Multihull Structure Thoughts

Russell, I understand the dilemma between folder and swing wing tri’s. The Marples approach has been tried on a local trimaran and works in calm water folding but in any waves the “interconnecting aluminum tube” flexes and you are back to uneven loads. If the connecting tube was a larger diameter or heavier walls then it may be better. Has anyone more experience of the Marples 26 tri during folding? The Radikal system looks attractive bar the limitations already discussed.

I am only going to make a suggestion here. The Farrier system is very good and is out of patent. There are many versions of the Farrier system but the simplest I have seen has been done by Wayne Barret on this M 80 trimaran. The M 80 uses straight control arms with simple bolts through beams. This system only uses 1 extra control arm per beam and gives the full advantage of the Farrier system. The jpegs are of a Carbon fibre M 80 but a ply/wooden version of a tri and cross arms would be possible. The control arms can be aluminium or carbon fibre. The geometry is a bit tricky but not that hard. I have several plans of folding trimarans, each are straight forward engineering and able to be built by a home builder.

I am only making comment as I would love to see what you plan to build. A smaller Adagio style trimaran would be a very interesting boat. I also have admired Trinado as a fun boat. I hope you can finalise the design and get on the water in a reasonable time. A fun project.

The jpegs are Marples 26, M80 and Trinado. Additional item is Trailer Tri 18 information. This is an a wooden cross beam folding model which was replicated up to 24 foot. Its a bit complicated to build but could be simplified, especially in the metal arm structure. Also people an look at Farriers original patent at Retractable connecting beam for trimarans https://www.freepatentsonline.com/5235925.pdf which shows the concept. he also added a variation to keep the float vertical which was not used in his designs.

 

Good to see the M80. Seems like the folding system is the same as the Farrier's, with the inboard ends of the control links well inboard and down and requiring four large pockets for the control arms. The Marples 26 system seems interesting and like you said it could be far stiffer with composite tubes and struts. still requires something to hold the ama up when folding on land. A nice Adagio photo for you.

 

This is more a short read about what is possible in cruising. Alex Grimes built a Piver Nimble trimaran in England then sailed the tri from Britain to New Zealand in 1962 to 1963. Even today this is a bit of a journey and as the story tells you, there was an adventure or two along the way. The Nimble was 30 x 18 foot with a weight of 2240 lbs (optimistic), some claim 3800 lbs and a working sail area of 325 square foot of working sail area. An optional 240 square foot genoa an a 650 square foot spinnaker was available. The floats had mini fins on them for lateral resistance. The draft was 2 foot. The hard chine main hull and deep V float.

They were plywood timber builds with 9 mm plywood on the hulls, decks and bulkheads with 18 x 25 mm stringers and 19 x 65 mm chines. The forward box plywood cross beam of 450 x 225 mm. The box beam was of 9 mm plywood with 2 layers of 9mm the closer to the centre line. The aft beam was 250 x 225 mm of the same construction. Additional timber strips were added to the box beam for strength.

The actual story is at Trimaran 'Trinui' voyage 1962/63 https://grimesinc.neocities.org/ The jpegs give an idea.

 

On page 88 on this thread Tony Grainger’s Raku 35 catamaran was presented. Grainger revised the Raku 35 and renamed it to the Raku 36. The Raku 36 is 36 x 20 foot and weighs 6770 lbs with a displacement of 10030 lbs. The mast is 50.5 foot high and can be fixed aluminium to a rotating carbon fibre wing mast. The mainsail is 481 square foot, a self tacking jib of 196 square foot, a code O of 435 square foot and a gennaker of 716 square foot. The hull length to beam is 13 to 1. The draft over the rudders is 3.5 foot, daggerboards 6.9 foot or if optional low aspect ratio keels are used 3.5 foot. Twin 10 HP outboards or inboards provide the motive power. The underwing clearance is 2.4 foot. The mast is 45% from the bow.

Although the Raku 36 is 1.2 foot longer than the Raku 35 the Raku 36 weighs and displaces 1200 lbs less than the Raku 35. The rig on both cats is the same. The internal accommodation layout is similar.

The accommodation layout is good. It has a serious double berth in a good location aft of the mast on the bridge deck and 2 double berths aft. There is a toilet forward in one hull and a single berth forward in the other hull. The main cabin has 6 foot headroom where you walk and sitting headroom forward. The galley is in the hull with 6.5 foot headroom. The cockpit/main saloon entrance is large allowing the semi outdoor living area feel.

The Raku 35 structure was mainly PVC foam e glass vinylester flat panels with rounded chines. The hull bottoms are built on a male mould and mated to the flat panel hull sides and bulkheads. The Raku 36 has an upgraded structure with most of the composite surfaces are created quickly and efficiently with large CNC panels accurately manufactured to fit the boat and curved in only one plane. Moulded surfaces are used for hull shoes. Compounded hull forms give an optimise hull design for performance and comfort at sea. Producing curved surfaces does not have to be complicated, expensive, or time consuming. Compounded shapes are formed by various means including strip planking and moulding panels over temporary forms using CNC panels with just a light laminate on one side of the core that is later reinforced with an additional laminate. The panels and hull shoes are all created with PVC cores, fibreglass skins, and epoxy resins. Carbon fibre is used in the rudders, daggerboards, chainplates, forebeam, bow prodder and structural beam top and bottom caps. Similar cruising cats have 600 to 800 gsm e-glass triax on the outside 15 mm pvc foam and 600 gsm e-glass biax inside in epoxy resin, doubled e-glass below the waterline on the exterior. The bulkheads would be foam e-glass triaxle fabrics with carbon fibre in the top and bottom flanges on the bulkheads.

This is a well designed performance cruising cat that has been upgraded with modern building materials to produce a lighter cat with slightly more accommodation. The jpegs give the idea. The final 2 jpegs are not the Raku 36 but examples of Raku components that need to be assembled and taped together. Literally thousands of feet of taping, grinding and fairing.

 

In 1970 a few guys with a $100 decided they were going to build a sail boat. Their youthful enthusiasm wanted a fast boat so they decided to build a hydrofoil. The 1970 hydrofoil is a bow steering foil with 2 aft widely spread supporting foils. The concept was probably inspired by Don Niggs 1968 home built Exocet hydrofoil that was capable of foiling at 20 knots for short periods.

They began by lofting the hull as a chalk outline on the concrete garage floor. Next a 16 foot main hull structure was made of four 25 x 50 mm pine longitudinal stringers with several rectangular 6 mm marine plywood bulkheads spaced along their length. Circular holes were cut into each of the bulkhead to reduce weight. Despite trying to bend the stringers forward using hot water, it required several scarf joints to form the proper curve. The sides and transom were 6 mm plywood. The hull was inverted on sawhorses and Styrofoam was glued on the hull bottom then shaped into a semicircular canoe underbody using a disc sander. Fiberglass cloth and epoxy resin was then applied to the bottom.

Constructing the lifting hydrofoils came next. The surface-piercing, self-regulating foils would have dynamic stability without requiring moving flaps to adjust their position in the water. After considering several NACA (National Advisory Committee for Aeronautics) foil cross-sections, they decided for simplicity’s sake to use ogive sections: circular-arc upper-surface contours and flat under surfaces.

In the early 1970s, Philippine mahogany was cheap and abundant. For strength, they chose to build the foils from long, laminated wood strips. The foils needed to be tapered, necessitating a complex cutting schedule for the 250 strips to be laminated. The most innovative feature of our hydrofoil sailboat was the bow foil. The vertical “rudder” was laminated mahogany. The V-shaped bow foil assembly was made of hand-contoured aluminium plates along with a V-shaped pine “safety foil” mounted above it. The entire complex was suspended by gudgeons mated to inverted pintles attached to the plumb bow.

Two 3 meter x 50 mm aluminium electrical conduits to use as cross beams for the port and starboard main hydrofoils. These conduits acted as the spars for the main foil arms. They mated to the hull through reinforced holes traversing the beam of the hull. The circular section of the conduits allowed the main foils and their entire assemblies to pivot about the transverse horizontal axis. Rotation of these conduit beams permitted adjustment of the foils’ angle of incidence, and enabled us to rotate the foils completely out of the water.

After testing behind a towed behind a power boat the tri went back into the shop for strengthening in the cross arms before it was finally had a rig put on it for the final sail tests. The result was according to the builders “While I was near the stern clenching the joystick and Marty sat amidships trimming the sails, the wind came up to 12 knots. The bow rose and Marty moved forward to correct the fore-and-aft trim, further optimizing the foils’ angle of attack. As he sheeted in both sails, I steadied our course on a beam reach. The boat accelerated smoothly in response. The hull pitched rhythmically in the chop. Distinct vortices formed along the trailing edges of the main foils. Suddenly, as though by magic, the entire hull rose from the water and our boat shifted into another gear. The choppy ride instantly became smooth and swift as though gliding on ice.”

Not bad for the 70’s. Home made foilers with low tech material is possible. Jpegs attached give the idea.

 

And chalk instead of CAD !

 

I was trying to make these into a going concern. Sadly I couldn't find anyone who wanted to make small catamarans. The folding system is pretty easy to build. Russell, just come out to Australia, buy a medium sized car and use this anywhere you like.



If anyone wants one, there are two and I own them both. She is a lovely little cruiser.

 

Thanks for the offer, Sketcher. I have looked at that video and the folding system is brilliant, but I want a trimaran, not a catamaran. Ever since I quit proas I've been stuck with cat's. I've got two now, a motorboat and a sailboat and I want somewhere to stand up to put my pants on and cook and a bed that doesn't have to be put away every morning. And it needs space for a small wood stove for heat. We have great cruising North of here, but it can be cold.
So a folding tri is needed. I could sell the G-32 and buy an F-27, but plastic doesn't do it for me and I do seem to need good projects to sink my teeth into. Oldmulti has been throwing up folding systems for me to see, but keeps trying to talk me in to the Farrier system, so have been working on drawings with that system, but using water stays to take the sailing loads.

 

Gday Russell,

The Tramp, or Eagle in your part of the world uses simple alloy tubes for Farrier folding. Could you not base a folding mechanism on this and then have the waterstays as well? I also love tris but as I cruised mostly with a family I find the cat a great setup. My little 7 metre cat has a 1.35 metre wide double aft in the starboard hull, a toilet compartment up forward and two berths in the port hull with a big bench for a galley. Plus a massive cockpit .Great for warm water sailing with extra people, or stuff.

Then again, I think that a deep Dragonfly hinge system, with composite hinges would be pretty easy to build and will stay on the water folded. I have a had quite a bit of success with composite hinges so the loads transmitted through a Dragonfly hinge would not scare me, and Dragonflies have some quite large versions with high loads so the mechanism should not be a problem. I stitch composite tubes onto the structure with glass tow and wrap it around the tube and a backing plate, super strong.

It took me a while to realise that there are lots of different loads when folding. The front beam in my design is absolutely necessary because the "beam" mechanism does not take the rotational loads during the folding process. When extended the forebeam is redundant but try as I might I had to keep on coming back to it. Same with the aft folding beam, I tried sliders, alloy tubes, folding inwards and more but in the end went with a fold aft beam. There is a huge amount of stuffing around in developing a folding system. I would recommend putting your skills into slightly modifying a proven system like the Dragonfly or Tramp/Eagle (typical Farrier composite beams are a lot of work).

Cheers

Phil

 

The following 2 catamarans are old designs from Ray Kendrick of Teamscarab. The Siren 8.4 plans have been lost. The 950 plans were withdrawn after initial development. Both cats are of interest to many but I doubt Ray will resurrect either plan as his interest, commercial success appears to be more focused on trimarans. I would like to thank Jamez for the Siren 950 study print. The only jpeg I have of the Siren 8.4 is from an old Kendrick brochure front page. I hope there is a better study plan available.

The Siren 8.4 cruising catamaran is 27.5 x 19.5 foot displacing 3,500 lbs. The 36 foot aluminium mast carries a 395 square foot rig fractional rig. Draft ranges from 1.3 to 5 foot over the daggerboards and rudders. The hull length to beam is 11 to 1.

The 8.4 is an open bridge deck catamaran with good accommodation for its size because the hull sides are heavily flared creating good living areas. The starboard hull has 2 double berths, two settees with a table between and a galley area. Stowage is provided under the berths and both sides of the hull in the vicinity of the main beam mounting. The port hull has the same 2 double berths with a settee, navigation area, toilet, shelves and stowage areas. The accommodation to both hulls is accessed by steps through a companion way and hatch in the hull sides.

The construction is plywood, epoxy and fibreglass. Fore and aft beams are alloy tube sections while the main beam is a fabricated box section with a fairing on the forward face. If the design follows the standard Kendrick approach the hulls would have been 9 mm plywood glassed with 450 gsm biax outside and 300 gsm uni inside. The bulkheads would probably be 9 mm ply. The chines would form the equivalent of stringers. There would be a lot of taping of chines etc.

Next is the Siren 950 is a semi bridge deck catamaran. The initial Siren design was 31 x 18.2 foot with a displacement of 6,600 lbs. The 42 foot mast carries a 336 square foot mainsail and a 151 square foot jib. There is an option of a low aspect ratio keel drawing 3 foot. The hull length to beam would be about 10 to 1. The daggerboard option varies from 1.3 foot to 5 foot draft.

The accommodation has 2 double berths and 2 single berths with full headroom galley and toilet in the hulls. The large cockpit contains seating and has an optional folding top for sun and rain protection.

The construction is plywood, epoxy and fibreglass. Fore beam is an alloy tube section while the main beam and aft beam are fabricated box sections with a fairing on the forward face of the main beam. If the design follows the standard Kendrick approach the hulls would have been 9 mm plywood glassed with 450 gsm biax outside and 300 gsm uni inside. The bulkheads would probably be 9 mm ply with the main beam having 12 mm ply. There would be some stringers and a lot of deck or underwing framing. There would be a lot of taping of chines etc. The initial study plan mentioned a foam glass option which would probably be 12 mm PVC foam covered with 600 gsm biax either side with vinylester or polyester.

Both these designs would be good fast cruising cats. I hope Ray may do an upgraded version of either design. The limited jpegs give the idea. The Siren 8.4 is on the top right corner of the first jpeg. Sorry the jpeg will not rotate to the correct orientation.

 

Does anyone have any experience with Team Scarab's 7.3m Fish and Chips? The site mentions one in Russia, and the study plans have a photo of one under construction in Canada.

 

Love your origami like folding system Phil!

A very clever way to integrate a hard deck into the design.

What’s the overall beam width unfolded?

 

Thanks - she expands to about 4.8m from 2.5m. The mechanism allows extension to about 95% of folded beam.

One of the problems with many folding systems is about middle of the way through the process when the beams don't like taking load anymore. This is why I kept the fore beam. The basis for my design was to make a design that could take on Farriers in terms of utility and time for folding. I got pretty close and could be much closer if I didn't include hard floors. They were a real pain to get right. The boat is now in pieces getting another slight change to the forward panel. She is pretty close to spot on now.

Also one of the problems of beams is that they cycle from tension to compression, wiggling and making the structure move. What I did was to make the mast panel stay in compression, so there is no movement and the fore and aft folding beams are very deep to reduce movement through any slop. The boat is stiffer than an alloy 3 beam cat like a Seawind 24. Basically as stiff as if she was a composite box beam cat. Getting the mast load off the fore and aft beam was the trick there.

 

I don't know how many have been built. There was one with a much narrower beam but I don't know if he ever finished it.

What do you want to know ?

It would be easy to do in foam if you don't like ply. I'd imagine it would sail fine. I've been thinking of buying the plans just to have a look. Mr Kendrick puts a design on sale regularly. F&C was last on sale I think about 12 months ago. $150 seems a small price to pay to have the plans ?

I have a few sheets of the Kendrick siren cats but I would need his permission to share them. If the plans were complete I'd buy either design in a flash.

 

Guzzi 3, Please e-mail Ray Kendrick at Team Scarab and explain what items you have, where it would be shown and ask permission please. Ray is approachable. If what you have is a study plan or a EG a bulkhead layout he may say yes as its an old design. If it is EG a detailed cross beam plan he may refuse. No pressure just a request.

Kurt Hughes designs many multihulls from 12 foot to over 70 foot. He especially understands trimarans. Several of his personal tris were in the 30 to 40 foot range. There are racing, economy build, fixed and folding versions of the tri’s with moderate to high internal volume models at 30 to 32 foot.

The aft cabin version shown here is a sliding beam 31 foot performance cruising trimaran. The tri is 30 x 25.75 foot with a weight of 2,550 lbs and a displacement 3,950 lbs. The 37 foot aluminium or optional wood or carbon fibre wing mast has a 380 square foot mainsail, a 122 square foot jib, 352 square foot screacher and a 670 square foot spinnaker. There is a slightly bigger rig option. The main hull length t beam at the waterline is 10 to 1. The floats length to b4eam is 18 to 1. The draft is between 1.33 foot to 7.9 foot with the daggerboard down. The sliding beams allow the tri to be compressed to 13.5 foot.

The accommodation has a double aft and forward double berth cabin each with limited headroom, a reasonable enclosed toilet, a good galley and smaller dinette table area. The cockpit has the engine under. For a 30 foot tri the accommodation is good.

The build of the tri is described in the cross-section jpeg. Its basically a foam glass structure with 12 to 18 mm PVC cores with 400 to 800 gsm fabrics e glass internal or external coverings with either vinylester or epoxy resin. It would be helpful if you use vacuum bagging or resin infusion in the build to lighten the structure. The hull shapes are have many curves and will require good accurate frame type moulds for the build. The sliding aluminium beams are 185 mm outside diameter with water stays. The beams slide inside fiberglass tubes. This is a relative easy way to build a beam reducing beam system but is not the lightest system and requires a controlled folding process.

This is a good fast cruising trimaran by Kurt Hughes. The jpegs give the idea.