Building an aluminium boat
BUILDING ONGEMAK
Part 1
Oloff de Wet
Brothers Oloff and Muir de Wet have recently launched their aluminium sloop, Ongemak, which they built over a period of five years. This is part 1 of their nautical adventure in the backyard.
The Name
Occasionally one has the rare privilege of reading a sentence or two that capture your sentiments much better than you yourself could. There Be No Dragons: How to Cross a Big Ocean in a Small Sailboat by Reese Palley was, for me, a book with many of these gems. One of the highlights is where Palley warns against being “overly dedicated to comfort”. He urges us to “break the pattern of thought that says more comfort means a better life. The good life has damn-all to do with comfort. The good life has to do with stretching mind and body...”
Ongemak, the name of our boat, is the Afrikaans word for discomfort. It was also the name of our grandfather’s farm, and from the moment that Muir and I came up with this name, it stuck, it grew, and sometimes became akin to a living force behind the project. It was a name that at once reflected our roots in the platteland far from the sea, as well as a sense of adventure and a willingness for sacrificing comfort and comfort-zones for new uncharted horizons.
The Beginning
Muir and I had our first serious taste of sailing (albeit not of salt water) when, together with our friends Tinashe, Elisma and Adolf, we acquired a Miura on the Vaal Dam. An article like this is no place for appropriating blame, but it was mostly Hennie Olivier's fault. Shortly after we had arrived back in South Africa, after a year-long transcontinental trip, and Muir and I were telling Hennie the story of how we, with our youngest brother Francois, had sundowners in Dakar on the last evening, having sold the old Hilux to buy our flight tickets back. Sitting at Dakar's beautiful yacht club, staring out over the boats, we'd already started dreaming of new frontiers. So Hennie immediately got up to fetch his SAILING from the car, and together we started going through the classifieds. He later drove through from Bloemfontein to advise us when we bought the Miura, and became our sailing mentor and a true friend.
Having a Miura on the Vaal proved to be perfect for the metamorphosis from land animal to amphibian. The Vaal can occasionally be nasty, but it is mostly friendly, and a Miura is always a very forgiving boat. But we also learnt that owning a boat is about a lot more than sailing. It is a way of life, and being part of a community of often eccentric individuals. It is interacting with nature in the most straightforward way, and (if we are honest) often has a lot more to do with keeping and maintaining a boat than sailing it. This played a major part in what followed.
Human nature means that we always want more, and sadly sailing does not cure us of this malady. Soon I started thinking of improvements to the boat – small ones at first, and then increasingly larger ones. It did not help that I was busy with a PhD in Geometry, because often during my years of study I found that when duty called, some other project promising pleasure started calling like a siren in an even louder voice. So slowly an idea started brewing...
My mother often says that Muir and I are twins born two years apart, and it is true that we share a like-mindedness which is sometimes uncanny. So it came as no surprise that, when we discovered we'd both moved on to a new page in our lives, it was in fact the same page. (He was now working in aerospace medicine in the Middle East and I was a lecturer in Pretoria.) This is what our new page said: It makes no sense to sell the best 8 hours of every day. Life is short and the world is big. Let's move to Cape Town and build a yacht.
So in our late thirties we both quit our jobs. We said goodbye to the office, confident that we would soon master the mystical skills of welding and the wielding of power tools. Success was a given, because when he was 7 and I was 9, we built a really nice tree house. We even had the dog up there.
Design criteria
This is more or less what we wanted:
- A sloop for extensive cruising for two couples.
- Minimum maintenance and simple systems
- Energy efficiency and complete solar reliance
Finer detail of the design will be discussed in part 2 of this article.
The Material
We wanted an empty shell and to design our own interior layout and systems, so we started off looking for a hull and deck, or a semi still in the beginning stages. But somehow, even though we looked at quite a few, we were never happy. It eventually dawned on us that what we wanted was something much too specific. We realised that we would have to start from scratch.
There is a lot of information available on different hull materials, and on the pros and cons of each. Our boat was to be used specifically for cruising, and for this we decided on aluminium:
- Minimum maintenance: I strongly believe that many boats are designed to look nice at boat shows without taking into account how the boat will have to be maintained for the next 30 years. Modern aluminium yachts are not painted on the topsides or at the inside, and osmosis does not exist. Steve and Linda Dashew describe how they used to be full of concern for the boat's gel coat when tropical traders came in canoes and dugouts to sell fresh fish, fruit or coconuts. But once they got an aluminium boat, concern melted away, and was replaced with nonchalant chat and friendly barter. This is what we wanted, a Hilux on the water. (I have never seen a bow fender on an aluminium boat!) Lastly, the hull and deck are welded together, resulting in a very dry boat, which also lowers maintenance.
- Once-off: While GRP is good for mass production, it takes a lot of work to produce a single hull. Aluminium is perfect for a once-off, especially like in our case, where the building and designing took place more or less simultaneously. It is the perfect material if you want to weld on, cut off, repair or adapt parts of your boat in future!
- Strong: Aluminium and steel are the choices for those who want to go to high latitudes where things might go bump in the night. But aluminium is much lighter than steel, so there can be much more weight in the keel for a stiffer safer boat.
- People with them love them: When we asked the owner of a big aluminium yacht at the RCYC whether he would care to show us his beauty, he was most welcoming in his rather quiet way. We had lots of questions. I saw his two Rocna anchors and asked him if he was happy with them. “Well I should be,” he answered, “I designed them.” It was Peter Smith, and after this first fortuitous encounter at the club he visited us at home on our project on several occasions with lots of valuable advice. He is not one to overstate or exaggerate, but when asked about materials his answer was simple: no material is perfect, but if he had to get another boat, if would again be aluminium. And he should know – his factories in New Zealand and later in Papua New Guinea built boats in a variety of materials, and he has been to Antarctica in his own boat more than once. (By the way, the Rocna website is a treasure chest of all things to do with anchoring.)
As Peter said, no material is perfect. The main disadvantage of aluminium is the possibility of galvanic corrosion. This can occur when another metal, like stainless steel, is connected to the hull, especially in a wet environment. The way to prevent this is through a plastic gasket, special sealant or, even more common these days, by using a non-metallic alternative, for instance a plastic sea cock rather than a stainless steel one. Galvanic corrosion can also occur if there are stray currents flowing through a marina, especially if the underwater paintwork is not in good nick. To prevent this, aluminium boats carry sacrificial anodes on the hull. There should be enough of these and they should be checked and replaced as needed every few years. This is not a problem while cruising and anchoring away from commercial power.
I might mention that I have often heard the dreaded story of someone who dropped a metal coin in their aluminium boat, and then discovered it a short while later, just in time, before it has corroded straight through the hull. I believe that this is total nonsense, or at least one of those nice stories that has become more and more fantastic as it was retold over the years. We did the following experiment: Six glass jars, each with a marine grade aluminium disc at the bottom, were filled, three with salt water and three with fresh water. Into these we put samples of respectively stainless steel, lead and a variety of coins. After six months we examined all the samples, and only where the lead sample lay in salt water on the aluminium disc was there the slightest indication of pitting, less than 0,2 mm in depth and diameter. (As far as I know, no one even goes through the trouble of painting the inside of the hull.) Herein lies an important lesson which we noticed on several occasions, namely that it is often easier to empirically test the validity of a statement than to go on hearsay or to get trapped in contradictory theories on the internet. So don't be shy – test it, break it, burn it or freeze it – it's great fun too!
Lastly, something about the price of aluminium compared to other materials. The aluminium plate for our boat cost about R75 000 ($6 000), but to this one has to add lots of consumables, as well as various bits of aluminium profile. Therefore the total cost of the hull and deck was nearly double this amount, roughly R150 000 ($12 000). It might seem tempting to rather build a boat out of steel or wood, by which one can get the hull and deck for less than two thirds of this price. But it is important to realise that, compared to the price of the whole project, which might be around R 700 000 ($55 000), this saving is less than 10%. To my mind it makes no sense to compromise on the hull material, for this would influence the character and the resale value of the boat for years to come. If money is to be saved, it can be done by having simpler interior, internal systems, rigging or engine. These could always be upgraded later.
The Skills
One of the most rewarding aspect of creating your own boat is that you simultaneously create, in yourself, sets of skills which you might not have acquired in any other way. Neither of us have ever welded before! So one of the first skills we had to learn was MIG welding (Metal Inert Gas welding). For this we contacted the South African Institute of Welding in Johannesburg, and organised to go on a one week course. The instructors there were surprisingly flexible in realising that, unlike most of their students, we were not seeking any form of certification, but rather a broad introduction to different aspects of welding from where we will be able to proceed through practising at home. At the end of the week we were tired to the bone, but we were given a good nudge in the right direction, as well as lots of advice on what may and may not work for our ambitious project.
Back in Cape Town we bought a cheap MIG welder (which only pushes the filler wire from the machine's side) and had the cable shortened (for less friction) instead of buying a more expensive push-pull machine. This worked very well and the wire hardly ever got jammed – probably because the filler wire used for welding marine grade aluminium is quite stiff. And then the fun started! We had lots of cut-offs once we started cutting the hull plates, and on these we started practising. And we watched lots of YouTube videos. And then we practised some more. We cut the welded metal up into strips and broke it in the vice. If it broke on the weld it was bad – if it broke on the heat affected zone next to the weld we were happy. The hierarchy of welds seems to be like this: a bad weld looks good but breaks easily; an average weld looks bad but is difficult to break; a good weld looks good and is difficult to break. I think I can safely say that our boat consists of equal amounts of the last two types!
Another skill was to learn how to use power tools. The wonder of working with aluminium is that normal woodworking tools are perfectly sufficient: a skill saw (fitted with a blade for cutting aluminium, available from any hardware shop) goes through a meter of aluminium plate in less than two minutes, an electric planer can destroy your project if you are not careful, and an angle grinder or pencil grinder fitted with a carbide tipped blade is perfect for removing the cold start of a welding run. Just remember not to use abrasive discs or sandpaper where you want to weld again later – these will contaminate the area and lead to messy or weakened welds. And don't forget all that safety gear!
The Place
There are those who believe that if you wish for something really hard, then you can attract it through some mysterious force. I am not one of those people, but this happened more or less in any case. One day at work while paging through our beloved SAILING magazine (it must have been lunch time) I found a curious advertisement: “Accommodation to let. Large loft on second floor of house in Milnerton, together with garden space suitable for building a yacht.” This was still a year before we planned to move to Cape Town, but, as luck would have it, my best friend Paul was in Cape Town while finishing his own boat project. He happened to be looking for accommodation and he liked the place so much that he agreed to rent it for himself in the interim. Like many other things to come, it worked out beautifully.
It turned out that the owner of the house originally wanted to build his own yacht, so he left space next to the house for the building site. This is good, because, like with many things in life, one should have an exit strategy. It might be possible to build a boat in an enclosed space, but very difficult to get it out again! We built a 12 meter long lean-to next to the house from wooden poles and beams, covered with plastic tarpaulin and shade cloth. (MIG welding needs a wind free environment.) It was a lovely space so we threw a massive party for all our friends. If you tell so many people that you are going to build a yacht in this big tent, then you have to do it!
Next instalment...
In part 2 we will look at the finer detail of the design and at how the hull was constructed:
Anyone interested in building a yacht at home, or our design in particular, is welcome to contact me at
