[Public-list] ELECTRIC DRIVE

[Gordon Laco]

Hi everyone - 

Just had to wade into this one.

I looked at electric power for the Folkboat (about 3 tons loaded)  I came to
the conclusion that until superconductors make batteries and motors much
more efficient you can't compare electric power with internal combustion.

My feeling is that the rubber meets the road when you talk about pounds of
thrust being delivered to the water.  Water is heavy, so is the boat, and
any sort of wave action and windage really bumps up the total on the
"resistance to move forward" side of the equation.  You need a lot of amps
to get a useful amount of thrust - you can't get around that.  You need to
store those amps and then have some way to put them back into storage after
using them.  After looking at water generation, wind generation and solar
generation I kept coming back to an internal combustion engine to drive a
generator...and if you have that you might as well save a pile of money and
complexity by just letting that engine drive the boat.

On the other hand, if you have a light boat, and can plug its regulated
charger into shore power after each light usage...electric power might be
OK.  

Gord 
 #426






>> I will guess the A30 needs about 15 of it's 30 hp to go 4 >knots
> 
> At any speed less than hull speed (5 1/4 knots by my calculations) the A30
> needs way less than 15 hp. My 15 hp diesel drives the boat at 7+
> knots-although there is a gas/diesel, brake hp./shaft hp., apple/ orange.
> inability to make direct engine comparisons; not least of which electric
> motors develop max hp. just before stall, internal combustion engines have
> max hp. at max RPM.
> 
> Michael Grosh
> #220
> 
> 
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