Global cruiser concept - 25m stabilised monohull

I am a yacht designer for 30 years and have travelled many thousands of miles at sea in sailing/power catamarans and monohulls in the Tasman/Coral Sea, Bass strait, Pacific and Atlantic oceans. I understand the compromises of these types of hull forms and found them all to be lacking in varying ways.

I live in Australia and am at the stage of designing and building my own ‘retirement’ boat for world cruising/live aboard with me and my wife - I have come up with a criteria list:

• Power, not sail – sails, masts and keels are not cheap, you still need a diesel engine, and I am getting too old for drama, and the compromises on space of a sailing boat are too much
• Fast, efficient hull configuration capable of sustained 250 nm/day speeds and much higher sprint speeds, all whilst burning small amounts of fuel. The world is far too big for boats that go distances at 5 knots. Real world range of 4000nm plus at these speeds – the Pacific Ocean is a large place
• Comfortable at sea and anchor without mechanical or rigged stabiliser systems. Motion of cats not great in a seaway, nor unstabilised monohulls
• Ability to go upwind, to punch into a sea. Cats suck at this as do wide monohulls and the sea seems to be rarely flat, and often going the wrong way
• Ability to go downwind/down seas at pace with ease and control. Big rudders and good steering moment generation. Good quartering seas ability
• Onboard spaces suitable for a couple and friends, with a split of casual and sleeping areas in line with a modern apartment. Indoor/outdoor spaces with excellent ventilation, including forced ventilation for all cabin – deck/topside hatches useless at sea
• Large amount of deck space for outside living and flexibility of entertaining. Vessel suitable for casual commercial use (day charter)
• Seriously serviceable equipment with full access to all important equipment.
• Full headroom engine room, separate workshop
• Direct crane access for generator/main engine install/removal
• Oil change system for main, gearbox and generator
• Full size intake/discharge sea chests
• Fuel day tank with polishing system, fuel transfer between all tanks
• No inaccessible serviceable items, removable panels as needed
• Significant solar installed and an independent in-port/get home electric propulsion system
• Dry out ability, protected drive lines
• A kick arse tender and anchoring system as I don’t want (or will be able to afford) to be in a marina at all
• Built to Australian commercial vessel standards for open ocean use, Lloyds SSC structures, IMO standards for damaged/intact stability

I have come up with a stabilised monohull design to meet these requirements (like a trimaran but with very small volumes in outer hulls). Looking for thoughts and feedback on this design to meet the above brief.

Paul

 

Here are some details of what I am thinking:

 

You can make a smaller replica of Adastra



Or just a plywood replica of Grainger Venom trimaran and bring a schooner shorter rig to avoid wind and wave capsizing

Easy, cheap and fast to self-build with your friends mounting CNC cuttings and even recycled wood strips




This is partial wooden trimaran barracuda


Sails can be made cheap with hemp fabric and webbing with few layers stitched following Sailrite tutorials

 

Paul. Welcome to the tread. You are more aware than most of the actual needs of a sea going design. Yes a tri design can be made more comfortable than a cat to minimise snap roll over wave crests can be done especially if the tri has has small slanted foils on the floats to help minimise roll, The balance between foil size and roll reduction without any moveable parts will take a little work to estimate. The remaining requirements of main hull length to beam, Malcom Tennant canoe stern, wave interactions between main hull and floats etc you have your own opinions on and access to research from various sources. As Scott Juston said to me one day after working for Austral, this is all about pressure distributions along the hulls. Get it right and you get a 10% plus range and/or speed difference. Finally keep it light if you can but with your experience your will a good idea of the real payload you are going to need. Have fun and I hope we get to see photo's of the built power tri in interesting locations.

 

Thanks for the comments, I worked for Scott for 4 years in Sydney back in the days of that designing custom race boats for people in Australia was a thing. I think your remarks are on the money - lightweight and correct volume distribution.

 

A friend of mine built a 60 foot power trimaran called ringo. He started with the stabilised monohull idea as well. He started with a smaller beam and smaller volume floats. This was his fourth large vessel design and build. He also had many years liveaboard experience. He soon changed his ideas on the design finding it uncomfortable in an average sea state let alone bad conditions. He returned the boat to the hardstand and increased the beam dramatically and also the volume of his "floats". He ended up with a 40 ft beam on a 60 foot boat. The boat was super efficient and very comfortable. He sold the boat and it was subsequently damaged in the Bundaberg floods around 2011 I think. It was recovered and remodelled badly. The "floats" were replaced with old sailing catamaran hulls with way too much rocker and a very low prismatic coefficient. I do not have any information on the boats current performance. It was a fantastic boat sitting on 16 knots all day at around 2.5 nautical miles per litre. A real ocean greyhound!

 

Do you remember engine/s type ? No pictures at all ?

 

Was a single engine. Sorry no pics. I went on the vessel at anchor in very bad conditions and it was amazingly stable. I own a 44ft catamaran and his vessel was amazingly calm compared to my boat in the same anchorage. It was also fantastic under motor especially surfing downwind in 20 knots plus conditions. If I was younger I would attempt a similar build. I really like the concept of a powertri but not with narrow beam and small floats. In beam seas it virtually sat flat as well. The greatest drawback with the concept is hardstand or marina berths. The footprint is too large for many facilities. Conversely the need for such facilities is significantly diminished. The liveability and ability to beach the boat for maintenance reduces the requirement to use such facilities. Think somewhere between the neel trimaran and cable and wireless from nigel irens for the basic outline.

 

Ilan voyager nigel irens ?

 

No comments as per your request. Malcolm Tennant Domino meets your plans I believe. fyi

But not likely available.

 

Ilan voyager and cable and wireless are similar. Cable & Wireless Adventurer - Nigel Irens Design https://nigelirens.com/boats/power-boats/cable-and-wireless/.