The first report on the plans for my new boat has generated much interest, and I had several questions. I’ll deal with the most frequently asked ones first.
The first Aventura was a strong well built GRP boat which survived a three hour grounding on a reef on the Caicos Bank with only superficial scratches. She served me perfectly well during my first circumnavigation but for my next boat I decided to go for steel mainly because, once again, I was planning to explore out of the way places and believed that a metal boat was better suited for such a purpose.
It didn’t take me long to realise that while metal was indeed a good choice, the maintenance of a steel hull was a real nightmare and that I should have listened to my friend Erick Bouteleux and go for aluminium, as he had done himself.
So when the time came for No. 3, the decision had already been taken. In the following 13 years my aluminium OVNI 43 took me all over the world, including Antarctica and Alaska, and I became totally converted to this wonderful material.
One of the greatest advantages of aluminium over any other boat building material is that aluminium spontaneously forms a thin but effective oxide layer that prevents further oxidation. Aluminium oxide is impermeable and, unlike the oxide layers on many other metals, it adheres strongly to the parent metal. If damaged, this oxide layer repairs itself immediately.
I must point out that my hull, and any other hull, is not made of pure aluminium, but an alloy. Those used in boat construction contain magnesium, such alloys having excellent durability in sea water.
Why an unpainted hull?
As on my previous boat, my main priority was not only a strong boat but also a functional one, and, in my view, nothing can be more functional and maintenance free than an unpainted hull.
One of the great advantages of an unpainted aluminium hull, especially for those of us who do not buy a boat to sit in a marina but to be out there sailing, is that you can forget about gleaming topsides. As most owners will surely agree, they can be such a worry when confronted with rough docks, barnacle covered pilings, or being boarded by uncaring officials who often come alongside banging into your hull with their launch without any fenders.
While in Antarctica, colliding with bits of ice was practically unavoidable, and we ended up without any scratches to speak of whereas friends of ours on two fibreglass boats fared much worse.
One of the first questions everyone asks me is how safe it is to sail on a boat without a keel.
Having sailed twice across the Drake Passage to Antarctica, both times on a centreboard boat, and having experienced on at least two occasions winds around 60 knots, with swell to match, was a perfect opportunity to test, and put to rest, any doubts about stability.
Thanks to an internal lead ballast of 3.5 tons and a displacement of 9 tons, my previous Aventura was as stable as any more traditionally designed cruising boat. I am sure that the next Aventura will be no different. I need to point out that both the previous Aventura and her successor have an integral centreboard, which means that the board can be fully retracted into the hull.
There are many advantages to a centreboard, besides shallow draft. The main role of the board is to provide lift when sailing close-hauled and reduce leeway when reaching. With the board fully down my previous boat drew eight feet and, when sailed properly, it could point as high, or almost as high, as most cruising boats.
What I mean by sailed properly is that when hard on the wind sail trim is critical, a good speed must be kept up and heeling too much must be avoided or you end up making a lot of leeway. With a draft of ten feet with the board down, the new Aventura should perform even better.
There is a certain technique in sailing a centreboarder efficiently, not just on the wind but off the wind as well. This is when the centreboard becomes a true asset as it allows you to reduce the wetted surface. Also, the ability to lift the board gradually as the apparent wind goes past 135°, and then continue lifting it up to the point when the board is fully retracted, is a great advantage as the risk of broaching is virtually eliminated. The absence of a keel to act as a pivot in a potential broaching situation means that the boat does not tend to round up when, in a similar situation, a keeled boat would do just that. It is a feature that I have blessed on many occasions, and that had allowed me to continue keeping the spinnaker up longer than I would have done otherwise.
The board was normally retracted when motoring in calm waters and the reduction in wetted surface provided an extra 0.3 to 0.5 knots of speed.
Why do I consider shallow draft to be so important?
In all surveys dealing with the subject of ideal draft there was a consensus that whereas a fixed keel may be best suited for ocean passages, when cruising having a shallow draft boat is not only ideal for exploring places that other boats cannot reach, but also safe because it allows you to tuck into a protected spot if needing shelter in an emergency.
Indeed, one of the main reasons for choosing a centreboarder is to increase my cruising options, and having a boat whose draft can be reduced instantly is a huge advantage. The fact that most aluminium centreboard boats have a flat bottom means that with the board fully up the boat can dry out on any beach, tidal bay or estuary. When the tide runs out, the boat settles down comfortably, and, as the height of the stern platform is less than three feet above the dried out surface, access aboard is very easy with the aid of the swimming ladder. We have dried out on many occasions, whether to put on a quick coat of antifouling between tides while cruising the Chilean canals, or to access a shallow bay in Alaska so we could watch grizzly bears fishing for salmon.
One other advantage of having a centreboard, that is nothing more than an aluminium plate, is that one can use it as a sounding board when entering an unfamiliar shallow anchorage. It is a technique I learned from an old friend and taught me a new meaning for the term ‘sounding board’.