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SketchUp Make and Pro 2014 brought with it many improvements including the upgrade from Ruby 1.8.7 to Ruby 2.0 for its Ruby API and Plugins. Like most improvements, there are some casualties and collateral damage. I had hoped that CutList 2.6 release fixed all the SketchUp 2014 and Ruby 2.0 compatibility problems, but users have found a few more. So today I am releasing CutList Bridge 2.7.

Very Important – Please Report All Problems To: jpz@srww.com

CutList Bridge:

  1. Download the CutList Bridge User’s Guide.pdf file to a location you will remember e.g. your desktop. This file is a User’s Guide. Read the “Locating Your Plugins Folder” section and the “Installation” section very carefully.
  2. Download the cutlist_bridge_revision_2.7.rbz file to a location you will remember e.g. your desktop. Follow the installation instructions above.

It’s out and it’s disappointing. If you are a free version user of SketchUp you have a new name to deal with for 2013: SketchUp Make. In addition you are more restricted in your use of SketchUp Make; you can not use it for business or profit oriented activities in any way. Other than that, you don’t have much to look forward to from a user interface point of view. It is quite possible that SketchUp Make (and SketchUp Pro) are a lot faster in some applications and hopefully more stable and less buggy. But the jury will be out on that for some time.

SketchUp Pro has some new features that are nice in the LayOut application; most notably you have cross section fill capability. But there is very little in the SketchUp application itself of import.

Higher price, uglier icons, still Ruby 1.6 internally even though Ruby is up to 2.0, no improvement in Ruby console (I thought sure Unit Test would make it in there) etc. etc. etc. Let’s hope they did something of value when they expose the under the hood changes. Right now, very disappointing.

The one thing that is obvious is the toolbar set up. You can now set up your toolbar with its own dialog box and when you collapse the window the toolbars and position is returned when the wind is expanded, Nice, but setting up the tool bar is a onetime thing and I could easily have lived with the old method. And Save Toolbar Postions worked quite nicely. What I don’t like about the new toolbar behavior is that I can’t place a vertical x 2 column on the left or right side. It forces a x 1 horizontal column when I try.
The fill capability in LayOut is nice, but it would have been better if it were integrated into the Section tool in SketchUp. I haven’t checked my list of bugs yet, but I bet when I do printing to scale and printing extents still isn’t fixed; a problem that has existed since the beginning of time. So far Trimble gets a failing grade from me for its influence on SketchUp.

I hope I have to retract or alter my First Blush opinion on SketchUp 2013. Trust me, I would happily do so it warranted. But I am not hopeful.


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.


You may not be aware, but there is a free application called OpenOffice that is largely equivalent to Microsoft Office. It can be downloaded at http://download.openoffice.fm/free/ . One note of caution; there are a few extra applications that get installed with OpenOffice that are marketing data gathering software. You are supposed to be able to opt-in at install time, but the opt-in process is so obscure that most people will miss it. However, you can remove these application after installation if you miss the opt-in process.

OpenOffice Text Import Dialog BoxI have downloaded Open Office and gave it a test drive with CutList Bridge 2.0. It works with one very minor problem. First, when exporting from SketchUp use the File/Export to Microsoft Excel command. Next, when importing to OpenOffice Spreadsheet use the File/Open command with All files (*.*) selected for Files of type:, and then a dialog box will appear. See the image on the left (click to enlarge). Clear any single quote or double quote (‘ or "") in the Text delimiter drop down box. You don’t have a choice of blank in the drop down, but just select any character(s) in that box and delete them. Make sure you have the Comma check box selected and none other. Hit OK and you will get a cut list similar to that shown in the image at right.

CutList Bridge 2.1 Cut List Imported To OpenOfficeThe double quotes in the left hand column should not be there. They are a result of a bug I have in my script which Excel overlooks, hence I have never seen it. I will fix it in the next bug fix release. This bug does not affect either CutList Plus or Excel. Simply select these cells and delete their content.

So far I am quite impressed with Open Office. I don’t know why I haven’t tried it before today. If you are looking for a complete free solution from 3D modeling of woodworking projects to shop cut lists then the combination of SketchUp, CutList Bridge 2.0 and OpenOffice is your answer.


Assign Attributes TabAt the suggestion of Greg Larson, owner and operator of the New England School of Architectural Woodworking, and with his help, I have developed a cut list export tool for SketchUp. Why another cut list tool? Don’t we have enough already? Well, this has some unique features that are tailored to architectural cabinetmaking design and build, though these features can be used for all types of woodworking models.

This release is Revision 1.0. It comes with a CutList Bridge User’s Guide that will explain 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 with this link. Please report all strange behavior or bugs to jpz@srww.com and don’t hesitate to write if you need help.

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

Happy Bridging!

Major Features of CutList Bridge

1. Seamlessly bridges SketchUp and CutList Plus fx or Microsoft Excel
CutList Plus fx is a highly functional cut list creator, costing tool, proposal generator and inventory manager for woodworking shops. Google SketchUp is a powerful 3D drawing tool ideally suited for furniture and architectural cabinet design and photorealistic rendering. These two tools do not naturally work together. CutList Bridge solves that problem by seamlessly bridging these two applications. If you do not use CutList Plus fx, no problem. You can export your cut list to Microsoft Excel.

2. All cut list attributes are entered in SketchUp and remain with the model file
CutList Plus fx requires the user to manually re-enter dimensions and other component attributes such as material type, material name, notes and banding. Attributes that can be generated automatically from the design’s 3D model and which ideally belong with the design file. CutList Bridge allows the user to enter and store all attributes with the model file and provides features for editing and exporting. Attributes which can be automatically generated from the 3D model, such as component dimensions and grain direction corrections are also handled in CutList Bridge.

3. Sub-Assembly names can be assigned in SketchUp explicitly or automatically by Layer name
In CutList Plus fx a Sub-Assembly name is typically used to group a collection of components. For example: in a model of a chest-of-drawers you may want two Sub-Assembly names; one called Carcass for all the components that make up the basic support structure, and one called Drawers for all components that make up the drawers. A grandfather clock may have Sub-Assembly names of Hood, Waist and Base. A trundle bed might be divided into Headboard, Footboard, Sides and Trundle. A kitchen cabinet may have sub-assemblies of Cabinet, Face Frame, Drawers and Doors. CutList Bridge allows the user to assign Sub-Assembly names in SketchUp prior to exporting to CutList Plus fx.

Sub-Assembly names can also be assigned by layer using the layer’s name. For example, as stick frame house designed in SketchUp may be organized with layer names such as Footing, Foundation, 1st Floor Joists, 1st Floor Framing, 2nd Floor Framing etc. These layer names can automatically be used as the Sub-Assembly names in CutList Bridge fx.

4. Assign oversize/undersize dimensions in SketchUp via the Cabinet Mode Resize feature
Lists Tab<Info> is a CutList Plus fx field that is intended as a short note. However, it has two significant differences from the Notes field provided by CutList Plus fx. First, <Info> shows up in the CutList Plus fx spreadsheet whereas Notes only appear on the Parts printout. Second, if a CutList Plus fx spreadsheet is locked to prevent accidental change, <Info> can still be changed allowing for cutting status to be input. See the CutList Plus fx User’s Guide for more information.

CutList Bridge extends the use of <Info> when used in a special mode called Cabinet Mode. In Cabinet Mode parts can be oversized or undersized in length and width using the Resize feature, and these dimensions will appear in the CutList Plus fx <Info Field>. The user has the choice of displaying the increment of over/under size or the over/under sized finished dimension for each of width or length.

5. Assign Notes in SketchUp while designing the model
Notes can be assigned in SketchUp for each component. These will be exported to the Notes field in CutList Plus fx.

6. Both Milled Parts and Other Items are supported
CutList Plus fx supports two classes of components: Milled Parts, which are typically Rough Lumber, Dimensioned Lumber or Sheet Goods that are milled into a component in the shop. CutList Bridge also supports Other Items such as drawer pulls, consumables such as screws, biscuits, dominos or any other non-milled components which are typically purchased.

7. All Milled Part attributes can be assigned in SketchUp
Milled Parts, as mentioned, are components milled from Rough Lumber, Dimensioned Lumber or Sheet Goods. Each Milled Part component can be assigned the following:

a. Material Type – Rough Lumber, Dimensioned Lumber or Sheet Goods

b. Material Name – e.g. Tiger Maple

c. Banding – A code to indicate which sides are banded and which banding material to use.

d. Swap L/W – The user can specify in SketchUp any component whose length and width should be swapped. CutList Plus fx assumes the length field specifies the grain direction. However, there are times when the short dimension of a board should be the grain direction. Check Swap L/W to accomplish this.

e. Can Rotate? – Many material types have no grain. To assist CutList Plus fx in optimizing material use you can specify in SketchUp which Components can be rotated by CutList Plus fx.

8. Cabinet Mode provides Auto-Swap of L & W and Over/Under sizing of cut list parts
Setup TabCabinet Mode is a sub-mode of Milled Parts. It is selected in CutList Bridge by checking its checkbox. When selected <Info> is no longer available in the usual way. However, when selected another very useful and key option becomes available in addition to three more fields.

a. Enable Auto-Swap – This is a feature that automatically determines which components should have their lengths and widths swapped, independent of dimensions, based on a Component’s Type. In cabinet design there is a basic box with components that can be labeled Back, Bottom, Shelf, Side or Top. Based on these attributes L & W will be automatically swapped when needed such that grain runs up a side, across a top, down a side and across the bottom to the starting point. Back grain will always be in the vertical direction. Shelves will have a grain direction that is horizontal (side to side) while its cross grain direction is perpendicular to the Back’s plane.

b. Component Type – As mentioned is assigned with a drop down list and can be either Back, Bottom, Shelf, Side or Top.

c. Resize Width By – The user can specify a dimension to resize the width by (the increment, or decrement when preceded with a minus sign). The Width column in CutList Plus will contain this resized dimension.

d. Resize Length By – The user can specify a dimension to resize the length by (the increment, or decrement when preceded with a minus sign). The Length column in CutList Plus will contain this resized dimension.

The user is able to choose display options for the <Info> and Description fields that will modify what information appear in these fields in CutList Plus fx. More on this later.

9. Other Items can be specified while modeling in SketchUp
Components that are not milled in the shop, but are purchased, may be specified in the Other Items’ Item field. If the name specified in the Other Items’ Item field exists in the Raw Materials library of CutList Plus fx this component and its quantity will be appropriately categorized and added to the BOM in CutList Plus fx. If the name specified does not exist in CutList Plus fx it will still be imported but added to the [Not Categorized] Other Items category.

10. Exporting is a Selection and One Menu Command
Exporting a .csv file from SketchUp is as simple as selecting a complete model and choosing menu command File/Export to CutList Plus fx. That’s it. A .csv file is generated with the same name as your .skp model file name and placed in the same folder.

A Completed CutList Plus fx Cut List


Dovetailed Components Interface WindowOccasionally I update the tools in the Construction Plus toolbar; usually with fixes and minor modifications. This time, in addition to such changes, Dovetailed Components has been significantly enhanced. In addition to drawing drawer sides for traditional drawers automatically, it now draws contemporary drawers and tailboards automatically too. Contemporary drawers are much more common in today’s furniture and tailboards are useful in constructing carcasses, grandfather clocks, jewelry boxes, blanket chests and much more.

With this release I have included a short User’s Guide. When you download construction_plus.zip and install it, by extracting it to the Plugins folder, you will find Dovetailed Components User’s Guide.pdf in the C:\Program Files (x86)\Google\Google SketchUp Pro 8\Plugins\dovetailed_components directory. Of course, your directory will be somewhat different depending on your platform (MAC or PC), Operating System version and SketchUp version and license. So adjust accordingly.

I hope you find this tool useful. I have ambitious plans for its evolution; Dovetailed Components will eventually model the entire drawer, including front, back and bottom. In addition it will allow for custom tails and pins with unequal spacing. In the meantime enjoy this version.


OK, a little dramatic, but I had to get your attention. We all know how difficult it is to manage SketchUp layers; specifically which layers primitives reside on. The biggest problem newbie SketchUp users have, bay far, is spreading primitives over layers, often multiple layers, other than Layer0. I wrote a script called layers.rb or Layers Manager. That tool does several things, but most importantly it warns you if you try to make a layer other than Layer0 active. Making a layer other than zero is a major cause of modeling problems.

However, there are numerous ways to get into trouble besides changing the active layer. In fact SketchUp seems to want to help you get into trouble. If you have a group or component instance which resides on a layer other than zero, but whose primitives are correctly residing on Layer0, and then use context tool Explode, SketchUp will move the primitives to the layer the group or component instance was on. Let’s say I have a component called Cube, and I place it on Layer Cube after first drawing it and making it a component on Layer0. Cube will be a correctly formed component; its primitive will be on Layer0 and Cube will reside on Layer Cube. As I make Layer Cube visible or invisible my Cube component will be displayed or hidden.

Now suppose I decide to explode Cube using the context menu Explode tool. I select Cube and Explode it. Cube (that instance of it, not the library component) will be deleted, but in its place, on Layer Cube will be all the primitives that belonged to Cube and was originally on Layer0. Why is SketchUp so helpful? I don’t know.

Fortunately Steve gave us two context tools. One called Explode to Layer 0, which works the way Explode should work; it deletes the group or component instance while leaving its primitive on Layer0.

The second tool is even more helpful. If you get well into a model before you discover you have major spreading of primitives, don’t panic. The solution is only one two clicks away. First use the select tool to select all groups and components in your model. Next context click and choose Primitives to Layer 0. This tool will examine each group and component in the selection, recursively drill down if any are hierarchical, and place all primitives on Layer0. It will leave all groups and component instances correctly formed independent of the layer they are on. I highly recommend making this tool a part of your Ruby script plugins.

Download the To Zero Tool

You can download the To Zero ruby script by clicking here. This is a compressed file and needs to be unzipped or decompressed. Simply extract it to your Plugins folder.

If you find this tool as useful as I do please drop Steve a line and let him know. You can get contact information by visiting his website, http://www.slbaumgartner.com/, and while you are there browse his gallery of fine furniture.

Viewing The To Zero Video

You can view the To Zero video by pressing the play icon below or by downloading it to your system.

The video file is 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 Introducing SketchUp Tool Face To Face click on or paste

http://blip.tv/file/get/Chiefwoodworker-SteveBaumgartnersToZeroSketchUpTool108.mp4

into your browser or download manager.

Full Screen Viewing

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

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