Tangent Threadlines & Loops The optional Tangent Loops module is used for manufacturing threadline Threadline or String Sails

or string sails. The features in the loops module are being used by many factories around the world, and are being developed to keep pace with the requirements of this rapidly developing segment of sail making.

Loops

The idea behind the loops module is to separate the functions of sail

Overview

design and membrane manufacture. The sail designer and the sail design software develop load paths or string paths on 2D or 3D sail panels. These panels and paths are exported to Tangent, and all the manufacturing features necessary to make the sail are added by Tangent. Currently, there are several approaches to manufacturing threadline or string sails which fall into three broad categories: narrow panelled sails, “one piece” sails, and thread aligned one piece sails.

Narrow

Narrow panelled sails are sails made from relatively narrow panels (less

Panelled Sails

than 2000 wide) made on a long, narrow machine and generally laminated using a traditional laminating roller. This is the earliest method of manufacturing string sails.

One-Piece

So-called one piece sails are manufactured on wide machines (most made

Sails

by Aeronaut around 10 metres wide) where fibres are laid over a piece of film as large as the whole sail in continuous passes from corner to corner. When the top layer of membrane is laminated onto the laid-up part, broadseams are drawn and the membrane is slit and re-joined to shape the sail. Inherent in this process is the fact that due to the slitting and re-joining, the fibres crossing the broad seam will no longer align in the joined sail.

Thread Aligned

A thread-aligned one piece sail is manufactured in a similar way, but at

One-Piece

each broad-seam, the yarn-laying plotter slows and turns, to re-align the fibre paths so that when the membrane is broad-seamed and re-joined, the threads align correctly. This type of sail is somewhat slower to manufacture than the one-piece but is cosmetically more attractive, and theoretically more structurally sound.

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To make a one-piece sail, it is necessary to have a CAD file containing the sail outline, panel outlines and all the threadline paths. To make a threadaligned one-piece sail, you can use the same panel data from a narrow panel sail, and let Tangent link the panels and align the threadlines across the broad-seam. Using the thread-aligned techniques, you can manufacture small to medium sized sails as one-piece. Very large sails can be made by separating off the foot panels and laying them as single panels, and completing the upper sections of the sail as a thread-aligned one-piece. Since both versions of one-piece sails are considerably faster to lay than narrow panel sails as well as wasting less fibre, it is likely that this method of manufacturing string sails will become more prevalent.

Loops

What ever type of construction is used to manufacture threadline or string sails, the process uses a machine to lay a series of fibres in a continuous path from corner to corner of the membrane. When the machine reaches a corner or sail edge, the thread laying mechanism rotates to align with the next path, and then follows the path to the next corner or edge. In this way, the entire set of threadline paths are joined into one single path so each set of threadlines may be laid in a continuous movement. The joining process is called looping, and Tangent is used to develop these loops. Where threadlines cross panel edges, they may be some distance apart. This requires the fibre laying head to traverse to the next threadline path in an elongated loop. The size of this loop is dependent on the geometry of the fibre-laying head as well as the spacing between threadlines. It is possible to turn the fibre laying head quite sharply, but depending on the width of the roller laying the fibres, the glue being used, the fibre type, sharp turns may present problems when laying, so small arcs are normally preferable.

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Threadline paths may not all meet or overlap exactly at a corner such as a clew. If they do, especially on larger sails, the build up of fibres may be so thick that they make laying very difficult. They’ll also make finishing the corner difficult too. So in most cases in corners, the threadlines are spread to distribute the fibres more evenly.

File Types

There are several sources of CAD files used for manufacturing threadline or string sails. These many be generated in 3D from dedicated or fully featured sail design programs such as SailPack. The files may be generated in 2D by stand-alone programs laying fibre paths on panels exported from legacy sail design programs which do not have the ability to generate threadline paths in 3D. Or the threadline paths may be generated on the 2D panels by plug-in tools in CAD software. Which ever method is used, it is our opinion that the job of these programs is to develop the paths to suit the designer’s ideas of shape and structural strength. It is the job of the manufacturing programs such as Tangent to develop and add the manufacturing details such as loops, alignment marks, film outline etc. Currently Tangent supports file types from Vectorworks (VS text files), Fibrepath UC files, and DXF-AAMA files. Due to the standardisation of the DXF-AAMA files, these are likely to be the best supported and the most flexible files to use. If you are using SailPack, export your files as DXF-AAMA. If you are using CAD software, please contact the factory about formatting DXF-AAMA files to work with Tangent.

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Formatting

Files need to be formatted correctly for working with Tangent’s loops

Files

feature. This technology is in its early days and though most files can be expected to work without problems, problems will happen if files are not correctly formatted before reading into Tangent. In almost all cases, files for threadline or string sails are generated by sail design software or tools in CAD software specifically developed to generate threadline paths. As a result, paths for threadlines are arrayed in order. This means that all paths start at one edge, commonly the bottom left corner, and are developed left to right. If one path is created running up a panel and the adjacent one runs top to bottom, Tangent will not develop paths correctly, if at all. Since Tangent develops its own loops, it is not necessary to develop loops in the design software. Attempting to import paths with loops is likely to cause problems. If you are attempting to develop paths using CAD software, it’s likely that the paths will be developed properly… until you do something to the CAD file. It is very easy for paths to get scrambled, even by doing simple actions in the CAD software such as grouping. If your CAD software supports plug-in tools, it is relatively easy to develop suitable routines for sorting and ordering sets of threadline paths to conform to standards set by sail design programs. In the DXF-AAMA format, threadline paths are put on layers from 1001 onwards. Otherwise the format is identical to other DXF-AAMA files, with normal panel details present in the standard AAMA layers.

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Importing Threadline Files DXF-AAMA

Threadline files are imported in the same way as other files. You can either select Open from the file menu, or Import… If you are using DXF-AAMA files, remember that DXF does not contain information about the units used in the design file. You may have to use trial and error or contact the designer to find the units used in the file.

You should select the CAD view for AAMA files. The layout view is probably not necessary.

UC Files

With UC files, you will need to set the scale of the original file. This is normally contained in the file header. /* FBRPATH: 10-15-2004 Xscale:-500.913 Yscale: 500.913 */

You can open the file with a text processor to check.

UC files often contain “loops”, however these may be right angle corners and may be badly formed. If you check the “Use existing yarn loops checkbox, these will be left in the file. Otherwise Tangent will strip the loops so you replace them with with any size arc or loop you require.

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To begin with, work on one panel at a time. UC files contain only one panel, but AAMA files may contain many panels and patches. Create a new window. Select a panel in main file window and holding the option key down, drag a panel from the main window to the new window, so you make a copy of a panel in the new window.

Working

Adjust the fabric width of the new window using the info pallette to suit

Fabric width

your work, and large enough to accommodate all the loops. If you are working with a wide format system, it is probably best to make the fabric width as wide as your floor. In any case, the fabric working width will depend on the type of threadline sails you are manufacturing.

In the plotter control window, you can see paths for each set of threadline paths. In the case of AAMA files, these have numbers from 1001 up. Many UC files paths named “head-clew” etc. You can set colours for each of these paths.

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Colouring

Having a different colour for each path allows you to see what you are

Threadline

doing when developing loops and plotting. Go to Preferences: Setups:

Paths

Paths. Scroll down the list of standard path colours until you see the paths in your file. Clicking on the colour swatch in the Colour column of the Paths pane will bring up a standard colour picker. Select a different colour for each path.

Deleting

Tangent stores a record of each path it opens. Over time you may get a

Threadline

huge list of redundant paths in the list. To delete excess paths, close all

Paths

open files. Go to Preferences: Setups: Paths. Scroll down the list of standard path colours and select the first unwanted threadline or non-standard path. Hold down the shift key and scroll down to the bottom of the list. Click on the last line in the paths list that you want to delete and click on the Delete button in the Paths pane. Make sure you do not delete any paths for which you have special setups, or take a note of the settings so you can make the same settings on new paths.

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Threadline

Tangent has various settings specific to threadlines. Go to Preferences:

Preferences

Extras. Set the Threadline Head Turning Radius to suit the size of arcs you want on the loops joining the threadline paths. You may need to experiment with this to find the best value for your work.

Set the Threadline Half Width to suit your roller. This factor controls the offset between the loops and the edge of a panel. If the loops are being made across panel edges, clear the loops and increase this value. The Offset Threadlines value controls how close to the edge of a panel the loops are developed. Threadline Lead In and Threadline Lead Out control how close to the first threadline the machine start is placed. Ideally, the machine start is well away from the edge of a panel, but inside the membrane film. Panel alignment marks are used to allow panels on the computer screen to be aligned with panels on the floor to allow re-plotting of the panel outline after it has been laminated. Text offset refers to the panel name which is written on each panel before plotting so all parts of a sail are correctly identified. These marks should be inside the film outline, but outside the sail panel itself. The offset value should be around 50% of the Film Outline value. If you are using Tangent to develop the film outline, set the film outline offset to a width large enough to include your loops and set a path colour suitable for the tool you are going to use to mark or cut the film. Tangent 4

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Developing Threadline Loops

Once you have made suitable settings in preferences for threadlines, you can develop loops. Begin by working on a single panel. In the Plotter Control Window, turn off all paths except one. See “Path Visibility”. From the Extras menu, select the path number you are working on.

Selecting Calculate loops will generate a set of loops on the selected path.

Selecting Clear Loops will remove them.

You can repeat this process for all the paths in a panel.

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Path

You can use the Info palette to get information about paths. You can view

Information

the length of the path, the length of the loops, the total path length and the percentage waste (in the loops) for each path.

You’ll notice that this narrow panel method is the most wasteful of all methods of manufacturing threadline sails since the proportion of loop length to path length is so high.

Other loop forms

Setting the Threadline Head Turning Radius to a lesser value will reduce the amount of fibre used in loops… if your threadline head will reliably lay yarn when turned in a tighter radius.

Calculate Loops (Multiple)

Using the Calculate Loops (Multiple) option will make sure the loops are made in the shortest distance between path ends. Tangent 4

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This option reduces the path length and can use less time in turns, but reportedly it is more difficult to recover from problems using this method due to the difficulty of working out which path was being plotted when the problem occurred. Future versions of Tangent and Aeronaut controller software will have a full feedback feature where the plotter’s position and path index will be shown on screen at all times.

Calculate Loops

There may be cases where the complexity of the paths or poor path

(Subgroups)

development from the original design software does not allow loops to be developed using the standard option. Using the subgroups option, Tangent breaks down the loops into subgroups to allow more logical loop development. In the picture below, loops have been developed using the standard option, and there are several problems, noticeably on the left side. These could be fixed by editing in Vectorworks, but it is quicker to try using sub groups in Tangent.

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In this version, loops were developed using with the sub-groups option. New path-groups were added, and loops were successfully formed.

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One-Piece

In current versions of Tangent you must develop one=piece sails with the

Sails

foot on the left side of the screen, luff down, and the head on the right of the screen. The process is relatively complex, and errors can result if paths are developed with the panels rotated in other directions. In a simple one-piece sail, all the paths are joined before the file is imported into Tangent, and loop development etc. is essentially the same as for single panel work. What follows applies mostly to thread-aligned onepiece sails. When the sail panels have been imported, especially if the sail file also contains patches, it is a good idea to make a new queue or fabric window, and drag a copy (option-drag) of the main panels into this window. Initially, only drag the panels you are going to work on at once. So if you are working on a very large sail where the foot sections are to be laid separately to the head sections, perhaps make separate windows to develop loops for each section. If you make a habit of saving this queue after any significant work, you can always revert to the saved version to recover from problems.

Orientating Panels

To begin with, you should orientate all the panels correctly in the queue or fabric window.

Rotate all the panels to put the luff down, and the clew up, head towards the right. Select all the panels (-A) and rotate them (-L). If the panels don’t rotate as expected, check the info palette to make sure the rotation rule options are set to 90˚ or Free.

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You need to allow space between each panel for the fibre laying head to re-align between panels. Ideally, the head moves as little as possible to minimise the slow-down and waste fibre. The horizontal and vertical alignment of each panel is a matter of judgement depending on your mechanism and technical factors. In the examples below, the horizontal spacing is set to 150mm. Enter this figure into the Nesting Gap edit field in the info Palette. Select all the panels, -A, and press the left arrow cursor key to move the panels apart with a 150mm separation.

One-Piece Sails

There are several ways to set the vertical alignment, but the best method probably depends on personal preferences and the way in which the sail’s vertical fibres are run, the main idea being to minimise the curvature of the links between panels. You can adjust the vertical position of panels using the mouse, or you can use alignment marks. Alignment marks may be present in the sail panels, or you can develop them with Tangent. Select all the panels and select Extras: Generate Align Marks: 4 Sides. This will put alignment mark on the head and foot of each panel.

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Drag the panels away from the home position so you can see all the alignment marks. You can use Tangent’s zoom tool to view these close-up. (The selection and zooming tools can be switched by typing the letters Z-X-C and V.) Type -5 to un-zoom and fit all the panels into the window.

You’ll see that the panels towards the head of the sail are perhaps lower down in the window than is desirable. You can nudge these panels upwards with the mouse, or you can generate grid-lines and align panels using this if you want. The foot panels are reasonably well aligned. So select panel 2. You’ll see a bull’s eye mark appear on one of panel 2’s alignment marks. Select Window: Grid to bring up the grid palette. Switch to the Bull’s Eye pane. Using the two arrow buttons at the top of the pane, you can switch the bull’s eye marker to highlight each mark on panel 2. Make sure the lower right-most mark is highlighted. (Equivalent to the panel’s own tack.)

Now press the Grid from Marks button in the Grid pane. You’ll now see a series of grid lines in the window spaced according to the tack mark on panel 2. (You can enter 0 into the vertical grid first and repeat edit fields to remove the vertical grid lines, but don’t! It is not necessary here.). Tangent 4

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Now select panel 3. Click 2 times on the arrow buttons on the Bull’s Eye pane to select the head alignment mark on panel 3. Now, while panel 3 is selected, hold down the option key and press the vertical cursor key on the keyboard. This will cause panel 3’s selected alignment mark to snap to the horizontal grid line. If you don’t like this position, you can use the arrow buttons in the Bull’s Eye pane to select the tack alignment mark and have another go.

Repeat this process with each panel (changing the selected alignment marks if necessary) to optimally align each panel. You can at any time clear the grid using the Clear Grid button in the Grid pane and make another. You can select all the panels, clear the existing marks using the menu Extras: Generate Align Marks: Clear All Marks option, and re-generate the marks to try a different alignment.

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There may not be an optimal alignment for all sail panels and paths, but if there is, the sail design software developers can put an alignment mark on each panel so this feature can be used to rapidly align panels for optimal inter-panel link development.

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Calculate Loops

The Calculate Loops (One Piece) option is designed to allow loops to

(One Piece)

be developed between two or more panels. The paths are joined by arc shaped links so the threadline head can move smoothly between panels.

Groups &

When you develop loops in a one piece sail, you are by definition deal-

Locking

ing with more than one panel. For this reason, panels are grouped as soon as any one-piece loops are developed. One piece sails should be locked as soon as any plotting operations are done on the file. It you find you cannot move individual panels, check to see if they are grouped or locked. You can move and rotate grouped panels after loops have been developed but at the moment it is best to only develop loops with the sail in the position described above. The development of loops and links in a one-piece sail is similar to the development of loops in a single panelled sail. You select all the panels you want to loop. You then select the path you want to develop the loops on, then you select Calculate Loops (One-Piece) from the Extras menu.

If you examine the clew region of this development, you’ll see the links are all distorted. In this case, it is probably best to clear these loops, ungroup the panels, move the foot panel and redevelop the loops and links.

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After sliding up the foot panel, the developed links are smoother. Proceed through the sail developing loops on each path. It is very important to make sure you can develop loops on the whole sail before you begin laying fibre!

There are going to be instances of difficult paths and difficult files where work-arounds fail. In the sail above, the final set of loops (the second reef) would not develop using one-piece, but developed fine using the standard loop calculations.

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Trouble-shooting

Threadline or string sails are a developing technology and there are bound

loop development

to be teething troubles. It is really important to develop all the loops in a sail before starting plotting. Once you have started laying fibres, solving problems becomes a lot more difficult. If you have difficulties developing a particular path, the following may be of help. Lay up problem panels as single panels. This is a relatively painless operation, and if it means you continue work but waste a little fibre, it may be the best way out of a difficult situation.

It was not possible to develop paths on the foot panel on this design using one-piece loop calculations. If the foot panel is removed, it is now possible to develop loops on the rest of the sail.

And, using the Subgroups option, it is possible to develop all the loops on the foot panels.

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Be aware of what causes loop problems and avoid these at the design stage. Large numbers of paths which are split at an oblique angle can cause problems. This can occur with tack-clew and reef paths which cross panel divisions. The best solution for this is to shift the region upwards, and/or develop the foot as a single panel and the upper part of the sail as one-piece.

Edit the design files. Tangent saves its files in Vectorworks Vectorsript (VSS) format. This is a text file format. If you have Vectorworks, it is often easy to solve problems by exporting the panels from Tangent to Vectorworks, editing or sorting the paths, and exporting back to Tangent. Re-plot problem panels using the alignment marks to re-position the panels. The idea behind the alignment marks on these panels is to allow accurate repositioning of the panels after lamination. You run the plotter over to where the on-screen pattern says the alignment mark should be and using the Bull’s Eye Pointer and Align to 1st and 2nd buttons in the Bull’s Eye pane, you align the on-screen panel to fit what is laid on the floor. So it is possible, as long as you have alignment marks, to cut off a problem section of a one-piece sail and accurately reposition it for laying more fibres. The use of the bull’s eye pointer is covered in this manual. Send Feedback to Aeronaut. If you have difficulties, it is very important that you give us as much information as possible. “This don’t work” is probably not the full story. The Feedback menu item (Help: Feedback…) will make a copy of your preferences as well as the design file. You should compress (Stuffit or Zip) and email them back to Aeronaut. Be sure to compress the files before putting them on a Windows based email system. Use the latest version of Tangent. Read the Manual. Tangent 4

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Sorting Paths in

Tangent has been developed and tested using many files from popular sail

CAD software

design software such as SailPack. Tangent has also been used in several factories with threadline paths developed in CAD software. In all these cases, the threadline paths are developed in order by the design software. If you are going to be working with files from software which does not develop the paths in order, Tangent may fail to develop proper loops. The reason for this is normally that the originating CAD file had a more or less random order of the polygons forming the threadline paths. We have been able to write simple plug-in tools in Vectorworks to sort and order threadline paths to correct problems in difficult sail files. If you are going to be dealing with this type of file on a regular basis, it’s worth looking at automatically sorting and formatting CAD files. The file below takes less than 10 seconds to re-format.

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Film Outline

Threadline or string sails are laid onto a film base, normally Mylar or a Maylar/Dacron scrim laminate. With wide format panels, the film outline will be made from several strips of film. These are normally developed from the sail outline, cut using a conventional sailcloth plotter, and taped up on the floor or table. Tangent has features to allow the film outline to be developed. In most cases, you would develop a film outline in a new window or queue.

Alter the fabric width of the new window to fit the film outline vertically… you can read this dimension using the info palette or the Length figure at the bottom left of the queue window. Rotate the film vertically, and duplicate it (-D). Rotate this 180 degrees, and select the split palette (-K). You want to make sure the seam lines or splits on the upper and lower film layers on the finished sail don’t coincide. So select the left-most panel. Select Split from Panel Top. Set the split width equal to the film width and enter a suitable seam allowance for the film.

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Splitting the film outline

Repeatedly press the Split button to divide the panel into film width strips or panels. Each one should have a unique number, derived from the original panel number.

If the split widths are correct on the first film panel, you can either split the second part from the top, or rotate the panel and split again from the foot of the sail. This time, enter 50% of the film width as the split width. Split once, and then enter the full width of the film as the split width. This ensures that the join seams of the film will not overlap. Close the split window (or it will make annoying split suggestions on any selected panel.)

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Set the fabric width of the window to the same as the split width you uses for the film.

Nest or Autonest the film panels.

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Threadlines:

The plotter setup for doing threadline sails is often different to that used

Plot by Path

for conventional plotting and cutting. One significant difference is that you always must have Plot by Path selected in the Plot menu. The plotter needs to plot one entire path before moving onto anything else. This is especially important for one piece sails.

Loop Speed

You may require a different speed profile for the loops and links in a string

Setup

or threadline sail. Since loops developed in Tangent are in a different data class, you can set a speed for a path and a separate speed, acceleration, pressure etc. for the loops and links. This is one of the advantages of having Tangent develop these elements in the process rather than hard-coding them in the design file. In Preferences: Setups: Speeds, create a new speed setting and call it Loops. Make sure the row is enabled. Set the speed, acceleration and pressure settings to suit your work. Tangent will now switch automatically between the path settings and loops settings when it encounters a loop.

Note: This feature requires that the plotter is an Aeronaut plotter capable of handling in-line variables, and fitted with a digital pressure regulator.

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