I have to agree with you 100% on all your points. I think the idea is enough batteries to
run some, in/out of harbor and some distance, thereby minimize genset start, plus reduce
size of genset for handling only long peak high demand loads. Spread out genset runs for
the shorter duration peak loads, while using batteries. It is a balancing act to not oversize
either but maximize battery capability to handle shorter peak loads.
PLus depending on power type, AC Vs DC. can make the genset additive to battery supply,
when load is very high, avoiding annoying circuit breaker faults. Charter goers not good
at troubleshooting tripped breakers nor do we want them to.
I too don't like the rudder mount as cables are too exposed. Prefer the flip down strut off
the LW hull.
All we have found so far on rim drive is at http://www.e-
Multiple requests from several forum members and no answers yet. Think they have
issues. I am not sure they are equally effective both directions. THey have tip deflectors
that seem to be direction dependent. These are sized for our application so maybe a
breakthru. Waiting for them to be more forthcoming.
I personally think electric is a good solution for a proa application, just have to resolve
best implementation and be clear on wants versus must have for short runs or sustained
cruising speed. Heat is a big problem, both in the controller for high amp systems and in
the motor itself. They will either self-regulate or shut you down until cooled. Have to dig
into vendor claims to find out what will happen and under what conditions. Run
longer/faster in cold temps than in the carib.
No free lunch on anything, just what balance seems to work best for you.
ON my HP, 3-4T loaded, will go with one 8KW motor. 10KW genset DC, 7.7KW NILAR
NiMh batteries. Cruise at 75% capacity, about 7 knots, for an hour on battery alone. 5
knots for 2-3 hours. NiMh good for fast regen and high amp output. Does have a little
daily loss. Weight for all, 100 lbs motor & mount, 310 lbs, batteries, 350 lbs on genset.
Add Ac/DC battery chargers and inverters to suit. Thinking on going all electric, no
propane.
Victron has nice mulitvolt battery charger. TDI has some nice lightweight inverters used
primarily in the telecom and military market, see their LCE series.
http://www.tdipower
Just some ideas, hope others have some more to pool our collective plans into the best
solution.
JT
--- In harryproa@yahoogrou
>
> This discussion has prompted me to look more at the electric motors
> that are available. I think my main objections are the idea that you
> can just carry enough batteries to not use the generator to motor the
> boat, and the flexing of the electric cables on the lift and tilt rudders.
>
> I also ran across the "rim driven electric propellors" used as
> thrusters for large ships and some discussions of how they might be
> used for propulsion. They seem appropriate for a proa, because they
> should be able to drive equally in either direction, so they would not
> have to swivel around they way a regular prop does. Is there someone
> in the forum who knows more about them? Like what a small one would
> cost? And whether they can really be reversed? The motor can, I am
> sure, but will the props work equally well in both directions.
>
> - Gardner
>
>
> --- In harryproa@yahoogrou
> >
> > 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
> > genset.
> >
> > 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 ?
> >
> > Regards,
> >
> > JT
> >
> > --- In harryproa@yahoogrou
> > >
> > > -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
> > slight
> > > tinge of green as they sail after jetting in from all over the
> > world.
> > > Robert -- In harryproa@yahoogrou
> > > <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
> > electric.
> > > This
> > > > isn't so much from an engineering basis, but from living aboard a
> > small
> > > > (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
> > worth.
> > > >
> > > > 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
> > had
> > > to go
> > > > in to a marina to recharge. Since then, a generator to recharge
> > the
> > > > batteries has been right up at the top of the list of things to
> > have
> > > 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
> > motive
> > > 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
> > motor?
> > > >
> > > > 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
> > pound
> > > > monohull at about 8 knots in flat water.
> > > >
> > > > I am thinking that motoring a proa should not take that much
> > power.
> > > If it
> > > > can run at 8 knots, that should be satisfactory. One would almost
> > expect
> > > > 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
> > thing
> > > I would
> > > > want from an engine is quiet. Electric would give me that for
> > short
> > > 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
> > pretty
> > > > 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@
> > > >
> > > > > I thought it a good idea to make a separate topic while Rob
> > and
> > > Ron are
> > > > > discussing drive options.
> > > > >
> > > > > I agree the electric drives "in general" offer freedom of
> > installtion
> > > > > location. Electric can use battery power that is stored energy
> > for
> > > > > some duration depending on size of battery bank and speed
> > desired.
> > > > > 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
> > power.
> > > > >
> > > > > Problem is fuel in the tropics. Source in carib. is
> > questionable,
> > > > > while biocides and such do not seem to keep the sludge under
> > control.
> > > > > 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
> > charter
> > > > > 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
> > long
> > > > > enough from point to point to give a full recharge. Going
> > upwind is
> > > > > full motor in most all situations for charter goers. Too much
> > hassle
> > > > > and schedules to get to next locale and beat the rest of the
> > charter
> > > > > 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
> > the
> > > > > genset will be needed to top off.
> > > > >
> > > > > Aside from weight, I don't see a huge advantage to go with
> > hydraulic.
> > > > > 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
> > everyone's
> > > > > input on options, mounting, control, size and type,...etc.
> > > > >
> > > > > JT
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
>
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