Multihull Structure Thoughts

I would think very few!
It is so easy to add weight to a boat when it is being built, but very difficult to get rid of it - many people have the same problem

And I was rather worried by how overweight this Rhea was - even before the prospective new owner loaded her up with his cruising gear.

 

Richard Woods Rhea is 40 x 23.3 foot with an empty weight of 7,850 lbs and a displacement of 11,200 lbs. The 51 foot mast carries 915 square foot fractional rig. The hull length to beam is about 12 to 1 with a draft over the low aspect ratio keels of 3.5 foot. The result is the Rhea design is it is slightly wider, 17% lighter and carries 22% more sail area on a 6 foot higher mast than the Meander 40 foot. The final variation is in the hull shape. There is a deep V version but the preferred is a rounded hull version which requires an upgraded structure.

Today we will talk about the WRC strip plank version and the foam glass version. Both have the more rounded V hull shape. The strip plank cedar version has 12mm Western Red Cedar in 70mm wide strips cut down to 35mm in round bilge area. The outside glass is 800gsm Biaxial e-glass and the hull inside skin is 600 gsm Biaxial e-glass all in epoxy.

The foam glass version is 12 mm Airex foam with 600 gsm rovings and 300 gram CSM (600/300 Rovimat) on either side in polyester or vinylester resin. Addition 600 gram CSM is added as required.

In both options there are 9 mm secondary bulkheads and 12 mm ply crossbeam bulkheads filleted with bog and glass to the hulls. The decks can be 9 mm plywood with a 300 gsm cloth covering or a 12 mm WRC glass or a 12 mm Termanto or Divinycell type foam with inner hull glass skin covering on both sides. The cuddy can be ply or foam glass as required. The cross beams as in all versions are wooden box beams with a 12 mm plywood web 50 x 50 mm top bottom flange, 12 mm ply web with 75 x 50 mm top and bottom flange, 12 mm ply web with 50 x 50 mm top and bottom flanges then the final 12 mm ply web. The interior takes 6 mm and 9 mm plywood.

An interesting point is the resin required for the strip plank cedar hulls is 440 lbs of epoxy. The foam glass hulls require 2,900 lbs of polyester resin. You start to understand strip plank cedar hulls are not much heavier than older style foam glass hulls with CSM layers in them. Modern foam glass hulls using resin infusion and virtually no CSM can be a lot lighter than a well built strip plank cedar hull. In Rhea’s case I suspect you could use 1,000 lbs less polyester resin with modern fabrics and vacuum bagging or resin infusion. The slight downside is, although it will probably be a “stronger” layup the external glass skin thickness will be thinner which means less puncture resistance so a fin keel may be a better option.

And for Guzzis3. The real problem of strip plank is the preparation of everything especially if you have to machine the strips to size by yourself. The actual laying strips on a mould can be painful with one person but the time drops dramatically if you have EG 4 plus people working on the hull, glue preparation etc at once. I have seen the cedar strips of a hull laid up in one day if there were multiple people and everything was prepared. Guzzis3 flat foam glass panels are faster but in relation of the build the hulls are 25% of the total build.

Limited jpegs sorry. Tomorrow Ondina Richard Woods 45 foot deep V cat.

 

Richard Woods design Ondina as a fast cruiser. Ondina has been drawn with either soft chine deep V hulls or rounded V hulls. Ondina is 45 x 25.3 foot with a weight of 9,920 lbs and a displacement of 15,450 lbs. The 52 foot fixed aluminium mast carries a 926 square foot fractional rig, as shown, or a masthead cutter rig are feasible. The length to beam is 11.9 to 1. The draft is 2.4 foot with the centre board up and 6 foot with centre boards down. The performance of these style of cats is good if built to weight. The Rhea is the fastest by about 10%, Ondina would match it in a seaway but would be slower around a course in moderate weather and Meander would be 10% slower. These boats can average about 7 to 10 knots over 24 hours. Again, it would depend on which version you built. The straight panel deep V would have more wetted surface which would mean it slightly slower in light airs than the rounded V models. As performance cruisers your speed is going to be more dictated by comfort at sea and ease of handling than pure speed.

The accommodation layout shown was drawn for two couples who wanted to sail offshore together. The wings on Ondina are large enough to be used as seats, thus vastly increasing the size of the saloon area. Each hull has a private double berth cabin, after that one hull has a galley, dinette, and full private toilet. The other hull has a workshop (this is a real cruiser), navigation area an separate seating for privacy if required. Other layouts are feasible as long as major structural components are maintained in their original position.

The Ondina structure is a development of Meander. As a result, some structural items are lighter than Meander and Rhea which allows Ondina to have the lowest displacement for its length. Ondina has a 10 mm ply skin with 37 x 25 mm stringers. The keels are multiple layers of 25 mm timber to the depth you require to provide a rounded shape. The secondary bulkheads a 9 mm plywood with 12 mm plywood crossbeam bulkheads. The decks are 8 mm plywood on 50 x 25 mm deck stringers and 75 x 25 mm deck beams. The interior is 6 mm and 8 mm plywood with 8 mm plywood floors and bunks. The cross beams are wooden box beams with a 15 mm plywood web 50 x 50 mm top bottom flange, 15 mm ply web with 75 x 50 mm top and bottom flange, 15 mm ply web with 50 x 50 mm top and bottom flanges then the final 15 mm ply web. The main mast cross beam has 100 x 50 mm centre flanges instead of the 75 x 50 mm top and bottom flanges. All exterior surfaces are covered with 300 gsm glass cloth and epoxy. The entire build should be epoxy saturated as per West system. The plywood is glued and screwed to stringers etc. How many screws? Try 5,000 countersunk brass screws. Oh, my sore wrist.

This is about the largest cat I would try and build at home and I would make sure that my partner was fully involved. Also, additional help and an under cover building site is really required. In short, it’s possible to build one but consider the 40 footers first. The jpegs give the idea.

 

Thank you very much. I can not help but be fascinated by them. I did not know rhea was a development of meander. It makes a lot of things make sense.

Are you sure the boat with a red hull is an ondina ? It appears to have a bridgedeck cabin and chined hull.

 

Gussis3. Richard Woods 2009 blog shows the cat being built by a German couple. It has Ondina hulls and it appears with Woods approval they added a bridge deck cabin. The 3 jpegs (Ondina 4, 3 and 2) are listed as an Ondina build jpegs. Tomorrow the Coral Cove 40 by Waller.

 

The Coral Cove 40 is designed by Mike Waller and is intended to fit somewhere between the Polynesian catamaran concept and the more high tech catamarans. It can be an open bridge deck cat or have a central cuddy cabin on the bridge deck area. The Coral Cove 40 is 40 x 24 foot with a weight of 12,000 lbs and a displacement of 14,250 lbs (maximum overload displacement of 16,400 lbs) The 59 foot fixed aluminium mast carries from 720 square foot (fractional rig) to 915 square foot (mast head sloop) of sail. The hull length to beam is 10 to 1 on the 35.3 foot waterline. The draft is 3.5 foot over the low aspect ratio fin keels. The Coral Cove 40 has a multi-chine hull with mini keels and can have transom hung rudders for cruising simplicity. Auxiliary power is provided by twin outboard motors mounted below the hull pods.

The design has several accommodation options for versatility and owner customisation. The basic accommodation is intended for long term cruising, and has a double berth forward in each hull. Both hulls have a raised seating area in the mid section extending into the hull pods. To starboard the area is arranged as a dinette with a pilot berth inboard, whilst to port this area is a large and comfortable lounging area. Aft to starboard is the huge galley and a single berth (which may be eliminated in favour of an even larger galley and extra lazarette), whilst to port the aft area is given over to a large W.C. area with separate shower compartment. As options for long distance cruising, the port hull center area may be arranged as a separate owner's cabin, with a full size double berth extending into the pod area. Forward of this can be either a storage / workshop area or a separate single cabin. The cockpit area features a solid floor fitted between the pod inner sides and the two main beams.

The Coral Cove cats do not use exotic materials. To keep construction simple, they are designed for all plywood construction and timber / epoxy construction with a fiberglass sheathed plywood hull shell over a framework of plywood bulkheads and timber longitudinals. The Coral cats all feature separate hulls connected by crossbeams. Beams are solidly mounted. Cats can be built as separate hulls to 80% completion, then transported to the water for final assembly. I do not know but I can imagine 9 mm ply hull shells over 50 x 18 mm stingers on 9 mm and 12 mm ply bulkheads. The decks could be 9 mm ply with 12 mm to 15 mm ply in the underwing. The crossbeam structures are unknown beyond plywood and timber.

The jpegs give the idea. The performance calculator says this cat will match an Ondina in all-round performance. The hull shape of the Coral Cove 40 has fuller ends than the Meander, Ondina series so I will not be surprised if it was faster upwind in a seaway even with fuller hulls.

 

That is actually a really neat design. I'm typically not a fan of wood catamarans, but that's one I can get behind.

 

If you have a look at the old site where that page can still be seen:

Sailing Catamarans - Review of 2009 http://www.sailingcatamarans.com/index.php/year-reviews/133-2009-boats-mentioned-romany-wizard-mirage-flica-saturn-merlin-sango-strike-ondina-transit-bee

The text immediately above the photo talks about a flica.

Sailing Catamarans - Flica 34 - 10.4m family ocean cruiser http://www.sailingcatamarans.com/index.php/designs-2/5-catamarans-over-40ft/182-flica-34

Note the chine below the waterline here:

Sailing Catamarans - Sailing Catamarans http://www.sailingcatamarans.com/index.php/component/content/article/351

I accept it is confusing. I spent some time studying that page a few weeks back to try and work out the photos.

 

The following catamaran is being finalised in design so details are little fluid but the concept is available. The hybrid sail powered (with assistance from renewable energy solar panels and wind turbines) catamaran “Manta” is 185 x 85 foot with a displacement of 4,000,000 lbs (1800 tons). Yes, the numbers are real. The 2 masts are 205 foot high of the water. The sail area is unknown. The draft of the hull is 11.5 foot. over the rudder is 18 foot and over the dagger boards is 48 foot. The power requirements is around 500kW of onboard renewable energy is generated via two wind turbines located at the stern, 500 square meters of photovoltaic solar panels at the bow, two hydro-generators under the boat and a Waste-to-Electricity Conversion Unit (WECU) used to power the hotel load, or what the captain and crew consume.

What is the purpose of this vessel? It is being created by Seacleaners, a group aiming to operate for 300 days a year collecting up to 10,000 tons per year of waste plastics from the ocean. Seacleaners has found that majority of plastics (about 60%) come from major rivers mouths in various countries, many in Asia. Manta expands to 150 foot wide with additional capture nets to sweep up floating plastics and micro plastics which is then processed onboard to smaller components for either assistance in powering the vessel or to be taken to shore for appropriate disposal. The vessel has accommodation for staff doing research on waste materials and has a state-of-the-art scientific laboratory.

Manta will be built from low carbon steel and uses low environmental impact fitout materials.

Manta when collecting waste plastic travels at 2.5 knots to allow sea creatures like fish and turtles to “run away” from he nets capturing the plastics. The vessel at full speed can travel at 12 knots when moving from location to location. The aim is to have many of these vessels globally to start to capture the million tons of plastic waste in the ocean

The jpegs give the impressions of the initial cat. There have been about 3 versions of the design so far.

 

This is a very impressive project - and it seems to be well funded. Brilliant.

Some more info about Manta on their website here -
https://www.theseacleaners.org/the-manta-innovation/

I was trying to find out more details as to who designed her - I was wondering if Incat Crowther might be involved - but it seems to be mostly 'in house'.

Here is a link to the first of their videos on YouTube -

 

I cannot find a reference to Richard Woods Chat 18 cat but I think it’s been done before. Regard this as an update or new. The Chat 18 cat is an inshore camp cruising cat suitable for bay, river or limited coastal work in good weather. The Chat is 18.3 x 8.2 foot with a weight of 700 lbs and a displacement to 1,500 lbs. The 27.5 foot mast carries a 120 square foot mainsail and a 75 square foot jib. The rig can come off a beach cat or be custom made for EG a Gunter rig. The length to beam on the hulls is 10 to 1. The Chat 18 is fitted with low aspect ratio keels, of 1.75 draft, for simplicity of both building and sailing, however daggerboards are an option for very shallow water sailing. The rudders can be kickup transom hung. The outboard power is 2.5 to 20 HP. The Chat is 8.2 foot wide so is easy to trail with no assembly needed. It will be quicker than most small monohulls to get from trailer to water, typically 15 minutes.

I suggested the cat is a camp cruiser with an internal space in the main cabin of 4.7 x 7 foot with a 3.4 foot headroom. Enough space for a double bed or a single bed and a camping galley with some storage. Despite its small size and the essential watertight compartments, there is still lots of storage space in the hulls for anchor, warps, fenders, deck cushions, BBQ, fishing tackle and all the other "stuff" that makes a day out on the water more enjoyable. A couple could have a comfortable weekend away with a bucket as a toilet. A deck tent over the cockpit would provide some additional space and privacy.

The construction is plywood timber. The hull bottoms and underwing are 9 mm plywood. The hull sides, decks and cabin are 6 mm plywood. The bulkheads are 6 mm plywood with some timber backing depending on the bulkhead. The 5 cross beams are 100 x 50 mm, the full width of the cat. The external surfaces are covered with 200 gsm cloth in epoxy. This cat only takes 1000 stainless steel screws. Most joints are filleted and fiberglass taped together. The hull shape minimises the number of timber stringers required as the angled tape seams do most of the strengthening. The basic materials list is below:

Plywood: 6mm ply 20 sheets 9mm ply 4 sheets
Timber : 2in x 1in 40m 3in x 1in 2m 2in x 2in 5m 1.5in x 1in 40m keels 1850 x 300 mm four of.
Beams: 4in x 2in x 2.5m 5 off Rudders 3m x 8in x 1in 2 1.5in x 2m glass tape 150m 100mm (4in) wide
Sheathing (optional) 60sqm 200g/sqm (4oz) epoxy 20kgs screws 1000 18mm (3/4in) x no6 200 25mm (1in) x no6 st steel cs

The performance of a Chat 18 is quite good for an 18 foot cruiser. One report says 7 knots in 12 knots of wind another said 10 to 11 knots in 20 knots of winds. This cat can move well but as a cruiser should not be pushed to hard. A good easily handled rig with a rotating mast will improve performance, next improvement will be good quality sails and building to plan with lighter weight plywood will help, but do not expect Hobie 20 performance. The jpegs give the idea.

 

This is the kind of boat that would be really easy to use and therefore get used often. I’d be tempted to make it longer. Maybe 24’ so not as extreme as a G32. One daggerboard and kick up rudders on mine please. Awesome little toy.

 

Ron. Have a look at Kohler Maxi Maxipage https://ikarus342000.com/MAXIpage.htm 26.25 x 8.2 foot trailable and designed as a cheap to build, smaller version of the G32

 

An update on Kohler’s Maxi 26 design that was featured as a prospective design on page 82 of this thread. The Maxi is 26.25 x 8 to 8.2 foot wide depending on where you live for trailing. The boat weight is 1,700 lbs with a displacement of 3,300 lbs with an optional water ballast of 570 lbs in each hull available for extra stability in stronger winds. The 26 foot mast is a 180 mm carbon fibre tube that has no spreaders to allow the 160 square foot mainsail to roll around the mast. The 161 square foot mainsail has semi vertical battens to hold up the fat head. The head sails range from 120 square foot to 170 square foot. This rig is one option there are others depending on need. The length to beam of the hulls are 16 to 1. The hulls are easy to build Sharpie (flat bottom with a slight lift of chines at bow) hulls. The draft is 0.9 foot to 3.7 foot over the kickup centreboards and rudders. Outboard can be 5 to 10 HP.

The cat is intended to be a higher performance bay sailor or sailed in sight of land near coasts, not offshore. Bernd designed a fold out seat to let a person sit out further and add to the stability. The water ballast when used appropriately will add to the stability and performance. Bernd did some calculations about stability and performance. There was a light displacement mode where the cat would average 9.1 knots lifting a hull in 17.44 knots of wind to a heavy displacement mode where the cat would average 8.94 knots and lift a hull in 19.18 knots of wind. This is quick for a trailable 26 foot cat.

The accommodation is similar to the ECO 5.5 catamaran. A double berth, a small galley and porta potti and limited headroom. This is a camp cruiser that can really sail more than a cruiser.

The build will be plywood and wood in epoxy and glassed over, as with Bernd’s other designs. The hull side skins are 6 mm ply, the hull bottoms are 9 mm plywood underwing is 12 mm plywood, bulkheads are 6 mm and 9 mm plywood with timber reinforcing. There are limited stringers. Bernd’s build time estimate is 500 hours.

The maxi will not match the performance of a G32 which inspired the design but the Maxi is fast for its size and it being a truly trailable catamaran. The jpegs give the idea. Please ignore the Maxi 32 label on some jpegs it should read Maxi 26. The web site is Maxipage https://ikarus342000.com/MAXIpage.htm

 

This is a 2 part item. The first will cover the concept and the second part will be about the structure. We are talking about a serious performance cruising catamaran designed by Greg Young of New Zealand. The JAMADHAR 100 is 96 foot total length including bow sprit. The actual cat is 88.5 x 44.3 foot with a displacement of 213,000 lbs. The 115 foot carbon fibre mast (weighs 3,900 lbs full rigged) carries a 2,920 square foot mainsail, a 882 square foot staysail, 1,505 square foot genoa and 3,605 square foot Code 0. The length to beam on the hulls is about 10 to 1 at the waterline. The draft is 7.2 foot over the low aspect ratio fin keels. The two 6 cylinder YANMAR turbocharged diesel engines of 315 hp drive through shaft drives.

The rig’s genoa forestay and inner forestay in NITRONIC 50 stainless steel and other rigging is KEVLAR. The halyard, sheets, and some rigging is DYNEEMA. The entire rig is controlled by hydraulic winches.

The accommodation is large and luxurious. The hulls have 5 double berth cabins with attached toilets and the master galley. The main deck has 2 king size double berth cabins with attached toilets forward. The main saloon has a dinette seating area, entertainment area and bar secondary galley. There is a large glass door connecting to the lower cockpit. The upper sailing cockpit is where all sail controls (mainly push buttons for hydraulics) and steering position is.

This is a foam glass, Kevlar and carbon fibre epoxy infused structure. It took 3 years of a professional yard to build. Result, a bank repossession and its available for a mere 2.35 million Euros.

There is no question that this cat can sail with initial trials confirming that in 5 knots wind it sails at 5 knots, in 10 knots of wind it sails at 8 knots, in 15 knots of wind it sails at 12 knots. Higher winds higher speeds up to about 20 knots.

The jpegs give the idea. Tomorrow we will give some construction details.