Dr.Mark,
Asking "how far and fast..." questions of battery-only electric boats will always be disappointing (with current technology) to those not already sold on battery-only boats.
Asking "how maneuverable, how reliable, how torquey, how much, how safe..." questions will grow the market exponentially. Even detaching "far" and "fast" gains market share for battery-only propulsion solutions, as batteries do either well (but not both). If the current battery technology had 100,000 times the energy density, everyone would go battery-only.
As it is, battery-only auxiliary sailboat propulsion is on the margins. As Arby said, "one gallon of gas is 800lbs of battery," and Keith harangues wisely about imagining "that you started [a] trip with only 1 gallon of fuel."
If you need fast + range, diesel/electric makes an efficient system. If you ALSO want easy maneuvering, diesel/battery/
Thanks for putting that box of soap out there for me to stand on.
Mark Stafford
P.S. If that is 25' LWL, 100watt regen, for 24hours, maybe 6knots for 1/10 mile? Regen works for LED lighting and occasional radio. Hull speed propulsion is much thirstier.
--- In electricboats@
>
> The most compelling argument Keith makes, for me, is that if regen worked so well there would be a booming tow generator biz. But the ones I've found look pretty anemic, 100 watts is big time. If you're cruising offshore, 2400 kw a day is not bad.
>
> But how far and fast will that push a 25 ft 4500 pound displacement hull?
>
> md
>
>
>
> --- In electricboats@
> >
> > There is only one possible conclusion..
> >
> > ...Golf carts should have sails!!
> >
> >
> > Seriously though...I do think that eventually regen can get practical (my "X-prize" standard is 10:1 ratio). But you probably need some combination of (as mentioned many times)
> >
> > o fancy controller to auto-feather without stalling
> > o Optimized prop design that can generate lift in reverse
> > o Over-sized (and therefore probably pod-mounted) and maybe shrouded/ducted props - note: these need to be running all the time while sailing or the drag would be too great, so technically you're now a powerboat.
> >
> > That's why I call it a science experiment - if you've got more money and time than common sense you'll be a perfect candidate!!
> >
> > But consider - if this really worked there would already be a tow-generator on the market that would make stupendous claims about how much power they generate (in reality a good one gives 6-8amps @12V - about 100watts*...
> >
> > -Keith
> >
> > (* references: http://www.jgtech.
> >
>
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