Hi Matt, I considered having the "bridge" of the boat only a few centimeters above sea-level to help keep it's center of gravity as low as possible so I assume it will be constantly washed by the waves and no salt will get deposited on it's solar panels. As for the amount of sunlight available to the solar panels I guess that the washing of the water does have a certain effect but is it really that important overall ? Cloudy weather I can live with, the boat will simply sleep more often I guess. What would the minimum speed required to fight the currents and get across the ocean be ? I don't really mind if it takes 6 months for the thing to get across so I guess I should maybe rename this a "stubborn drifter" rather than a boat ... Tobie Horswill thorswil@videotron.ca ----- Original Message ----- From: "Matt Bennett" To: Sent: Saturday, October 21, 2000 9:29 AM Subject: Re: [OT]: PICinaBottle <-- Long range position feedback anyone ? > I'm getting into this conversation rather late, but until March, I used > to work on a rather similar project: > We put > these little robot boats into the middle of the Atlantic and had them > listen for an impact of a missle during a submarine launched ballistic > missle test. Neat stuff. During this job, I had the opportunity to be > at sea for 5 weeks (on a ~300 ft oceanographic survey ship) supporting > it and I have a few observations- > > 1. Don't count on solar power. It is very often cloudy at sea, and > infrequently full sun. if the seas get calm enough for your solar > panels to stay above the water for a while, you're going to get a nasty > layer of salt dried on top of them which kill the efficiency. In fact, > everything above the waterline will have to survive and operate with a > layer of salt on it. > > 2. The waves in the middle of the ocean are just big enough to be > annoying- usually between 3 and 5 feet (pk-pk) and relatively long > wavelength. This motion will serve to work harden virtually any antenna > scheme you have. Unless you are in a storm. Thats where you find the > biggies. > > 3. The sea is incredibly corrosive. Anything that doesn't corrode is > going to get scum on it. We saw the beginnings of corrosion to the > aluminum and steel in less than 10 hours of deployment, and even the > stainless steel screws started to corrode after a while. > > 4. Don't count on moving around under battery power. Out little boats > were small (about a foot wide, 3 feet deep and 3 feet long, with > pontoons for stability) With 2 trolling motors to steer it with > differential steering. This could keep us in one place against 2 knot > currents for *maybe* 48 hours. This is with 160A-Hr of batteries (about > 200 lb.) > > 5. We had differing opinions about marker lights at night- all big > ships at sea are expected to have them. I don't know how your little > boat falls under these rules. We put a single while marker light (10W, > I think) on a mast. > > 6. Your little boat could be considered a hazard to navigation. If > someone does find it, realistically there is no way to prevent them from > picking it up and taking it as a "service" to the other ships at sea. > > 7. Abandon all hope of VHF or higher frequency radios back to a land > based receiver. We needed bandwidth, so we used 900 MHz radios, which > got us about 10 miles from an antenna 2 feet above the water to an > antenna 90 ft. above the water. If you have a GPS trained clock, you > can synchronize the two receivers pretty well and get some pretty > impressive operation under bad S/N conditions with modulations like > spread spectrum. > > Matt > And to keep it appropriate for the PICLIST- I put a couple of PICs on > it- 2 12C672's, which served as the motor PWM controller (with a bunch > of MOSFETS) and a scuttle controller if we had to abandon them. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.