Multihull Structure Thoughts

Mulkari has been wanting a new larger sailing cat that will be an open bridge deck sailing cat of simple construction and a reasonable hull shape that will give better performance than a Wharram and reasonable accommodation. Mulkari has a 30 foot tube cat that sails well but it lacks accommodation and “enough stability” for the type of sailing he would like to do. I will talk about 2 designs, one expensive to give the idea of what is possible versus a cheaper option.

Maine Cat designer/builder Dick Vermeulen launched the Maine Cat 41 in 2004. The Maine Cat 41 is 41.5 x 23 foot with a weight of 12,200 lbs and a maximum displacement of19,200 lbs. The aluminium mast carries a working sail 996 square foot and with a gennaker 1,290 square foot. The draft ranges from 2.5 to 7 foot.

The accommodations within the hulls. A large functional galley occupies all of the aft end of the port hull, with a double berth on an offset inboard shelf amidships, followed by a head, then a single berth right up in the bow. The starboard hull features a head with a separate shower stall plus a small dressing area aft, followed by another double berth amidships, then a nav desk and another single berth right forward.

The manufacturer claims the nominal hull speed -Light ship 13.3 knots, and with maximum payload 11.6 knots peak speeds. Owners claim the 41 has excellent helm sensitivity and with its daggerboards it can tack through 90 degrees in flat water. Owners claim top speed of 18 knots and several owners report hitting average speeds between 11 and 14 knots.

The entire boat–hull, deck, hardtop, and interior components–is built of lightweight vacuum-bagged composite laminate cored with high-density Corecell foam. Expensive, not simple to build but good.

The next design is Richard Woods open bridge deck Mirage. The Mirage is a later design Richard did to replace his deep V Mira open bridge deck design. The Mirage is 36 x 19.5 foot with a weight of 7,000 lbs and a displacement of 9,800 lbs. The 45 foot aluminium mast carries a basic sail area of 600 square foot. The hull length to beam is 12.5 to 1. The draft is 3.2 foot over fixed low aspect ratio keels. Richard Wood often does round bilge versions of his chine designs and daggerboards are easy.

The accommodation is double berths aft then in one hull a galley mid hull and seating/table forward. In the other hull a nav area, toilet mid hull with a double berth forward. Practical accommodation that works for EG 4 people cruising.

The construction is plywood on timber plywood frames and bulkheads with stringers. This could be reengineered to foam glass (as many other Woods designs have been). Richard Woods has done many designs around this size and for hime to mix and match design components is relatively easy (not a freebie) but fairly easy.

The Mirage design has already gone transatlantic, can hold “a solid” 14 knots in the right conditions, can average 9 to 11 knots etc. In short it can sail well on all points of sail and with an upgraded rig and daggerboards probably sail better.

The reality is the Maine Cat 41 is a production boat that will cost twice the cost of a Mirage. But the Mirage can be built at home, can be configured to you preference EG daggerboards, slightly different internal layout etc. The performance and internal space may be down 10% but at half the price I would be willing to do the trade off.

This as about what is important to you. The first set of jpegs is the Maine Cat 41. The second jpegs are the Mirage.

 

The Richard Woods Mirage catamaran accommodation layout and hull cross section.

 

Looking at the numbers it is really a apples and oranges comparison with the Naria MK4. Yes the other boats will sail faster but the Naria can carry over twice the load at 6-7000 pounds compared to the Mirage,'s 2800.
The hatch observation Tane has made appears to be addressed by the optional cockpit shelter which blocks spray from underneath. The same solid deck area approach used by the Mirage for the side hatches.

 

Ted Warren was a very good designer of very light, very fast multihulls. His work included a design for a large pod cat for the first global race, a 21 foot proa that was just 2 very small hulls and a tall mainsail only rig, several minimal hull trimarans from about 16 foot to 29 foot, a 31 and a 35 foot trimaran cruisers that had EG 14 lbs cross arms connecting floats to the main hull etc.

We will focus on Teds last attempt to commercialise an ultra light 20 foot racing day sailing trimaran. The UL20 is 20 x 15 foot with a weight of 175 lbs in the race version (carbon fibre every where) or 220 lbs in the “cruising” version. The race version has a 29 foot carbon mast with a 192 square foot mainsail, a 56 square foot jib and a 172 square foot screecher. The cruise version has a 25 foot mast, a 165 square foot mainsail, 48 square foot jib and a 156 square foot screecher. The deep carbon fibre daggerboard provides lateral resistance. The floats have 1000 lbs of buoyancy.

What does all this mean? A starting Bruce Number of 2.0 and with the taller rig and light crew a Bruce number of 2.2-2.3. Any Bruce number of 1.2 or above is fast for a given size. There is a video on the web of the race version of the tri in 11 knots of true wind speed (with occasional gusts) the UL20 is sailing at 16 knots boat speed. That is 40% faster than wind speed. Yes, these tris can perform.

There was only about 15 of these tris produced before Ted realised the tri was not commercially viable. Each UL20 was almost a customised build. Ted also found: “We will make them on special order only, where we will quote the boat depending on configuration. We found that the orders were very custom as it was and it is better to work with the customer on configuration. I also think that the boat is much better with carbon beams and mast, which gets it into a higher price category, and down into the 180 lb range. We have found that the market for this type of sailboat has passed and we would have to spend a significant amount of money in marketing to develop a market for her. She is also more expensive to make than our original estimates.”

The construction of the hulls and decks are carbon fibre foam but the mast and crossbeams could be aluminium or carbon fibre. The heaviest component is the main hull at about 40 lbs. The boat is assembled with four pins to the main hull and four saddle clamps to the floats. Cockpits were optional.

A very interesting boat that was been superseded in about 2012 by the development of higher performance to foiling EG beach cats. Also trying to meet each customers requirements was not financially successful when vanilla production cats could be purchased cheaper.

The jpegs give the idea.

 

Naria MK4 is really a 32' with extra weight, $ and work. They say big lb but skin long. Same $ time etc meander etc bigger inside ...

(wrote this my self. Not grate but better.)

Narai (Mk lV) Self-Build Boat Plans | James Wharram Designs https://www.wharram.com/shop/building-plans/classic-designs/narai-mkiv

Meander 40' performance cruising catamaran by Woods Designs https://web.archive.org/web/20110522013308fw_/http://sailingcatamarans.com/meander.htm

(or Rhea 40 cruiser with central cuddy by Woods Designs https://web.archive.org/web/20110522013153fw_/http://sailingcatamarans.com/rhea.htm)



MEANDER 40' Performance Cruiser

sheet ply or grp flat panel deep V hulls

strip cedar round bilge hulls, ply decks

LENGTH O.A. 12.2m
LENGTH W.L. 11.0m
BEAM OA 6.9m
DISPL (empty) 3.5T
DISPL (loaded) 6T
HEADROOM 1.9m
DRAFT 0.65 - 1.85m
SAIL AREA 70 sq m

Meander Materials List
Hullpanels

84 sq m 12 mm PVC foam e.g. termanto, Divynicell
150 kg 600/150g Linrovmat
85 kg 600/300g Duomat
350 kg polyester resin

Decks, wings, cabin etc.

75 sq m 12 mm PVC foam
150 kg 600/300g duomat
220 kg polyester resin

Keel and bulkhead joints etc.

100 kg 600/300g duomat
50 kg 450g c.s.m.
230 kg polyester resin

Bulkheads 6 sheets 9mm ply, 6 sheets 12mm ply
Keel Panel 2 sheets 12mm
Beam, c'boxes 5 sheets 12mm ply, 2 sheets 15mm ply
Interior 6 sheets 9mm ply, 4 sheets 6mm ply
Platform 7 sheets 9mm ply, 2 sheets 6mm ply (or use foam sandwich, lay up as hull decks)

Timber:
Best quality Douglas fir, Sitkas Spruce, yellow cedar or similar, "planed all round" (PAR).
Beams and beam boxes 2" x 2" 110 m, 3" x 2" 30 m
General framing 2" x 1" 50m approx, 1" x 1" 50m approx (depending on fitout),
Rubbing Strakes 3" x 1" hardwood 26m

Basic layup hull panels

Outer laminate 2 layers 600/150 linrovmat (Ist layer vertical, 2nd layer
horizontal), all joints to be butted, no overlaps, matlayer down first.
Core 12 mm PVC foam (Type 75) or similar.
Inner laminate 1 layer 600/300 g Duomat, mat layer down first.

Keel joint as for the solid glass boat, but extend final csm layer up to the
waterline (not applicable if vacuum bagged panels are used.).
Note: hull panels should be glassed on both sides (and filled and sanded as
appropriate) before offering up to bulkheads. Stringers on hullskin are not
necessary, however, the number of bulkheads should not be reduced and interior
fittings (shelves etc.) should be as the standard boat.

Basic layup decks

I Layer 600/300 Duomat on each side of l2 mm PVC foam. Flat panels should be
glassed, filled and sanded on both sides before offering up to boat, cambered
decks should be glassed on inside only before offering up. Deck stringers and
frames are not required (but temporary supports will be necessary). Insert ply
pads under all deck fittings. All corners should be rounded off to a min. 12 mm
radius and glass joints made as for standard hull/bhd joints.

It is recommended that bulkheads and interior frames and partitions be made in
plywood to save unnecessary finishing.
Beamboxes should be in plywood, as on wood decked boat. Centreboard box can
be foam sandwich, with laminate as for decks. Adjust bulkhead cutouts, knees etc.
for extra box thickness.

 

Well it certainly is a more expensive build Guzzi, best quality Sitka adds up even in the decadent PNW. My point about the Naria is it is a freighter not a performance cruiser. I think James hit his mark for a voyaging canoe which is what he aimed for. Most of the framing could be gotten from home store lumber by picking through for grain and ripping what you need.
Now a performance cruiser will be a easier sell if you want a return on your labor but....
Those Tiki 38s are hovering around $100000 so finding a tribal enthusiast may not be impossible if you want to sell down the road. A cult does have its own built in market.

 

my guess would be, Meander (of course only the ply/V.version) is only slightly more expensive & labour-intensive to build than a Narai MK4, but a significantly better boat.
We (Tangaroa MK I) sailed a bit in company with a Narai MK IV & werde definitely doing better. Freeboard of the Narai is quite high (& we had a much more efficient cutter rig). This Narai rtw-ed later too though, with different owner (Risho Maru - Peter, Alexandra und Finn segeln um die Welt http://www.rishomaru.com/)

 

I recently discovered I'd been working with a fellow multihull sailor for years without knowing. He had built a Pahi 42 in 9 months! and cruised the Pacific for 5 years before selling. He had many positive things to say about that boat, not a speed burner or a slouch but mostly about how it kept him safe. Much of the time he sailed solo.

 

In Australia I would look into demolition timber yards before big box stores, I have seen some exceptionally good beams of Oregon (Douglas Fir) from old warehouses etc

 

Hi. I ran across some comments you made about the catamaran Dreamer, designed by Hugo Myer(s). My husband's uncle was one of the engineers who built the boat and a co owner. His uncle was William Culver and was a PhD student in physics at UCLA. If you can give me any info or boats about Dreamer I'd appreciate it. My husband as a child used to sail from Los Angeles to Catalina many times. His uncle has since passed away but we were very close to him. Any info would be appreciated.

 

I think this is a great idea anywhere, invest in a good saw and planer and you are set.

 

The next (and final) Ted Warren tri I will do is an example of a real performance trimaran. The Warren 27 (this one lengthened to 29 foot) is listed as having no accommodations, as in zero, that is no cockpit or cabin. You sit on a wing net, float or main hull but you will get wet on any sort of windy day. But you will be going fast whilst you are getting wet.

The Warren 27 (or 29) is 29 x 27 foot and weighs 1,100 lbs with a displacement of 1,560 lbs. Yes, the load capacity is 3 crew and not much else. The rotating 44 foot by 1 foot wide wood carbon fibre wing mast (is a 2 part mast for trailing that is joined by bolts for sailing) carries 650 square foot of sail area upwind. A deep central daggerboard provides lateral resistance. If carried, a 6 HP outboard is the maximum power. The floats have 250% buoyancy of the full design displacement and are 28 feet long and have their center of buoyancy forward to develop large amounts of diagonal stability.

This boat sits on a trailer and demounts using a crew of three. Each component is removable with a few nuts and bolts and is placed on the trailer for a width of 8 feet.

As said, there are 3 hulls wing nets and a tall rig. The basic Bruce number is 2.2 but with optional sails can have a Bruce number of 2.5. Translation, a boat speed up to 50% faster than wind speed in the right conditions with good sails and crew. One owner claims this to be a very easy tri to sail and enjoys single handed sailing.

The construction of the majority of the tri is a core of Western red cedar with fiberglass skins on the hulls and carbon fiber skins on the crossbeams and mast all in epoxy. The jpeg boat was mainly professionally built.

This is a very high performance tri that was only superseded by EG Seacart 30 foam glass machine that had very high performance with some cabin space. Ted was ahead of his time and the market place moved on to foilers, some cabin space and cockpit protection.

Sorry about the lack of jpegs.

 

Lydia.
For all. Dreamer and was designed by Hugo Myers with Bruce Ewing and built by these 2 plus 6 engineer friends over 1.5 years of weekend work. Dreamer is 43 x 18.2 foot weighing about 14,000 lbs (original designed to weigh 10,000 lbs). The original mast carried a main and jib of 800 square foot. An 800 square foot genoa was added to the sail area. The length to beam on the hulls is 16 to 1. The draft is 2 foot to 7.2 foot over the daggerboards. The underwing clearance is 1.8 foot. Power is a 50 HP outboard. The reason this cat is significant as is it was one of Hugo Myers first designs, Hugo went on to design Seabird 44 foot ocean racing Transpac winning cat and many other models. Dreamer was the first symmetrical hull cat that was raced against the Choy designed 46 foot Aikane which had asymmetric hulls. Dreamer could outsail Aikane upwind and occasionally beat Aikane around a course. In 1956 Rudy Choy cats were the benchmark but here was a symmetrical hull cat beating them. Dreamer is an important historical cat.

How was dreamer built, with 12 mm plywood and timber. The majority of the shell is 12 mm plywood covered with fiberglass. The hulls are multichine (250 mm wide panels between chines) that were symmetrical side to side and had fine bows and full sterns. The stringers are 38 x 50 mm. The cross beams are 75 x 300 mm hollow box beams placed 6 foot apart in the original build. The current advertising claims the box beams are 100 x 225 mm. The daggerboards are solid Douglas fir.

Attached are a few jpegs of Dreamer when it was for sale a couple of years ago, yes it still exists and is sailing. If you look at the publications page of the Armature Yacht Research Society you may find 2 documents. Number 35 "Catamarans 1960" which has an article on Dreamer. Also the same article appears in the AYRS book "Cruising Catamarans".