Subject: Re: [harryproa] Re: Electric drive for Harryproa
From: George Kuck
Date: 4/3/2008, 2:23 PM

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 continuously.  
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 <> 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.


--- In, "Rob Denney" <harryproa@...>
> G'day,
> Blind Date is getting an electric motor this winter. The 66'ter in
> 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
> 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
> 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
> > release on website. Also check out RE-E- .
> > In the Re-E-Power Forum link in the photo section is a example of
> > pod mounted to a long swing arm.
> >
> > Has anything been done with electric power on Harryproa's ? I
> > 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
> > 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
> > could be as much as 1000lbs or more. I am hoping that newer
> > types will bring down the weight in the next few years to less
> > 600 lbs.
> > Valence Technology Lithium batteries would be great but the
> > price is prohibitive. Firerfly batteries (a new lighter type of
> > 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
> > 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
> > 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
> >
> >
> >

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