Multihull Structure Thoughts

This is another dream yacht that I thought was just a concept design. I was wrong, at least the first part of the build has been completed and delivered to a new location for hopefully completion. The Daedalus 100 uses new design concepts, cutting-edge engineering, and new systems to achieve a high quality and green performance catamaran for blue water sailing. The key concepts behind the design and engineering choices are simplicity, reliability and easy/low maintenance. Finite element (FE) calculation methods were used to study stress areas and optimize fiber orientation, laminate weights, and structures using high-security factors. Computational Fluid Hydrodynamics (CFD) allowed the optimization of the flow along the hull and around foils, to find the best configuration of drag, lift, stability and control. The hulls are not designed to any rule but more to be balanced, fast and forgiving under all conditions.

There are not many details of the Daedalus 100 that I have found but it appears to be 100 x 43 foot with a 146 foot high carbon mast. The hull length to beam of about 13 to 1. There are carbon fibre C foils of 16 foot draft that can provide 15% (of the displacement) lift. The power for the D 100 uses twin electric motors connected to the propellers, powered by a large battery bank. When the propellers rotate the electric motors generate power to recharge the high power lithium battery bank. An interesting aspect is that once the batteries are topped up, excess electrical energy will be stored as hydrogen. The Daedalus team calculates continuous free power of over 50kW is achievable. Additionally, the yacht can convert seawater to hydrogen using solar and wind power with the help of the on-board H2 generator, further extending the zero emission range. This is leading edge technology that I would like to understand more about.

The D100 also has gull-wing style doors amidships and an underwater viewing lounge. The four guest cabins aft and amidships all have queen size berths. She has three helm positions for ease of handling and docking and control lines are all led to the central interior helming station. The jpeg of the main saloon indicates a large galley to port with a central dining table and seating to starboard. A full internal helm station is forward. The cockpit is integrated with the main saloon through big glass doors.

The construction is built using female-moulded, vacuum-cured, pre-preg carbon and epoxy foam sandwich construction. The longitudinal stringers, crossbeam, longeron, rig and chainplates are all in carbon. A Kevlar outer skin provides waterline abrasion protection and a carbon and Kevlar inner shell give it protection from ice and allow it to be beached.

The theoretical performance is very interesting. Quote “Under sail she’ll be cruising above 20 knots all the time in the trades and the VPP predicts 36 knot capability in 24 knots of true wind.” If the D 100 is light enough and the sails good enough I can accept this is possible, but this cat will depend on electric winches and a very good crew to achieve these performance numbers.

The jpegs will give an idea of the cat. I want to read a sailing test report.

 

The following is about perfection of design process versus let’s get it done. A university project decided to design a “Hydrobike”. A human powered catamaran hydrofoil supported bike that could be peddled by 1 person. OK, creativity 1, engineering development 1, why would you do it? Maybe half.

This fine vessel is 7.1 x 3.2 foot with a displacement of 201 lbs. The hull draft is 100 mm. The power is cyclist peddling onto a drive system with an underwater propeller. There is a lifting foiling underwater. According to the data obtained from XFLR 5 plane wing analysing software, Wortmann FX 74-CL5-140 foil (FX74-CL5-140) has the best performances compared with other studied foil. And even it has the highest lift coefficient for given range of angle of attacks compared with other foil sections. The foil has a span of 3.2 foot and a cord of 30 cm (about 1 foot).

Now we get to the hull form design. I will quote from the designers: “Hull form is dependent on the Froude number of operating speed. From available data volumetric Froude number in operating range is calculated as 1.91, which is a quite high for a craft of this size. Therefore, to achieve the required speed a planning hull has to be used which has the best operation conditions above 1.00 Volumetric Froude Number. Then several planning catamaran hull series were considered such as Series 62 Hard Chine Planning Hulls, USCG Systematic Series of High Speed Planning Hulls and Series 89’ VWS Hard Chine Catamaran Hull. In addition, several research papers also referred. From all of these 89’ VWS Hard Chine Catamaran Hull was identified as the most suitable hull form. Because it has better hydrodynamic properties as a planning catamaran hull. DelftShip software package was used in the initial development of hull. Initial design lengths were given to obtain a basic hull from the software. Then resultant surfaces were modified according to the lines plan of Series 89’ VWS Hard Chine Catamaran Hull.”

So far, good academic stuff for the students. Now the construction. After completion of the mould construction began. Two coats of Gel-Coat with required pigment was applied. Then glass fiber mats were laid up followed by the epoxy-resin according to the schedule. To strength the shell, frames of square sections were added. Frames were built separately and attached to the shell by talc putty. Next a layer of glass fiber mat is laid on it to strengthen the frames. Finally, hulls were taken out from the mould after curing for two days. The deck joining two hulls were manufactured by GFRP. Then glass fiber mat and epoxy resins were applied to join the bridge deck to the hulls.

The jpegs show the build. There is no indication of the vessels moving on water or if it ever “flew” on its hydrofoil. But a lot of academic work to design a perfect solution. Now a quick and dirty protype could have been knocked up in a short time to prove the concept before a lot of excellent design work was put in. The jpegs give an idea.

 

Ah yes, they spent a lot of time planning the planing.

 

If the vertical struts will really be just four round tubes, then the electric assist will have to work hard to overcome that drag. Being in the wake of the pedal-driven forward propeller probably doesn't help. I suppose that might be mitigated by the propellers rotating in opposite directions, but judging by the propellers in the pictures, they don't plan on doing that. A single propeller and an electric motor attached to the pedals might be more efficient. I also don't see anything that would give the vessel either longitudinal or transverse stability in flight, unless they try do take care of that unicycle-style by turning and acceleration. That is not mentioned in their poster.

 

The John Marples designed Seaclipper 16 is a nice trimaran for day sailing. It comes in several formats from a tandem sailor to an open cockpit version. The early versions had either a fixed beam or a simple hinge system to fold floats up. The open cockpit version came with a swing wing option which is now the default plan.

The tri is 16 x 11.3 foot folding to 7.5 foot in the swing wing version. The dry weight 400 lbs with a 400 lbs carrying capability. The sail area is 146 square foot with a 21.5 foot mast using a standard Hobie 14 mast, boom and mainsail with “Turbo” jib Hobie 14 mast step. The length to beam of the main hull is 9 to 1. The float length to beam is 13 or 14 to 1 depending on sailing conditions. The draft is 0.9 foot (280mm) hull only and 2.6 foot with the main hull centre board down. The maximum outboard is 4 HP.

The hull shapes are simple flat bottom approaches that are easier to build. I said easier not easy as the float is a slightly asymmetric truncated V bottom with an angle. Not hard but follow the plans carefully.

The material list is below for the open cockpit swing wing version. The decks are 9 mm ply because Marples thinks by the time you do framing and stringers for lighter ply you end up with more work for only a small weight saving. The hull bottoms are 9 mm ply. The main hull sides are 6 mm ply. Bulkheads are 6 mm plywood with 19 mm timber framing. The stringers and gunnels are 19 x 32 mm approximately as some stringers require an angle cut on some faces. Cockpit wing seats are 9 mm plywood. The floats are ply timber again. All external surfaces are covered by 135 gsm cloth in epoxy. The forward timber swing arms are 2 layers of 19 x 240 mm timber. The aft timber swing wing cross arms are 2 layers of 19 x 190 mm timber. The main hull timber supports for the forward swinging cross arms are 3 layers of 19 x 240 mm timbers and aft 3 layers of 19 x 190 mm timber. The pivot and locking pins are 12 mm bolts. The floats have a 9 mm ply disc on top of the 9 mm ply decks with a 19 mm x width of the beam timber from gunnel to gunnel below the deck next to a bulkhead. The centreboard case has 6 mm plywood sides with timber support logs either side top and bottom. The cockpit floor is 9 mm ply and a real strengthener for the centre case and main hull sides. The kickup fixed rudders system is very good. This is a strong boat.

The performance of the Seaclipper 16 is good. In your comfortable seated position, it will achieve 10 knots without much drama, and you will go upwind well with the centreboard down. The boat will go faster, but the sails can also be reefed to reduce power and speed as required. My simple calculator says 8 knot averages and 15 to 18 knot peaks (you will be getting a little wet at this point).

This is a very well designed simple to build trailer day sailor. Build it well and it will outlast you. The jpegs give an idea. The general material list follows. Some of the timber sizes will require cutting to make eg several stringers etc.


Plywood – marine grade, solid core, water proof glue, 4’ x 8’ (1.219M x 2.438M)
7 sheets ¼” (6mm)
5 sheets 3/8” (9mm)
Lumber – straight, clear, dry, vertical grain fir or equiv.
3 pcs. ¾”x 3 ½” (19 x 89mm) x 16’ (4.88M) stringers, glue strips
2 pcs. ¾” x 5 ½” (19 x 140mm) x 15’ (4.57M)stringers
3 pcs. 1 ½” x 3 ½” (38 x 89mm) x 8’ (2.44M) coamings, stems
Hardwood – mahogany or other
1 pc. 1 ½” x 3 ½” (38 x 89mm) x 3’ (914mm) tiller
Western red cedar
5 pcs. ¾” x 3 ½” (19 x 89mm) x 8’ (2.44M) daggerboard
Akas – straight, clear, dry, vertical grain fir or equiv.
3 pcs. ¾” x 7.5” (19 x 191mm) x 8’ (2.44M)
2 pcs. ¾” x 7.5” (19 x 191mm) x 10’ (2.54M)
3 pcs. ¾” x 9.5” (19 x 241mm) x 8’ (2.44M)
2 pcs. ¾” x 9.5” (19 x 241mm) x 10’ (2.54M)

Epoxy
12 gallons including hardener.
6 lb. wood flour filler
3 lb. silica thickener
misc. supplies – gloves, mixing cup and sticks, squeegees, etc.

Fiberglass cloth – 4 ounce (135 gr./sq.M), plain weave or twill
75 yds. x 38” (965mm) wide

 

Seaclipper 16 part 2 jpegs

 

"Tri-Umphant"
I love it!!

 

This will give an idea of what is required to sail really fast in the OMRA era. This design was done by a “student” in Naval Architecture. The design was very up to date for about 2003 and not to far away from some of the later designs and builds.

60 x 60 foot with a weight of 13,100 lbs and a displacement of 15,500 lbs. The 93 foot (OMRA rules say can be 100 foot) rotating carbon fibre wing mast carries 2200 square foot mainsail, a 930 square foot jib, a 1200 square foot Code 0 and spinnakers up to 3,500 square foot. The draft is 14 foot over the central hull daggerboard. The floats have lifting C foils. There are rudders on all hulls. This is a 2003 design and the floats have finer sterns than the later designs which had fuller floats as the OMRA tris started to sailing like a wide cat with a very slim central hull.

This tri is all about racing with effectively one berth in a cabin set up for navigating and weather routing. There is a minimal galley food area.

Construction is virtually full carbon fibre epoxy foam sandwich. The structural engineering required to balance the rig forces to foil forces through a lightweight structure is difficult. Torque forces are large and X configurations help, but making the structure stiff enough to keep the C foil angle of attack correct whilst sailing is very interesting.

The performance of these designs were very good. Speeds up to 35 knots were common, some claim speeds of 40 knots at peaks. most of these tris can do twice wind speeds. Averages up to 28 knots over 24 hours have been recorded but the real capability is upwind in moderate conditions with massive rigs and really deep boards. In the full foiling era VMG is the main game and this does not always mean a narrow tacking angles.

The jpegs give the idea.

 

Some great pictures of the seaclipper 16. A nice simply common sense buildby the looks.
The marples seaclipper web site seems to have disappeared, anyone know anything about that ,are plans available somewhere else?

 

Adrian. I suspect Marples has retired and his web site has recently been shutdown. The only Seaclipper plans being sold are the Seaclipper 20 ($470) is by Woodenboat plans. I cannot find the Seaclipper plans being sold elsewhere. Anyone know if the Seaclipper 16 plans are still available?

 

I forwarded your review of the 16 to John Marples. I'll see what he says about plans.

 

This is a simple Pacific proa for those who want to experiment and still have a practical boat capable of carrying 2 crew for day sailing or camp cruising.

20 x 8 foot over all with a float being 12 x 1.2 foot and a weight of 250 lbs and an approximate maximum displacement of about 700 lbs. The unstayed 15 foot mast (above deck) with an 89 square foot lanteen sail. The boom is 11 foot and the yard is 19 foot. The main hull length to beam on is 8 to 1 when loaded. Float length to beam 10 to 1. The draft over hull is 0.3 to 0.5 foot depending on load. The draft over the kick up rudders is 2 foot.

The construction is mainly plywood skins, bulkheads and timber stringers, gunnels and framing. The plywood is 6 mm. Most of the chines are taped seams. No jigs and or lofting. Simple and quick. The steering arrangement are kickup lee boards at either crossbeam. The concept is simple but the build will not be hard but a little tricky.

A bit of fun, simple to build and capable of moderate speeds up to probably 10 to 12 knots.

 

The following is a creative Bernd Kohler solution to a houseboat for protected water. The ECO 62 houseboat can travel trough the majority of Europe’s canals and rivers. Or down the Mississippi etc in the US. If you pick your weather, you could do short coastal trips. The major limitations are the payload capability and the windage of the design. In light winds you could cruise with 10 HP but in stronger winds it will require either two 10 HP or EG a single of 25 HP.

The ECO 62 houseboat is 20 x 8.2 foot with a weight 920 lbs and a displacement of 1,075 lbs. The draft is 0.75 foot. The total height of the boat is 8.5 foot with 7.75 foot above the water line. The power can be 2 electric (150 lbs thrust) trolling motors (one aft, one forward for control) giving about 5 knots, a single 10 HP outboard gave 6 knots at 30% throttle and EG two 20 HP outboards should give about 20 knots. The motor options depend on the area you will travelling in. A quite lake will require less power than a flowing river or high wind area. There is a roof top solar array that can provide EG 2 KW of power to a battery bank. The boat is light enough to be a real trailer sailor with medium size vehicle.

The accommodation provides a double berth under the foredeck. The helming station is on the starboard side with a hanging closet to port. There is a reasonable galley with a dinette opposite. In the aft port corner is an enclosed toilet. The 8 x 4.4 foot cockpit aft provides a great place to watch the world go by. Headroom throughout beside the double berth is 6.4 foot. This is an excellent little house for a week at a time.

The construction is mainly plywood and timber. The design is built around 5 bulkheads and wooden stringers. A hull weights around 50 kg when finished and is attached to the bridge deck. The bridge deck is built up from 12 mm plywood. A 12 mm plywood panel weights typical 18,3 kg (about 41 lbs). So, it can be handled by one person. All other plywood used is 6 and 4 mm plywood. Laminated together where need. EG Keel to chine is build up from two layers of 6mm plywood. The roof is an arched construction probably of 4 mm ply either side of internal arched frames and foam sandwich. The build time is projected at 800 hours for a straight forward build. Get fancy with a high quality interior you could add another 1000 hours.

This is a good design for 2 people to get away from it all for a week. The jpegs give the idea.

 

Part 2 of the ECO 62 houseboat

 

Bernd Kohler power designs come in several sizes but we will focus on the ECO 75 which is a power catamaran that is capable of doing both inshore and coastal cruising. The ECO 75 has lower windage and a higher bridge deck clearance from the water than the ECO 62 houseboat from yesterday. This means the ECO 75 only has headroom in the hulls and the open cockpit but in exchange you get a cat that is faster and more capable in a seaway.

The ECO 75 is 24.6 x 10.6 foot with a weight of 1,800 lbs and a displacement of 3,130 lbs. The hull length to beam is 9.50 to 1. Draft is 0.85 foot. The power can be outboard(s) between 20 and 40 HP. It can reach around 25 knots with a 40 HP engine, or 18 knots at half power. There is a solar (miniumum of 400 watts) battery electric option available with about a 40 KM range. The power could be 2 x 10 Kw Torqeedo pod's, one under each hull or EG 2 x Torqeedo Cruise 4.0R. The battery packet will be a LiFePo4 48 Volt 400 Ah, which has a weight of about 250 kg. this is a customer suggestion and they think they will get 10 to 12 knots speed.

The cat has 2 single berths and a convertible dinette double berth on the bridge deck. The height on the bridge deck saloon is 4 foot. Just enough for seating on the settee. The hulls have standing headroom in the galley/pantry and the toilet. There is a forward and aft cockpit. The Aft cockpit can be covered by a large bimini for sun protection etc.

The structure of the design is plywood and timber covered with epoxy. The planking for the chine hulls has a constant radius and is tortured plywood in some spots. The hulls are 6 mm plywood side and two layers of 6 mm ply on the bottoms and have biaxial glass 340 gr/m2 and one layer 200 gr/m2 glass fabric. A later version of the structure says that the ECO 75 hulls are mainly built of 8 mm plywood with I suspect 2 layers of 4 mm plywood in the lower forward portion of the hulls with the strong concave curves. The roof is 2 layers of 4 mm ply and forward under wing is likely to be 3 layers of 4 mm ply. The under wing is 12 mm ply. The attached sample PDF plan gives more details of the structure. The jpegs show the hull bulkhead and stringer layout arrangement.

Bernd made a comment about plywood which is relevant: “. My advice on plywood used in my plans is Ocume plywood which is produced many countries… Many customers in the USA use Fir plywood which is building something for a short life span, not advisable. Best plywood you can get is marine plywood from Bruinzeel plywood factory, Netherlands or Joubert, France. You can get these products in many countries. On the other side, I used unknown waterproof okume plywood for some of my 14 boats I built, without any problem. EG PELICAN that is 28 years old. The wood/fiberglass/Epoxy system makes the difference to get a durable boat.”

This is a smart design with each component adding value to the overall strength whilst providing privacy as required. Also, the forward cockpits entrance by a door from the galley hull side is an interesting design feature.

This is a good economical power cruiser for those who like to do some coastal cruising or have large exposed bays to travel around in. A good option for a few weeks of relaxed travel. The jpegs give the idea.