Boats are wonderful things to make when you're getting into the RC hobby. The electronics and control systems are very simple and when it comes to design, the sky is the limit. A horrible design will not lead to the whole thing crashing down, such as in the case of an aircraft, and if it sinks (or capsizes, such as what happened in my case initially), the only replacement part I needed was a new Electronic Speed Controller. I built this after my ill fated attempts to build a tricopter and all of the parts were taken from that build, so improvisation is the name of the game. The main aim is to get it running as quickly as possible so you can extract maximum run time and you can make as many iterations as you want. Plus, unlike a multirotor, the battery life is phenomenal as it doesn't need the full power output of the motor to just potter around, and it has only one motor! So as you can see, I've used household materials as much as possible and the only specialized equipment is the electronics.
Satisfaction to effort ratio with this build is epic :) so you can have hours of fun with minimal effort, and this is a good springboard to get kids into the hobby.
Step 1: Step 1: Gather the Materials or Raid a Dumpster
1 X DT750 outrunner brushless motor
1 X 10x4.5 slowflyer prop
1 X el cheapo 9 gram servo
1 X 2200mAh Lipoly 3 cell battery
1 X 20A Mystery ESC
Silicone wire (cut to the length you require)
1 X whatever RC RX/TX combo you have
3 X 1 litre plastic water bottles
Scrap wood strips (whatever you may have lying around)
Cardboard or balsa wood, whatever floats your boat :P (see what i did there?)
Zipties in the millions
Step 2: Step 2 : Making the Frame
I don't have any pictures of the boat during construction, so I am using Sketchup diagrams to explain. Make a frame like the one seen in the above picture. I am using a reverse tricycle design as it'll have less tendency to tip over. My initial design was normal tricycle design with disastrous consequences. To read more about those fails, check out my blog:
I used cyanoacrylate to glue the pieces of the frame together but you can just as easily use nuts and bolts.
The bottles are attached to the frame by poking four holes through them and threading zip ties around the frame and through the bottles. This holds up pretty well and if you want to make any design changes wrt the arrangement of bottles, you can easily slide them out and put them on a different frame.
You can see how the arrangement will look in the actual picture of the boat above.
Step 3: Step 3: the Elctronics and the Steering Mechanism
Looking at the sketchup diagram above, you can see the various parts and their arrangement. The motor is wired up to the ESC and it is attached to the motor mount. The ESC is located right behind the mount for cooling purposes. The battery is placed centrally to keep the CG as low as possible and in the middle of the whole boat.
The connection scheme for the ESC - motor arrangement can be found in numerous sites online but I'll give a brief description here:
The ESC has three outputs and each of these are connected to the motor. The motor direction is dependent on the way the ESC is connected to it. At first if it doesn't spin in the right direction, switch two of the ESC leads and it'll spin the right way. Here the motor is in a TRACTOR configuration, ie. the motor+prop combo is PULLING the boat. If they were pushing, it would be called a PUSHER configuration. It is a good practice to use gold plated plugs to make the connections as it becomes easier to change parts if one of them fails.
I used zipties to attach the motor to the frame and velcro strips to attach the battery, to make it easy to remove for charging.
For more detailed description on RC how-to's check out flitetest.com and their youtube channel. Those guys make everything look incredibly simple and easy to understand.
The rudder is basically a piece of cardboard glued to the mount at the rear. It is creased to allow it to bend easily when it is attached to the servo. The servo horn is attached to the rudder level with the servo arm and attached to it with a stiff metal wire, such as those in paper clips or safety pins. The second sketchup diagram illustrates this arrangement.
Step 4: Step 4: General Wiring
The ESC is connected to the motor on one end and the battery on the other. Make sure you connect the battery at the end, after making all the other connections and without a prop attached to the motor. If you spin it up without making sure everything is secured, there may be disastrous consequences to eyeballs everywhere. The 3rd channel of the rx, in my case is the motor control channel and the 1st channel is the aileron channel. So plug the leads of the servo into the appropriate port on the receiver and do the same for the ESC. In most cases, the ESC supplies power to run the Rx and the Servo so a battery elimination circuit (BEC) is not required. In case your ESC doesn't supply power, you will have to draw out another line from the battery for the ESC. Above diagrams shows the motor connections.
For more info check out the below video:
Step 5: Step 5: Final Adjustments
After all the testing is done, attach your prop the right way up to your motor. Always make sure the printed side of the prop is pointing towards you. I used zipties to attach the prop, but the conventional way is to use locknuts and washers. Attach the battery to the ESC, and do smoke test: if you become a passive smoker, something is wrong and disconnect immediately. If all goes well, you will hear three beeps : beep beep beeeeep from the ESC indicating everything is A OK. Give it a little throttle and see if the prop is spinning in the right direction. Don't throttle up too much, the above combination of motor and ESC gives around a kilogram of thrust! So you don't want it to rain broken boat pieces. Center the servo using the trims and make sure there is full throw of the rudder when you move the stick. In a Mode 2 radio, such as what I have, I connected the rudder to the aileron channel so that I can use one hand for the throttle and the other for the rudder. You can change it to whatever mode and arrangement you find easy to use. ALWAYS REMEMBER TO TURN ON YOUR TX BEFORE YOU CONNECT THE BATTERY!
After this is done, unplug the battery and fill the bottles up with some sand to weigh it down. My first model capsized as it was too light and tipped over while performing a particularly sharp turn. If that happens, you will have one fried ESC and a dead boat. Everything else should work after drying them off but don't push your luck :P
Place the boat in the water and it should sink to about an inch below the water atleast. In my boat I also taped some old spent 9V batteries for added weight.
The first picture shows my ill fated first design which capsized.
The second shows the one which I built with the reverse tricycle config.
Step 6: Step 6: and You're Done!!
Go ride the waves with the dolphins!
I'm kidding, this has the profile of a barge in water, so you want be doing any hair raising speeds. It is capable, but i don't trust the frame to handle full throttle of the motor.
So there you have it! A cheap, easy to make RC boat which is fun to make and you won't be distraught if someone blew it up in a James Bond-esque chase scene in a film where the villain has plans of world domination by creating an artificial scarcity by hoarding plastic water bottles.
I don't have any pics of the reincarnated version in the water, so you will have to imagine how that looks :P
PS: I am entering this in the Green design contest so please vote for me if you like this Instructable :D
Also check out my blog for more of my misadventures! : Whatthegell!!!