This Instructable will describe the construction of a heavy duty milk jug raft built out of recycled materials and capable of supporting over 700 lbs. The product is a fun craft for lakes, rivers, and swimming pools alike.
I've actually entertained the idea of building a milk jug raft for a while, but it took a few years to gather all the milk jugs, so I've only now been able to complete the project. I found it to be highly rewarding and extremely satisfying... there is something innately fun about building a raft and having adventures like those found in the wonderful story of The Adventures of Huckleberry Finn. As Huck says, "It's lovely to live on a raft. We had the sky up there, all speckled with stars, and we used to lay on our backs and look up at them, and discuss about whether they was made or only just happened." I personally don't live on my raft, but I had an incredibly peaceful and relaxing experience lying in the middle of a lake gazing up at the sky. The raft is 100% worth the minimal effort needed to construct it.
This project carries no cost and can be easily completed by anyone who can use a drill and basic hand tools. It will take a few months to a few years to save the required milk jugs, but a speedier option would be to gather them from recycling days and friends. Alright - enough with the talk, let's get shipbuilding!
Step 1: Collect the Milk Jugs
The first step is to evaluate the best option for flotation and collect the floats. Although this is a milk jug raft, yours doesn't have to be - I just used milk jugs because my family goes through about 6 gallons per week, so they were plentiful. Alternately, you could use two-liter carbonated drink bottles, or any other strong plastic container. You will need a lot, so keep that in mind when choosing your flotation method.
Next, you will need to determine how many to collect. This is based on desired buoyancy and on whatever size goal you set. If you want a certain size raft, just measure a milk jug and use the basic length times width calculations to figure out how many you need for a certain size raft. This works well, but a better method is to set a goal for milk jug collection based on how much buoyancy you want in the end. There are some really neat physics calculations that govern buoyancy and displacement (how much water your craft pushes out of the way), and they are super simple! Just take the volume of your container (1 gal=3.785 liters) and convert it to liters. This will not work with imperial units, which is why the United States should switch to metric. :) After converting your volume to liters, simply replace the word "liters" with "kilograms." That's it! That is how much weight one milk jug will support - 3.785 kilograms, or 8.345 lbs. With that knowledge in hand, you can just divide your target buoyancy capability by that to find out how many milk jugs you will need.
To estimate a target buoyancy, I recommend about 50 lbs for the raft itself, your weight and an estimate of any potential guests' weights, and 20 lbs for miscellaneous. However, that will just barely keep your toes above the water. Really, you should use about 1.5 to 2 times that weight - this will keep you dry and provide a safety cushion of buoyancy. I decided to use 84 milk jugs.
Once you know how much bouyancy you want or how large a raft you want, start collecting! Use whatever resources you have - recycling bins, family, friends, work/school, etc. The more places you have giving you milk jugs the faster you can get building!
Step 2: Bind the Milk Jug Modules
Once you have a huge pile of milk jugs sitting around somewhere in your house and taking up a lot of space, you will be very motivated to use them for something. That is great!
I built my raft by making four-jug modules that were taped together. These were easier to handle than single milk jugs and were also symmetrical, which made attachment fairly straightforward. To make the modules, assemble scrap wood into a square with inner dimensions of 12", or whatever two of your milk jugs measure side by side. Next, place four jugs in the jig with their handles facing inwards. Use a rubber band to hold the tops close to each other.
To finish the module, measure four feet of duct tape and cut it a little bit long. Pulling tightly, wrap it around the four milk jugs about halfway up. Make sure to smooth it down well. After removing the rubber band, you have a finished milk jug module! Congratulations! You only have a gazillion more to do...
Step 3: Lay Out the Raft
Next, you should determine a rough layout for your raft. Decide on the basic shape, etc. I decided to go with the simple solution and just make three pontoons side by side, but this design leaves a lot of room for improvement. For example, it is a bit wobbly side to side. One possible fix would be to place the outer pontoons on outrigger-type structures, so that the three pontoons would have space in between them. The deck boards would then cross all three pontoons, just like they do in my raft design.
You could also choose a different design and make a square raft, or a taller raft, or even a monstrous floating island.
Whichever design you settle upon, decide how long your boards will have to be to connect all your milk jugs together. I made mine around 14 feet long - this enables me to make three pontoons with 7 modules each for a total of 84 milk jugs, 28 on each pontoon. Measure and cut your boards (I used scrap 2x4s), then proceed to the next step.
Step 4: Make the Pontoons
I'll be honest - this is the most boring step part the whole project. It goes much faster with a good set of tunes playing in the background, though.
With your mountain of milk jug modules ready, you can make the pontoons. I used nylon string tied through the inward-facing handles of the four milk jugs in each module to attach them to my 2x4 pontoon boards.
It is somewhat tricky to get the milk jugs to stay, and even harder to make the nylon string not slip, so don't give up if it takes a few tries to get it right. I passed the string (with fused ends) through two of the milk jug handles (going from one side of the board to the other), then up, over the board, and back to the side it started on. I then threaded it down and through the other two handles (again going from one side of the board to the other, not parallel to the board), then back up and over the board to meet the other end of the string. Hopefully the pictures help. :)
Then, I tied the string on top of the board (in the middle of the X formed) using a triple knot. From Wikipedia, this seems to be a granny knot with another knot on top. Make sure to pull the string as tight as possible before doing this! Nylon string is extremely slippery and WILL undo itself if not triple-knotted. Once the knot is done, fuse the ends of the string with a lighter.
If you've got one module attached, you are totally capable of doing all the rest! Just keep the tunes rolling and don't forget to pull the string tight. Also, make sure to push each module up against the already-attached ones so that you don't run out of space on your pontoon board. Your finished pontoon should look approximately like the one in the last picture.
Step 5: Add Planks
Once you have all your pontoons made, line them up according to your design and measure the distances you will need to cover with planks. For me, since my raft was a rectangle, it was prettty easy - just a bunch of 32" 2x4s. You should plan to have one plank per row of milk jugs - i.e. I used 14 planks since I had a 6x14 array of milk jugs. The planks serve a triple purpose - they provide a walking/sitting surface, hold the pontoons together, and press down on the milk jug caps (which are slightly above the surface of the pontoon boards) to exert tension on the string and keep the milk jugs from flopping around. When you have determined the number and length of planks needed, cut them. You don't have to use 2x4s - you could use thinner boards for less weight.
Assemble your pontoons in the correct formation and then use one screw per pontoon to attach the just the end planks. Now you can make sure that the raft is square. Once it's square, add another screw to each of the pontoon-plank intersections. I also added two planks evenly spaced in between the end ones, with two screws per interesction.
If you continued like this, you would spend a long time screwing down planks, which would grow quite loathesome by the time you were done. So, to speed up the process and save on screws, I only used three screws per plank for the rest of the planks, rather than six. The raft is still quite sturdy. (Two-by-fours may have been a bit excessive for planks, hmm?)
Step 6: Sand and Paint
If you used scrap wood like me, it is probably really rough and not pleasant to sit on. So, to remedy that problem, pull out your dusk mask and sand it for all you're worth!
An orbital sander will make your job much easier, but sandpaper will also work. I started with 80 grit and then went up to a 120 grit for a smoother finish. The difference was quite apparent, and I felt much more confident about sitting on it and not getting splinters.
Once the raft is sanded to your liking, paint it with a durable exterior paint. It will get wet and see some roughing up under your shoes, so interior paint probably won't make the cut.
Step 7: Make the Paddle
Since I didn't have a canoe or kayak paddle, or even a rowboat oar, I had to get creative and use what I had on hand. I used an old squeeze mop and a cabinet door to make a really nice paddle.
To do this, I removed the mop part of the mop and was left with the handle and the bracket at the bottom of the handle. I had a space left between the sides of the bracket, so I made some washers (using a hole saw) from a piece of plastic I had lying around. The plastic was made by cutting up milk jugs and then melting and pressing them into a sheet of hard, rigid plastic useful for many projects. There is a pretty good Instructable on that subject here. It says to use a pot of oil to melt the plastic; I just used a parchment paper-covered cookie sheet in my oven.
I did 45° cuts on the corners of the cabinet door to improve its aesthetics and then used the plastic washers and the bracket to attach the door securely to the mop handle. Finally, I gave it a quick coat of polyeurethane for waterproofing.
If you have a paddle, oar, or other means of propulsion (battery powered outboard motor, anyone?), by all means, use it. Otherwise, find a handle and something flat, and let your creative side shine!
Step 8: Add Pizzazz!
A white raft floating on white milk jugs would probably be described by Huckleberry Finn as "mournfully dull," so in the spirit of adventure, pirates, and boyhood fancy, let's add some pizzazz with a pirate flag!
To make your flag (it doesn't have to be a Jolly Rodger), take a scrap of cloth or a pair of unwanted pants and cut it to size. I used about 16"x12". Next, if it is to be the dreadful skull and crossbones, crumple one end of it and cut it with scissors to make a tattered edge for effect. If it is synthetic, lightly fuse the edges with a lighter to prevent unravelling.
Lay out your design by drawing the outline of what you want in chalk, or with a pencil. Fill it in with paint - I just used the same paint as I put on the raft planks. Once one side dries, flip it over and do the same thing on the other side.
I found that a gardening stake worked well as my flagpole. If you don't have one, just buy a dowel rod. To secure the flag to the pole, fold one end over the pole so it wraps around, then pin and sew it. The finished stitch can be seen in picture 7.
Next, drill a hole in one of your raft planks or pontoon boards to fit the pole. Hot glue a stop (I cut mine with a hole saw) onto the pole at the correct depth to prevent the flag from sinking too far into the hole.
Finally, give your new raft a good name! I christened mine The Thirsty Pirate, which I think is quite fitting.
Step 9: Set Sail for the High Seas!
Step back and take in your handiwork! You have just built a sturdy watercraft, capable of supporting lots of people! Find some water and set sail for magical adventures on the high seas!
Hmm... actually sailing this craft into the ocean may be hazardous to your health and is thus not recommended. Nevertheless, fantastic adventures await you and your newly christened pirate raft! Have fun, be safe, and unleash the Huckleberry Finn (or Tom Sawyer, if you like) inside you!