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
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
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.
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
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
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
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
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.