A design from start to finish

Gavin Atkin moved house. The length of his new garage would enable him to build boats up to about 13 ft long; he is famous for one sheet (2440 x 1220 mm plywood) boats. Don Elliott sang the praises of an 8ft cruiser with fully closed in but awfully claustrophobic cabin, Stuart of Maximum Exposure fame made a disastrous start to his attempt to sail single-handed around Great Britain, a friend of mine bewailed the amount of time and money needed to build something which he could cruise for a month or so, I found that high strength carbon fibre and /or fibreglass tubes are getting pretty cheap.

My wife Denny and I spent a week out on Lake Hachure in a very small centreboard cabin yacht with just about room to take a deep breath without bursting the cabin at the seams. I read yet another song of praise about Bolgers “Micro” cruiser, I wondered about Bill Serjeant's Micro Cruiser site which did not seem to be picking up as much support as it deserved and I was bored with the boats that customers demands had me detailing on my drawing board.

All of these are related.

Rather like the disparate elements that go to make up a good soup, they simmered and gurgled in the back of my mind, surfacing to ask the occasional question then blending into the background noise again. How much room does it take to lie down? How much space does a months stores take if the boat can be resupplied with water once a week? What is the minimum height in which an average European male can sit upright? What sort of hull form could carry a really decent weight on a length that would fit into Gavin’s garage? How can a boat that would suit all of the other parameters be made to have the smallest possible range of stability inverted? What could be done to make her able to be reefed in a seaway, and hove to, where would the cooking stove go, the dry clothes --- and so on.

Some designs seem to have a life of their own!

Shreds of evidence disappear into my mind, the mix ferments and eventually the pressure gets so great that there is nothing for it but to download the result through my pen. So, here are the results!

Length, a 15ft (4.5 m) long building space could accommodate a boat about 13 and a little bit feet (4 m) long and still allow the builder to get around the ends with the doors shut.

Imagine being up at the head of a deserted estuary, stuck there waiting out a couple of rainy days! I refuse to lock my customer in a tiny coffin like space for shelter so sitting headroom and adequate light for reading is a minimum. This means we need about 2m long x 0.75m wide x 1.050 m high at one end to accommodate our hypothetical average skipper. We may not be able to use the same space for both accommodation and sailing space so might need to do this twice over, but sitting up facing across the boat even a long legged sort needs only 1.200m of space from backrest to heel.

A month at 2 kg of food a day is 60 kg, this would include an allowance for stove and lamp fuel, with a weeks water at 3 litres a day the voyage consumables stores weight would be 81 kg. Given an 80kg skipper, 25 kg of ground tackle spread between two good sized anchors with some chain and 20 fathoms of nylon warp on each, an allowance of another 25 kg for clothing, pots and a camp stove we’re up to a bit over 200 kg (440 lbs) of “cargo” we have to carry.

A boat like this will be heavier than a typical dinghy of the same length but I expect about another 90 kg including the rig would do it. Given the tendency of cruisers to collect gear we should allow for 300 kg total displacement. That’s quite a lot for a dinghy of this size; she is to be as heavy as most day sailers with three crew so we need a buoyant and powerful hull.

Self righting, even the most carefully designed of ocean cruisers still has a narrow range of inverted stability, so the trick here would seem to be to get the stable range so narrow that she can be rolled up by her normal crew of one. To take a tip from “Maximum Exposure” we need to get some enclosed (buoyant) space high up relative to the hull. If possible we should have some weight low down and well secured so it contributes to the righting moment.

She should not have so much buoyancy tankage out near the gunwale that the skippers weight cannot sink one side to roll her, and the little cruiser should not have so much water in her when she rolls back to her feet that she is unstable due to free surface effect.

A securely watertight cabin and enclosed buoyancy chambers in the ends of the boat will do most of what we need with the buoyancy, at the helm the sailor needs only about 750mm in a fore and aft dimension if the full width can be used, water ballast would work but does tend to complicate the structure and is not particularly effective for the volume taken up. Perhaps some fixed ballast amidships? We can’t pick her up without a helping hand so another few kilos might not hurt. Lets draw this out and see.

Centreboard? They get in the road if they are in the middle, so why have it in the middle! Ok, an “offcentreboard!”

Storage. Hmmm, plenty of room and much of it can be amidships and low down, needs to be secure in a rollover or knockdown though.

An anchor space can be organised at each end so that wet and muddy ground tackle doesn’t need to be down below, auxiliary power, rowing I think would work fine for a boat of this size (suits Bill Serjeants Micro Sailboat class too) and anyone who wants an outboard can hang one on the back.

The rig? The rig! As the layout takes shape in my mind there is not room to put a mast in the usual place, no problem, I have in mind a rig that will allow the boat to be hove to head to wind so she can be reefed without having to hang over the side, a rig which will allow the sail area to be spread out and low, which can be used to help the boat self steer and which is simple and economical to set up.

A balance lugsail main and slightly larger than usual sharpie spritsail mizzen will do all of this; your choice for spars could be any one of alloy tube, bamboo, carbon fibre tubes, or wood. There should be one or another under the brother in laws house or somewhere else just as cheap.

Very much time to start the pictures so out comes the graph paper and pencil.

#1 a pencil sketch is the first stage of the process, and is really just I thinking out loud and making notes. It shows the basic concept, layout and spaces.

#2 from the above a drawing is made on graph paper so the proportions are more clearly defined. By using the graph paper I can map the sizes of each space required, I can work out the optimum spacing for frames and bulkheads, headroom, rough areas of sail and so on.

#3. From drawing #2 comes the next stage, which is a drawing close enough to do calculations from. It is done on heavy polyester drafting film which can take much rubbing out, and the initial stages of the drawing work is done with “non copy blue” pencil, then 6h x .25mm propelling pencil, and finished off with .25mm tube nosed “Rotring Rapidograph “ pen using black “film” ink.

From this drawing calculations are made as to weights, stability, load carrying ability, centres of buoyancy, gravity, effort and lateral plane, Prismatic and block coefficients, sail area to displacement, water plane loading, water flow paths, foils, sail area and distribution, structural loads and how to carry them, ergonomics and economics, building method and on and on.

Of course previous experience makes a huge difference at this stage of a design, much of what I need is already to hand having designed boats of similar size and weights, building the occasional boat myself keeps me in touch with what is practically achievable with the materials so I end up with a boat that can be built without too much tearing out of hair.

#4. Structure, all dimensions are taken off the #3 drawing so the dimensioning is consistent, any really odd joints are detailed, as are the bulkheads and frames. From this drawing on the development of a set of plans is a drafting function, Stuart Reid does this for me on my really big projects, the information is there in #3 but it requires time and application to produce the detail work from which the builders get the solutions to their many questions.

While the excitement is gone to some degree it is this stage of drawing that is the most important to the home boat builder, I was in a super yacht building company the other day, taking to one of my designer friends, he is employed solely to produce interpretations of plans and drawings of components from the designers originals. My customers can’t afford to hire him so we do the work here before the plans go out the door.

Now, how do we present this thing to the clients? So often it is the story illustrating the capability and possibilities of the design that sets people to thinking, a raw set of statistics and a profile drawing doesn’t grab the imagination so. Few people are able to make the leap from a few lines on paper to the mental imagery that would see them watching the sunset from the cockpit, so the next job is to write a story which will tell the reader just what it is that has just been set out on paper.

John Welsford
Designer.

A Tread Lightly Tale

The little boat butted her way through the chop, the tide running out strongly into the sea breeze setting up steep whitecaps out in the channel, sheltered in the tiny cruisers deep cockpit her skipper chose to stay out with the current behind him where progress would be best. His wife was waiting at the boat ramp where he had launched three days earlier, she would be happy to see him, and keen to exchange stories of the previous few days.

It hadn’t always been so. They’d just managed to get by during his working days, the boys had gone to the local Tech, University had been beyond their finances but paid for by a lot of overtime at the engineering works. They were now qualified, had married and were doing well. There had been little time for hobbies so when he retired there had been little to do. He’d tried to help around the house and was dismayed when his wife of almost 40 years had resented the disturbing of long established routines.

The old tradesman had lost more than a job when he retired, he’d lost a whole reason for being, and was lost without the routine and prestige of his position as foreman engineer in a prominent local company. And it was with some trepidation that he went to a 'retirement seminar' (but they’re all old!) Where they suggested that he take up a hobby. “Build something,” They said. “How about some furniture? Or a small boat so you can go fishing with some mates” Treat it as a job, go out to your workshop at 8 30, come home for lunch, and finish at 4 pm! That gives you a routine, and leaves Maggie some space too!

Well, he’d sailed with his grandad when a boy, enjoyed the estuary near home and although not a fisherman thought that exploring the rivers and lakes could give him an opportunity to use his camera on the wildlife, to see the natural side of the world that had been always out of sight from the welders and lathes of his life at work.

A neighbour was building a boat, he could hear the hammer and router in the evenings, and see the bow of the boat when he passed his garage. One Saturday morning he called in, was asked to “hold this please” and was soon an essential helper in the backyard boat works.

Lots of people called in, coffee was always on, friendships formed, skills were learned, opinions exchanged and dreams discussed, he became a part of a social circle of D I Y boat builders and his engineering skills were in strong demand

(“ Maggie, I’m off to Fred’s for a couple of hours, he needs a hand to get his rudder pintles made up”).

Life was getting better.

It came time to choose and get on with building his own, and after a lot of thought his friends in the sawhorse committee drew up a shortlist of wants.

Stay aboard, yes but only one bunk would be needed, as Maggie was not a sailor.

Cooking? Of course!

Type, sailing boat, a yacht but sort of a working boat flavour.

Centreboard so the upper reaches of the river could be reached.

Trailerable, there were other harbours and lakes within range.

Size, although he did not like to admit it, the budget was too tight to allow anything but the smallest and simplest of craft.

Budget, if this was to be achieved, it had to be cheap.

TREAD LIGHTLY featured in an article in a magazine that turned up in the boatshed one day, “ Look at this Bill. Look, a comfortable bunk, space for a camping stove, she is small enough to row, draws hardly any water with the board up and she should sail really well. It’s small but it’s got everything you need! ” And it did too, he fell in love with her instantly, and it was only the following week that the plans arrived, a trip was made to the local builders yard for some high grade construction ply and the back of the garage was cleaned out. (Its OK love, the car will still fit in there when I am not working) One momentous evening, before his friends from the sawhorse committee the first piece of wood was cut.

Building was fun, even if at times it took some puzzling, Bill found himself unexpectedly proud when Maggie brought friends out to look at the project and was wonderfully complimented when she volunteered to sew up curtains and bedding for the tiny cabin.

Working steadily, and enjoying the project it was only a winter before Tread Lightly was being fitted out, Maggie and Bill had enjoyed the trips to the second hand stores looking for the fittings that Bill had not been able to make himself. A local sailmaker cut down some second hand sails, the trailer towbar was extended and rollers fitted, and the big day was at hand.

The whole committee were there, plus the boys with wives and a couple of brand new grandchildren when Maggie sprinkled the stubby bow with lemonade and shared what was left with the toddlers, the boat was carefully carried to the waters edge by four of the committee and Bill, at the oars, gently sculled her out to where he could put the sails up and the centreboard down. The cameras clicked. Gently she heeled to the breeze and Tread Lightly, with a chuckle at her forefoot moved quietly off into the warm evening.

A year had gone by, the voyages getting longer as the skippers experience grew, the boat now had a dedicated toolkit and galley equipment, Christmas and Birthdays had seen unexpected gifts of wet weather clothing and a selection of plastic laminated charts. Tread Lightly had been thoroughly tested in a wide range of conditions including a scary few hours hove to when caught out in a serious squall and with practice his cooking on the tiny camp stove had improved out of all recognition.

Bill had been away in the upper reaches of the tidal harbour for three days, living comfortably and hugely proud of his self sufficient little home, busily sailing from one place to another with his camera at the ready, excited at the prospect of adding some photographs of the rare seabird he’d found to his collection. Maggie had got over her apprehension at having her partner away in such a tiny boat and had even been out occasionally for picnics. She enjoyed the tales of her mans voyaging, and talked happily to her friends at their craft circle about how cheerful he was now that he had something to keep him interested.

She waited at the ramp with the trailer ready for the wee cruiser, keen to hear how far he’d been, watching as Bill's grey head came into view sheltered behind the cabin, waving as he stood up to drop the main, the boats head held to the wind by the sheeted in mizzen as he got the oars out to scull the last few yards to the beach.

Their long hug said everything.

I’ve written the above to show how I work, and while the scenario is fiction it is very close to what I have seen among friends and relatives. The boat is designed as a serious estuary cruiser, stable, very capable, surprisingly comfortable for day sailing two or overnighting one, she will fit on most ordinary garden trailers, she should not cost a lot and should be achievable within a very tight budget.

I see my teenager looking at the drawings right now. I can imagine her appropriating a corner of my workshop so she could knock one of these together, and would be pleased to be the one waiting for her at the boatramp.