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Bringing the second golden age of sail
John Marples, Multihull Pioneer
John Marples was born in Heswall, England in 1944 during WW II. After immigrating to the US, he resided in N. New Jersey for his grade school years and then the family moved to S. California. Since then he has lived in N. California (twice), Washington state, Florida, and most recently, Maine in 2012.
Shortly after earning a Mechanical Engineering degree from California State Polytechnic University in 1967, he built the Searunner 37 sailing trimaran, BACCHANAL, in which he won the 1972 Multihull Transpac and then cruised the South Pacific for two years. Under the mentorship of Jim Brown, he published his first plywood designs for backyard builders in 1975. Today, his portfolio includes dozens of wood-epoxy composite sailing and power multihulls to 65 feet. He has over 30 US Coast Guard certified commercial vessels in service. In 2005, Marples’ designs won both the OSTAR under 35-foot category (CC37 trimaran) and the West Marine Hampton to Bermuda Trawler Trek (CrossWater 49 power catamaran).
His own boat building experience includes not only the Searunner 37 but a Constant Camber 26 folding trimaran, a Cyclone 23 folding trimaran, numerous dinghies of various types, an 18’ experimental Constant Camber canoe, the Fumar 19 trailerable trimaran prototype (which he designed) and two USCG certified catamaran power boats; the Admiral Pete, a 50’ 82 passenger fast ferry and a 40’ catamaran, 49 passenger tour boat for an existing cabin structure. Both power cats were built for Kipsap Harbor Tours in Bremerton (Seattle area) Washington. Both are still in operation.
In 1995 Marples finished and flew the first of 3 aircraft he built. It was a kit plane, RV-6A with 180 horsepower Lycoming engine, and fully aerobatic. During the 10 years he owned the aircraft, he added speed modifications to increase cruise speed from 190 MPH to over 200. He subsequently finished (but did not fly) a second RV-6A for a friend. Later in 2011, he built a CX-4, all aluminum light sport aircraft from plans, using a VW engine that he hand-built. The plane achieved the 125 MPH limiting speed for LS aircraft and performed very well. He flew the plane for the first few hours but had to sell it to move to Maine.
In 2007 Marples accepted a construction project to build a Flettner Rotor powered trimaran prototype for Impossible Pictures, a London based film company under contract with the Discovery TV channel. The project was eventually called Brighter Earth and published in the Project Earth series, produced for TV. Working with Dr. Stephen Salter, Professor emeritus of Glasgow University, Mechanical Engineering, he designed and built (2) Flettnor rotors (4 ½ feet diameter x 31 feet tall) and installed them on a Searunner 34 trimaran for demonstration. The project was to show how cloud albedo (sunlight reflectivity) could reduce ocean temperatures to pre-industrial levels to stop climate change. It proposed a fleet of drone trimarans, sailing the oceans, spraying sub-micron sized droplets of seawater into the air to create clouds. John designed and built two rotors in foam core and carbon fiber using vacuum bagging techniques and installed them on a used vessel that was purchased for the project. The rotors were supported by ball bearings on aluminum pipe stub masts in the boat. The rotors were driven to rotational speeds up to about 350 RPM by electric golf cart motors using batteries on board. On demonstration day, the boat achieved 6 knots under rotors alone, in 6 knots wind, and was the only demonstration of all the projects in the series to show success.
Marples has two current boat projects underway as this is written. The first is a 21’ day sailing trailerable trimaran of revolutionary swing-wing design started in 2017. Construction so far has produced the amas and some related rigging. The second is a 110’ aluminum power catamaran design for a previous client. It is an expedition vessel, capable of 20 knots with a 3000 mile range, carrying a 26’ twin outboard catamaran tender and R44 helicopter. It has accommodations for 6 guests and a crew of 4. The owner expects to cruise the NW passage and the tropics.
John operates a part-time design and engineering office in Penobscot, Maine. John can be contacted for consulting, marine design, marine surveyor work, and advisory projects at [email protected] : remove the SPAM!
Boat Profile
Seaclipper 16
A folding trimaran for the home builder
From Issue January 2017
I ’ve built more than a few boats for myself in the past 38 years, and in all that time I have never been tempted to build a multihull. Why go to all the work of building two hulls, let alone three, when I’ve never found any of my single-hulled boats lacking in any significant way? I started getting answers to that question as soon as I stepped aboard a Seaclipper 16 designed by John Marples of Searunner Multihulls and one of nine designs in the Seaclipper series of trimarans. The hull is constructed of 7 sheets of 1/4″ six-ply marine plywood, five sheets of 3/8″ nine-ply, and lumber in commonly available sizes. Fiberglass-and-epoxy sheathing is optional. The instructions are geared for novice builders; full-sized templates for the bulkheads are provided in the plans. Stringers connecting the bulkheads define the shapes of the plywood panels for the hulls. The 15′ 11″ vaka (center hull) has a flat bottom that will take to landing on the beach without digging in or causing the kind of wear you’d get with a sharp V hull. The amas (outrigger hulls) have bottom panels set at an angle, deeper outboard than inboard. This configuration adds a fin-like element for increased lateral resistance for sailing in shallow water with the daggerboard pulled up. The angled ama bottoms also present an edge to the water, keeping the amas from slapping the waves when they’re close to the water’s surface; it’s a quieter ride. The amas’ bottoms are positioned higher than the vaka’s bottom, so their edges are not subjected to wear when the boat is hauled up on a beach.
Each of the four swing-arm akas has three bolts: one securing the pivoting part of the aka to the ama, and two (one of those anchoring the shroud bridle) connecting the pivoting part of the aka to the fixed central section on the vaka. Removing the inboard bolt allows the swing arm to pivot, moving the ama aft and inward.
The akas (crossbeams) can be made in three ways: as one piece bolted to the three hulls, hinged to fold the amas on top of the vaka, or as swing-wings, like LIMONADA shown here. With the swing-wing, the amas pivot aft and nest against the vaka, bringing the beam down from 11′ 3″ to 7′ 7″ for trailering and to fit in a standard marina slip. The swing wings can function whether the boat is afloat or on a trailer, so they are handy when launching or landing at a crowded boat ramp. The swing wings don’t require any hardware beyond nuts and bolts, and have an advantage over the hinged akas: there’s no need to lift an ama and set it down gently on the vaka. The Seaclipper 16 can be built as an open-cockpit cruiser, or as a daysailer with a tandem cockpit, with the helmsman sitting in the aft position, legs straddling a centerboard trunk and the crew sitting forward. The 7′-long open cockpit has side decks between the akas that offer more options for seating, moving around while under sail, and sleeping aboard while moored.
John Marples, designer of the Seaclipper 16 and builder of LIMONADA, goes for a sail on the Mystic River.
L IMONADA, as an open-cockpit version of the 16, has a daggerboard deployed through a slot in the cockpit sole. A softwood stick wedged in the slot keeps the board down; it has a loop of line at its top for quick removal and raising of the board. The cockpit sole is high enough above the waterline that any water coming into the cockpit drains right out. The rudder is mounted on a false transom, hinged at the top, that allows the rudder to kick up when meeting an unexpected shoal or to be retracted when coming ashore. The downhaul at the bottom of the false transom leads to the cockpit for easy operation. The rudder blade is balanced and has enough of the blade ahead of the pintles and gudgeons to lighten the load on the skipper when coming about. It also allows the arms of the rudder yoke to be short and unobtrusive. The lines from the yoke lead forward to pedals in the cockpit to for hands-free steering. A tiller above the yoke allows steering while sitting on a side deck and is the means of raising the rudder when coming ashore.
A hinged false transom allows the rudder to be kicked up. The tiller pulls the rudder up and holds it. The line at the bottom of the false transom holds the rudder down while the boat is underway.
The Seaclipper 16 is designed to take a Hobie 14 sailing rig. The pivoting aluminum mast, roller-furling jib, and fully battened mainsail are readily available from a wide network of Hobie dealers and may be found used in online classifieds. The Hobie 14 has a beam of 7′ 8″, so the Seaclipper 16, with a beam of 11′3″ can take better advantage of the 146-sq-ft sail rig without flying a hull to the brink of capsizing. Dyneema shrouds, secured to bridles spanning the side decks, support the mast. The plans include specifications for an unstayed wooden mast. For auxiliary power, a short crossbeam aft of the port aka serves as a mount for a small outboard.
The side decks provide seating when two are aboard, and the steering is then done with the tiller, not the foot pedals.
I had a chance to sail LIMONADA, the Seaclipper 16 built by Marples for Mac MacDevitt, on Mystic River near Mystic Seaport. Stepping aboard, I got my first lesson in the values of a multihull. I didn’t have to lunge for the centerline as I do with my monohulls to keep them on an even keel. The trimaran has plenty of stability no matter where I put my weight and the amas (outer hulls) have enough volume of to support my 220 lbs. Without having my movement aboard the boat restricted by the nagging demands of a monohull, I could wander around the boat. The decks are all flat, so the footing is good everywhere. While I like the sweep of a curved sheer line, the Seaclipper’s flat decks simplify the construction of the boat and provide the geometry required for the swing-wing akas.
The deck surrounding the cockpit is large enough to set up a tent for sleeping at anchor. The windshield was added by the builder to block spray when sailing into a brisk breeze.
I liked being able to walk around the boat while it was under sail with Mac at the helm. I never get to see my own boats moving through the water, so stretching out on an ama to watch the vaka’s bow at work was a treat. The 7′-square deck around the cockpit offers a place to pitch a tent. Mac has a two-person tent with an oval hole in its floor to match the cockpit opening. He can sleep to one side of the cockpit, sit comfortably upright with his feet in the cockpit and have access to the gear stowed there. The amas and vaka offer plenty of room for cruising and camping gear; commercial plastic hatches offer access.
I took LIMONADA out by myself and enjoyed steering with my feet and having my hands free to manage the sheets. Nestled down in the cockpit on a padded seat with a backrest, I was very comfortable and relaxed. The sheets were right in front and could be cleated off, making sail-handling a breeze; there was no need to switch sides or do-si-do with a tiller when coming about. During my outing the weather was warm and the wind was light, perhaps 8 to 10 knots at best with a few gusts, but in a cold wind, being mostly below deck level would be a boon. Mac had made a removable windshield that wraps around the forward end of the cockpit for even greater protection from cold wind and spray.
With Marples and owner Mac MacDevitt aboard, LIMONADA flies the windward ama. The leeward ama still has plenty of freeboard.
The light wind was more than enough to get Mac’s Seaclipper going at a brisk pace and fly the weather ama. There was no spray, so I stayed dry, and even with the boat moving at a good clip I didn’t notice any water coming up through the daggerboard slot.
I was surprised by how well the Seaclipper could come about. With three hulls in the water, I thought there would be a lot of drag in the turns and that the boat would get bogged down, but the rudder blade and the centerboard have enough area to swing the bow around before the boat loses momentum. I never got caught in irons, but I backed the jib for a moment to hasten the bow’s falling off and the filling of the main.
LIMONADA owner Mac MacDevitt reports that his Seaclipper 16 is “super fun in a stiff breeze.” Here, sailing with a reefed main on Lake Champlain, he estimated his speed at about 13 knots. “It was exciting, but I felt safe and secure.”
Christopher Cunningham is the editor of Small Boats Monthly.
Seaclipper 16 Particulars
Length/15′ 11″
Beam/11′ 3″
Beam, amas retracted/7′ 7″
Draft, hull only/11″
Draft, board down/2′ 7″
Sail area/127 sq ft
Displacement, dry/400 lbs
Displacement, full load/800 lbs
Plans for the Seaclipper 16 are available from Searunner Multihulls for $180.
Is there a boat you’d like to know more about? Have you built one that you think other Small Boats Monthly readers would enjoy? Please email us!
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Comments (2)
Thanks for the multi-hull perspective. Lots of cool ideas.
I’ve been looking. This could be the one!
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Professional BoatBuilder Magazine
Folding multihulls.
By John Marples , Jan 28, 2023
Folding multihulls and their beam-reduction strategies.
A Farrier 33R trimaran with amas folded and secured on a road-legal trailer exem- plifies the advantages of adjustable- beam multihulls, which are easy to trans- port and store out of the water.
“I’ll be surprised if you can find space in the harbor for that thing,” I heard him say as my new 37 ‘ (11.3m) trimaran was about to be launched. I hadn’t given it much thought, but now this legitimate question was raised, and where to moor was the next issue at hand. Space, particularly width of a slip, becomes the limiting requirement. But then, space also is one of the attractive features of multihulls—deck space to move around on, free from the confines of the cockpit.
Step aboard any multihull and it is obvious how much real estate they offer. Even small models seem expansive. The beam of the typical catamaran is half its length, and trimarans are even wider, sometimes as wide as they are long. Aside from increasing space, beam also boosts stability without adding ballast. The early Pacific Islanders created these form-stable craft for fishing and interisland commerce and voyaging where natural island harbors were few, so the boats had to be light enough for crew to carry them up the beach. Today’s modern multihulls are still lighter than contemporary monohulls, but the larger ones preclude the option of dry sailing them from the beach. They require more marina space than monohulls, and the limited number of slips to accommodate them can be a problem. As someone once put to me, “Multihulls have a poor ‘stacking factor.’”
With catamarans and trimarans becoming more popular, they demand mooring solutions. Some marinas offer shallow-water slips to multihulls, typically at the inboard ends of docks, next to the seawall, because multihulls either have shallow keels or retractable boards. Some marinas also designate the end ties as multihull slips in areas not used for transients. Even though these boats protrude farther into the channel than monohulls, the extra space their beam occupies is relatively small. With multihulls crowding waiting lists for marina slips, builders were prompted to consider folding systems to “improve their stacking factor.”
Without ballast, smaller multihulls up to about 30 ‘ (9.1m) can be dry-stored on a trailer, and most launch ramps easily accommodate over-width boats. If the boat’s beam can be reduced to the legal highway width of 8.5 ‘ (2.6m), the owner can store the boat at home. Today, folding trimarans and catamarans are common sights on trailers in storage yards and backyards. Various folding systems have evolved to support this need, especially for the backyard builder. Some beam-reduction systems allow the boats to be folded and stored in the water in conventional-size marina slips, while other systems facilitate efficient storage or provide street-legal trailering.
Folding Systems
Basic folding systems are separated into several categories:
- take-apart akas, the simplest beam-reduction method
- telescoping akas (sliding beams)
- simple horizontal hinge
- complex horizontal hinge systems
- vertical hinges (swing wing)
- complex swing wing
The following overview of folding systems illustrates how these mechanisms work. It is not intended to be an exhaustive listing of available folding designs. I’ll address two-hull boats (catamarans and proas) first, followed by trimarans. Each type has its challenges and advantages. All are separated into two more categories: transportable boats and trailerable boats. The characteristic distinguishing between them is the time and effort required to launch, starting from an on-the-trailer folded condition. Trailerable implies the possibility of daily launching, requiring less than an hour from trailering to sailing. Transportable denotes a road-legal trailer package but with a longer assembly time to sail away. It might even take more than one trailer load, and considerable assembly time. Legal width in this category could extend to 10 ‘ (3m) wide if OVERSIZE LOAD signs are used (consult local laws). Transportable boats usually require seasonal transport with storage in the water during sailing season and dry storage in the winter. Both categories benefit from the ability to “go to weather at 65 mph” to reach any suitable launching site, even hundreds of miles from home. This opens the possible sailing venue to any water body with a launch ramp and road access, and some trailerable and transportable boats can be delivered anywhere in the world in standard shipping containers.
Catamarans and Proas
The WindRider 17′ trima- ran’s telescoping tubular akas are secured with pins
Hobie Cats and other beach cats are familiar sights around lakes, beaches, and harbors. They are usually built to 8 ‘ (2.4m) beam and do not need folding systems. The 19 ‘ (5.8m) Tornado class catamaran at 10 ‘ wide uses a side tilt-up trailer to reduce beam. Larger catamarans needing folding systems have greater challenges than trimarans of the same length, for a few reasons: The hulls are normally bigger (and heavier) than amas for the same length trimaran; the mast is stepped on the center of an aka, midway between the hulls, which means the aka must be extra strong; and there is no easy means of supporting the hulls while the beam is being expanded to the sailing position, requiring that the trailer have an expanding-beam function. As a result, folding systems are less common on cats and are usually of three types:
- folding akas along the centerline or to a center pod
- telescoping akas
- take-apart akas
On this Wharram cat, the akas are securely lashed into “deck alleys.”
Designers have used telescoping akas, but production boats generally avoid the associated complexity and cost. The mechanically straightforward take-apart feature has successfully been used by many boats, like the 27 ‘ (8.2m) Stiletto Cat and others. Generally, the assembly of these boats takes some time and muscle, which relegates them to the transportable category. Stiletto Cat advertising suggests a four-hour setup time, but in reality, it is much longer. All the James Wharram–designed catamarans up to 63 ‘ (19.2m) are held together with rope lashings and can be dismantled for transport. The required time and effort are generally proportional to the length of the boat.
Note that the Gougeon 32 ‘ (9.7m) sailing catamaran is unique, at 8 ‘ wide, without folding capability but with a water ballast system to make up for the lack of form stability.
The large main hull of a typical smaller trimaran offers a larger interior space than a comparably sized catama ran, a deep footwell in the cockpit for comfortable seating, and a folding system for trailering with the amas connected to a well-supported main hull. In addition, the mast is stepped on the main hull, with the headstay attached to the bow, not to the akas.
Trailerable trimarans come in all sizes to about 32 ‘ long, with transportable designs somewhat longer. The latter types tend to have larger interior spaces and less complex connectives. To a certain extent, manufacturers were willing to add cost to the folding system to reduce setup time. Folding capability on or off the water also adds to the design challenges.
Take-Apart Aka Systems
This is the least expensive method and easiest to achieve for the home builder or the manufacturer. The akas may be built-up wood box beams or tubular metal. Each beam is secured to the hulls by through-bolts, bolted straps, plug-in sockets, or lashings. Tubular aluminum beams are the lightest but most expensive. Regardless of attachment method, the hulls must be supported in their respective positions for the akas to be installed. In small vessels, this can be an abbreviated procedure, but larger vessels will require a special trailer to hold the disconnected amas while on the road.
The Chesapeake Light Craft 15′ single outrigger canoe akas lash into saddles on both hulls.
Telescoping Aka Systems
The telescoping option is limited to boats where the total stack-up width and length dimensions of the hulls and fully retracted akas do not exceed the legal road limits. The WindRider 17 is a good example. The boat is supported on “high bars” on the trailer, leaving the amas free to be moved in or out. The simplicity of the akas and trailer-support system reduces cost and launching time.
In larger vessels, this system has been applied to reduce width for storage in marina slips. For these boats, the sliding system is large and complex, usually requiring some sort of power to make the telescope slide. Because the sliding mechanism requires a small clearance between the sliding members, the akas will move slightly during sailing, which is difficult to avoid.
The 1970s-vintage Telstar 26 features a simple hinge-down system with a bolted con- nection on deck and a bolted strut below.
Simple Horizontal Hinge Systems
Early trailerable trimaran designs often incorporated a simple hinged beam-reduction system to fold both sides down. Boats to about 25 ‘ (7.6m) with a 16 ‘ (4.9m) beam could be made to fold to 8 ‘ . At the ama end, lifting the hull, sometimes with attached wing deck, could require substantial muscle or a mechanical lift. Even for smaller boats this task may be beyond one person’s capability. Normally, bolts and plates between the members secure the hull for sailing. On the Searunner 25 and Constant Camber 26 (7.9m), double-hinged tubes are bolted to tangs on the main hull.
The Searunner 25 trimaran has a hinge mechanism on its metal-tube A-frame akas that secures with bolts at both ends.
Commonly, simple hinge systems require that the main hull be positioned rather high on the trailer so the amas clear the trailer wheels beneath. A disadvantage is that the trailer must be submerged more deeply than usual for the boat to float off. Compared to the Telstar system, the Searunner 25 offered some improvement by positioning the hinge point at the top of the cabinside, raising the folded ama slightly.
Complex Aka Hinge Systems
A complex system for folding multihulls, much like a garage door lift linkage, was developed and patented by Ian Farrier for his trailerable trimaran designs. It allows one person to fold or unfold the boat while it’s afloat. Before launching, the mast is stepped and secured with lower stays. Note that folded storage in the water for long periods is not practical because the immersed ama’s topsides will gather marine fouling. In addition, the arrangement of the support linkage arms has a very shallow angle with the aka, causing them to be highly stressed, which adds significant weight and cost.
Unfolding it requires help from friends.
A complex folding system I developed has only four attachment bolts and a wide-angle strut brace. It is very light but requires folding prior to launching. It relies on a simple roller dolly on a beam attached to the trailer to support the ama during folding and unfolding.
Swing-Wing Systems
In-water storage of folding trimarans is generally limited to swing-wing designs, where the hulls all float on their respective waterlines, either folded or unfolded. Many variations have been used in production boats, and among the most successful is the Quorning-designed Dragonfly. It has hinged arms supported by a “waterstay”— a diagonal cable under the arm to counteract cantilever aka loads. The outer end of the arm, on the ama deck, pivots on a single pin. The waterstay becomes slack when the boat is folded, leaving only the hinge to support the ama in the folded configuration. I’ve seen one folded boat that was damaged while moored at the dock in strong harbor waves when the ama climbed onto the dock. Swing-wing designs stored in the water must provide strong vertical support for the ama in the folded condition
A swing-wing aka system on the Borg Quorning–designed Dragonfly 32 is further supported by a waterstay when rigged for sailing. The akas can be adjusted in and out while in the water and for storage at the dock.
The main challenge of the swing-wing system is to get all the pivot axes parallel because they must rotate about 90° without binding. If there is any depth to the structure, this accuracy is critical, as the pins or pivot axles could be quite long, so even a small inaccuracy will make the system difficult to assemble, let alone pivot smoothly.
Folding Multihulls with Flat Swing-Wing Akas
The most basic swing-wing system is the flat aka configuration developed by Jim Brown. He avoided the need for perfect parallel alignment of all hinge axes because the beams are not very thick, and the pivot-pin holes can have additional clearance. For the swing system to operate without binding, spacing of the pivot points must be identical on all the swing arms. The system’s downside is strength, because the aka must support all the heeling loads in a relatively narrow beam. For some boats, a waterstay may need to be added to increase cantilever strength and reduce deflections when sailing.
The Seaclipper 16 flat swing- wing akas are made from common dimensional lumber and pivot using steel bolts.
A logical improvement in strength for swing arms is to add a truss, with triangulated strength that will easily bear all the heeling loads from the ama. Here again, it is essential that pivot axes be in perfect alignment to avoid binding. To my eye, open trusses in sleek yachts are never beautiful, but they offer higher strength for lower weight.
Complex Swing-Wing Systems
If the akas are not flat along their full length, it is more difficult to achieve a smoothly pivoting system. My latest boat, Syzygy (pronounced, sis-a-gee), is a case in point. Flat akas offer little variation in styling—flat is flat. To add underwing clearance and more attractive aesthetics, many designers favor the arched aka. This configuration allows the aka to approach the ama hull from above and connect through the deck for more usable immersion of the ama buoyancy, and to keep the aka above the wavetops.
This system has arched akas with an upward angle (dihedral) as they extend from the main hull and descend with a smooth curve onto the ama deck. The pivot axis must also be inclined, normal to the surface, to allow it to pivot. To make life simple, the vertical centerline of the ama is inclined inboard at the top by the same amount, which aligns all the pivot axes with the ama vertical centerline. If the beam is level fore-and-aft, when the ama is folded inboard, it is positioned rather low, due to the arch. To compensate, the akas must be given a negative angle of attack to make the folded ama arrive in the same position as a simple flat aka system. It’s a good challenge for any boatbuilder to get it right and a good use of a digital level. The angles in Syzygy were 8° dihedral, and a nega tive 5° angle of attack. The aka pivot surfaces must be perfectly parallel on both ends—at the inboard aka pivots and the ama deck pivot tables.
Jan Gougeon designed and built strings, a 40′ swing-wing catamaran with carbon- tubular-truss swing akas built over foam mandrels.
A late iteration of the Telstar 26 became the Telstar 28 with a vertical-axis swing-wing system. This production boat is no longer manufactured but was unique for its faired wing and attempt to hide the folding system from view. It also featured an electric linear drive to fold/unfold the heavy akas.
For transporting folding multihulls on the highway, road trailers must have some specific attributes to properly support the hulls. Most models use transverse cradle supports under the hull at major interior bulkhead positions. It is important to install bow guides on the trailer to get the hull to settle in exactly the right place when retrieved from the water. Rollers beneath the hull are not recommended, as they tend to distort it and potentially cause damage. The amas require enough support so the folding mechanism is not carrying the load when being towed.
For swing-wing boats, there is a significant change in the center of gravity between folded to unfolded configurations. Normally, the amas swing back when folded and swing forward for the sailing position. If the trailer has the proper tongue weight for towing on the hitch with the boat folded, the weight will increase when unfolded. For trailers with telescoping tongues, tongue design must accomodate that weight; otherwise, the extended tongue may bend severely during launching or retrieval.
Homebuilt wooden trailers are popular for these specialized boats, and some designers provide plans for them. Without much metal in them, they will probably float, which sometimes leads to difficulty at launching. Adding some steel channel to the bunks can solve that. However, floating is not an undesirable feature if a trailer floats level but is submerged enough to maneuver the hull into the bunks, and the hull settles into the right place automatically. Floating trailers also never run off the end of the ramp.
Conclusions
There’s truth in the humorous claim that “the new family yacht has to look good behind your SUV.” But while many of the latest small boats are daysailers, folding multihulls have expanded the trailerable and transportable boat size to include those with weekend cruising capability, up to about 32 ‘ . As we’ve seen, those essential folding or retraction mechanisms are not simple and must be carefully designed and engineered, even by the home builder. But for owners of these boats, seasonal storage and slip availability are no longer problems. And the overall reduction in total cost can bring owning a boat within reach for many more people. What’s not to like about that?
About the Author: John Marples has designed, built, and rigged many sail- ing vessels. His portfolio includes doz- ens of wood-epoxy composite sailing and power multihulls to 110′ (33.5m). He operates Marples Marine , a multihull design and engineering firm in Penobscot, Maine
Dieter Loibner | Professional BoatBuilder Magazine
Nomenclature
Multihull designers have developed some useful, specific names for components, mostly derived from the Pacific Islander language.
Aka (ah-kah) refers to the crossbeam structure of any multihull. Designers used to call them “cross-beams,” but writing that on hand-drawn plans took up too much space and time, so this shorter Polynesian name became the standard.
Ama (ah-mah) is the Polynesian name for the outer hull of a trimaran or proa. They were formerly named “floats” or “outer hulls” (never pontoons), but again, ama is shorter.
Vaka (vah-kah) is the Polynesian name for the main (largest) hull of a trimaran or proa. Since it can be confused with the other names and is not very descriptive, most designers have opted for the term main hull.
Waterstay is a diagonal stay, metal or synthetic rope, below the aka, between the main hull near the waterline and aka near its outboard end. This stay counteracts the upward load from ama buoyancy when the ama is immersed.
—John Marples
The Crossbeam (Aka) Structure
T he essential function of any crossbeam (aka) system on a multihull is to structurally connect the hulls in a way that resists all the forces generated when sailing. Heeling forces from lift on the sails must be transferred to the leeward hull by the aka structure. The forces on the akas are complex, composed of cantilever bending due to heeling loads, twisting of the structural platform, and horizontal bending caused by drag from the ama’s forward motion through the water. The heeling force, resisted by the buoyancy of the ama, pushes up, causing cantilever bending loads in the akas similar to the forces on an airplane wing. Torsion is created when the sails’ lift pushes the leeward ama bow down, while the shrouds supporting the mast pull the weather-side ama stern up. Drag from the leeward ama tries to bend the akas toward the stern, and forces from the windward shroud tend to pull the aka forward as well as up. These forces all act together at the attachment points on the hulls. In most cases, torsion is resisted by the tubular hull and cabin structure itself. Heeling is countered by the cantilever strength of the aka beams and is sometimes strengthened by diagonal waterstay cables beneath. Drag forces can be resolved by the fore-and-aft strength of the akas or by adding diagonal cables between the akas. Each folding system must accommodate these loads through all the pivoting components in the structure.
Of key interest in aka design are the loads imposed on the ama hulls by the seaway when sailing to windward. These hulls are subject to significant loads on the outboard sides. The windward ama is pummeled by wavetops, and the leeward ama is pushed sideways due to leeway. Since the aka system is characteristically attached through the ama deck, these forces are trying to rotate the ama keel inboard, toward the main hull, in either case. The same is true for catamarans, concerning the aka loads where they emerge at the hull inboard sides. These loads can be calculated to estimate the strength required for any configuration and should be part of the design’s stress analysis. If centerboards or daggerboards are located in the amas, those rotating forces are significantly increased.
Of further interest in swing-wing designs is the clearance between pins and brackets in vertical pivot mechanisms. When sailing, the forces at the hinge pins can change from positive to negative repetitively, creating noise and wear. The wear will eventually elongate the holes, reduce pin diameter, and become a maintenance problem. Designs like the flat wing can be tightened to eliminate movement, which will eliminate wear. Amas with waterstays tend to put the akas in compression and stop the vertical deflection that would be normally carried through the hinge pins. In that case, the pins would be loaded in only one direction and not be subject to cyclic ± loads. —J.M.
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Constant Camber
This technique was pioneered by Jim Brown together with input from Dick Newick and John Marples, as a system to achieve the advantages of a cold molded boat but with less labor, and specifically developed for narrow multihull hulls. Designer Chris White also once trumpeted the system when he was creating his personal trimaran Juniper , as well as for others of his design. [Footnote: Chris now leans more towards using an accurate mold and building with strip foam and glass—mostly to be able to precut bulkheads and other interior work and know it will fit.]
Once moulded, this formed sheet has the same curvature over its width—a somewhat aerofoil section with a deeper curve along the keel edge than the other. The mould typically has a slight (large-radius) curve over its length as well, so that the final form of each sheet has a slight compound curvature built in. This can be seen in this photo of a panel being lifted off its mould.
One advantage of keeping the "camber constant " is that once you determine the right shape for the strips of veneer, you can use the same shape for all of them instead of having to individually trim and fit (spile) each one to fit together with the previous strip. Another is that by varying which part of the mold you work over, one can generally use the same mold for all curved parts of the boat.
By 'butt-joining' the cambered sheets together, cutting to the required profile and further bending the corners, a reasonably fair hull shape can be created without the need for much internal framing other than bulkheads. I add a note of concern here, as 'butt joining' these otherwise rigid panels will be a highly stressed potential trouble area, where water may later infiltrate.
(Footnote: My own way around this would be to let any butt strap only serve as a partial connection on the inside, and to then grind out the butted joint on the outside in a broad vee, to lay in fiberglass tapes of various widths, so that the joints are made secure throughout the full thickness of the shell, prior to exterior sheathing).
The typical elliptical-vee form is somewhat low in displacement however, so the resulting shape is best suited to relatively narrow, lightweight designs. The result can be attractive though (see photos of Chris White's Juniper and Discovery 20 ) and as for any multi-directional laminated wood system, it is certainly strong and tough. A number of charter boats have also been built using this system, particular for day charters where the payload is light.
In terms of performance, the CC system is what I would call 'a mixed bag'. While the form offers a gentle ride in rough conditions, its not an ideal one for a main hull in many other aspects. First of all, the shape is very vee'd and this not only offers far less foot space within a main hull but creates section shapes that have a fight with passing waves. This will depend on whether the vee'd shape is at the waterline or not. (On the larger, well loaded boats say 40ft or more, it's possible that the vee'd part is mostly underwater, so the potential problem I will outline here, may apply less to such boats) .
The potential issue is easier to understand if we first imagine a light CC boat at anchor facing head-on waves. As each wave peaks pass down the hull length, the water molecules are forced horizontally outward by the vee'd sections if they are much wider above the still water line. If we now put such a hull into motion against such waves, we can visualize the wasted energy in doing this useless, horizontal work. In addition, this action also creates a more disturbed surface that the wind picks up and blows over the boat as spray, making such boats wetter than they need be. Further, as the vee'd shape is often retained forward giving a more 'old-tradition' bow overhang, this gives a high increase in buoyancy right up forward, resulting in the bow being thrown quite forcefully upwards, and then, once the wave has passed, the bow falls deeply back down into the wave trough. This starts an exaggerated pitching action, aggravated by the highly vee'd shape and not only adds more resistance of its own, but also upsets the air flow over the mast and sails that are now being thrown quite violently back & forth into the oncoming wind.
But to be clear and fair, all boats will pitch to some degree as the boat interfaces with waves of varying heights. However, when the sides of the boat are more vertical, the buoyancy pick-up is much less extreme and that wasteful 'horizontal action' from excessively vee'd hulls, is much reduced. This combination of factors not only limits the speed of such boats using such a vee'd shape, but can also introduce what has been called 'a nervous, squirrely feeling ' starting at a Speed/Length 0.5 ratio of around 2 (which is really not fast for a good multihull), as the waves create unequal side forces on the hull at any one moment, possibly requiring a larger rudder to be fitted. (The longer the boat, the less the effect though, so the 52ft Juniper would probably not even notice this).
Coupling all this to the loss of foot space inside, personally leans me well away from all hulls heavily vee'd near the waterline and those created by the present Constant Camber system more often fall into that category.
Construction notes:
Although the hull shape can be somewhat controlled with guide frames and bulkheads, this system (like that of Cylinder Molding) is still hard to build exactly to the dimensions called for by designer plans, so any question of building a strict one-design this way is out. Bulkheads are best shaped to fit after the hulls are assembled, as forcing the skin to fit a bulkhead, risks to cause unfairness and hard spots. (This latter comment also applies to the VFP (CM) system though the latter requires less fairing work as larger sheets are created with less joints.) (See Method 5: Cylinder Molding)
The above sketch comes from Chris White's fine book about 'The Cruising Multihull', and is reproduced here with his kind permission, along with the photo of 'Juniper' (below).
Here on the right is Chris White's elegant 52ft 'Juniper' hulls built using the Constant Camber system.
By varying the mould dimension and curvature, the system can be used for all different sizes of boats and CC was also used for Chris White's very neat Discovery 20 design pictured underneath.
Advantages: The positive things about the system are that the mould does not need a huge space* and that the process uses wood which many builders are familiar and comfortable with. Also, the interior of the finished boat is relatively smooth as there is less need from internal framing. The mold can also be reused over and over again for each and all curved panels. Generally, two persons can create one panel per day if the ply strips are all prepared beforehand.
*(I should mention that some builders have chosen to make longer (even full length) moulds that reduce the need for butt joints—borrowing a feature of Cylinder Molding (CM) in that respect.)
Disadvantages: The negative thing is that the system is fairly labor intensive, particularly as the surfaces require the same degree of surface finishing as does a double-diagonal construction, with many hard-edged joints to grind in order to get the surface ready for glass sheathing and subsequent painting. All interior bulkheads and frames need to be custom fitted as it's virtually impossible to build to precise offsets—an issue this build system shares with several others. The mould, with its double curvature, is also relatively complex and also requires covering with a surface ply to act as an air-tight backsheet when vacuum-bagging is used.
Since 2000, I have personally become less enthusiastic for the very Vee'd shape offered by Constant Camber , as despite the appearance of a smooth elegant shape, there are performance compromises to consider. It's all too easy to view a rounded hull (monohulls also) and get 'carried away' by its generally sweet form, but forget that it's the resistance to FORWARD motion that is the most important one to consider. Consider this. A boat makes 'a hole' in the water directly related to it's weight. To move forward, water needs to be moved aside. If this is done mostly at the surface, waves are too readily created, so ideally, this 'parting of the water', should be done as deep as possible below the surface. Deep 'U' or box shapes achieve this better. Vee'd shapes give little buoyancy for their depth and surface friction, and as they move through waves, plus up and down while pitching, they push surface water outwards in a pumping action that does nothing to help forward motion. CC shapes also tend towards a banana shape in profile and this further encourages pitching which is something we want to negate and not encourage. Foot space is also compromised compared to a deeper box or U-shaped hull, so unless the hulls are very large, interior space may be unnecessarily penalized. While CC shapes may permit a gentle up and down ride in waves, my personal view is that hulls shapes with a deeper 'U' or box form and straighter lines in profile, will offer faster hull shapes for the important extended mid-range speed. You may read more about this in other articles on this website.
It is important to remind readers that the hull or hulls are only a relatively small part of the whole project—depending a lot on how the interior is finished and equipped. To appreciate this, take a glimpse into the work on a homebuilt 42ft Constant Camber cruising trimaran, by going to this website. http://svrikki.net/Build/RTT/The_Build.html
Rikki-Tikki-Tav i is a beautifully built CC40 to a design by John Marples, developed from an earlier Searunner 40 design by the noted trimaran pioneer, Jim Brown. (But even here, later reports have described many rot issues with water infiltration into plywood). Thankfully, a small trimaran for daysailing will be a lot less work than this one.
The boatshop with perhaps the most experience worldwide in building with the Constant Camber system, is located on Cebu Is. in the Philippines. Called 'Boatshop Philippines', they have reportedly built about 20 multihulls between 30' and 60' using this vacuum-laminated system.
Owner Mike Allen has designed a series of 'Visayan Catamarans' using CC, ranging from 32' to 60'. Here is their VS 50 footer.
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21 Foot Trimaran SYZYGY Just Launched
by Small Tri Guy | Jul 8, 2019 | Self-built Small Trimarans , Small Tri Info - All | 5 comments
John and his wife Robin will now enjoy sailing it. I asked him a few questions about the boat and he replied as follows:
SYZYGY is Launched by John Marples
SYZYGY was launched at the WoodenBoat waterfront in Brooklin, Maine. She is 21′ long, 16′ beam and weighs 850 lbs with all gear aboard. The arched aka folding system reduces beam to 8’5″ wide for trailering
This is an original design but some similarities to the CC23 do exist – mostly the cockpit. I will not be offering plans since this boat is very complicated to build.
The folding system with arched akas did present a design challenge but it works very nicely and easily folds on the trailer. The hulls have narrow flats on the sides and bottom with cedar strip planking in the bilges and deck edges.
Hulls were molded on a table, split on the vertical centerline, one side at a time and then joined along the keels later.
The cockpit is large and open with room for up to 6 persons. Future improvements will include a roller furling jib and parallel battens for the mainsail to help with handling.
It is a blast to sail, reaching speeds of about 15 knots so far. I think it will go faster. The ama arrangement makes the boat very stable, even on the mooring.
Our dog Sam went for a ride yesterday and liked it.
Thanks to noted photographer Ben Mendlowitz for the following photo.
Here are a couple other pics:
“similar to the CC23” “hulls were molded on a table” So is it essentially another constant camber boat?
No, it is NOT a CC boat. John built this one using “strip plank” technique. It took him awhile to build it too, but it looks terrific. (This is a correction to my previous comment here … I had wrongly assumed it was CC because of the nice, curvy shape.)
Very nice, John. Ticks all the boxes and then some. Skinny and light. Quite a slick vaka shape, love it. All the best, Tom Henry Salem, Mass
I recently stumbled across a conversation about the Jim Brown Seaclipper 28 MK2 trimaran. Looks like the perfect combination of CC and easy simple folding system, fast and trailerable. Do you know if Jim is planning on a CC23 MK2 version with the same swing wing idea? Thx- Burk
Here’s the link to the conversation with pictures of the Seaclipper 28 MK2
http://www.cruisersforum.com/forums/f48/trimaran-especially-searunner-owners-14322-262.html
Burk, this is John Marples’ boat. He is the designer. I don’t know that he is planning a swing wing option for the CC23 or not. That is a great question though. You can reach him via his contact info on http://www.searunner.com
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new trimaran from Jim Brown/John Marples
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Very, very interesting! Don't really fancy hobbie, prindle, dart, etc rigs on trimarans but hey, at least they're widely available...
We bought a complete Hobie 16 on a trailer to cannibalize for the rig, sails, gudgeons ,etc... Sails alone would have easily exceeded the $400 spent. The Seaclipper 24 we are doing next will be built with a J-24 rig. Jim and John chose the Hobie rig for the very reason that you mentioned : availability.
That's what I thought so... I would consider such kinds of desings if I was to replace my nugget24 in a near future, but now I'm pretty much satisfied... The possibility of recycling one-design rigs is very atractive, except for the somewhat exagerated colourfulness of Hobbie's sails which I dont't particularly like...
The sails are definitely a little on the festive side, but the price was right. If you are thinking about replacing your Piver Nugget at some point, you may want to consider building John Marples' Seaclipper 24. I have a few drawings of it available for download free of charge on my website. It is the big sister of the S.C. 20 , but sports a cuddy cabin instead of the large open cockpit of the S.C. 20.
Jim Brown just released a video on Youtube of the seatrials of the Seaclipper 20 trimaran conducted here in St. Augustine.
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Take 4,000-year-old technology, add a group of 1950s radical sailors and genius engineers and you get a movement that defied sailing convention and redefined freedom. sailor, marine designer, adventurer and author jim brown has been on a 70-year high seas odyssey capturing the characters and culture of the modern multihull movement. the beyond mainstream project is cataloging and gathering jim’s vast library of photos, videos, articles and podcasts into an accessible form to share with all. and, coming soon, a documentary dedicated to this movement and the amazing cast of characters behind it..
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"During a particular period in the 20th century a bunch of non-traditional engineers and tinkerers started thinking quite differently about the traditional craft of boatbuilding, and about the conventions of society. These guys jumped right out of the western tradition, grabbed some principles from a totally different genus (aircraft) and invented a hybrid vessel with hybrid vigor. I’ll never have the wherewithal to own a J-boat, a downeaster, or a Gloucester fishing schooner, but I can own a trimaran, because it was designed for people like me to build, own and sail. That’s a pretty amazing concept in this world of specialized manufacturing, oven-baked carbon fiber race boats and the growth of the indentured class."
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Searunner Multihulls offers designs of sail and power craft by John Marples and Jim Brown, who have over 40 years of experience in multihull design. You can view their portfolio of trimarans and catamarans, from 7 to 64 feet, or purchase study plans and get design consultation and USCG certification services.
Learn about John Marples, a prolific designer and builder of sailing and power multihulls, including trimarans. He has won races, built aircraft, and participated in a Flettner rotor project.
Learn how to build a folding trimaran for the home builder with Seaclipper 16, a design by John Marples of Searunner Multihulls. The article covers the features, benefits and construction of this 15'11" vaka with two swing-arm akas.
Learn about different folding systems for multihulls to reduce beam and facilitate transport and storage. The article covers catamarans, proas, and trimarans, with examples and illustrations.
John Marples (born 1944) [1] is a multihull sailboat designer who collaborates with Jim Brown. [ 2 ] The pair are responsible for the Constant camber (1970s-present), Seaclipper (1970s-present) and Searunner [ 2 ] (1960s-1970) series of trimarans .
Seaclipper 28. The Seaclipper 28 is designed as a cruising boat, but she's not slow, she'll go over 15 knots in the right wind. Photograph by Pat O'Hara. This boat is designed for extended coastal cruising or limited offshore passages. It has ample room for two people below and will take a crowd friends on a daysail.
More at www.searunner.comJohn Marples presents the designer's own 21' daysailing trimaran, the 27' trimaran Woodenboat Design Challenge winner, a Flettner Ro...
Seaclipper 16 is a fun and easy-to-build trimaran for sailing with a friend. It has a folding system to reduce the beam to 8' for trailering and a large open cockpit with steering pedals and sail controls.
This Multihull video is about John Marples' "CC40" Trimaran using Vacum Bagged laminated Wood veneers with Epoxy /FiberGlass construction build.- Strong,...
Rikki-Tikki-Tavi is a beautifully built CC40 to a design by John Marples, developed from an earlier Searunner 40 design by the noted trimaran pioneer, Jim Brown. (But even here, later reports have described many rot issues with water infiltration into plywood). Thankfully, a small trimaran for daysailing will be a lot less work than this one.
SYZYGY is Launched. by John Marples. SYZYGY was launched at the WoodenBoat waterfront in Brooklin, Maine. She is 21′ long, 16′ beam and weighs 850 lbs with all gear aboard. The arched aka folding system reduces beam to 8'5″ wide for trailering. This is an original design but some similarities to the CC23 do exist - mostly the cockpit.
DESIGNER/BUILDER - MARPLES 35' CC35A TRIMARAN. About the Designer: John Marples and Jim Brown have collaborated for over twenty years in developing the world-class line of SEARUNNER MULTIHULLS. Jim's sense of design paired with John's technical expertise has produced more then thirty sail and powerboat designs for both commercial and private use.
John Marples recently completed the drawings of the Sea Clipper 20 a swing-wing trailerable trimaran, which Jim Brown first envisioned back in 2002. You can hear more about it on Small Trimarans. I had the honor of building the prototype for Jim, including having Jim spend the final chaotic week prior to launch working with my apprentices and ...
Picture by John Marples. IMAGE 1: SOUR GRAPES was built in the 1980s and restored and relaunched in 2013 by designer John Marples. Picture by John Marples. IMAGE 2: Seaclipper 10s and the Constant Camber 3-meters race together near Vashon Island. Picture by John Marples. IMAGE 3: The Seaclipper 10 BANANAS sailing in San Francisco Bay.
In this sample audio segment, Jim Brown speaks to multihull designer John Marples about the differences between catamarans and trimarans. ... 56 ft Lauren Williams design trimaran Home built on hard in Chula Vista ca. Needs sails and rigging, never launched. Complete pix and specs on my website ,yachtsus.com…Listed at 169000..Commission ...
John Marples Mid-Cockpit Constant Camber 35' Trimaran Plans - These are a full set of plans including support from the designer.I bought these plans with the intention to build the boat but my local building inspector wouldn't let me build a shed to build the boat.I have since found a Searunner 37 that I bought. The CC35 is an updated version of the Searunner 37.
Tweet. #5. 04-01-2015, 06:16 AM. Re: Seaclipper 4M new folding trimaran from John Marples. Plans are available, with full size bulkheads for $140. I have a Hobie Drive and a GRP moulded housing for it, so dug it out to see how it might fit. Need around 12" long, 7" high, 3" width at the bottom and 6" width at the top.
A Tupolev TU-154 aircraft landed on a runway with vehicles on it and crashed, killing 178 people. The accident was caused by poor communication and visibility, and lack of safety measures on the runway.
Circumstances: While descending to Omsk Airport, the crew encountered poor weather conditions and low visibility due to snow showers. On final, as he was unable to locate the runway, the captain abandoned the approach and initiated a go-around. Three other attempts to land were abandoned within the next minutes.
The Constant Camber 23 is a fast day-sailing sloop trimaran with central cockpit and up to 6-person capacity. This boat folds for highway trailering. Trampolines between the hulls offer seating outside the cockpit. Cuddy storage space forward of the cockpit. Pictures taken by John Marples.
Omsk Refinery is a large oil refinery plant in Omsk, Russia, owned by Gazprom Neft. It produces various oil products, including gasoline, jet fuel, bitumen, and natural gas, and complies with European emission standards.
Picture by John Marples. IMAGE 2: 3XLT built by Wayne Erickson, who is 6'6" tall and weighs 280 pounds. Big people can sail these boats too. Picture by John Marples. IMAGE 3: The fun in racing 3-meters increases with the number of boats. Picture by John Marples. IMAGE 4: All sail-control lines are led directly to the cockpit. Picture by John ...
261st Reserve Motorised Rifle Division. 261-я запасная мотострелковая дивизия. Activated 1980 in Omsk, Omsk Oblast, as a mobilisation division. Disbanded 1987. The division was maintained as a Mobilisation Division (US terms: Mobilisation Division) - manning was 0%. Equipment set present, older types, substantial ...