The passing of sailing’s true rocket scientist | Mr. Smith’s Amazing Sailboats

She is a vessel of transformation for civilized men and women who wish to explore and reconnect with the ebb and flow of natural law. It is a laboratory of earthly experience, floating above an estuary of life, the most productive ecosystem on the planet. She is a ship, a transactional embodiment between two natural entities, a partnership, a friendship, a relationship, registered and limitedly liable via a citizenship.

This sporty little multihull hails from Cape Town, the home of designer Gerhard Schein and G-Force dinghies. It’s called a “tacking proa”, though we purists would say ”outrigger”. It has all the mod-cons like a square top main and a carbon fiber bow sprit for the screacher, and it looks like a great ride. Though the actual boat doesn’t have it, the 3D model on the G-Force site shows a Bruce foil in the ama.

Edmond Bruce was a brilliant sailing theorist and experimenter who was perhaps the brightest star of the Amateur Yacht Research Society (AYRS) in it’s 60’s and 70’s heyday. He had a gift for experiments - building wind tunnels out of bailing wire and desk fans, and tank testing his ideas for a miniscule fraction of the cost of a typical university. He published his results in the famous AYRS newsletter, a peculiarly British institution that printed all manner of demented English sailing fantasies as well as serious research into sailing, and since absolutely no one else was interested in the topic, they had the field mostly to themselves.

Bruce first posited the idea of using angled hydrofoils for balancing heeling force back in 1965, and it is an idea that is ever so slowly catching on. Now ocean racing trimarans sport angled boards in the amas, and so do the latest A Cats. I’m sure Edmond Bruce would be very pleased. A Bruce foiled outrigger is unique because the foil pushes up on one tack, and pulls down on the other.

Testing with Models

2009 was a good year for the proa “virus”. We witnessed two proa “messabouts”, and the launch of a truly spectacular “giant”.

The 2009 Texas Proa Championships featured four proas in attendance, and a race between Kevin O’Neill’s 21’ Skate and Laurent Coquilleau’s 21’ proa. The First New Zealand Proa Congress had a turnout of eight outrigged craft, including several canoes of Gary Dierking’s design. James Brett’s Free Radical took home the trophy. Both events are planned to repeat in 2010.

Inigo Wijnen launched the 71’ Gaia’s Dream in Oz, and capped 2009 with the maiden voyage from Coffs Harbour to Sydney.

This proa is laid out along the general lines of the Kiribati proas, with the famous “Kiribati dimple” in the lee side, and a 40 mm lateral camber to the keel. The only hydrodynamic innovation is the use of a “vortex tunnel” keel, which Dieter Shulz and John Dalziel developed some years ago, to get better windward speed from hulls without daggerboards. Dieter built and tested aerodynamic models which showed promising lift/drag characteristics, but as far as we know this will be the first full-size test of the concept.

The 25sm crab-claw sail is actually intended for the 10 M boat, but we are using it on the 8 M model to make sure a crew of one or two can handle it safely. If all goes well, this will be quite a fast proa.

After aeronautical engineer Janusz Ostrowski calculated the weight of wood spars for the boat, we decided to “bite the bullet” and build them from carbon fiber; handling the weight of the wood spars would quickly tire out the crew. Carbon should solve that problem, but I think we are near the practical limits for a crab-claw sail on a boat sailed by only two crew.

Helmut intends to experiment with rigs, including a mast step location to windward on a girder (shown on the three-view) or in the traditional position, plus the use of a lee shroud or a bungee-loaded back-wind brace. There is a step and partners fitted to the main hull that will allow the use of a free-standing mast. It is also possible to mount a marconi rig on the mast girder, in the manner of Russ Brown’s proas.

Helmut plans to use Gary Dierking’s bungee- assisted shunting system, and will test shunting using a free yard, a continuous shunting line, and if necessary, a full-length track-and-car system on deck. Spilling lines are used for sail control.

To avoid the usual problems with steering, we went with the tried-and-true long sweep. The sweep can be used on either side of the stern, though we intend at first to use Gary Dierking’s system on the windward side. There is a lot of extra reinforcement in the ends, to allow testing of quarter-rudders or leeboards.

Non-steering daggerboards and slots are built into the hull at either end; these will take the strain off the helmsman when sailing downwind, and will also allow the boat to be balanced when the Western-style rigs are tested.

There is a 255 liter water-ballast tank located in the ama, but design 75/25 weight distribution is achieved with only 80 liters of water. There are two pumps located at the cockpit to fill or drain the tank.

One trick we will try is to make the lee pod do double-duty as a dinghy. This is an old idea with several major problems, but we are going to see if we can make it work. The fixed pod of the 10 M proa is designed to right the boat from a static heel to leeward of 110 degrees. We won’t achieve such a deep angle with the dinghy-pod, but we will get self-righting to at least 100 degrees.

Specifications

LOA- 8 M (26’4")
LWL- 7.518 M

Ama LOA- 4.96 M
Ama LWL- 4.82 M

Beam Overall- 5.401 M
Beam Hull- 0.883 M
Hull BWL- 0.407 M
Beam, Hull C/L to Ama C/L- 4.16 M

Beam Ama- 0.377 M
Ama BWL- 0.293 M

Hull Draft- 0.488 M
Ama Draft- 0.29 M

Aka Clearance over flat water- 0.803 M

Design Displacement, fully loaded, with crew, all equipment,
and 80 liters water ballast- 640 kg

Ama Water Ballast Capacity- 255 kg

Design weight distribution- hull 75%, ama 25%
Wt. dist, no water ballast- hull 85%, ama 15%
Wt. dist, full water ballast- hull 60%, ama 40%

Prismatic coefficient:
Hull- 0.61
Ama- 0.638
Hull @ 640 kg w/Ama flying- 0.631

Sail Area- 25 M2 (269 sq. ft.)
Mast Length- 7-8 M
Yard and Boom Length- 8.3 M

Design Credits

Overall concept, lines, general layout: John Dalziel
Construction design and methods: Helmut Mueller
Sail plan, spars and carbon fiber specifications: Janusz Ostrowski

I’m very pleased to announce that Schacht Marine, my professional marine industrial design site is now up and running! It includes a blog (of course) and that will be where the majority of my posts will appear from now on. Schacht Marine will range much further afield than Proafile, gathering inspiration from all sectors of the design world. That is also where I’ll be presenting new proposals - and there will most likely be a proa or two in there. I’ll also be looking at modern yacht design while wearing a cultural analysis hat, which I think could be a lot of fun. See The Battle Axe for an example. Please come visit and say “Hi” at the new digs!

Proafile will remain as an archive and resource for proanauts, and proa specific content will still be added. Thanks to everyone who contributed to Proafile over the years, it has been an honor and a privilege to get to know you.

All the best,

Michael Schacht

The Beach Cruiser sketch from last March has progressed into a 3D model - my first 3D project in a long while - a good vehicle for relearning the ropes. To recap, Beach Cruiser is intended to be a multihull version of the popular "open boat" style of camping cruiser. Over the years, small cats have become somewhat the victims of their own success - evolving into pure race boats. It's a bit of a shame really, considering their roots come from the ocean crossing voyaging canoes of the Polynesians. Why not a beach cat "voyaging canoe"? A small trailer boat that maintains (much) of the performance of its race bred cousins, but with considerably more storage, comfort and seaworthiness. A boat for really going places... quickly!

A multihull designed to live on a trailer immediately comes up against the beam issue. 8'-6" is fine for a racing cat designed to fly a hull at every opportunity, but what about a cruiser? Chris Ostlind has tackled the stability issue with his Neo 21 camp cruiser catamaran by using a clever sliding-beam design that extends the boat out to a rock solid 11' of BOA on the water - increasing the stability to match the powerful sail plan. With Beach Cruiser I'm taking the other approach, accepting the 8'-6" trailerable beam limit (which gives me the considerable benefits of a simplified structure and speedy set-up on the ramp) and reducing the power of the rig.

Beach Cruiser

LOA: 20'
LWL: 19'-2"
BOA: 8'-6"
Hull beam: 1'-6"
Draft: 11"
Sail Area: 220 sq. ft.
Mast height: 20'
Mast height including gaff: 26'-2"

The Sliding Gunter Rig

The rig is a 220 sq. ft. modern sliding gunter sloop (first proposed on the 23' Manu Kai) and the most innovative aspect of the design. The gunter rig has several advantages for a small cruising catamaran:

• Easily rigged from a trailer - The rotating mast is only 20' long, which makes trailering a lot easier than with your typical unwieldy beach cat mast. The mast is the same length as the boat, creating a nice trailering package, and it is also 28% lighter than a 28' beach cat mast. A cut-down Hobie mast would be perfect. The mast also clears low bridges more easily.
• Aerodynamically efficient - The carbon reinforced wood gaff makes an excellent aerodynamic shape, smaller in diameter than the mast.
• Easily reefed - The gaff saves weight aloft (the best place to save it) and even more important, the gaff is easily reefed, a feature almost unavailable in traditional beach cat rigs.
• Automatic de-powering - The gaff will bend off in gusts, automatically de-powering the rig, almost in the manner of free-standing rigs. This is a feature highly desirable in a narrow beam cruising catamaran - and the one that can tame the high strung beach cat into a manageable cruiser.

The only downside I can see to the rig is that the height of the asymmetric chute is reduced, but since this IS a cruiser, probably a good thing. The blade jib is self-tacking.

The hull shape is a slender curved V. It needs no boards to sail to windward, and is a robust shape that takes beaching well, delivers a great ride, and looks good doing it. Construction method is tortured plywood (mildly tortured, really just tickling) and the hull shape is symmetrical in order to help the builder keep things all lined up and true. Also good for mass production, since only one hull mold is required.

The solid bridge deck with raised seating goes a long way toward keeping the crew comfortable and dry. The bridgedeck is 16" above the water, providing excellent wave clearance and contributing further to a smooth and dry ride. The solid cockpit floor measures 6'-8" x 5' - just enough for a large double air mattress, and by raising the boom, a boom tent can turn the cockpit into a cozy camp site. A canvas dodger can be fitted just aft of the mast to further protect the crew in colder climates.

Still to be added are the "wing" seats, which allow the crew to shift their weight out to windward by a significant percentage.

As mentioned in the earlier article about Beach Cruiser, the boat was inspired by the solid bridge deck cats of C/S/K - the prototype "beach cruisers" of the '60's. Like Aloha shirts and Vans, the style is a perennial favorite. I hope you enjoy the modern interpretation.