Multihull Structure Thoughts

Russell. I have not seen the manufacturing process and can only give a quote from the company brochure. Available at https://www.duflex.com.au/wp-content/uploads/2020/04/20191106_Duflex_Composite_Brochure_LR06.pdf

"DuFLEX® and Featherlight® panels are manufactured in a controlled environment and under-go strict Quality Inspections at all stages during the manufacturing process to ensure dimensional stability and consistent thickness. The core and laminates are co-cured in a hot press, a method that consolidates the laminate under pressure increasing the fibre volume and therefore the strength of the finished panel. The E-glass fibre content of the laminates is approximately 62% by weight. The panels are finished with peel ply to protect the laminates from contamination and to reduce the amount of preparation required prior to secondary bonding or laminating. Featherlight panels are specifically designed for non-structural applications and cores are chosen to provide superior levels of stiffness, and thermal, or acoustical, insulating properties. They are also available with sanded, calibrated hardwood veneers. These timber-faced panels are ready for decorative veneer application, painting or secondary bonding with decorative laminate."

As a follow up read Building a Catamaran.. Outgassing? https://buildacat.com/bbloggas.html and building a catamaran.. outgassing with epoxy https://buildacat.com/bblog6b.html
pages where a guy building a 40 foot cat who is also a magazine publisher had a few things to say. He was using Duflex and had a few issues. Anyone else with experience of the product?

And finally a reminder of why conversations about builds and products are important, a series of jpegs from a ship in the North Atlantic.

 

Hello Oldmulti and all friends,

you wrote:
Adrenalin ...The floats structure is unknown but either stressed plywood or strip plank cedar based on how they built Adrenalin floats. I would love to know more detail.... I looked my paper archive with a hint from my brain and found an article in Multihulls Magazine about the Multihull Symposium 1988 where Meade Gougeon said:

QUOTE: Adrenalin was built with two female molds ... we used 1/2" cedar (12,3mm) tongue and groove. During construction this was tested for failure. Ultimatly, we found that we only needed 4/10" (10,2mm) cedar. We also carboned this over by hand layup and vacuum bagged it, which was not really nessesary....

... The Amas were built a little differently. We built a mold and vacuum-bagged down intro the mold, all at one time, one layer of carbon cloth, two layers of Douglas Fir veneer and a layer of carbon cloth - very light and very strong. The all up weight of one ama is 270lbs and they are 39' long QUOTE

When I talked to Helge von der Linden, who is the german distributor of West Systems and helped building Adrenalin, he said that the Vaka was built with 15mm cedar first and was then planed down to 12mm after the distruction-testing. He also said that the carbon was 220gr/sqm (6oz.) uni vertical

See Adrenalin sailing by:

I always loved the Gougeon boats, they were very innovative with the respect for the wood in mind. I think the unique ama shapes emerged from the design and making of the wind turbine blades the Gougeons manufactured in the 1970's. Minimum surface area and the strongest structure and minimum drag with elliptical forms. I like it that the old Ollie (and Adagio???) is still rocking the party and doing this with low resistance instead of maximum power. Thats so opposite of toda's thinking where more luxury means more weight which requires more power, needing bigger amas and so on an on.
Modern Inconvienences ... Do I sound like Dick Newick? Good!!! *smile*

Have fun, Michel

 

As you get to know more about multihull boat building the more you understand that all is not as it seems. Multiplast has produced many high tech multis: Crédit Agricole III, Jet Services I, II, IV & V, Elf Aquitaine II & III, Commodore Explorer, Région Haute Normandie II, Biscuits La Trinitaine II, Club Med, Innovation Explorer, Team Adventure, Geronimo, Orange II, Groupama 3 and many more. But I saw a jpeg (first jpeg) of the crossbeam of Groupama 3 beam which has pop rivets in it, why? Does this mean sometimes you have to use metal to reinforce certain fiberglass section areas? Answer:

“The arms on Groupama are constructed in an unusual way, like an RSG, with the top and bottom sections bonded to the vertical section. It was not Multiplast that decided on that type of arm, we have not designed Groupama 3, we just made it and it was apparent that - on the curved section of the arms - there would be movement and this would lead to the sections wanting to come apart. The only solution was a mechanical one, to use rivets so the sections cannot come apart. It is the fruit of experience from Groupama 2.”

Normally Multiplast beams are designed differently; four sections are bonded to form a box and then the whole wrapped in carbon fibre.

A myth is carbon fibre does not flex well? Response from Giles Oliver: “That isn’t true, the thing that a composite structure cannot take is a big shock, like hitting a container, for example. The fact is that there are no bad materials, just bad applications of a material. Carbon, properly used, is just as good as any other material for monohulls and multihulls. The problems that EG Volvo boats had has nothing to do with the material, it was down to the workmanship.” And “when Russel Bowler (of Farr yacht design talking about Volvo boats etc) talks of problems of delamination with age, he is both right and wrong. Bowler is, however, correct about problems due to aging; old composites, which have been worked, do not have the same mechanical properties as new ones. All materials fatigue and carbon is no exception. With the right safety factor, a carbon hull will be good for 2 or 3 world tours; in the first one there should be no failures, next year there will be a risk of minor failure and, third time round, a risk of some major failure.”

Followed by: “Some people think carbon is a miracle material, but it is not; it is just better than other materials. There are no miracle materials, no bad materials, just bad choice and application of materials. If you design a round the world boat and do not take the fatigue factor into account, you are going to get failures. If you calculate correctly and build correctly you will not have failures; Orange II went round the world at an average of 22 knots and nothing failed. The problem with composites is that they don’t tolerate bad workmanship; you must be sure of your gluing, sure of your environment, sure of your air temperature, sure of your vacuum and sure of the heat you apply.”

Giles Oliver thoughts on fabrication: “We make parts for Airbus. For these we have a system of quality control and we have applied it to boats. You have to have controls; on the entry of materials, during fabrication, after fabrication, just like the aircraft industry. We test the performance of all the composites, in the laboratory, to breaking point. We never just rely on theory .... never! We are pragmatic and we only work with what we can guarantee every day, that’s why we make viable boats. For every assembly operation, samples are checked after hardening for 12 hours, so if two successive checks do not give the same result you know you have a problem.”

On the topic of moulds: “Carbon fibre; the material of mould and piece to be moulded must be the same. Carbon is not inert to temperature change, but it does not move a lot, but if you make a mould in glass fibre it could elongate 100 mm. Suppose you make a mould in metal; the entire mould dilates as it is heated. The resin in the carbon is liquid up to 80°, at 120° it is hard. Then the mould cools down to 20° and, if it is metal, that mould retracts a lot and the carbon structure inside scarcely at all so it stops the moulded part retracting. That means in some cases it gets ejected, but if you have a boat with a vertical stem it can’t get out. With our sort of multihull builds, where you have a skin, then a honeycomb then another skin and so on, there could be as many as 4 or 5 cookings of the EG hull before it is complete, so having the same material for mould and boat is essential.”

Giles Oliver and Multiplast have the track record and experience that is invaluable to us all. The first jpeg is of Groupama 3 cross beam rivets. The rest are of a few Multiplast boats.

 

I noticed an article about “healable composites” being used on a Gunboat 68. Ok, what is it and how does it work. CompPair’s produce healable composite materials that are used in the interior composite panels of the Gunboat 68, these panels if they get a dent can be repaired in two minutes without impact paintwork, reducing repair time by 99%. For boatbuilders, the benefits of HealTech panels are twofold, CompPair notes: Saving weight by using lighter panels and reducing repair time by 99%. CompPair’s solution reportedly enables Gunboat to efficiently repair an internal panel, should it get dented during construction or throughout its lifetime. Preliminary tests performed at Gunboat’s factory in La Grande-Motte, France, show that dents on HealTech panels can be repaired in two minutes without impacting the paintwork — this is in comparison to previous repair times of up to two days, in addition to other required resources and the inconvenience of immobilizing a yacht.

CompPair’s first product family is available as prepregs with different fibers and architectures. These products are compatible with current prepreg production processes. Composite structures built using HealTech™prepregs have an intrinsic healing capacity. Composite parts that have suffered matrix damage events can be repaired in-stitu in a couple minutes thanks to the prepreg technology. The healing process is very simple. The damaged area of the composite part needs to be heated at moderate temperature (100-150°C), which can be done using a heat gun, a heated blanket, an oven, etc. After a couple minutes, the part while have regained its structure and properties and can be used once again.

Contrary to current repair processes, which may compromise the integrity of the fibres (creating a weak spot) and change the weight and profile of the products (altering their performances), repair with HealTech™ results in a renewed composite structure. Recovering 100% of mechanical properties after repair, the structure also maintains its integrity, profile, and weight.

The next development is as a result of 12 years of research at EPFL in Switzerland, HealTech™ is a new type of resin giving composite materials the ability to heal cracks and delamination’s in a few minutes. Made with HealTech™, composite structures can be fully repaired on site as the parts stay structural during healing.

Translation: The prepreg panel has a “memory” and when reheated will go back to its original shape and structure. This will work on small dents etc currently but the company is trying to do “healable composites” on larger problem areas.

This is an interesting area of product development which may reduce repair times for many “knock about” charter cats etc. A description of the approach is at: https://comppair.ch/self-healing-composite-technology/

Very limited jpegs of a dented panel before and after 1 minute of heat treatment and a jpeg of the Gunboat 68 that used the panels on the interior. The web site gives more information.

 

Look at the jpegs and admire a Transatlantic trimaran. It has no motive power, no sails and this year will cross the Atlantic from Cape Verde to Barbados, a distance of 3,920 klms in about 50 days. Oh, it will be unmanned for about 12 hours per day. So back to the trimaran. It is 14 x 8.2 foot with a weight of 1,500 lbs and a displacement of 2,000 lbs. The draft ranges from 170 mm (7 inches) to 3.5 foot over the 4 daggerboards. The daggerboards can be rotated to 90 degrees to slow the tri down.

Confused? This tri is being used by a guy who intends to swim the Atlantic alone. The tri will be the support vessel that he will sleep in, feed himself, stand upright and do exercise inside for 4 hour shifts before he swims for 4 hours. He will be completely alone as there will be no other support once he starts his journey. The tri will be “blown” downwind for the entire journey across the Atlantic with its drift speed controlled by the 4 daggerboards being adjusted from fully up to fully down at o degrees to 90 degrees. I do not know if he will be tethered to the tri in any way during the swim. This is a brave adventure and I hope he makes it.

This is a new class of racing tri, raft or drift tri racers, who can cross an ocean just using the wind and currents without any sails etc. Back to the serious stuff. The guy is very well trained has done many long distance swims before and is capable of achieving this trip but it is still a very risky project.

Back to the tri. Francios Lucas did the design and the tri was built by professional boat builders in ply and epoxy with glass over the external shell. The hull shape is very simple being a box shape as it has an average speed requirement of 7 klm/hour. The construction jpegs show the framing and timber stringers. The shape is a self righting if rolled by a wave as water, battery etc storage is kept very low. The flat aft section of the hull/coachroof will provide plenty of area for any wind to push against to provide the “motive” power for the tri. I suspect there will be a lot of leaning required to understand how to control the drift direction and speed of the raft etc.

Please look at the OpenHeart web site at: OCEAN HEART https://www.ocean-heart.org/en/homepage/

This details the trip, some information about the tri and the preparation for the journey. The jpegs give the idea. Good luck.

 

Why a trimaran???
RonB.

 

Ron. I am confused as you. I suspect it is to provide a minimum movement (ie no roll) boat. A cat could achieve the same. The only other reason I could see is that the tri had to be self righting incase of bad weather and wave capsizes. A cat would be harder to design to self right but possible. With the weight of water/batteries etc a slim self righting mono would work but for a "drift" boat it needed a fat stern to catch the wind. There are no rules here as this is the first time I think someone has tried this approach, maybe we will all learn something. Good question.

 

Tri,
Greater beam overall.
Fat main hull for accommodation
Greater windage overall ?
Shorter beams easier to engineer/build.
2 cents

 

The following trimaran was designed by Philippe Rivière in the mid 1980’s. It came in 2 versions, the first a hard chine home builder version and a fiberglass round bilge production version. They share the same basic dimensions but have different builds. The Expresso 6.5 (or 22) is 21.3 x 19.7 foot with a weight of 900 lbs. The 31 foot mast carries 344 square foot in the main and jib. The draft over the daggerboard in the cockpit is about 4 foot. The rudder is a kickup on the main hull stern. The floats are relatively large for their time.

Expresso offers its crew a long cockpit (6.5 foot between the two crossbeams) on two seats either side of the main hull and extended by the side trampolines. Two berths could be accommodated in the hull; one in the bow area and the other at the rear. There could be a tent set up on the trampoline for additional comfort. The design is more a fast day sailor and a camp cruiser than a cruiser.

The home builder version is hard chine plywood and timber stringers done in epoxy saturation with glass externally. The cross beams are timber. The production version has solid e-glass polyester fiberglass hulls with epoxy e-glass balsa core decks and cockpit floor. The cross arms are aluminium tubes, with water stays.

No comments about performance beyond owners on a French blog are very happy with the performance. Considering the sail area to weight ratio and stability from the wide beam I suspect 15 plus knots on the odd occasion is very possible with light air performance being very good.

A fun machine, the jpegs give the idea. The final jpeg is of a proposal to add a cabin to an Expresso 22 which was done by one person.

 

I've been browsing for a used boat to hold me over until I finish the new one. I'd buy that Expresso if it came up for sale nearby. I wanted to buy the 25' Humdinger tri, but need an inexpensive boat that can be left on a mooring without worrying about it.
Thanks for all the Duflex info, including the negative reports. A tech that works for Gougeon was telling me that infusion works well with Balsa core, which is interesting because with infusion, the skins can be 100 percent resin-filled and not porous.
As always I really enjoy this thread and I learn a lot.

 

I've really like to pass on my Newick. It's more important that it goes to someone that knows about boats than getting top dollar. Was thinking about asking $35K. CDN.

 

Trimaran Mistral 650 https://www.facebook.com/Mistral650
https://youtube.com/channel/UC182ys_uuDv_td8L61Sjqhg?view_as=subscriber

This is about a very nice rebuild of an Expresso 650. Small cabin and semilifting foils. Mathei is a very nice guy, had contact with him when I presented his boat in my FB-group Frankencats & tris Sverige | Facebook https://www.facebook.com/groups/1192604934176635

The beams are from 100x4mm aluminium tubing.

 

We again will be talking about 2 trimarans that have a common heritage. Philippe Rivière in 1990 designed a trimaran called “Ickory” which was built and then used as the base for a limited production trimaran called the Sirius 26 C which had the same crossbeams and floats but a slightly modified main hull by Eric Magré for more comfort on board. Both boats had virtually the same dimensions. The “Ickory” was 26.25 x 21 foot with a weight of 1,460 lbs. The 35 foot aluminum mast carries 345 square foot in the main and jib. The length to beam on the main hull is about 7.5 to 1. The rudder is an underslung spade and there is a daggerboard.

In the jpegs below you will notice a slight difference in the shape of the main hull between the “Play Boat” and the “Sir” jpegs. The interior shots are of the Eric Magre Sirius 26C hull. The build shots are of the “Ickory” original design. In either case the amount of interior room is impressive for a 26 foot performance cruising trimaran. There is a genuine aft double berth, seating in the main saloon with a mini galley area and a forward cabin containing a toilet wash area and a single berth. This could be a short term cruiser for a couple.

On performance the owner of the Sirius 26C said; “First day, calm weather between 5-10 knots of wind, gliding and good, the boat lacks a bit of power in the wind holes. The next day, it's a little more serious, wind 15-20 knots with gusts to 25 knots. The boat glides, the super bulky floats give power to the boat (long live the fixed arms), their V shapes allow us to gently pass the few waves that we have crossed. Just something amazing that I had never felt before on a multi, from a certain speed (I would say around 9 knots), the central hull is relieved by a few centimetres and the boat accelerates. I'm between 9-11 knots, maybe peaks at 12 knots.” In short the tri sails well and the owner claims it is slightly slower than a F27 but does well.

The build of the main hull and floats of “Ickory” with the main hull of Sirius 26C is strip plank cedar between glass skins with epoxy. Ply is used in the cabin tops and bulkheads. The floats of the Sirius 26C are “moulded” using the “Ickory” floats as the base mould. The cross beams appear to be removable timber but I am unsure of this.

The owners of these tris are happy people but very few were built. Get one second hand and you should be happy. The first jpegs are of Ickory then Sirius 26C.

 

Hi Ron,
I don't know how to send a private message on this forum. I also don't know what Newick design you have. I can be reached at info@ptwatercraft.com. Thanks.

 

A little tour into the AC 40 monohull foilers which are going to be used in the Youth and Womens America's Cup Regattas in Barcelona, as well as by the America's Cup crews in three Preliminary Regattas. The final Preliminary Regatta and America’s Cup will be sailed in AC75's. So the AC 40 is a “mini” America’s Cup boat used for training etc. There will be 8 initially built and after that production run AC 40’s will be available for the public to buy. The AC 40 is 38.7 x 11 foot over the hull, 11.5 foot over the foils at the dock and 29 foot over the foils in full flight position. The displacement is about 4500 lbs with a very high ballast ratio in the 2 main foils. The 57.5 foot high rotating D shape mast has a double sided mainsail and a selection of headsails. The jib is 295 square foot and the mainsail is about 685 square foot mainsail.

These boats are about pure speed on an inshore “safe” course over a limited wind speed range (max winds about 30 knots). The 4 crew contain 2 helms people and 2 trimers. Most of the foiling systems on the yacht are automated and battery or hydraulic powered, the jib is self tacking, so most of the hard work is minimized and the human roll is about decision making. As these boats are also a testing platform for larger AC boats the foil shapes and software that control the foils in flight can be experimented with.

So what does all this technology mean? Speed. The team reported that the AC40 "Seems to start to lift at just over 10 knots boat speed, Estimated TWA 70 degrees Estimated speed to be fully foiling 13.5 knots boat speed". And “The AC40 was very fast, over 33 knots in less than 14 knots TWS" With “Downwind ride height was reported as "very fast but still big changes in ride height. Doing over 40 knots boat speed in under 15 knots TWS". All of this was in the first few days of testing. There is a jpeg below with the polar of an AC 40 with upwind speeds of 39 knots and downwind speeds of 44 knots. Some later reports are indicating the AC 40’ are getting close to these numbers. This is slightly slower than the AC 75’s. The GP 50 cats can hit 55 knots. All these boats can sail at up to 3 times wind speed and can sail very close to the wind.

The real way to get speed is have a good power to weight ratio with stability. It does not matter how you deploy your foils as long as the foils are far apart and are controllable. The issue for any foiler is the shape of the foils. Foils start to cavitate at about 55 knots. The 65 knot runs of the pure speed sailing machines are done with super cavitating foils which don’t work well at lower speeds.

The AC40s are built at McConaghy’s state-of-the-art production facility in China. The initial moulds were built using a 7 axis CNC machine. Each AC 40 takes 80 staff working 12 hours/day 7 days a week for 5 weeks to build (Chinese work conditions). That’s over 30,000 hours per boat. The hulls are laid up from multiple thin layers of carbon fibre for strength and weight saving. The cores are nomex, corecell and aluminum honeycomb depending on the location. McConaghy Boats in China say it’s like building ultralight racing dinghies. To ensure the accuracy of the build there is a full metal jig that is use to align all foil pins, slots etc in the hull and then after that the completed glass layup is done with the hydraulic lines etc in place then finally the internal bulkheads (positioned by the metal jig) are glassed in and the internal metal jig is removed and the deck moulding glassed on. When boats are capable of sailing at over 40 knots any miss alignments could result in a real problem.

The final jpeg is of what happens when things go wrong. Quote “Two good gybes were watched but the yacht was really starting to pull away, the chase/recon boat was doing 32-36 knots. Just before the capsize she had put over a mile on us. Going into a gybe the rudder came out and the boat pitch-poled quite hard. She capsized onto her port side, the deck just aft of the chain plate has deflected and the whole bow section has come aft about 250mm and up about 350mm.”

Jpegs give the idea.