May 23, 2014 | By Don Foley

Background: The "double bubble" future aircraft design concept is created by the research team led by the Massachusetts Institute of Technology for an 18-month NASA's research effort to visualize the passenger airplanes of the future.

The Double Bubble future aircraft design concept | NASA

With a modified tube and wing with a very wide fuselage to provide extra lift, the Double Bubble is designed to do the same work as a Boeing 737-800. The concept also uses composite materials for lower weight and turbofan engines with an ultra high bypass ratio for more efficient thrust. The team said the Double Bubble's unusual shape gives it a roomier coach cabin than the 737, and it will use 70% less fuel.

The Double Bubble is among the designs presented in April 2010 to the NASA Aeronautics Research Mission Directorate and NASA says it could enter service in the 2030-2035 time frame.

Online magazine Popular Science gave Don Foley, master illustrator and visual journalist, an assignment to illustrate a concept plane for the magazine. Here is his story:

Final print of the NASA/MIT "Double Bubble"

When Popular Science assigned Don Foley to illustrate a concept plane for the magazine, he saw it as an opportunity to showcase his latest skill-set: 3D printing. Don's work has published in Popular Science since 1996 and this is the first time he has offered 3D printing in conjunction with his illustration. As far as Don knows, no one has done this before.

Initial Model

The model for the project would be used twice. Once for the magazine illustration and once to create the geometry for the 3D print. The goal was to build the model so it could satisfy both needs. To create the model Don used the 3D modeling, rendering and animation system he uses for all his current work, Lightwave 3D. The latest version of the program, 11.6, now supports 3D printing, so the timing was perfect. Don could have used any number of programs to create the model, many of them, like Blender, are free. But Don switched to Lightwave in 2004 and creating 3D geometry has become second nature to him. While the program isn't perfect for creating models for 3D printing, its many pro's outweighed the cons and finding work-arounds with issues that came up wasn't too much of an issue.

The plane render

While building the model it occurred Don that maybe there was a way to use the texture maps he had created for the illustration on the 3D printed version. When he was a kid he built countless model airplanes, and much of the details were done with decals supplied with the kits. Could he print his own decals? A Google search of "print my own decals" quickly showed that this is very common in the model making world for everything from model train to RC enthusiasts. A short visit to Amazon and several packs of transparent decal sheets were ordered and would arrive in a couple days. Gotta love Amazon Prime!

Render of the model setup to print

When printing with a FFF (fused filament fabrication) 3D printer, there are a few things to keep in mind. One critical concern is that the printer lays down one thin layer at a time from what can be compared to as a really small glue gun. Each layer is about as thick as a sheet of paper. As the printer lays down a layer, it needs to print on something, it doesn't like printing on thin air. So you either build up on the same object, or you can use supports. Most FFF 3D printers will forgive you up to about a 45° angle. So to create this plane, Don divided the main hull of the craft in half so the body could print vertically upon itself. The same would go with the wings. To take advantage of the fact that the plane could be taken apart, Don decided to make it a "3D Printed Infographic," to that end he created rows of seats so people could see what it would look like on the inside.

Simplify 3D user interface

Once the model is built, a STL file is exported from Lightwave and opened in a program where the printer parameters can be set. Don likes to use Simplify 3D because of the level of control that it allows. Many variables determine the quality of the final print, including print head speed and layer height. These variables and about 80 others can be adjusted in this program.

The WanHao Duplicator 4 3D printer, printing out the Double Bubble

Once the file has been 'sliced' into the many layers that will create the final build, these instructions are sent to the printer. In Don's case he outputs an .X3G file, puts it on an SD card and plugs the card into the printer. The printer could be controlled directly from the computer, but if the computer fails or the program is accidentally exited, it would ruin the print. Because of this Don likes to use the SD card.

To print the plane, Don used his WanHao Duplicator 4 and printed it with PLA plastic. He bought the printer and his materials from Don is a big fan of the Duplicator, it takes his abuse and yet continues to crank out quality high resolution prints.

Getting prints to stick to the bed can be tricky. After much experimentation Don found that Scotch painter tape, scrubbed with isopropyl alcohol worked perfect for him. This model was built using PLA plastic, a corn-starch derivative. He doesn't apply any heat to the bed and uses a nozzle temperature of 205°. The nozzle size is .4 mm and the layer height is 0.17 mm with a print speed of 3500 mm per minute. The resulting file takes about 15 hours to print.

The printed plane still on the bed.

The next step was building the plane. To assemble the two sections Don created an internal 'sleeve' with slightly raised 'friction ridges' on all sides. This would hold the craft together without glue, and allow the user to pull it apart.

The plane before assembly, you can see the biscuits in place on the wings

Don also created small 'biscuits' to fit into the wings and stabilizers to position them for future gluing. He uses Loctite Super Glue Ultra Control Gel to assemble his 3D prints.

The plane on Don's build table

With the plane assembled, Don turned his attention to the decals. He created the artwork in Adobe Illustrator and then brought the file into Photoshop to tweak it and to save the file as a PSD file which can be used both for image mapping on the 3D file in Lightwave as well as printing on the decal sheet. Both of these could be done in Illustrator alone, but Don is a creature of habit and he's used to processing his image maps in Photoshop.

Decal sheet design

The Testor decals come in half-sheets, which is about as small as you can get something through an ink-jet printer. Don set up enough decals to take care of 2 planes and threw in a few extra items for good measure. He'd be sending this plane up to the creative director at Popular Science, so for kicks he put the name of their parent company on it. After printing out the sheet he sprayed three coats of spray lacquer on it, allowing it to dry between each spray. Inkjet ink is water soluble, so you need to spray lacquer on it to 'fix' it to the decal sheet. Once dry, you trim out the pieces you want individually and drop it into a small bowl of water for about 10 seconds. Blot it off with paper towel and slide the decal off the paper backing and carefully into place. Clean your model first. Don found if any oil from your hand gets on the plane, the decal might not stick. Don cleans it with isopropyl alcohol on some paper towel.

The final plane with a basket of parts for the next plane to assemble

With the final plane done, Don sprays it with a final coat of lacquer to help stabilize the decals. The print is done! To complete the process, Don creates a 'how to assemble' diagram of his creations.

"How to Assemble" diagram

This model can be purchased directly from Don for $15 at his store. You can download the design files for this 3-D model in .LWO.OBJ, and .STL, file formats. 


Posted in 3D Printing Applications


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Sheffdog wrote at 6/15/2014 7:33:32 AM:

Great Job Don! Adding the decals definitely adds that extra touch that makes the model really stand out. I would love to print that sucker out when I get a 3d printer.

Don Foley wrote at 5/28/2014 3:19:27 AM:

TheJ, Nope. I'm sure that in the real world scale, my walls would be several feet of plastic. I actually made it more dense than it needed to be, but it was one of the first models I built for 3D printing. I built it back in March when the assignment came in. Later models are MUCH thinner. But it does have a nice 'bulky feel.' I'm sure it wouldn't glide un-powered. A jet engine designer once told me that they could strap a modern jet engine onto the side of a barn and it would fly, they are so powerful. I'm sure the X-Plane folks will work up a design for this. When I get bored I fly X-plane on my i-Pad!

TheJ wrote at 5/27/2014 9:05:28 PM:

Don, have you considered FLYING the model? If not in real life, why not in X-Plane? Does the printed model glide?

Don Foley wrote at 5/27/2014 4:31:41 PM:

Chris, That's cool. I bought the printer because I figured I needed to dive in at some point and picked what I thought would be an entry level FFF printer. I was amazed how good it printed. So now I'm a big fan. Lots of people add mods to it, but since I'm selling my models, I want to stick to a stock machine.

Chris wrote at 5/24/2014 3:40:53 PM:

Don, apologies, I was only laughing at the name and look of the printer, not the quality.

test wrote at 5/24/2014 5:51:25 AM:


Don Foley wrote at 5/24/2014 5:39:46 AM:

Chris, I will match my Duplicator output against any machine on the market. You may say "hahaha" but I would be happy with 2 Duplicators over one Replicator. My work is out there. My clients love my prints. If I thought I needed a better printer, I'd buy it. I don't think I do. When a better printer comes out, I'll buy it. Right now...I'm happy with my 'hahaha' printer that outputs great prints. It's a solid machine and I have thousands of hours on it. It runs around the clock and I seldom have a failed print (and if I do, it's usually a design error on my part). What printer do you have? Knightfire, That's cool. You always have Thingiverse. I build models for a living. It would be a bit of a struggle to pay the bills if I gave my art away for free. I am thankful for the many folks who have no problem paying for my builds. My boat mechanic feels the same way.

Chris wrote at 5/24/2014 12:40:39 AM:

Wanhao Duplicator 4! hahaha

KnightFire wrote at 5/23/2014 9:08:50 PM:

$15us!?! No thanks!

Anja wrote at 5/23/2014 7:17:51 PM:

@TK: Thanks! fixed. Appreciate your help.

TK wrote at 5/23/2014 7:03:08 PM:

Typo in "Blot it off with paper town". Makes more sense with "towel". I like this idea of making your own toys.

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