Multihull Structure Thoughts

This is a conceptual design done by Kurt Hughes for a 100 foot container cat freighter for the Caribbean. The idea is to have a boat that can transport some containers from a major port to some outer islands on a regular basis. But there are a few considerations. Each container can weigh fully loaded 67,000 lbs. Moving these containers around require some crane assistance which will be available at a major port but at an outer island there may not be the facilities to lift the container off the cat. It would be possible to unload the container contents at an island while the container remains on the cat.

The cat proposed is 100 x about 50 foot but will require a displacement of over 340,000 lbs (150 tons). The proposed rig is a Maltese Falcon Dyna type rig. These rigs are surprising low stress (excluding the free standing masts) and close winded although with 6 masts I do not know if the interference will cause problems. Maltese Falcon rig is fully computer controlled and can be reefed by a button so a small crew is possible. No power options are mentioned.

The cat is intended for 4 crew and probably a few passengers who will have enough room to sleep and have all services provided.

The proposed construction interested me. Kurt was proposing a single skin laminate and stringers in place of hull core. The logic maybe these hulls have to be able to absorb knocks against wharfs, minor grounding etc and a thicker hull skin will handle this better.

I don’t think this design was fully developed as Kurt has done conceptual designs of bigger cargo multihulls over the last few years.

The limited jpegs give the idea.

 

Don’t know much about this cat beyond it is a Kurt Hughes design, aimed for production. The power cruising cat is going into production in Estonia. The cat was styled by Mike Schacht (designer of Evergreen biplane cat) who has a good eye.

The 44.4 x 24 foot cat weighs 7,800 lbs with a displacement of 15,500 lbs. The draft starts at 1.75 foot. The motive power will be a hybrid with “green” 4 cylinder or 6 cylinder Steyr diesel hybrid motors which drive electric motors via a battery setup.

The accommodation is a little different with a double cabin forward and large ensuite toilet and shower aft in each hull. The main saloon has a dinette, large galley, helming position and exit to a large lower cockpit. There is a flybridge capable of seating many as well as the helmsperson. I personally prefer berths at or aft of the pitch centre which is about 55% aft of the bow especially if the boat is to do real seaway work.

Construction will be foam/glass throughout. Kurt really understands how to design these structures which is the reason he can achieve a shell weight of 7,800 lbs.

The jpegs give the idea of an interesting cat. The last jpeg is the start of the production moulds.

 

The following are a couple of random jpegs I have found that were interesting. The first is a 40 foot tri that was designed about 1991-1993. The designer unknown but an interesting design. The tri was built in 1995. The size is 39.4 x 36 foot with a “displacement” of 8,000 lbs. A draft of 1.7 foot, board lifted and a 60 HP outboard engine in a well aft. 6 berths, toilet, galley and navigation table. The build is described as Strip plank cedar with foam glass carbon fibre (presumably epoxy) crossbeams. This tri looks familiar but I cannot remember where from. First jpeg.

The second design is a small tri in the last 2 jpegs. If you were to try this link you may get a set of “free” plans for the boat. I have not accessed the link. If anyone has success, please tell the thread if the plans are reasonable. It is described as a small tri. Small Multihull Free Boat Plan - CULTURA MARINARA https://culturamarinara.com/en/small-multihull-free-boat-plan/

Have a look and maybe we will learn something more about both designs.

 

I always thought the angled (Ford Anglia style) wheelhouse windows were to assist vision by reducing sun glare

 

Re the photos posted by Oldmulti in post # 3928 it is definitely not a stupid question - doing this helps a lot to reduce reflections on the forward windows at night from lights (even dim lights) in the wheelhouse, and thus to improve the visibility for the crew when underway.
A possible 'disadvantage' is that the wheelhouse structure and the windows then have to be made stronger, compared to a wheelhouse which has the front sloping aft.
If it is sloping aft, and a big wave comes over the bow, it can just carry on, over the roof, dissipating the energy in the wave slowly.
If it is sloping forward, then the direction of the wave is reversed, increasing the force on the structure of the wheelhouse.

 

This is a simple one that will require you to read a little. The boat being built is a C 50 Harryproa. The guy building it has an excellent blog which gives details of the build process. Both the good points and low points. The “Harry Hendon Saga” can be gotten to directly or via the Harryproa site, look under the C50 address and hit the “Australian” build.

The basic build process of a Harryproa has been simplified by the designer Rob Denny, and for an experienced builder they are a relatively easy build. But for first time builder there is a lot of learnings that a builder has to go through. At this time, you appreciate the support of the designer and the building community to help you through.

This guy is learning as he goes and is willing to share his experiences. Excellent.

The initial link is about an “ugly infusion” process but if you look on the left hand side you will see the rest of the blog. This is an interesting read. The Harry "Hendon" Saga: Ugly Infusion https://harryhendon.blogspot.com/2023/11/ugly-infusion.html

 

Pierre J. Kubis design has done 2 versions of a very nice 24 foot trimaran and an upgrade on the second version. The tris are fast daysailer/racing machines with some limited accommodation. The original design was done around the cockpit to allow the crew to handle sails and do manoeuvres very quickly. The accommodation was then considered. I will focus on the Blue V2 and its upgrade variation.

The “Blue V2” is 23.4 x 19.4 foot with a weight of 1760 lbs and a displacement of 2580 lbs. The sail area varies from 420 square foot with main and jib to 700 square foot with main and Code0 on the rotating wing mast. The draft ranges from 1 foot to 6 foot over the daggerboard and kickup rudder.

Organized around the cockpit the accommodation comprises of 2 cabins with a single berth forward and a double bunk on the aft. In the main “cabin” is a seat for 3 with stove and storage. Basically a coastal camp racer cruiser.

The prototype, built in collaboration with the Espace Blue Ocean shipyard, in Saint Nazaire, was built in strip planking of Red Cedar / epoxy for the central hull and foam shaped for its floats, guaranteeing unsinkability. The lifting rudder is a very nice design and has been done before on other boats.

There have been several built and used for fast fun judging from the jpegs. There are no performance figures available.

An interesting good fun tri. The blue jpegs are the original the white boat is the upgrade.

 

Pierre J. Kubis design won a naval architecture design award in 1998 with the following fast cruising trimaran “Arakhne”. It’s aimed at being a cruiser racer for 4 crew.

The tri is 32 x 25.9 foot with a guess displacement of 8,000 lbs. The 47 foot high free standing wing mast with a baleston rig (long boom that carries forward of the mast to the forestay). These rigs are self balancing and more efficient on reaching and running courses. The mainsail is 400 square foot plus the 48 square foot mast and a jib of 190 square foot. The draft is 3 foot over the fixed low aspect ratio keel and rudder on the main hull. There are daggerboards in the floats that draw 3 foot when not healed.

The accommodation is a double berth forward and aft. In the main cabin there is seating for 6, a galley and a head shower unit. The accommodation is reasonable for a couple but 4 would have to be good friends. I sailed a 36 foot tri up the coast of Australia and found 3 people was the limit of my tolerance. There was not enough circulation room. If you needed to go to the forward bunk other people needed to move or you squeezed past etc.

The concept of this tri is good and I am assuming the construction would be either strip plank cedar or foam glass. No performance figures are mentioned but I would expect 10 knot averages and speeds in excess of 16 knots.

The jpegs give the idea.

 

This is about a very transportable inflatable day sailing catamaran. The MiniCat 460 Elite is designed for a maximum of four people, the 460 Elite can also be singlehanded. The MiniCat’s builder is based in Bolevice, which is between Prague and Bratislava in the Czech Republic.

The MiniCat is 15.1 x 7.25 foot with a weight of 116 lbs. The 4 piece total of 20 foot high mast carries a sail area is 124 square foot. There is an optional 129 square foot gennaker available. The single-chamber floats are just over 15.1 foot length and have a 1.6 foot diameter. There’s a single rudder attached to the frame on centerline. In case of a grounding, it kicks up. It can also be locked in both the up or down position as needed. To minimize leeway, there are a pair of mini keels that attach to the bottom of the floats, which are in turn attached to the frame via a pocket/insert arrangement.

The entire boat packs up into 2 bags and takes about 40 minutes to assemble.

Construction includes a powder-coated aluminum frame attached to twin gray floats made of abrasion-resistant, reinforced Heytex.

This is a fun boat that can be stored in an apartment if required. The jpegs give the idea.

 

A short story that you may have read about before but we will try and analyse the tri designed for the task. The task was to be a publicity stunt. The stunt was to use a Chrysler LaBaron car to power a “boat” from Japan to the USA. Searunner Multihulls of Virginia run by designers, John Marples and Jim Brown were engaged to design the “boat” in 1982. A 54 foot trimaran was the result.

The car would be placed on a platform in the centre of the tri and the wheels were placed on rollers, the engine is then started and the wheels turn rollers that are connected by a hydraulic drive system to a 2 foot shrouded underwater propeller which powers the tri across the Pacific. OK. PS the idea was developed but the attempt to cross the Pacific did not happen.

The tri is 54 x 29 foot. The displacement is about 20,000 lbs (estimate). The main hull length to beam is 10 to 1. The draft over the rudder and prop is 3.25 foot. A forward centreboard, used to prevent the bow being blown off in crosswinds, draws 5.5 foot when down. The motive power is the LeBaron car driving rollers which drive a hydraulic pump that connects to a hydraulic motor driving the prop.

The main purpose of this tri is a publicity stunt, so accommodation was a secondary detail. There is a bunk forward, a galley room and aft of the car a navigation area and a bunk space. There is a helming station on the main deck. There is the basics of a good tri here, that could have been a big comfortable sailing cruiser. Maybe John Marples still has a few drawings laying around of the idea.

The construction is unknown but at this stage constant camber deisgns were being done so my guess is it could have been done in molded wood.

The Chrysler board decided not to go ahead with the project after some staff changes which is a pity, as I would have liked to understand the seagoing capability of the design.

The jpegs give the idea.

 

It all sounds very inefficient - and how is the car going to stay on the rollers in heavy weather?

It would be a lot more efficient to simply take the engine out of the car and hook it up (via a suitable gearbox) directly to the propeller.

And even more efficient to simply chuck the car over the side, and put a sailing rig on it instead.

 

Bajansailor. On the limited information I have the car was securely strapped down not to move in any direction. This was a publicity stunt the idea being you could "drive" a LaBaron from Japan to USA. Logic did not come into the equation. One of the problems they were thinking about was, the LeBaron car did not have a powerful engine option and by the time the hydraulics power losses were included, there was not a lot of power getting to the propeller. It was going to be a long slow voyage. The reason for the very large fuel tank on the tri. I fully agree chuck the car over the side and put a rig on the 54 foot tri, that would have been a good boat. A smaller version of Mark Hassells 64 foot "That".

 

I am still here, life has gotten in the way again back tomorrow.

 

This may be an update on a tri we have done before. In 2003/4 a conceptual design of a 40 foot aluminium trimaran design was presented. The tri was built and sailed. The following is mainly a jpeg essay but the following numbers may help.

The tri is 40 x 27.2 foot with an estimated displacement of 10,000 lbs. The about 55 foot aluminium mast carries an unknown sail area. Length to beam on the main hull is 8.25 to 1. Draft 3.3 foot over the fixed fin keel and there is small centre boards (diagrams show daggerboards) in the floats. The hull shapes are single or multichine for the main hull.

This tri is more a cruiser than a racer with good internal accommodation. There is a double berth cabin forward, a toilet shower followed by the main saloon with 2 seat/berths, a large table followed by a galley and navigation area. The large cockpit is next with a tiller steering station. The large cabin structure should provide some good protection to the helmsperson.

The construction is aluminium with frames and stringers. The chine hull shapes add rigidity as does the curved decks and roof structure. The underlying structure appears to be good but I do not have details about the crossbeams which I assume to be aluminium.

As the jpegs show this tri was built and launched but the waterline shows it to be heavier than originally designed. No performance figures but I suspect it sails well as it has the right sort of features to make it a good cruiser.

The jpegs tell the story.

 

This is about an ambitious recreation of a very famous trimaran. Pen-Duick IV was built for Eric Tabarly and designed to be the fastest trimaran in the world by Alain Allgre. It was forced to retire during its inaugural race in 1968 in the hands of Eric Tabarly. After this abandonment, Pen-Duick IV made headlines by smashing the record for the Atlantic crossing between the Canaries and the West Indies in December of the same year. This performance was followed by an unofficial entry in the Los Angeles – Honolulu race in July 1969, where Pen-Duick IV finished two days before the best monohulls, confirming its speed.

The boat was then sold to Alain Colas, a former teammate of Tabarly. Pen-Duick IV was renamed Manureva. Colas won the English Transat in 1972, breaking the event record ensuring tri’s would be a dominant force in competitive sailing. Colas reinforcing the structure and stability of the three hulls, and prepared Manureva for a solo circumnavigation of the three capes, which he completed in 1973 (with a stopover). However, the epic of Pen-Duick IV under the name of Manureva ended tragically when Alain Colas disappeared at sea on November 16, 1978, during the first edition of the Route du Rhum.

Arnaud Pennarun and the Chantier Naval de Pors-Moro (a company he is associated with) hopes to rebuild a new version of the Pen-Duick IV trimaran with Alain Colas updates and participate with it in the 2026 Route du Rhum - Destination Guadeloupe, as well as in The Transat CIC 2028.

The original Pen-Duick IV was 68.2 x 35 foot (float length 64 foot) with a displacement 14,560 lbs, after Colas strengthened and modified the tri it weighed 18,000 lbs. The original Pen-Duick had 2 aluminum fabricated wing masts which were later removed for fixed aluminum tube masts. The fore mast was 57 foot high, the aft mast was 54 foot high. The sail area upwind is 1151 square foot. The length to beam on the main hull is 12 to 1, the floats length to beam is 20 to 1. The draft ranges from 2.6 to 7.9 foot over the main hull daggerboard.

Manureva was the strengthened Pen-Duick IV with an additional forward cross beam and additional buoyancy pods placed on the forward sections of all bows. The original crossbeams had cracked at weld joints and required gussets to be inserted as well as rewelding. The original tri also nose dived when pushed hard requiring the additional buoyancy.

The construction of Pen-Duick IV was aluminum. The tri’s structure was more like an oil refinery than what we see in a modern trimaran. The main hull and floats were 4.5 mm aluminum plate with 5 stringers per side on the main hull that were 100 x 75 X 6 mm C channels. There are frames about every 1500 mm. There were 3 crossbeams of 2 aluminum top tubes and a bottom aluminum tube. The tubes are 125 mm diameter. The tubes are separated by aluminum tubes. The main sail aluminum main sheet traveller tracks are 300 mm deep x 18 mm thick and have an 18 mm thick top T section. The main mast was a 300 mm chord x 225 mm wide “wing” of 4.5 mm aluminum pop riveted onto an internal web structure. The mizzen wing mast 250 x 125 mm. Colas added an additional forward cross beam.

The performance of Pen-Duick IV and Manureva was very good for its day with 10 knot averages and peaks of over 20 knots but compared to a modern OMRA 60 footer is a slow tri. Modern 60 footers can average 25 knots and peak at over 35 knots. That has been the development over the last 50 years.

The jpegs give an idea of the tri trying to be recreated.