----- Original Message ----- From: "Russell McMahon" To: Sent: Friday, October 20, 2000 3:58 AM Subject: Re: [OT]: PICinaBottle <-- Long range position feedbackanyone ? > > I wondered about active power for propulsion but felt that this would make > it more difficult. > Solar is OK but power levels would be modest and nights pose a problem :-) Actually, depending on battery life, I had planned that the boat would keep going for a little while after sunset then go to sleep until the charge rate is sufficient and get moving again. > When you consider that many ships travel large distances self fuelled it > SHOULD be possible to make a small motor power craft which will cross many > thousands of miles of sea. This concept may not scale down well? 1kg of fuel > contains say 5 to 15 kWH of energy. I have no idea of the "kg per ton mile" > performance of sea craft but no doubt this is very well established. I know > that typical petrol powered pleasure boats have mpg figures MUCH worse than > automobiles but I don't know if this has to be the case if speed can be > optimised for efficiency. > > As a totally ball park figure say that a pleasure boat achieves say 5 mpg. > This would weigh say 250 kg. > If this scales down/up linearly (I'm sure it doesn't) then a 10 kg craft > with 100% of mass as fuel (almost) would do 5 x 25 = 125 miles on its fuel. > A 1 kg on the same argument would travel 1000 miles odd. > Ships can certainly do MUCH better than this so there is something very > wrong with my assumption set. > I'm sure the model boat boys could help here - Andy? > I still prefer the "regenerative" and self contained idea of the solar-cell/battery combination but if anyone can think of a simple way of implementing a reliable sail system I would be interested. The redundancy would be great. Tobie -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics