Practical Boat Owner – May 2018

medium sized boat is much cheaper to
build than a larger one, since the cost of
boats tends to go up exponentially with
size. For a cruiser this is important,
because you don’t simply want to visit
beautiful anchorages all over the world

• you also need some pocket money to
  rent a car to explore the interior. Or maybe
  just book into a hotel with a big bath once
  in a while!
  As confirmation of this, the friendly
  people at Van de Stadt estimated that it
  would cost about 50% more to build the
  Stadt 37 than the Stadt 34.
  To begin our build project we ordered six
  marine grade aluminium plates, each
  6mm thick with dimensions 2m x 6m. We
  were busy figuring out how to cut the
  different hull plates out of these when we
  realised that there would be a fair amount
  of aluminium left, and that it was actually
  possible to build a bigger boat with the
  available material.
  Let’s stretch the boat by 2.5%, we
  thought, and inadvertently pushed over
  the first of many dominoes.
  Then followed an altered hull shape with
  the bow more upright for a longer
  waterline; more freeboard and the cockpit
  further aft for a more spacious interior; a
  large foredeck to lie on as well as a proper
  swimming platform aft; a step in the
  coachroof with hatches for a view forward;
  and a draught limited to 1.75m for cruising
  in canals.
  To do this I read several books on yacht
  design, and Muir became an expert in
  CAD, drawing and redrawing our altered
  design several times on his laptop.
  I taught mathematics for quite a few
  years at university, but to use my
  mechanical engineering and maths
  background for something which was
  actually going to exist in three dimensions,

Slots on one side of the keel allow the

floors to be welded in where internal

access is impossible

High-tech equipment for melting the lead

and pouring it into the keel consisted of

an old cast iron pot and a blow lamp

was very exciting.

One of my favourite books was John

Letcher’s Self-Steering for Sailing Craft.

The last chapter makes the point that wind

vanes are usually fitted to boats as an

afterthought, but that a cruising boat can

be designed in such a way as to allow for

a simple and integrated self-steering

mechanism. As a consequence, Ongemak

has a well-balanced rudder, situated close

to the transom. There is a tiller, not a

wheel, and the stock turns in Jefa

self-aligning roller bearings. This results in

a responsive steering system with

extremely low friction, and the self-steering

is simply a large horizontal vane

connected directly to the tiller. It can be

swung to the side when not in use, so that

the swimming platform remains open.

Anyone who wants to design their own

self-steering should definitely get hold of

this book.

The decision to have a tiller rather than a

wheel also has other advantages for

cruising. The stats show that a cruising

boat sails only about 10% of the time and

that the boat is mostly at anchor. The

cockpit, with the tiller tied to one side, is

then the heart of the party: people can

move about freely and scuba gear and

other toys can easily be launched.

The definition of cruising is boat

maintenance in exotic places, but with a

tiller this is at least slightly less true.

Just to be certain...

At last we were ready to begin building.

But now the questioned popped up: did

we stray so far from the original design

that seaworthiness or behaviour of the

boat will be affected? We made an

appointment with Anton du Toit, the well

known Cape Town-based yacht designer.

We were offered coffee and discussed our

plans for more than an hour. It was a big

relief to hear that all was in order, and

when we asked for the bill we knew that

this was money well spent.

“There is no bill,” he answered, “you

guys want to build a boat. Now go and

The keel being

lowered into the hull

with a block and

tackle. Note the keel’s

internal floors, or

braces, which run the

full depth

78 Practical Boat Owner • http://www.pbo.co.uk

PRACTICAL

ABOUT THE AUTHOR

Oloff and Muir de Wet grew up in a

small town in the interior of South

Africa, 200 miles from the sea. Oloff

studied mechanical engineering and

then pure mathematics. He taught at

a school in KwaZulu-Natal. Muir

studied medicine and worked in

Mexico, Peru and the Middle East.

The brothers drove through Africa in

an old 4x4 and then got stuck on

building a boat. Ongemak is in Port

Owen in South Africa before she

sails for St Helena.