by John B. Carnett: John B. Carnett

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The Homemade Spy Sub

Cost: $300
Time: 4
Days
Easy | | | | Hard

Some fathers and sons play catch. Electrical engineer Jason Rollette and his 12-year-old son Trevor are a little more ambitious. Hoping to explore the lakes and rivers near their Milwaukee home, they´ve built their own underwater remote-operated vehicle, or ROV. Controlled and powered by a laptop, their ROV can swim more than a quarter of a mile, to depths of 250 feet, while a home-surveillance camera sealed inside sends a live feed to the pilots onshore.

The camera, electronics and lights fit inside two- to four-inch-diameter PVC piping. The pipes had watertight O-rings at their joints, so Rollette created windows from Plexiglas and screwed them onto the ends. Bilge pumps-which typically pump water out of a boat-act as thrusters, each spitting out up to 1,250 gallons an hour in different directions through plastic tubes. He plans to attach a motorized claw for grabbing treasure.

The trickiest part of the build proved to be the computer control. Rollette isn´t a programmer, so he recruited help through his blog (rollette.com). Thanks to volunteers, he and Trevor now steer the craft with a gaming joystick while monitoring video-as well as depth, compass heading and other navigation details-on their laptop. The next step, suggested by Trevor: CO2-powered torpedoes... you know, just in case.

How It Works (Click here for photos)

• Thrust: Six bilge pumps, mounted on ceiling-tile grates that sit between the pipes, force water through one of six plastic tubes, pushing the vehicle left or right and forward or backward or changing the angle of its dive.
• Control: A joystick steers the rig, and an interface on the laptop lets the driver zoom the video or snap a photo.
• Communications: Video, power and navigation info are all transmitted over a quarter-mile-long Ethernet cable in a waterproof sleeve.