| Winsome - Watercraft Sept/Oct 2005 |
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banks of the Monmouthshire and Brecon Canal, through miles of beautiful hill country and past some fine pubs. It’s too narrow for sailing or rowing; you need a motorboat or a canoe and these are either big and noisy, or wet and hard work. What they wanted was a selfpropelled boat to cruise the length of the canal or just nip along to the pub for an evening drink. Knowing we had experimented with a pedal-powered ocean-going boat, they approached us with a wish list: • No engine – must be silent and environmentally friendly. • Transportable to and from, into and out of, the water. • Dry to use and to get on and off. • No skill required to operate and able to cruise at the 4mph canal speed limit for the same effort as walking. • Good looking. • Hands free to eat, drink, read or play the saxophone • Able to be carried or wheeled around flights of locks • Plenty of storage space for food, drink, luggage and tent I agreed to take a look but immediately enlisted their help on the project. A friend introduced us to David Williams of Norfolk who had designed and built two pedal powered canoes for his own use – see W22 – the first over 40 years ago! David generously offered the team a trial run and the benefit of his experience in developing and using these boats over the years. One trip on the Norfolk Broads and everyone was hooked; with David’s advice and encouragement, the pedal skiff project was on! In principle, David Williams had done the spade work and all we had to do was to refine the ideas for production. The naval architecture seemed simple enough and bike parts are fairly standard, as are prop shafts and props. Granted a 90˚ bevel gearbox was unfamiliar but a quick search on the Web located several suppliers of off-the-shelf units. Eighteen months later, we were glad that at least we ’d been right about the bike parts! On the positive side, as each problem has arisen, we have found highly skilled engineers willing to help, experts in everything from the bike to submarine design. Everyone has been intrigued by the concept and we would not have got here without their freely-offered help and encouragement. Our 3 main challenges were interrelated:- • Efficiently transmitting the modest power to the prop • Designing a hull that was stable yet easily driven and light • The ergonomics of seat and pedal comfort Efficient transmission Two fit people pedalling hard generate about 400 watts of power between them. Our potential customers are not necessarily fit and may not wish to exhaust themselves so we gave ourselves a power budget of about 250 watts, which two normal people can maintain indefinitely. But what might be a tolerable loss for a 10 HP (7.5KW) engine could easily soak up most of the power of a 250 watt motor. Standard prop shafts, gearboxes and seals generate far too much drag; the gearbox in particular was a major problem. To transmit the relatively high torque input of two people through a standard gearbox used up almost half our power budget simply to turn the box. In desperation, we consulted a local quad bike specialist to see if a differential unit could be cannibalised to suit. He dismissed the idea completely but suggested we visit The Engineer just down the road. The Engineer turned out to be everything we needed, from casting to gear cutting and fortunately, he was as fascinated by the project as we were. In this part of Wales, there are so many skilled people hidden in the undergrowth that we could build a nuclear power station locally if only we could find them. Equipped for woodwork and remembering that lignum vitae was once used as bearing material on ship propellers, we tried this hardest of timbers but discovered it did not like drying out between runs. So we settled on a 16mm diameter stainless steel tube with synthetic bearings, with a simple spring loaded lip seal, which has worked well. The gearbox and propeller also worked well and we were delighted with the performance of the boat: 6.5 knots going hard at it and a very relaxing 3.5 knots with a cold drink in your hand. Unfortunately, the ladies said the gearbox was a bit noisy. There are three ways to make quiet gears: • Precision grinding – expensive. • Use hypoid gears – also expensive • Use plastic gears – which David Williams tried, found they only lasted a year and so ended up with hypoid gears. But, as we had now come to expect from rural Wales, we found a truly world-class gear expert who suggested that some new plastic gears with a patented tooth form might suit and would be easier to fit than bevel gears. So far they have run perfectly and are very quiet. We have to test their longterm durability but we now think that the drive train is sorted. Phew! Hull and propeller design There were two challenges in the hull and propeller design: • The hull had to be inherently more stable than, say, a canoe or rowing boat since it wouldn’t have the active stabilisation of oars or paddles. • The propeller had to operate at optimum efficiency in relation to the hull and the rate at which people pedal. We opted early on for a slipper launch shape, with a nearly flat bottom for stability and relatively high sides for large angle stability in a seaway. This gave good flow to the prop and to minimise drag, we decided on an open shaft with a bearing in the rudder post. The rudder post had to be very strong to protect the prop on grounding, so the addition of a bearing seemed obvious. Early prop calculations called for a prop of about 12” (0.3m) diameter, with a pitch between 12” and 18” (0.3- 4.5m). We couldn’t establish the dimensions entirely on paper because of the fairly wide errors in the resistance calculations and because of doubts on the optimum pedal rate. Cycling literature recommends at least 60 RPM at the pedals and preferably more but David Williams had found a lower rate more acceptable in his boats. As a quick and cheap development, we made some simple jigs to smith the props out of aluminium sheet welded to a central hub and made a variety of 2- and 3-bladed props for trials. The open prop shaft worked well hydrodynamically but proved to be a ruthlessly efficient weed collector; the smallest weed on the prop quickly increases the required pedal force alarmingly. The Teifi estuary grows a particularly sticky seaweed and we found that the bare rotating shaft collected this like spaghetti on a fork. So we changed the design to an enclosed shaft and did away with the forward skeg and replaced it with a small dagger-board, which improves the turning circle and makes it easier to turn through strong crosswinds. The hull itself was the one bit we got about right first time. The constraints of ‘roof-racking’ limited hull length to about 16-17’ (4.9-5.2m), while the requirement for low drag and stability suggested a beam of 3’6” (1.07m). The overall result is surprisingly stable and leaves very little wake even at 6.5 knots. Construction of the prototype is stitch and glue plywood but the final version will be in GRP, with slightly reduced freeboard – and increased sheer – with a rounded off deck edge to make a lighter but stronger hull. Seat and pedal comfort This was a new area for us but the ergonomics of the seat and pedal have proved just as fascinating as the rest of this project. The critical factors appear to be pedal height and seat height/rake. The seat needs to be as low as possible for stability, while pedal height is fixed by the crank diameter and the need for clearance between your heels and the bottom of the boat. To minimise seat height, we rigged up an infinitely adjustable three-part seat and experimented endlessly with angles, heights and distances from the pedals. Most people find our prototype seats comfortable but they are too expensive for regular production and in hot weather, a ventilated seat might be preferable. We experimented over many months with different people’s preferred pedal rate or cadence. There doesn’t seem to be a single ideal solution. Some prefer a slow hard push but most like a lighter one at about 50 revs per minute, while pro cyclists argue for 80rpm or so. Our solution? The production boat will come with three sprocket sizes so that the gear ratio can be changed to suit individual taste. Cost issues Our original target was a boat that would sell for about £3,000. But unsurprisingly, things haven’t quite worked out this well. To meet our weight goals, the hull needs to be a sandwich moulding which, while very strong and stiff, is also more expensive. The silent plastic gears are three times the price of our prototype metal gears and though the seat design has yet to be finalised, recumbent bicycle seats seem to cost over £80 each. The bottom line is that the initial production boats will sell for nearer £4,000. This means that Winsome cannot be considered an alternative to a canoe! Fortunately, early customer exposure suggests that a small percentage of boat owners and walkers try ‘Winsoming’ once and fall in love with the concept. So, we are slowly gathering a small trickle of Winsome converts who may be willing to pay the price for her unique – and hard won – combination of elegance and engineering innovation. So far, over 100 people of all ages have tried Winsome, on estuaries, canals, the Broads and the Thames, not forgetting the queue of ladies from Water Craft who wanted a go at Beale Park. Nearly everyone comments on how fast she goes, with how little effort and the enjoyable conversations they have as they cruised along. Other comments include: “We had a great time and it was the longest conversation I’ve had with my daughter since she got her iPod” and “[This is the boat] for middle-aged couples who still like each other.” EVALUATING THE PROTOTYPE They say the engineering graduate asks: Can it work better? The design graduate asks: Can it look better? And the arts graduate asks: Can I get you extra fries with that? Is that why Emily Mansfield volunteered to test Winsome? Ihad always assumed that pedal-powered boats were only for the bikini-clad holiday-makers who invade Greece in the summer; a splashy and inefficient means of trundling around on sun-sparkled water which only seems a good idea after one too many martinis. As a consequence, the notion of taking out a glorified pedalo, presumably made of fluorescent pink plastic, amidst the beautifully varnished Thames launches at Henley seemed to present enormous potential for embarrassment. When I saw the boat in question, I found my reservations were entirely unnecessary. With her dark green hull and a silhouette comparable to those of the classic riverboats around her, Winsome easily lived up to their standard of elegance. Indeed, when it came to attracting interested and admiring glances, both for her graceful lines and her novel means of propulsion, she was almost too successful. It seemed everyone wanted to try her out, from canoeists who sensed a fundamental similarity of aim, to ladies reclining in opulent motor launches who saw a novel and entertaining way of getting some exercise, and kids who relished the potential for speed. Winsome’s secret seemed to be the combination of an activity which looked fundamentally enjoyable, with enough style that she did not seem out of place cruising along beside the black-tie riverside concerts of the Henley music festival. The smoothness of the pedal mechanism means that Winsome is practically silent and my friend Claire and I found that with minimal effort, we could keep up with, even overtake, motorboats and electric launches – and it’s even more satisfying when you are supplying your own propulsion. While a small boat is an attractive alternative to the gym, and pedalling Winsome for any significant length of time is surely good exercise, I was taken aback by how little exertion was needed to maintain quite a fair speed. Indeed, everyone who has a go is struck by how much easier it is than it looks. Unlike her pink plastic predecessors, she is very efficient, mainly due to the use of a gearbox and propeller instead of paddlewheels, which allow her to glide along quite happily at an optimum speed of 4 knots. Allied to the fact that pedalling is a skill everyone has, this effortlessness makes Winsome a very democratic boat, not calling for the technical elitism of sailing or the fitness levels of rowing, and so quite accessible even for someone who has never been afloat under their own steam before. The cushioned seats and their sociable orientation make Winsome ideal for picnicking as well as pedalling and the slightly strange sensation of having both hands free while propelling yourself along seems to ask for the decadence of champagne and strawberries, at least in the glamorous surroundings of the Henley festival. Under more normal circumstances, one can hold binoculars or a camera, or even a cup of tea, and it does not take long to become accustomed to the level of relaxation you can attain, as you lean back and prop your elbows on the gunwale as if in an armchair. That said, the backrests serve a highly practical purpose of giving firm lower back support and so allowing you to invest considerable power in pushing the pedals, should you fancy higher-octane exercise. If this is the case, there is also the option of a higher gear, which can be set before heading out, allowing Winsome to reach her top speed of about 6mph. Winsome is very manoeuvrable, as the rudder is located immediately behind the propeller where it will be most affected by the wash and she also has the advantage of a reverse gear achieved by back-pedalling, which can be handy in a tight situation. In addition, her flat bottom gives a low centre of gravity which makes her feel safe and stable. So stable, we found it was even possible to carry two passengers, one at either end, sitting on the decks; in fact, Swallowboats goes so far as to boast that you can sit on the gunwale and she will not tip. Perhaps if she was 18-20” (0.5m) longer, there would be room for a passenger sitting at the same level as the people pedalling, which could make her more of a family boat – although the length she is now is convenient because she can be carried on a car roof-rack. Alternatively, it might be nice to have both pedallers facing in the same direction, so they can both see where they’re going. Another idea might be to widen the boat so that people could sit side by side, two facing forwards and two backwards, making her more sociable. I think that Winsome might be prettier and the front person feel more involved with the surroundings if the freeboard were slightly lower. These are not criticisms so much as ideas stimulated by the fun we had with her and a considerable advantage of the present version is the relative simplicity with which the concept has been translated into practical terms. Removing the pedal mechanism and seats to leave just the hull for ease of transportation is a straightforward procedure, leaving her light enough to be carried by two people and even hoisted onto a roof-rack. Once situated near water all that is needed is the dagger-board if it is windy, and the cushions, making her ideal for spontaneous trips. She can be pedalled quite satisfactorily by only one person and the GRP version now being developed will make her even lighter, facilitating launching. Even so she will remain environmentally friendly. Pedalling back from the concert, overtaking all the boats around us and knowing that the river was ours to explore in the morning, I was convinced. CONTACT Swallowboats Ltd, Nant-y-Ferwig, Gwbert Road, Cardigan, Wales SA43 1PN. Tel: +44 (0)1239 615140 www.swallowboats.com Winsome Specification LOA: 17’ (5.2m) LWL: 17’ (5.2m) Beam: 3’6” (1.07m) Draft: 1’2” (0.36m) Hull weight ex-pedal unit: 110lbs (50kg)
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