Hi Anton,
I'm fairly familiar with the Wharram Pahi 42 design. I understand that you are thinking about creating rudders with built in drive pods, or maybe pods attached to the rudders. The biggest problem with drive pods is trying to keep operable while constantly submerged. There was a pod vendor that sold a number of pods that later failed from water intrusion. There might be other, more reliable brands, but they will probably be expensive. Because of the size of your boat, your motors should be fairly powerful and the rudder structure will need to be stronger than designed, I've heard of people successfully doing something similar on small boats, but not on a boat of your size.
Most electric conversions aim for about 1kW or drive power for each ton of displacement. You should consider loaded displacement for this calculation, so you're looking at 6.5-7kW of drive capability. Personally I would run two Torqeedo Cruise 4.0 motors on the Wharram style drive mounts, one near each hull. They will be easy to deploy, retract and you will be able to "power steer" with the seperate throttles. The two motors will cost about 20% of your conversion budget, $8000. Half throttle on both motors should move your boat at 4.5-5kts.
Moving on to the batteries, Torqeedo says that a 5.4kWh lithium battery will power a Cruise 4.0 for 3 hours. So 11kWh of batteries should give you a 15nm range at 5kts on batteries alone. I don't know what Lithium batteries cost in your part of the world, but at US prices, you would be able to buy 32 Thundersky LiFePO4 3.2V 100Ah cells for less than $4500. This would give you a 5.1kWh (51V x 100Ah), 60Kg battery bank in each hull. Your boat would have a 14nm+ range under battery power alone.
Since Wharram cats mostly operate in displacement mode, your sailing speeds are not going to average into where regen will produce significant power. I wouldn't plan on any regen, and if you get some, you can consider it a gift from the wind gods.
I would buy a shore power battery charger that could be wired to both banks (I would put in a switch on the charger output and charge the banks seperately). I use the Elcon PWC 2000+ charger that charges at 28A, it costs less than $1000. Throw in cabling, fuses and other miscellaneous hardware and we've spent about $15,000 so far.
Once you've built the Wharram motor mounts, the installation of everything mentioned so far, would take less than 2 days (many people could probably do it in less than 1 day).
Now all you need is the renewable energy stuff. It would take 2.5kW of solar panels to supply half of your 5kt cruising speed. This would extend the range of your batteries to 30nm (about 6 hours). Picking a random solar cell, the Samsung LPC244SM. 2 groups of 6 panels in a 2S-3P configuration might deliver 42A into your drives (21A per drive) during the peak of the day. Each panel is 1.65m x 1m and weighs 20Kg. So 12 panels would cover 20m2 and weigh 240Kg. US cost would be $7000. You'll need a charge controller. I would recommend an MPPT controller to maximize your charging. This type of charge controller can handle reduced voltage if part of your array is shadowed. I would budget $1000 to get a good controler with the proper LiFePO4 charging profile. Building an appropriate superstructure to carry the panels would be you biggest challenge so far. Your boat might be able to motor at about 4kts on solar alone in good conditions.
You could also consider wind generators. A $1000 Air-X wind genrator will produce 400W, but only when the wind is blowing 28+kts. In 12kts of wind the output is closer to 70W. In my opinion, wind turbines are not worth the noise, effort, or money. But you may feel differently.
Without the wind generators, this plan would come out to around $25,000 US.
Anyway, that's what I where I would start. I wish you the best in your conversion.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, harpitap <no_reply@...> wrote:
>
> Hi, my name is Anton and I joined some time ago, I am overwhelmed with information in this group. English is not my native language and I try to do my best. All my life I spent little to no attention to environmental problems/solutions.
>
> I am now the proud owner of a James Wharram Pahi 42 catamaran http://s1226.photobucket.com/home/harpitap/index
> specifications: (mine is actually 43ft)
>
> LOA (length overall): 12.8 m (42 ft)
> LWL (length at waterline): 10.36 m (34 ft)
> Beam: 6.7 m (22 ft)
> Draft minimum: 0.64 m (2 ft 1 in)
> Draft maximum (e.g. boards down): 1.07 m (3 ft 6 in)
> Windward sail area: 59.6 m² (642 ft²)
> Displacement, lightship (empty): 3500 kg (3.44 tons)
> Payload: 3000 kg (2.95 tons)
> Hullshape: V - V
>
> Installed is a 15hp Honda motor. After cleaning out the hulls I found about 10 empty cans of fuel and a nasty fuel stench in the storage room. All electric wiring had corrosion.
>
> After many days, thoughts, research and discussions I decided to make this a full green boat. Not only declining fossil fuels but also "non fossil fuels", that means no backup system. The boat will sail in Asia, mainly coast sailing and islandhopping so there will be enough sun and/or wind. I would like to keep this post on topic so I will not go in to details about cooking, toilet, air conditioning, hot and cold water, waste and drinking water.
>
> From the mast to the rear end is 5.5x6.5=35.75m2 available for solar panels, more if needed. The panels will be installed on a roof just under the boom. The booms shade on the panels is a problem for witch I have no solution. I have 6 Prevailer pv-27dc on board and I don't know if or how they could be set to use (thoughts?). As for the batterybank I was thinking LifePo4, as I understand are the safest.
> According to the building plans that came with the boat I think it is possible (after redesigning the rutter and mount) to install pod-motors build in the rutters and using foldable props, regenerating motors would be awesome. One or two wind-generators is optional.
>
> Requirements: the boat will sail in Asian waters using the motors for distances <30km, and sails for >30km. The desired trolling speed for motoring will be 5kn at 70%. 50 of these 70% must come directly from the panels thus draining the bank for 20%. this would give me theoretically 5hrs at 70% and unlimited 50% or am I making a mistake here?
>
> The budged for the panels, motors, controller, charger, transformer, wind-generators, battery bank is $40.000. This is not fixed but I have to set it somehow ;-)
> What setup do you suggest, what are the best pod-motors, battery, panel and what are your thoughts about this project?
>
> Anton
>
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