Multihull Structure Thoughts

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

  1. oldmulti
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    oldmulti Senior Member

    Part 3 of Russian 19.7 x 10.5 cat.
     

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  2. peterAustralia
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    peterAustralia Senior Member

    I like the first one. I like the fact that it is a fraction beamier than the standard 8.5ft trailering width, making for a more natural beam. I also like the higher cabin forward, allowing the person sleeping there more space. More space also allows the option of having fewer crew and stuffing heaps of junk in those forward berths, the extra height allowing crew to reach over items stowed close bye and access items further forward. Downside is a fraction more windage, and also makes standing of the foredeck problematic as it slopes forward.

    Aside, oldmulti, after two years of this thread, and having read 90 percent of the posts on here, any chance u could identify yourself (optional), sydome of us that are curious could then google ur name and read some past articles you have written

    Aside, a few months ago I was in Ulladulla, two hours south of Sydney, Australia. In the harbour I saw a moored Tiki 21, Two things struck me, firstly how well it was built, and secondly, how absolutley tiny the cabin/berth was. No way you could even sit up and eat a bowl of cereal inside
     
  3. peterAustralia
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    peterAustralia Senior Member

    The first one has a flat deck between the hulls all the way to the bow, versus netting. Obviously in large waves, water would come over the top, adding weight before it drains away, and the underside would pound. The upside is lots of space for lounging around. Thus all makes sense as it is provided it is never sailed in rough conditions, thus more of a weekender, not a blue water boat
     
  4. oldmulti
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    oldmulti Senior Member

    Bernard Kohler is a versatile designer who creates mainly plywood sailing cats and tri’s from 10 to 40 foot. The one we are featuring today is a powered house boat that if powered appropriately is capable of 12 knots. The Eco 6.2 is not an ocean crosser but a canal, river or bay cruiser. The Eco 6.2 houseboat is trailable.

    The Eco 6.2 is 20.3 x 8.2 foot that weights 920 lbs and displaces 2,000 lbs. The engine options can be 2 electric outboards aft and 1 forward and can provide 5 knots with their combined 150 lbs of thrust. Two 100 amp hour batteries will provide a 28 mile range. The next option could be a 20 HP outboard which will power the house boat at 12 knots. The next option is a 20 HP outboard on each transom which will drive the Eco 6.2 at 20 knots. The final option could be a “long tail” surface drive 15 HP air cooled engine on the rear deck with an extended prop shaft. It’s a 12 knot, cheap but noisy option.

    The accommodation is very good for its size. A 6.5 x 4.5 foot double berth forward followed by a 10 by 8 foot main cain containing a galley, dinette, and toilet cabinet. The steering position is forward in the main cabin. Aft is a 4.5 x 8 foot cockpit. A forward cockpit is placed over the forward double berth. Headroom throughout is 6.3 foot except over the double berth. There is 200 litre of water storage.

    The construction is plywood and timber with a light fiberglass cloth layer over the exterior surfaces. There are 5 bulkheads with wooden stringers fore and aft. A hull weights around 105 lbs when finished. The bridge deck is built from 12 mm plywood. All other plywood used is 6 and 4 mm plywood. Laminated together where need. Example: Keel to chine is build up from two layers of 6mm plywood. The cabin sides would be 4 mm plywood. The roof would be 4 mm outside a foam insert and a liner inside for insulation. The cabin sits on the top of the hulls. So, the hulls are basically empty. This would be a relatively easy build and the designer claims it could be built in 800 hours.

    This is a very practicable inshore cruiser that will satisfy even a non-boat person in accommodation for short cruises. Being able to trail it to new locations is a big advantage. A excellent design which has been built. The jpegs give the idea.
     

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  5. YoungGrumpy
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    YoungGrumpy Junior Member

    Did anybody consider modifying the Eco 6 into separated two hulls and a bridgedeck cabin? The hulls could be extended on a simple alum beams for the water, making it more seaworthy?
     
  6. oldmulti
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    oldmulti Senior Member

    Today we will feature the future. The base trimaran is 27 x 19.5 foot and displaces 2,300 lbs. The two L based forward foils and the single rear T foil with attached propeller allow the tri to fly over the sea. The hull and cross beam structures are a carbon fibre PVC foam sandwich. The foils are solid carbon fibre.

    The TU Delft Solar Boat Team initially built the above tri as a solar powered “racer”. The tri has 300 square foot solar array that generates 5.4 KW of power to 20 KW lithium-ion batteries. The 14 HP electric motor feeds to the propeller with 76% efficiency. Result the team said "Due to excellent circumstances, a team that worked very well together and a perfectly functioning boat, we were able to achieve very high speeds and even set a speed record for the boat at a speed of 35 km / h." The 60 km long-distance race that took place on Saturday was a major challenge for the team. “The solar panels were no longer on the deck, so we had to deal with the energy that was already stored in the batteries,” The team won the event by removing the solar panels and just used battery power on race day. For longer distances the solar panels remain attached and provide a lot off additional power.

    The TU Delft Solar Boat Team then for the next year’s Monaco event the team changed the tri and developed a Hydrogen powered option. The tri’s structure had some additional strengthening as this version are capable of higher speeds. Solar panels were removed and replaced by a 250 lbs hydrogen fuel tank strengthen to handle 36 BAR to carry 20 lbs of hydrogen. The hydrogen is combined with oxygen in a fuel cell to provide electrical power for the electric motor.

    At the take-off speed of about 12 knots, they generate enough lift to raise the hull about 15 inches out of the water. This drastically reduces hull resistance and lowers the energy requirements for propulsion. The boat is operated by three pilots and reaches speeds of up to 22 knots. Again it won the 60 km race in Monaco and later created a record for renewable powered boats across the English channel.

    One detail about the build was informative. The mould had Teflon laid in the mould to release the product from the mould. Now, the first prepreg carbon layers could be laid together with the core material and finally the inner carbon layer which then oven cured. After curing in the oven the teflon did not release as easy as hoped. The first of three hulls were released within an hour then the remaining hulls were produced.

    The jpegs give the idea. A video of the Hydrogen powered version is at: https://solarboatteam.nl/en/
     

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  7. oldmulti
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    oldmulti Senior Member

    The America’s Cup has just released the rules for the next series. One boat only, similar to the last series, hopefully using the vessel for the next AC as well and a maximum of 8 crew to reduce costs. OK so far then this requirement was included “As part of the ongoing drive for innovation and new clean technology in the America’s Cup, it is now a mandated obligation of all teams to build and operate two hydrogen powered foiling chase boats for their campaign (subject to proof of concept). It’s hoped showcasing proven hydrogen technology in the marine sector will help create a game-changing pathway for the wider industry and lead to a significant reduction in its carbon footprint. These boats must be a minimum of 10 metres long and the usage and performance criteria is set out in the Protocol”

    So, you save several million by limiting the number of boats per nation and reduce the crew numbers then you include a requirement that will cost several million to build at least 2 hydrogen powered chase boats that have to be at least 10 meters long and travel at 60 knots. The America’s Cup could turn into a renewable power boat race in 10 years.

    Team NZ has already done a design proposal with several companies using the Team NZ chief designer and several local companies. They are seeking sponsors for the chase power boats as they are going to be expensive, I would suggest as expensive as the AC yachts.

    Emirates Team New Zealand CEO Grant Dalton said, “Emirates Team New Zealand continues to be at the forefront of innovation and we intend to really drive the development curve of new and clean technology in the marine industry. It is our hope that we can make a seismic shift into hydrogen power and an emission free statement for the industry. This initiative is not a small undertaking and is not without risk, as we have very specific operating criteria within the team and the America’s Cup.”

    The chase boats proposed are catamarans built from carbon fibre foam sandwich structures with carbon fibre foils. A set of foils for an AC catamaran used to cost $400,000 minimum 7 years ago. The foils on the chase boats look more complex as they have to include electric propeller drives. The hydrogen fuel tanks, fuel cells, electronic controls, batteries, electric motors etc will not be cheap as they are a developing technology. There is hydrogen fuel cell powered cars being manufactured by Toyota and Hyundai that may have technology that’s appropriate which may lower the cost.

    The jpegs give the idea of the proposed boats. The last jpegs give the best idea of part of the complexity. Again if these boats work well, they will redefine the future of boating, but I am not convinced there will be a hydrogen fuel station at every port.
     

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  8. oldmulti
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    oldmulti Senior Member

    The “Albatros” is a Val II trimaran designed by Dick Newick in 1991. Val designs have been featured before but this one caught my interest because of the advertising. According to the ad this tri is a “Construction FG w/poly foam, carbon and Kevlar” and displaces 998 KGs (2235 lbs) with 40.9 square meters (440 square foot) of sail.

    The actual numbers for a Val 11 is 32 x 26.5 foot weighing 3500 lbs fully rigged. The 43 foot wood wing mast carries a sail area that varies between 540 square foot to 800 square foot with genoa etc. The sail length to beam is 11.9 to 1. The minimum draft is 1.3 foot with a draft of 7 foot when the dagger board is down. A 10 HP outboard is the maximum recommended auxiliary power.

    I then chased down jpegs of the build and found the build was wood and ply with a fiberglass covering. The only accurate information I found about the boat in the advertisement was the mast build which was “She comes with a fiberglass coated 43' wing mast made out of BC fir wood and epoxy – such as the boat structure – reinforced with carbon fiber (inside and out), head and foot of mast installed.” The jpegs of the mast are informative as to the amount of work involved in a mast build. The jpegs of the build show the basics of full wing deck Vals. The full wing deck Vals have a lot more accommodation than the mark 1 Vals but are “slower” than Mark 1 Vals. This is a relative term. Any Val is fast if its is not over built or over loaded.

    The accommodation has 2 berths in the main cabin (one on each side on the wing deck with plenty of storage space) plus an optional berth in the bow. The main cabin has a simple galley and limited seating. This boat is aimed at sailing capability first and accommodation second.

    This boat took 16 years to build and appears to be well built. The owner died near its completion, leaving it to his son to organise the final build before it was sold before launching. It is now sailing.

    Please take the warning, the advertised boat may not reflect the actual build. This is the reason you should employ a surveyor if you cannot see the boat for yourself. The jpegs tell the story.
     

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  9. oldmulti
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    oldmulti Senior Member

    Second part of Val 11 mainly featuring the mast, which is strip plank fir with carbon fiber inside and outside. The central spine is timber strips on a plywood web. Additional interior shoots are also included.
     

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  10. Ron Badley
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    Ron Badley New Member


    What a beauty! The float shape is pretty much identical to my White Wings. Some very similar hull construction details in the cross beams too. Both boats designed around the same time I'd guess.
     
  11. oldmulti
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    oldmulti Senior Member

    Ron, if the boat mentioned is the 36 foot Newick ketch rigged White wings can you please tell us how it performs upwind etc. and how good /simple is the roller reefing system with the mast. What is the bearing system supporting the mast to allow the roller reefing? The tri is very attractive and I hope fast on all points.
     
  12. patzefran
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    patzefran patzefran

    Please, what are the length and weight of your White Wings ? Having built a Crowther Twiggy 32 I know it is very easy to overbuild / overweight ! It looks like this Val II is heavy
     
  13. oldmulti
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    oldmulti Senior Member

    Patzefran. Page 56 and 58 on this thread has some detail of White Wings but Ron's input would be much appreciated.
     
  14. patzefran
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    patzefran patzefran

    Thank's, Old Multi. Nice boats ! 5000 Lbs looks right for a performance 36 ft Tri !
    I built / owned a Newick Tremolino MK 4 with 20' outriggers.
    My best flat water performance downwind was near 14 kt. Now I sail a Strike 20 tri (Richard Woods design), 10 / 11 kt to windward and 16 kt downwind (flat water).
    I say flat water, because most people claimed best records corresponds to wave surfing downwind, which (in my opinion !) do not characterize the real performance of the boat.
     

  15. Ron Badley
    Joined: Aug 2020
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    Location: Madeira Park, British Columbia, Canada

    Ron Badley New Member

    The rotation system is quite simple. The is a Derilin cup at the base of the mast captured by an outer stainless cup. The base of the mast is coated in graphite. At the deck there is a plastic needle bearing set up with rings to retain everything. I have the mast out of the boat right now and will get some pictures of the parts later. I was thinking of changing the rig to a regular 3 point stayed arrangement but have changed my mind on that.


    About 10 years ago we were on our way to a multihull sail-in. It was quite windy when we set out, over 20 knots. When the wind freshened even more we decided to turn back as the sail-in was about 25 miles straight up wind. The mast rotation was controlled by an electric motor with a chain ring around the mast. This made it really easy to roll up the sail but wouldn’t hold it in position for reefing. That’s not really an issue as a reef was very seldom required in our light wind area of British Columbia.


    So, we are now sailing downwind under full main and mizzen in probably about 30 knots of wind. Drifter is under control and moving along very well. We were probably doing between 12 and 15 knots. There was a land mass ahead and we needed to jibe. The original sail was the two ply Ljungstrom held together at the clews by a clumsy shackle arrangement. Halfway through the jibe the sail opened up from the clews, we now had nearly double the sail area and my goodness did we take off! My wife isn’t an experienced sailer but even she was aware of things going wrong. I was too busy steering to look at the speedo but we must have been doing well over 20 knots. We stuffed all 3 bows into the back side of a steep wave. I was reaching for the radio because I was sure we were looking at a pitchpole in progress.

    The bow of the main hull is quite flared and the floats are very rounded. The flare saved us, I’m sure. Lots of buoyancy up there. I was able to bring the boat through the jibe after riding over the wave and then rolled up the sail completely. We finished our little trip under mizzen only. I called Dick later and thanked him for his good design sense.


    Once back at the dock I took the main off and ordered a “normal” square top sail with reef points. This was with Dicks permission. Drifter has since been altered to a wishbone boom and the mizzen is gone. There are more modifications but I’ll save those for another day. Overall the boat is a pleasure to sail and very comfortable. It points as high as anything out there but could use more power. Hence the thoughts on changing the rig. I think I’ll just get a bigger main and make a longer wishbone.


    Unfortunately I don’t sail Drifter as much as I should and every now and then I threaten to sell it. Probably never happen. IMG_20190719_145617.jpeg
     
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