Turn an RC Plane Into an RC Boat

The remote control airplane was only $30 at Harbor Freight.  I put it together in about 20 minutes, on the living room coffee table, during my two-year old son's nap time.  It was much easier to assemble than the complicated and expensive gas powered RC plane I built as a teenager, but it was also palpably cheap.  The battery charger doesn't have a light, so I read the instructions carefully to figure out how to tell when the batteries are fully charged. The answer: "When they start to feel hot."

A few weeks later there is a calm Sunday morning. My wife pushes the stroller while I carry the bright yellow plane down to the empty soccer field. The air isn't completely still, but the small gusts are only enough to rustle the leaves of the trees at the edge of the field.

I show my wife the arm motion to launch it, and then I push the stick all the way forward to full throttle. She tosses it, just right, into the air. I had trimmed it beforehand but it immediately begins to veer right. I nudge the stick left and keep the throttle high but it banks hard and loses lift, and before I can back off on the the throttle the plane flies hard into the pavement at the edge of the tennis courts. My son and I run over to inspect the damage. The wing and the body are in pieces.

I feel a little sorry for myself, and have the thought that I'm not cut out for RC airplanes. I remember how more or less the same thing happened the last time I tried to fly an RC plane I'd put together, when I was a teenager. And in the midst of my disappointment and self-recrimination, I notice that the innards - the RC receiver, battery, props, and motors, are all intact.  I get out my leatherman and free them from the wreckage. It occurs to me that boats are easier.

* * *

Acquire an inexpensive remote control airplane with two electric motors that can be controlled independently. Remove the motors, battery pack, and radio receiver from the plane.

As I walked home I thought about getting a cheap toy boat and gluing the motors and props onto it. I searched a few websites of crafts stores, but didn't find anything promising. So I searched for boats on instructables, hoping to find a simple design I could build from stuff lying around the house. I came across something made by some guys from the Netherlands who built model sailboats out of PVC pipe to pick up trash from the Ocean. I decide not to do that -- too lazy to go to the hardware store, and I don't like PVC much. But the fact that they use deep keels with lots of ballast at the bottom sticks in my mind.

Since I don't have anything boat-like, I dig through the recycling bin and come up with two bottles, neither of which are very smooth, but I'm not picky. (A friend of mine, hacker extraordinaire, broke me of that habit.) I rinse them and put them in the bathtub with a little water, to see how they behave. One gets chosen for my boat, and the other becomes my son's favorite bath toy.

* * *

Find a clean plastic juice bottle (64 ounce or nearabouts), and a piece of bamboo or pipe with a diameter approximately the same size as the electric motors that drive the props.  The bamboo should be long enough so that the props can be mounted just inside either end, with just enough clearance so that they don't strike the side of the bottle boat when spinning.

With a pocket knife or small wood saw, cut notches in the end of your bamboo such that the distance between them is approximately the thickness of the electric motor that drives the props.  Remove the material from between the notches, and insert the motor - it should fit snuggly into the end of your pipe. Secure with zip ties, hot glue, duct tape, chewing gum, pine sap, or whatever is at hand.

I put different things in different places, imagine how the props would drive it, rummage in the basement for materials, repeat. In short, I tinker.

* * *

Next zip tie the bamboo motor mount onto the top of the bottle, a little aft of the middle. To do this, you'll need to make 2 holes for each of the two zip ties, approximately the thickness of the bamboo apart. The two ties should be offset a few inches to keep the motor mount pipe perpendicular to the centerline of the bottle.

Once the holes are made, you'll insert one end of the zip tie and then use a stick or piece of bamboo or something to coax it out of the second hole. Do the same for the other zip tie. Now lay your bamboo motor mount in its position across the top, with the propellers on the rear side of the motor (i.e. not the way I did it in the picture below!)

Cinch down the zip ties. Hopefully your mount will be firmly attached, and generally pointing in the right direction. 

Now is a good time to insert the radio receiver antenna wire into the bottle, through one of the holes you threaded a zip tie through. It should have plenty of room to spread out in order to catch the signal from the transmitter.

In order to keep your sensitive electronics dry, you'll need to add a keel of some sort. It should be heavy enough that the bottle cannot heel over enough to get the motors wet, or capsize. I used a 4 inch bolt with as many 5/8" nuts as I could fit on it, but this makes for an unwieldy and rather poorly shaped keel, and the zip ties used to secure it don't help. Lead fishing weights, or any dense, heavy object that is smooth and can be mounted securely, would be a better choice.

For the body of the keel, use a a piece of cedar shim or anything of suitable size and thickness. Mount it to the bottle by a piece of pipe hanging strap wrapped around it. Bend the strap 90 degrees at the point where it meets the keel, but do so such that when you put a bolt through the the strap and keel and tighten it, it will compress the strap and grip the bottle securely.

Get a small plastic bottle -  Gatorade is a good choice - and cut off the bottom third with scissors or a bandsaw. Cut out a notch for the bamboo motor mount , such that the bottle fits over it as snug as possible. Use a rubber band in the front and one in the back to hold the cowling on top of the bottle, thereby sheltering the radio and battery pack from any spray kicked up by your props.

Depending on how lucky you feel, you may also want to cover your motors and any exposed wiring with saran wrap, with a little duct tape to hold it all together. Waterproofing never hurts.

Fire up your radio, put your boat in the water, and let her rip! You may want to have a helpful assistant stand in the water to ensure that the balance of the keel is sufficient to keep the boat from capsizing.  If you end up soaking the electronics, remove the battery pack as quickly as possible, and let everything dry out for a day or so, then see if it still works.

This entire project - from destruction of airplane, to launch of boat - took me about 2 1/2 hours of playful and mostly uncritical tinkering. That means there is *vast* room for improvement in most or all areas. For example - it's very hard to keep the boat traveling in a straight line with this configuration. A streamlined keel, and props oriented closer to one another, would probably help with that. But then the ship might not be able to twirl and pirouette quite as dramatically either.

Endnote:
I love instructables. They provide great inspiration and the details necessary to re-create something. But like recipes, they tend to omit the processes that led to their creation -- the blind alleys, the silly ideas that lead to better ones, and the messy subjective experience of the creator. There are good reasons for this omission: a recipe is more concise and easier to write. But I wish there were better ways to document the whole creative process, not just where it ends up. Maybe then we'd have the courage to leave space in education for the messy bits of creativity, instead of making kids endlessly reproduce someone else's success, grown stale with the years.

My colleague Tiffany Tseng has created a platform called Build in Progress to try out different ways of documenting the creative process.  You can find out more on the About page.