Introduction: PULSE - Social Seating Structure - Market Street Prototyping Festival 2016
Amidst the vast sea of stimuli that surrounds us, Pulse sets a stage for spontaneous social interaction. Each new encounter provides us the opportunity to interpret the world through fresh perspectives, and gain newfound personal clarity. Inspired by the curves of the human body and the steady flow of the city, the close proximity of each seat erodes at personal spheres - welcoming a new, more socially connected outlook; Pulse aims to reunite community.
This project was designed using Rhinoceros 5.0, with plug-ins T-Splines by Autodesk and Grasshopper 3D
Shopbot Alpha CNC - router
1/2" x 2" HSS drill bit
Festool 6" orbital sander + vacuum
Rasps and Surform for Shaping
25 4' x 8' x 1" sheets Extruded Polystyrene Styrofoam (XPS)
3 4' x 8' x 1/8" sheets Plywood
8 1" wood dowels
3 gallons of Titebond II wood glue
12 gallons West System Epoxy kit
25 yards of fiberglass
Aerosil Gelcoat (large sack)
Alexseal Premium Topcoat
3/8" die-cut Neoprene rubber
Step 1: Modeling and Slicing
The seats follow the curves of the human body and accommodate a large range of body types and sizes. The four spots are offset and placed at different heights to give the illusion of totally separate spaces, however by closely unifying them strangers voluntarily enter one another's personal space. Each spot's comfort puts users in an open and vulnerable position; prime for a deep and meaningful conversation. The lounge seats are distanced at the optimal range for gazing and fully seeing their counterpart.
I sliced the 3D model at one inch increments including 1" holes for dowels for alignment. I also included 1/8" plywood panels on all flat surfaces (sides and bottoms) and two more in the middle for reinforcement. In the future I might recommend going to a 1/4" thickness on these components. I wanted to keep the weight down so I went with a thinner plywood, and hollowed out the two middle plywood pieces. The final weight was roughly 300 lb.
Step 2: CNC-routing
I bought my materials from Home Depot. 25 4'x8' sheets of Extruded Polystyrene Styrofoam (XPS) at 1" thickness. This is very different from Expanded Polystyrene Styrofoam (EPS) which is the white typical styrofoam that crumbles into tiny little balls of foam. XPS is a much smoother, more uniform consistency, which is great for CNC routing (cuts like butter!). It is sold as insulation sheathing at Home Depot, and is only available at this size at the Home Depot PRO stores. I also got three standard 1/8" Plywood 4'x8' sheet from Home Depot, but I might recommend either a higher quality or a different location, as the one I received was quite warped, which made CNC-routing a bit challenging. It took me 3 full days of CNC routing at the TechShop to get all the pieces cut, 46 pieces total 28 sheets of material.
Step 3: Gluing
I used Home Depot's Titebond II wood glue (about two and a half gallons) to laminate the sheets of foam together. I arranged them in order and with the help of a friend glued each sheet through the wood dowels. The first plywood panel had the holes indented rather than punched all the way through to hold in the wood dowels. We started out with only four dowels so we could each have one hand apply pressure around each dowel. We laid down the glue, spread it out with some plastic putty knives, carefully aligned the holes and gently pressed down each sheet. This took us one full day of work.
We laid the glue over the whole surface of each sheet, but I had some leaks throughout the process and realized some of the glue that was deep in the center was unable to dry because it didn't have any air access. In the future I would only apply glue to the perimeter of each sheet to avoid this issue.
Step 4: Sanding, Sculpting, and Building a Booth
Once all the pieces are glued the shaping process begins. It took about 20 hours to fully sand down the foam to my liking. It is key to remember that this is simply the base layer and the build-up of layers can resolve any imperfections and create more voluptuous, smooth curves.
After the foam is shaped and any dried glue is removed it is time to seal and putty the surface. Sealing is done by brushing on a modest layer of Epoxy on all surfaces. Next, once the Epoxy is relatively hardened the putty can be applied. The putty is created by mixing filler into the Epoxy until a thick, peanut-butter-like paste is achieved. This is smoothed on with a putty knife to fill any holes, blemishes, or create a smoother surface. If over 12 hours have passed between layers the Epoxy must be washed or "scratched" (by lightly sanding with a coarse sandpaper) to remove any excess catalyst which rises to the top and prevents optimal bonding between layers. If less than 12 hours have passed this step can be eliminated. This step is necessary between every layer from here on out.
The idea behind the booth is to have a fully sealed environment with clean air flowing in and filtered air flowing out. We used recycled 2x4's to build a simple frame structure and sealed it with a 3.5 mil plastic liner from Home Depot. We stapled it down with a thin strip of wood and a staple gun. The staple should first go through the wood and then the plastic and finally the 2x4; this creates a clamp between the wood and minimizes the chance of the staples stripping the plastic. We used two fans of the same size, one facing inwards and the other facing out, with a a filter in the same dimensions. We used the highest grade of filter from Home Depot to get the most efficiency and eliminated toxins from entering the space. (note: the door to the booth was not yet fully adhered in these photos)
Step 5: Applying Epoxy and Putty
The next step involves sealing the foam and further smoothing the surface to eliminate any imperfections. I bought all my epoxy, fiberglass and tools needed for this and the following few processes from Svendsen's Boatyard in Alameda. I tried out two different types of Epoxy: Hawk Epoxy and West System. I liked West System better because it was a finer consistency, easier to work with, and resulted in a smoother surface.
I started out with the Slow curing formula which allows for 20-25 min pot life (before it begins to heat up) and 90-110 min working time (before it begins to gel). This is depicted in the last image which was taken from the West System website. It shows the four different hardeners and their respective pot life, working time, and curing time. If you are applying multiple layers it is easier to lie within the curing time, for slow it is 10-15 hours, between each layer. If you go past 12-15 hours you will get uncatalyzed catalyst which rises to the surface and creates a waxy layer that makes it more difficult for the next layer to adhere properly. This can either be rinsed off with soapy water or the whole surface can be lightly "scratched" with a coarse sandpaper to remove this film and allow for the best adhesion of the following surface. After mastering the process with the Slow formula I began using the Fast hardener to speed up my process.
Sealing the surface is relatively simple, you must get paint brushes with natural bristles (plastic ones will melt from the solvents in the epoxy). These are pretty cheap and have a limited lifespan, but to take care of them get a big bucket (from Svendsen's or Tap Plastics - to ensure it is made of a plastic that won't melt from the solvents) and fill it with lacquer thinner and dump the used brushes in here after each use to eliminate any epoxy sticking gunking them up. Once you are ready mix about 20 oz of epoxy (a larger quantity than most batches because this step goes quickly). Make sure to mix for a full minute and get the right ratio. West System and Hawk were both a 5 to 1 ratio of epoxy to catalyst. West System also sells pumps that dispense the exact ratio of 5 to 1 which can simplify the measuring process. If you want to lengthen the pot life of the epoxy it is helpful to get a metal pan with a plastic (make sure it is the right plastic) liner (also sold at Svendsen's) and pour the mixed epoxy into the pan. Spreading it thin will prevent it from prematurely heating up and gelling. Next grab a brush and paint the full surface. It should go on easily, the coat thickness should come naturally, not too thin where you are working hard to spread it, nor too thick where it is dripping. I also sealed all the Plywood pieces which weren't glued down to the foam (the remaining two sides and bottoms).
Once sealed the smoothing begins. The putty is made by fully mixing the epoxy and then adding a filler substance. I bought the West System 407 filler from Svendsen's. This was added slowly while mixing until a consistency of peanut butter is reached. This step takes more time and precision so smaller quantities should be made per batch. I found 5 oz to be just the right amount. This is spread on plastic putty knives and ideally covers the full surface until a smooth, even surface is reached. The plywood end plates were adhered using round gobs of this putty formula and drilled into the hardened sealed surface. The screws work as clamps would, and I also used alternative methods of clamping, to ensure the pieces would lie and cure as flat and air-tight as I could get them. For the bottoms I simply tipped over the piece onto a flat wood panel after adhering and screwing down the plates so it's own weight would secure the plywood. The tops I clamped in as shown in the images using small 2x4 pieces and clamping them within the wood-frame booth structure. After the epoxy had cured I removed the screws so they wouldn't jut out or create imperfections which were hard to sand down.
Step 6: Lay Up Fiberglass
I bought two different grades of fiberglass, one was called e-glass it has a mat texture on one end and a fabric-like cloth on the other, the mat absorbs more resin, and is stronger in shear. I felt this would be helpful to build up the initial layers for thickness and strength. For the second layer I used a 10 oz cloth fiberglass. This is more flexible and absorbs less epoxy. It is helpful to set up a fiberglass station, as seen in the first image. I set it up using a metal tube clamped to two saw-horses. I put the fiberglass tube on this with a table underneath. I spread out a roll of paper on the table which I replaced periodically so as I was measuring the pieces I could keep the fiberglass untainted. If any epoxy touches the cloth it will harden and both create imperfections and prevent this segment from bonding to the previous layer.
The cloth should be measured and cut to fit the exact form while the piece is still dry so you can trim off excess without getting your tools and cloth all sticky. It is helpful to label each piece of cloth and where it should go with a sharpie and keep this stack in a clean area. As soon as epoxy touches the cloth it will begin to harden and if it isn't placed where you want it will go to waste. Any excess cloth that isn't cut to form will also harden and can be difficult to sand off, which is why it is good to plan everything out before beginning the epoxy process. Doubly curved surfaces will be difficult to form with one piece of cloth, so I created a puzzle of cloth pieces that form the full surface. Each piece of cloth should overlap with the one below it at least one inch to ensure adhesion. The corners are done last by cutting thin strips to accommodate for the curves (or thicker on straight edges) and overlapping each piece as you lay them down.
Once all the pieces are cut you must prep the surface (if over 12 hours have passed since the last coat of epoxy), then lightly paint on a coat of epoxy to wet the surface. Then carefully press the piece onto the surface and pat it down. Air bubbles will create deficiencies in the surface and adhesion so make sure to remove any air bubbles and press down the fabric from the center out to the edges. Then use epoxy rollers (sold at Svendsen's or Tap Plastics) to apply epoxy to the cloth until it is fully translucent. If you see any remaining white spots it is either not fully wetted with epoxy or there is a problem underneath (usually an air bubble).
Once cured you can sand between layers to ensure the smoothest form possible. It is most important to get any sharp edges off and remove any air bubbles or noticeable blemishes. The first layers are more about building up the surface to a certain thickness, I was shooting for 1/8", and for a specific strength. I was aided by the fact that my mold was to remain within the piece, but I was able to reach 3 layers (considering the e-glass is two layers in one) which is strong enough to hold the weight of about 4-8 people (if not more).
Step 7: Apply Gelcoat
The gelcoat is the last opportunity to smooth out and reach the form you are looking for. Due to my limited tools I applied the gel coat manually (rather than sprayed on). I mixed the epoxy with a substance called Aerosil until reaching a thick paste-y substance and spread this on with plastic putty knives. I coated the full surface about two or three times until I felt confident with the smoothness and form. In between each layer I carefully inspected the surface and marked it up with a sharpie to show where I saw low points and high points. Once the surface is wet and glossy it is harder to see these spots so the sharpie helps to speed up the process and ensure a higher precision. I used a finer sandpaper (100 and 120, rather than 60 and 80 as I was using previously) because the gelcoat is much softer than the fiberglass and I am not trying to remove material as much as I am simply trying to level and shape the surface.
Step 8: Finish
The finish was done professionally at Svendson's Boatyard in Alameda, California. I used Alexseal premium topcoats. I asked them to also smooth out the surface a bit further than I had because I knew their tools and staff were far higher quality and more professional than myself and my resources. They used four coats of heavy build primer with heavy duty orbital sanders to reach this ultimate smoothness. It takes 3 days for each coat of the final paint to reach its full hardness so it is important to account for this time. I didn't have time for a final clear coat which might have helped to protect the paint even more from scuffing and sharp objects scraping it. I feel it has endured a lot (I've brought it to five different events, each spanning anywhere from 1-3 days), and it is still in great shape. The gloss and vibrance of the color still remain a very professional quality, however it does show some wear and tear from buttons on pants and the many moves it's gone through.
I also included 3/8" neoprene footings to both raise the finished piece off the ground and prevent it from sliding around on the ground. I ordered these from Cal Neva Supply in San Leonardo, CA. They do custom die-cut shapes at a very reasonable cost. I was able to send the form of my footings in the form of an AutoCAD DWG file and pick them up the very next day! I used rubber cement which I purchased from Cal Neva to adhere the footings to the form.
The piece was a great success on Market Street and truly did foster interactions between strangers!