Multihull Structure Thoughts

The MLS Raiffeisen 5050 Fifty-Fifty team seem to think there's a future with the biplane concept. Not placing a rig on the beams does reduce loads heaps...

 

The following 2 cats, Fleury Michon VII and Charente Maritime 2, were designed in1984 by Joubert-Nivelt and built by Janneau and JF de Premorel. Charente was assembled at Pinta in La Rochelle. Both were built at the same time but differed in detail EG Fleury Michon had a fixed mast, Charente Maritime 2 had a wing mast at some point.

The cats were 95 x 43.3 foot racing catamaran with a displacement of 21,960 lbs. The mast was 91 foot to 95 foot high depending on the cat and in the case of Charente Maritime 2 was converted to a wing mast. The mainsail was 2,130 square foot, solent was 860 square foot, number 2 genoa was 1463 square foot, genoa was 1,570 square foot the drifter was 2,475 square foot and the largest spinnaker was 5,380 square foot. The hull length to beam is 25 to 1. Draft is 1.5 to 11.8 foot over the hull based daggerboards. After her racing days two 18 HP diesels were installed for charter work.

The structure of the cats was a sandwich of klegecell foam-fiberglass-polyester which was reinforced with kevlar and/or carbon fibers in high stress areas. Again, the accommodation is very limited to racing requirements.

The performance of Fleury Michon VII will give you a taste of these boats’ capabilities. Peak speeds in excess of 25 knots. On one Atlantic crossing she did 4 days of over 425 miles per day. It did a 10 day Atlantic crossing and won/placed highly in many races. These cats were capable of sailing well in all directions and very competitive in the 1980’s. Fleury Michon VII also in 1986 had a broken mast that also broke the fore beam and the starboard bow of the cat. A major rebuild was required as well as the mast being lengthened by 5 foot.

In late 1980’s Fleury Michon VII was sold into charter work and was upgraded with electric winches limited accommodation, engines etc. where it remained until it was in 2004 September 16, destroyed during the cyclone that hit Santo Domingo where it was on charter (sorry I cannot verify this).

Charente Maritime 2 was a fragile boat that had several crossbeam breakages whilst racing in the 1980’s and in 1996 had a nasty accident that damaged the cat requiring a rebuild but the cat went on to charter work.

Both interesting cats that were overtaken by trimarans by the 1990’s.

The jpegs give the idea of both sisterships.

 

Sorry about not posting yesterday but there were some computer issues. This is the final in this series of historical cats. This item indicates what can happen to some cats as they are raced, rebuilt, modified, capsized, turned into a cruiser, rebuilt, returned to its original design but “improved” etc. Yes this really has happened.

In 1984 Gahinet- Ollier designed and had built a 66 x 34.5 foot catamaran which was designed to weigh 11,200 lbs. After modifications (the stern were cut down) to fit into the 60 foot class The actual weight was between 13,400 lbs and 14,500 lbs depending on what “version” we are talking about. The various masts were about 85 foot high with some being standard tube mast and some wing masts. The draft is reported to be from 6.5 foot to 13 foot over the daggerboards.

There are multiple builders with this cat as it was rebuilt several times after racing incidents and a cruising modification. So why so many builders on a foam glass cat? Lets look at its racing history.

1984 OSTAR. Mast problems will near the lead, Had to turn around, discovered a crack in the mast foot support. Was taken to Quebec by cargo ship for the Quebec St Malo race, did not start as there was more problems. Sailed back to France.

In 1986 while going to the start of the Route de la Découverte the cat loses a piece of bow just before Gibraltar, boat abandoned, then brought back to Cadiz. The boat is brought back to the yard, where the structure of the arms and floats has been redone, the boat lengthened to 20m for the Rhum with the same mast. The cat entered Route du Rhum and came 4th out of 32 boats but broke a lower backstay.

As “Primagaz” in 1987, the cat was prepared for the Race of Europe and underwent some repairs the month before the start with the cat being shortened to 60 foot. It did not race due to insufficient funds. Later in 1987 the cat was damaged during the delivery to the Mediterranean.

In 1987/88 the central beam was redone by Nordal Mabire and François Villon. The cat entered the CSTAR and came 6th out of 95 boats with a limited sail wardrobe. In 1989 during the Nice-Lorient delivery the cat was dismasted off the coast of Portugal. It returned to Lorient and used the Route du Rhum mast. In the Lorient-St Barth race the cat capsized the day before the race finish while 6th. During the 2nd stage, The cat managed to set off again, but broke its central beam, which caused the mast to fall down.

In 1990 after a new sponsor Azurex-Saint Marc was obtained the front beam was changed and new rigging and mast were installed. The new wing mast was from the trimaran "Groupe Pierre 1er". The cat had some racing success in this configuration.

In 1994 under the name of “Omapi” new daggerboards, redone electrical circuits and new gennaker were installed.

In about 1997 a brother and sister purchased the cat and refurbished the boat into a semi cruiser with a cabin between the hulls and lengthened her to 65 foot. It was now called “Overdose”. The builder described the modifications. “I renovated this boat alone for 6 months. Complete sanding and repair of all the composite. Repairs to the trampolines. Manufacture of a centerboard (broken in two). Creation of the rear skirts. Opening of the side cockpits. Opening for installing the deck panels to access the inside of the floats. Between the central beam and the rear beam, they had a mobile home type structure made (very ugly). The stringers served as tanks.”

In 2002 the cat was sold to a new guy who converted the cat back to the 60 foot racing cat of old. Hence the name of “Original 85”. It raced relatively well for the next few years before being sold to a Dutch guy in 2011 who used it for charter for 2 summers before it was swept onto rocks from its moorings in a storm.

After over 2 years of fighting the insurance company (it’s now 2014/15) the Dutch owner Sanne Van Der Duin said this. "Hi I've taken it upon myself to restore the French cat for the last two summers. It was quite an ordeal, a 33 foot tear along starboard hull keel (vacuum infuse mono hull epoxy glass carbon and core), New bows, new sterns and new bulkheads. We hope to have her floating in march next year (2021) and are currently reinstalling all systems. Very happily because the heavy labor is past. The whole project was a lot of work, more than anticipated.”

There is a message here. The initial design of this racing cat was pushing the limits of structural knowledge at the time. Skippers in the 80’s and 90’s were pushing boats incredibly hard, result boat breakages and capsizes. At each stage of this boat evolution more powerful rigs and deeper EG daggerboards were installed to try and improve racing speed. If the designer was not consulted I can understand why there were beam breakages.

Todays designers have access to FEA with very clear testing of materials and resins. There is less gut experience and more scientific design and build processes. So don’t buy an old boat and hope it will win with an upgrade, it may be cheaper to build new.

The jpegs give an idea.

 

Part 2 Export 33, Omapi, Overdose etc cat. This is the final Dutch owners work to repair the now 60 ft cat.

 

This is about a 40 foot racing tri capable of doing and has done 300 mile days. The concept was a short handed racing tri with some accommodation. Franco Manzoli in 1999 worked on a 35 foot "Cotonella" in preparation for his third participation in the Ostar, he had to withdraw due to technical/structural problems.

In 2000, project "CotonellaTri" began , a 40-foot tri designed and built by Franco with the help of many friends. Aided by design software from French structural engineer Frank de Ryvoire, Franco designed the hulls, deck and sail plan of his new boat. Also, with the collaboration of Francesco Mura (builder and sailmaker) helped a lot. The Velscaf shipyard in Carasco which built the tri, is owned by Franco Manzoli and builds with advanced techniques and sophisticated materials having extensive knowledge of building in vacuum-cured carbon fibers. The tri was completed in 2003 with the intention of entering the 2004 OSTAR but the rights to the race were sold and it was renamed the TRANSAT. In 2005 the OSTAR was done for amateur sailors with 53 boats competing of which 8 were trimarans up to 50 foot.

In 2005 Franco Manzoli sailed Cotonella to win (first to finish) the Faraday Mill OSTAR 2005, completing the 2,800 mile course in 18 days, 21 hours, 41 minutes. He did several days of 300 miles. Cotonella’s was easy to spot as its mainsail was sporting a lady in underwear as he was sponsored by Cotonella Underwear company.

“Cotonella” is 40 x 38.7 foot with a weight of 6,720 lbs. The rotating carbon mast is 60.5 foot high and carries a 885 square foot mainsail, a 215 square foot staysail, a 580 square foot jib, 990 square foot gennaker most on Profurl furlers. The draft is 10.5 foot over the central hull daggerboard.

The build is glass, carbon, epoxy resin, Airex expanded PVC. All done in in vacuum-cured builds.

The tri has been sailed and raced up to 2023 winning many local and highly placing in EG winner of class 3 in the 2006 Route Du Rhum. After many more races it was sold to new owners who used it in local longer races and it competed in the 2018 Route Du Rhum. This is a fast 40 foot tri even today. It helps that it was very well built and light from the start.

The jpegs give the idea.

 

In Zanzibar they have a 500 km sailing race for traditional craft, Ngalawa tris and some cats. The Kraken Cup race is run over 10 days with mandatory stops overnight at some islands. The crew requires a very busy bailing person to empty the water from the main hull that is taken onboard due to the 1.3 foot freeboard. The bailing person is also responsible for feeding the sailing and crew hiking out to keep the tri upright.

The race course varies but as an EG they sail from the Northern tip of Zanibar to Tanzania. The rules are strict to prevent teams from getting lost at sea with no navigation in vessels that are not all that seaworthy. The hardest part about the event is making it to the finish line according to the organisers. But at least you can just cut down a palm tree if you break your mast. Which happened several times. There were also broken booms, fractured bones, capsizes and a late night dash over a reef to get home.

So, what are we talking about as a boat. A Ngalawa tri is a hollowed out log for the central hull with wooden crossarms that are lashed together and a a mast from EG a palm tree mast and a top yard as the leading edge of a triangular sail hand sheeted to the stern area. The float is often a flat plank slightly toed in at the bow to create lift. Additional righting moment is obtained by crew hiking out. The dimension of each Ngalawa varies according to the mango tree log used for the main hull, the strength of the cross beams and float planks. Assume the main hull length to beam is about 12 to 1. The only additional motive power is paddles. There are no centre or daggerboards so upwind work is hard.

Now as you have guested this is a relatively tough race but it has a few unusual dangers. You have fragile boats that break or capsize (it takes about an hour to right the boat and bail it out).It can be sailed in shipping lanes but there is another danger. One crew in the race had this experience: “But late on day three, as we were cruising close to shore, we learnt never to be complacent. A noise whistled over our heads and something landed with a huge splash just in front of our boat. Then another whistle and another explosion, this time just behind. Terrified that we were being shot at by pirates we cowered below the gunwale. Later on, we found out we had in fact strayed too close to the Presidential Palace and had been warned off by the mortars of the Tanzanian People’s Defence Force.”

Another quote: “Once we rounded the small headland, we were immediately hit by force six winds of up to 30 knots and rocked about by three metre swells. There was no time for food, or talking, or changing positions. For three hours straight I was stuck out on the outrigger; reeling along as the waves smashed into us, my hands raw with rope-burn. Our bucket boy Ollie was on constant bailing duty, pausing only to vomit into his bucket and send that over the side as well.”

These boats can take from 3 to 10 hours to do 50 km depending on the weather and wind direction implying speeds of 3 to 9 knot averages. These boats have been used by fishermen for hundreds of years and were not conceived for racing or outright speed. If you are brave and want fun this is the race for you. You will have up to 22 teams to race against and a lot of people to discuss life with on overnight stops.

The jpegs give the idea.

 

This is about a sail craft after the outright speed record for sailing craft. Originally I thought it was a design study but then I found that in October 2023 they were testing a prototype. (Jpegs below). So, what do we know? Not much detail but the concept is interesting.

The V-Rex is a hydrofoil based craft with a semi soft sail fractional sloop rig. The major element that is different is the aerofoil cross arms that are used to support small floats on the crossarms. There are several interesting features that become critical when you have a sailing craft hit 60 plus knots. First the hydrofoils need to be supercritical. That means the forward 50% of the foil is conventional but the back half of the foil is removed. Conventional foils only work to around 55 knots before they fail to provide lift.

Second, the wing shaped crossarms are meant to provide lift but they need flaps to adjust the lift characteristics on each side of the boat when foiling. Why, because the apparent wind when sailing forward could reach EG 80 knots which is fast enough for a glider to fly. The result is as the craft moves through the air it will need dynamic balancing. They also have water ballast tanks help keep it heeled at an angle of exactly 66 degrees whilst sailing to keep at least one crossarm wing parallel with the water. Next the rig. A semi soft wing mainsail and jib may provide the power but will need to be dynamic to adjust to wind speed variations or the helmsman will need to be very good at speed to make course adjustments to keep consistent pressure on the rig. This is where computer controls will help as the 2 crew will be busy.

The test boat had a 6 person team looking after it for 6 days of testing and they found many issues needing development. Like all such attempts it takes time to integrate all the facets of a design to get a successful outcome. In early Moth (11 ft) sailing it took several years to fully learn how to fly on foils around a course.

I hope these guys succeed in developing the 60 knot yacht they dream of as we will all learn something. The jpegs show the initial design and the prototype.

 

The following is what happens when an Australian property developer, who builds 2000 apartment multi story complexes for a living, wants to build a boat for himself and a few friends. He conceived a comfortable boat that could handle a large local bay that can turn nasty and coastal trips around Australia as required. This cat could go trans ocean if you had enough fuel, but this a bit of a problem. The peak speed of this 50 foot cruising cat is 70 knots.

The “Karve 50” is 50 x 19 foot with guesstimate displacement of 50,000 lbs (the fuel and engines weigh 15,000 lbs alone). The length to beam on the V shaped chine hulls is about 8 to 1. The draft is 2.2 foot over the hulls. Now we get to the power. Try 4 x 600hp Mercury V12 Verado outboards. There are 4 fuel tanks with a total capacity of 5800 litres.

Yes, 2400 HP to drive a 50 foot cat at 70 knots peak speed. Cruising speed is claimed to be 40 knots. If you want fuel economy you could shut down 2 engines and run on the remaining 2. The 4 fuel tanks (1 per engine) to minimize the chance of dirty fuel stopping all engines.

The final internal layout has not been finalized but up to 12 berths are possible with 2 full toilet shower combinations available. Alternate layouts will be available on request as this will be a semi custom cat built around a common hull deck superstructure.

The build is aluminum. The jpegs give the idea. The build is standard close set bulkheads with stringers and welded aluminum hull and deck skins. This cat is likely to have 5 mm hull side, 6 mm hull and underwing and 4 mm decks and superstructure (my guess not any specifications). Study the jpegs you can learn a lot about aluminum power cats. Also there are many component parts in this build which was simplified by CNC cutting of the parts. The build jpegs started in Jan 2024 with the build of the steel (yellow) strong back. The hull frame structure you see is as at July 2024. If you have the right equipment and factory space, aluminum is a fast build approach.

This is a serious boat that will cost over $US1.5 million ($2.3 mill Australian) per copy (all the 4 engines in Australia will cost close to $500,000 Australian).

The jpegs give the idea.

 

I had a need for some cordless power tools recently, specifically a drill and an angle grinder. I went to the internet to check information and reviews finding a diversity of opinions. But the real problem was the range of prices and the claims for quality.

Names like Milwaukie, Bosch, Makita, DeWalt etc are considered to be good brands but are expensive. Brands Like OZito, Ferrex (Aldi), Ryobi, Black and Decker etc are much cheaper and appear to be similar cordless power tools.

So, what is the real difference? Let’s start with a few facts. TTI industries China owns and produces the Ryobi, AEG (Ridgid) and Milwaukee brands, Black and Decker owns Dewalt and Makita owns Ozito. Ineach case there is a high end “professional” brand along side a differently named consumer brand.

Now we hit the real issue. The professional brands are very different tools to the consumer tools. I will focus on cordless power drills from here. Ozito and Black and Decker produce an 18 volt cordless power drill which looks like a Makita or a Dewalt but you need to understand some very important features. The “power” of the tool, the battery life and the service repair support.

The differences in “power” can be significant. “power” is not measured by EG 18 volts. It is measured by the Newton Meters (Nm) of torque at the drill head. An Ozito may have 50 Nm of power, the high end Milwaukee will have 140 to 160 Nm. What does this mean in the real world?

An Ozito type tool will drive a 3 inch screw into a softwood like radiata pine or Western Red Cedar. A Milwaukee will drive a 3 inch screw into hardwood that would stop a consumer Ozito 1 inch in. Even within a “professional” brand range they will have different power in there drills. EG Dewalt sell a 90 Nm drill and a 140 Nm drill. Reason is the 140 Nm is powerful but is not good at gently driving a screw in for example.

Next is the batteries. Just because a battery says “18 volt” there is a BIG difference between batteries even within a given brand. In a low end consumer brand your charge will last maybe 20 minutes of serious drilling. In professional brands an 18 volt 6 amp hour battery may last 2 to 3 hours of continuous hard drilling.

Next on batteries is the recharge and longevity of the batteries. Consumer tool battery life may be years if they are regularly charged and used rarely or if they are used every day heavily the battery may only last weeks. Professional batteries will last a lot longer if treated well, but that does not mean they hold there charge well.

In the Milwaukee brand they have 18 volt 2 amp, 4 amp, 5 amp and 6 amp batteries. The higher the amps the longer the charge and slightly more power you get. Result even within a given brand name you will have choose a battery that suits your need.

Next is service backup. Heavily used tools will break. Make sure the company has support maintenance infrastructure to repair your tool if required. Why? Because professional tools are expensive and are sold a “skins” with no batteries in a lot of cases. You buy the batteries and chargers separately. A skin may cost $300, a battery/charger combo may cost another $300. Sometimes a company may sell a kit with the skin and battery combined at a cheaper rate.

Please be careful when you select tools. If you can, buy good quality as they will be long lasting and powerful. Finally there are a lot of internet tool comparisons on the web, Youtube etc. There is also people who have "favorite" brands and support only that brand. Look widely.

 

I've worked on the warranty repair end of power tools, the pro brands are worth the money with a couple things to consider. Check out the tool brands to make sure what you'll need is offered and stick with one battery system.
Extra power is offered by brushless motors but there are bargains in brushed models for tools you use less, they may also have features you want
Don't buy a new model, wait a couple years for the bugs to get worked out. When Milwaukee first implemented their brushless system they used the same gearing as the old versions which failed under the torque. Chips went through changes to control power and battery life etc...
If you aren't around shore power batteries are a good option if you hate to listen to generators.
A good drill and oscillating multi tool are good places to start. Grinders can do some interesting things, especially with a aggressive carving /rasp type tool for wood or a flat sand pad. They do use a fair amount of juice however.
Of course planers are handy, laminate trimmers......

 

Parked out the front of Airlie Beach today, Gerald Barinks' Cactus Island. A very good-looking cat.
Biplane balestron rig with stays. I believe Gerry built up these masts with carbon over aluminium poles.
Would be great if he chimed in here and told us a bit about the rig.

 

Were you able to take any photos of her please which you could post on here?

OldMulti posted some photos and info about her on this thread in post #1150 two years ago -
Multihull Structure Thoughts https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/page-77

 

Thanks Bajansailor.
That post had all the detail I was curious about.

 

Questioning Beast (QB) is a 21 foot cruising proa built by Skip Johnson who has done several proa’s previously. Now I said cruising proa’s but Skip who is in his 80’s occasionally races his proa’s in races like the Texas 200. Skip in it for fun, if he has success good but fun is the primary goal. His previous proa was P52 which Skip built a small cabin on it for 2 single berths and a little bit of comfort. (first 3 jpegs)

QB is 21 x about 12 foot compressible to 8 foot trailering beam by sliding beams and weighs 170 lbs (hulls) and weighs 320 lbs fully assembled without rig or crew. The rig is a schooner rigged with about 180 square foot of total sail. The draft is about 0.2 foot. The main hull prismatic coefficient is 0.76 (this means a very full ended hull).

QB is basically a day sailing camp cruiser that’s good for a weekender with a large cockpit and stowage available. Skip calls it a pocket cruiser.

The build of QB is interesting using construction of Gpet sheet foam core and fiberglass. Foam is primarily 12 mm, 5 pounds per cubic foot Gpet foam (10 sheets) with one sheet of 12mm Corecell M80 for bottom panels and some scraps of 12mm Corecell M200 with the fiberglass is primarily 9 oz tooling cloth with 12 oz biaxial taping and some 22 oz unidirectional tape spot reinforcement. Skip said the 9 oz tooling cloth was a mistake; he should have used 12 oz biaxial throughout. Virtually all fiberglass work was topped off with a layer of peel ply. The hull was turned over and the bottom glassed, lapped over the bottom to just over the waterline for an 18 oz bottom. While still upside down the bottom was coated with a thick graphite/epoxy bottom coat.

The float is based on a Speer P30012 section stretched to about a 7.5% section. Rudders are straight P30012 section. Sliding cross beams are 3” x 1/8” wall 6061 aluminum tube sliding in HDPE bushings. Masts are sectional step tapered aluminum flagpoles 3” diameter base, 2” diameter cap. Sails are 4 oz Dacron with a leading edge luff of seat belt webbing. Battens are 3/8” carbon fibre tubing. Auxiliary power is an A.D. style scull with fiberglass blade and aluminum tubing shaft.

QB entered the Texas 200 in 2024 and completed half the race due to operator error according to Skip. QB worked well with only a few issues. The cross arm needed to be stiffer or a larger diameter. The steering system needed to change from pushrods to wire control as each time the rudders lifted due to weed or hit bottom the push rods were put under pressure. There were other minor things but QB sailed well and was stable in some difficult conditions.

The jpegs give the idea of a good pocket cruising proa.

 

An interesting little boat Skip has put together there.
I would love to see some video of it sailing, & hear his impressions of how his boats are developing. ?