I've been doing a lot of research and have been following the electricboats
forum on yahoo groups for a couple of years. I have been told by AsmoMarine
and others that one motor would be sufficient to drive the boat, but I want
a little extra power to get the extra speed in emergency situations. This
is still sort of a "breadboard" project for me and there will probably end
up being modifications after the initial build.
The boat weighs in at around 16000 lbs without the perkins diesel and
nadaguides claims that the original boat was delivered with a 25hp diesel
installed. I may end up adding as much as 2000 lbs (or more) of additional
equipment with the genset and batteries which could give me 4-5 hours of
slow and silent "motoring" and considerably less at a higher speed before
the genset kicks in.
"Matt Colie" wrote in message
...
Bill,
I have been following the thread, and I believe that you might do some
thinking before you go too far....
Your ketch is probably about 15 ton. It will take both motors at flat out
to make hull speed with a more or less typical propellor efficiency. Then
there is the small matter or electric power. If you are not planning to
run it as a diesel-electric (like a Staten Island Ferry) then you will
need a huge battery collection (I am going to forego the extension cord
option).
If you run one 8hp (~6kw) motor with one 8D (230Ah) battery, the motor
will be pulling about 450amps (BIG wire) and at that load the battery will
be flat in about 15 minutes give or take.
As to the effective horsepower bit - bull....
Horsepower is horsepower and that is 746 watts. The only gain experienced
is from the constant instantaneous rotational speed that electric
provides. If you actually record the rotational speed of any IC engine
you will see significant variation that peaks at the fire pulses. This is
less pronounced with more cylinders and heavier flywheels - of course.
If you were to compare an electric drive to a little diesel of three or
four cylinders with a heavy flywheel and a reduction gear drive, you would
be hard pressed to find a difference greater than you instrument noise.
If you put out the capital for a CP wheel, what could you get for it?
Maybe another couple of minutes under power per charge. Reversing an
electric motor sure is no big problem.
There is another small problem. I have never found a CP wheel that goes
to full feather. I wanted one for a project of my own several years ago
and could find none. I wanted a marine engine with no transmission at
all, so I was hunting for a controllable/reversible pitch propellor that
could do all this. That seems to be the province of aircraft.
In any case, I wish you the best of luck..
Keep us posted how it goes.
Matt Colie - see a prior sig
Bill Farina wrote:
"John Cairns" wrote in message
. ..
"Bill Farina" wrote in message
...
"John Cairns" wrote in message
.net...
"Bill Farina" wrote in message
...
I'm in the process of building an e-boat and am looking for a ~19 inch
variable pitch prop along with probably the shaft and any controls
that may
be associated with it.
A friend of mine told me that Volvo makes one, but none of their
dealers
seem to know anything about it.
I have been told by others that older fishing boats used to use these,
but were unable to supply a manufacturer name.
If anyone knows of a source, it would be greatly appreciated.
Luke, Maxprop, Autoprop, Martec make feathering props with adjustable
pitches. They give you a recommended pitch, you make any necessary
adjustments. Pricey, very pricey in the case of the Luke, which are
one-offs.
http://www.peluke.com/Propellers/propellers.html
http://tinylink.com/?pbh5yrcpXO
Was that what you were referring to?
Exactly, thanks.
Now I just have to begin saving my pennys. :-)
You never mentioned why you wanted a feathering prop. Have you considered
a folding prop? Folders work better under sail than feathering
props-considerably less drag than feathering props-and even the best,
like Gori, run about half the cost of a feathering prop.
http://tinylink.com/?khyWB1cXEC
I have a Gori two blade standard folder, sweet.
John Cairns
I'm in the process of converting a 38' full keel Seafarer ketch from
diesel to electric. I have 2 electric etek motors that I'm going to hook
up inline via a belt drive to the prop shaft. The working hp of the two
motors is kind of vague and I'll probably be running on just one motor
most of the time. Depending on the configuration, the working hp
equivalency can be as much as 2-6 times the electrical hp (which is 8 (15
in short bursts) per etek). I want to have the flexability so that I can
tweak the prop to optimum efficiency.