Oloff and Muir de Wet, two South African brothers, taught themselves welding, CAD programmes, keel casting and so much more en route to building their dream cruising yacht.

The cost of building your own aluminium sloop

You can’t discuss the idea of building your own boat, and of extended cruising, without considering the question of money.

‘How can you afford it?’ is probably the most commonly asked question. The golden coin has two sides. One side has to do with investing wisely, and in ultimately earning a passive income. The other side, plain and simple but less often realised, lies in discovering that we can get by with a lot less than we think.

‘Blessed be moderate poverty!’ proclaims Friedrich Nietzsche’s hero Zarathustra. And he has a point when he says that ‘he who possesses little, is so much the less possessed.’ And also that ‘they acquire wealth and make themselves poorer with it.’

But unfortunately he seems to sleep in the forest most of the time, and much as I respect Zarathustra’s teachings he is, after all, only a fictional character.

On a more serious note we can look at Maslow’s well known hierarchy of needs. The idea is that a healthy individual would first fulfil his most basic needs – those of food, sex, shelter etc. Thereafter the individual would move on to higher needs like social belonging, and lastly to self-actualisation.

It’s clear to me that our consumer society is to a large degree stuck at the most basic levels. We keep on striving for more possessions: branded clothes, newer cars and bigger houses. And we keep at it, even when we have much more than we need.

Ultimately we are poorer for it, and this endless chase of the material denies us the opportunity of acquiring higher forms of wealth. Surely there are other things to be done! We have to read old books. We have to design and build new boats!

Personally this is what I did: I lived in a place which was slightly too small and slightly too dodgy, much like when I was a student. I tried to avoid buying all the crap that everyone is constantly trying to sell you. I drove an old car which I had bought for cash. For holidays I went to third-world countries with a backpack (these are the best holidays anyway!).

The money I saved in this way, which was about half of my salary, I invested, both into rental property and onto the stock exchange (mostly low risk Index Tracking Funds). Then, after nine years, the miracle of compound interest occurred, when I realised that I could sustain myself from my investment income – it’s a feeling of relief and indescribable freedom.

Muir, on the other hand, started saving quite late, but like the hare instead of the tortoise, he ran off to the Middle East where he was offered a much larger salary, and returned three years later with a pot full of money. He invested his booty alongside mine and we manage these portfolios together.

Designing a hull

Our first idea was to build a Van de Stadt 34, for which we had ordered the plans, but to redesign the interior to make it more suitable for two couples. These boats have a very good track record, and a 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, 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.

Metal gurus: Oloff and Muir enjoying life board their self-built aluminium yacht Ongemak – note the expansive foredeck!

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 build it.” Well Anton, we did build it, and thank you once again. And we hope the wine was OK.

Another person who was superbly helpful was Ray Mathews, who was commodore of the Royal Cape Yacht Club at the time, and organised for the plasma cutting of our hull plates.
It was incredible to see how the plates for the whole boat were cut to shape in about an hour: they were delivered that same evening.

Our excitement was uncontainable as we handled parts of our boat for the first time. Ongemak is a hard chine boat, so each plate is as long as the boat, although quite narrow. The wonder, with aluminium being so light, is that two people can quite easily manoeuvre these long plates.

So they were dragged across the lawn to the back, but didn’t remain there for very long. Over the next two weeks they were moved again, into the shed and onto the cradle, where they were to stay for nearly five years.

At the time of delivery we’d already built the cradle in which the boat had to lie. It is made out of mild steel and is rugged and strong. But we had made it with the utmost care, accurate to a few millimetres, because in this the hull plates had to rest, and it ultimately determines the shape and symmetry of the boat.

Speedy stitching

What followed was fantastic – something close to immediate gratification: every day we hauled one of the plates onto the cradle, and tack-welded it to the one underneath. Each tack-weld is only two or three centimetres long, and the purpose is to temporarily hold all the plates in the right position.

So, lo and behold, after eight days we had a beautiful shining aluminium hull next to our house.

The seam welding, however, took many weeks. The welding on the outside of the boat was done first. It is important to make welds short (about 20cm) and to scatter them along the length and also between port and starboard. This prevents distortion caused by built-up heat.

This took a long time because the welding machine constantly had to be moved, and furthermore every single weld has a cold start which had to be cut out, in our case with a special disc we had on the angle grinder.

Of course, at that stage, we were still new to the game of welding, our bodies were not used to a whole day’s manual labour, and much time was spent figuring out where to do what.

Still, the boat grew, and with it our abilities. It’s a wonderful feeling when equipment becomes almost an extension to your body, being used without any great effort.

Next came the inside. It was a relief not to weld upside down for a change, but first all the back-cutting on the inside had to be done. This involves cutting a groove along the joint of the plates at the inside so that, once welded, the exterior and interior welds are fused without voids.

The stem was also fitted during these early stages, a big heavy tapered bar.

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

To accommodate the depth of the keel in the lean-to shed a hole had to be dug in the ground!

Not very high-tech equipment for melting the lead and pouring it into the keel consisted of an old cast iron pot and a blow lamp

Building a keel

The keel is a big job and it was frankly difficult. I have a strong suspicion that nothing I read on aluminium keel construction was written by someone who ever did it themselves. Of course we now know exactly how to build the next one!

The first step was to strengthen the hull somewhat. So we fitted the stern plate, deck stringers and foredeck.

Then we moved into the garage, where the keel was constructed. It is basically an accurately made aluminium tank, into which the lead can be poured.

It contains vertical floors which run all the way down for strength. The one side of the keel can simply be welded to these floors, but there is no access to weld once the other side is on, so slots must first be cut to enable welding onto the floors.

Having cut the side full of holes, they then have to be welded up very carefully, because if not salt water will enter, and galvanic corrosion would occur between the lead and aluminium.

This requirement is so strict that you have to temporarily weld a lid onto the top of the keel, and then pressure test it to check for any leaks.

I should add that some aluminium boats have normal external lead keels, with a non-metal gasket between it and the boat, and it is attached with normal keel bolts. The advantage is probably that you’d be able to outsource this job! But the incredible strength of an integrated keel would be lost, and keel bolt maintenance would also come into play, just as it is on most boats.

Having done all this, we now got our block and tackle (ie an old mainsheet which is now our kicker) and hoisted the keel, which in its bare aluminium state weighed about 100kg, into the boat. A template was made and we then cut the hole for the keel into the bottom of the boat. A deep hole was dug underneath the boat as well. The keel was now lowered in, but we had to hoist it up a few times to file the hole slightly bigger. It is generally good practice to get parts that are to be welded to fit snugly, because it is easy to accidentally burn straight through when a gap is more than one millimetre.

But before we welded the keel to the hull we had to put in the horizontal floors.

Meticulous job

These are the structural beams under the soleboards of a boat, which gives the bottom of the hull its strength. It is a meticulous job to get them to fit the hull exactly, and each one was cut twice – first just roughly, and then more accurately after it was put in place temporarily and the profile marked with a compass.

I think it was Krishnamurti who said ‘The first step is the last step’. And in the same vein Muir often mockingly sang Dem Bones: “The toe bone’s connected to the foot bone, the foot bone’s connected to the ankle bone, the ankle bone’s connected to the leg bone, now praise the name of the Lord!”

We were constantly building and planning at the same time, and this played a role right from the start. So, for instance, we had to think carefully about where exactly the floors had to go, because some of the floors had to be extended upward to become the frames onto which the bulkheads get bolted. And the bulkheads ultimately determine the whole interior layout.

I’m glad to say that the care we took early on was thoroughly rewarded. The geometry lines up very nicely to give an uncluttered and spacious interior, and anyone who wants to produce a sister ship to Ongemak will find it straightforward.

The last step was to fill the keel with two tons of lead. A contact I made in the bar at Matjiesfontein now came in very handy and he sold us recycled lead at a very reasonable price. We melted the lead pigs in an old cast iron pot and bit by bit we filled the keel by pouring it in, or by stacking whole pigs in when space allowed. This process was a lot of fun, but we worked slowly and carefully, for our own safety and for that of the keel, because distortion to the keel had to be avoided. Water sprinklers were fed onto the outside of the keel all the time to keep it cool.

Lastly I have to say something about sealing the top of the keel. Several sources indicate that it is sufficient to seal the top of the lead with epoxy or tar. Fortunately for us Peter Smith visited us around this time and warned us to rather weld aluminium cover plates onto the keel and to pressure test it again.

This ended up being a very big job, because we didn’t plan for it at the start, so some of the floors were in the way.

We are, however, thankful to Peter for this good advice. There are many stories on the internet of people who had problems years afterwards from not having done it correctly in the first place, and I have personally met someone who had so much galvanic corrosion inside the leaky keel of an old aluminium boat that he decided to cut off the keel and have it rebuilt!

101 other things

The biggest welding jobs were now behind us, but a lot still had to be done. We put in the frames onto which the plywood bulkheads were to come, as well as three sets of chainplate knees for our double spreader mast. We carefully incorporated the knees into bulkheads or inside cupboards to keep the interior uncluttered.

This was followed by stringers to support the benches and bunks, and a watertight compartment under the front half of the V-berth. A very deep anchor locker made sure that the weight of the chain would be as low as possible.

The mounting bed for the engine was made and the engine with it’s saildrive was installed.

The sole in the saloon rests on top of the floors, while the sole in the forepeak is the hull itself. This step up from forepeak to saloon, together with the upright front side of the coachroof, means you can stand in the saloon and look out through forward-facing portlights – a rare privilege on a modern boat.

Next came the decks and coachroof followed by the cockpit, which simply drains back out through holes in the transom. Both the cockpit benches and sole are long enough to sleep on, and there is a large lazarette to portside.

The swimming platform has continuous welds, and the cavity underneath serves as an integrated water tank. When the decks were eventually painted, this part got a darker colour, so the water for the transom shower gets heated by the sun.

The last job was the building of the rudder. This was mounted in the special self-aligning Jeffa bearings, which means that the rudder will keep on functioning, even if it takes a hard knock which bends the stock. The rudder was mounted at the transom plate, and thus the cockpit remains open and without obstruction.

Design: Ongemak 35
LOA: 10.45m (34ft 4in)
LOD: 9.90m (32ft 6in)
Beam: 3.33m (10ft 11in)
Draught: 1.75m (5ft 9in)
Displacement: 5,300kg (11,685lb)
Ballast: 2,100kg (4,630lb)
Rig: sloop
Year launched: 2016
Building time: 5,000 hours
Building cost: South African Rand 650,000 (approx £38,500)

At last, then, the hull and deck were completed. It took more than two years of planning and building, but there it stood, like a giant modern sculpture next to the house. We were thoroughly thrilled and decided to throw another big house party which we called ‘The Halfway Mark’.

  1. 1. Introduction
  2. 2. The cost of building your own aluminium sloop
  3. 3. Completing the project of a lifetime
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