Multihull Structure Thoughts

[oldmulti]

The EC24 power catamaran is from the following web site: Power Cat Boat Plans - Boat Builder Central https://www.boatbuildercentral.com/product-category/boat-plans/multi-hull-boat-plans/power-cat-boat-plans/

The catamaran can be powered by fuel or solar power with batteries. An interesting design and if you want more detail or the plan the above address is an excellent place to start.

The E stands for Electric Catamaran or Economy Cat or Efficient Cat the design is all that. The cat is 29.75 x 8 foot or can be built up to 10 foot wide. The displacement (I suspect is weight) is 2000 lbs with an immersion rate of 295 lbs/inch. Now we get to the interesting part. This cat can be powered by two 5 HP outboards or a single outboard or be solar/battery powered by EG Electric motors like the Torqeedo Cruise R 4.0 “outboards”. Batteries can be recharged by solar panels mounted on the roof or dockside or on the trailer. A small quiet generator can be kept onboard to recharge the batteries. Performance will depend very much on weight. Lightly loaded, with a pair of Torqeedo's 4.0 and two battery sets, the boat will cruise all day long at 6 mph, top speed above 10 mph. With 2 modern 600 watt solar panels charging your batteries you will be able go a long way without recharging. With a pair of small gas outboards 5 HP each, performance will be the same than with the electric motors. With larger gas motors, 10 HP max., the top speed will be around 15 mph with no range limitation.

The build material of the cat is fiberglass epoxy on a plywood core which is stiff and light which helps a relatively efficient catamaran hull. The chine hull section is made of five panels with a narrow bottom. The hulls are fine and the long waterline provides minimum resistance for a given speed.

The thin plywood acts as a core between layers of e-fiberglass in epoxy. The assembly is done by stitch and glue. The E Cats are built in 4 parts: 2 hulls, a set of cross beams and the deck. The hulls are built one or two at a time, the beams and some of the deck furniture are built separately from the hulls. After completion of those parts, the hulls are joined by the cross beams, the assembly is fitted with a deck and deck components are added. The E Cat hulls are built upside down on a jig made from the plywood frames or from throw away molds. The following chart gives the bill of materials for the basic hulls and bridge deck. Any seating and Bimini top is extra material.

Plywood standard sheets 4x8'

12 mm (1/2") 2 sheets

10 mm (3/8") 7 sheets

6 mm (1/4") 11 sheets

Boards and Battens

25 x 75 mm 120 feet

25 x 25 mm 100 feet

Fiberglass fabric 1250 mm wide or tape 150 mm wide (totals)

Biaxial tape 45/45 12 oz. (400 gsm) 1200 foot 366 meters

Woven fabric 6 oz. (200 gsm) 50" wide 105 foot 32 meters

Woven tape 9 oz (300 gsm) 4" wide 19 foot 6 meters

Resin Epoxy, total 35 litres 30 Kg

An interesting design. The jpegs are from the design brochures.

 

[Dejay]

Interesting boat, wasn't on my list yet. Building with foam core might save you money on motor and batteries and make those 600W more effective.

I'd be curious if people think the EC24 is overbuild with 900kg weight? Or that just the limit of what you can do with plywood in that size with good conscience?

Most boats seem to be designed very heavy, but some are incredibly light. For comparison the 7.5 m / 25' harryproa E25 weights 140 kgs. The plywood mini cargo ferry is 500kg.

 

[SolGato]

Interesting boat, wasn't on my list yet. Building with foam core might save you money on motor and batteries and make those 600W more effective.

I'd be curious if people think the EC24 is overbuild with 900kg weight? Or that just the limit of what you can do with plywood in that size with good conscience?

Most boats seem to be designed very heavy, but some are incredibly light. For comparison the 7.5 m / 25' harryproa E25 weights 140 kgs. The plywood mini cargo ferry is 500kg.

Weight IMO is not nearly as important as hull efficiency, the amount of wetted surface area, and the amount of windage above the waterline with regard to electric non-planing cruising type boats.

With electric motors providing linear torque, you can push a very large heavy boat with a very small motor and prop.

From my experience, wind and current become more of a factor and will determine if you have adequate thrust to operate efficiently and maintain control of the vessel.

Point is, I would be more focused on the shape of a boat below and above the waterline, much more so than the overall weight when designing an electric cruiser.

However with regard to weight and the EC24 design posted above, balance and center of gravity are also very important, and I would be concerned about the weight of panels that large and the substantial support they would require. Too much weight up high on a small boat like that makes for poor handling, which in turn would cause inefficient use of the motors.

 

[oldmulti]

The following cruising catamaran is sold as a modular kit catamaran for professional or home construction. The Max Cruise Marine MAX 42 SC cat is 42 x 24 foot with a weight of 12,200 lbs and a displacement of 17,500 lbs. The 53 foot aluminum or carbon mast carries a 731 square foot mainsail, 327 square foot self tacking jib and 840 square foot Code 0. The mast has a spreaderless rig. The hull length to beam is 12.2 to 1. There is an option of daggerboards that draw 5.75 foot or low aspect ratio keels that draw 3.8 foot. There are fixed spade rudders. The underwing clearance is 2.65 foot. Two 30 HP inboard diesels are the motive power.

The 42SC sailing catamaran is available in 2, 3 or 4 cabin layouts, and 2 heads/showers. There is also some flexibility available with the bridge deck salon cabin general arrangements. The main feature of the accommodation is it is mainly aft of center. The mast is placed in the center of the cat. This allows better reaching power, less pitching and if wanted finer bows for upwind work.

The main feature of this cat is its build options. The 42 SC is built from 3D Modular (3DM) moulded components which are naval architect designed and constructed using CNC technology to exacting standards. The Vietnam factory produces hull modules 3D moulded, deck modules 3D and moulded cabin top modules 3D moulded. The cockpit benches 3D moulded, fore beam, catwalk ('longeron') are 3D moldings and the rudder halves 3D moulded. Bulkheads and furniture are 2D moldings. There are assembly and technical drawings. All 2D and 3D modules are Vinyl-ester resin infused sandwich with PVC structural foam core, some components have a Gelcoat exterior. If you want to build at home all the components are delivered in two 40 foot containers to your door step. One of the jpegs show a couple standing in front of hulls and a bridge deck. The containers were delivered 2 days earlier, they got to this point in 48 hours with a group of friends.

A precise design and manufacture process enables significant reductions in build times, labour, build space costs (such as rent) and reduced wastage of consumables in comparison to other kit boats. The time to build from the kit components to a completed 42SC exterior according to the company is for a professional yard is 4 to 5 weeks. For a home builder with 3 other people the company claims the external shell can be done in 8 weeks.

Please remember an external shell even with some furniture components installed is still at least a year away from a launch for most home builders as the plumbing, electrics, fittings, engines, galley equipment, rig, sails, trampoline netting etc. just take time in design, acquisition and installation.

The 42 SC can also be completed by the Vietnam factory to a ready to launch cat. There are no performance tests yet as there are no fully finished boats yet. The numbers look good and I suspect this will be a high performance cruiser with 8 to 10 knot average capability and peaks close to 20 knots.

The jpegs give the idea. An interesting design that is worth a follow up. the web address is: Max42SC Sailing Catamaran https://maxcruisemarine.com/max42sc-sailing-catamaran/

 

[oldmulti]

The Seaclipper 34 is designed as a capable offshore passage maker for extended cruising. John Marples is the designer which will ensure it’s a strong, good to very good performing trimaran. The Seaclipper 34 is 34.4 x 23.3 foot that weighs 5600 lbs and displaces 7600 lbs. One builder choose quality lightweight materials and had a launch weight of 4900 lbs. The tri has a fractional spreaderless 40 foot aluminium mast that has a 7.5 oz 290 square foot mainsail, a 6.5 oz genoa of 326 square foot, a 6.5 oz jib of 126 square foot and a 7.5 oz 42 square foot storm jib. Some owners have put on 4 oz light wind genoa’s and spinnakers. The main hull at the gunnels is 6.6 foot wide and at the waterline approximately 35 foot wide giving a length to beam on the main hull of 9 to1. The draft of the centreboard in the main hull is 5 foot. There is a kickup stern mounted rudder.

For coastal cruising, the floats can be dismounted for overland transport and for winter storage. The Seaclippers tapered box cross beams slide through the hull and bolt to main strength bulkheads and drop into the float mounts. Very easy for assembly or disassembly, but please remember this is many friends or a crane to help with the task. This is not a trailer sailor. For offshore sailing, it is recommended that the boat be glued together permanently.

The 34 is designed for a crew of 2 in long term voyaging. It has standing headroom in the main cabin. The aft cabin is a full-berth layout with privacy. Wing pods to expand the main cabin are optional. There is a single berth, at double, seating and galley in the main cabin with a loo forward. Yes, you could add extra space in the optional wing pods but the major restriction is the 1600 lbs payload. To maintain the tri’s sailing performance the displacement is limited and as john designs strong boats, the payload is limited. EG the water tankage is 80 litres and fuel is 40 litres.

The Seaclipper 34 is built from plywood and timber. The hulls are planked with 9 mm plywood on stringers and timber framed plywood bulkheads. The hull bottom is slightly rounded and probably moulded from 2 layers of 4.8 mm plywood. The centreboard case is a major structural element and is integrated with the internal furniture. The floats are a simple V shape with a stich and glue keel line. The timber and plywood box beams are relatively easy to make compared to folding trimaran mechanisms. The entire tri should be epoxy coated with a light (eg 1 or 2 layers of 300 gsm cloth) e-glass layer on all external surfaces. Expect to spend 1 to 2 year build times according to the designer.

One owner comment that the tri sails well on all points of sail especially upwind and in light winds. The tri is very easy to control on all points of sail. The inboard 6 HP BMW D-7 diesel drives the tri at 7 knots. This is a very practical easy to build cruiser for those who want to go offshore. The jpegs give the idea.

 

[oldmulti]

After the Seaclipper 34 yesterday today we feature the Seaclipper 38 which is 4 foot longer but has a larger internal and more practical accommodation with a better payload capacity. The Seaclipper 38 is 38.25 x 25.5 foot that weighs 8,000 lbs with a displacement of 11,000 lbs. The 46.5 foot aluminium spreaderless mast carries a 320 square foot mainsail, a 450 square foot genoa and a 270 square foot jib. The mainhull centreboard draws 6 foot. The rudder is a kickup in the stern. The mainhull length to beam is 8.75 to 1.

The engine power is either an outboard or 20 HP inboard diesel. One owner tried the outboard option but found in rough water the outboard lacking and changed his engine to a diesel. The diesel pushes the tri at 8 knots under most conditions. The water tankage is 200 litres and 80 litres of fuel.

John Marples did the design mainly for liveaboards and extended offshore cruising for up to 3 people. The twin cabin arrangement allows privacy for two couples. The main cabin features galley, dinette, and head facilities. Other arrangements are possible. The central cockpit helps centralized weight and protect the crew.

The Seaclipper 38 was designed as a cost effective alternative to a EG Searunner 37 and is much simpler to build. An excellent choice for a home builder. Since the design is based around using lumberyard grade materials the weights and displacements that are listed are a little high, you can build a lighter tri with upgraded plywood (EG Okuome) and keeping it simple. One person thinks something like a Seaclipper 34 could be built in 1/2 the time of the same size Searunner 34.

The Seaclipper 38 is built from plywood and timber. The hulls are planked with 12 mm plywood on stringers and timber framed plywood bulkheads. The hull bottom is slightly rounded and probably moulded from 2 layers of 6 mm plywood. The centreboard case is a major structural element and is integrated with the internal furniture. The floats are a simple V shape with a stich and glue keel line. The timber and plywood box beams are relatively easy to make. The entire tri should be epoxy coated with a light (eg 1 or 2 layers of 200 gsm cloth) e-glass layer on all external surfaces. Expect to spend 2 to 3 years build times according to the designer.

The owner of a rare Seaclipper 38 says he would like to own a version that was either built from flat panel foam glass sandwich or a plywood version built from 9 mm plywood. He thinks the lighter tri would be able to have a greater payload for cruising and would be a little faster. The other modification he would like to do would be to have daggerboards in the floats removing the centerboard from the main hull to gain a bit more room in the main hull.

The performance of the Seaclipper 38 is good according to the owner. It sails well to windward is capable of 10 to 12 knots sailing in moderate to heavy weather. He says it could go faster but he is a cruiser not a racer. He may not be a racer but he already has a 50 foot mast with a larger mainsail and headsail (it’s the rig from the Seaclipper 41 design). To quote the owner “Mine is the SC38 and it is a nicely balanced cruiser and comfortable and secure in heavy weather and will sail with a good turn of speed. The windward float does not touch the water except in very light air.” The tri is easily handled and has clear decks for sail handling etc.

The jpegs give the idea of the design. This is a very practical cruiser for those who want a tri that is easy to build.

 

[oldmulti]

The Drifter series of trimaran designs are done by Mark Gumprecht. Mark is a talented designer who has done designs from small day sailing tris and cats to a 22 foot bridge deck sailing catamaran. All are creative designs aimed at a minimal build time and low cost with good performance. The 2 designs featured here are the Drifter 12 and the Drifter 12L which has larger floats and rig. The Drifter 12 is 12 x 9.6 foot and weighs about 100 lbs.


The Drifter trimaran models are simple flat bottom designs, built out of 1/8″ mahogany plywood, with a free standing windsurfer mast, and a roll up sail. They have a lee board, a kick-up rudder, and are steered with foot peddles. The whole boat comes apart in 15 minutes and can go on top of a car, or on a small trailer. The amas on the Drifter 12 fit into the main hull, another way to transport it, and great for shipping.

They are easy to paddle, and really fun, and easy to sail. It’s great for inexperienced sailors, because you launch and land with the sail rolled up, and set sail once you are out on the water. It’s a very enjoyable way to get out on the water and explore protected bays, rivers, and lakes.

The build materials are for both the Drifter 12 and Drifter 12L are:

8 sheets 1/8" mahogany plywood
4 5/8" x 1 1/2" x 12' stringers (spruce or fir)
2 5/8" x 3/4" x 12' stringers
4 1/2" x 1/2" x 8' stringers
3 2" x 4" x 10' clear spruce or fir for beams
3/4" spruce or fir for leeboard and rudder
13 yards 50" 4 oz. fiberglass
2-3 gallons of epoxy
15' windsurfing mast

A few jpegs but the real gold is the PDF’s. Full, free plans with build description which Mark has now released.

 

[guzzis3]

The TRISTAR 24 flush deck design gives you a spacious interior and deck that makes for easy sail handling.

I've been watching this thread grow for ages but only started reading it the other day.

The folding T24 is fascinating. Here in queensland with our oversize trailering option you could in theory fit the 27-9 into the envelope. Apart from longer waterline you get 6' standing headroon without the bubble top and most important enough clearance over the bunks to sleep comfortably. I put this to Mr Horstman but he wasn't interested. If someone cared enough designing such a beast with a modern rig in foam wouldn't be that hard and give an easily (fairly!) trailerable proper family cruiser, or 2 couples. Enclosed heads with room for shower, decent galley, proper diner. Stuff you don't get even in a bridgedeck cat under 30'

Anyway back to the reading

 

[oldmulti]

The next in the Drifter series of trimaran designs done by Mark Gumprecht are the Drifter 14 and Drifter 16. All are creative designs aimed at a minimal build time and low cost with good performance. The 2 designs featured here are the Drifter 14 and the Drifter 16. The Drifter 14 is 14 x 10.9 foot and weighs about 120 lbs. The Drifter 16 is 15.5 x 11.25 foot and weighs about 130 lbs. The Drifter 16 is designed to carry 2 people if wanted.

The Drifter trimaran models are simple flat bottom designs, built out of 1/8″ mahogany plywood, with a free standing windsurfer mast, and a roll up sail. They have a lee board, a kick-up rudder, and are steered with foot peddles. The whole boat comes apart in 15 minutes and can go on top of a car, or on a small trailer.

They are easy to paddle, and easy to sail. It’s great for inexperienced sailors, because you launch and land with the sail rolled up, and set sail once you are out on the water. It’s an enjoyable way to get out on the water and explore protected bays, rivers, and lakes.

The build materials are for the Drifter 14 are:
10 sheets 1/8" mahogany plywood
4 5/8" x 1 1/2" x 14' stringers (spruce or fir)
2 5/8" x 3/4" x 14' stringers
4 1/2" x 1/2" x 12' stringers
3 2" x 4" x 10' clear spruce or fir for beams
3/4" spruce or fir for leeboard and rudder
16 yards 50" 4 oz. fiberglass
3 gallons of epoxy
16' windsurfing mast

The Drifter 16 materials are:
12 sheets 1/8" mahogany plywood
8 1/2" x 1/2" x 13' stringers (spruce or fir)
4 5/8" x 1 1/2" x 16' stringers
2 5/8" x 1" x 16' stringers
3/4" spruce or fir for rudder and leeboard (can be glued together out of strips)
3 2" x 5" x 11' 6" medium density spruce or fir for beams
3 1/2 gallons of epoxy
20 yds 50" 4 oz. fiberglass
1 16' or 17' windsurfing mast

A few jpegs but again the real gold is the PDF’s. Full, free plans with build description which Mark has now released.

 

[guzzis3]

The alternative way of doing a transportable catamaran is represented by the WALLER TC 750 (yes Tim Clissold TC 750 is not the (Trailable Catamaran) TC 750). In Australia you can get day light hours towing permits for boats up to 3.5 meters wide for travel through the majority of areas. The trailer can only be 2.5 meters wide but the boat can be 3.5 meters wide. Check your local state regulations. The TC 750 is 24.5 x 11.3 foot weighing 3000 lbs displacing 3700 lbs with a maximum displacement of 4500 lbs. TC 750 carries a 250 square foot mainsail and 150 square foot head sail.

....

Note that this vessel is wider than the standard road trailing width for most areas. Normally this yacht would live on a trailer frame at the local yacht club (much cheaper than a berth or mooring).

I've asked everyone I can think of how this works. As far as I can tell here in queensland the only people who can trail 3.5 meters are commercial heavy vehicles with permits. I have also been unable to find a path in other state to private vehicles trailering at this width. I would be extremely grateful if someone could point me at a document that explains how this can be done.

2.9 meters in queensland can be done with flags and sign, no permit required. Running lights at night. That's an "oversize" load. Wide load is a different animal.

 

[guzzis3]

Redreuben. The International 23 basics are ...

I put some time into researching the inter years ago. They were built all over the place at various times. If you look at boats that come up for sale some have the telltale holes for the main beam some don't. The ones that don't don't compress. They are fixed beam, demountable but not compressable. I almost bought a properly priced inter years ago until I realised it wasn't a slider.

A seawind 24 feels like an ocean liner by comparison, but they are a bigger boat than a windrush 600. The W6 is very fast though. A hard sailed one has done well in the bay to bay many times...

 

[oldmulti]

Guzzis3. For victoria read the following web site: Oversize light vehicles : VicRoads https://www.vicroads.vic.gov.au/registration/oversize-light-vehicles

Oversize light vehicle conditions and requirements
The Road Safety (Vehicles) Interim Regulations 2020 sets out the dimension limits and other requirements for Class 0 vehicles. In particular they may be up to 3.5 metres wide, 4.6 metres high and 25.0 metres long.

Class O vehicles can travel on all roads in Victoria except:

• in the Mountainous Area and the Otway Area (if the vehicle is over 2.5 metres in width and/or 19 metres in length)
• in the Gippsland Ranges Area and Colac–Surf Coast Area (if the vehicle is over 3 metres in width and/or 22 metres in length)
• on Main Roads (if the vehicle is a Class O agricultural vehicle or agricultural combination)
• on restricted routes.

For full details of Class O restrictions, including areas, routes and times, see Schedule 7 of the Road Safety (Vehicles) Interim Regulations 2020 and the Victorian Government’s Class O Specifications (PDF).

Last time I looked NSW had the sort of regulation, I cannot remember if it applied in QLD but as Waller is from QLD I suspect it is the case. Yes, it is possible if you are a good driver who is close to a launching ramp. it opens a world of possibilities for a serious coastal cruiser with headroom and a reasonable bridge deck accommodation.

 

[guzzis3]

Guzzis3. For victoria read the following web site: Oversize light vehicles : VicRoads https://www.vicroads.vic.gov.au/registration/oversize-light-vehicles

Thank you very much for that. It's the first indication I've had that that is legal despite asking people for years.

Up here everyone I've spoken to, including queensland transport, just advise it has to be a heavy vehicle etc, but there may be a regulation somewhere I've not been able to track down. I'll look again.

 

[oldmulti]

Guzzis 3. Please look at: https://www.publications.qld.gov.au...4-425c-9b3d-b5ecf221ac90/download/form-26.pdf

Max width in QLD appears to be 3.3 meters not 3.5 meters. A comment below from the above document.

Note: If dimensions of the over width vehicle/combination are above 2.9 metres to 3.3 metres in width, the operator may apply for a Vehicle Standards Exemption Permit using the Vehicle Standards Permit Application/Renewal form (F4880). The form is available at Home (Department of Transport and Main Roads) http://www.tmr.qld.gov.au. Applications will be assessed on a case by case basis and the issuance of a permit will be dependent on the applicant's ability to mitigate the risk of an over width vehicle travelling on Queensland's Roads. Widths above 3.3 metres are not eligible for road access when towed by a light vehicle. The load will need to be transported behind an appropriate heavy vehicle. For more information on the operating requirements and conditions, contact the National Heavy Vehicle Regulator (NHVR) via email info@nhvr.gov.au or call 1300 696 487

 

[oldmulti]

The following 2 designs are from Reichel Pugh design. I know very little about these designs as there is little information available but I present them as a sample of what high profile designers are doing to expand their portfolio.

The first is a 45 x 27 foot trimaran of unknown displacement with a 58 foot mast and about 580 square foot mainsail and about 570 square foot fore triangle. This design has been done in 2021 and has bridge deck accommodation with a forward and very large aft cockpit. This looks like a very comfortable cruiser with serious sailing capability.

The second design is a 45 x 26.4 foot very high performance catamaran. Why do I say that, curved daggerboards that draw 9 foot draft may give a hint. To quote the designers “The motivation to design this 45ft offshore performance catamaran started with a question from a prospective client. The client wanted a fast yacht for shorthanded offshore racing that also featured genuine cruising capacity”

The designers also said “To fulfil the design brief for a successful racing design all opportunities for performance advantage were investigated. The modern hull design exhibits a low rocker shape and reverse stem while maintaining a high-volume bow for reserve buoyancy with a flying knuckle to improve maneuverability.

The rig utilises an efficient rotating mast arrangement. The headstay, code zero and downwind sails are supported with a stayed longeron/sprit, eliminating the customary forward beam to reduce windage and pitching motion. C-shaped daggerboards provide leeway resistance as well as some vertical lift to reduce virtual displacement – also ensuring the bows stay up when the boat is being pressed hard downwind.”

The accommodation according to the designers “The interior arrangement features the owner’s quarters, a head with separate shower and the galley in the starboard hull. The port hull accommodation includes two guest/crew berths with shared head and a dinette area. The fit-out is simple but comfortable in keeping with modern design trends; numerous portlights and windows create a light and airy interior.”

The structure of these boats I would guess be a PVC foam glass sandwich with carbon reinforcements.

The tri would be a comfortable performance cruiser, the cat would excite most people with its speed and some accommodation. Interesting concepts. The jpegs give the idea.