Multihull Structure Thoughts

Peterbike. Use google and ask "Questioning Beast sailing proa" it should lead you to a couple of pages in which Skip describes the build and another about his Texas 2024 adventures.

 

It will be a while before I get some video of sailing, age and other projects and responsibilities need some attention. I'm quite happy with the boat as is, look forward to more development.

 

Thanks for posting something about my current project, it's an honor to be here. Two minor points; the Texas 200 is more a raid than a race, a cruise in company. Also the cross arms are fine, the problem is the three planks spanning between them are woefully inadequate, an failed exercise in structural minimalism.

 

Milton "Skip" Johnson in 2000 entered a design competition and the following is the result. Its different and was not built to my knowledge but has many idea’s worth exploration. The name is Questioning Beast 1 (QB1). QB I is basically an oversized canoe fitted with a Birdwatcher style superstructure (slot in the roof with a sliding canvas covering to allow a person to walk upright).

QB1 is 21.3 x 12.1 foot that can be folded to 7 foot. The main hull is 6 foot wide with a 4.6 foot waterline beam. The length to beam on the main hull is 4.33 to 1. The weight was to be 900 lbs with a displacement of 1,500 lbs. The mast height is 18 foot with a reefable tacking triangular sail of 160 square foot. The hull draft was 0.66 foot increasing to 1.66 foot when heeled to 20 degrees. Additional power appears to be an electric outboard.

The accommodation is basically bench seats on either side of the main cabin with sufficient space for a portapotti and camp kitchen with some stowage. This would be a reasonable weekend camp cruiser.

Now we get on to the proposed construction. The main hull has 5 permanent bulkheads of 9mm ply, pre-finished, plus temporary frames of 15 mm particle board or equivalent at 16" o.c. provide the form for strip plank 9 x 25 mm western cedar strips. Once faired, outside of hull is covered with 12 oz biaxial glass, 2 layers on bottom and stem. Turned over, inside is covered with one layer 8.5 oz. unidirectional across hull with epoxy/wood flour fillets at bulkheads and ends. Interior hull stripping to be left finished clear, balance of boat to be paint finish. The foils are built from 6mm ply like a large model airplane wing (Ogive section, arc of a circle about 12% thick). Pre-finish framing and interior of skins, then assemble. Pivots are based on 1/2" S.S. rods with braces fabricated from 7/8" S.S. tubing and standard bimini top hardware fittings. Strategically placed foam pads and heavy shock cord straps should keep the lee foils tucked in for trailering, and be quick and easy-to fold out at the boat ramp.

The mast is to be built up from timber in an octagonal ‘birdmouth’ section, 6" diameter, heavily tapered, finished weight about 40 ibs. That’s too heavy, but with roller at the bow and gallows, you should never have to handle the whole weight. An alternative would be a foam or very thin wall wood section with carbon fibre skin but only if needed. Rudder is fairly conventional, laminated up from several layers of plywood.

This craft has many ideas worth a second look, pity it wasn’t built as we all could have learnt something. The fat central hull would have been interesting to find out its performance limits. I was surprised when I sailed on an early Piver and a Trailer Tri 18 as to how well they sailed in light to moderate airs. There peak speed was not to high but there average speed was good for their size. The limited jpegs give the idea.

 

Barink posts on Sailing Anarchy as "he b gb" and has posted lots of photos and information on "Cactus Island" and shared plenty of other tidbits of wisdom. Use the search function. Here's a video.

 

Reminds me a little of the "X-Wing Racer" that Sean Langman said he was going to build for the Sydney to Hobart years ago, possibly before the internet was the tool it is today, I think I saw drawings in sailing magazines. I can't find anything on google at this point.

 

Quite a lot of aero and hydro skin friction going on there.

 

Gordano Goose is a very famous tri because of the designer and part time builder Nigel Irens. This tri was conceived as a pure racer with limited accommodation. It was designed in 1981 and was a product of its time. Low weight, narrow hulls, reasonable sail area for weight etc but the stern shape on all 3 hulls gives away the design age. At this stage Dick Newicks tris were fast and sea capable so other designers followed the general concept. As Nigel Irens sailed many sea miles he evolved the hull shapes dramatically into the full ended hull shapes with floats that almost have the same underwater shape as the main hull. Now with foils float hull shapes have evolved again.

Gordano Goose is 40 x 29 foot with a weight between 4,200 lbs to 5,000 lbs depending on what stage of life it was measured. There is a fixed aluminium 51 foot high mast that carries 754 square foot of sail upwind. The length to beam on the main hull is 11 to 1. The float length to beam under pressure is 13.5 to 1. The draft is 3.2 foot to 6.8 foot with the central hull daggerboard down. The engine is an 8 HP outboard.

The performance of this tri was good with 2 OSTARs, 2 Routes du Rhum and Round Britain races with many other local races under its belt. It may not have placed high in the overall results but it was successful in its class. It also had a few DNF due to things like broken rudders etc.

In September 1997, Gordano Goose, capsized off the Balearic Islands. Then after being righted, the boat is brought back to Minorca. In 2007 Gordano Goose escapes a bulldozer and is brought back to Port Leucate under jury rig. The tri was then refurbished (read rebuilt) and by 2015 it was ready for sailing again minus a mast and few details. It was sold for 20,000 euro’s. In 2018 the tri was fully restored to its original as first built condition and went sailing. Dedication by some owners who did a lot of work themselves on a limited budget and a very interesting original build.

The construction was a combination of PVC foam glass hulls with plywood/wood decks. The crossarms had some carbon in them. But to show the dedication to weight saving that Nigel Irens was into, the deck stingers were triangular shape with a carbon cap on the point of the triangle (wide side glued to the ply). This many have saved a couple of lbs per deck stringer but reduced weight was more important than the increased amount of work.

The jpegs give the idea.

 

I have a couple more photos of Gordano Goose.

 

Sorry about the crazy uploads.

 

The following Atlantic proa was designed in 1980 by Gilles Ollier. The builder was Guy DELAGE who owned the proa for 13 years of racing before the boat needed to be sold as part of a divorce. The proa had many names Hydropholie, Metabo, Lestra Sport, Sudinox, Francofolies and FUNANBULE. This proa was basically a racer having competed in transatlantic, Twostar Europe, Double-handed Transat, Route du Rhum and many local races.

This Atlantic proa was fast proa with a speed of 23.23 knots over a measured course. Its peak speed according to Guy DELAGE was 38 knots. Any boat that can average 12 knots transatlantic is good. This proa was better at longer course sailing than around the bouys and when it was on some points of sail was very fast due to being an Atlantic proa. Alantic proa’s have the stability of a trimaran without have the weight or windage of the “windward float”. The power to weight to stability ratio’s you can achieve are very good.

The proa was originally 55.8 foot but was lengthened later in life to 60 foot. The beam is 26.3 foot with a displacement of between 8,500 lbs and 10,000 lbs depending on its stage of life. The rig is a schooner with two 60 foot aluminium masts and an upwind area of 1,506 square foot with a 2,256 square foot spinnaker available. The length to beam on the mast hull is about 12 to 1 and the float has a length to beam of 18 to 1. The draft ranged from 3 foot to 7.8 foot over the mast hull daggerboard.

The accommodation has 1 double berth, a limited galley, toilet and some seating.

The build is claimed to be Airex foam, glass and carbon fibre in epoxy but Guy Delage, who built the boat, on his page says its Airex foam, glass and polyester resin. Either way its relatively light for its length. The proa had several issues such as broken rudder, lost its daggerboard out of its slot, was dismasted etc. The majority of these accidents happened during racing. The final issue was in 2012 the proa lost at anchor in Dakar after the La Baule Dakar race.

The jpegs give the idea.

 

Sorry guys, no entry today a little busy.

 

This is about a 1985 Lombard designed racing cat that was built by KRB in La Rochelle. The cat under many names was launched in 1985 and raced often and widely. It also was rebuilt at least 3 times due to various incidents and is still being used as a charter cat today.

The cat known as LEJABY RASUREL 2, GROUPE LG, and later in life Llampec Grillat, GRYLLOS, Ile et Elle is 60 x 38 foot but after one accident was narrowed to 36 foot beam. Its displacement was between 10,750 and 12,320 lbs depending on the version we are dealing with. The 76 foot mast was aluminium and changed over to a cardon fibre mast later. Upwind the sail area was 2,400 square foot, downwind the sail area was 4,720 square foot. The draft ranged from 2 to 9.9 foot over the hull based daggerboards. There were foils placed on the front of each hull to provide “lift”. Tried many times but they can also minimise the bow lifting quickly if at the angle of attack resulting in a tripping moment.

This is a racer and did not have much accommodation beyond the central, pod which contained 2 berths, some seating and minimal galley. Later the pod area was modified to provide full headroom, a toilet area for cruising and/or charter work. This cat had limited accommodation even when cruising.

The build of this cat was Divinycell, carbon and epoxy mainly. Most of the structure was vacuum bagged unidirectional carbon fibre that was post cured at about 45 to 50 degrees Celsius. The main mast cross beam was also a unidirectional carbon foam structure in epoxy. The only problem was in the initial 38 foot beam build the mast pressure caused the beam to flex which resulted in the mast falling down (1986) braking the forebeam. The cat was repaired but had its beam reduced to 36 foot as part of the repair, strengthening work.

This cat was an ocean racing winner with EG In 1987 Race of Europe the cat was 1st out of 5 Class 2 multihulls after winning all the stages in class 2. In 1989 it won the class 2 section of the Tour de Europe. But it was also fragile, as GROUPE LG in the 1989 Route du Rhum its mast fell down.

A carbon mast was installed in 1989 and the cat was very successful racing until it was dismasted in 1990 whilst racing and abandoned. In 1991 the wreck was brought back to France by a Spanish trawler. The cat was repaired and converted into a cruiser named Llampec Grillat.

In 2003 the cat dragged anchor in a storm and was washed up onto a rocky beach and again was repaired. The cat was now turned into a charter cat by the name of “Ile et Elle” and is still operating today from what I know.

This is an interesting cat that was advanced for its time and could sail well with very good sailors onboard. But the design pushed the knowledge of materials and structures of the time and had issues. It amazing as to the dedication of people to bring boats back to life after accidents.

The jpegs give an idea.

 

Arkema produce Elium®, thermoplastic resins that are recyclable and have the following characteristics:

• Formulation: Elium® is a acrylic base polymer diluted in a reactive monomer blend with processing additives that makes it very fluid
• Polymerisation: a polymerisation initiator is mixed with the resin to create an high molecular weight thermoplacstic matrix. Several type of reaction and intitiators are possible
• Process: as a thermoset resin used in composites fiber reinforced polymer. Elium® is compatible with traditional process and the parameters can be adjusted depending on the requirements (viscosity, time and temperature reactivity)
• Applications: our solution enables to obtain high performance composites products like epoxy, polyester or vinylester with all the benefits of thermoplastic matrix. Industries: wind energy, construction and civil engineering, transportation, marine, sports and consumers goods
• End of life: Elium® can be recycled with 2 methodologies, mechanical or chemical, to produce new recycled composites parts.

A composite part made with our Elium® resins:

• Is light and tough with superior properties under impact
• Is Styrene free, contains no BPA and cobalt salts
• Is fully recyclable with possible separation of the fibers and reuse of the virgin resin
• Has a cost efficient and lower Capex compared to similar thermosets parts
• Has additional features and benefits for adhesion, welding, thermoforming.

So great virtues of a recyclable resin system but what about real world boat building experience with the product. A company inEastern Canada did the first of many fishing vessels using the Arkema Elium products to build a 44’11” (13.7m) long with a 16’4″ (5m) beam and 42″ (1.1m) draft fishing hull a DJ Marine 45. The builder wanted to try infusing a full hull with the new resin matrix. The builder found the recyclable infusion resin was new for them. “The Elium resin is peculiar…it’s really sensitive to air leaks, and it’s more difficult to infuse compared to polyester resin.”

The first infusion happened October, 2023. DJ Marine’s preparation task was to gelcoat and skin coat the boat in the mold using standard vinylester resin. Then the crew of trainers, consultants, and trainees showed up for a two-week window with the first week was just to lay up the fiberglass. The second week they installed all the consumables, peel ply, etc., and then on the Friday the hull was infused. The laminate stack was multiple layers of conventional E-glass cloth, all cut to size. In addition, some sheets of balsa core were placed in bottom panels to strengthen the running surface.

The real problem was the vacuum bag material they’d ordered for the infusion was too thin and had pinholes in it, which led to multiple leaks as they attempted to do a standard vacuum drop test before running the resin. “The more you tried to find the leaks, the more leaks you had where you stepped on the plastic, it was nerve-wracking.”

They found at least two leaks forward in the mold. And thanks to backup vacuum lines they were able to prick the bag close to one leak and install the vacuum line right behind it so the air still coming in the pinhole travelled a very short distance instead of compromising a large area of hull.

“When you have one line that goes bad, you have to react, and then everybody panics,” said the builder. “Franck was very calm, stopped the pump, reset, and started again.” The lesson: You have minutes to react, and that is enough.

Some of that forgiving time they had to take corrective measures was a function of the resin choice. “With this infusion we chose our three-hour-open-time Elium. We wanted extra open time just in case, you don’t want to screw up a part that costs $50,000.” In the end, there was “just one dry spot from a leak, and we did a patch and repaired it” by flowing resin into the void area.

While the Elium resin made for a more ticklish infusion process than might have been the case with vinylester, the infusion was a success. For a crew that can infuse this fussy resin, conventional materials will be comparatively easy to handle. The jpegs give an idea.

 

Life cycle analysis (LCA) is about the total environmental cost of EG building and running a boat. All private pleasure boats have an environmental cost but the differences between boat build types on the environment can be very different. EG An aluminium 21 foot power boat will be 5 times greater impact on the environment than a plywood boat with a glass covering.

How are people doing this analysis. There are software products available, Brandon Davis of Turning Point Design used MarineShift360 (MS360), a LCA tool specifically developed for the marine industry. “For instance, CFD [computational fluid dynamics] calculations showed that it is necessary to reduce overall weight to lessen drag and achieve the speed a client expects. That suggested switching from recycled PET foam to virgin Divinycell, but when I plugged in the numbers, it became obvious that the difference in carbon footprint actually is negligible.” These tools can help avoid changes that cancel each other out or even increase the carbon footprint. Flax, for instance, is a natural fiber that absorbs CO2 during growth and has a much smaller energy footprint than carbon fiber or fiberglass. But as a laminate material it has heavier weights than the others, because it tends to soak up more resin during infusion leading to a heavier boat that uses more power/fuel. Translation, a flax laminate, due to weight or emissions doesn’t work out due to higher epoxy resin consumption, what’s the point of using flax.

During Brandon Davis analysis he estimated the carbon footprint of a 21′ power boat (Helios 21) and a displacement of 4,100 lbs. He basically found:

Plywood kit construction (baseline boat): Built from a CNC-cut plywood kit from 3⁄8″ (10mm) okoume plywood, hull sheathed with 6-oz glass and epoxy on both sides and bulkheads coated in epoxy. Paint is two-part LPU over a couple of applications of epoxy fillers and primers. The interior fit-out was kept as simple as possible. Power a four-stroke 40-hp (30-kW) Yamaha outboard, 18–20 knots cruising speed with a consumption of 8 nm per gallon.

PET foam core and fiberglass: Most of the details are identical to the plywood, but some differences of note are that the PET core is 100% recycled and about half the cost of plywood. However, hand laid laminates need to be thicker, so the boat consumes 2.5 times more epoxy and fiberglass with more fairing needed. This build boat could be 400 lbs (181 kg) lighter than the plywood version, which would translate into higher top speed, quicker to get on plane and/or better fuel economy.

Limited or full production run fiberglass using molds: Foam-cored boats are infused from full production tooling, which is more durable and yields a higher quality finish. In this method, production molds are pulled from a plug, which increases upfront costs that must be amortized by a long production run of dozens or hundreds of boats. Davis assumed gelcoat would be used, and labor is reduced dramatically. Weight and performance would be similar to the plywood boat. The down side of this approach is the requirements for full partial or full production molds which come at an environmental cost. The upside is the environmental impact can be reduced if a long production run is done (meaning a small % of the mold environmental impact is allocated to each boat) and also there is likely to be less waste materials in the build process as the exact amount is known for each boat.

There was also an aluminium option considered but the weight and material selection had a heavy environmental impact.

Results. The material build of the plywood and foam cored boats (be it divinycell or pet foam) had a very similar environmental impact. A solid fiberglass had 3 times the environmental build impact, an aluminium build had 7 times the environmental impact.

When you added the fuel usage (250 hours/year for EG 2 years) into the total environmental impact The environmental impact is similar. The plywood and foam cored boats use have about one third of the environmental impact of a solid glass hull and about one sixth of the impact of aluminium hull.

The surprise was the electric powered PET-foam-core kit boat would travel at 8 to 10 knots but its environmental impact is only about 10% less than an outboard powered same build boat. Reason the environmental cost of the batteries and the assumption of grid recharging which is not likely to be green power. The upside of electric is the longer you own it the more environmentally friendly it becomes compared to ongoing impact fossil fuel.

Sorry about the limited jpeg as this was a design study. Also the above numbers are a summary of the results for simplicity, not 100% accurate.