Monday, August 31, 2009

[Electric Boats] Re: Small displacement boat question

 

a 13.5' LWL, 16' LOA displacement hull total weight on the order of 1000 lbs., plus an occupant or two. The boat is beamy at 6'

See group files, "Building an Electric Javelin", a 14 ft displacement electric with 3/4 horsepower electric drive. This boat gets along very well with 4 adults on board. 24 volt DC battery power only.
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> 1. A 1.5 HP electric motor should be capable of pushing me along at a slow but steady speed, even in a good wind, assuming an 8-10" or so prop can be fitted?

ANS: 1.5 HP is more than you need, 1 HP or less will do OK with the proper sized propeller. An 8 to 10 inch prop is way too small, and would be very inefficient, use at least a 14 inch prop. If you use a 10 inch prop, then you may need the 1.5 HP motor, but that would be poor design, using a much larger motor (and battery pack) to get the same performance as a smaller motor could give with the properly sized propeller.
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> 2. If the motor in question were so small and an AC 110v model, that the power source could simply be a gas-operated generator, say, a Honda putting out about 1000w?

ANS: The 1000 watt Honda generator will not start a 120 VAC motor that is any larger than 1/4 to 1/2 horsepower. In order to start a 1 HP 120 VAC motor, you need to have a generator rated at a few kilowatts at least. The starting electric load on almost any motor is several times the running electric load, and the generator must be capable of handling the starting load.

An alternate option is to install battery powered DC electric drive, and use the 1000 watt generator and automotive type battery charger to charge the battery pack. This would allow silent running with limited range, or continuous charging while underway (or chargine when not underway).
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> 3. Can I assume that I would not be liable to electrocute myself with such a setup?

ANS: DC system with 12 volts or 24 volts is pretty safe, higher voltages can be much more dangerous in either DC or AC. As an amateur, probably better to stay away fron the 120 volt AC system, although these can be designed and built to have good safety features with proper engineering.
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> All advice appreciated. And by all means save a life by putting me off the idea if you must!

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