– Proa-Active ptII –
Continuing the saga of proas, and Rob Denney’s development of the modern HarryProa. We are up to where the tried and tested practical ideas hit the water.
Now for the real test. To try his theory in the real world Rob built Harry, a 12 x 6.5m proa with full standing headroom, two double bunks, galley and toilet in the windward hull, rig and rudders in the leeward one.
And his pride at the results is evident in his tone. “Built of bending ply* and epoxy/glass, Harry was an incredibly easy boat to build and sail. I could shunt single handed in eight seconds. It was also fast, easily achieving wind speed, despite, once again, never being optimised.”
Harry was essentially yet another experiment, on which Rob tried various rigs, hulls, beams and rudders. Despite only weighing 650kg, Harry was incredibly tough, “withstanding being blown off 500mm high blocks in the boatyard, and later being washed up onto a beach by waves ‘too big to launch a dinghy through’ and pounded for three hours.”
A Harryproa called Aroha that sailed across the Tasman.
Now it was Australia’s geography that entered the equation. Just after Rob had modified Harry to try a single beam layout, he and his family moved to Perth and a trailerable version became necessary to sail in the Swan River and the ocean. Harrigami (Harry + origami) was designed as a folding, trailerable proa with accommodation for up to four people for weekend cruising and racing, with the potential to race offshore. Again, there’s Rob’s modesty – “It also had to be very cheap and, due to my rudimentary building skills, and easy to build.”
“Mark Stevens and I drew a 15m (50ft) Harry for Australian, Dutch and Finnish clients. This boat was named Visionarry, for the Dutch boat which was designed to take blind people sailing. These boats were all strip planked timber and had very curvaceous shapes. They required a huge amount of filling, sanding and fairing.”
By 2005, Rob and Mark were casting around for a better way and hosted two KSS workshops with the acclaimed designer Derek Kelsall. “These were a real eye opener about what could be done with foam infused on a flat table. I built a couple of hulls using this method and further developed it to use cheap flat panels moulds which cut the work required and the weight of secondary laminating for joins, fit out, and the rest.”
One of the first clients to use this technique was Steinar Alvestad, a Norwegian building a 20m (65ft) Harry. It was a happy circumstance: “Turns out Steinar is a stylist of some repute, so I employed him to redraw all the boats using the new methods.”
All of this potted history appears a long way to get to the basic question – but I reckon the backgrounder was worth it. So I asked, “Why a Harryproa? And what are the advantages of this set-up?”
Rob responds with “The boat has more righting moment (RM) for its weight than a cat or tri. RM is the weight in the windward hull (50% of the weight in a cat or tri) x the beam. A four-tonne cat 8m wide will have 16 tonne metres (4t x 0.5 x 8m). A 60/40 Harry Proa of the same weight and beam will have 19.2 tonne metres (4t x 0.6 x 8m). Righting moment allows the boat to be driven harder and/or is safer in squalls.”
So is Rob Denney’s Harry Proa concept taking the best of both the Pacific and Atlantic proas’ attributes?
The man himself agrees, “although I am not well versed in the traditional boats, having arrived at proas from cats and tris and looking for efficiency/speed/ease of build and cost rather than trying to westernise a boat type that was limited by material availability.
Harryproas appear to have been a development of the Pacific proa (departure from?), by having hulls of almost equal displacement, with the ‘living-in’ hull to windward. “Yes,” says Rob, “sort of. Harrys are designed to fulfill requirements. For a cruising version, this will include safety, ease of sailing and optimising space so the lived-in hull is to windward. As they get bigger (15m+) the displacement discrepancy is not so important so the space in the lee hull is used for sleeping, workshop, machinery, etc too. Racers and small versions rely on crew weight for stability, the same as the traditional versions.”
The whys and wherefores of this need further investigation. It’s correct to say the Harryproa hulls are of similar displacement, but – “the lee hull is longer, lower and narrower, usually with more displacement available so that it will support the entire boat weight if the windward hull flies.
Prototype mini Cargo Poa.
“The usual ratio between the hulls on the cruisers is about 60% in the windward hull and 40% in the lee, although this is not set in stone or particularly important.
“Both hulls have length/waterline beam ratios narrower than 11:1, which means they do not have drag humps at speeds (in knots) around 1.34 x waterline length (in feet) which limits speed. The lee hulls are above 16:1 which, with their extra length makes for a higher top speed, more sea kindliness and less likelihood of pitchpoling compared to a cat of the same weight.”
So how many Harryproas have been launched so far? Here’s where Rob gets vague.
“No idea, I gave away a lot of plans and other information before I decided to make it into a business. Maybe a couple of dozen or so? More important (to me) is how many designers are copying what we are doing. Not just the Harry Proa format, but unstayed masts, kick up appendages and simpler build techniques.”
Like all blue-water sailors, I was itching to ask the inevitable question, “Have any Harry Proas been tested in storm/survival conditions at sea?”
Says Rob “Aroha (the te reo Māori word for love) is the only one I know of, the rest were designed for coastal cruising or day sailing.”
Suffice to say, Aroha crossed the often-tempestuous Tasman Sea. Bain Robinson built Aroha from strip planked timber and launched her in 2004. In 2006 he sailed it across the Tasman, predictably encountering a fairly severe storm on the way, with only minor damage reported.
The Aroha story is on Harry Proa’s
fine website at
While Harryproas may seem a radical and evolving new concept, some things stay they same, some keep changing. As Rob says, “Harryproa philosophy is fast, safe, simple, cheap, quick to build, prep and pack up and that has not evolved. The design and build evolution never stops as we continue improving it.”
So where exactly do proas sit in the modern multihull mileu? “Aha! This,” says Rob, “is not easily answered without a lot of disclaimers, but basically, a Harry proa is the most possible boat for the least possible money that performs well. The beam is between a cat and tri (shunting means a wider beam than a cat which has to tack is viable), the extra RM means it does not need to be as wide as a tri.
Harryproas are “Longer for a given weight as the lee hull is a smaller in cross section than a cat’s and, secondly, the total hull length is split between different length hulls.
“Harryproas are lighter and cheaper than cats and tris due to:
• unstayed masts (beefing up is highly localised)
• Self-vanging rigs which were initially Ballestron, then wishbone, now (Cargo Proa) telescoping wing sails. None of them need or have extras, require much less deck gear and have lower related stresses and loads
• Less surface area as the bows don’t need to be high enough to keep trampolines dry
• Easier build shapes which can be infused in full length panels with
• No daggerboards and their cases
• External, kick up rudders which do not need to be as strong as fixed rudders
• The windward hull only has to support the beams and keep the water out so can be built much lighter
• Furniture for panel stiffness. This is taken to extremes in the cargo proa which has non cored hulls
• Intelligent infusion which provides optimal resin/fibre ratios (1:2) Int Inf provides a surface ready for high build, so little or no external fairing.
Harry Proas are equally able to be built in low-tech and modern composite materials. Rob provides these notes about the options and their advantages: “I have built Harryproa hulls in strip plank cedar and paulonia, plywood, carbon/foam, fibreglass foam and solid fibreglass. We are currently working through an aluminium 18m. Strip-planking is good for rounded shapes, but needs sanding and fairing. Ply works for cheap (unless decent ply is used) and cheerful unless it is carefully maintained. Carbon/foam is light, stiff and expensive. Glass/foam is a little less of each and is the preferred naterial for cruisers. Solid glass is by far the cheapest (less than $AUS40,000 in the composite materials for the 24m cargo proa, including the masts, beams, hulls, rudders 8m tender and bridgedeck), but requires small panels and plenty of out of the box thinking for stiffening.
Gilbert Island small proa from Jim Sier's book Taratai.
Rob is currently building a larger 24m Cargo Proa, intended for emissions-free inter-island goods transport in the Pacific.
When will the first Cargo Proa to be launched? Rob’s answer to this question is one all home-builders of boast will relate to: “Not sure. We are 95% done, 95% to go!
“It will be shipped to Fiji (more publicity, lower cost and less paperwork than launching it here and sailing it over) and I will fly over when Covid allows, hopefully before Christmas 2021. In Fiji the lee hull ends will be attached and the rest of it assembled which may be a month’s work, depending on cyclones, the work site, helpers and other variables. Sea trials and any ‘adjustments’ will be made, then it goes into service between Suva and a couple of islands 70 and 100km away. It will only haul freight due to the cost of safety equipment. A people-carrying version would have a different windward hull.
There are currently three boats in the Cargo Proa range, says Rob, “The Mini Cargo Proa (MCP), which I was lucky enough to build in the Marshall Islands, with local help; the prototype 24m, which I am building in a shed provided by University of Queensland Composite Engineering Department with a potential Harryproa builder (who came for a look and stayed for 18 months) and occasional student volunteers; and a 4m paddle canoe.
“The MCP is 7.2m x 4m, carries a tonne and is built in ply sheathed both sides with glass. It is designed for crossing lagoons (10-50 miles) and accessing near islands. Ply was chosen as it was seen as a smaller step from traditional methods than foam which, if infused would result in excess plastic waste. However, the Marshallese are excellent boatbuilders and sailors, would have no problem with foam and glass. We have changed the design so it can be built without infusion, resulting in a longer lasting (near indefinite), lighter, tougher, easier to maintain boat. These will be built in Fiji alongside the Cargo Proa.”
During the current build of the 24m prototype, Rob experimented with many techniques to make it simpler, lighter, quicker or cheaper to build. This is why it looks different to the original sketch and the original cargo ferry. The result? “Some of these techniques have worked, most didn’t. Both were hugely enjoyable. The end result is $AUS60,000 for a 24m x 3 tonne sailing boat capable of carrying 10 tonnes of cargo and built by two old age pensioners in <18 months.
The smallest boat is a paddle canoe, originally designed for a co-op in PNG to replace heavy, often rotten dugouts that require three people to drag them down the beach. The foam/glass paddle canoe weighs under 15 kgs. Rob says women (and men and kids, but most of the interest was from women) borrow money from the co-op to buy the materials to build their boat. They do this under supervision over a couple of weekends, then use it for fishing. Their surplus catch is sold by the co-op (meaning the women don’t have to attend the market), who repay the loan from the sale proceedings. There is strong interest in this model throughout the Pacific, he says.
Cargo Proa – getting an idea of the size.
There’s one more advantage to the Cargo Proa concept, and this has to do with righting moment (RM). Rob explains: “The reason the cargo proa works for shipping cargo is the RM does not change when it is loaded as all the load is on the leeward hull. Therefore the beams and rig can be sized for the empty righting moment, which is the same when the boat is fully loaded. On a cat, tri or mono, the structures and rigs would have to be designed for the full load. Hence, the 3 tonne, 24m cargo proa capable of carrying 10 tonnes of cargo. A similar cat would weigh at least 10 tonnes empty, much of the weight being required to resist the forces when fully loaded. The design spiral would result in ever increasing weights of rig, beams, appendages and engines, whereas on the Harrypro, the spiral goes the other way; everything gets lighter.”
Rob Denney’s Cargo Proa is “a passion project, my money and time.
“I spent five years trying to sell the idea to governments, donors and sponsors. All agreed it was great, but said, ‘where can we see one?’
“The only way to break the circle was to do it myself. The initial plan was to sail it through the Pacific demonstrating it to the locals to encourage them to convince their governments that it was better for locals to build a zero-emissions boat than to subsidise the diesel burners.
“Once it was obvious I was serious and would have a demo boat, interest surged. First cab off the rank was Sustainable Sea Transport Initiative (SSTI), a well-connected group of successful business people and academics in Fiji who offered to do all the local organisation, politics, lobbying and fundraising for a trial route and a local build programme.
So what are the real-world trade possibilities using Cargo Proas in the Pacific? And what are the advantages and constraints? As always, Rob has a clearly itemised list:
Zero emissions. Pacific Island nations are eager to show they are doing their bit to reduce emissions to encourage other countries to do so too. This to reduce sea level rising and extreme weather, both of which are existential problems for them.
Shallow draft: Diesel ships cannot access the beach and/or enter the lagoon so motor up and down outside while petrol powered skiffs move the freight. Cargo proas can sail up to the beach, unload/load and sail away.
Small payload: it is not economical for ships to carry small loads, so their visits are often months apart. Consequently, villagers cannot reliably get to and from schools, hospitals and services, nor grow produce or catch fish to sell. A small fleet of cargo proas, visiting weekly would change this.
Low maintenance: Cargo proas need a coat of house paint every 10 years or so, new ropes and a new wing covering every five. Ships can only be scrubbed and antifouled in dry dock. Cargo proas are scrubbed off in knee deep water as required. Two people can easily handle and sail a cargo proa, including loading and unloading the freight which is carried in 1m cubed deck boxes, craned on and off using halyards.
Low capital cost: Series built, a fleet of 20 Cargo Proas will cost about the same as a small diesel ship. They will be built locally, providing jobs and money for the locals.
Kudos: Pacific Islanders were once the best sailors in the world. They have incredible ties to the sea and a strong desire to use it. The people who crew on cargo proas will have huge status.
Limited cargo capacity. Big ships will still be required to move vehicles etc.
Reliability: In typical trade winds, the cargo proa will reach and run faster than the diesels motor. When the wind doesn’t blow, the Cargo Proa lowers the stern of its tender and motors using the electric outboard, powered by batteries and solar panels. The routes envisaged should not require any night sailing.
Cyclones: The Cargo Proa is fast enough, and forecasting accurate enough to leave when a cyclone is approaching, sail clear and return behind it, ideally carrying supplies etc for affected villages. It can be tied up in a shallow mangrove swamp or dismantled and the components placed in a container or tied down.
Cargo Proas are built to be easily repaired on a beach, or in place with limited boat-building facilities. They draw 200mm empty, have flat bottoms and sides and non-complex skins. There are watertight bulkheads at 800mm intervals. Holes are easily fixed by sliding a piece of premade glass through the hole and water pressure holds it in place, aided by a few screws. They can be dried-out and repaired on the beach sitting on old tyres. Next tide, antifoul the exterior. There is almost nothing else to break or that requires servicing.
HARRY PROA REVERSIBLE SCHOONER
The Cargo Proa project boats will sport a free-standing, fully-rotating schooner rig, with fully-battened Bermudan-style mainsails, and wishbone booms, which angled downwards, perform the function of the vang as well. The ends of the booms will also be used as derricks for loading cargo.
A last note of realism from Rob: “The Cargo Proas will never replace big ships hauling containers of bulk goods, but that is not their purpose.
So there you have it. A dream: one with a twisty route(just a proa shunting, going backwards then forward to progress) to have got this far; and one which stands of the cusp of becoming realised in a very different post-Covid world.