Subject: [harryproa] Re: Electric drive for Harryproa
From: "jjtctaylor" <>
Date: 4/3/2008, 7:55 PM

Hi George,

I conversed with Kevin Plank and it is true you could run a 3000 system motor at a higher
wattage. BUT he states a 3000 motor can only run continuously at 80 amps or the MOTOR
will overheat. The controller itself can run at 170 amps continuously, yet not the motor.
AND it is true you can run 400 amps but no more than 10 seconds or so, much like a bow
thruster. Therefore his literature states now a max recommended cruise of about 60
amps. Devil in the pesky details. While he won't extrapolate how long you can run over
80 amps since that depends on water temp, etc. just know you won't be able to do that

The back end issue is batteries, AGM can handle higher discharge rates, while others like
typical lead acid don't like it. Lot's of new battery technologies coming available soon.
Firefly by August 08.

So just be VERY careful about elec motor sizing. Max HP of a diesel can be run for
extended periods without damage so just be sure the motor rating is matched for both
the short and long term running. Nigel Caulder spells it out very clearly in his review in
Professional Boatbuilding. 4KW (48V x 80amp) is still 5HP+ and while that performs
MUCH better than a larger diesel at low rpm, the diesel will continue to drive that prop
rpm up to its higher RPM using its peak HP capability. All a function of the torque curves.

The comparison performance levels at RE-E-Power are very misleading. From what I can
find a honda 9.9 HP power prop puts out about 250 pounds of thrust. That is a just a
little more than a 4KW elec drive. Just validate your complete needs and all will work out
well for happy cruising. I like electric myself. Just a challenge to get it all together
without excess weight.


--- In, George Kuck <chesapeake410@...> wrote:
> Hello, JT
> You are correct in that the electric is good for low speed with a flat torque curve. But
if the motor is sized correctly its power should not be a problem. It should be pointed out
that you can not make a direct comparison of the HP since a gas or diesel is rated at max
HP and an electric is rated at continuous HP. An electric rated at 48 VDC,170 amps would
be 10.94 HP but the same motor may have a max HP twice this amount which can be used
for short duration. The Re-E-Power system 3000 is rated at 170 amps continuous but
has a max of 400amps ! Of course you could not pull this much amps for vary long. I do
not think that a gas or diesel engine would last vary long if it were run at full throttle
> There are other reasons to go with a electric drive, they are quieter, cleaner, simpler.
But if you think you need a diesel you can install a diesel generator to supplement the
battery pack for more range and to provide electric for the boat.
> One factor that may be overlooked though with electric is the power capacity of the
controller. This is as important or more so than the power of the motor. If you have a
motor with a 10 kw capacity but a controller with only 8 Kw max output you will limit the
output of the motor.
> Happy sailing,
> George Kuck
> Chestertown, MD
> jjtctaylor <jtaylor412@...> wrote:
> Just two cavets to electric drives. As many profess electric has low
> speed advantage over diesel with a flat torque curve all the way up
> to max rpm. Great for harbor maneuvers. They don't have more power
> than a diesel of similar rating. Check Profesional Boat builder
> earlier this year, think Jan & Feb for detailed analysis by Nigel
> Caulder. So if you are pinned off a lee shore make sure you have
> sufficient HP or KW to move forward.
> #2 If you pod mount off a rudder, your steering rudder, then you can
> expect an autopilot to not handle it well. If at ALL ! The
> autopilot tunes to rudder response versus boat performance. The
> drive will cause it to overshoot and thus will be extremely diffciult
> to dampen. If the pilot ever manages to eventually tune to work, if
> you change thrust on the electric motor the tuning will fail again.
> JT
> --- In, "Rob Denney" <harryproa@>
> wrote:
> >
> > G'day,
> >
> > Blind Date is getting an electric motor this winter. The 66'ter in
> Portugal
> > and the 60' charter boat are both planning on having them as well.
> >
> > Putting them on the rudders solves the two way problem and gives
> amazing
> > maneuverability. Would only need one if it was powerful enough.
> No real
> > drawings yet, but the principle is a sleeve that slides up and down
> on the
> > rudder blade with the motor attached to it. Lift it clear of the
> water when
> > not in use with a block and tackle, ease the rope to lower it.
> Much cheaper
> > and more reliable than the African Cats system. Kicks up on
> impact and
> > very accessible for clearing ropes and stuff off the prop. Also
> (smug
> > grin) not usable by boats without beam mounted rudders.
> >
> > Another version is the e jet
> >
> > regards,
> > Rob
> >
> > On Thu, Apr 3, 2008 at 10:26 PM, chesapeake410 <chesapeake410@>
> > wrote:
> >
> > > Hello,
> > > I am planing on building a 12 m Harryproa and am thinking of using
> > > electric pods. Pods would be mounted on swing arms similar to what
> > > has been used on African cats. Take a look at the June 14,2007
> press
> > > release on website. Also check out RE-E-
> .
> > > In the Re-E-Power Forum link in the photo section is a example of
> a
> > > pod mounted to a long swing arm.
> > >
> > > Has anything been done with electric power on Harryproa's ? I
> think
> > > there was a recent reference to electric motors on rudders, does
> > > anyone have more information or pictures on this.
> > >
> > > I think a Harryproa would be unequally suited to a solar/battery
> > > electric drive system since the sail is offset on lw hull. A solar
> > > canopy over the seats a center area of boat would be less
> obstructed
> > > by sail than a cattermaran.
> > >
> > > The proa does have the problem of how to deal with going in both
> > > directions with the electric drive. You could point one in each
> > > direction and only use one in open water and lower both for
> > > maneuvering in harbor or for extra power when needed. You could
> use a
> > > prop designed for both directions but I do not know it it would
> be as
> > > efficient as one designed for one direction.
> > >
> > > I would like to hear any sugjestions and comments one this ?
> > >
> > > One other concern would be the added weight of a battery pack
> which
> > > could be as much as 1000lbs or more. I am hoping that newer
> battery
> > > types will bring down the weight in the next few years to less
> than
> > > 600 lbs.
> > > Valence Technology Lithium batteries would be great but the
> current
> > > price is prohibitive. Firerfly batteries (a new lighter type of
> lead
> > > acit battery) sound like a good bet but are not yet available. It
> > > may be necessary to start with current lead acid and switch to
> > > lighter batteries in the future. After Lithium batteries get
> > > established in electric cars that will start coming out in the
> next
> > > few years I expect availability and price to improve. I spoke with
> > > Bob Lutz vic chairman of General motors at a special event a the
> New
> > > York Auto show a week or two ago and he claims that they will have
> > > the Chevy Volt in production by the end of 2010 ! It will run on
> > > lithium batteries.
> > >
> > > Thanks for any imput on this topic,
> > >
> > > George Kuck
> > > Chestertown, MD
> > >
> > >
> > >
> >
> ---------------------------------
> You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access,
No Cost.

Recent Activity
Visit Your Group
Y!7 Toolbar

Get it Free!

easy 1-click access

to your groups.

Yahoo!7 Groups

Start a group

in 3 easy steps.

Connect with others.