sometime driven by the need to have the upper part of the leech sufficiently open to clear the spreaders. For a mainsail the twist is also driven by the ability of the rig to carry the tension in the leech, in particular a gaff rig will have more twist in its main sail than a Bermuda rig. It is important that the twist angle entered in Sailcut reflects the reality of the shape of the leech when sailing in an average wind.

The sheeting angle value is the actual sheeting angle measured from the boat centerline when the sail is set on the boat. For a jib the minimum value is 5 degrees. The value is of importance to ensure that the sail is properly positioned when displayed in the "rig viewer". You can then visualise for example the slot between a jib and the main sail as set when sailing.

#### 3.1.5. "Cloth" box

Enter there the width of cloth used, the width of the seams between adjacent panels, the width of material to be added to the leech to make the leech hem and the width of material for the foot hem and the other edges hems.

The figure below describes de location of the various hems and seam width.

Sailcut will compute the panels such that they fit within the declared cloth width including the seam and hems width as appropriate.

Note that when using the radial layout, the seam width between horizontal sections will be twice the width of the seams between adjacent panels of the same section.

Figura 4. Sailcut seams and hems definition

### 3.2. Mould dialog screen (View->Mould menu)

The depth of the sail can be entered at three levels located at the bottom (foot) the middle (maximum depth level) and near the top.

The vertical position of the maximum depth profile is controlled by the vertical slide bar to the right of the left vertical frame.

The luff shape and the leech shape can be adjusted for the Top profile and Middle profile only. The foot profile is always an arc of circle.

In order to avoid that the leech makes a hook in the upper part of the sail when the wind increases it is recommended that the Top profile luff shape value be higher than that of the middle profile and that the leech shape value at the top be lower than the middle value.

### 3.3. Rig viewer (View->Rig menu)

This viewer is used to display several sails on the same rig.

The File->Add sail menu entry is used to purge the viewer.

The File->Add sail menu entry is used to add sails already created and saved with Sailcut.

Once a sail is added to the rig viewer the sail information frame appears below and it is possible to translate the sail in the 3 directions by adding X-Y-Z displacement values. If you have misplaced a sail use the Reload button to recover the initial sail. You can also use the Remove button to eliminate a sail. 2 slides allows you to ratate the rig in azimuth and elevation and view the ig from any vantage point.

The File->Save menu entry is used to save a rig with a combination of sails.

Rigs which have been saved can be later opened as an entity with File->Open menu entry.

Note that the rig viewer window must be closed to allow you to return to the main screen of Sailcut.

### 3.4. View controls

It is possible to zoom, pan and rotate the sail in the view window:

- rotation : you can control the rotation that is applied to the sail by using the elevation and azimuth sliders.

- pan : click on a point with the left mouse to center the view on that point.

- zoom : to zoom in press CTRL and + and to zoom out press CTRL and -. You can also use the zoom buttons in the view controls or your mouse wheel to zoom in and out.

### 3.5. Sail panels development

The developed sail is display by clicking on the "Development" tab from Sailcut CAD's main window. This presents you with a view of the developed (flat) panels of the sail. The view controls are the same as those of the main window. The blue line represents the edge of the finished panel (draw line) and the red line represents the outer edge taking into account the seam and hems width allowance (cut line).

You can export the points which define the edges of the developed panels with the draw and cut lines to the following file formats:

- Carlson Design plotter (.sp4) using File->Export development->to Carlson plotter

- AutoCAD DXF using File->Export development->to DXF

- XML dump of the points using File->Export development->to XML sail (see Sección 6.3, “XML representation of a sail” for file format details)

- plain text dump of the points using File->Export development->to TXT sail (see Sección 6.1, “Text representation of developed sail” for file format details)

### 3.6. Loading / saving sails

Once you have customised you sail, you can save it to a file (File->Save or File->Save As) and load it (File->Open) next time you want to work on it. Both the sail's dimensions and the parameters of the mould are saved.

Sailcut CAD uses XML files to store the sail data. These files are plain text so they can easily be viewed using your favourite text editor.

### 3.7. Exporting 3D sails

In addition to Sailcut CAD's native file format, it is possible to export all the 3D points located on the edges and seams of the panels that make up a sail. You can export the three dimensional sail to the following file formats from the Export 3D sail submenu of the File menu:

- AutoCAD DXF file using the to DXF menu entry.

- XML dump of the points using the to XML sail menu entry (see Sección 6.3, “XML representation of a sail” for file format details).

- Plain ASCII text dump of the points using the to TXT sail menu entry (see Sección 6.2, “Text representation of 3D sail” for file format details).

- SVG (Scalable Vector Graphics) file using the to SVG menu entry.

### 3.8. Printing data and drawings

The File menu offers various printout possibilities:

- File->Print->data, will print the data of the sail,

- File->Print->drawing, will print a drawing of the complete sail,

- File->Print->develop, will print all the developed panels with key points coordinates (1 panel per page). The definition of the developed panel key points coordinates is given in the figure below. The X,Y coordinates are absolute coordinates referenced to the lower left corner of the box enveloping the contour of the CUT line of the panel (edge of cloth). The dX,dY coordinates are relative to the straight line joining the end of the corresponding edge and it should be remembered that the origin of dX is at the left end of the edge and positive value of dY indicate that the point is left of the straight line joining the origin to the end points of the edge.

The printout scaling is such that the sail drawing and the largest developed panel automatically fit in one page. For printing panels to a precise scale it is preferable to export the developed sail in a DXF file and use a CAD package to print the panels.

Figura 5. Developed panels drawing

## 4. Sails surface formulation in Sailcut

TODO

## 5. Where can I find more information about Sailcut CAD?

TODO

## 6. File formats used by Sailcut CAD

### 6.1. Text representation of developed sail

TODO

### 6.2. Text representation of 3D sail

TODO

### 6.3. XML representation of a sail

TODO

## 7. Copyright

Copyright (C) Robert Lainé & Jeremy Lainé.

Sailcut is a Registered Trademark of Robert Lainé.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. See http://www.fsf.org/ for the licence terms and details.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

The authors would appreciate that publications on sails designed with Sailcut include some acknowledgement of their work.