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A JPEG Image Found in an Internet Search

A JPEG Image Found in an Internet Search

In Country Style Cabinets with a Furniture Flair – Part 1 and Part 2, I showed you how to add base and crown molding to a cabinet. If you are a professional cabinetmaker you probably don’t want to spend your time creating moldings over and over. You need a library of moldings to choose from. You can find thousands of moldings from internet searches, especially the 3D Warehouse. However, many of the interesting moldings are .jpg images such as I used in Country Style Cabinets with a Furniture Flair – Part 2 shown at right. So you may find yourself stuck creating it as I did in Part 2.

However, it only takes a few extra minutes to add your creation to a library of moldings. Hence forth they are available from the Components dialog box (Components library). In this post and accompanying video I will explain how you can create your own library and provide you with a few options for organizing the library. But first I want to review the steps used in Part 2 to create a cross section from a .jpg (or other graphic type) image file. I will use the .jpg profile shown above right found in an internet search. I will call this profile Jeremy.

Steps in Creating a Cross Section From a JPEG Image

If you don’t have a Bezier curve tool already you will need one for this procedure. There are some really good and flexible extensions for SketchUp. I have two favorites:

Fredo6: Bezier Spline v1.9a

SketchUp Team: Bezier Curve Tool v1.1

Bezier Spline is very flexible, draws polylines, Bezier curves and Spline curves. It has numerous icons and can be a little intimidating if you don’t use it a lot, but it is my favorite for drawing complex curves. The Bezier Curve Tool is quick to learn and easy to use and the results are quite astonishing. The Bezier Curve Tool is the one I will use in this post and video.

SketchUp Profile with Discontinuities Labeled

SketchUp Profile with Discontinuities Labeled

Before I get into the steps for creating a cross section I want to make sure we are on the same page with terminology. Curves such as S-curves are made up of curve segments that join at a point of inflection. Points of inflection are points along a curve where the curve changes from convex to concave or concave to convex. They are smooth transitions and mathematically both segments have the same tangent at that point of inflection. Discontinuities on the other hand are points where a curve segment joins another curve segment (or line) and the two segments do not share the same tangent line. At this point of discontinuity there is an abrupt change in direction of the overall curve.

The image at left is the SketchUp model of the cross section (profile) I created by tracing Jeremy above right. I will also refer to this SketchUp model profile as Jeremy in the future. Notice there are five points of discontinuity along the front face. Between these five points are four smooth curve segments. The smooth curve segment are also broken down into sub-segments; at places where there are inflection points or where the sharpness of the curve changes and it is convenient to add a sub-segment.

These sub-segments are called polylines (all curves in SketchUp are polylines ‘smoothly welded’ together). Where these sub-segments join one another, but not at discontinuities, we want to weld them so they do not appear as a line when the profile is extruded. This means you need another tool:

Smustard Team: Weld v3.0.5

With the above terminology and our new tools we are ready for the steps in creating mold cross sections.

  1. Drag and drop a graphical image such as a .jpg file into a new SketchUp model.
  2. Orient the image at the Origin. Since most moldings run horizontally is is usually best to place the image on the Blue/Green or Blue/Red plane. Don’t worry about the size of the image at this point.
  3. Most .jpg images of molding have dimensions shown on them like Jeremy above right. If not you will have to choose a desired dimension for an edge in the image. Measure the actual length of that edge with the Tape Measure tool and record it.
  4. Create a scale factor with the actual dimension and the dimension given on the .jpg or the desired dimension you chose. It’s a simple matter of dividing the two numbers. Chose which is the divisor by whether you need to scale the image up or down.
  5. Use the Scale tool and the scale factor calculated in Step 4 to scale the image to the correct size.
  6. Location of a User's Custom Components Library

    Location of a User’s Custom Components Library

    The image is a component slightly larger than the profile you want to trace and it is also a face that you can trace on. Use the Line and Bezier tools to trace the profile. Here is the very important part: keep your eye on the Inference Engine each time you click on a point and make sure you are actually on the face. The Inference Engine tool tip will say ‘On Face in Image’. If you are not on the face you will be somewhere else in 3D space and in the end will not get a face to extrude.
  7. After the outline is traced and you are sure you have a face to work with locate all the points of discontinuities. Between the points of discontinuity select all the sub-segments with the Ctrl key and the Select tool. Use the Weld tool to join them.
  8. Delete the .jpg image. It is no longer needed.
  9. Make a component of the profile. Give it a name that will make sense to you later when you may want to locate it in the library again.
  10. Save the file in your library file. Here is where I saved my Jeremy.skp file:C:\Users\Joe\AppData\Roaming\SketchUp\SketchUp 2017\SketchUp\Components\Crown Molding

Your Library Appears in the Components DIalog Box List

Your Library Appears in the Components DIalog Box List

If you look in the Window > Preferences dialog box and select the Files page you will see where SketchUp is expecting you to put your library. If you put your library there is will show up in the Components dialog box where you can readily drag it into a model. See the images above right and at left.

Choices, Choices, Choices!

In the video you are about to watch you will see there are several (actually numerous) ways you can build and save your library. The first, as I just explained, is to save only the profiles in the library. Then, when you create a new model and want to trim something you can drag the molding profile into your model. From there you can proceed as I did starting at 50:08 in the Part 2 video or starting at 26:22 in today’s video.

In today’s video you will see that there are two other ways you can store your moldings in your library. You can include the profile and some number of useful components with their bounding boxes corrected, or you can store the profile and some number of useful components without their bounding boxes corrected.

Which of these three methods you use is up to you and how you are comfortable manipulating images or components. Each has its advantages and disadvantages and no one way is right for everyone. You need to develop a method that works for you.

As promised I am going to supply you with two profiles you can use to start your library. Crown Molding ZIP Folder Now it is time to enjoy today’s feature film. Get the popcorn, sit back and relax while I work.


Larson Kitchen 1Later this fall I will be releasing an Alpha version of CabWriter. I have been working on this project with Greg Larson, owner of the New England School of Architectural Woodworking (nesaw.com). Greg, you might say, is the architect of CabWriter and I am the coder. The pictures you see here are snapshots I took of Greg’s kitchen – remodeled using CabWriter.

You may have heard bits and pieces of CabWriter if you follow me on my Popular Woodworking blog, or my personal blog or website. Today I want to formally introduce CabWriter and give you a hint of its features and show you some of the results to-date. But first there are two questions I need to answer, even before you ask them: what is an Alpha release and what is CabWriter?

What is an Alpha Release?

Larson Kitchen 1In the software world a new product is sometimes released in what is referred to as an Alpha release. The purpose is primarily to get very early feedback and suggestions. A secondary purpose is to build interest. Alpha releases are almost always free and have the following disclaimers:

  1. Functionality is incomplete or may change in future releases. That is, current functionality may be dropped or new functionality may be added in future releases. A CabWriter specific example is that it only works with inset doors in the Alpha release, but in its first product release will work with inset, overlay and frameless doors.
  2. There may be significant software bugs in an Alpha release. This is a direct tradeoff with the desire to expose a new product early. Users are asked to be patient and to take part in its improvement by reporting bugs to the developer. In the specific case of CabWriter reports should be made to me at : jpz@srww.com .
  3. The user uses an Alpha release at their own risk whether for personal use or commercial use. The very nature of an Alpha release is “use at your own risk”.
  4. Using an Alpha release is not a license to use the product release. You will need to acquire a license after product release.

Larson Kitchen 3So much for disclaimers, here is why I am releasing an Alpha version. I will be looking for help from users who want to design and build kitchen cabinets, bathroom cabinets, and office or library furniture. I want feedback in the form of constructive criticism, bug reports, feature suggestions and training needs. In return, for those who actively participate, you get the first CabWriter product license for free. If you are interested you can contact me via email and ask to be an Alpha user. You don’t have to participate to be an Alpha user, but only active participants will get a free license. I will, of course, be the judge of who has actively participated.

What is CabWriter?

Larson Kitchen Modeled in SketchUpCabWriter is a SketchUp Ruby script extension (formerly called plug-in). As its name implies CabWriter permits automatic and efficient custom cabinet 3D modeling, shop drawing documentation, cut list generation and DXF output that permits CNC milling. CabWriter is tightly connected to CutList Bridge and hence CutList Plus fx for material optimization. CabWriter takes advantage of the powerful Ruby API supported by Trimble SketchUp; its functional code is written in Ruby while the Graphical User Interface in JavaScript, HTML and CSS.

Shop Drawing in LayOut 1There will likely be two or three version with a target range from the hobbyist/weekend warrior to the professional cabinet shop. CabWriter comes with CutList Bridge. So far we have designed, built and installed four custom kitchens and are currently working on the fifth and sixth.

Shop Drawing in LayOut 2The goal of CabWriter is to be able to meet with a client at their residence and within a few hours walk away with a complete 3D design the client can sign off on, including plan and elevation views, cut list and materials list, cost estimate and even DXF output for CNC milling. In the real world of course clients will always want to make changes the next day and for a few weeks later. However, CabWriter makes it possible to complete this entire goal in just a few hours sans further changes. In the next two months we expect to demonstrate this goal including the installation. We will document the entire project from design, through CNC milling to completed installation in a video.

Shop Drawing in LayOut 3Before I show you some of the design output of CabWriter let me list some of its important features:

  1. The entire design file stays with the SketchUp model. While you may export files for Excel, OpenOffice or CutList Plus fx, there is no need to save or archive these files. They can always be reproduced with the SketchUp model file and SketchUp with extensions CabWriter and CutList Bridge.
  2. CabWriter has a large set of defaults all of which can be changed by the user. This makes tailoring CabWriter to a given build methodology relatively easy as well as assigning default material types and names.
  3. CabWriter automatically draws cabinet with any number of boxes, creates and assigns component names, part names and material types and material names. Any attribute that can be specified using CutList Bridge can automatically be assigned using CabWriter.Shop Drawing in LayOut 4
  4. CabWriter permits changing of numerous cabinet and box defaults on a per cabinet and per box basis such as number of doors and drawers.
  5. Cabinets can be edited after they are drawn to change things such as width, height, depth, material, number of doors, drawers etc.
  6. CabWriter Version 1.0 will handle face frame cabinets with inset or overlay doors, or frame-less cabinets.
  7. CabWriter automatically stores CutList Bridge attributes in each component so there is little or no manual entry required.
  8. CabWriter makes plan and elevation views a snap and automatically includes the hatching for material keys.Sheet Optimization in Vectric Aspire
  9. CabWriter is completely functional in the Make version of SketchUp for hobbyists and weekend warriors who wish to design and build their own cabinet. For professionals CabWriter makes integration with LayOut a snap.
  10. CutList Bridge comes with CabWriter and permits near instant cut list generation. Its bridging capability to CutList Plus fx saves material cost with material layout optimization.
  11. CabWriter provides CutList Bridge with the information to automatically create all the DXF files necessary to mill sheet goods on a CNC machine. These DXF file can, for example, can be imported to Vectric Aspire or Vectric Cut2D which will do sheet optimization and output the necessary G code for CNC milling. The DXF files produced by CutList Bridge fx permits use of numerous applications as alternatives to Vectric Aspire (Aspire is the application we are currently using).

Single Sheet Enlargement in Vectric AspireGreg’s kitchen, shown in the previous pictures, and above as a 3D rendering, was drawn entirely in SketchUp using CabWriter. The following images are CabWriter views sent to LayOut. You can see that the drawing set is quite professional and complete. The last two images are the Aspire optimized sheet layout and an enlargement of one sheet. Shortly I will be releasing a training video documenting a complete design. I will announce it and the Alpha release in a newsletter and in my blogs. So stay tuned.

CabWriter to CNC

I would like to end this post with a short video of a CabWriter designed cabinet set cut on a ShopBot CNC machine. CutList Bridge, which is part of CabWriter, produces all the DXF files which are then imported into Vectric’s Aspire or Cut2D which in turn optimizes the sheet layouts and produces the G code necessary to drive the CNC. This video was shot on October 22, 2015 and is the first CabWriter designed cabinet set cut on a CNC machine. Much thanks to Mason Papaport of Rapaport Design (http://rapaportdesigns.com/) for the use of his Shop Bot CNC. Now pop the popcorn, sit back, and enjoy this special feature film.


Greg, on left, and students on installation day.Each year the New England School of Architectural Woodworking (NESAW at www.nesaw.com) runs a five month cabinetmaking course. The purpose of the course is to prepare students for a rewarding career in the field of cabinetmaking. Over 90% of NESAW’s job-seeking graduates find employment at architectural woodworking shops across the United States.

The industry is in dire need of skilled craftspeople, due to the record number of retiring workers and the declining number of vocational programs aimed at cabinetmakers.

NESAW LogoSign up now. Classes begin January 5th and enrollment ends on January 10th. Visit the New England School of Architectural Woodworking for details.

 

NESAW’s program teaches the fundamentals of architectural woodworking and offers students the opportunity to work directly with members of the community to design, build, and install projects. This combination of skills-building and real-world experience makes NESAW’s graduates particularly attractive to employers, since it means a safer employee, less on-the-job training and a better understanding of the entire project lifecycle.

Greg installing a sink.Students who enter the program to improve their woodworking skills or start their own businesses also gain from this approach, as they better understand how to more efficiently design and build a quality product.

The New England School of Architectural Woodworking is owned and operated by Greg and Margaret Larson. I first met Greg in the fall of 2011 through introductions made by a former student of Greg’s and mine. I wrote about NESAW in my December 21st 2011, March 29th and June 11th 2012 Chiefwoodworker’s Newsletters.

Margaret serving cake at graduation celebration.That year I taught a SketchUp class for NESAW students. During this period Greg and I spoke at length about what students were learning and the time consuming aspects of custom cabinetmaking. Out of those discussions came CutList Bridge and later CabWriter. Greg and I have worked closely together ever since our first meeting and I have spent numerous hours at the NESAW shop with his students. Each year I teach a live SketchUp course to the students. I t is with this intimate knowledge that I highly recommend visiting the NESAW website if you are interested in a career in cabinetmaking. You will find no better program or more caring people than NESAW, Greg and Margaret.


CutList Plus fx Preferences/File LocationsIf you use CutList Bridge to export a cut list to import into CutList Plus fx, you need to be sure CutList Plus fx is setup to be compatible with CutList Bridge. This is especially true if you use a non-dollar currency such as the euro. Here is what you need to check.

  1. Open CutList Plus fx.
  2. Choose menu Settings/General Preferences…
  3. Choose the File Locations tab.
  4. Under Export: check “Use Unicode file format when exporting.
  5. Click on the OK button.

If you exported materials.csv files from CutList Plus fx to CutList Bridge prior to performing this procedure you will have to repeat that export/import after this. Consult the CutList Bridge User’s Guide and go to the section called “To Create a List From CutList Plus fx:” for instructions.


SketchUp is woodworker’s chosen tool for creating shop drawings; CutList Plus fx by Bridgewood Design is the leading tool for generating optimized sheet layouts and materials lists. These two industry leading tools don’t natively communicate. That became history with the introduction of CutList Bridge. Now CutList Bridge 4 is even more powerful and rich with new features and is ready for even better things to come.

What is CutList Bridge?

Attributes TabCutList Bridge is a SketchUp Ruby extension. It extends the attributes of components to include such things as the material type used in its milling, the species or material name, re-sized dimensions, shop method tags, the sub-assembly to which it belongs and much more. These attributes are attached to the component and stored in the model file. The user can export these attribute to either: a .cwx file, which can be opened in CutList Plus fx version 12.3 or higher; or to a comma separated value file (.csv aka CSV) and subsequently imported to Microsoft Excel, Open/Office Calc or any spread sheet application that supports CSV importing. Either of these methods will produce a cut list but CutList Plus fx will also produce a materials list, optimized cutting diagrams and project costing.

Setup TabA very important feature of CutList Bridge is that it stores all components’ material and milling attributes in the SketchUp model file. The user need keep only one file of a design and doesn’t have to worry about synchronizing other files when design changes are made. The CWX, CSV, CutList Plus fx, Excel or OpenOffice Calc files can all be reproduced in about four mouse clicks.

What’s New in CutList Bridge 4?

CutList Bridge 3 added four new fields to the cut list .csv file: Tags, Fin T, Fin W and Fin L. However, they were only available for import to Excel and OpenOffice Calc; they could not be imported to CutList Plus fx. This limitation is eliminated in version 4.0, a major release with new functionality. Some of the new functionality was added to support CabWriter, a future new extension that will add to the SketchUp/CutList Bridge/CutList Plus design process. Other functionality was added to generally improve the extension for all woodworking projects. Here is a list of the new functionality and fixes:

CutList Bridge to CutList Plus fx

1. A Legacy Mode checkbox has been added to the Extended Entity Info dialog box Setup tab. If you do not have either a Gold or Platinum CutList Plus fx license of revision 12.3 or higher you should check Legacy Mode. In Legacy Mode you will not be able to export the Tags, Fin T, Fin W and Fin L columns. Legacy Mode is unchecked when CutList Bridge 4.0 is installed.

2. When using the File/Export to CutList Plus fx command a file is saved in the same folder (place) as the SketchUp model file (.skp), with the same name as the model. The file extension will be .cwx if Legacy Mode in not checked. If Legacy Mode is checked the file extension will be .csv.

3. The Tags, Fin T, Fin W and Fin L columns are now included in a File/Export to CutList Plus fx operation. In CutList Bridge 4 the command File/Export to CutList Plus fx now produces a file with the same name as the SketchUp model file but with the extension .cwx (a.k.a CWX) . Users of CutList Plus fx version 12.3 or higher can now open this file with the command File/Open. The fields are automatically mapped so the user no longer need manually map them with the Parts Import Wizard. In addition, upon installation of CutList Plus fx 12.3, the CWX extension is associated with CutList Plus fx, so the user can simply double click on a CWX file and CutList Plus fx is opened to it.

4. Fixed an issue with Add material when the material name contained the inch unit mark ("), which caused weird behavior with the list drop down boxes.

5. Some users have experienced problems with materials.csv files that contain Euros currency. This problem is solved in CutList Plus fx version 12.3.

The attached images show the new Extended Entity Info Attributes and Setup tab and a sample cut list produced with CutList Bridge 4 and CutList Plus fx version 12.3. The video below is a ten minute introductory of CutList Bridge 4 and CutList Plus fx. You can also view it on YouTube in a larger format.

 

Where can I get CutList Bridge 4?

You can purchase CutList Bridge 4 in the Popular Woodworking Shop Woodworking on-line store.


SketchUp is woodworker’s chosen tool for creating shop drawings; CutList Plus fx by Bridgewood Design is the leading tool for generating optimized sheet layouts and materials lists. These two industry leading tools don’t natively communicate. That became history with the introduction of CutList Bridge. Now CutList Bridge 3 is even more powerful and rich with new features and is ready for even better things to come.

CutList Bridge Extension for SketchUp

You can purchase CutList Bridge 3 from the Popular Woodworking On-Line Store.

What is CutList Bridge?

New CutList Bridge 3 TabsMany of you have used this tool before, but for those of you who have not, CutList Bridge is a SketchUp Ruby extension. It extends the attributes of components to include such things as the material type used in its milling, the species or material name, re-sized dimensions, shop method tags, the sub-assembly to which it belongs and much more. These attributes are attached to the component and stored in the model file. The user can export these attribute to a comma separated value file (.csv aka CSV) and subsequently import that file into CutList Plus fx to produce a cut list, materials list, optimized cutting diagrams and project costing. If the user doesn’t have a CutList Plus fx license the CSV file can be imported to Microsoft Excel, Open/Office Calc or any spread sheet application that supports CSV importing.

A very important feature of CutList Bridge is that it stores all components’ material and milling attributes in the SketchUp model file. The user need keep only one file of a design and doesn’t have to worry about synchronizing other files when design changes are made. The CSV, CutList Plus fx, Excel or Calc files can all be reproduced in about four mouse clicks.

What’s New in CutList Bridge 3?

CutList Bridge 3 now supports component numbering capability including manually by the user, automatically in alphabetical or numerical order by CutList Bridge 3 and automatically by CabWriter. CabWriter is a new SketchUp Ruby extension to be announced later this fall. CabWriter automatically draws custom cabinets using a simple and powerful user interface; see the CabWriter drawn kitchen below. CutList Bridge 3 is CabWriter ready.

A CabWriter Drawn Kitchen

A new Tags field has been added to tag critical shop operations such as adjacent component grain matching. Any shop critical operation can be tagged in this text field and can be alphabetically sorted to assist in efficient performance of these shop operations. This field will also be supported in future releases of CutList Plus fx.

Re-sizing of thickness capability has been added to the Resizing field. And now there are three new fields to export the finished or As Drawn dimensions. These too will be supported in the next CutList Plus fx release.

There are a number of internal changes that make CutList Bridge 3 ready for CabWriter as well as the next version of CutList Plus fx.
For more information on CutList Bridge 3 see the CutList Bridge User’s Guide. Below is a partial cut list of the kitchen shown in the above image exported to CutList Plus fx.

A CutList Bridge Generated Cut List Exported To CutList Plus fx

 

Where Can I Get CutList Bridge 3?

CutList Bridge 3 is distributed exclusively by Popular Woodworking. You can purchase CutList Bridge 3 from the Popular Woodworking On-Line Store.

Is there a Training Course for CutList Bridge 3?

PWUlogo_300Yes. There’s a three segment on-line course titled Using CutList Bridge 3 and given by Popular Woodworking University. Each segment is approximately one hour long and covers creating a cut list for three types of woodworking project: Furniture Pieces, Custom Cabinets & Structures such as a shed, home and home addition.


In CutList Bridge Tutorial – Part 1 I demonstrated how to use CutList Bridge to create a cut list for a furniture piece us a Shaker Tall Clock SketchUp model. In Part 2 I use a custom kitchen cabinet to demonstrate how to you the Cabinet Mode features of CutList Bridge. While Cabinet Mode features are particularly useful for custom cabinetmakers it is also useful for furniture designers and craftsmen. I think this video will be well worth you while whatever style of woodworking you do.

Before viewing this video be sure to download and install CutList Bridge 2.5. The previous version had a bug that could make following along with this video frustrating.

Also, you will notice that in version 2.5 you no longer have to use the Save Attributes button as was necessary in previous versions and witnessed in Part 1. All entries are now saved as you enter them.

MAC users may have had trouble using CutList Bridge because of an OS/Safari Browser bug. When you download and install CutList Bridge 2.5 you will be shown a workaround if you have this problem.

Downloading CutList Bridge

CutList Bridge can be downloaded and installed by following the highlighted link; the target post will always host the most recent version of CutList Bridge.

Overview of CutList Bridge

CutList Bridge adds two export commands to the File menu and one dialog box to the Window menu of Trimble SketchUp. The export commands are:

  • Export to CutList Plus fx
  • Export to Microsoft Excel or OpenOffice

The dialog box is called Extended Entity Info and as its name implies is complements and extends the Entity Info dialog box.

When CutList Bridge is installed, as indicated by the availability of these commands and dialog box, a basic cut list can be produced simply by selecting one copy of your model using the Select tool and then choosing one of the export commands from the file menu. Simple as that.

However, the Extended Entity Info dialog box can be used to assign additional attributes to your components, which will produce a richer and much more useful cut list. This first video tutorial will show you how to create a basic cut list and then embellish the cut list with material types (rough lumber, dimensioned lumber, sheet good and other items), material names (cherry, walnut etc.), sub assembly groupings and notes. Subsequent video tutorials will show you how to assign attributes helpful for cabinetry and architectural models.

Downloading the Video to Your Computer

Sometimes the performance of your internet connection, the load on it at a particular time of day, and the length of these video tutorials can all conspire to provide you a frustrating and impossible viewing experience. If this happens it may be preferable to download the entire video unto your system and view it on your local video player. The video file is an mp4. It can be viewed with most video players including QuickTime and Media Player. If you have a default, or user specified, file association for .mp4 you may have to delete it or use a download manager to download this file. Otherwise the associated application may be invoked and file streaming will prevail over downloading. There are numerous free download managers on the internet. Be careful, and do some research to locate one that is not loaded with spyware or viruses.

If you are on a PC platform running Windows OS and have Internet Explorer or Firefox you don’t have to change file association or use a downloader. Simply right click on the link(s) below and choose Save Link As. When Explorer opens choose a destination folder and select Save.

To download this video click here or paste

http://www.srww.com/downloads/blog_posts/CutList%20Bridge%20Tutorial%20-%20Part%202/CutList_Bridge_Tutorial_Part%202.mp4

into your download manager.

Viewing in Your Browser

You may find it easier to view the video in full screen mode. Start the video before selecting this mode. To enter full screen mode click the little screen icon at the bottom of the video player. When in full screen view hold your cursor near the bottom of the screen to access the video player’s controls. Exit full screen mode with the Esc key. This part is approximately 33 minutes long. Sit back, relax and enjoy the show!


CutList Bridge 2.5 is now available for download. CutList Bridge comes with a CutList Bridge User’s Guide that will explain installation procedures and all features and functionality. The User’s Guide gives three examples of types of woodworking that benefit from its features. You can download CutList Bridge 2.5 with this link. Please report all strange behavior or bugs to jpz@srww.com and don’t hesitate to write if you need help.

Changes In Version 2.5

Version 2.5 fixes a bug introduced in version 2.4 and is a must upgrade. This bug will cause the user to potentially loose work and attributes. In version 2.4 I changed and included code to make it unnecessary to use the Save Attributes key to save attributes. Each input change is saved as it is entered. If multiple components are selected and an attribute is entered or changed, only that attribute will be changed in all selected components. Blank fields, unless one or more became blank due to an intentional change, will not be written to all components. This eliminates the need for the Save Attributes button. The button remains but is harmless and it will be removed in version 3.0.

In the process of making this change to version 2.4 I introduced a bug that is fixed in version 2.5. Sorry folks.

Help With Installation

Download the CutList Bridge User’s Guide and locate the Installation section in the index. After reviewing this section also review Installing Ruby Plugins and follow the instructions under the heading “Older versions of SketchUp and .rb files”.

CutList Bridge Tutorial Series

I have begun a series of tutorial videos to help you learn the features of CutList Bridge. Part 1 of 3 was recently released and can be found at CutList Bridge Tutorial – Part 1. Part 2 was released today and can be found at CutList Bridge Tutorial – Part 2. Stay tuned for Part 3.

Attention MAC Users

Known Issue With Version 2.5

If you are a MAC user and have the latest Safari Version 6.0.2 but do not have the latest OSX Mountain Lion installed, you will not be able to use CutList Bridge to add component attributes. Safari 6.0.2 in older versions of the OSX make text input fields black instead of white masking the black characters entered by the user. This is a MAC problem and not a CutList Bridge 2.5 problem.

However, I have provided a work around. If, after you install CutList Bridge as instructed above, your input fields show up with black backgrounds, follow these instructions:

  1. Download alternate_cutlist_bridge_css.zip by clicking on this hyperlink.
  2. Extract the file cutlist_bridge.css from the ZIP folder and move it to the folder …. \Plugins\cutlist_bridge\cutlist_bridge (note the two levels of cutlist_bridge folder). This replaces the file of the same name that is already in your Plugins file under folder \cutlist_bridge\cutlist_bridge (note again the two levels of cutlist_bridge folder).
  3. Close SketchUp and reopen it. You CutList Bridge input fields will still have a black background, but your entries will be red characters making them visible.

Models To Practice With

There are three models which you can download that already have attributes assigned. You can use these models to produce a cut list and experiment with changes to the attributes. The Shaker Tall Clock demonstrates most of the basic features of CutList Bridge. Base Cabinet, thanks to Matt Richardson and Greg Larson of NESAW, demonstrates most of the special Cabinet Mode features. SketchUp Home demonstrates a very large cut list whose Sub-Assembly names are automatically generated with the Sub-Assembly by Layer feature. Click the links below to download each model.

Shaker Tall Clock
Base Cabinet
SketchUp Home

Below is an image of a SketchUp cut list exported to OpenOffice. Not all lines are shown.

SketchUp Cut List Exported to OpenOffice


Base Cabinet With Counter Top & HardwareIn my 10-6-2012 issue of Chiefwoodworker’ Newsletter on page 15, I wrote at length about my Trimble SketchUp Ruby Script plugin called CutList Bridge (Version 2.2). As its name implies CutList Bridge permits quick and efficient cut list creation by exporting SketchUp dimensions and other key component attributes to a .csv file. This .csv file can then be imported into CutList Plus fx or any application supporting the comma-separated-value format, such as Microsoft Excel and Open/Office.

In the case of exporting to the latter two applications decimal equivalents of thickness, width and length can be exported. This permits the user to add equations in the spreadsheet to calculate board feet, area, total sheets, linear feet or weight. CutList Plus fx will do all but calculate weight on its own. The Base Cabinet shown above left produces the following cut list when exported to OpenOffice. Note the organization by material type (Rough Lumber, Dimensioned Lumber etc.), Sub-Assembly and Description (component). Click on the images to see larger formats.

Base Cabinet Cut List With Counter Top & Hardware

Downloading CutList Bridge

CutList Bridge can be downloaded and installed by following the highlighted link; the target post will always host the most recent version of CutList Bridge.

Overview of CutList Bridge

CutList Bridge adds two export commands to the File menu and one dialog box to the Window menu of Trimble SketchUp. The export commands are:

  • Export to CutList Plus fx
  • Export to Microsoft Excel or OpenOffice

The dialog box is called Extended Entity Info and as its name implies is complements and extends the Entity Info dialog box.

When CutList Bridge is installed, as indicated by the availability of these commands and dialog box, a basic cut list can be produced simply by selecting one copy of your model using the Select tool and then choosing one of the export commands from the file menu. Simple as that.

However, the Extended Entity Info dialog box can be used to assign additional attributes to your components, which will produce a richer and much more useful cut list. This first video tutorial will show you how to create a basic cut list and then embellish the cut list with material types (rough lumber, dimensioned lumber, sheet good and other items), material names (cherry, walnut etc.), sub assembly groupings and notes. Subsequent video tutorials will show you how to assign attributes helpful for cabinetry and architectural models.

Downloading the Video to Your Computer

Sometimes the performance of your internet connection, the load on it at a particular time of day, and the length of these video tutorials can all conspire to provide you a frustrating and impossible viewing experience. If this happens it may be preferable to download the entire video unto your system and view it on your local video player. The video file is an mp4. It can be viewed with most video players including QuickTime and Media Player. If you have a default, or user specified, file association for .mp4 you may have to delete it or use a download manager to download this file. Otherwise the associated application may be invoked and file streaming will prevail over downloading. There are numerous free download managers on the internet. Be careful, and do some research to locate one that is not loaded with spyware or viruses.

If you are on a PC platform running Windows OS and have Internet Explorer or Firefox you don’t have to change file association or use a downloader. Simply right click on the link(s) below and choose Save Link As. When Explorer opens choose a destination folder and select Save.

To download this video click here or paste

http://www.srww.com/downloads/blog_posts/CutList%20Bridge%20Tutorial%20-%20Part%201/CutList_Bridge_Tutorial_Part%201.mp4

into your download manager.

Viewing in Your Browser

You may find it easier to view the video in full screen mode. Start the video before selecting this mode. To enter full screen mode click the little screen icon at the bottom of the video player. When in full screen view hold your cursor near the bottom of the screen to access the video player’s controls. Exit full screen mode with the Esc key. This part is approximately 33 minutes long. Sit back, relax and enjoy the show!


Perspective View of Modeled Wing SkinA reader asked whether airplane wings could be modeled in SketchUp. Without ever having tried I confidently answered “anything can be modeled in SketchUp”.

I am an instrument rated private pilot and the question intrigued me.  I wondered how one might go about modeling a wing. So later that day I set about to develop a proof of concept. The result is shown at right. This proof of concept, or first attempt, has a number of flaws so I decided to take it to another level. In this article I will describe in layman’s language the major design parameters and trade-offs the aeronautical engineer makes when designing a wing and then I will show you hot to model it. Let me make very clear that I am not an aeronautical engineer; the definitions and explanations I give here are my lay interpretations of things I have read over the years. If you are an aeronautical engineer and take issue with anything I say please correct me by commenting to this post. That way all readers can benefit from your feedback.

I have two simple SketchUp models the reader can download for self manipulation.

http://www.srww.com/blog/wp-content/uploads/2012/11/Wing1.skp

http://www.srww.com/blog/wp-content/uploads/2012/11/Wing 2.skp

Before proceeding some definitions are in order:

Airfoil – Airfoil is the cross section of the wing sliced by a plane parallel to the plane formed by the plane’s longitudinal and vertical axis. The airfoil generally has a positive camber on the top surface, is thicker near the front edge than back edge and the leading edge is smoothly curved approaching a semi-circle.

Ailerons

Control surfaces located at the trailing edge of the wing near the wing tips. Surfaces move in opposite direction (one up and the other down) to produce roll around the longitudinal axis of the airplane.

Airspeed

The speed of an aircraft relative to the air surrounding it.

Angle of Attack (AOA)

The angle between a wing’s chord and the direction of flight (a vector parallel to airspeed).

Chord

A straight line running from the leading most point on the leading edge to the trailing most point on the trailing edge.

Drag

Forces opposing the direction of flight. Drag has two components: parasitic drag, caused by skin friction such as ice accumulating on a wing; induced drag, caused by flight attitude such as high angles of attack.

Flaps

Control surfaces located at the trailing edge of the wing near the wing roots. Surfaces are angled down in steps. Each step produces more lift until the increased drag slows the airplane to a stall speed.

Mach

Mach 1 is the speed of sound; Mach 0.6 is sixty % of the speed of sound and so on. In dry air at 20 °C (68 °F), the speed of sound is 343.2 meters per second (1,126 ft/s).

Planform

The view of a wing looking down its vertical axis.

Stall

A point reached when the airfoil no longer produces sufficient lift to overcome weight and is produced by angles of attack greater than the stall angle. Stall can be abrupt and dangerous. Essentially the wing stops flying.

Sweep

Wing sweep is usually the counterclockwise rotation of the wing in the planform view. The major advantage is to high performance planes flying near or above Mach 1; wing sweep helps to increase the maximum airspeed of the plane.

Taper

Taper can be applied to the leading edge, trailing edge or both. Wings are generally tapered such that the chord is shorter at the tip than at the root. Taper should not be confused with Sweep. The major advantages of wing taper are: reduced weight, structural integrity (lower bending moment), reduces drag. A disadvantage of wing taper is that it reduces the AOA at which stall occurs at the tip and hence may have poorer stall characteristics.

Twist

Generally a wing has lower angle of attack (AOA) at the tip than the root. The AOA usually decreases linearly from root to tip. This type of twist is used to ensure the wing stalls first at the root and last at the tip where the control surfaces are.

Wing Setting Angle

Wings Setting Angle (also called wing incidence) is the angle between the fuselage center line and the wings chord line mapped on the y-z plane (plane of symmetry). You can think of it as a built in AOA which helps to increase lift at slow speed such as during the take-off roll and climb. Typical wing setting angles are 0° – 5°.

The Airfoil and Bernoulli’s Principle

bernoullilYou probably remember basic airfoil (hydrofoil in a fluid) theory from your high school physics class. Airfoils and hydrofoils operate on the Bernoulli principle which says that as a fluid increases in velocity it is accompanied with a decrease in pressure. You have seen this in action many times in your daily life. As you drive a pickup the air flows over the top at a speed roughly equal to the speed of the vehicle. The air behind the back window, in the bed of the truck, is still; not moving at all. As a result things sitting in the bed often are lifted up toward the fast moving air overhead. Indeed, the whole backend of the truck experiences some lift and makes the back of the truck a little “lighter” creating problems for the driver in wet or icy conditions.

angle_of_attackThe airfoil takes advantage of this phenomena (or more accurate one of the many laws of physics). You have probably experimented with a sheet of paper as an airfoil. If not, hold a piece of printer paper between the thumb and forefinger of your right and left hand at the end of the paper. Pull on the paper to take out the slack at the end. The rest of the paper will fall limp. Bring the paper to your lips with your lips just above the paper. Now blow steadily and easily. Notice the paper lift slightly. Now blow steadily and harder. Notice the paper lift more. The harder you blow the more the paper lifts. This is the Bernoulli principle at work. Fast moving air on the top side of the paper produces lower air pressure and results in lift being produce in the direction of high pressure (beneath the sheet) to low pressure (above the sheet).

The airfoil of an airplane wing (and many bird wings) is wider in the from with the front edge being round or curved, and tapering to a very thin edge at the back. The top surface generally has a camber and the bottom surface is generally flat. See the second image above. Oncoming air is moving at the air speed of the airplane and separated at the leading edge. As air that moves over the top must travel a longer distance to meet up with the air moving beneath the wing, it must must travel at a faster speed than the air on the bottom. Therefore the relative pressure is greater above the wing and hence lift is produced at the bottom of the wing.

In the second image above you will notice that while the distance air must travel at the bottom is less than at the top, it is still greater than the straight line distance from leading edge to back edge. Aeronautic engineers often build in a slight angle to the airfoil, called angle of attack. This has the effect of decreasing the distance that must be traveled on the bottom, and hence increases the top edge distance. This means the resulting total lift will be greater. However, if the angle is too large the face of the bottom of the wing will be presented to the oncoming air and produce excessive drag. So there is a delicate balance that must be achieved. See the third images above. Notice that the total lift is still perpendicular to the bottom surface of the plane (oversimplification) and now has components of airplane lift and drag. Airplane lift is opposite the pull of gravity while a small amount of drag tries to slow the plane and is opposite the planes travel. If the angle of attack is optimum there is sufficiently small drag such that the airplane lift is still larger than if there were no angle of attack.

This description of lift doesn’t mention downwash at the trailing edge of the wing. This downwash assists in generating lift. Lift is a complex issue when thoroughly treated and has many components. My description is admittedly simple, but still useful for basic understanding.

Modeling the Airfoil

airfoil#0_dimensionsDrawing on my early pilot training on wing design I started with an airfoil profile; essentially the cross section of a wing. Airfoils come in many shapes. In this article I am modeling a basic airfoil which only requires three steps. The picture at left shows the three perimeter portions of the airfoil. I start with a semi-circle to the left of points a and b with a radius of 12” (2 foot diameter). At the bottom of the semi-circle I extend a line 96” (8 feet) from point b to c. From a to c I use the Arc tool with a Bulge of approximately 6 5/64” (a radius of approximately 204 17/32”. The dimensions of this airfoil may not be efficient, indeed may even be a poor design. However, it does have all the characteristics necessary for flight: the front edge is smooth and curved, the trailing edge comes to a point, and the air must travel a greater distance on the top surface than it does on the bottom surface. This is a basic but not atypical airfoil. When completed I make this airfoil a component called Airfoil#0.

Modeling the Wing Setting Angle

At this point a wing setting angle can be modeled by simply rotating the airfoil around an axis perpendicular to the airfoil surface and running through the tails trailing edge (point) See the third image in this article.

General aviation airplanes have wing setting angles of 2° – 4°. Commercial airliners may have wing set between 3° – 5°. Supersonic fighters have very shallow wing set between 0° – 1°. Flying wings are considered to have no set because they have no fuselage.

The wing I modeled here has an exaggerated 8° wing set to make it more visually apparent in my images.

Tapering Wings for Stability and Structural Strength

extruding_the_airfoil

Wings are often tapered so that they are smaller at the tip than they are at the fuselage. Lift generated at the tips of the wing have much more influence (torque – ft-lbs) on the plane around its longitudinal axis than lift near the fuselage. The ailerons are placed near the tip of the wings and to manage aileron response stability the wing tips are tapered and hence produce less total lift.

Creating the wing shape is a series of tedious steps, one which would benefit from a Ruby script, which I might write one day but not for this article. First I need to create a number of airfoils; remember an airfoil is a cross section of a wing. So I need enough cross sections, evenly spaced to give me a smooth wing shape. My wing, when finished, will be approximately 35’ in length so I arbitrarily choose to create 33 additional airfoils, spaced 1’ apart, and each one smaller by a factor of 0.98. Also, when done I want the trailing edge to be a straight line. To do this I use a combination of the Move/Copy, Scale and Make Unique tools thirty three times (this is where a Ruby script that recorded a sequence of steps and repeated them N times would help). First I use the Move/Copy tool to copy and move the previous airfoil to the left one foot. Next I use the Scale tool to uniformly scale about the opposite point a factor of 0.98. The “opposite point” is the point at the trailing edge. This will keep the trailing edges lined up along a straight line. Finally I use the Make Unique command on the Context menu to make a new component, each sequentially numbered. I now have thirty four airfoil components named Airfoil#0 through Airfoil#33.

Wing Twist to Improve Stall Characteristics

Many wing designs include wing twist; gentle continuous rotation of the wing along it length. The direction of twist has a profound effect on the planes stall characteristics. If the wing is twisted counterclockwise, when viewed from the tip and looking at the root, the wing tip will have a lower angle of attack than the wing root. Recall that wings stall – wing stops flying – when the stall angle is reached. Once the wing stops flying the pilot has little or no control of the plane.

Wings with twist don’t stall at the same time along the wings length, rather the roots stalls first because it has a larger set angle than the twisted wing’s tip. Hence stall progresses from the root outward to the tip as the AOA increases.

Ailerons, the roll control surfaces, are located near the tip of the wing. So it is desirable for the tip of the wing to remain flying (not stalled) as long as possible when the planes angle of attack reaches the stall angle. Wing twist assures this occurs.

wing_twistModeling twist is a simple matter, though a tedious one, of reducing each airfoil’s set angle a fixed amount relative to the previous one starting at the root and working toward the tip. In the case of the wing I modeled here, Airfoil#0 has a set angle of 8°. Each following Airfoil has a set angle reduced from the previous by 0.2° resulting in Airfoil#1 having a set angle of 7.8°, Airfoil#2 7.6°, Airfoil#3 7.4° down to Airfoil#33 1.4°.

In practice this can be modeled by selecting Airfoils #1 – #33 with the Select tool. Reduce their set angle by 0.2°. While all 33 airfoils are still selected use the Select tool with the Shift key to deselect Airfoil#1 leaving Airfoil#2 through Airfoil#33 still selected. Now use the Rotate tool to reduce the selected airfoils set angle by 0.2°. Now deselect Airfoil#2 leaving Airfoil#3 through Airfoil#33 still selected and reduce their set angle by 0.2°. Repeat this process for each airfoil down to and including Airfoil#33.

Airfoil#33 will have a set angle of 1.4°. Starting with Airfoil#0 with a set angle of 8° and subtracting 33 reductions of 0.2° equals 1.4°. The finish twisted will will look like the image at above left.

Modeling the Wing’s Skin

wing_skinWe now have the airfoil cross sections and we can use them to create the wing. I only model the skin in this article; not the internal structure called spars and ribs. Nor do I give the skin thickness. These can be modeled quite easily once the airfoils and skin have been modeled, and I will leave that exercise to the student.

Recall that the beginning airfoil was constructed with a semi-circle, straight line and an arc. SketchUp models circles and curves with line segments. Each line segment has endpoints which the inference engine will point out when you hold your cursor over it. I connected these endpoints with straight lines to produce the mesh of rectangles shown in the picture above right. Again this is tedious and repetitive but doesn’t take too long.

triangulated_wingIf wing twist is modeled the above process gets even more tedious. With wing twist no four points will form a plane – the wings twist ensures that. So the skin must be modeled with triangles; three points will always form a plane. The image at left shows the hidden geometry of a twisted wing.

Note that the wing tip is modeled using the Follow Me tool to create and one quarter sphere, then using the Push/Pull tool to extrude the one quarter sphere and finally using some hand stitching and cleanup.

Swept Wing Design for Higher Air Speed

Swept wings should not be confused with tapered wings described above. Wings are swept – angled toward the tail – on high performance planes including corporate and airliner planes. The reason is simple; swept wings allow a plane to fly faster. How a swept wing works is not simple and in-depth understanding requires a degree in aeronautical engineering. I will attempt a significantly oversimplified explanation to give you some basic understanding.

sweepAs a plane approaches the speed of sound, Mach 1, there is a speed lower than Mach 1 where, due to the complex shape of an airplane, some parts of the plane reach Mach 1. That is some areas of the plane reach Mach 1 before the plane’s airspeed is Mach 1. Shock waves appear at those points and produce drag rather abruptly and increases rapidly. These shock waves limit the speed the plane can fly. The critical Mach number (Mcr) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound. This might be a number such as Mach 0.75. To increase the speed of the aircraft the aeronautical engineer has to increase the effective Mcr. Enter the swept wing.

The Mcr of a non-swept wing is a function of the airfoil design; principally the chord line of the airfoil cross section. Before a wing is swept the chord line is parallel to the travel of the airplane and aligned with the planes airspeed. When the wing is swept the chord line is at an angle to the airspeed. The airspeed now aligned with the cord line is a fraction of the airplanes airspeed, and is proportional to a leg of the right triangle of which the chord line is the hypotenuse and the angle between the hypotenuse and leg is the sweep angle. Now the airplane can accelerate to a higher airspeed before the airspeed component parallel to the airfoil chord reaches Mcr.

As stated earlier, this is significantly oversimplified. Not all of the theoretical advantage of sweeping a wing is realized because of other effects such as skin friction and fuselage drag. In fact some supersonic aircraft do not use swept wings, such as the Lockheed F-104 Starfighter which reaches airspeeds of Mach 1.7 with straight wings.

Modeling wing sweep is a simple matter of using the Rotate tool to rotate the wing around a pivot point near or at the root. This angle is usually small but can be aggressive and deep on high performance military aircraft.

Dihedral Design for Roll Stability

dihedralAnother very important design property is dihedral. Some plane wings slant up at the tip (dihedral) and some slant down (anhedral). When dihedral is designed into a plane wing it increases roll stability (stability around the longitudinal axis). Cross wind gusts tend to push one wing down (or the other up). When this happens the lower wing has a greater attack angle and presents more surface area in the direction opposite gravity. This cause the lower wing to produce more lift which opposes the rolling effect of the wind gusts. Dihedral is often used on small general aviation aircraft because this built in stability is rather inexpensive and tends to keep the inexperienced private pilot out of trouble. Anhedral is sometimes used on high performance planes for other advantages, but it is less stable. However, high performance aircraft have expensive and extensive computer sensors that can detect wind gust roll and generate computer controlled responses that can increase stability.

Modeling dihedral, like sweep, is a simple matter of using the Rotate tool to rotate the wings up around a pivot point near or at the root. The angle is usually small, maybe 5° or so.

Completed Wing Skin Model with All Major Attributes

completed_wingAfter modeling all the major attributes of a wing skin I ended up with the image at right. I used the Eraser tool with the Ctrl key to hide most of the lines including diagonals. The remaining lines simulate the edges of the aluminum sheets a wing skin is made of.

If I were an aeronautical engineer designing a real wing I would use this skin to model the spars, ribs, aluminum sheet thickness, rivets, ailerons, flaps, fuel tanks, wing tip lighting and so on. My purpose here was to point out the type of modeling techniques one might use to model a fairly complex shape.

This modeling task included a fair number of tedious and repetitive steps that would benefit from a Ruby script to produce Macro capability (memorize a sequence of steps and repeat them 1 to N times). Writing such a Ruby script would take much longer than executing the tedious modeling, and I doubt I would find the tool useful in many of the models I tend to work on. So overall it would be a waste of time. Modeling is often like that; it often pays to do things the simple and tedious way.

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