|Posted on March 18, 2019 at 5:10 PM|
Airboats are pretty cool, even though they don’t actually sail through the air. Traditional boats push themselves through the water by exerting force on the water itself. Airboats push themselves over the water by exerting force on the air behind the boat. Thanks to the lack of a motor or propellers in the water, combined with their flat bottoms, these types of boats are perfect for navigating places we wouldn’t normally be able to reach with a traditional boat.
While many hunters or anglers use airboats (a.k.a. fanboats) in their expeditions, they’ve also become a great tool for conservationists, researchers, and eco-tourists! Fanboats are used to access swamps and marshlands containing a vast number of species to be studied and provide a way to quickly get from one site to another without risking serious harm to aquatic creatures, such as manatees or alligators. But before you go out looking for an airboat to pilot, it’s important to understand how they work. For that, we can build our own simple airboat while challenging our STEAM skills!
Fanboat STEAM Challenge!
What you will need:
-Small hobby motor (3-6v will work, but up to 12v will do just fine)
-A clean, empty beverage can
-A boat body
-A motor mount
-Small rubber bands
-Something to waterproff/protect the battery
The boat body:
Here’s the first part of this STEAM challenge! Find or create a small boat body! For our fanboat, we actually still had an unfinished tea tray, which happened to work out pretty well. Be creative, though! You can make the body of your boat out of tin foil, popsicle sticks, an old shoe sole, or whatever! Just make sure it has a flat bottom, can float, is watersafe/watertight, and that you’ll have places to mount the motor on the back and store the battery on board. Once you have the body of the boat made or figured out, it’s time to mount the propeller and battery case!
The motor mount:
Again, this is a challenge, which means you’ll have to come up with something yourself. For our tea tray boat, we glued a couple of pieces of wood shim together to act as the motor mount. You just need something to hold the motor level and in place. If you’re using tin foil, it might be best to add double-sided tape or something else to insulate between the motor and the foil. Once you have your mount figured out, install the mount into your boat. For ours, we simply glued the mount into the boat. Once the mount has been installed, attach the motor to the mount. If you’re gluing the motor on, be sure not to get any adhesives inside the motor or on any of the moving parts outside of the motor.
The battery case:
The next part of this challenge is figuring out how to waterproof and protect the source of power for your boat. For ours, we used an empty breath-mint container. The container actually helped provide a nice counterbalance to the motor, so our boat wasn’t sinking too far down on the back end. If you can’t find or make anything in your home to do the job, you should be able to find waterproof battery cases at your local craft or hobby store.
Glue or attach your battery case, and (carefully) wire the battery to your motor to make sure everything works. If you have the know-how and materials, you can add some power regulation and on on/off switch the your circuit, but for our project we just stuck with a simple direct current circuit (power source directly tied to motor). Just keep in mind that without power regulation, your battery may fry out your motor or vice versa, so pay attention to the power requirements and limits of both.
Finally, use some electrical tape to insulate and protect any exposed wiring. If too much moisture gets on any exposed wires while the circuit is hot, it can cause a short out potentially damage your motor or battery. As you can see in the pictures, we didn’t protect exposed wires on our motor, and ended up ultimately frying out the motor as a result.
Next, we need to make and attach a propeller to the motor. To do so, draw and (carefully) cut your propeller out of an empty, clean beverage can. Below is the simple shape we used, but experimentation is always encouraged! Some cans may be thinner than others, so you may have to cut multiple copies of your propeller out and glue them together. Wrap a rubber band around the output shaft (the part that spins) on the motor. This will help hold the propeller in place. Next, punch or drill a hole out of the center of your newly made propeller unit. Be sure the hole is just big enough to fit the shaft into.
To finish installing your propeller, slide the propeller onto the shaft, and tightly wrap the other rubber band around the shaft. Push both rubber bands tightly against the shaft, so they hold it from both sides. You may need to add a little glue to the rubber bands to make sure the blade doesn’t come loose.
Flat propeller blades aren’t good for moving things so much as they are for cutting things up, so you’re going to have to bend the blades. Doing so will change the “pitch” of the blades. You’ll have to experiment a bit with what angle the blades should be at to push your fanboat rather than pull it. Just remember that different parts of the blade move at different speeds while rotating, so the pitch shouldn’t be the same all the way down the blade. Likely, the pitch will be steeper (more angled) at the base of the blade, and shallower (more flat) at the end of the blade. If you need a little visual inspiration, check out the fans most people use to cool their homes during the warmer seasons.
At this point, it’s important to test everything out and ask yourself a few questions before taking your craft to water.
-Is the boat able to float and water tight?
-Is the battery water-safe?
-Is the propeller pitch pushing or pulling?
-Are wired connections insulated and/or protected?
-Is the motor system functioning?
After a final test to make sure everything works as expected, your boat is ready to take to the water! Just be sure not to send it onto a body of water that you won’t be able to recover it from, such as a lake or pond. Just to be safe, it may be worth attaching a light string or fishing line to it. If it gets too far out of reach, you could just reel it back in!
The reason this simple little fan is moving your boat has a lot to do with Newton’s Third Law, which states that every action has an opposite and equal reaction. As the fan pushes the air backwards behind the boat, the air propels the boat forward. If you only consider Newton’s Third Law, though, you may be left wondering why the boat doesn’t seem to move as quickly as it should. A seemingly simple problem may have some very complex answers, though!
The first thing to consider is Newton’s Second Law, which states that the greater the mass of an object, the greater the force needed to move it is. Already, your propeller must be strong enough to overcome the mass of your boat.
The next thing to consider is that the force moving the boat forward IS the same as the force of the air being pushed behind the boat, but the forces of gravity and friction play a role, as well. Air friction is acting on the boat, producing more sets of equal and opposite reactions (known as “drag”). Friction from the water is also acting on the boat, creating even more sets of equal and opposite reactions. Gravity is ALSO acting on the boat, creating EVEN MORE sets of opposite and equal reactions. These types of reactions play into Newton’s First Law, which states that an object at rest will stay at rest unless acted on by an unbalanced force. Friction and gravity hold the boat in place, “at rest.”
This is the first in a new series of blog posts with challenges in STEAM skills. A lot of the instruction was left somewhat vague and open because we want you to use those wonderful brains of yours to design and create your own versions of this project, using materials and resources you have locally available. Not only does this help you practice your critical thinking skills, but it helps you learn and practice skills used in almost every field of STEM and STEAM research!
Not only we love to see your designs and how they turned out, but sharing your knowledge may help others build on it and create a better version for everyone to benefit from! Share your results with us on our Facebook Page, Instagram, or post it on Twitter with the hashtag #COTairboatchallenge
CJ w/ Children of Terra-NEO
https://www.explainthatstuff.com/how-propellers-work.html" target="_blank">Explain That Stuff: How Propellers Work
https://www.physicsclassroom.com/class/newtlaws/Lesson-4/Newton-s-Third-Law" target="_blank">Physics Classroom: Newton's Laws