Multihull Structure Thoughts

Another long distance cruising catamaran designed and built in Queensland Australia by Chris Mashford. Chris Mashford has designed and built many cats and tris but to give you a feel for his talents his personal 37 foot cruising tri was 330 gsm 12 mm foam 330 gsm structure. He also designed and built a 50 foot monohull bow, catamaran stern “monocat”. He is a very good and creative designer and builder. I spoke to Chris and visited Chris as he was building this cat in 1988 for an American client. Sideline. Chris flew to USA to finalise the deal and had the fly home on Sunday, no deposit or contract was done Sunday morning, Chris thought the deal was over. Then the customer said he had transferred the money into his account Sunday morning and signed the contract just before he left the US. This was 1988 and Chris was used to 5 day a week banking not 7/24 hour banking.

Back to Talaria. This is a serious luxury cruising cat that is 52 x 26 foot that displaces about 60,000 lbs with a 60 foot aluminum fixed mast and stainless steel rigging. The draft over the hull based daggerboards is 5 foot (this cat has spent a lot of its life in Florida, deep draft is not good in Florida). The engines are 2 x Yanmar 110 HP with shaft drives. Engine cruising speed is 8 knots, motor sailing cruise speed is 10 to 14 knots.

The accommodation on this cat is very good. There are 2 Single Berth cabins, 2 Double Berth cabins, 2 Queen Berth cabins and a Captain’s Cabin. There are 4 toilet showers available. The main saloon has a very large galley and saloon seating area with separate tables. The cockpit in this design is separate from the main saloon with only a connecting door. The cockpit itself has good seating and can be used for external meals etc. The accommodation spaces are large as this cat has a relatively long wing deck and bulge/upper chines on the hull providing more hull space.

I walked through this cat as it was being built. The structure is basically an epoxy glass foam sandwich which used woven rovings, biaxial and unidirectional glass in hulls, deck and bulkheads. This was a strong light structure that was well done when I saw it but it was mainly hand laid with some vacuum bagging. The timber cabinetry and interior etc was done by professional joiners etc.

As the jpegs show it would be a very good cruising cat for those who have a family and wish to see the world.

 

This is a confusing one. The 60 foot Isocatamran was claimed to be designed and built by a person in 2007 and he could manufacture more of them. Then an advertisement appeared in 2024 which said it was a Kurt Hughes 60 foot design. When I looked on the Kurt Hughes design site the closet design that approximated the hull shape was a 58 foot cruising cat design. As the design was probably done 17 years ago and Kurt evolves his designs, I will assume its an older design of his.

So lets talk about “Isokratia”. She is a 60 x 30 foot design weighing about 20,000 lbs and displacing about 34,000 lbs. The 78 foot 1.35 x 1.1 foot aluminium mast is supported by 12 mm and 16 mm stainless steel rigging and connects to 10 to 15 mm thick stainless steel chain plates. The mainsail is 950 square foot12oz fully battened, a furling jib of 310 square foot 12oz and a 5oz high cut Yankee jib. The draft over the fixed fin keels is about 4.5 foot. The bridge deck clearance is about 3.5 foot. The power is two Volvo Penta D2 75 diesel turbo engines through shaft drives.

The accommodation plan shows 4 double berth cabins with associated toilets and shows. There are 2 crew cabins in the bows. The main saloon has many seats tables and a large galley.

The build of the cat in the hulls and superstructure is vacuum bagged composite wood (core 25 mm Western Red cedar) with west system epoxy and biaxial/triaxial fabrics. The custom-designed cabinetry and furniture was built of the finest materials. The same construction methods were used for the saloon, with addition of further re-enforcing in the form of solid fiberglass strips, 100mm wide laid every 1.6 foot. This provides a firm stable structure. Things like chain plates were glassed into the structure with unidirectionals running down to the hull sides. The rudders stocks are stainless steel, whilst the rudders themselves are constructed from stainless steel plates and covered with solid foam and fiberglass. For additional security, each rudder is housed on a marine grade aluminium skeg.

This is a charter machine that could be used as a private yacht and no performance figures were shown. I am confident this cat could average 10 knots if required and would peak at near 20 knots if pushed hard in good conditions. Kurt Hughes knows how design good performing multihulls.

The jpegs give the idea.

 

This is a new production electric power cat that is a day boat that can be converted to a small cruiser as required. The Millikan Boats M9 has come from a company that has been developing electric boats since 2015, so when they release a new model it worth investigating. The “M.9” is a Vincent Lebailly Yacht Design creation that is capable of running all day at a slower speed on solar power and has a battery bank for limited night running or anchoring.

The M9 is 31.15 x 11.15 foot with a weight of 5600 lbs (including the 670 lbs of solar panels). The overall width of the cat is dependant on the fold out solar panels which can increase the overall beam to 18.95 foot. The hull length to beam is about 10 to 1. The draft is 1.45 foot empty.

Now we get to the power train. The solar panel system powering them has an output of more than 6 kW and uses both singled sided (in the central cabin roof) and “double sided” solar panels that have direct sunlight and the underside of the panel that uses reflected sunlight from the water surface. The fold out, side solar panels produce 20 percent more energy than traditional, i.e., “single-sided” central panels. The power from the panels feed into 2 x 18.9 KW batteries. The 2 Pod motors are 15 kW each, producing a power comparable to a 50 HP motor. The system has an energy management system for power flow etc. The system also has a nice feature. The M.9 is equipped with a virtual anchor feature, which thanks to a precise GPS and computerized engine management, allows it to stay in a fixed position, without having to drop anchor. With a simple click, the boat is immobilizes, which remains in its position thanks to small energy inputs in to the rotary motors. Consumption is almost zero, the virtual anchor can be used for several hours or several days.

The Millikan M9 catamaran is capable, with a day of sunshine, up to 70 miles (10-11 hours) cruising at 6 knots if the right weather conditions are available, while at a cruising speed of 9 knots you have about 3 hours of range. The maximum speed is 12 knots for a shorter period.

Accommodation. There is a cabin in each of the two hulls, in addition to the central cabin between the two hulls. The cabin in the port hull has a double cabin with a 200 x 110 cm bed, while in the starboard hull is a similar cabin and a bathroom with sink, toilet, and shower. Between the two hulls, the side panels fold down, effectively closing off the central area and creating another cabin-or common space-with about 130 square foot of floor space. There is the table, which if necessary can be closed to create a double bed (200 x 140 cm) and a kitchen outside that has a refrigerator, electric stove and sink. The other option is to have seating so the cat can act as a ferry.

The structure is foam glass in vinylester. I like the jpegs with the foil board being towed behind.

The jpegs give the idea.

 

The interesting and unusual always a item that I enjoy doing but this design is reaching even my limits of understanding. This solar powered, Fresnel Hydrofoil trimaran yacht design done by Margot Krasojević has been commissioned by HoldenManz wine estate, Cape Town.

The Fresnel Trimaran has a folding wingsail for a better lift to drag ratio, the sail’s frame is a built up mechanical structure similar to an airplane wing constructed from carbon fibre with a retractable Kevlar sail covered in aero-nautical film. The sail rotates around the mast and has a series of motorised creases which catch the wind, the wingsail is actuated by motors that control these movements using solar cells and wind energy.

The combination of the Fresnel lens and holographic film clad outrigger concentrates solar power for more of an efficient output. The form of the main hull acts as one unit with the wingsail, which wraps into the main body of the hull creating a continuous surface resulting in the motorised mast changing the shape of the sail allowing it to harness more wind. The outriggers detach to transform the yacht from racing multihull Trimaran to a cruise boat for leisure. The multi-hulls use recycled carbon fibre materials to reduce the environmental damage caused during processing new carbon fibre sheets.

The above are the publicity words. Now we try and get some understanding because the “plans” have some different words. The Fresnet tri appears to be about 100 x 45 foot with a folded controllable wingsail on about a 50 foot mast. The aluminium floats are connected by holographic outriggers to the central solar cell accommodation pod (this is what the plans say) which also has the elliptical perpetual motion sail track.

There are forward, side and aft foils under the main and side pod structure. The “floats” can be taken off and the design sailed as a foiled assisted “monohull”. If anyone actually wanted to build this design there would be a mountain of work and money to make this artistic conception into anything that would sail well.

I think you need to decide if the jpegs are anything more than art. The jpegs give the idea.

 

Hmm... was this design released on april 1 ?

 

This is about a 1987 racing tacking proa designed and built by the Cormier brothers in France. The design is very simple with single rudder and centreboard in the accommodation hull. The boat was initially known as Azurex then was renamed to Funamuble. The boat raced with some success until 1991 when it broke the rear cross beam in a race and was abandoned.

Azurex is a tacking proa with an accommodation hull and a float. The rig, rudder and daggerboard are in the accommodation hull. The proa is 54.5 x 36 foot with a displacement 9,400 lbs. The boat was later modified to 58.5 x 42.6 foot with a weight of 9,850 lbs and a displacement of 11,200 lbs. The additional beam appears to be a pod on the main hull to allow a greater rigging base and better sheeting angle. The rig dimensions are for the modified boat. The fixed 74 foot mast carries 1,930 square foot of sail area upwind and 3,870 square foot of sail area downwind. The length to beam of the hulls is 22.5 to 1. The draft is between 4.25 foot to 10.2 foot over the daggerboard.

The performance ranges from good to first places in some late 1980’s races. This tacking proa would be spectacular on one tack and downwind but a little sensitive on the other tack requiring a cautious helming approach. This tacking proa could average over 15 knots and had peaks of over 25 knots.

The construction is polyester e-glass on a foam core. This is a relatively cheap build but still light for its day. This design and build was basically a “home build”.

The final 2 jpegs shows its fate, I do not know if it was saved or reconstructed. The jpegs give the idea.

 

I don't think it was saved or reconstructed... I do seem to recall that it was a bit of a frankenboat, having originally been built using donor parts, maybe one cat and one tri hull?

I love the outside the box thinking...

Both boats that come to my my mind when thinking of tacking outriggers (calling them proas ruffles some feathers are both yellow... I don't recall if you mentioned the other one earlier, I think it was built and sailed in the Caribbean, with some success, and was ketch rigged. Apparently hit a rock racing at night, and was beached to avoid sinking, and sold as was. Can't remember the decade -70s give or take.

 

There are many variations in catamaran design and when this boat was designed and constructed in 1982 experiments were being done by many people. Gahinet-Ollier designed this cat that was constructed by Daniel Le Mene. The cat was raced between 1982 and 1987 then went into the charter trade up until about 2013. From 2013 until 2018 went racing occasionally again under a new owner who also put a central cabin on the boat and converted it to a sloop rig.

So back to EDONIL. EDONIL is a cat schooner rigged racer cruiser, originally 43.3 x 30.6 foot but was lengthened to 45.75 foot. The displacement is listed as 9600 lbs at the start but I do not know the final number. The rig started as a 2 fixed masted schooner on the main cross beams with just 2 mainsails on wishbone booms, The mainsails were 720 square foot each, for a total upwind sail area of 1440 square foot. The rig then developed with headsails on a prodder and optional spinnakers etc so the boat could have 2,840 square foot down wind. The final development was a conventional fractional single mast rig. The draft ranged from 6 foot to 8 foot over the daggerboards in its racing time as it was developed.

The accommodation was hull based at the start but after conversion to a cruiser the large central cabin would have added a lot of room.

The initial build was airex foam sandwich construction with probably polyester and wovern rovings and some biaxial fabrics. The schooner masts were claimed to be Carbon fibre but I do not know at what point they were installed in the boat. The sloop rig is a carbon fibre mast.

The original idea for the schooner rig was to make the boat easy to handle for short handed racing (and I suspect for publicity). As knowledge, skills etc improved more sail and rig components were added. The result was a reasonably fast package, but in its original rig form it could hit 18 knots, which is the reason I suspect the rig was upgraded to get better all-round performance.

An interesting design. The jpegs give the idea.

 

I exchanged emails with Kurt recently about the boat , and he claims he does not know what the boat is.
So i doubt , it is one of his designs
A father , never forget his son/s

Otherwise , i wish , boat designers own up to their designs , even if they are a mistake , because it is their creation. The boat is beautiful , perhaps a contractual disagreement.

Where did you get the information about "The 60 foot Isocatamran was claimed to be designed and built by a person in 2007 and he could manufacture more of them" ?

 

Muchtolearn. Look at this page. Catamarans,bareboat charter Greece,sailing trips,Greek island holidays,sailing vacation,luxury yacht charter https://isocatamarans.com/catamarans.html

The other source is an advertisement for the catamaran for sale recently which makes the statement it is a Kurt Hughes design. Custom ISoCatamarans 60, Used Catamarans for Sale - The Multihull Company https://www.multihullcompany.com/boat/custom-isocatamarans-60-4045810/

PS Kurt has said to me he did not know about a 45 foot cat being built in Cairns Australia. The builder told me it was a 36 foot Hughes design he had extended and he had told Kurt about the changes. That does not mean Kurt approved the changes and may be the reason why Kurt did not acknowledge the design.

 

An ocean racing biplane cat that became famous was originally named Oceanspeed was designed by Bruno Dubernet in 1981 and built by Barberet. Modification were done later by others. Oceanspeed is more commonly known by the JAZ when it was seriously ocean racing.

JAZ was a 57.8 x 33.5 foot catamaran that was designed to weigh 9,400 lbs. The cat was later lengthened to 60 foot. When it was racing its displacement was 13,200 lbs which means its weight was probably about 12,000 lbs. The most interesting part of this cat was the biplane rig. A fixed 50 foot aluminium mast was placed on each hull having its own mast head rig with a main and fore sail. The total upwind sail area was 1,720 square foot upwind and maximum sail area down wind was 5,600 square foot thanks to its massive 28 foot wide square head of the spinnaker that goes down to the deck and 2 mainsails wing on wing. The draft was 6.7 foot over the daggerboards.

This cat could sail very well under certain conditions. The best run was 380 miles in 24 hours and it could top 18 knots without a problem but it had the usual weakness of a biplane which was one rig would send turbulent air onto the leeward rig on certain points of sail. Also the massive spinnaker could not work well in fine reaching but was worked very well downwind. This rig has some advantages but also many disadvantages. One of the big disadvantages is it is expensive to set up and requires a lot of work when sailing to minimise the rigs interference.

The real advantage of a fractional sloop single mast rig is it can go upwind well and modern multihulls especially foiling multihulls can go faster than the wind speed. Therefore they are going “upwind” most of the time. Biplane rigs don’t do upwind work well.

The accommodation was limited as it was a racing boat. A later addition was the aluminum central pod used in short handed racing which has enough room for a berth, some limited cooking facilities and not much else.

The build was foam glass composite in epoxy and carbon fibre. The central pod was aluminum added later. The jpegs give the idea of the cat.

 

i exchanged emails with kurt about the 60 feet isokratia , just a week ago , i understand its advertised as a kurthughes , but its not his. Was not referring to the 45 foot cat.

perhaps the seller is riding on his name to improve the sale , perhaps builder and designer fell out. only the involved parties would know.

Can tell me more , why do you feel , it is capable of doing 20 knots ?

My gut feel , says it can do more ? maybe even 25+ knots ,
- given the 60 feet length ,
- given the shape of kurthughes narrow hull and waterline
- given that it has a 24metre mast in the link you gave.

I am trying to catch up with your thread , but it is 270+ pages long , are there any other boats like the isokratia that you could educate me on , that you have posted in this thread , that I should revisit ?

Thank you.

 

Muchtolearn. On page 1 of this thread is an index of all the boats by length. Look up the index page that has 60 foot boats in it. https://www.boatdesign.net/attachments/index-23-12-jpg.186406/ The next column is the page number. Find an entry EG Spirita on page 37 which is a fast 60 foot Crowther cruiser racer cat in foam glass. Go to the address bar above and change the page number from EG 267 to 37 and press return and you should get to the page quickly. There are a lot more cats around the 55 to 65 range that may suit your needs.

 

The following is an informative story of an F31 capsize. This is NO criticism of the boat skipper or the crew. They handled the situation well. But it indicates that you cannot take the weather for granted and being prepared is the best practice. This information is from the Farrier groups message board which has a lot of information about Farrier tris etc. I applaud Tom Clark for being so factual and honest about the incident as this helps us all understand what to watch out for.

“I've been meaning to share a post and debrief about the event. Many of you have reached out to me and asked if I would share my view of the experience. First of all I want to thank all of those in the Pensacola area that helped me right and secure Guacamaya... Serious generosity and kindness. I also want to thank all of you that reached out with words of support and encouragement.

We were participating in the Gulfport to Pensacola Race. This year was my 11th time competing in this race. 9th as skipper/owner/captain. Guacamaya had incredible crew onboard. This might have been part of our demise... a false sense of invincibility there in which we were certainly humbled. Anyway, we were leading the fleet averaging 16 - 18 knots, hitting top speeds of 22 - 23 knots. A storm brewed. A tricky storm... This was not your usual black wall heading at you, but more of a "grey out". We would have large gusts of wind and then the TWS would back off for 5- 10 -15 minutes. This happened multiple times. The wind was on our starboard quarter. Our AWS was averaging 10 - 14 knots. We had full main and spin. After constant discussion with the crew, we finally decided to drop the spin and reduce sail. In the process of doing this, we were hit by a 40-45 knot gust, the boat rounded up, and stuck/tripped over a 4-5' wave. The boat capsized in what felt like 1 second.

This was an incredibly humbling event. I can't lie or downplay it, I felt such shame and embarrassment for allowing this to happen...

1. I do this for a living. People hire me to teach them how to sail these boats. I deliver boats all over the GoM, Caribbean, Atlantic, etc..
2. I perform offshore training passages for hire, specifically multihulls. The main thing I preach is reefing, pre-emptive reefing, conservative sailing, safety, storm tactics, etc.

Ultimately, we were playing with fire and got burned.

Takeaways/Lessons Learned:

• Reef early (duhhh)
• Know your limits. Even with fantastic crew.
• Never clip into the jacklines when capsizing is a possibility.
• Wear a PLB on your PFD.
• Keep a handheld radio in the emergency locker.
• True wind data and conversions from AWS could have been useful, however, we all know when it's simply too windy without any data at all. I had AWS only.
• The main alone was enough to capsize us. The spin had pretty much no pressure in it at the time.

Overall/Notes

• My faith in these boats was actually increased. Flipped over, Guacamaya was a giant life raft. Very buoyant.
• No one on board got hurt or even a scratch for that matter.
• Worst case scenario, we flip over and float. Monohulls sink.
• Righting the boat back over was surprisingly easy, I thought.
• The boat got washed out, stripped, and will be sailing again soon.
• The jib and main can be repaired and saved.
• Will need a new spin, but it was an older hand-me-down, anyway.
• Hosing the boat out on the inside is easy and works well.

I hope to have Guacamaya back out there and racing soon. I'm looking forward to competing in this event next year, maybe SORC, and other local offshore events.

Thanks, Tom Clark Guacamaya F-31 Hull #70”

 

oldmulti , thank you.
I have started going down the list; I think I know what I will be doing this weekend ...