John,
It is obvious that you have done your homework and have thought
deeply and practically of the issues. Short of super cooled super
conductors or heavy weight copper cables the more compact the
better. Possibly the extra height of the centre of mass of the
batteries could encourage hobby horsing against low down central in
the lw hull. There is heaps of righting stability so resistance to
hobby horsing giving greater comfort and allowing the boat to be
driven harder as well as giving cleaner flow over the sails and
therefore better drive to drag on the sails may be more important for
driving to windward than the extra stability. It would also be less
strain on the boat overall while punching slop.
Taking this concept to the extreme, I came to thinking of a deep
pod like a submarine to actually sit under the water with a slim
access conning tower. The whole structure sitting just to ww of
centre, centre of mass sitting at centre of bouyancy. Maybe even go
the whole hog and have electrically operated stabilising hydrofoils
coupled to sensors on the bows. Unfortunately, it would probably be a
nightmare for maintenance and extra skin friction for low speed
sailing.

Robert



--- In harryproa@..., "jjtctaylor" <jtaylor412@c...>
wrote:
> Robert,
>
> Of course you can always put batteries in an optimal location.
> But optimization has "some" considerations. Outboard is where
> we live so they take up space. Since they are a "huge" power
> bank they have to be connected into your power plan. Electric
> drives take a lot of current so the farther away the batteries, the
> more power losss there will be in the cables plus the cables
> themselves are large gage which also adds weight.
>
> If you want to add other "systems" to make best use of this bank
> of power then they too should be near the source. Inverters,
> generators, distribution panels all find favor being closer to the
> batteries. All may be something you add later, but they need
> space.
>
> The weight of this bank of batteries does give the designer
> flexibility to insure fore-aft balance is mantained. They don't
> change weight like water tanks and the sizeable mass can be
> moved about some to get the bows level on final install.
>
> Lastly a final "big" consideration is how far can the electric
motor
> controller be distant from the electric outboards. The motor
> controllers handle the current to drives. They should be close to
> the motors and not too far from the batteries. Solomon drives
> require the motor controller to be not farther than 6 feet. All
> controllers are susceptable to noice interference and are best
> kept close to the drives. Even your HF radio can wreak havoc on
> an electric drive.
>
> I know the "best" weight location is the windward pod. My electric
> drive will be close to the LW side and works for me to keep all
> those systems in the LW hull. The current Visionnary under
> construction in Australia has two drives located near the WW
> hull. So with that arrangement if you can spare the space then
> the WW hull could be a good choice. I agree drippy is bad but
> space on the WW side remains an issue unless we add some.
> And you are correct they have to be somewhat central to prevent
> hobby-horse.
>
> REgards,
>
> JT
>
>
> --- In harryproa@..., "Robert"
> <cateran1949@y...> wrote:
> > -Could the 200 odd kg of batteries and the drive be kept in a
> pod ,
> > keeping the weight more outboard and the centre of drive more
> central
> > and keeping the electricity well clear of any dripping masts.--
In
> > harryproa@..., "jjtctaylor" <jtaylor412@c...>
> wrote:
> > > Hi ya Col.........
> > >
> > > I have known about ETEK for over a year. After doing a bunch
> of
> > > digging found out they have about half the torque at max
> output,
> > > as a Solomon ST-37. Yes they are going to heat up a bunch
> > > trying to overprop an ETEK. In addition they run at 3600 rpm
> and
> > > have to be geared down to something useable. They are
> rated
> > > at 6HP but only at max rpm, the torque ramps like a fuel
> powered
> > > engine so they lack grunt power a low speed.
> > >
> > > The big weight is not the engine (motor) but the batteries.
> The
> > > motors are not more efficient so watts consumed is the
> same as
> > > supplied by the batteries, no matter whose motor it is. Want
> to
> > > drive a Visionarry boat at 10 knots, it will take about 3-4KW
> per
> > > hour. Battery banks have to be at least double that size
> cause
> > > current released drops significantly after 50% capacity is
> spent,
> > > plus it isn't good for the batteries. So you will need at
least
> > 6KW
> > > in batteries, just to run an hour. A 60lb battery supplies
about
> > > 1KW. You will need not less than 6 to run an hour.
> > >
> > > Doesn't matter 48V, 60V or 144V, you still need that kind of
> > > capacity to drive the boat. I would not have anything less
> cause
> > > you never know when going fast is needed.
> > >
> > > Not sure ETEK is sufficiently marinized. Need to know if it
> will
> > > run if soaked (immersed) in salt water. Overheat is a real
> issue
> > > so not sure how the ventilation is handled.
> > >
> > > Granted the motor is cheaper, but life is full of choices and
> > risks.
> > > Have not seen the ETEK commercially used anywhere
> except
> > > lake outboards. I wouldn't give up on 'em but wait till Myles
> has
> > > the issues resolved and you are prepared to accept the
> battery
> > > mass required. Lots of folks complain bitterly about anemic
> > > outboards, don't want to have anemic electric outboards.
> Happy
> > > peppy boating sure beats a drifter.
> > >
> > > Regards,
> > >
> > > JT
> > > > >
> > > > Hi John,
> > > >
> > > > Have you considered a couple of Etek motors instead of
> the
> > > Solomon
> > > > solution?
> > > > The advantages as I see them are:
> > > >
> > > > -Less weight
> > > >
> > > > -Similar power (if a cooling cowl with fan is employed)-
> > > > see Myles Twete's site,mentioned at-
> > > >
> http://groups.yahoo.com/group/electricboats/message/2478
> > > >
> > > > -Better manoeverability - able to "turn on a dime"
> > > >
> > > > -Less cost (much less) - a spare motor could even be
> included
> > > >
> > > > You could still drive 16" propellors if you used a 4:1
> gearbox,
> > or
> > > > equivalent pulleys.
> > > >
> > > > Regards,
> > > >
> > > > Col Campey