Multihull Structure Thoughts

The foils reminded me about a very interesting Polish trimaran "Retman II". Designed by Ludomir Jawniszko, built by youth from Lodz (a city far from the sea), was prepared for OSTAR'76 race. The foils added some dynamic lift to the low-buoyancy amas. Another interesting feature was the rig, consisting of two wingmasts and jibs. The masts were buoyant, which, together with low-displacement amas, gave the trimaran a self-righting ability. During the tests, the crew was able to right the capsized boat in ten minutes.

Retman II didn't enter the race due to the problems with bureaucracy - she was too innovative for the Polish authorities to get a certificate. Nevertheless, she crossed Atlantic a year later. After a damage in collision with a buoy, the hull was stored in Lodz (I saw it in 1999), and finally lost in fire. The only remainder is one of her wingmasts, that is standing in the sailing club in Lodz.

regards

krzys

 

This item is about “Ollie” a racing cruising trimaran that was designed and built in 1984 by the Gougeon brother’s. The design was the Stressform™ 35 along with Stressform wingmast plans. Ollie’s design further advanced Jan’s ideas for self-righting multihulls. Ollie is 36 x 30 foot and weighs 2600 lbs. The 45 foot Stressform wooden wing mast carries a total of 670 square foot of sail in the initial design. 30 plus years later Ollie now has black (carbon fibre type) fat square headed mainsail and jibs with I suspect increased sail area. There is a daggerboard in the main hull and an outboard kickup rudder.

Now we get to the floats. Ollie was the second trimaran after the 25 x 28 foot Splinter (page 37 of this thread) designed to be capable of being righted by the onboard crew after a capsize. Jan Gougeon was trapped on a capsized tri for 4 days in the Atlantic and each design he did afterwards had self righting capability. Ollies floats were long and low buoyancy (a bit over 100% of displacement) to allow the self righting. Ollie, when capsized, self righting system allows sea water to be introduced into an ama until it submerges. The partial buoyancy in the light partially sealed wingmast provides helps lift the tri onto its side. Then, Ollie would be sitting on her side and water pumped out of the submerged ama and into the other float. Judging by the shrouds there might be some mast adjustments going here as well. Please understand Ollie will not immediately self right, the crew have to do a lot of work, but it can be recovered by the crew. If you find the G-32 patent by the Jan Gougeon it details the use of the rig in a righting situation.

The performance of Ollie is very good. It has been winning races for 38 years. Its most recent big win was the Port Huron to Mackinaw race last year. There are several Great Lakes races were Ollie held the race record for years. It is fast seriously fast on all points of sail. The accommodation is “good” according to Russell Brown but I have not found any interior jpegs. The mainhull shape indicates room for berths, galley, seating and loo. But at a weight of 2600 lbs I suspect basic but effective would describe the accommodation.

The structure of Ollie is wood epoxy and some glass cloth. The main hull below the chine is 7 mm 5 ply plywood tortured into shape with supporting ribs. The shell is covered by 4 oz glass cloth. Above the chine line (we are educated guessing here based on Splinter) everything from the wing, deck, cabin etc are thin ply sandwiches with Verticel cores. The cross beams are laminated timber. 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.

This was and still is a ground breaking trimaran. It is a pity that the ideas and design did not get a greater acceptance. The performance capability of this tri would amaze many people and some may be willing to sacrifice the 4 double berths, air-conditioning etc to really enjoy sailing. The jpegs give an idea, the last 2 jpegs are of Splinter.

 

Sometimes I see a jpeg look and think interesting but why. Then came this cat. Stormvogel is a unique catamaran designed by Alexander Verheus. The cat is 49.8 x 30.6 foot with a weight of 21,800 lbs. The mast is 60 foot high and is a very large diameter tube with no spreaders. The mainsail has has a leading eadge sleeve that fits over the mast to provide a smooth leading edge to the mainsail sail. The headsails are on roller furling drums. The total sail area of the mainsail and jib is 1,000 square foot. There is also a 1,100 square foot gennaker. The draft varies from 2 foot to 6.5 foot by centre boards. There is one central Diesel 50hp engine, located just ahead of the mast. It runs through a prop shaft that raises out of the water when not in use.

Now back to the question of why. Alexander Verheus was asked to design a cat that “incorporate a look that has influences from Scandinavia and Polynesia” and have it built in the Netherlands to an extremely high standard. The design specification was to build a light, fast, safe, world traveller that uses the latest materials. Alexander took on the challenge and produced Stormvogel. Stormvogel mission is a charter yacht for day charters or longer stays. The cat was initially located in Holland then sailed to the West Indies and chartered there.

The accommodation has 5 mainly hull based double cabins with a toilet in each hull. The galley and dinette seating is down aft in the port hull. The function of the bridgedeck cabin is mainly for helming, navigation and shelter from the sun. The cockpit has some additional seating. This is a Wharram style accommodation with a bridgedeck and a small cabin. I am a little confused but onward.

The build is interesting. Notice the clinker hull shape (nod to Scandinavian influences) on the Wharram type double ended hull shape. The “clinker” planks are 30 mm foam core between fiberglass resin skins. A report says they are e-glass polyester another says the cat “is built out of 3cm foam and epoxy, vacuum bagged with carbon and kevlar reinforcement at critical points.” Either way this technique has 2 advantages. The 30 mm foam with provide a stiff panel with minimal framing and the clinker hull shape will provide “stiffening” default stringers down the length of the hull. Again either 30 mm foam or the clinker hull approach would provide enough stiffening but doing both is an overkill. The hull bottoms are round bilge. Again, Alexander is meeting a customer demand. I suspect the Kevlar and Carbon fibre is used as strengthening and the e-glass used in the shell etc. I also suspect the mast is a carbon fibre tube.

The performance according to the following quate is good. “Sailing is just a pleasure on the Stormvogel. Stable at the helm, stable on the water, light to manoeuvre and easy accelerating. Within light air the Stormvogel performs moderate and you might wish a bit higher mast especially with to the wind courses. But with wind from the side or backwards you can use the gennaker of 110 m2 and the catamaran accelerates quickly to 5-8 knots. With a light breeze the Stormvogel sails easy 5 knots to the wind and in other courses up to 9-10 knots. From a wind strength of force 5-6 bf. the speed goes up to 8-16 knots. Do you have in addition the right course and waves, you can start surfing with a speed up to 20 knots.”

An interesting design. The jpegs give the idea.

 

Interesting design Oldmulti, certainly a step away from the norm.
I am particularly interested in the deck mounted motor with the prop shaft able to be raised & lowered.
Do you know of any details on this or any other with a similar method/design ?
Thank you.

 

Peterbike. The engine longtail method is used a lot in Wharram cats. There are variations of the idea but if you read through some of the following online magazines from the Polynesian Catamaran Association the Sailorman and Sea People magazines were a very good source of interesting ideas that Wharram builders came up with. They are available at Polynesian Catamaran Association http://pca.colegarner.com/sailorman.html

The source of a good start article for the longtail engine is page 16 of Sailorman number 9 at: http://pca.colegarner.com/Sailorman-009.pdf

Page 28 of http://pca.colegarner.com/Sailorman-014.pdf

There are more articles in later mags, it just will take time to find them. Have fun.

 

I noticed that Punch catamarans designed by Alain Mortain was to restart production after a 10 year gap. Punch cats were produced by Multicap Caraïbes based in Martinique. Now they will be produced in the south of Portugal. But that is not the only change. Punch catamarans were produced in several versions and sizes. They all had one consistency they were built in sheet plywood and timber that was epoxy saturated with glass epoxy covering. The bridgedeck cabins had some foam glass for insulation purposes. An example of the designs was the Punch 12.50 catamaran. The 12.50 was 41.7 x 21 foot with a weight of 15,600 lbs. The 49 foot aluminium mast carries a fractional sloop rig with a 570 square foot mainsail, a roller furling genoa of 355 square foot and a spinnaker of 1184 square foot. The draft is 4 foot over the fixed low aspect ratio keels. The engines start at 2 x 20 HP inboard diesels. The dimensions of each 12.50 varied a little because they were basically a series production but customisable cat.

The 12.50 accommodation has 4 double berth cabins in the hulls with a toilet in each hull. The main saloon has a large galley and a large dinette. In short the pretty standard layout for a cruising catamaran. The performance of the cats was good due to there light weight, slim hulls and reasonable rig. The only downside are modern buyers who think 4.2 foot wide double bunks are cramped and we cannot put our feet down beside the beds. Slim hulls help speed and seakeeping.

The build of these light and fast catamarans, plywood (Sapeli)/epoxy saturated and timber framing and stringers. They were fiber-glassed reinforced all over externally with some glass reinforcing inside. The hull shapes were flat bottom dory shapes with the chines below the waterline so when sailing it was very hard to tell from the finish if they were ply or glass. These cats were well built as Multicap started in the early 1987 and many 20 plus year old Punches are still be resold for very good money. Well designed, built and maintained ply saturated in epoxy cats can last for decades. The jpegs below are of several Punch 12.50’s, notice the frame and stringer arrangements especial of the underside of the decks. This is a fair amount of work but for some people it would be easier than a foam glass cat.

Now we got to the new Punch cats being built in Portugal. The headlines include “Punch, the plywood cruising catamaran range is back on track” (Boatnews) and “Punch 17.10 - Wood/epoxy catamarans making a big comeback” (Multihulls-News). Again, they are claimed to be strip planked and wood, until you read the details. The new 12.70 (and the rest of the range including the 17.10) will have strip planks from PET foam and glass in resin on either side. The topsides are flat foam glass panels. The hulls are round bilge etc The weight is going to be 11,700 lbs for the 12.70.etc. In short, a new design in effect. There is nothing wrong with the new Punch but it is a very different structure to the old Punch models. I suspect it is difficult to sell plywood cats in a fiberglass obsessed world.

The jpegs give an idea.

 

Wharram catamarans are reasonable sailing catamarans that in the latest versions perform well. Some of the earlier versions had some issues and after a period, had improvements in hull shapes and rigs to improve performance, handling and seakeeping capability. But there is one “downside”, its about the size of the cat and the available accommodation. For a given length Wharram cats have generally smaller internal accommodation than a lot of other cats.

This ends up being a real problem because many Wharrams are being modified to increase their Wharrams accommodation and “improve” the performance of Wharram cat by modifying the rig, ensuring the cat is rigid etc. Some of these modifications are well done but many confuse me, as the modifications are badly done impacting the Wharram’s sailing capability and seakeeping qualities.

Attached are some jpegs. The first set are of the accommodation at all costs versions (jpegs 1 and 2) that should remain at a dock permentaly, followed by the “we will make it rigid cat” with more accommodation and a “conventional rig” (3 to 5). Next are the improved accommodation whilst still having some sailing capability (5 to 8) and then the modified rig on basically a set of Wharram hulls (9 and 10).

Then I came across the jpegs 11 to 13. This is a Pahi 42 cat modified to suit the owners’ requirements. It’s a GRP version with a full bridgedeck cabin that has an aerorig placed on it. Next it has stern extensions to increase the waterline length and broaden the stern to dampen the pitching. Why? Someone has spent a lot of money turning an economical simple cat into a accommodation platform with a very expensive rig and then found it had some pitching issues which required a big hull modification to correct some of the issues.

Endlessly modifying a design to build your dream is the equivalent of buying a 1990 minivan and putting a V8 engine in it to make it go like a Ferrari. It is expensive and just does not work well.

If the owner had a completely new design, he could have had a much more integrated catamaran that would have meet their accommodation and sailing demands at a similar or lesser cost. The new design, I suspect, would have sailed faster with less pitching. I know at least 1 full bridgedeck production catamaran who will talk to you about an aerorig, expensive but possible.

Summary. Wharram design cats for specific purposes, they are designed to be economical, easy to build and if built to plan sail OK. The thing you have to accept is there limited accommodation. Modifying them is often expensive reducing their sailing and handling capabilities. Talk to the designer first. I have seen to many disappointed people trying to sell their “dream” that has turned into a nightmare.

 

I've seen a few horrible modified Wharrams over the years.
Currently in our area is a 40' Narai that has had a full bridgedeck cabin added.
The boat is well down on the designed waterline aft, with very little bridgedeck clearance.
Probably comfortable inside, but would sail like a brick to windward, and I wouldn't want to be on her in a storm.

Nootka Dancer, the Pahi 42 with Balestron and stern mods, was lost some years ago. Mast beam broke, and the boat came apart.

 

On page 77 of this thread is an item on Saphira a Chris White designed biplane cruising catamaran for an older couple. The biplane rig was selected for ease of shorthanded sailing it should be very fast directly upwind and downwind which are typically the weaker points in catamaran sailing performance. A cruising catamaran that has a youtube video of Saphira doing 16 knots while people are wandering around thinking this is normal. OK. This is an update.

Saphira is a 70 x 32 foot cat, designed by Chris White, that is aimed at 300 mile days with a 2 person crew. It weighs 33,000 lbs at its day sailing weight and can go to 42,000 lbs in full cruise mode. The biplane carbon fibre 100 foot wing mast rig is (guess) two 1300 square foot wing mast sail combinations for a total of 2600 square foot. The hull length to beam is about 13.5 to 1 and the hulls have daggerboards with small keels to protect rudders. The masts are full carbon fibre wings designed Southern Spars New Zealand who applied their considerable engineering experience to the rig. The mast rotation is controlled by electric motors and a press button. Saphira has 4 foot of underwing clearance which has proven to almost completely eliminate getting kicked from below. When that does happen the bridge deck (deckhouse floor) is an extremely stiff carbon skinned laminate with large carbon fiber box beams on the underside.

The design process involved many people, each of whom contributed their specific areas of expertise. SDK did the bulk of the structural engineering. Robbie Doyle had a lot of input on the sail plan. The design of the masts was central to the project, and Southern Spars New Zealand applied their considerable engineering experience to the rig. An outsourced company, Outradius, calculated the loads required for each piece of sailing hardware for the yacht based on the maximum possible loads on the running rigging. Using these loads and a baseline factor of safety, the team specified all production pieces of hardware to be installed on the boat. In some areas such as lines exiting the mast and entering the daggerboard trunks, the team at Outradius designed custom aluminum and stainless steel sheave boxes and ferrules, optimizing their designs using finite element analysis. From prior catamaran sailing experience and input from the owner, the hardware design globally defined the ergonomics of how the yacht is to be sailed.

The A70F is long, lean and light, built in all pre-preg carbon fiber. The boatbuilder Eric Goetz, an old friend of Peter's, built the boat in all pre-preg carbon fibre foam composite. Extensive 3D computer modelling was used to CNC cut and mill moulds and parts. Large ovens were built to vacuum bag and cure the hulls and other large parts at the required 200 degrees F. The 100% Carbon Fiber/Epoxy Resin construction utilizes extra thick foam cores for strength and insulation. Robust uni-directional carbon fiber reinforcing laminates in all critical high load areas increase strength and stiffness for superior longevity. Hull, decks and bulkheads are all vacuum bagged epoxy/carbon over thermo formed foam core. There are no cracks or gaps in the core which eliminates the possibility of water migrating withing the laminate. Hull, deck and crossbeam laminates are all on the robust side to insure long life. The result is a super stiff structure at very low weight.

The builders prefer to build as much as they can upside down since dust and debris falls out of the boat and you can work standing on a flat floor. But eventually the hulls need to be rotated and this required cranes to do the job. Currently the deck is attached, most of the interior in place and systems/machinery are being installed. Across the street from Eric Goetz boat building an Atlantic 72 was built at Aquidneck Custom Composites with a conventional sloop rig but the same basic dimensions as the A70 and also in carbon fibre foam sandwich.

From the owner “I have experience with the rig. We are an older cruising couple and, in many conditions, we find that using just one sail works great. Of course, it affects the balance somewhat, but not in any ways that I consider negative. Our sails are large -- they are the only two sails on the boat and have the same total sail area as a cat (with our righting moment) would have if its full main and largest spinnaker were set. A picture of our boat is attached. Please PM me if you would like more information.” Biplane rig behaviors - Cruisers & Sailing Forums https://www.cruisersforum.com/forums/f48/biplane-rig-behaviors-267015.html From other reports Saphira is capable of 20 knots plus and 300 miles days but in reality the owners do 7 to 12 knot averages.

Many of the jpegs are new and give some idea of Saphira.

 

NZ has a cyclone passing over it now. Does anyone know about this? "A New Zealand navy helicopter attends a yacht in distress in the Hauraki Gulf off the North Island"

 

Some info here:

Catamaran "888"possibly lost at sea https://forums.sailinganarchy.com/threads/catamaran-888-possibly-lost-at-sea.240902/

 

Thank you SolGato. It looks like 888. I hope a great boat is not lost.

 

On page 21, 66, 88, 92, 147 and 177 of this thread I have done updates on Minimus 11, a very original small ocean voyaging catamaran. Why the ongoing interest (boarding on obsession)? This man has done many ocean miles in a 23’ Wharram cat from Mexico to Hawaii, a 20’ monohull from Seattle to southern Mexico and most recently, a 25’ monohull (Minimus) from California to Tahiti. The owner is an original thinker who is willing to design and build his ideas and then sail them many ocean miles. Have no illusions when he says he has built an offshore cruiser in Minimus 11, he is serious about crossing oceans.

Minimus 11 is 23.75 x 13.33 foot, weighs 1600 lbs and can carry 1200 lbs of people, food and equipment. The 4 mast rig carries 2 junk sails of 91 square foot and 2 smaller mizzen junk sails. The 18 foot masts are from 4" (102mm) pipe with a wall thickness of 0.072" (1.85mm). When finished, they had two 18' (5.5m) masts that were triple wall (0.216", 5.5mm) in the bottom third of the mast, double wall (0.144", 3.7mm) in the middle third, and single wall (0.072", 1.8mm) in the top third. The underwing clearance is 2.5 foot. The length to beam of the dory flat bottom hulls is 10 to 1. There was a concern the flat bottoms hulls might pound going to windward in choppy seas. She got well tested and hasn’t proved to be an issue. A daggerboard was added in the bridge deck to aid in tacking and added significantly to windward performance. Ropes hold the board in position when down.

The build is 12 mm MDO plywood (used for outdoor signs) with 25 x 50 mm chine stringers and sheer stringers. 50 x 50 mm lumber is used for bulkhead reinforcement and deck beams. Raka epoxy with medium hardener and epoxy additives, including wood flour, chopped fiberglass, microballoons and silica. MDO doesn't require an additional layer of fiberglass to prevent surface checking. Instead, hulls, deck and cabin tops will simply be covered with 3 coats of epoxy and painted. Only the portion of each hull below the waterline will be fiberglassed for extra abrasion resistance should we want to beach the boat. The decks are 12 mm MDO. The wet deck is 150 x 25 mm cedar and some MDO. The cross beams are made from 3/4" x 8" MDO plywood capped top and bottom with pairs of 1-1/2" x 1-3/4" Douglas fir caps. They beams are strong. The beams were originally attached to the hulls with Wharram type rope lashings.

The accommodation has about 4 foot head room in each of the 4 cabins. One hull has a galley, with a person in one cabin and another person in the other. They can see each other, converse and pass food through the open center bulkhead. They sleep in the other hull. The bunks are about 24" (61cm) wide and have found them comfortable.

Now we to the point of this update. Minimus 11 has now been sailed enough to show up some weaknesses that need to be corrected and a human factor is coming into play.

--Lashings: The lashings between the hulls and the fore and aft beams loosened up a bit in the course of the trip. Partly, it may have been due to the pressure of the lashings denting the wood on top of the beams. He gave thought to replacing the lashings with another fastening method such as ratchet straps or metal fasteners; he laid an additional amount of fiberglass at the lashing points on the dented cross beams. This did not work. He changed from rope lashings to stainless steel ratchet straps and modified the attachment blocks on the hull sides.

--After installation of a central centreboard to improve windward performance, the centerboard support lines started slipping: On each side of the centerboard are two dyneema supporting lines that keep the centerboard vertical. These lines were knotted at each end and, as happens with dyneema under load, the knots slipped, allowing the board to angle to the side. Our plan is to instead use eye splices in place of knots and to pre-stretch the lines.

--Assembly and disassembly: Full assembly, including stowage of gear and provisions for extended sailing, requires a couple days. That includes removing the beams and deck boards from the trailer, raising the hulls up, positioning the temporary mounting beams on the trailer, lowering the hulls onto them, spreading the hulls and aligning them, setting the main beams in place and lashing them, putting on the deck beams, rudders and boomkins, stepping the masts, hooking up the electrical harness, rigging the sails and finally loading gear and provisions. She's best suited for extended sailing in which assembly and disassembly are only occasional tasks. We're always pretty tired by the end of assembly and will be working on ways to streamline the process. Disassembly is quicker, but still takes half a day or more.

--Exposure: Her small cabins and lack of covered bridge deck mean that her crew are mostly on deck and exposed to the weather. Going into the trip he knew that she would be a warm weather boat, at least for extended sailing. It was the cold weather we didn't expect. Although the cabins are fine for sleeping and sitting, being confined to them for extended periods led us to refer to them as "coffin cabins". Pearl, being 5'4" tall, found them comfortable, but for me at 6' 2", it was tighter. We slept feet to feet in one hull and there were many times that I banged my head where the end of the cabin meets the deck at the head of each cabin. We'll be foam padding those parts of the cabins before going out again.

Translation. Minimus 11 is now an ocean capable minimum cruiser that will self steer using the rig and rudder settings alone. But the owners are now aged 67 (David) and 65 (Pearl), health issues loom larger and the comfort of the boat is becoming more important which resulted in the exposure comment. If you are younger, without much money, you could build this type of cat for less money than a square top mainsail on a 30 foot Farrier and see a lot of the world. But if you are older, I suspect you would need a bigger version (may be 27- 28 foot) with real sitting headroom (4.5 foot minimum) with an organised galley and loo area. The structure could be the same and the rig would be slightly larger but very similar in concept.

This cat really works and this week has just started cruising south in Mexico waters again. The jpegs give the idea.

 

The following catamaran is one mans dream that he designed and built around 1980. It was designed by Frits Dubois for his own use and built in his multihull-yard at Groningen. The cat was conceived as a very high performance cruiser. It achieved it. The “Duo” is 40.6 x 19.6 foot (extended sterns it is now 43 foot overall) with a weight of 3360 lbs and a displacement of 3600 lbs (a number I doubt, I suspect it is more like 4 to 5000 lbs). The 46 foot aluminium mast carries a mainsail of 826 square foot, genoa of 645 square foot and a 1,720 square foot spinnaker. The length to beam of the hulls is about 12 to 1 at the waterline. The draft ranges from 1 foot to 6 foot over the daggerboards. The engine is a Yamaha 9.9.

The accommodation is mainly hull based with a double berth in each hull. One hull has a galley the other hull has a toilet and some seating with a table. There is a small sitting cabin on the bridge deck with an attached cockpit where helming is done from, Headroom in the hulls is 6 foot. The bridge deck cabin headroom is 5 foot. This cat was designed with performance in mind with some accommodation, not an outright cruiser.

The entire build is plywood and wood saturated in epoxy and externally glassed in epoxy. The crossbeams are box structures of wood with plywood. The hulls are round bilge with frames and stringers. Again, if a plywood, wood structure is well designed, built and maintained they can last over 40 years. Duo is currently in the West Indies and looks very good.

So what does a high performance cruiser mean. 8 to 12 knot averages with peaks of 20 knots. Duo has done local racing in Holland and West Indies after crossing the Atlantic. In short it has achieved it intended design purpose of being a racer and a fast voyager.

The jpegs give the idea.

 

Re Duo, she reminds me quite a lot (re her construction and interior photos) of the cats built by Peter Spronk in St Maarten in the 70's and 80's.
Although Duo is much more racy and lighter than a typical Spronk cat of similar size.
@oldmulti have you ever seen any Spronk cats that have voyaged to downunder?