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Windmill Boat Proposal

16' HobieCat with experimental windmill rig. Developer, retired physics professor Brad Blackford at the controls. Location: Armdale Yacht Club, Halifax, Nova Scotia.

Test boat underway on a reach.

Proposed 36' windmill powered catamaran for coastal cruising.

We are seeking to assemble a consortium of designers, builders and sponsor(s) to construct and test a windmill powered, coastal-cruising vessel. The aim is to demonstrate that a windmill powered craft is a viable concept for a coastal cruiser. At the end of the experiment, we intend to sell the design, design experience and the boat to an interested party or parties.

A number of windmill powered boats have been built over the years, with varying degrees of success. Some of the smaller ones were built from scratch, larger ones were converted production boats. However, the idea has not caught on beyond a few amateur one-off designs.
Why build a windmill powered boat?

· The main advantage of a windmill boat is its ability to "sail" in any direction, regardless of wind direction. Because it is never necessary to tack, this ability can make it a long distance performer. Therefore, a moderate-speed boat can outperform a speedier counterpart. Further, they can be effortlessly maneuvered in tight quarters where winds are not fair. This would include rivers, estuaries, narrow lakes and shoal infested areas.

· The windmill boat has many of the advantages of the power boat without noise, pollution and the high (and ever rising) cost of fuel and engine maintenance.

There is a potential market out there for an enterprising boat builder.

· Technophiles intrigued by the very idea of ?sailing? directly up wind.

· Technophiles who have to be the ?first one on the block? to posses a new product.

· Persons who want the advantages of a power boat without the expense of fuel, the noise, maintenance and pollution . It?s a ?Green Machine?.

· Persons who navigate waters that are not conducive to safe or comfortable sailing in the usual sense. E.g., a long narrow lake where the wind blows only up and down the lake.

· Ecotourism operators who can offer ?naturally powered? touring experiences. An unusual hook for potential customers.

· Environmental or other scientific researchers navigating waters in a manner that causes minimal disruption and pollution.

· There may even be a potential for a separate racing class. There will be ample opportunity for competitors to fine tune their rigs for optimal performance (One can imagine the need for special rules to keep a safe distance from one another.)

Our test boat, a 16' Hobie Cat, achieves a speed of 50% to 60% of the relative wind, at just about equal speed, in any direction. Speeds up to 10 knots have been achieved so far.

The windmill drive has been proven to work. Our principle challenge will be to develop a simple, robust and efficient drive train that is easy to use and maintain. It must be strong enough to stand up to rough marine conditions. However, this should not be too difficult using normal engineering principles.

What makes this design unique is that the windmill blades together with the rest of the drive train have been developed to produce maximum net forward force.

(See references in Appendix A)

A principle concern with the windmill is safety. For obvious reasons the wind propeller must be kept from contacting passengers, other boats, wharves, etc. A catamaran has been chosen to keep the propeller blades from touching water while rolling. It's imperative that the deck, accommodation layout and access to emergency equipment be such that passengers and crew do not inadvertently come in contact with the rig underway. For this reason the rig will have limited appeal but for some cruisers it will serve well indeed.

A second concern is protection of the water propeller in the event of grounding since there is no keel. Grounding is inevitable while cruising. In the 16? prototype, the prop is incorporated in a large, tiltable skeg/rudder.

Required is a boat design that will go easily and safely, directly upwind without excessive pitching or burying, in reasonable comfort.

The catamaran is somewhat less expensive than a trimaran and has a bit more directional stability going downwind

With our prototype we wish to demonstrate that the concept can fill a niche among cruising designs. Once the concept has been made to work the boat could be sold as is, finished out and sold or kept for further experiments.

Proposed Specifications: (this is a work in progress and is by no means final)

Hull Type: Wave piercing catamaran.

Size: 36?0? LOA; 16?5?' Beam; 7?4? Draft; 2900 lb. Displacement Hulls approx. 2'2" wide over much of their length. (The hulls are long, narrow and more or less parallel sided. Cabins with sitting headroom with overhanging extensions inboard.

Material: Wood epoxy ply hulls, sheathed in fiberglass, stitch-and-tape construction. (Future hulls could be built in fiberglass, for example.)

Crossbeams and other fixtures: laminated wood epoxy.

Propulsion: Single, mast mounted astern, three blade, horizontal axis, variable pitch windmill, driving a two bladed, high aspect ratio water propeller (possibly variable pitch) incorporated into a rudder/skeg assembly designed to tilt forward. The forward tilting configuration accomplishes several purposes. (For inspection access, maintenance, freeing debris and in case of grounding.)

Wind Propeller Construction: three blades, carbon fiber over foam core. This is Brad Blackford?s unique contribution, a blade designed for optimal net forward force through the whole range of wind directions.

Water propeller Construction: two cast bronze blades, or carbon fiber.
Variable pitch control being considered.

Accommodation: Minimal but developable later.

Appendix A


"Windmill Thrusters: A Comparison of Theory and Experiment",
Journal of Wind Engineering and Industrial Aerodynamics, 20(1985) 267-281

"Optimal Blade Design for Windmill Boats and Vehicles",
Journal of Ship Research, Vol.29, No.2, June 1985, pp. 139-149

"The Physics of a Push-Me Pull-You Boat", Am.J.Phys.,Vol.46,No.10,
Oct.1978, pp.1004-6

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Gerald K. Limber
Asheboro, NC