Multihull Structure Thoughts

Hey Oldmulti,
A NZ design caught my eye the other day Snowbird by Frank Pelin, turns out he’s quite the prolific designer but has barely rated a mention here. A lot of his hulls are described as a symmetrical Vee and yet use 2 layers of ply so I’m wondering if they have a bit more shape than say a Wharram, I like the look of the Glidetime at 8.4m.
Can anyone advise on their hull section and second hand availability?

 

Redreuben. I will do a piece on Snowbirds in a day or 2. There were several built but a few capsized. Depending on the size of the Pelin cats some had symmetrical hulls others asymmetric.

Red look at: Used Pelin Catamaran Snowbird for Sale | Yachts For Sale | Yachthub https://yachthub.com/list/yachts-for-sale/used/sail-catamarans/pelin-catamaran-snowbird/278025

 

Look what I found.

read the description they made a few mods.
The framing looks nice and light.

 

Good find. I will add a little tomorrow which I suspect you will already know.

 

The Snowbird catamaran was an early design by the Pelin group. The cruisier racer cat was popular in New Zealand with many being built. The Snowbird is 32 x 15.5 foot and was advertised to weigh 2400 lbs but in reality the second hand boats talk about 4000 lbs. I suspect the naked shell may weigh 2,400 lbs but when you include the rig, interior etc you get the larger weights. The fixed aluminium mast is 44 foot with a fractional rig of 482 square foot. The length to beam on the hulls is about 10 to 1. The hull is a shallow single chine V. The basic draft is 1 foot but several owners have put in daggerboards drawing EG 5 foot. The underwing clearance of 1.5 foot. Engines range from inboards to 10 to 20 HP outboards.

The accommodation is 4 single berths in the hulls with a galley in one hull and toilet in the other hull. The main cabin contains a dinette that can convert to a double bed. The headroom in the hulls is 6 foot and 4.5 foot in the main saloon. Each builder had their own variation but there are several owners who have added a full headroom section in the main cabin. The issue here is this cat was designed to be light and is lightly built, it was not conceived to be a full headroom cruiser with freezers etc.

The original advertising said. “Although designed as a family cruiser the Snowbird has proved a winner in many N.Z. multihull races. With a sail area of 482 sq.ft speeds of up to 15 knots reaching are easily obtained and 7 or 8 knots on the wind are quite common.” I can accept the numbers but New Zealanders are born racers and there have been a few Snowbirds capsize. This is not a problem with the basic design, its just that with a 44 foot mast and a serious racer at the helm things can happen.

The construction is described as: “The Snowbird is constructed from sheet plywood and the latest techniques of hull construction are used with various areas being reinforced with fibreglass chopped strand mat and fibreglassing resin to ensure a strong watertight hull which is easily constructed by the amateur. This craft also lends itself to foam sandwich and end grain balsa construction.” The video Redrueben found gives a clear idea of the plywood build version. The fact that CSM is included in the original build gives an idea of the age of the design.

Next Pelin, later, designed several other cats: Glide Time 28 foot weight 3,570 lbs and 8 and 6 mm ply, Landfall 34 foot weight 6,080 lbs 9 mm and 6 mm ply, Trade Wind 36 foot weighing 7,000 lbs 9 mm and 6 mm ply. As you can see the earlier designed Snowbird is a lightly built design.

The attached jpegs will give an idea of the design.

 

Frank Pelin was one of those jack of all trade designers, like Richard Hartley, who designed ranges of different types of boats in different materials. The plans are still available.
The Snowbird was a popular design in NZ and quite a few were built. As OM says a number went over. There were two rigs IIRC one had a 13.5 and the other 11.5 metre masts. I got to know a bit more about this design when some friends bought one a few years back. Its a very 60s /70s style boat in the vein of the Iroquois and boats of that type. Quite a lot of room in the cockpit and the low (4'6") bridgedeck main cabin. They can sail quite well, especially with the big rig and kept light. The hulls have quite low freeboard - the toilet, under the foredeck in one hull is accessed through a crawlthrough on my friends old boat. The bunks are crawl-ins. I think the worst thing is the low (1'6") bridgedeck clearance at the back of the cockpit which will pound going to weather. Plenty of similar size boats today tend to have higher freeboard, BD clearance, more space in the hulls and B/deck and still perform well. Good boat for its time though.

 

The following high performance cruising catamaran is the stuff of dreams. It was designed by VPLP with characteristics of a racer but with very spacious accommodation. The Moxie 61 (yes, homage to Weld Newick Moxie racer) is 62.2 x 31.5 foot weighing 35,600 lbs. The 78 foot rotating carbon fibre wing mast is 130 square foot and carries a 1,290 square foot mainsail, a 860 square foot number 1, 430 square foot number 2, 1,880 square foot gennaker and a 2,960 square foot spinnaker. The main and jibs are all Cuben Fiber racing style sails, high aspect ratio, square top with PBO rigging. The mast is placed aft of centre to allow the cat to be driven harder in reaching and downwind conditions. The draft ranges from 4 foot to 9 foot over the daggerboards. Engine power 2 x 50 hp.

The accommodation has 4 elegant en-suite cabins (1 master and 3 guest cabins) are designed for comfort and privacy, with plenty of space for clothing and personal items. Portholes bring light and fresh air into the cabins, creating an inviting retreat by day. Original artwork in each cabin adds that extra personal touch. There are also crew cabins. There is a very large galley. The main saloon is very large, with large Bose entertainment systems (also throughout the vessel) and seating available which is integrated with the cockpit. There are well-protected aft helm stations either side of the large cockpit.

Complete independent navigation systems based around the Furuno radar system suite, and a separate Inmarsat C package is backed up with an always-on satellite connection feeding weather information to independent processors, screens, and a navigation package. Moxie is never “in the dark,” even under the most adverse conditions. All digital power and media systems, and a green design throughout mean minimal energy needs, met mostly by passive, six jumbo solar panels are flush-mounted on the coach roof. Engine-integrated generators, a redundant independent navigation system for added safety.

the MOXIE 61 is fully built in carbon foam epoxy from bottom of the dagger boards to top of the mast. The mast located aft for better weight distribution will be rotating with a Kevlar rig. The structural concept I like is the full width full depth 6.5 foot bulkheads across the cat which provides very good internal room, a strong structure and a great end plate to sails. The view from the steering cockpits also is excellent.

There are no performance numbers but this is a 25 knot peak speed type of cat with 300 to 400 mile day potential. In short travelling at wind speed up to about 15 knots in the right conditions. Only one problem, Moxie 61 second hand is selling for $US 1.8 million, so much for dreams.

The jpegs give the idea. How a good cruising cat should be designed. Pity they cannot do the same concept in a smaller package without it looking out of proportion.

 

The following is an aluminium charter power cat designed by Sea Speed (Australian kit boat company). The Sea Speed 12.1 is 40.3 x 14.3 foot with a displacement of 22,400 lbs. The draft is 1.8 foot. The power is 4 X Suzuki 250 4 stroke 250 HP (@ 6000 RPM) outboards. Maximum speed is 40 KNOTS LIGHT, 38 KNOTS LOADED with up to 40 passengers. The cruising speed is 28-30 KNOTS.

The reason for this item is the fuel “economy”. Fuel consumption is 170LTR/HR @ 20 KNOTS (38 gallons/hr) and at cruise speed 240LTR/HR @ 28 KNOTS (54.5 gallons/hour). In Australia at cruising speed you are spending $A 576/hour, in the US you are spending $US 218/hour ($A 320 Australian). At full power/full speed you are 344LTR/HR @ 40 KNOTS or $A 825/hour of fuel. The cat has 6 x 200 litre fuel tanks for an effective range of 315 miles at about 20 knots. You better have a successful business running to pay that sort of money in fuel costs alone let alone any other running costs of crew, maintenance and depreciation. There is an attached jpeg of the fuel consumption of this cat over a speed range.

This cat is designed by experienced people and the fuel numbers don’t surprise me. In a commercial operation the fuel consumption makes sense but for a private individual inboard diesel engines would make more sense. You may have a lower top speed but you could halve your fuel costs using diesel engines over the outboards.

Back to the Sea Speed 12.1, basically all aluminium construction. Cats like this typically have 4.5 or 6 mm bottom plate, 4.5 mm side plates, frames every 2 foot or less and stringers every 1 to 1.3 foot. Often commercial charter builds have slightly heavier construction that pleasure boats due to government regulations.

The power cat is a charter vessel set up to do day trips in coastal water operations. The seating is configured in a back to back arrangement with lightweight honeycomb tables between them allowing for dining in comfort during rough trips. The deck layout also has a small galley forward and large central table midships aft. The aft' deck has a fold down platform which can be used for both beach landing and as a snorkelling/dive platform at sea. The platform is attached to a fixed platform which extends out past the outboards. This is complemented by three fresh water shower units, one overhead plus one recessed units each side. Beside the platform is an aft' toilet compartment which is full size. On board white goods include flat screen T.V.s with live streaming GPS navigation and DVD entertainment plus stereo sound system and Bosh speakers. Also a 4 stage CCTV system for safety and security reasons.

The jpegs give an idea of the cat.

 

This is a very short one because I do not know much detail and would like to know more. Ron Givens designed the 14 foot Paper Tiger catamaran in the 1960’s. In the early 1970’s he designed the Paper Tiger Cub as an introductory cat for young people. The Cub is 10 x 5 foot, the weight is unknown. The mast size and sail area is unknown. The hull beam is 1.2 foot. The hull length to beam is about 8.5 to 1. The hulls are single chine shallow V shaped. There are hull based daggerboards and kickup rudders.

I suspect this is a 14 foot Paper Tiger basically shorten to 10 foot. The construction is ply timber again and would use either 3 or 4 mm ply on the hulls. The cross beams are 52 x 52 mm aluminum box sections. The mast beam is so short it does not require a dolphin striker.

The 14 foot Paper Tiger is either foam glass or 4 mm ply. But one NZ guy decided to build a light version, he used 2 mm aircraft ply with a light carbon fibre skin. No reports on longevity.

There are only 2 jpegs. The only person who reported sailing a Paper Tiger Cub, sailed it when he was 16 and had a lot of fun and found it easy to sail. Any further information would be appreciated.

 

As another variation on the PT theme, there was also the Tiger Shark 5.5 twin trapese job. A few built over here (NZ).

 

Global Marine Designs from Australia do designs and kits for aluminum power cats and other designs. The cat we will focus on is “Spirit of Turmarr” a UK windfarm support vessel of 39.3 x 14.9 foot over the hull and a total length of 44.1 foot over the rear platform covering the jet drives. The weight is 34,400 lbs with a displacement of 44,400 lbs. The length to beam on the hulls is 10 to1. The underwing clearance is 3 foot. The power is 2 x Iveco C90 550 hp inboard engines with a total power of 1,100 hp driving “Rolls-Royce” Kamewa waterjets through ZF305 gearboxes.

The fuel capacity is 2 x 1200 Liters which at the vessel’s maximum speed of 25 knots, the vessel has a range of 190 nautical miles. When cruising at 21 knots, this range extends to 225 nautical miles.

The accommodation is set up for wind farm work transporting workers and some equipment, but is quite spacious and could be converted into a nice cruising accommodation.

The build is basically aluminum with bottom plates 5 mm, side plates 4 mm, the main deck (underwing) plates 5 mm, foredeck plates 4 mm and the superstructure plating 4 mm with a 4 mm roof. The nominal frame spacing 700 mm (2′ 4″) and there are longitudinal stringers throughout.

Vessels like this are designed to work in all weathers and are solid vessels. They are very capable cats providing a relatively comfortable and safe ride in difficult conditions. The engines are large to handle those tough conditions.

The jpegs give the idea.

 

I've seen a few snowbirds come up for sale over the years. They didn't appeal so I never looked into them much. I can't remember for sure but I THINK at least 1 or 2 were in aus.

 

One on Yachthub right now.
Used Pelin Catamaran Snowbird for Sale | Yachts For Sale | Yachthub https://yachthub.com/list/yachts-for-sale/used/sail-catamarans/pelin-catamaran-snowbird/278025

 

“Marie-Pierre” is the second Global Marine Design that has a hull length of 39.5 foot but has a different shaped hull form to suit its requirements of a dive charter cats. The “Marie-Pierre” is 39.5 x 14.7 foot over the hull with an overlength of 41.1 foot over the rear ramps covering the jet drives. The weight is 26,200 lbs and the displacement is 30,250 lbs. The length t beam is 8 to 1 on the slightly asymmetric V hulls. The draft is 2.2 foot at full displacement. The underwing clearance is 2.7 foot. The power is 2 x C9 Cats of 575hp @ 2500 rpm through Twin Disc MG 5082 SC gear boxes and Hamilton 322 Jets. The top speed is 34 knots. The cruise speed is 24 knots. The 2 x 900 liters fuel tanks provide a 300 nautical mile range at cruising speed.

“Marie-Pierre” is 14,000 lbs lighter in displacement than the “Spirit of Turmarr” above and as a result can travel 9 knots faster at peak speed with a 3 knots faster cruise speed. Using virtually the same engine power and drive technology “Marie-Pierre” uses 25% less fuel and has a 30% longer range at a faster cruise speed. Well designed light displacement cats save you money over the life of the boat.

The accommodation matches its function of a charter dive cat with a small galley, dinette, navigation and helming area. Also there is a large toilet on the bridge deck. The cockpit is large for people to prepare for diving tours. This design could be converted to a cruiser if required.

The build is basically aluminum with bottom plates 6 mm, side plates 4 mm, the main deck (underwing) plates 5 mm, foredeck plates 4 mm and the superstructure plating 4 mm with a 4 mm roof. The nominal frame spacing 700 mm (2′ 4″) and there are longitudinal stringers throughout.

The jpegs give the idea.

 

The Sunpower 44 is a cruising catamaran designed to run on electric power. Depending on the solar, battery, engine option chosen can run purely on solar at slower speeds or have higher performance with a supporting generator. The Sunpower 44 is 44 x 23.6 foot with a weight of 24,600 lbs. The hull length to beam is about 9 to 1. The draft is 2.5 foot.

The motive power depends on which “engine” package you choose. The start system is a 48 volt propulsion system with 25kw motors and a 30kw battery pack with a solar power 2kw sun charge. The next is a 96 volt propulsion system with 30kw motors and 30kw battery pack with solar power 4kw sun charge. The higher power system is 144 volt propulsion system with 50kw motors and 70kw battery pack with solar power of 1.6kw to 9.6kw sun charge. The final option is a 400 volt propulsion system with 135kw e-motors and a 140kw battery pack with solar power 1.6kw – 9.6kw sun charge. All options have a supporting generator ranging from 22 kW to 100 kW. As the engine power rises the cost rises. Running a 400 volt system compared to a 48 volt system requires different wiring, inverters, power controller arrays etc throughout the vessel.

The cruising speed of the basic system using solar alone is 4 to 6 knots all day long depending on conditions. If you are using the supporting generator with larger engines etc you can cruise up to 10 knots. The peak speed is 15 knots. The generator has a 250 to 500 litres of fuel available. At anchor the Sunpower 44 can be completely solar powered for days at a time. In one of the jpegs you will see a full size 2 door house fridge which can be supported by this level of solar.

The accommodation is comfortable with 4 double berth cabins, a really large bathroom and another toilet area. The salon has the galley, inside helm navigation area, seating with an attached cockpit area available through large doors. The fly bridge is very comfortable with a solar array roof providing shelter.

This type of power cruising cat is the future of boating. The advances in EV car batteries and electric motors helps develop the technology for boating. Porsche Taycan run 800 volt architectures, Tesla are just starting to use cheaper larger batteries, now that lithium iron batteries have come of patent. 700 watt solar panels are now in production (400 watt was standard 2 years ago). We will see some of this technology be included in cruising boats allowing higher cruising speeds and less need for generators.

The cat is built in foam glass and “has custom made foam core e-glass that is 30 percent lighter than other yachts internal bulkheads and stringers yet is also stronger and engineered to the highest level. Yes, it is more expensive to make but our team focus on custom quality builds.”

The jpegs give the idea.