Subject: [harryproa] Re: Electric Drive for Charter Proa
From: "jjtctaylor" <>
Date: 5/19/2008, 4:57 PM

Great points from ALL.... I have never been opposed to hydraulic
drive as they are very reliable, just the hassle of energy conversion
to power them. If already got a genset or other power generation,
just seems a waste to add another system. PTO off the the main
propulsion unit is very practical for hydraulics, just seems
counterproductive if main drive is hydraulics, but produced from
electrical, converted from diesel.

Certainly many can argue why not diesel as primary energy source and
no problem to add hyd or elec drive from that. Problem is sizing for
peak results in a lot fo extra weight and HP. Victron energy and
others take advantage of electric drives and battery storage to play
games with balance on silent batt power and the associated loads and
power types to harmonize demands with system sizing to minimize
weight overall. So best results come in medium to large battery
banks and smaller gensets. Optimized for peak loads and run
durations. All balanced with power supply, regen, solar and finally

One caveat from Rob and some others is you want to run at 8 knots
under power. Expect to need 10 - 20KW depending on final loaded
displacement. Electric drive can easily perform better than a much
larger diesel engine when moving the boat at 4-5 knots. When we push
the exponential increase in drive power, going past 7 knots then
electric will match the peak HP of the typical diesel inboard of a
similar displacement craft. Size your continuous power generation to
match or slow down ! African cats replied to me indicating they size
their capability to run flat out over 8 knots for an hour, but only
can run continuously at 75% of that.

Go fast and need a lot of HP/KW plus chew up a bunch of fuel.
Charters of Lagoon 420 elec. have not reported any fuel savings, with
electic drives, since they wanna go fast. Charter comments, they
like parking power and silent operation and as mentioned the premise
of "green" is important to some. Greener when they didn't use it all
and the charter proa is so fun to sail and shunt they lay off the aux
drive, right ? But charters are not making much dent in fuel cost
with regen.

I think at present the assumption is charter wants electric stuff
like AC cooling, refrig, and a whole bunch af "other" conveniences.
So given genset is required, why not size for modest speed electric
(7) knots, burst speed when needed. Sizing properly can save weight
while offering flexibility to push harder on occasion.

The comes the question AC or DC genset ?



--- In, "Robert" <cateran1949@...> wrote:
> -Though I agree that chartering the batteries are less likely to
> recharge under regeneration, and there is not a sufficient
> disincentive to not use fuel, this may not always be the case.
> It may get a different clientele who like the idea of having a
> tinge of green as they sail after jetting in from all over the
> Robert -- In, "Gardner Pomper"
> <gardner@> wrote:
> >
> > Hi,
> >
> > I have been following your posts on the forum and it is clear that
> you are
> > much more knowledgeable in boat building than I am, but I am not
> sure that I
> > agree that a hydraulic system is more complicated than the
> This
> > isn't so much from an engineering basis, but from living aboard a
> > (30') cat in the bahamas, and also owning a 37' one-tonne racing
> monohull
> > with a hydraulic drive. So, take my comments for what they are
> >
> > All the systems on our cat were operated off electric
> (refrigeration, radar,
> > etc) from 4 solar panels. We had gasoline outboards for mobility,
> but they
> > were pretty useless for charging the batteries. It operated well,
> until we
> > were hit by 3 rainy days in a row. We might have been ok if we
had a
> wind
> > generator, but there wasn't really all that much wind either. We
> to go
> > in to a marina to recharge. Since then, a generator to recharge
> > batteries has been right up at the top of the list of things to
> one a
> > boat. Running off solar/wind is great, but you know that you will
> run out of
> > electricity at some point. If you are using the electric for
> power,
> > you will have much greater reserves, but you will also use them up
> motoring
> > (charter delivery dates, plane dates, etc). Were I to have an
> "all-electric"
> > system, I would still need a genset, with its attendent fuel
> requirements.
> > And I believe, that the charter harryproa will have a genset. So,
> could we
> > not have an electric pump, pumping hydraulic to the submerged
> >
> > Perhaps that it too inefficient. My monohull sloop had a 60HP
> Perkings 4108
> > mounted under the V-berth (racing handicap, apparently) which ran
> back to a
> > hydraulic box on the propellor shaft. It would push the 16,000
> > monohull at about 8 knots in flat water.
> >
> > I am thinking that motoring a proa should not take that much
> If it
> > can run at 8 knots, that should be satisfactory. One would almost
> > that it could just be done with outboards (not that I approve of
> those; I
> > would really want diesel for any sustained motoring).
> >
> > Apart from fuel efficiency, (and lack of explosions), the main
> I would
> > want from an engine is quiet. Electric would give me that for
> periods,
> > but I am worried about the genset right up on the deck. It would
have to
> > really ruin the serenity.
> >
> > I guess what all this boils down to is that this proa design is a
> > radical new concept. Things are bound to go wrong. I would rather
> just keep
> > the engine systems simple and use all the engineering brilliance
on the
> > sailing platform. After all, it is a sailboat. The motors are
already a
> > fallback. They need to just work.
> >
> > - Gardner
> >
> >
> > On Sun, May 18, 2008 at 7:37 AM, jjtctaylor <jtaylor412@> wrote:
> >
> > > I thought it a good idea to make a separate topic while Rob
> Ron are
> > > discussing drive options.
> > >
> > > I agree the electric drives "in general" offer freedom of
> > > location. Electric can use battery power that is stored energy
> > > some duration depending on size of battery bank and speed
> > > Battery provides an extra level of safety as reliability is
very high
> > > and can be abused in emergency if genset doesn't start. I have
> > > personally on my own charter boat twice to lose all engine
> > >
> > > Problem is fuel in the tropics. Source in carib. is
> > > while biocides and such do not seem to keep the sludge under
> > > Charter fleets are not going to manage quality of fuel as you
or me
> > > will do it. Nor do they take time to purge tanks and thoroughly
> > > clean. So batteries provide a very handy energy backup to keep
> > > sailors going. Nothing worse than coming into a slip or crowded
> > > mooring field undersail alone. I've done it, but not fun.
> > >
> > > Recharging as a charter boat in the carib has a lot of input
from the
> > > Lagoon 420 thread in cruiser's forum. Bottom line, don't sail
> > > enough from point to point to give a full recharge. Going
upwind is
> > > full motor in most all situations for charter goers. Too much
> > > and schedules to get to next locale and beat the rest of the
> > > gangs is prime concern. You might say that sailing is
faster,.... The
> > > charter bunch are a point and shoot type. So while it takes 3
or more
> > > time to recharge than use you can see it is highly more likely
> > > genset will be needed to top off.
> > >
> > > Aside from weight, I don't see a huge advantage to go with
> > > Why add complexity and a system when not needed. I do agree
> > > engineering will be needed for cable type, and protection on any
> > > submerged motor. The 48V re-e-power type need bigger cables and
> > > protection than the higher voltage types like from African cats.
> > >
> > > In any event thought I would add this topic separate for
> > > input on options, mounting, control, size and type,...etc.
> > >
> > > JT
> > >
> > >
> > >
> >

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