Build an Irish proa
Mike Teale designs and constructs a small, stable craft suitable for solo motor-cruising on the Erne-Shannon waterway system
A small, stable craft suitable for solo motor-cruising
One of my many resolutions when moving to Ireland in 2015 was that my habit of building rather strange, small boats every year or so was at an end.
However, events took a turn, as they so often do, and I felt it would be foolish not to use some free time to explore the Shannon-Erne waterway. In order to that, I would require some sort of craft and, while a hire-cruiser may have represented the obvious answer, it seemed a shame not to build something and try it out.
For some time I had mulled over a method of building a small boat with adequate accommodation for one person who is used to, and enjoys, camping. The problem essentially revolved around providing an enclosed space around 0.65m wide by 2m long with a headroom of about 1.2m and incorporating it into a boat form that was simple and fast to build, very stable, light, shallow draught and reasonably efficient to propel.
The conclusion that I came to was that a proa configuration (or, more correctly, an outrigger canoe) would provide the easiest solution; a slim central hull providing the accommodation with stability provided by an even slimmer pod connected by crossbeams. Propulsion would be provided by a small four-stroke outboard. As such animals are surprisingly heavy when compared to their two-stroke predecessors, I would mount it centrally to keep the ends of the craft as light as possible. The only real concern I had was whether the outboard would simply push the boat round in a slow circle irrespective of what the rudder did. If this actually happened, Plan B would be to mount it on the aft bulkhead and form a well and, of course, pretend that this had been the idea all along.
The ‘flat bottom and box-sides’ approach is a bit of an eyebrow-lifter to those whose concept of a proper boat has silky curves at its core, but the flat bottom allowed all internal space to be useful while keeping draught to a minimum and ensuring that building difficulty was ‘exceedingly limited’. A simple sketch was the extent of my design aside from convincing myself, via basic calculation, that when fully loaded with the 75kg designer/ constructor, 20kg outboard, 15kg fuel, 10kg of sleeping bag and associated items, 5kg of food and 10kg of the vitally important ‘miscellaneous’, I would be left with reasonable freeboard.
Plywood was the obvious material of choice, and I went through the usual issues when trying to source material that was good enough for the task without being ridiculously expensive. Plywood classifications used to be pretty straightforward but, these days, it is difficult to know what your money is buying. Indeed, in the end I purchased what seemed to be reasonably-priced marine plywood, but the delivery docket stated ‘Marine plywood to BS1088 (not for marine use)’. Curious.
I used 6mm thickness for everything apart from the bottom and bulkheads of both the pod and the main hull, which were 9mm. Connection areas for the crossbeams to the bulkheads were doubled-up 9mm plywood, and other
items were made from timber which was lying around. I used a combination of screws and epoxy and all significant plywood-plywood seams were also taped with glassfibre and ended up with a structure that was strong, rigid, relatively light and watertight (in terms of both lake and rain water).
In order to protect the plywood that would be either underwater or close to that region I applied a conventional oil-based external paint system of primer, undercoat and two coats of topcoat, and then an additional two coats of waterproof bitumen paint. I was a little uncertain regarding this approach as I had not tried it before, so I contacted the manufacturer of the bitumen to seek their advice, by email. I received a response which was not particularly useful as it ducked the question of whether their paint could adversely affect the underlying paint system by, for instance, softening it.
To bolster my confidence I created a small test panel, and the results seemed to indicate that in the short term at least, neither paint system had any effect on the other. Interestingly, during my subsequent trip I was chatting to the owners of a wooden boat built in the ’30s that was used for day-trips on the Shannon, and they told me that the approach I had adopted was very similar to one that they had used successfully for many years. Nothing, as they say, is new.
The construction process was very straightforward, and using only very basic tools and not a great deal of focus, everything was complete and ready to launch in less than 8 weeks (probably 250-300 hours). I kept to the key dimensions on my sketch but the exact curve of the hulls in plan and sheer was merely ‘pleasing to the eye’ as opposed to anything more exact. The main sequence of events was to join 8ft lengths of 9mm plywood for the bottom of the main hull and the 6mm plywood for the sides using epoxied butt-straps, cut them to shape, fix the chine piece to the bottom, fix the sides to the chine, cut out and fix the bulkheads, fix the top stringer, fix the horizontal cabin-widening piece, fix the cabin and decks and then fit the intermediate stringer.
Then I built the pod, using a single length of plywood, and finally I created the crossbeams. In hindsight, the only difference to this approach that would have been beneficial would be to have built and offered up the crossbeams to the main bulkheads of both the main hull and pod before fixing them.
In the event, the crossbeams required various shims and washers for a good connection to be made.
Launch day arrived in mid-April, and my resourceful friend Walter Quirke transported the craft (broken down into its component parts) to Ballina on the southern part of the Shannon River where there is an excellent slipway. Together, we assembled her, and off she floated with no nasty little leaks of any description. There was great interest from passers-by, and a kayaker made the observation that, really, she represented an old man’s kayak with accommodation built-in and no need for physical effort to get from A to B. He was right. That is exactly what she is.
Over the next 18 days I made my way up to Belleek and back via Loughs Derg and Ree on the Shannon, the Shannon and Erne waterways and then the Erne Upper and Lower Loughs. Overall, this trip is about 800km and must represent one of the finest inland waterways voyages in the British Isles, combining serious lumps of water with fetches of many miles and where sensible use of weather forecasts and careful navigation is a necessity. One encounters the most beautiful of canals and rivers, where the absence of boats outside the main holiday season is remarkable, and the wildlife and scenery almost overwhelming.
Twill, as she was known (as in ‘it will do’), performed splendidly in the mixed weather that I experienced. As with all craft, she had her own characteristics, and one was that when starting off from stationary she would gently turn to port until the speed was above about 1.5mph. However, when coming into a mooring, with the engine in neutral, she would steer positively right up to the last moment.
I routinely had the 3.5hp Tohatsu engine throttle at the position marked ‘re-start’, and at this she trundled along at between 4.0 and 4.3mph according to GPS, depending on wind direction, and consumed 5lt of fuel every 11 hours. By opening up the throttle to about a third of maximum, she moved at about 5.5mph but with a considerable increase in wash (and noise). Using more throttle than this caused intermittent propeller ventilation which will probably be overcome, or at least reduced, in the future by lowering the position of the outboard such that the ventilation plate is a few inches underwater at rest.
The sleeping accommodation turned out to be nigh on perfect, and I had 19 excellent rests in the dry and warm. It initially took about 30 minutes to get all the gear in the right place and then get comfortable, but this reduced to about 10 minutes after experience was gained and rain showers provided a motivating force.
Stability, unsurprisingly, was extremely good, so there was never any need to plan how to get on and off or where to sit when the wind howled. Lateral rocking motion resulting from wave action was quick and jerky, as with all small multihulls, but there was very little pitching at all, mainly due to her very fine, unflared bow.
The project was certainly a success. It is always satisfying to come up with an individual solution to a situation and, for me, this little craft is great for easy ‘hiking on water’. She formed the basis of many conversations on my route and, while those used to large cruisers were aghast that I would sleep in her, those used to camping were impressed at the space available. It takes all sorts!
A simple sketch was the extent of my design