Multihull Structure Thoughts

Lots of similarities to my White Wings. Rudder, cross beams, cockpit arrangements, sweep of the sheer…. 5200 pounds is optimistic. Nice boat.

RonB.

 

This following is about the more conventional float shape Dick Newick trimaran called Native. The Native is 38 x 26.4 foot with a weight of 6,000 lbs and a displacement is 6,700 lbs (the crew was expected to be light and athletic). The 46.6 foot aluminium rotating mast carries a 538 square foot mainsail, a 183 square foot jib, 376 square foot genoa and a 538 square foot asymmetric spinnaker. The draft is 7 foot over the central hull daggerboard. The outboard can be from 10 to 15 HP.

The Native hull shape is very seaworthy and provides a soft ride in a seaway. This hull shape is fast but has been superseded by fuller end shapes later. The last variation of the Val design had very full ended shapes and larger floats. The Native design has a full wing or 2 crossbeam option. Most were built with full wingdeck option as it was only slightly heavier but had better tortional resistance and provided some extra internal room. The native has a single berth forward and a porta potti toilet. The main cabin has “double berths” on each wing with a “galley” and seating in the hull structure. The cockpit is functional but not spacious.

The build by Damian Mac Laughlin (Massachussetts/USA) was a cold molded wood hull (3 layers 3.2 mm) with sheet plywood decks and some underwing all done in West system epoxy. The external is covered in light glass and epoxy. The internal framing and stringers are wood with plywood bulkheads and I beams. This was fairly standard building approach of Newick tris of the 1970’s to 90’s.

The tris performance is very good on all points. To quote one owner “With 11 knots of real wind, the impression of speed is permanent, we are traveling at between 8 and 9.5 knots with great regularity against an easterly sea which is forming.” The reality is this tri can easily do 10 knot plus averages with peaks at over 20 knots. Dick Newick skill was designing tri’s that were very comfortable at speed in a seaway.

The real problem of these tri’s now is the estimated 500,000 to 600,000 Euro cost to have one of these tris professionally built today. There are other options with either more space and or speed. Nice design for its time.

The jpegs give the idea.

 

Sometimes lust overrides logic. The following Latvian tri is built by iqwoodwork web address iQwood - Sailing Trimaran https://iqwoodwork.com/iqwood/sailing_trimaran

The build of this tri is a thing of beauty. The tri is 18.35 x 12.5 foot of an unknown weight (I suspect its light judging by the canoes they also build). The 19.5 foot mast is either wooden (80 mm at base 70 mm at the top) or a 60 mm diameter x 3 mm wall aluminium tube carrying a 205 square foot genoa sail (could easily be a mainsail only rig). The draft of the tri is 1 foot over the kickup rudder and the lee board can be lowered to a draft of about 2.5 foot. Human paddling is the auxiliary power.

The tri is intended to be a day sailor for one person but could sail 2 up if required. There is storage and watertight compartments in the bow and stern.

Now to the beautiful built tri. This trimaran is handcrafted from strips of Siberian Red Cedar wood or White Oak, it is your choice. The hulls are then covered with a light layer of light fiberglass that becomes clear when bonded with watertight clear epoxy resin and is then coated with marine varnish. This combination of fiberglass and epoxy is very strong and abrasion resistant and completely transparent so that the beauty of the wood shows through while protecting it. The only issue is the need to maintain the tri and you should not leave it out in the Australian sun during summer. The leeboard structure clamps to the gunnel strips. The cross beams are removable and slot into crossbeam boxes attached to the central hull. The cross beams are laminated strip timber and are bolted to the floats. The wing planks for seating are lashed on to the cross arms.

There is no performance data but I suspect this tri is more about cruising along in lakes and rivers at a moderate speed more than racing around course. So, if you want a delightful cruiser that will attract attention when you stop you can order one on Esty at about $4600 Australian (plus $715 shipping cost to Australia) and have it delivered in about 5 weeks according to the ESTY web site.

Sorry about the limited jpegs of a beautiful tri.

 

There is a F 43 trimaran design out there. This is not a Farrier but it was known as a “Corsair 43” but it was designed by Chris Bjerragaard, a local RI sailor, and the first and only boat was built for his parents by TPI. TPI built the moulds and pulled the first boat. John Walton when he owned Corsair was also at one point the partial owner of the tri.

The problem is I do not know anything about the tri beyond it was 43 foot overall and it was built by TPI in the early 1990’s. There are various reports of the tri was well built but a bit overweight due to the construction processes at the time. One person said: “There was a full set of production tooling made by TPI and the boat was advertised and promoted as a production boat, I think under the TPI name. I remember going aboard the boat at a boat show (probably Newport) and I have a brochure.”

There was good accommodation for its size and it had enough room in the floats to store a kayak.

The build was foam glass and according to another person: “Gel coat, chopped mat, puttied-in interior liners and other build methods that are used to provide glossy low-maintenance surfaces that can be built in a modest number of man-hours do not work out so well with multihulls which have lots of surface area and need to be kept light. Too bad, as a remember the boat was attractive and had plenty of accommodations for coastwise cruising.”

The tri known as “Triple Treat” is still racing and cruising. The jpegs show her sailing and there was mentioned she had entered over 30 local and offshore races with some success .

I would like to know more if anyone has further information. Sorry about the limited jpegs of a very interesting tri.

 

The following is a description of a design that Kurt Hughes says “I cant believe that I have been lured into designing a new millennium Searunner”. Kurt had done a trimaran design called the D32 but an old friend of 30 years said he wanted a centre cockpit design like the old Searunners and with the 2019 Wooden Boat Festival coming up Kurt did some concept sketches for presentation. The jpegs are presented below.

There are few details of the 31 foot centre cockpit but what we know is it has sliding beams to reduce the beam for marina’s etc. It has a fractional sloop rig. There is a deep daggerboard that is in the cockpit and there is a kickup rudder. The 31 has a 9.9 HP outboard for power. Now we get to the advantage/disadvantages of the central cockpit. The advantage is the cockpit is the safest and most comfortable position under way and heavy weights like water tanks etc can be below the cockpit floor. Also, the 31 foot tri is basically divided into 2 living zones for privacy.

The downside is that the “largest widest” part of the main hull is used for the cockpit, not accommodation. The accommodation is separated so EG the bow has a double berth and a toilet area then the aft accommodation has the galley, seating and some berths. Also, the cross beam sliding structure interferes with headroom in both accommodation areas. Jim Browns Searunner 31 had similar issues but hundreds were built and appreciated by their owners.

The structure of the Hughes 31 is flat panels of ply and cored composites for the multi chine stepped main hull. The floats are CM developed plywood. The cross beams are aluminum and waterstays for a faster build. Detailed plans were not done to my knowledge but the design created a lot of interest.

The Hughes D32 tri was done several years before the conceptual Hughes 31 centre concept. The D32 is similar being 32.25 x 27.75 foot capable of being compressed to 13.5 foot for marinas etc. The floats and beams can be disassembled for transport (crane required stuff). The weight is 2,650 lbs with a displacement is 4,190 lbs. The 42 foot aluminum mast carries a 381 square foot mainsail, 131 square foot blade jib, a 210 square foot Genoa and a 675 square foot spinnaker. The length to beam on the main hull is 9.5 to 1.The draft is 1.2 foot to 7.1 foot over the daggerboard and kickup rudder. The outboard power is 10 HP.

The accommodation provides a fore and aft double berth with a toilet area forward. The main saloon has a large galley and a large seating dinette area. The cockpit is aft and sensible size. The build of the demountable D32 trimaran can be built in developed plywood or composite materials. Even if built with ply/epoxy, it uses core materials to make the large panels stiff. The connectives are of aluminum tubes and stainless steel wire. That speeds up construction considerably. The tubes can be one piece, or a pair front and back, to slide past one another. That lets the tri get skinny in a marina. Many D32’s have been built.

The jpegs give you the idea of similar designs that allow you to choose your interior options. The 31 footer looks better but the D32 is a very functional design that has proven to sail very well on all points of sail.

 

Bit of the bread box elements there, the D32 especially. The center cockpit boat is actually reminiscent of the Newick Argonauta with the raised stern cabin profile.
I'd take the Searunner 31 with a vented wingdeck, much better looking, the centerboard is better for gunkholing and..... the plans are done!

 

The Trice 3 is a mid cockpit Newick bread box, the 37 foot length gives you more to work with but the stern treatment reduces the box effect.

 

The following is about a small very high performance racing trimaran that was designed by Darren Newton. The tri was designed on a low budget for a paraplegic sailor Alan Grice to enter the 1998 Royal Western Yacht Club’s two-handed Round Britain and Ireland Race. Paradox is 30 x 24.5 foot with an unknown weight. The initial rig had a 40 foot aluminium mast but later had a 45 foot carbon fibre mast with an unknown sail area. Each float has a daggerboard and an underslung rudder in it. The engine is a 9.9 HP outboard.

The accommodation wa designed for the requirements of racing and a disabled crew. There is a single berth under the cockpit and a single harbour berth forward. The main cabin has a bench seat on one side with a bench for a “galley” and navigation on the other side. In short minimal accommodation and weight for racing.

The build is hulls in foam e-glass (the boat was built with a tight budget) in moulds. The crossbeams are aluminium.

So how did the tri go? On the second day of initial trials Paradox hit 21 knots and could sail really well on all points. It retired in the 1998 Round Britian race. It was sold to Simon and Matt Baker in 2001. In 2005 it was T boned by a mono a day before the 2005 Fastnet It was repaired and raced well. Will Claxton and Matt Gill, 2 boat builders then purchased Paradox who extended the tri to 32 foot and changed the rig. So how did it sail, you say. Paradox went on to become the 3 times class and handicap winner of The Round Britain and Ireland race. She also came 2nd in class in the Fastnet as well as winning her class in the Round the Island race. Paradox also won her class in the 2010 Fastnet, sailed by Will Claxton and Matt Gill. It was sold to Italy in 2016 she is now available for day charter. Yes it could sail very well.

This is a very good design. The jpegs give the idea.

 

Cavalier Mk2 said he thought that the Searunner 31 vented wing was a great mid cockpit trimaran. With about 400 Searunner 31’s built since 1972, mainly by amateurs, they certainly meet a lot of peoples needs. There were 3 versions of the Searunner 31. All have the same central hull (same accommodation) and float shape but you could choose a full fixed wing deck, a vented fixed wing deck or an A frame cross arm structure that allowed the Searunner 31 to be disassembled or rebuilt for transport (crane required).

The 31 is 31.2 x 18.66 foot (some were stretched to 20 foot) with a weight of 5,600 lbs and a displacement of 7,000 lbs. The payload was limited to 1,400 lbs. The 35 foot wooden square mast was 191 x 102 mm with a cutter rig. The mainsail is 195 square foot, the fore triangle is 255 square foot fore a “total” area of 453 square foot. Genoa’s and spinnakers increase the area a lot. The float length is 27.2 foot with a float beam of 2.45 foot. The floats have 200 % buoyancy. The length to beam on the main hull at the waterline is 7 to 1. The float length to beam when under pressure is 12 to 1. The draft over the hull is 1.9 foot, with an external “worm shoe” 2.75 foot and over the centreboard 5 .75 foot. The engine is normally a 10 HP outboard but can go to 20 HP as long as the engine props etc weigh under 200 lbs. The speed with a 10 HP is 6 knots.

The accommodation is controlled by the mid cockpit. In the bow is storage and a toilet area with room for a shower. Next is the head of 2 single bunks that extend under the seats of the central cockpit. Next is a spacious cockpit. Aft in a separate cabin is the galley either side of a central standing area followed by a dinette that can convert to a double berth. Under the central cockpit is water tanks, heavy storage or a light inboard engine. The major structure under the cockpit is the central centreboard which was very important to the success of the Searunner series.

Now to the Searunner design approach. In the 1960’s Piver trimaran were all the rage. Jim Brown wanted to improve the sea going capabilities of trimarans and had experimented with some smaller tri’s with V bottom floats that had chine, the main hull had a multi chine hull and more importantly deep centreboards. The hulls also had fuller end main hulls and cutter rigs. The length to beam of Pivers main hulls were 6 to 1 but Jim designed 7 to 1 main hulls. The result was the Searunner series could sail faster, point higher and were a lot more comfortable in a seaway than a Piver trimaran of similar size. They were a revelation for there time and Jim got the basic concept of future trimaran design very correct. Yes, modern tris are lighter, have wider beams and have bigger rigs but Jim Brown designs skills started these developments.

Now to the structure. The Searunner 31 was designed with plywood and timber with either timber cross beams or aluminium A frame cross beam structure. The main hull has a 12 mm bottom panel (or 18 mm if there is no worm shoe), 9 mm side chine plates and 6 mm topside hull panels. There are 7 bulkheads, a stem and a transom in the 31 foot main hull. The 6 mm plywood floats have the same number of bulkheads etc as the main hull. There are stringers in the hulls but the main building change was the fiberglass taped seams on the chine lines. The outside of the hulls had light fiberglass over them. Now we come to a problem of the early Searunner 31’s. This was time of polyester resin, epoxy was only just appearing and expensive. Result many early 31’s had fiberglass polyester chines and external fiberglass polyester covering. If well panted and maintained this did not cause to much problem but if not well maintained problems like EG wood rot occurred.

The crossbeam structure was a plywood sandwich with timber framing inside. The aluminium A frames were mainly 50 x 50 mm with 4 mm walls were bolted to the hulls and there were timber fore and aft struts to strengthen the structure. There was also in the vented wing version a set of stainless steel plates that could connect the cross beam float combination to the main hull. This could be disassembled later. The decks are 9 mm and 6 mm plywood.

The performance of the Searunner 31’s was a 5 to 7 knot average sort of boat with peaks around 15 knots in cruising mode. Some reports claim 9 knot averages when pushed. Upwind performance is good, although the Searunner 31 and 37 hobby horsed in some conditions. The last design done in the Searunner series, the Searunner 34, was a design improvement in accommodation, structure and performance.

The jpegs give the idea of an excellent early design. Well done Jim Brown, who built a Searunner 31 for his personal use in 1972. After 30 plus years of Jims ownership it was sold to a guy who is still cruising “Scrimshaw” in the Caribbean.

 

Thank you Old Multi, that is a great look at the 31. For any boat to be a Searunner substitute it has to be able to be built with average construction skills/methods without exotic materials.

These are cruising boats first that happen to be trimarans with the multihull advantages of more level sailing and shoal draft, some more speed can be there than the average monohull cruiser but that isn't the primary purpose.

One other mid cockpit cruiser I like is one of Norm Cross' last designs, the Cross 10.5. It is about the size of the Searunner 34 but with a shallow keel for those who don't want the extra work of keeping up a centerboard with it's trunk etc....
It also adds a feature important to me, the bunks have the sleepers feet pointed forward towards the bow. If you ever hit anything you'll know why I like this. They are also in the stern along with the head which has less motion for rest, kind of a Heavenly Twins cat layout in a tri.

Jeff Turner has made Cross plans available again and Searunner plans can still be bought from John Marples.

 

For those who would like to understand the differences, benefits of Searunners versus Cross trimarans the following thread was an interesting one a decade ago. Searunner or Norman Cross - Cruisers & Sailing Forums https://www.cruisersforum.com/forums/f48/searunner-or-norman-cross-80255.html

 

Well there's a blast from the past! All good boats, just check carefully for materials and condition.

To be fair about the Kurt Hughes boats, in that size range it is hard to get room without looking boxy, Phil Bolger embraced the box and it served him well.

Of course that Trice 3 does show what some curves can do.....

 

The Bali Catsmart is the smallest, full bridge deck cruising catamaran from Bali (offshoot of Catana) and was designed by Olivier Poncin, had the interior design done by Piaton-Bercault, naval architecture done by Xavier Faÿ and built by CATANA. You can tell this is a pure French production machine driven market research and desires. Translation: more space, lots of air-conditioned comfort, multiple berths and bathrooms with some pace. The Catsmart maybe the smallest catamaran from the Bali shipyard but its optimal use of spaces provides very good habitability for a cruiser.

The Bali catsmart is 37.2 x 21.2 foot (hull length, length over all is 39.5 foot over prodder) with a weight of 17,637 lbs and a maximum displacement of 27,100 lbs. The 47 foot fractional rigged mast has a sail area of 818 square foot in the standard main and self tacking jib and a maximum sail area with genoa of 1,076 square foot. Length to beam on waterline about 7.5 to 1. The maximum draft is 3.6 foot over the fixed fin keels. The standard engines are 2 x 20 HP diesels.

The statement by Bali says a lot: “The BALI CASTMART, with its 38 feet, remains faithful to the DNA of the brand, with the “BALI door” and the fully decked forward cockpit which have made it famous. This model also offers a double helm station making manoeuvring and steering easier. A boat perfectly suited to pleasure boating and family time at anchor.”

The interior main feature initiated by Bali is the cockpit is separated from the saloon by a large tilting door which fits perfectly into the roof when open. The saloon, galley and cockpit are brought together in a single space, providing a large “saloon” space. In order to meet the needs of the rental market, the Catsmart can be fitted out in a 3 or 4 cabin version, with a bathroom in each hull. An alternative is offered that is an owners version, with a double cabin and large forward bathroom/toilet in each hull. The kitchen occupies the entire width of the saloon, and offers a superb work surface. Numerous storage volumes, as well as a fridge and a freezer, confirm the program of this cruiser.

The build of these cats is pretty standard with foam e-glass in vinylester everywhere and carbon fibre reinforcement in bulkheads and some other areas as required.

The performance is not the highest priority but this cat can still do 8 knot averages with 16 knot type of peaks. It sails well on all points but needs a little engine help in very light winds. In short, an excellent cruiser or charter cat with great load carrying capacity but it is not a racer.

The jpegs give the idea.

 

This is about 2 catamarans with the same hulls and rigs. Kurt Hughes designed many years ago a 30 foot open bridge deck catamaran and later redesigned the cat to be a tube catamaran. In both cases the same hulls shape, rig and construction (crossbeams different) is used. The open bridge deck version is 30.1 x 20.2 foot with a weight of 2,950 lbs and a displacement of 5,800 lbs. The 37 foot aluminium rotating mast carries a 300 square foot mainsail, a 143 square blade self tacking jib, a 231 square foot genoa and a 400 square foot asymmetric spinnaker. The length to beam is 11.3 to 1. The draft over the hull is 1.4 foot and 5.8 foot over the daggerboards and kickup rudders. The underwing clearance is 2.9 foot in the bridge deck version.

The tube cat version is 30.1 x 20.2 foot with a weight of 2,250 lbs and a displacement of 4,800 lbs. The rig is the same as is the draft but the underwing clearance is 3.8 foot. The engine is an outboard of 20 HP or 2 x 10 HP outboards.

Both these cats are high performance simple 30' cruising catamaran with full standing headroom in the hulls, but is aerodynamic enough to give great windward performance. Both models have 2 double berths, a galley, internal seating area and separate toilet. If you are very friendly a couple could cruise a long time on these cats but they are warm water boats not built for sailing in the Artic (Opps, one of the first open bridge deck 30 footers was built in Alaska). The jpegs below give more insite.

Now to the point of this post. The build is done by CM (cylinder molding) using plywood and timber. The work in the hulls and hull decks are exactly the same. The only difference is the cross beam structure. One has a full plywood crossbeam bulkhead structure, the other has simple aluminium cross beams. The choice is yours but the real consideration is the availability of the aluminium cross beam tubes. The build differences are small and we reach the underlying issue. You could put either of these designs together in 2000 hours if you were experienced and have a good building facility with the right equipment. Or it could take 5000 hours if you wanted perfection or you are inexperienced. The design choice in theory should be based on a simple build and minimal components. Reality is “simple builds” of EG aluminium cross beams need a lot of work in the installation points in hulls, attaching of nets and deck gear to beams, provision of headsail track attachment points etc. Simple builds are often as time consuming and expensive as a fuller structural build.

The actual structure of the hulls is 2 layers of 3 mm plywood on a simple mould then the 30 foot long curved plywood sheets are cut to a hull side sheet. The 2 hull side sheets are joined at the keel line then forced into a deck flange to torture the hull into shape. Then bulkheads and stringers are inserted into the hull. The decks and crossbeams are standard build approach. This approach is just a “large Tornado” and uses a lot of epoxy and glass to do the keel lines. Quite a few of these cats have been built and are sailing in many locations. Some are used for charter.

I have only read a few performance reports but we are talking about a cat capable of 8 to 10 knot averages and peaks near 20 knots. The tube version is the faster option but the difference will not be significant.

The jpegs will give the idea (probable over 2 entries with the build second).

 

Part 2 Hughes 30 cat. Build.