MAX EBB — I
t was the morning of the first race in the winter series, and the dock was a busy place, with more pre-race activity than on a typical summer race day in the YRA season. This was probably a reflection of the aging fleet. There seems to be a growing preference for winter racing these days, especially since my club cancels for rain or gale-force winds. "We get to be cold, wet heroes all summer," explained the Race Committee Chair. "In the winter, we should only have to race in pleasant weather." It was, in fact, a beautiful warm sunny morning, and the wind for this winter race promised to be more like a calm summer day in Long Island Sound. The only problem was that my diver — who was scheduled to give my bottom a badly needed scrubbing — was nowhere to be seen, and she had not left the usual business card to show that she had already come and gone. I walked down the dock to see if she was working on another boat nearby. I didn't find the diver, but I did run into Lee Helm, naval architecture grad student, working the same problem from a different angle. Lee often sails with me as mainsheet trimmer and tactician — but for this race I wasn't fast enough with the crew calls, and she had signed aboard a smaller, faster, and much more
PHOTOS / MAX EBB modern race boat for the winter series. It's a lesson I should have learned long ago: Make your crew calls early, supply a top-end lunch, and be generous with the swag like boat shirts and custom logo sea bags. Lee was hard at work on her boat's bottom, using a long-handled flotation bottom brush of her own design. I had seen this brush in operation before. It's made of PVC pipe for the straight part, half of an old windsur fer boom for the curved part, a push brush from the hardware store, and a fender supplying the flotation to hold the brush against the hull or keel. But there was a new addition to the rig: Lee had her eyes glued to a cellphone attached to the brush's T-handle. I stopped to look over her shoulder. Sure enough, the image on the phone showed the business end of the brush moving over a small patch of the boat's hull. "Lee!" I exclaimed. "You've done it!" How did you get the Wi-Fi signal to go through water? This had always been the problem. Little waterproof cameras like the GoPro all feature remote operation and real-time monitoring via cellphone, but
"The divers will be the first to invest in these hull-cleaning drones, and they'll use them to expand their business."
The business end of Lee's video brush, minus the brush part.
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Latitude 38
• November, 2018
the signal does not go through water. "Wi-Fi is like, 2.4 gigahertz," Lee explained, "and that's a frequency that's absorbed by water. But I found a way to send the video signal up to the brush handle by cable." We had thought of this befor e, but the problem is that the tiny underwater housing leaves no room for a cable attachment inside the case. There are commercial systems that circumvent this problem with an alternate underwater case design, but they are pricey. "How did you do it?" I asked. "It's diabolically simple," she answered. "Just tape a piece of coax cable to the back of the camera case, with 6.25 centimeters of the core exposed." "6.25 centimeters?" I asked. "Sure. The speed of light is three times tento-the-eighth, or like, 300 million meters per second. Actually 299.8 in space, 299.7 in air, but three hundred is close enough. Divide by the Wi-Fi frequency of 2.4 gigahertz, and you get 0.125 meters, or 12.5 centimeters. That's the full wavelength and it won't fit on the back of the camera, so use a half wave, 6.25 centimeters of bare coax core." "But how do you connect this to the camera, without having to buy a larger underwater case?" "That's the cool part, Max. You don't need to connect anything, just stick it to the back of the case with duct tape. The signal gets through just fine. At the other end, I have the same 6.25 centimeters of coax core taped to the back of the phone." "What a great hack!" I said. "But shouldn't you really be using the speed of light in seawater? It's just a very thin layer between the casing and the wire, but still." "Not for a Wi-Fi signal," answered Lee. "The propagation speed of a radio signal in seawater is not the same as the speed of light. It's a strong function of the elec-