[Public-list] weight distribution and electric power

[Don Campbell]

Just so you know, there is a new generator on the market called Duogen. It is a
water/wind turbine and according to Australian Yachting magazine it "was rated
the "star" bit of gear in the latest ARC transatlantic gear survey". email me
off-list for the website
Don #528

J Bergquist wrote:

> I also am looking forward to seeing the hard data.
>
> In addition to Skene, there are a number of useful propeller design books
> which contain information on the subject. Gerr's "The Propeller Handbook" is
> a good basic reference. An excellent more advanced reference is "Marine
> Propellers and Propulsion."
>
> At the end of the day, it's not a very exact science for us, because the
> wake is poorly understood. It's basically empirical and experience-based. So
> without any experience (not many people are using water generators in our
> kinds of boats), it's tough to know what to expect or what to design for.
>
> later,
>
> J
>
> On 9/29/06, Gordon Laco <mainstay at csolve.net> wrote:
> >
> > Yes, very interesting topic.
> >
> > I used to teach at Georgian College's School of Marine Technology and so
> > had
> > a terrific library at my disposal.  It was fun trying to figure out hard
> > numbers for the various options.
> >
> > With regard to the water generator, I used thrust figures for various
> > revs,
> > blade orientation, pitch, area, etc. and tried to work backwards to get
> > figures for a water DRIVEN prop (as opposed to a water driving).  Blade
> > area
> > is key, and since you can assume that slippage will happen in a similar
> > ratio to thrust producing props - the big problem is getting the revs high
> > enough and with enough torque.  Skene's Elements of Yacht Design is a book
> > with useful data on this topic.
> >
> > I too look forward to what our colleague comes up with in an actual test.
> >
> > Gord #426
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > > Gordon-
> > >
> > > I did the same math and came to the same conclusion. Why go to electric
> > and
> > > then install a generator? In fact, I looked at exactly the same
> > ones...honda
> > > air cooled gensets.
> > >
> > > I could never quantify the drag of the water generator. There are no
> > hard
> > > numbers out there on it. It's even tough to compare apples with apples
> > when
> > > comparing diesel power and electric power, because the diesel gives up a
> > lot
> > > of its available power in losses, where the electric has much lower
> > losses,
> > > and generally more available power. By available I mean that the
> > electric
> > > motor has very different torque and power characteristics which make its
> > > power more available.
> > >
> > > It's a very touchy-feely thing, which is unfortunate. And it has a lot
> > to do
> > > with your expected usage profile and how long you expect to go before
> > > selling. There are significant resale value implications.
> > >
> > > At the end of the day, there is a lot more Q per pound in internal
> > > combustion. But if you can deal with the lower Q value per pound,
> > electric
> > > can be pretty doggone nice. Simple. Quiet. No smell. Always ready to go.
> > > Pretty slick...
> > >
> > > Personally, I am very interested to see how Dan's project turns out. It
> > may
> > > work very well, in which case I'd say it might be something for others
> > to
> > > consider too. I just didn't have the guts to try it like Dan has. Let
> > myself
> > > be talked into sticking with internal combustion...a decision I half
> > regret.
> > >
> > >
> > > Later,
> > >
> > > JB
> > >
> > > On 9/29/06, Gordon Laco <mainstay at csolve.net> wrote:
> > >>
> > >> I did a bit of figuring on this issue back when considering an electric
> > >> aux
> > >> in my old boat.  The water generator is not an inconsiderable drag
> > while
> > >> sailing.  I fell back on looking at fitting a small Honda generator,
> > which
> > >> would have done a fine job but there I was back with gasoline but this
> > >> time
> > >> in addition to the extra batteries and lower thrust the e motor could
> > >> deliver...
> > >>
> > >> Gord #426
> > >>
> > >>
> > >>
> >
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