>>     So, the model I have in mind at this moment looks more like a
sailboat.
>> No mast, no propeller, no rudder and no keel either. I figure than
anything
>> protruding from the boat is at risk of getting broken by a ship, a rock
or
>> whatever and that a propeller or a rudder is doomed to get jammed in
algae
>> or floating trash. It will be made of 2 shells of 1/4" Lexan suction
molded
>> around a styrofoam shape containing a PIC, GPS, digital compass ,
batteries,
>> motors and perhaps somekind of RF stage. Two turbines go through the boat
>> from bow to stern, sucking in water from the front of the boat and
spitting
>> it out at the back. Instead of a rudder I plan on having a sideways


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 :-)
.
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?





      Russell McMahon
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