Introduction: Project RRaft - Building a Raft Out of Water Bottles

About: I enjoy photography, horticulture and carpentry, and am almost always doing something relating to of those things.

rRaft is short for recycled raft. Inspired by Reishee Sowa, who lives on a water bottle island in mexico, this is my attempt at a similar feat. While many people have duct taped a couple hundred bottles together in the past and called it a raft, mine is sturdier, has a real deck, and is indefinitely reusable.

The entire process of developing Project rRaft was documented at

WARNING: General safety rules, as well as some state laws, dictate that you should have at least one PFD for each passenger of a boat. In the pictures, we are not wearing any, but also realize we did not row very far off shore. Go boating at your own risk. Also, be careful with any tools and such that you use.

Step 1: How Many Bottles?

For ease, I will split this step in to two sections. The first will explain the math/science that went into picking a bottle goal, and the second will quickly tell you how to figure out how many bottles to collect.

Section 1

I wanted my raft to support myself, and a friend if the opportunity arises. I weight 170 lbs, and i'm factoring for a friend who weighs the same. That's 340 pounds. Add in the weight of the boat plus extra buoyancy to keep us above water, and we're at 400-500 pounds of needed buoyancy.

  • The average water bottle contains .5 Liters of water.

Archimedes' principle, or the law of upthrust says:

"A body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid."

Thanks to scientific measurements, one liter of water supports one kilogram of weight.

If each water bottles supports half a kilogram, which is about one pound, than you need just as many bottles as pounds you wish to support. I used exactly 450 bottles in my raft.

Section 2

First, decide how many pounds of cargo your raft should support, that number is roughly how many .5 L bottles you will need.

Easy as that!

Step 2: Gathering Bottles

The most important part of getting enough bottles for your raft is to tell people that you're doing it. Once you convince them to save all their bottles, collecting is a breeze. Here are a few suggestions for collecting bottles:

  • Carry a bag with you everywhere for collecting bottles - I would get 20-25 bottles a day this way
  • Dumpster dive on recycling day
  • If you or friends play sports, put a collection box where you practice
  • Put a collection box in teacher work-rooms (if you're in school) or break-rooms (if you have a job)
  • Get friends to collect at their houses, too -- One friend of mine brought me a garbage bag full every week or so

Step 3: Bottle Processing

Bottles aren't quite fit for sailing as soon as you get them: we don't want the labels peeling off in the water and polluting them, nor do we want the bit of water still in the bottles weighting us down. Time to settle down for a bagging day!

First, all the bottles are dumped onto the floor, and I sit down and cut off each and every label. This needs to be done so that they don't come off in the water...pollution is bad. Once the label is off, each bottle's contents is emptied into a Gatorade bottle (One is picked out from the pile) because most water bottles still have a bit of water left in them, and every bit of buoyancy counts! Gatorade is the bottle of choice because they have large mouths, making them easy targets (and spill resistant) along with higher volume capacities than most water bottles. Bottles from juice, soda, or sports drinks need to be rinsed out, so they are separated as they go through initial processing.

After the entire cache of labeled bottles is exhausted, the non-water bottles are taken to the bathroom and washed out. If any water bottles were partially full, that water is used before sink water. The bottles are then taken back to be assimilated into the general bottle population.

Now it's time for the counting! Kitchen garbage bags are retrieved, and 50 bottles are deposited into each one. Full bags are thrown into the vacant tree house out back, and the surplus bottles (< 50) are left in a laundry hamper, eagerly awaiting the next bagging day. Lastly, the final tally of bottles is recorded.

Step 4: The Plan

The rRaft Blog, this Topic and a few friends helped me plan my raft.

The basic concept was to have two pontoons with a platform over top. Fishing nets would have been optimal for holding all the bottles together, but I had no source, so I used garden mesh and zip ties to hold them together. I also ended up making a third pontoon to support the necessary weight.. The frame is made from 1/2" electrical conduit connected with threaded 1/2" PVC corners (they're cheaper) and connected with liquid nails. The platform is painted plywood.

Step 5: Pontoons

Each pontoon was made of 75" of the 40" wide garden mesh. I wanted them to be 6 feet each, so the extra inches would make up for the ends. Lay out the mesh and use zip ties make it a cylinder. I found that the best way to close the cylinder was to flatten the end, with the seam in the middle, and zip tie it like that. Look at the pictures for a better explanation.

Each of the main cylinders was able to hold 162 bottles. Simply fill it with bottles and zip tie it shut.

Rinse and repeat.

My third pontoon was a last minute thing, and since it was going in the middle, I decided to make it pointy, sacrificing some volume, hoping it would look good. In order to get an even 450 bottles, the third pontoon had 126 bottles.

These are pretty simple, but somewhat time consuming.

Step 6: The Frame


2 - 10' length of 1/2" electrical conduit
4 - 1/2" threaded PVC corner
1 - Tube of Liquid Nails
1 - Rubber mallet

Home Depot decided that they wouldn't cut my conduit for me, so I went to Lowes, which happens to be right across the street, less busy, and a whole lot nicer. The guy at Lowes (go to the plumbing department, that's where they'll cut it) cut each piece into 6' and 4' for me. Follow the directions on the liquid nails to assemble a rectangle. The rubber mallet is to make sure the pipe gets into the elbows nice and tight.

Step 7: The Platform

An earlier idea had a piece of canvas stretched across the frame like a trampoline. After spending 2 hours grommeting the canvas, and then another half hour stretching it over the canvas, I waited until the next day to try it out. The conduit was bent and the canvas ripped when I sat down on it. I wanted to do it like that to save on weight, but I'm now glad that I used plywood.

I painted a piece of plywood with some left over paint we had, then sanded and painted again. That's about it for the platform..what can I say? Plywood is simple.

Step 8: Attach It All

I used 8 one hole conduit straps and bolts to attach the frame to the plywood. They give enough leeway for tying stuff too, which is exactly what I needed.

Attaching the pontoons to the frame is a lot more complicated, as they need to be removable. You'll need a decent amount of rope, four hose clamps and four eye bolts to attach the three of them.

First, tie a length of rope around the pontoon about a third of the way in from the front and back of the outer pontoons. To prevent sliding, weave it in and out all the way around. It doesn't have to be every other square, but do it enough to prevent breakage. I tied to ends of the rope together using a Sheet Bend knot. Use these pieces of rope to attach the pontoons to the frame with a hose clamp at each one.

Next, drill and screw in four eye bolts, two on each side of the third pontoon. Use a length of rope through the two loops of rope on the other pontoons. Weave the rope in and out of the middle pontoon, making sure to go through the eye bolt when you reach them. This serves multiple purposes, tying to the outer pontoons keeps them in place. Two attachments points would allow them to flow outwards, putting the platform at water lever. If you tie the rope tight (I used reef knots here) the middle one will stay in place, and the eye bolts will keep it raised.

If you did everything right, the only knots you'll have to undo are reef knots. The loops around the outer pontoons stay in place permanently, while the loops that hold the middle pontoon in place will be removed for transportation. To remove the outer pontoons, just undo the hose clamps.

Step 9: First Test

Now that everything was assembled, I had to test it. We carried the raft to the pool and set it in.


By myself, I could easily stand on it and rock back and forth. It's extremely stable. I grabbed the pool broom to push myself around, it doesn't have much friction, hence the look of concentration on my face in the photo. With two people, it's still stable, but I wasn't about to try standing up.

Step 10: Finishing Touches

For aesthetics and convenience, I added a few more things:

  • PVC bumper on the back, to make getting on from the water more pleasant
  • Painted name plate attached with eye bolts and rope - It would hang in the water
  • Rope loop to assist with getting on from the water
  • Eye hook for docking

The PVC bumper is made of flex PVC - it's made for sprinkler systems. I nailed it to a board and used a combination of a box cutter and Dremel to cut a hole through one of the walls. If you do use a Dremel, be sure to wear eye and respiratory protection. A fan also helps to blow any fumes away.

Once it's split, slide the bumper slowly onto the back of the raft's platform, then screw in on. Mine is about 2.5-3 feet long.

Step 11: Paddles

A quick trip to the cull wood section at Home Depot got me a wooden pole and a piece of plywood to make a paddle from. The wood cost me $1.50. Trace out a paddle shape on the plywood and cut it out with your choice of saws. I used a circular saw. Sand both it and the pole down to be smooth and have rounded edges, screw them together. They don't take long, but are sturdy and effective. Definitely seal them with something. I'm considering attaching a water bottle for buoyancy, in case they fall in the water.

I drilled two 1/2" holes in the paddle so that it can be tied to the boat.

Step 12: Maiden Voyage

Unfortunately, this project came during the coldest time of the year; but just for you guys, I braved the cold waters and took my raft to a nearby lake. Here are the results.

I brought with an electric screw driver with me, and using it, I was able to assemble the entire raft in about five minutes at the lake very easily. I took trips both with someone else, and by myself. I weigh around 170 pounds, and so did one of my passengers. We rode pretty close to the water, but it was definitely still stable and buoyant. As you can see below, it's stable enough for both of us to stand up at the same time. With a (much smaller) girl, we were a few inches above the water, and by myself, it was perfect.

I haven't gotten a chance to use my home made paddles outside of the pool, as they hadn't been sealed by the time we went on the lake.

The rope-loop-step and plastic bumper worked amazingly for getting back onto the raft, and not a moment too quickly - the water was freezing! My lightweight passenger did get slightly wet when I was getting back on, however.

Overall, rRaft was a huge success, and a project that i'll continue to use when the summer comes around. I encourage anyone interested to embark upon a journey such as mine. Enjoy!

The video isn't great, but you can still see that it works.

Keep the Bottle Contest

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Keep the Bottle Contest

Keep the Bottle Contest

Participated in the
Keep the Bottle Contest