Welcome Gene,
In the Files section download the "Eboat Model Spreadsheet" (if you
don't have Excel, the free OpenOffice program will open it). Just enter
in your boat particulars and it will give you most of the data you need.
I did a quick run with your numbers and it suggests (eek) a 29" prop and
almost 30HP to drive it. Your boat is at the upper limit of what is
practical for a battery-electric drive - for even an hour of runtime it
looks like 48 T-105 Trojan batteries (as one example) - almost $6K in
batteries alone.
An alternate strategy which I would strongly recommend you look at is a
dual-drive setup. With a boat as large as yours it will be difficult to
provision everything within a reasonable amperage draw - you would have
to go very high voltage. A dual-drive (just like a trawler) would have
many benefits:
* reduced amperage
* Redundancy - run on 1 drive in case of failure
* Lower voltage (48V or 72V is recommended)
* Lower-cost components overall (more "off the shelf) items.
* Vectored thrust for steering/bow-
Since you seem the DIY type a kit such as provided by ThunderStruck EV
would work (2 actually). I would recommend going with a brushed ET-RT
motor which is larger, and also easier to use and troubleshoot than the
brushless motor they provide in the kit (so this would be semi-custom) -
so expect to pay ~$3K- $4K for the drive systems (complete except for
batteries basically). If you are going cruising spend 50% more and get
a complete spare to carry. Then there are tools, meters, cables, etc
which will all add to the overall price.
Adding 2 sterntubes and engine beds is probably not that much more work
than 1. But you could also go with bolt-on external "pod" type dr such
as Re-Epower provides. This would run you more but greatly simplify
installation. Somewhere in between are various turnkey kits which will
be simpler than complete DIY. One in particular to look at is Electric
Yachts setup:
http://www.electric
, 2 of these should set you up nicely, though I would caution you about
under-powering a boat of that size.
I provide some guidance on planning fcr installation etc on a site I
maintain (non-commercial)
http://sites.
pointers to suppliers and such in the resources section.
You'll also see there that I don't place much credit on regeneration - I
cite references and state my argument pretty directly. In a nutshell -
it doesn't really work well enough to contribute to your energy budget.
Other considerations:
If you are planning on carrying a generator anyway, you can plan for a
smaller battery bank. Or opt for a complete hybrid strategy such as
provided by Glacier Bay.
In any case, incorporate the weight of the batteries - which will be
considerable - into your plans. You can probably, with the help of a
naval architect, re-design the keel to accommodate the extra weight in
batteries, so long as they are properly placed and secured low in the
bilge.
(all companies mentioned are on my Resources page, and most are in the
Links area here as well).
Regards,
-Keith
--- In electricboats@
>
>
>
> As a new member I have questions that may have been discussed before
but are new to me.
>
> I am starting a new project to build in wood-epoxy a 42' Bruce
Roberts Spray (18 ton displacement with a 14.5' beam) sail boat to
cruise through retirement.
>
> I plan to use a Chinese freestanding lug rig and an electrical
auxiliary motor that will recharge while under sail. As I look at
various motor options I find their pricing all over the board and
limited data provided. A couple questions that I have for anyone who
has converted to an electric boat (particularly a sail boat):
>
> • My thinking is that a large prop with a high pitch turning slow
may be more efficient while under power and for recharging while under
sail. From your experience, how large should the prop be for a 42'
boat with 18 ton displacement?
> • What should the speed of the prop be?
> • What experience have you had with reduction gears or reduction
belt assemblies?
> • What are some good sources of reduction units (to add torque and
reduce speed from the motor to the prop)?
>
> Thank you,
>
> Gene
> Hood Canal
>
>
>
>
> ____________
> Hotmail® has ever-growing storage! Don't worry about storage
limits.
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