Description
The TC Elotri 650 is an electric/solar powered, family, inland cruising, low drag, trimaran. The large social cockpit is protected by a lifting hard top, on which solar panels arte mounted to extend the boat’s range.

Inland boating.
Much boating is done inland, on canals, rivers, lakes and reservoirs. Many of these areas have speed and horsepower restrictions, and some now regulate to only allow electric engines. The sheltered nature of these areas, and the modern reality of people often having limited holiday time, means a great range is not needed. Enjoying quality time on the water, enjoying either the peace of nature, or gentle music from the stereo, without the noise and smell of an engine, is a priority though.

Hull shape/ Stability.
The hull shape is essentially a narrow, single chined mono hull, in which the chines evolve into an outrigger hull. This allows the entry angle at the bow can be much finer, reducing the bow wave considerably

At the stern the hull pinches in to provide a clean exit onto the propeller and rudder. Above this is flat to prevent the boat squatting at speed, and provide reserve buoyancy and water plane area as people board from the stern.

Being a trimaran the boat is naturally very stable. The cockpit floor is well clear of the water, so is self draining. The cockpit lockers are at this same height, and would be drained to the cockpit rather than straight down to the sea. As the boat heels, and trims down by the bow, the cockpit remains dry, so removing the flooding risk. The bench seating centralizes the crew weight.

Hard Top and Solar panels
The hard top when down seals the cockpit from the elements, and light fingered visitors. This means the squabs in the cockpit can remain in place, and items in the cockpit lockers are secure. It is raised by small servo motors on telescopic arms. This provides sun and rain shelter to the crew, who can fully enclose the cockpit with flexible PVC clear panels. The hard top has room for four 110w panels to charge the 24V battery bank. The forward solar panel can be slid aft to access the helm station when the top is down, so the boat can be manouvred under low bridges.

In cruising areas with more local wind than sun, such as UK or Europe, two of the solar panels could be substituted by a wind generator. This option would provide potentially 24 hour charging.

This charging capability is obviously an expensive part of the boat. To make the most of this costly investment, when at home, the boat could be plugged into the main house system of the owner, to help reduce the owner’s domestic electricity bill.

By lowering the hard top down, and having no permanent windscreen, the air drag of the Elotri is minimised. By using modern construction methods, towing weight is reduced, so that an average 2l car can tow the boat.

The hard top can be lowered, and the forward panel hinged aft, so the boat can be manoeuvred under low bridges.

Steering controls
The boat engine and steering would be controlled by a single joystick. In fact other than the charge meter, very few other controls would be needed. Of course compass, GPS, speed and depth could be added. But this boat is aimed for inland waterways where visual navigation should be easy.

The rudder would be controlled by a servo motor, as the boat is relying on electricity anyway for propulsion.

Cockpit.
The cockpit has bench seating all the way around. To port is the helm station facing forward, with a pivoting back rest to expand the social seating when at anchor.

The Starboard cockpit lockers raise vertically up to provide sink, bench space and galley storage when needed. A table folds down from the ceiling of the hard top, and detaching it and placing between the seats can provide a large extra double berth on deck. A barbecue cooker would be mounted aft.

The center seat at the rear can swing aft to provide a boarding ladder, and place to sit in the water to cool off. This feature also allows easy access to the boat when it is on the trailer.

A 24V portable fridge can be brought aboard and plugged in under the cockpit seats.

Accommodation.
Forward there is a large double berth with lots of shelf area surrounding it. Ventilation can be through the deck hatch, or though the anchor locker on wet days.

A private enclosed head is to port, with either a cassette toilet or marine toilet and holding tanks.

This allows for over-nighting in the boat, rather than just day trip use.

Trailer Options
This design could be trailed on a conventional boat trailer. Some countries regulations may not require brakes for the empty weight of the boat, but I would always recommend them as so often a boat going away gains a lot of weight in family food, beverages, clothes etc.

Being an electric boat there is an attraction in using regeneration of energy through braking, rather than friction brakes. Also a trailer adds more to the total trailer weight the car has to pull, and the structure of a boat is already strong, without needing further ‘backbone’. As well there is a cost and security risk of storing a trailer ashore when on holiday.

So a solution is to include the wheels into the hull, and make them retractable in the water. By using either an electric engine within the wheel hub, or a belt and shaft drive to an electric engine, braking can be done by generating more energy for the batteries. Also, when retrieving the boat up a steep ramp, or driving up hill, extra help by the electric wheel engines can assist the car.. Obviously any extra drive force cannot be so large so the trailer wants to overtake the car, but it can be computer regulated to assist, via the trailer coupling’s override system.

Remembering that many medium cars now are front wheel drive, this would have considerable benefit. Also, it seems a pity to own a large car for towing a boat for a few weekends a year, and having to pay for the extra petrol when not towing the boat of a large engine.

Extending this concept further, with the addition of a steer-able front wheel, the Elotri can be made amphibious. This removes the need to get the car near water, and gives options of driving the boat ashore to campgrounds besides canals or lakes. Also the draw bar could be attached to the front wheel, removing the draw bar weight from the rear of the car.

Construction.
The boat is designed with developable flat panel construction in mind. Possible the most long term environmentally friendly option is aluminium construction, as ultimately the boat could be recycled at the end of its life. However, as a designer I’m not as familiar with this medium as I am with composites.

For the home builder, or prototype, marine plywood fibreglassed over both inside and out is an option. The structure naturally grids up the boat, so 4-6mm plywood would be all that was required. Having made 4mm stressed plywood boats this can be very effective. (See the TC 790 Hard Drive)

Also for one off construction epoxy foam and fiberglass could be used, to produce the lightest, most durable boat.

Shaping the PVC foam or plywood for each panel, then glassing the inside skin before attaching it to male frames would be relatively straightforward. Then the entire outside skin can be applied. Many of the permanent inside frames would be coved and taped (on one side) to the inside of the boat while still on the frames. When the frames are removed, the hull seams can be (double bias) taped together.

The deck would be made in a similar fashion, and attached at the sheer line.

Really though the design would be ideally produced in a female mould in polyester, with foam core in the larger side and deck panels. Attention to detail and weight would be needed here to maintain the boats light weight advantages. Any production boat builders interested in producing this boat should contact me on email: tcdesign@xtra.co.nz

Markets:
The purpose of this boat is for family and friends to have fun on the water. The technical innovations of hull and propulsion just provide a vehicle for this. Primarily the boat is aimed at inland, recreational family boating.

The boat is aimed at the Inland boating of the USA, particularly California and Arizona, which have many inland lakes and waterways, and plenty of sunshine. There electric boating is already well established.

The United Kingdom has a wonderful array of canals to explore. But with reduced beam restrictions for both afloat and on the road, this design may need to be modified for this market.

In Europe there is an extensive canal network, especially in Holland, Belgium and France. Also people typically have small to medium engine cars. So this design should appeal there too, possibly with slightly more conservative aesthetic changes (this is being developed in the Netherlands and will be released as the Featherline Range, see www.featherline.nl ). Here the option of wind generation would be explored further.

In New Zealand (my home country) there are many inland lakes in the Central North Island (Rotorua region) and South Island where this design would appeal.

Primarily the boat is aimed at recreational family boating. This could extend to bird watching, fishing or as a diving platform. Commercial use could include use as a canal water taxi, or entertaining on the water

As an amphibian, it would have use as a rescue boat in area or towns after flooding, as the propeller is well protected, and it could cruise with the wheels down in shallow areas.

Summary
Currently many existing electric boats are relatively wide and heavy boats for their length, consequently they have high wave making drag at low speed. By using the trimarans hull form, in conjunction with light weight construction influenced from racing yachts, the entry angle at the bow can be much finer, reducing the bow wave considerably. As the hulls are fine displacement forms, there is no planning speed ‘hump’ at canal speed of 5-6 knots, so a small engine can push the boat efficiently. The hull platform also allows for a wide boat on deck, and so improving room for its length. The lifting hard top provides sun and rain protection, and when lowered minimises the air drag of the boat on the road. By including a private head and double berth below, the boat can be used as a weekender. And the solar panels can be put to use at home, as well as on the water.

In summary, we have an ‘Elegant Efficient Boat’.

Competition
This design is an entrant in the RINA Concept Boat Competition. This is an expanded extract from that design entry.

Tim Clissold
© TC Design Ltd