Multihull Structure Thoughts

Discussion in 'Multihulls' started by oldmulti, May 27, 2019.

  1. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Today is about another 50 foot cat, the Sunreef 50. The Sunreef line of cats is all about luxury, customisation to suit a client and reasonable sailing ability. The emphasis is on luxury but these cats can sail. The smallest in the sailing range is the Sunreef 50 which is 50 x 30 foot and displaces 71,600 lbs. Yes, you read the figure correctly, nearly 3 times the displacement of yesterday’s Adélaide 50 fast cruising catamaran. In the standard rig the 80 foot fixed aluminium mast carries a 807 square foot mainsail, a 592 square foot genoa. In the “Amber” version, the Sunreef 50 has a carbon mast and boom with a 860 square foot mainsail and a 850 square foot genoa. The length to beam on the hulls is 8 to 1 at best. The draft over the low aspect ratio keels is 3.7 foot. The engines are 2 x 80HP with 1000L / 264 US gallon of fuel and 800L / 211 US gallon water.

    The accommodation is spacious and luxurious. As I said, Sunreef build semi custom cats to suit their clients needs. Result is large practical spaces. In the port hull can be an owner’s cabin and guest double berth cabin with ensuite toilets. In the starboard hull there are 2 guest double berth cabins with ensuites and a single berth crew cabin and attached toilet. There is a 3 cabin version with an owners cabin using all the space in one hull. The main saloon has a large galley with dishwasher, washing machine and fridge freezer. The saloon seating has a dining table, entertainment area and a navigation area that is connected to a forward viewing cockpit thru a door. The aft cockpit also has a fridge and sink with seating and dining table. The aft cockpit is connected to the main saloon thru large glass doors. The flybridge cockpit is where all the sail handling controls lead t and the majority of the helming is done.

    What is the impact of the weight and Amber larger rig? “PAZ”, an “Amber” Sunreef 50, sailed 4,289 mile trip from Ibiza to the Caribbean at an average speed of 6.5 knots, and the maximum Speed Over Ground under sail was 16.3 knots. PAZ ran a Parasail spinnaker for half the trip. As I said this cat is about comfort over outright performance. One tester said “The 50 has been set up for short-handed sailing and with the light wind sails in your sailing locker you should move nicely along in a breeze. With electric winches and furlers and everything working properly, you should be able to handle this boat with one decent deck hand. If you were off on a long voyage though, that high boom height would worry me (problems with reefing lines anyone?), and the exposed helm position is obviously not ideal in 35 knots of wind in a big sea while you are trying to keep a close eye on everyone else on the boat.”

    The construction is composite foam glass. Sunreef build high quality vessels and you will find EG a lot of teak on decks and solid furniture internally.

    The jpegs give the idea. Several of these cats have been built and are very ocean capable. They will provide their owners with a very comfortable trip at a reasonable speed.
     

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  2. oldmulti
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    oldmulti Senior Member

    I am sorry but for this one, but you will have to read the PDF. Pat McGrath (Oldsailor to the multihull threads) used to run Canadian Multihull Services with his wife Jillian before coming to Australia. He was successful in Canada being a product (he “invented” Botecote epoxy, sold good quality timber and plywood etc) and multihull plan reseller for several designers. The PDF contains 50 multihull study plans for Jim Brown, Lock Crowther, Skip Johnson, James Wharram and Norm Cross designs.

    These are early designs mainly (pre about 1980) but give an excellent idea of the state of the art at that stage. Some of the articles are direct copies of sales broachers but there are gems in there. This is the first time I have seen good diagrams of the Seawings 24 and 36 that have been appreciated by a lot of people and you will see a lot of James Wharrams “racing” designs. Yes, you read correctly James was promoting some of his cats as ocean racing machines.

    Good reading. The document is 78 pages long and is 4.7 meg. I have included some jpegs of some of the featured designs.
     

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  3. oldmulti
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    oldmulti Senior Member

    A short one about a Tiki 30 hull build. A Wharram Tiki 30 is 30 x 16.3 foot with a weight of 2,200 lbs and displacement of 4,400 lbs. The 30 foot aluminium or wood round mat carries a 385 square foot wing sail rig. The length to beam is 11 to1 on an even keel and the lee hull can be pressed to 8 to 1 when the windward hull is about to fly. Draft is 2.1 foot. Outboard power of about 10 HP.

    This is not an expensive luxury catamaran, but provides basic comfort for living at sea . A low cost ocean sailboat with a sleeping capacity of 6 people (2 double beds and 2 single beds in the hulls) and spacious deck area. The performance of a Tiki 3o will surprise you. If keep light, these cats can sail very well with 8 knot plus averages and over 15 knot peaks.

    The construction is mainly 6 mm plywood with timber stringers and support framing. Wharram has simplified there cat structures over time and used epoxy and fiberglass tape to substitute for a difficult to shape timber components. The crossbeams are timber ply. You may love or hate Wharram cats looks and sailing ability but there latest build structures are well thought out. The problem a lot of Wharrams have is timber rot or owner builders using poor quality build materials.

    Back to the point of this post. A few jpegs of a build of a Tiki 30 hull. The many paged web site is: TikiRio: março 2012 http://tikirio.blogspot.com/2012/03/

    The components of the hull were made then a 2 day 2 person build created the lower hull and within 4 weeks a hullready for decking was complete. If you are focused and dedicated, a Tiki 30’s can be done in under a year.
     

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  4. oldmulti
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    oldmulti Senior Member

    The INSULA 52 is a development of the Adélaide 50 fast cruising catamaran designed by Vincent Lebailey Naval Architecture. The INSULA 52 is lighter, has a bigger rig and has more aggressive styling. The INSULA 52 is 51.9 x 24.7 foot with a half load displacement of 24,140 lbs. The carbon fibre mast carries 1,540 square foot upwind on a “slutter” rig (half way between a sloop and a cutter). The hull length to beam is about 12 to 1. The draft is 3.6 foot over the low aspect ratio keels. The drivetrains different with 1 x 75 HP diesel, shaft-driven in one hull and a 10 kW electric, shaft-driven in the other hull. I bet the owners hull has the electric motor.

    The single propulsion motor has a secondary electric motor called the “manovering motor”. This small electric motor will ensure the boat’s manovering function when arriving in a port or anchorage. It also allows the boat to navigate in areas where conventional thermal engines are undesirable.

    The INSULA 52′ is intended to be an ocean-going catamaran designed for comfort, performance and ease of maintenance. The accommodation on the INSULRA 52 web site:

    “The INSULA 52′, a 3-cabin version of a sailing catamaran: In its 3-cabin version, the boat is equipped with a large owner’s cabin with a dedicated washroom in one float, and two guest cabins with a shared washroom (and two companionways) on the opposite float. This ergonomic design optimises the volume of the float and the washroom by avoiding narrow volumes and long corridors.

    The INSULA 52′, a 4-cabin version of the travel catamaran: In the 4 cabin version, both floats will be equipped identically. The layout will have 4 companionways, once again, in order to limit the loss of volume in the floats caused by unnecessary long corridors.”

    I am assuming the main deck cabin has a large U shaped galley, seating dining area and a helm station/chart table positioned for the forward view. The outside saloon (read aft cockpit) is protected from the sun by the extended roof, for sun protected socialising.

    The main cabin roof is equipped with 4 fixed and rigid solar panels (4 x 400 W for an optimal output) ensuring electrical autonomy of the boat. The cat does not have a fly-bridge (weight saving) but has two steering stations with tiller bars on dedicated seats, along the side lines. At the end of each float on the aft deck, a technical access hatch is placed, to have easy access to the steering system.

    The mainsheet track is positioned on the aft beam of the boat, one of the strongest points of the vessel structure. The headsail tracks remain on the coachroof and to lead to the winches which are positioned to limit friction and to optimise crew ergonomics.

    This will be a performance cruising catamaran with the numbers indicating 10 knot averages and 20 knot peaks. The structure is unknown but to get down to this weight it would need to be foam biax and triax fabrics, resin infused with carbon strengthening in cross beams etc.

    The jpegs give the idea. I hope this design is built as it conceptually very good.
     

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  5. SolGato
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    SolGato Senior Member


    Thanks for posting this OldMulti.

    Great to read Skip’s musings, and his insight into the backstory of the evolution of Trimarans and the dedication of those who sought to refine the design.

    He and others at the time seem to have been aware that they had been given a bad reputation and felt that the potential was there and could be reached if they stayed focused on honing their craft.

    And interestingly many of the designs highlighted in the PDF seem to have done just that, as a great number were built and sailed in the decades that followed, with many still being sailed today.

    And I too was excited to see the drawings of the Seawings as I had been trying to track them down without any luck.

    Now I have something I can print and frame and hang up on my bulkhead above on of my bed bunks!
     
    Last edited: Oct 2, 2022
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  6. Flotation
    Joined: Jan 2020
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    Flotation Senior Member

    I noticed new videos on your YouTube channel, one about modifications to you solar powered cat:



    And one on a new bigger solar cat project:



    They are some of the most interesting examples of homebuilt solar powered boats. Would you mind starting a dedicated boatdesign.net thread about these?
     
  7. Russell Brown
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    Russell Brown Senior Member

    I think a thread would be a good idea. There are a couple of guys here that are very knowledgable about electric power for boats and they want to build solar powered cats.
    Sol, you have an enviable stable of boats!
     
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  8. cavalier mk2
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    cavalier mk2 Senior Member

    Thanks for posting the catalog from Pat, I enjoyed our correspondence over the years.
     
  9. oldmulti
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    oldmulti Senior Member

    A small contribution about electric boats. The Solinner (also known as the T 21) is 20.4 x 7. 6 foot and weighs 2,200 lbs. The basic electric engine is a Torqeedo 2.0 Cruise RL with two 210Ah AGM (Absorbent Glass Mat) batteries, a high precision charger monitor, solar charger controller and battery charger. Most boats are delivered a delivered with Torqeedo 4.0 Cruise RL (7 HP) with 10 KW batteries. There are four solar panels each with a power output of 285-W each on the cockpit roof. (This was the original design but I think they would be using 500 watt panels now, more power, faster and longer range).

    The speed and duration of the Torqeedo 2.0 Cruise RL and lower spec batteries is 10 km/h with an 8 hour duration. The Torqeedo 4.0 Cruise RL can reach 12 km/h (about 7 knots) with an 18 hour duration on overcast days with bigger panels and batteries..

    The concept of the catamaran is a day boat with a seating capacity of 10 people. This is a bay or river cruiser for a quite (very quite) day out. The design has a door in its side to allow easy access to the te seating etc. There is no indication of any internal accommodation.

    The base structure is fiberglass with Carbon fibre roof support posts. The bimini roof can be folded down to get below bridges etc.

    The jpegs give the idea.
     

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    Last edited: Oct 3, 2022
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  10. Russell Brown
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    Russell Brown Senior Member

    I'm pretty sure I remember Pat from my childhood. I think he was the only outside dealer for Searunner plans.
     
  11. cavalier mk2
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    cavalier mk2 Senior Member

    He'd send me Nicol stuff on occasion and I still have the Raka plans I got at discount.

    Some of the best reading was the book of the 1976 first multihull symposium along with the "Capsize Bugaboo", classics of multihull history. Outrig.org should publish them as they are hard to find.
     
  12. cavalier mk2
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    cavalier mk2 Senior Member

    Of course I have your Dad's books too, he and Jo Anna helped me with a survey once by copying parts of the Brown 41 plans I needed at a discount rate.
     
  13. oldmulti
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    oldmulti Senior Member

    Sunreef produces luxury power and sailing catamarans. The smallest sailing cat is the Sunreef 50 featured recently now we will discuss the mid-range Sunreef MM460 catamaran designed by Malcom McKeon Yacht Design and Sunreef. The Sunreef MM460 cat is 150 x 55 foot with a weight (??) of 1,120,000 lbs (500 tons). Now I have a problem, vessels this size have an old concept of “gross tons” which is based on dimensions not actual weight. Gross tons are used in requirements for safety equipment and build specification standards. Under 500 gross tons allows you can have less safety equipment, fewer watertight bulkheads etc and lower overall build costs. I suspect the real weight of the Sunreef MM460 is below 670,000 lbs (300 tons) loaded. The 182 foot carbon mast carries a 6,000 square foot main and a 5,200 square foot jib. With a code 0 the sail area is 16,400 square foot. The hull length to beam is about 12 to 1. The draft ranges from 9 foot boards up to 22 foot with the centreboards down.

    The accommodation is vast with 4 double berth cabins in each hull with attached toilets. The galley and services are in the “crew” hull (port hull in this case). The main saloon is integrated with the aft cockpit creating a very large entertaining and seating space suitable for 18 people. Forward on the bridge deck is the owners and VIP guest cabin. Forward of the main cabin area is a forward cockpit with its daybeds and Jacuzzi, which is reached via the main corridor. The flybridge is where the main helming and sailing controls are done. This is a push button boat with powered winches etc. If your home is as comfortable as this cat you can probably dream of owning it.

    Sunreef MM460 CAT also carries a 6.2m tender and there's space for additional water toys, scuba dive cylinders and compressor, as well as a wetsuit store. The crew/rescue tender is stowed in the forepeak and there's also space for two jet skis below deck. The Captain, engineer and about 6 crew will be working hard to keep the owners and guests happy.

    The cat is a foam glass/carbon epoxy composite. Malcom McKeon Yacht Design has done other large sailing catamarans including the Black range of cats including the Black cat 30, 35 and 50 meter designs. His largest design is MM751 – 75 meter (246 foot) performance catamaran. He also has done large power boats etc. Cats like this are $1 million plus design fees alone, let alone the need to be a billionaire to afford the actual cat.

    The performance based on the numbers is ridiculous. 15 knots averages under sail or power possible, but the estimated peak speeds of over 25 knots will need to be proven in reality. I don’t know if this design is under contract but I hope someone will build it.

    The jpegs give the idea. The last jpeg is Malcolm McKeon Black cat series.
     

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  14. Pewit
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    Pewit New Member

    While I agree with all the points you made in fact the video shows the rescue from a different boat and not the Weta.

    The Weta sailor was sailing solo and In the full footage of the hoist, you can see the blue hull of the boat he was rescued from and another sailor in the water.

    https://twitter.com/USCGPacificNW/status/1536471490555543552

    This is the boat Team Runaway Redux - Race to Alaska https://r2ak.com/2022-teams-stage-one/team-runaway-redux/

    The Weta sailor was wearing a drysuit and it would be impossible to do the even without one but even then, you are so exposed on a Weta that I just don't think it's suitable because of the windchill (9 deg water, 30 knot gusts) - unless you had a heated suit like divers but how would you recharge the heating over a week long event?
     

  15. Pewit
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    Pewit New Member

    Your data on the Weta is a bit out of date since the design and materials have evolved.

    Firstly original drawings for a prototype were produced by Tim Clissold but 3 years of development meant with input from many leading sailors in NZ, meant the final product was very different.

    Production was switched from China to XSP based in Singapore in 2014 with a new mold which has resulted in a much higher quality product. At the same time the sail supplier was switched to Norths who redesigned them in a more contemporary bi-radial cut as well as developing the 9.3SqM Square-Top mainsail (8.3SqM pinhead original) introduced in 2018 which provides more power in lighter winds but is still useable up to 25 knots. Also the original hex core was replaced by foam core construction of all three hulls. This resulted in a stiffer, lighter structure which weighs the same as the original at 120Kg fully rigged.
    In 2020 the Self-Tacking jib and Twin Tiller Extension kits were introduced which provides improved boat handling, especially for solo sailors, allowing “hands free” tacks and gybes.
    The self-tacking jib track supports are now built into the mold but kits can also be retro-fitted to existing boats.



     
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