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

Picture of Project RRaft - Building a Raft Out of Water Bottles

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?

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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.


michellenergy (author)2011-03-29

I am currently making a raft based (mostly) on your design with my two kids and we are having a blast with it! Great instructable and great idea!! We are using empty gallon milk jugs because that is what we have in abundance!! lol ... We are finishing up the fourth pontoon now and will probably do sea-trials this week! I'll post again when we see how she fares! THANKS! for a great instructable posting!

JoelL104 (author)michellenergy2017-07-14

How did it go?

I think gallon-size milk cartons ARE NOT a very good idea! The caps are not secure and the plastic is flimsy. (They barely keep milk in; so don't expect them to keep water out.)

subjected to the bottom of a raft, they will likely lose their caps and
implode... and you will instantly lose all 8 pounds of flotation, which
will put more pressure on the remaining cartons... causing them to fail

I understand the appeal of using larger bottles because you will need fewer of them, but they are more dangerous if
they fail, and they are also much flimsier. Fill a 2-liter bottle with
air and see how easy it is to poke the side in. Do the same to compare
against a 20-ounce bottle. (The good news about a 2-liter bottle is that
the cap is very strong, so they might actually make a good raft.)

dforcier (author)2017-01-05

how many bottles would you need for lets say a 96 lb person

GracieP4 (author)2016-05-03

how did you keep the bottles together so they would hold the weight?

dforcier (author)GracieP42017-01-04

he did it with Garden mesh and zip ties but he said a fishing net would work

shorty_my_it_gurl (author)2011-11-04

hey say me and my friend way 190 pounds together, but we want to use 2L bottles instead .5l .How many 2L bottles would we need to hold are weight and are bout will be around 20-100 pounds?

2L bottles will support about 4lbs each. You want to go over as much as possible so you actually float, instead of simply not sinking.

baboy is hot (author)2011-01-12

what are other alternative for material? we are going to use it for our investigatory project.:)
and also can we use it in flash floods??thanks!:))

mcaliber.50 (author)baboy is hot2011-07-13

using it in flash floods actually sounds like a goog idea

temp (author)2009-04-22

Exactly how cold was it. Cause it looks like there are many green trees, your pool is still open, and there is no ice / snow. Therefore it is not fall winter or very early spring. In late spring and summer the water is never cold!

Weissensteinburg (author)temp2009-04-22

It's Florida...the leaves don't fall and the water doesn't freeze. That doesn't mean anything less than a polar bear could bare that water.

(get it, bear-bare? hehe)

hey i liv in florida too! how old r u?

LOL!!! look at my pic click it you cant see it well !

temp (author)Weissensteinburg2010-10-10

Haha. I will admit, that made me laugh.

temp (author)Weissensteinburg2009-04-26

if leaves are still on the trees the water's warm enough to go swimming. And if you're in florida you shouldn't even complain about cold water. I was swimming in te ocean today. I live just north of boston. That was cold.

enemigo (author)2010-10-31

when you´re counting bottles don´t forget to take into account the weight of the deck material.

stronglad (author)2010-08-22

Can I do this with Arizona tea jugs?

Sure, you'll just have to do the buoyancy conversions yourself.

madara009 (author)2010-05-23

do you know how much weight a 2 liter soda bottle would hold up? i want to make somthing like this and it might be faster to get soda bottles instead of water.

RHkramer is correct, by the math stated. 1 kilo weighs nearly 2 pounds. Therefore, if you weighed 100 pounds, you would need 50 bottles.

You'll need more than that. There's the weight of the bottles themselves and the raft. In addition, that figure will only neutralize your weight -- You would be weightless in th water, but far from securely above water. You need extra bottles to actually feel like you're on a raft. Also, a two liter bottle will support two kilos, so 100 pounds would be 25 bottles for a neutral weight.

rhkramer (author)madara0092010-07-26

My guesstimate, without doing any real calculations, is about 4 lbs. per bottle. An empty bottle will hold up about the same weight as the weight of the amount of water it will hold, plus or minus a little bit, depending on how heavy the material of the bottle is (minus for materials heavier than water, like glass, plus for materials lighter than water--I'm guessing a lot of plastics are lighter than water, but I don't know for sure (fill a bottle, leave the lid off, and submerge it, see if it floats or sinks).

Also, if the bottle collapses slightly in water due to the weight of the water pressing against the outside, there will be a little less volume and thus it will support a little less weight.

A liter is a little bigger than a quart, a gallon of water weighs about 8 lbs, so a quart weighs about 2 lbs, so guesstimating that 2 liters will support about 4 lbs won't be too far off.

You could also simply fill the 2 liter container with water and weigh it--like I said, it will support about the weight of water it contains. (If you want to be precise, you could subtract the weight of the air the bottle will hold when we call it empty, but that is negligible. You will have to account for the slight collapse of the bottle underwater (as mentioned above), so if you weigh the bottle full, figure it will support a little less than what you weigh.

Of course, you'd want to figure on using more bottles than this caculation indicates, to account for all kinds of things, including the potential of bottles springing leaks due to collisions, abrasion, or whatever.

Hope this helps!

madara009 (author)rhkramer2010-07-26

WOW! Thank you! this is really helpful! i think ill start building one next week lol

rhkramer (author)madara0092010-07-27

You're welcome!

The Landon (author)2010-01-14

You can get a lot of bottles at small businesses that you´re familiar with, like restaurants. Once I went to a small casino to get bottles (not familiar with) and got like four BIG and FULL black bags of 2l bottles.

dzent1 (author)2010-01-14

Dang, that looks fun! And you're right, the CEO at Home Depot is a genuine a-hole and it just kind of trickles down from there. I quit them a few years ago and won't EVER be back because they're run so poorly. Loews all the way, or the local hardware store where the old guys know everything there is to know about everything!

bassclarinet23 (author)2010-01-10

How many bottles would you guess be needed to support around 120lbs.?

 121, plus the weight of the raft. But thats to be neutral, you need extra buoyancy.

Cool. Thanks.

MrL33TPenguin (author)2009-11-04

Hey Weissensteinburg, thanks for replying to several of my comments from a while ago. Because of that, I started to collect some water bottles, now I think I have enough to hold me above the water. I'm gonna be building a kayak for this one race that is going to be held this Sunday. Hope I can build it before Saturday and test it before the race. Thanks for all help from before.

Rock Soldier (author)2009-08-18

So, if I wanted to build a raft to support (for example) thirty pounds, I'd need at least 30 5 Litter water bottles?

No way! You'd need about thirty .5 liter bottles. The average plastic water bottle is .5 liters. If you want the exact amount, it's easier to work in kilograms. One liter of air will support one kilogram of weight in water.

30 lbs = 13.6 Kg

So to support 13.6 Kg, you'd need 13.6 Liters of air. That's 27.2 average water bottles. Remember you also have to account for the weight of the plastic and that the 27.2 number is only to equalize the weight. You'll want to use extra if you really want it to act like a boat.

Sorry, I meant .5L. Now, I have a question. How many Kilograms equals a pound?

About 2.2 lbs equal one kilo

koolmuffin13 (author)2009-05-05

the picture blocks the third step D:

loppy96 (author)koolmuffin132009-06-29

whenever it does that just refresh the page

What do you mean?

Derin (author)2009-05-31

You also need one of these if you need a PFD :)

ednolan (author)2009-05-25

I made one over the course of a few weeks. It works fine, and I didn't have to use the pipe frame or even paint the raft. I was able to get the bottles a lot faster by picking them out of the school's bottle recycling bins, which are usually full. Great idea!

Weissensteinburg (author)ednolan2009-05-25

That's great. I used the recycling bins at my school, until they got rid of them. Could you post a picture of yours?

ednolan (author)Weissensteinburg2009-05-25

Keep in mind that that photo is of the first test. I think I will eventually paint it, and I didn't really have an oar, so I was using a piece of driftwood and I had someone on shore with a rope to pull me in. (you can also see the picture at

Weissensteinburg (author)ednolan2009-05-25

Looks like yours turned out really well. It's great to know someone was actually able to use this.

smessud (author)2009-05-19

Just to add more data on buoyancy .. 1 litre of pure water weighs 1 kilo but 1 litre of salt water weighs more. Your 2-liter bottle would float 2 kilos in a river, but it will float slightly more in the sea.

ReCreate (author)2009-04-23

Could i use those 5 Gallon Bottles that are used for water Like the ones in the Picture,I ended up with about 20 of them.

Berkin (author)ReCreate2009-05-14


ReCreate (author)Berkin2009-05-14


jeff-o (author)2009-01-28

It doesn't look too cold where you are... Shorts and a T-shirt! *envy*

Weissensteinburg (author)jeff-o2009-01-28

No, the air temp wasn't too bad (florida) but the water is ridiculous!

For the record, it was 22 degrees a couple nights before.

Over here in Canada, it's -43... AIR TEMPERATURE. The water's frozen by the way... AND NOT ALL OF CANADA IS LIKE THIS(for thick-headed people) I LIVE UP NORTH>>>

About This Instructable




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