RAKU 40 PERFORMANCE CRUISING CATAMARAN

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Raku 40

We're talking cruising here; the ability to cross oceans, escape the race and chill out in some of the planet's more remote hideaways. Let's start with the basics; some comfortable beds, a bathroom or two and some reasonable cooking facilities. We want to be able to lounge around in a reasonably sheltered space to share drinks, food, and stories true or highly fanciful.

 

Well there's a lot of cats out that that can do all of those things. But Raku 40 doesn't stop where most of them leave off.

 

We want to be inspired in our work and the simple way to do that is to do some work that will inspire you. Let's create some serious sporting equipment. Let's give it some style so you'll  be inspired to get it out onto the water. A streamlined profile that won't create a vortex like a freight train, and hull lines and foils that will keep you sailing when the breeze has become a headwind, or faded to the point where less well equipped vessels are reaching for the engine starter.


Accommodation Layouts


1. Classic Layout

We've been using variations on this layout on many of designs over a long period of time and it's still a favorite with a lot of owners, especially those who prefer a sense of security in the saloon when the weather turns adverse.

We've retained a reasonably wide opening in the saloon door (1.5m) and this can be further reduced to provide more bench space in the saloon if preferred.

Port Hull

The standard layout provides for an owner's cabin in the port hull and two berths in the stbd hull. The aft berth is 1.4m wide at the height of the berth panel, but the inboard hull side flares out quickly above the panel so at sleeping height it is 1.5m or more wide depending on the height of the mattress. All of the berths are 2m long.

The central bathroom in the stbd hull can be replicated in the port hull.

Stbd Hull

The central bathroom in the stbd hull is part of the standard arrangement but there is also the option of fitting out the stbd hull the same as the port hull or the same as the stbd hull in the open version. The forward berth os 1060mm wide in the position as shown, increasing to 1150 wide if it is moved aft to 500mm forward of the mast BH


2. Open Layout

The open layout features a 2.4m wide opening in the bulkhead between the saloon and the cockpit, effectively creating a spacious, airy living space that is ideal for the tropic and temperate climates.

In adverse conditions the saloon can be sealed off from the weather with drop down vinyl clears or with solid infill panels that clip into place and store in the cockit lockers while not in use.

The saloon features a large lounge pad forward to port that can be used as a double bed for occasional guests or simply serves as a great lounging area.

Forward to starboard is a couch that is also wide enough to serve as a single berth.

The fwd facing nav. station is further to stbd.

Down below you can use the layout we've suggested here or change it to suit your own preferences.

Starboard Hull.

Given the amount of sleeping space in the saloon the forward berth is not essential and that space could be well deployed for storage. If it is used for sleeping the access can be through the stbd bathroom, or you can seal that bulkhead off and use it as a crew cabin with access through the deck hatch.

Port Hull

The owner's cabin allows for a generous bathroom forward with the toilet and washbasin separated from the shower compartment with a bulkhead that can be fitted with a door to prevent shower water splashing into the rest of the bathroom. The area between the bathroom and the sleeping cabin is open for creative deployment of office space or storage of personal items.

The standard plan allows for a sill at the saloon opening to comply with the ISO stands and prevent water washing into the saloon in case of a boarding wave. The sill can be removed to provide a continuous floor between the cockpit and the saloon but in this case there should be provision to close off the passage from the saloon to the hull accommodation, and a drain should be fitted across the bulkhead opening.


Two Rig Options - Cruising (17m Mast) and Racing (18.8m Mast)

If you're paying marina fees based on your LOA you probably don't want a premanent prodder extending forward of the hull length and contributing to the cost.

So the base configuration gets a self tacking jib and Code Zero/screecher set on a furler on the end of the longeron which terminates level with the bow.

Find you need more power later on?

Simply fit an extension, removeable or not, and talk to your sailmaker about a big gennaker outside the shroud and back to the cockpit.

The racing Raku 40 is begging for a tall carbon mast, rotating or not, but a rotating wing would look the part on this boat.

The one piece longeron extends wi=ell forward of the bow and carries a large gennaker that sheets outside the shroud back to the cockpit. For both rig configurations the longeron and forebeam are built as an intergral unit. The longer longeron will require under deck support to provide good luff tension upwind.


Rig Selection for Raku 40

What's the best rig type? Alloy or carbon? Wing section or conventional mast profile? Rotating or non rotating? They all work. They all have their own advantages and disadvantages. To help you sort through the issues we've written a fairly brief article titled "Rig Selection Guide for Multihulls".

You can see it here on the LAB.



Generous Shaded Cockpit laid out for Sailing and Socialising

Creating the Raku 40 wasn't just an exercise in creating a great performing cat and then figuring at how much accommodation we could cram into it. In fact the design has evolved over a number of years taking into account the efficiency of the rig, the hull forms, the helming arrangement, the layout of the sail controls and in particular the layout of the cockpit.

The cockpit provides not just a practical area for the crew sailing the boat, but a convivial socialising space which, with the open layout adds up to a total length of 5.2m and about 4m in width (depending where you take the measurement).

The roof over the cockpit provides 8.4 square metres of shade and covering all of the seating in the cockpit when the sun is overhead.

The cantilevered roof is supported by two beams extending inside the saloon to minimise clutter of support posts in the cockpit

On an earlier version of this design we offered the option of bulkhead mounted helm stations but we have left them off this version because of the other design features we have been able to incorporate. You could still incorporate the bulkhead mounted helms but this requires a different cockpit layout with the aft berths moved further aft.

 


Raku 40 Deck Plan

Two basic deck layouts cover all bases from fully crewed racing through to single handed or two handed voyaging. Either layout can be used with either sail plan and either accommodation layout, giving you broad scope in setting up the boat to suit.

The fully crewed option terminates all the halyards on the small deck at the mast base. Only the jib sheet, the furler lines and the daggerboard control lines go back to the cockpit.

The short handed version takes the halyards back to the cockpit winch across the cabin top and down to the helm station just inside the outboard cabin side.

Both layouts use six winches. For the crewed version two winches at the mast base, one at each helm and two on the aft beam for the mainsheet and traveller controls.

For the short handed version there are two winches each side in the cockpit and the two on the aft beam.


Raku 40 Overall Dimensions (plan)

Raku 40 Specifications and Sail Areas                  Hull and Displacement Data

LOA

BOA

BEAM CL-CL

 

SAIL AREAS

MAINSAIL

JIB

CODE ZERO

ASSYMETRIC A1

M+ FT 

MAST LENGTH

AIR DRAFT

MAST FROM BOW 

 

12m

7.2m

5.6m

 

SAIL AREAS

57.7 sq.m.

22.8 sq.m.

41 sq.m.

112 sq.m.

80.5 sq.m.

17 m Standard Rig. 18.8m Racing Rig

18.25 m Standard Rig

45% LOA

BEAM DWL

B:L RATIO DWL

WETTED AREA

SINKAGE RATE*

MAX DISP. 

MAX RIGHTING MOMENT

TYPICAL SAILING WEIGHT (light)

 

*This means that if you load the boat by an additional 191kg it will sink 10mm in the water.

 

1036 mm

1:11.58

(2 hulls) 31.5 sq.m

(2 hulls) 191 kg/cm*

7500kg

2100 kg/m

4000-4500kg

All details subject to change without notice


Raku 40 Displacement and Trim

Displacement Case 1. DWL   (max disp)     

Volume Displacement = 7066kg

Length to Beam Ratio Hull 11.8:1

Wing clearance: 820mm at lowest point

 

Displacement Case 2. DWL-50mm

Volume Displacement = 6140kg

 Length to Beam Ratio Hull =12:1

Wing clearance 870mm at lowest point

 

Displacement Case 3. DWL-100mm

Volume Displacement 5276kg

Length to Beam Ratio Hull 12.2:1

Wing clearance 920mm at lowest point

 

Displacement Case 4. DWL-150mm

Volume Displacement = 4446 kg

Length to beam Ratio Hull 12.54:1

Wing clearance at lowest point 970mm

 

The images you see on these pages are made with the boat sitting on its designed waterline (DWL) which is where it will sit at a weight of 7066kg and the transom just clear of the water. (45mm).

Typically a boat of this size and style will be launched ready to sail somewhere between 4000kg and 4500 kg fully fitted ready to sail including inboard 35HP diesels and an aluminium rig.

 

In cruising mode the boat will typically weigh somewhere between Case 2 and Case 3 (column at left) and if fully loaded for long term cruising the boat might be sitting close to the DWL at around seven tonnes. So the payload is somewhere between 2.5 and 3 tonnes.

 

As the figures show the WL beam is finer for the lighter boat. For this style of boat we avoid having the waterline any finer than about 1:13 because the higher sinkage rate limits payload and reduces wing clearance. It also increases wetted area which is a hindrance to performance in lighter conditions.


Daggers and Keels

Daggers and Fixed Keels

The standard design comes with daggerboards and cases with fixed keels available as an optional design feature. For kit construction the price of the materials is the same or both options.

 

 

 

 


Construction

Raku 40 is built in composite with glass skins, PVC foam cores and epoxy resins. The hull shoes are moulded by strip planking. Everything else is built from flat panels except the forward curve in the wing deck which is kerfed, and some kerfing in parts of the cabin top.

Carbon fibre reinforcing is deployed for chain plates, daggers, rudders, the longeron, forebeam and strategic reinforcements in the structure.


Build Options

At the time of writing we have one builder in Europe preparing quotes for a full build.

If you choose to build yourself or manage your own build there are two opions:

OPTION 1.

Purchase a Duflex kit from VDL Composites in Germany if you're in Europe. In other parts of the world ATL Composites in Australia will manufacture and supply the kit. The kit price includes the plans fee and builder support.

For DuFlex kit pricing contact Tony Grainger

graingerdesigns@gmail.com

OPTION 2.

Purchase plans (including the cutting files for the panels) and manufacture or commission a supplier to manufacture you own panels. Note that the panels should be vacuum laminated or infused and you need a CNC cutter to cut the panels to shape, If you dont have facilities to CNC the laminated panels you will need to make templates from the cutting files.


Full Panel Kit for Raku 40