WiFi Sailboat Passes Bathtub Test


Last summer, I built a pop-bottle sailboat with my (then) four year old.  After trying a couple of designs with keels in our bathtub, we settled on a catamaran style design with two pop bottles.  We tied a string to it, threw it into the pond, let the wind carry it away, and then pulled it back to shore.

And I thought, wouldn’t it be cool to add remote control functionality?

So I did.  I finished my smartphone controlled, WiFi sailboat on Saturday.

Field test on a rainy, windless day. The bane of any sailor.

The sailboat consists of:

  • 2 x 2L pop bottles
  • Rubbermaid body
  • Plastic shopping bag sail
  • Dowel mast, plywood rudder
  • 2 servos
  • Raspberry Pi with USB WiFi adapter
  • Arduino Uno
  • AA Battery pack with a 5V regulator

I configured the Raspberry Pi to act as a WiFi hot spot.  Using any smart phone, you can connect to the boat, and visit its web page.

The page has two jQuery slider controls.

Web Interface - jQuery sliders control the sail and rudder

When re-positioned, the slider controls drive a PHP page which sends commands over the USB interface to the Arduino, which then controls the servos.

It seems like overkill - an Arduino AND a Raspberry Pi for such a simple task?  I’d considered alternatives - using only an Arduino with Bluetooth or another wireless interface, or using the Raspberry Pi to directly control the servos - but in then end, I just used the parts I had on hand.

My initial design used a 7805 IC to supply the 5V for power - that didn’t work…  Everything would boot, the 7805 would get super-hot, and the Raspberry Pi would crash after moving a servo a few times.  A little reading lead me to pick up a switching regulator (I happened to pick up one from Castle Creations at my local hobby store).

I tested the design out with my assistant in our bathtub, and everything worked!

Bathtub Test Video

But, by the time everything was built, the city drained the reflecting pool I had intended to use for trials for the fall - I had to try it out in a nearby pond.  And, of course, there was no wind.  I’ll post more photos following a windy day test.

Check out these far grander projects - these individuals are trying to build autonomous boats that can cross the Atlantic:

With a little more money, and a little more time, I think it would be fun to build a boat I could launch in lake Ontario, at the foot of Yonge St., to sail autonomously down the St. Lawrence to Brockville, where friends in Ottawa could retrieve it.

Download Sailboat Project Files