Boats hold a special romantic appeal, for kids as well as grown-ups. Add to this a little scientific experiment, and we have a winner – a balloon-powered boat!
In this post, you’ll find a tutorial on how we made one. If you want to get one quickly, you can also get it through our toy shop!
Our family is particularly crazy about ships and boats. Some of us (Jeffrey) can’t say enough about the beauty of their lines. Others (me and Budster) always think of far-away lands and adventures in connection with boats. Even if the only pool of water we have in our immediate surrounding is a puddle in the backyard, a wooden boat can turn it into an ocean with sharks, pirates and all the rest.
Another fascinating thing about boats is that it is a longstanding mode of transportation, so over the course of history people have had time to invent quite a few uses for them and ways to power them. We have already built a paddle boat. When we go on summer picnics, we seldom fail to make a barge out of freshly emptied sardine tins (don’t worry, it isn’t US leaving them behind!). Sailboats are probably my favourites, but we have yet to tackle one them. With so many different variations, boats are sure an interesting way to study the mechanics of movement with kids!
This project isn’t about scaling down any propulsion system actually used in a boat, but rather a fun experiment with a particular mechanical system, in this case using compressed air. If you’re interested in a comparison to a real boat though, the balloon-powered boat is functionally similar to a jet boat that pumps water to accelerate.
And now, if you’re ready to start an adventure in your bathtub, let’s build this boat!
- wood: we used 3/4″ thick maple board and 3/4″ thick roasted maple board cut in half; it you want to skip a few steps of laminating wood and cutting a cabin, you can go for 1 1/2″ thick board (even a softwood 2″x4″ should work)
- 5/8″ dowel
- 1/4″ copper pipe (optional)
- wooden peg (optional
- wood glue
- outdoor varnish
How to Make a Balloon-Powered Boat
1. Our first steps can be considered optional. We laminated the base of the boat from two layers of wood: a 3/4″ thick maple board and 1/2″ roasted maple board become the hull. Glue the pieces of wood together with the wood glue and let them dry while clamped tightly, then trace the hull pattern onto the wood and cut it out with a band saw. (Or a scroll saw or a jig saw.) Sand all of the surfaces smooth – you can give it a bit of boat shape by carving or power sanding, if you want.
2. After tracing out the cabin pattern on a piece of roasted maple, cut it out and sand its edges smooth.Then locate where the cabin should sit on the deck, and glue it on. Laminating the three layers of wood together doesn’t add anything to the functionality of the boat, so if you want to make a simpler design, cut the outline of the base out of 1 1/2″ solid board and go to the next step.
3. The next step is to create a channel for the compressed air to run through. The 5/8″ dowel will need a 1/4″ hole drilled through it, and the boat will need a 5/8″ hole to accept the dowel. The hole should go almost all the way through the boat, but definitely not all the way through! A 1/4″ hole will then need to be drilled from the stern (back) of the boat to meet the 5/8″ hole.
While you have the 1/4″ bit handy, you can drill a hole near the front of the boat for inserting an optional peg in. The peg can be used for tying a string to, for navigating treacherous mud puddles.
If you plan to use a piece of copper tube for the nozzle, cut a length of it now, using a pipe cutter or hack saw. The tube can be polished up nicely with a minimum of effort but clamping it in a drill and sanding it while it spins.
4. Then, glue the parts together. The smoke stack should not bottom out in the hole drilled for it, or it will block the hole that runs to the nozzle. Then the copper tube should be pushed in so that about 1/4″ of it sticks out.
5. Thoroughly seal your finished boat with a varnish rated for regular wetting. Follow the manufacturer’s recommendations – our’s called for 3 layers, with light sanding and long dry times between. Make sure to let a bit of varnish run through the smoke stack and nozzle, too.
We don’t usually go to the trouble of applying varnishes, preferring a wax/oil finish. In this case, the longevity of the toy really depended on a good coating though, and we were happy with how nicely it displays the figuring of the wood. We were however surprised at how dark our roasted maple turned after varnishing – as black as ebony!
Now, it is time to blow up balloons and give it a go!
Testing It Out!
While we had imagined how the boat would work in theory, it was a different matter to test it out and see for ourselves. Of course, for that we needed the help of our senior tester. He was only too happy to oblige.
The boat sat well in the water – it submerged right to the water line (where the light and dark maples join). We blew up a balloon and slipped it over the smoke stack. Holding a balloon on the smoke stack and blowing it up through the nozzle at the back also worked. Then we plopped the boat in the water – and what a lot of fun! It blasted out a torrent of bubbles, and after it got up a bit of momentum, went clipping right along. A balloon full of air was enough “fuel” to complete a full lap of the tub before it deflated.
Budster, who doesn’t like balloons to pop or deflate, was a little concerned at first, but quickly grew excited to see the bubbles. They made such a cheerful sound, we couldn’t help make a video of the boat running.
During the course of testing, we noticed that some balloons work better. They’re the ones that have shorter stems and sit upright. Balloons with over-long stems would tip over when fully inflated, and make the boat go ’round in circles.
Racing boats is fun, too! And, of course, playing with a boat without a balloon is completely legitimate as well, which Budster has also tried out. While making the boats, you can drill additional holes for sailors and passengers. We have made them before from pegs.
By the way, our shop is up and running again, and after having a lot of fun with our boats, we decided to offer them on our shelves. So if you don’t feel like making the boats, you can get then here! There is also a bigger version of a balloon-powered boat available.