Mendota Map: the Making of a 3-D, Magnetic Map

I, Caroline, personally worked on every single step, but I had a lot of help along the way.

This post is a brief overview of how the magnetic Mendota Map for the Wisconsin Hoofers was built… 

Here’s a link to my post about the completed project and the design choices that shaped it. 

Reading through this summary, the procedure may seem straightforward… In practice, every step was a process of weighing the options, testing with scrap material, often attempting repeatedly to get it right, and second-guessing the choices afterward.

I had a lot of help putting this project together. I would especially like to recognize fellow Hoofers: Dennis Mossholder, who suggested all of the right materials, and Eric Oberhart, who did all of the text label design. Justin Randall helped with every aspect of the project, from power tools to emotional support. Finally, the Sector 67 workspace staff and members were instrumental in accomplishing the project.


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Workspace and equipment sector_logo

Throughout the project, we used equipment at Sector 67 (, a community workspace on the east side of Madison. For the cost of a monthly membership, I had access to a laser cutter, a full woodshop with 4-by-8-foot  CNC router, and countless other tools, as well as guidance on how to use them.

The photos posted with This Union Reinvestment Blog Post ( offer a nice glance at how the software, tools, and people at Sector67 helped make this map possible.

Mark_DSC_0152 Mark_DSC_0171 Mark_DSC_0112


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Building a Model     (October 2013) 

We started by building full-sized cardboard model, cut out of single-ply cardboard using the Sector 67 laser cutter.  Modeling the piece helped me grasp the idea of the map as a full-sized object. The model would later prove helpful in explaining what we were building.

Using the Sector 67 laser cutter to cut out a cardboard model
Using the Sector 67 laser cutter to cut out a cardboard model
Taping together the cardboard model
Full-sized cardboard model at 50 inches tall and 56 inches wide
Laser cutter in action

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In the early planning stages, I had a lot of help from fellow Hoofer and experienced craftsman Dennis Mossholder, who suggested several of the materials ultimately used in the map. He recommended Baltic Birch for the wood components and found a product called Magnetic Laminate (HPL#150) from the company Chemetal to create a surface which would attract magnets. It’s a laminate composed of an iron foil sandwiched between layers of a paper & resin material. Only 1 mm thick and lightweight, it attracts magnets like metal but can be cut using woodworking equipment. We laminated the Chemetal material to a backing of 3 mm Baltic Birch plywood using contact cement. The wood added support for the thin, floppy Chemetal laminate.

rolling contact cement onto the wood
rolling contact cement onto the wood
sheets of dark magnetic material attached to the light-colored wood

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Cutting      (November 2013) 

I used data from the Wisconsin DNR to produce Mendota’s lake depth contours at 10 foot intervals. We used a 4 by 8 foot CNC router at Sector 67 to cut the stock material into layers of lake depth. One depth contour was cut from each layer of material.

The Sector 67 CNC router cutting into our stock material
CNC router cuts the magnetic laminate/wood
CNC router cuts the magnetic laminate/wood
Before sanding: the pieces as they come off the CNC router
After sanding the edges (all by hand)
Deeper lake layers on the CNC router bed, as seen from above
All lake pieces on the CNC router bed, as seen from above
All material pieces are cut out!

For some video footage, check out:


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Painting      (January- February 2014)

After cutting out the map pieces, we needed more table space and fewer power tools, so the map moved to Memorial Union. We worked on it for months in the Hoofer boathouse, just down the hallway from its final home in the Chart Room. After the material was cut, I painted each layer. To achieve a blue gradient, I started with a base coat of paint in shades of grey, from white at the shallowest to nearly black at the deepest layer. I added a medium called absorbent ground to create a dry, chalky surface for the blue ink that I brushed on next.

Test painting on scrap material
I painted a base coat on each layer in shades of grey
I wiped on absorbent ground to give the colored ink something to stick to
Painting in the Hoofer boathouse in Memorial Union
Painting in the Hoofer boathouse, where I could spread out all pieces side-by-side
Painting on a dye-based indigo ink to give the map its blue color. Every layer is painted in the same ink- the base coat of grey paint gives each layer its shade
Painting on a dye-based indigo ink to give the map its blue color. Every layer is painted in the same ink- the base coat of grey paint gives each layer its shade

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Finishing      (February – March 2014)

Finding a suitable clear-coat for this project was one of the greatest challenges. The finish had to hold up to touching and magnet movement, yet be thin enough not to impede magnetic attraction. I first tried an artists’ spray varnish, but soon found that it would stick to a magnet and crack away from the surface, removing the paint below. After several more hours of research, I chose to use a clear enamel top coat. The look of the enamel finish is great for this piece. It gives the lake area a candy-apple shine and retains some of the texture of the brush-strokes, adding visual interest.

Our improvised spray booth, or dust-free tent, which included a filtered air intake
the air intake setup: a fan enclosed in a plastic bin with an air filter in the lid. The fan blows filtered air into the dust-free tent.
The outcome of leaving a magnet on the spray varnish surface for a few days... varnish sticks to the magnet, then cracks off the paint beneath
glossy sheen after finishing the layers with clear enamel

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Assembling the Lake     (April 2014) 

The base of the entire assembly is one large piece of half-inch-thick plywood, which we called the backboard. The backboard extends 3/4 in. past the edge of the Chemetal material on all sides. The lowest layers were inset into the wooden backboard; subsequent layers were stacked and secured down to the backboard using woodscrews. We had to grind off the pointed ends of screws where they protruded from the back of the piece.

All lake map pieces: large wooden backboard with deepest and shallowest lake layers on the right, shore pieces on the floor above, and intermediate lake layers on the left
the lowest lake layers are inset into the wooden backboard
attaching the deepest layers to the wooden backboard
stacking up the lake layers
it's finally coming together!
All lake layers are attached!
All lake layers attached, screws still visible where the shore pieces will be glued on top
screws protrude from the back of the piece
screws protrude from the back of the piece
grinding off the ends of screws where they extend out of the back of the map.

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Wooden Frame    (April – May 2014) 

Finally, we built up a wooden frame to enclose the piece, hiding the scrap material supports, screws, and dripping glue. We cut the wooden pieces on the CNC router, shaping them to fit the edge of the map, which wraps around the shape of the lake.

The Sector 67 CNC router cuts out pieces of wood to create the map's wooden frame
wood pieces are shaped to create a frame that wraps around the shape of the lake
stacking up the wooden frame in layers
clamps hold the wooden frame as it is being assembled
clamps hold the wooden frame as it is being assembled
sanding the wooden frame down to a smooth finish
After sanding the frame... a sawdust -coated map

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Installation     (May 2014) 

The map was mounted onto the wall using Monarch Metal’s Z-Clip hanging system. I estimate that the map weighs about 80 pounds.

The hanging system: aluminum clips on the back of the map fit into the long rails as shown here, which will be attached to the wall.
Clips on the back of the map
Dimensions for installation
Finally installed in the Chart Room in Memorial Union!

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The Complete Map  (May 2014) 

Finally, the complete map is on the wall!

After a late night finishing the wood frame, I declared it done on May 7th
The map is finished!
Awaiting installation
Moments after the map was installed on the wall
The north wall of the Chart Room is now its permanent home... just 100 yards or so from Lake Mendota itself
Here's an example of the lake with labels added... all labels are magnets.

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The magnetic text labels were designed by fellow cartographer and Hoofer member Eric Oberhart. I added some Scuba dive flag magnets, and I hope to continue to create more… Maybe a 3-d printed capitol building? Maybe the street network? Other Hoofer members can also design magnets customize the map display.

text labels were created with Baltic Birch wood on the Sector 67 laser cutter
Map with labels in place

Video of magnetic labels in action:


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Dedication Plaque / Cabinet 

The dedication plaque was installed next to the map on Aug 22, 2014. It doubles as a cabinet to store the map’s magnetic labels. I built the cabinet in about two days at Sector67, using a router, belt sander, laser cutter and mill. 

11 thoughts on “Mendota Map: the Making of a 3-D, Magnetic Map

  1. Must have taken a while to build the lake map, but the final result is pretty cool. I like the different shades of blue as the lake gets deeper – a nice 3D topographical (or is it called “bathymetrical”?) effect.

    Nice work!

  2. It’s great that you were able to hire some space in a workshop to access industrial standard tools making the project possible. Here in England we don’t have that facility, were far too entrenched in health and safety laws!
    I was fascinated by the laser cutter from your video link and how it cut the contours in the correct direction. Is it programmed to follow a drawn line? I’d love to know how this was done.
    80 pounds in weight! Did you anticipate it to weigh that much?

    1. There are several hackerspaces in the UK: – You should check some out! Some have laser cutters, and maybe somebody has a CNC wood router like the one I used to cut out my map’s wood and magnetic material.
      The CNC router in the video is indeed programmed to follow lines in a digital file. I converted a digital model of the lake bed into contour lines, then the contour lines into gcode, or tool-paths for the CNC wood router. (More specifically, the programs I used were ArcMap, Adobe Illustrator, and CamBam. The data was converted through many formats: from .tiff to .shp to .ai to .dxf to .cb to .nc)

  3. It was a really nice job. I made some project in my last semester but I used normal wood router. I was a very heard work. But in future I would like to use CNC wood router.
    Would you please tell me which brand or model of router you have used for your project?

    1. The router belongs to my local hackerspace, Sector67 ( As far as I know, the router was built by other members there. It’s a 4′ x 8′ x 5.5″ CNC Panel Router with LinuxCNC stepper controls.

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