I know next to nothing about crossing the ocean by ship, but I was under the impression that ocean currents didn't exist everywhere but only in 100 mile or so wide paths. If so, then when you encountered an unfavorable current (which you could detect by seeing by GPS that you were being driven backwards), why couldn't you set a course perpendicular to the current and sail right out of it, and then continue forward? Sean At 02:24 PM 10/21/00 -0400, you wrote: >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. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.