Multihull Structure Thoughts

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

  1. Mark.V
    Joined: Feb 2021
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    Mark.V New Member

    Bajan...you are correct.. Item two in your list, as Oldmulti guessed, is the boat I am looking at. I'mNot a multi...$$$ millioner for item 1.

    And yes, it does seem to have a lot of equipment/options which I had not considered probably add weight and hmm appeal. I am also concerned about excessive heat from the many windows. And Multi ~! I thought I was the only one that spotted the 100hp engines mislabeled. :). ... Any thoughts on how I might make this boat work with all the equip plus loaded for cruising for two? ...short of making the hulls deeper or cutting off the hull protrusions :)

    For that matter, any suggestions on boats to look for in similar price range for cruising though mostly parking.?

    I am experiencing some sad maturing @56 and (I think I might not) have the same desire to tweak max speed out all the time. So, as a more lethargic lump, I am becoming more prone to ... dare I say: Lagoon 440, FP Orana 44, (Nautitech 44, but seems to have similar bridge berth protrusion height concerns on the older ~2005-7ish models in my $ range). I do like something about the design/engineering/construction/fully loaded equip. of the old Manta 42, but saloon area seems too claustrophobic...think its due to being a retweaked design of their original 36 or 38.
    a
    I do really like the nav station area on that Crowther 47 though... and the big engines, 300gal fuel, big frig, ac, gen, multiple sails, electronics, speed sailing and motoring potential, etc.... The one lower bunk that I would prefer does seem pretty narrow for two (do you know how wide?), I did notice the protrusion bridge clearance concern, though I did not consider it already heavily loaded as people, supplies, and provisions where still absent! Your insight is excellent! thank you!

    At least I am short at only 5' 8" and there will normally only be two on board, but I am very inclined to many toys, goodies., stores, and supplies.
    [I am still kicking myself for missing out on a 2006 Lagoon 440 owner in good condition, loaded, for $200k]....

    A recent post lists a 97 Voyage 47 with 27' beam? (jerking?) thoughts?
    1997 Voyage Yachts Voyage 47 Catamaran for sale - YachtWorld https://www.yachtworld.com/boats/1997/voyage-yachts-voyage-47-3784365/

    Greatly appreciate all the help and insight! Timber Fittings????

    I am stressing about moving into a waterborne home with the considerations that come with that situation.
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    That Voyage Yachts 47' cat does look very nice indeed.
    I have seen a couple of Voyage cats here, and they also have the same very basic and simple, yet comfortable theme.

    I had a look on Yachtworld for sailing cats in the USA under $200k, and 45' - 50' in length - and not a lot came up.
    The above mentioned Voyage 47 is there, along with this Shuttleworth 45' in the link below, and another Voyage 47 - and that was it.
    1988 Custom Shuttleworth 45 Sail New and Used Boats for Sale - https://www.yachtworld.co.uk/boats/1988/custom-shuttleworth-45-3655387/

    However I do not think that the Shuttleworth would be too happy if you load her up with many goodies, toys, stores and supplies.

    Here is the Mayotte (Voyage) 47 - but her sale is pending -
    1995 Mayotte 47 Sail New and Used Boats for Sale - www.yachtworld.co.uk https://www.yachtworld.co.uk/boats/1995/mayotte-47-3726641/
     
  3. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Mark.V. You want comfort and reasonable performance. Lagoons, Pajots etc are aimed at that market. Crowthers are reasonable comfort and performance oriented. My other comment is the smaller the better. EG a 40 foot Lagoon is an easier boat to live with over a long term due to lower maintenance and operating costs as well as being physically easier to sail, especially if you don't have electric winches. A 33 footer takes half the effort of a 38 footer which is half the effort of a 45 footer to sail, especially if you have a problem in a seaway. Its the usual problem as you get older the bigger the boat you can afford, the less able you are to sail the boat, unless you carry crew or have a degree in electrical engineering.
     
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  4. goodwilltoall
    Joined: Jul 2010
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    goodwilltoall Senior Member

    Larger cats would require simplified systems deducing from their original intent as built which would then effect its overall value. If having or desiring a 40' cat where 98% are usually valued at around 200k they would be hard pressed to rework systems which can and would make a better voyaging boat but at same time destroy some of the boats existing monetary value.

    As posters have shown, finding cats under that price in the 40' range which are good candidates for reworking overly complicated systems is difficult.

    Reason for bringing this up is one idea i have which is contrary to ol multis way of thinking in the examples of the 33', 38', and 45' boats in his previous post (which btw is well reasoned).

    Yes, the smaller boat is easier to handle "proportionately" but, if overall SA is reduced on the bigger boat, they would still maintain speeds greater or at the least just as fast as the smaller boats during typical winds and similarly during times of higher winds when sail area is cut back while still maintaining a safer attitude. These characteristics can be gained up to the point of making the sails just as manageable as on the 33'.

    This change would take away from the larger cats "optimal" performance potential. Making the sails initially smaller but at the same time gaining simplicity doing away w big expensive winches n sails n rigging etc... creating a snowballing effect in the opposite direction of complexity, instead towards simplification, lesser costs, greater safety, and easy manageable operation

    In a ocean going catamaran the above characteristics are a requirement for long term "safe" voyaging. Technology has improved certain aspects but unrestrained reliance on it has been a detriment. Just as certainly as a carefree sedentary life makes you a weaker man so it is the same applied to a boat, meaning both need an active mind and body tending matters for well being.
     
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  5. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    A tacking outrigger “O Tahiti Nui Freedom” is 50 x 20 foot over hulls, 26 foot overall beam including the outrigger beams to support the mast cap shrouds. Weight is claimed to be 15,000 lbs but another site says 18,000 lbs. This Tacking outrigger is relatively light for its length. The mast is 36 foot high and carries a gaff rig with 765 square foot of sail. The length to beam on the main hull is 10 to 1 and on the 48 foot long float is 18 to 1. The rudder is an underslung spade with a stainless steel shaft.

    Why is this boat of interest? Because it did a successful 115 day voyage of 9500 miles from Polynesia to China and subsequently did a return trip visiting many countries. Also, the build was fast. The build started in 25 March 2010 and was launched 1 July 2010. On 27 July 2010 it started its 115 day voyage. Maybe tacking outriggers are very ocean capable if well designed. Did I mention that the original design of this craft was based on drawings done Admiral Paris in 1820. The design was then reviewed and modernized by NG Yacht Design in order to meet the standards of modern safety while respecting the line and form of Paris' 1820 plan. This modified design was then sent to all of the intended ports of call to assure compliance with local standards.

    The hull structure is plywood on timber stringers encapsulated in epoxy. The cross arms are 25 foot long and weigh 670 lbs each, they have up to 20 laminations of timber (with biaxial e glass epoxy between each layer) on the main hull ends and 11 laminations at the float end to form solid timber (with some glass and epoxy) cross arms. The maximum cross section of the cross arms are approximately 250 x 250 mm. The cabin roof is strip plank cedar and glass with timber framing. The decks and cockpit are plywood with a glass layer.

    The boat averages 3 knots light winds, 6/8 knot averages in moderate conditions but can do 9/10 knot averages in 25 knots of wind. The proa peak speeds were higher and it could go faster if pushed, but the crew wanted to be safe and the voyages intent was to highlight the Polynesian capability of ocean travel, it was not about record setting.

    Tacking proa’s have only one issue. You have an unbalanced stability curve. That means if you are fully powered up on one tack and then go to the other tack you may have to reduce sail or capsize. The float buoyancy on one tack needs to be 100% of the weight of the float to have a balanced stability curve. But if the floats buoyancy is 100% of the float weight there is no reserve buoyancy. Result the float has to have more buoyancy, therefore more stability on one tack than the other tack. Skilled sailors have no problem with this especially with lager sized tacking proa’s.

    The jpegs give the idea. The following web address will lead you to build “video’s” which are a series of slides about the boats build. tacking-outrigger.com nui freedom http://www.tackingoutrigger.com/nui_freedom.html
     

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  6. garydierking
    Joined: Sep 2004
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    garydierking Senior Member

    Small tacking outriggers can easily provide righting moment on either tack by having hiking seats on both sides within reach of the rudder for easy single handing.
    [​IMG]
     
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  7. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    AMF built the Hilu in the 70's, and she is very similar in concept to the outrigger in Gary's photo above.
    AMF Hilu advertisement.jpg
     
  8. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Yesterday we spoke of a 50 foot tacking outrigger “O Tahiti Nui Freedom”. Today we speak of her smaller sister the 29.75 foot tacking proa, the Va’amota 30, that was built for an educational/scientific observation project and eco-tourism for the local island population to exploit. This boat is also being partially discussed on Raidboat Pacific Proa thread.

    The tacking outrigger is 29.75 x 11.65 foot over hull gunnels and 15.15 foot wide including beam outriggers. The boat weighs 2080 lbs with a displacement of 3300 lbs. The 29 foot high mast carries a gaff rig mainsail of 312 square foot, 160 square foot genoa, a 65 square foot jib and a 365 code 0. The main hull length to beam is about 10 to 1. The float length to beam is 27 to 1. There is a retractable lee board on the main hull that draws 5 foot, with a stern mounted kickup rudder. The numbers indicate in the right conditions this boat could be fast. I have no knowledge of its performance though.

    Again, the design was done by NG Yacht Design. The structure of the boat is plywood and timber encapsulated in epoxy with a fiberglass cloth covering the structure. The boat has timber frames and stringers. The decks and cabin are plywood. The crossbeams are not solid timber but have a laminated timber top and bottom flanges with small bulkheads between. The timber beams have 3 dimensional curves in them to accommodate the rigging requirements. The cross beams are tied on to emulate the ancient Polynesian practice of tying proas together.

    The float size and shape indicates that this proa only has about 1200 lbs of buoyancy in it and the structure indicates it would only weigh about 500 lbs at best. This means, as Gary Dierking has indicated, it would require human ballast on the float to have a balanced side to side stability curve. The reason larger tacking outriggers are easier to sail is stability increases with size a lot faster than overturning moment of the sails. In short, the bigger the boat is, the safer it is, if a tacking outrigger keeps the same basic length to overall beam ratio.

    The jpegs indicate this tacking proa would be a lot of fun to sail and camp cruise on. I also suspect it would be a cheap fast boat to build except for the cross beams. The Tackingoutrigger.com site mentioned yesterday has many variations of tacking outriggers if you are inspired.
     

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  9. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    The Robinson 5000 (or 16) was designed by Dibley Yacht Design for a repeat client, John Robinson, commissioned us to design a new beach trimaran. The tri is 16.5 x 9.9 foot capable of folding to 3.6 foot for trailing. The weight is 165 lbs with a designed displacement of 345 lbs. The 24.5 foot fixed carbon mast carries (in its Mark 1 version) a 143 square foot mainsail. The main hull length to beam ratio is about 11.5 to 1 and the float length to beam is 14 to 1. The deep daggerboards and kickup rudders are on the floats. A later Mark 2 version has the mast moved slightly aft, a larger square top main and headsail added for more performance. The Mark 2 version also was to include larger float volumes to handle the larger rig.

    The original owner wanted a fast, fun, easily rigged trimaran with the outer hulls (Ama’s) to hinge back towards the mainhull (Vaka) so he can trailer his Tri back home. The Robinson 5000 is easily rigged and sailed by one person. All controls are within reach of the helmsman and the rudders effortlessly flip up when coming into the beach. The Ama’s have enough buoyancy to lift the main hull out of the water.

    The hulls are foam glass. The cross beams are carbon fibre. The carbon fibre spar and other carbon fittings were built by Alex Valling, of C-Tech in Auckland. The carbon fibre cross arms are 'oval carbon tubes' slots into 'half oval carbon tube' and then 50 mm (2") Velcro straps wrap around to keep it all together. Simple and yet really holds the ama's in place with very little movement. This spreads the load nicely compared to putting a pin in to join the beam to it resting place. A pin creates a hole and potential weakness. The build team are also looking at using a 3D Carbon Printer to make some of the smaller items as they have orders for 6 additional vessels.

    Dibley says “She sails like a dream and tacks very well. Careful thought was put into Ama positioning in relation the main hull, and of course the centre of effort of the sail to get her to tack like she does. Brief from client was to keep it simple and easy to rig by one person. Apparent angles shoot forward quite fast so no requirement for downwind sails for this model.” Dibley Marine Design said on the first sail with a performance of 5 knots True Wind Speed resulted in 8 knots plus boat speed.

    An interesting design as the jpegs show. The last jpeg shows the faster Mark 2 verson.
     

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  10. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Sodebo, a 31 meter carbon fiber offshore racing trimaran that is capable of 40 knots collided with a cargo ship in the English Channel in 2014, less than 24 hours from departing on the solo trans-Atlantic yacht race La Route du Rhum. The 2014 Sodebo is 102 x 69 foot with a 115 foot mast carrying 4,700 square foot of sail upwind and 7,100 square foot of sail downwind (yes, a 2650 square foot main and a gennaker or spinnaker can drive you at 40 knots).

    Why the interest? The closing speed between the vessels was about 40 knots. The trimaran was sailing under 3 reefs and was progressing at a speed of 20/25 knots in gusty winds with 30 knots of wind from the SW. The tri was doing 25 knots when it hit the ship on its aft quarter as the ship was motoring at 18 knots. The damage was significant, but surprisingly it wasn’t altogether catastrophic. Sodebo’s central hull bow was torn off and the starboard float was heavily damaged back to the forward cross beam, yet the mast remained upright and skipper Thomas Coville nursed Sodebo as he was heading towards the port of Roscoff, reaching under reduced sail, sailing on the port hull. Coville was making 12kts and as he approached the Brittany coast.

    Coville notes he had gone inside his boat to investigate an engine alarm and noticed he had two merchant vessels on his screen. Sodebo Ultim was sailing on autopilot at the time which was keeping a constant true wind angle on his sails, but not necessarily a constant course. He notes that with the closing speed of 40 knots, he closed the distance in 1 minute 30 and before he knew it, he smacked the side of the ship near its aft quarter.

    Several things, things can happen fast when you have closing speeds approaching 40 knots. That is 4000 feet every minute, in short Colville was over a mile from the ship when he went below and in 90 seconds he hit the ship. Second for a tri that hit the ship hard there is damage but the tri was still able to sail at 12 knots back to the coast. This is a safety factor that is not known to many monohulls. Third controlling 5000 square foot of sail on 40 knot boats is not the real issue, its watch keeping that is important. In an ocean increasingly littered by ships, fishing vessels, 1500 lost cargo containers per year and other items like bouys, ice bergs, logs etc it is only a matter of time before you hit something. Forward facing radar etc helps but human eyes are often better.

    Jpegs give the idea of the damage and the tri.
     

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  11. oldmulti
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    oldmulti Senior Member

    The proa featured here is an Atlantic proa designed in 2003 by Clara Brander. The proa is 67 x 42 foot with a weight of 14,500 lbs and a displacement of 16,700 lbs. The 73 foot high mast carries a 670 square foot main, a genoa of 1100 square foot and a variety of jibs down to 80 square foot. The length to beam on the main hull is 14.3 to 1 the float length to beam is 23 to 1. A deep daggerboard is in the float, with high aspect spade rudders interconnected fore and aft on the main hull. All of these numbers indicate this proa will be fast but being an Atlantic proa it will suffer the issue of having a lot more stability on one tack. If the proa is caught aback with the wind from the wrong direction some very quick action will be required to minimise capsize risk.

    The proa is designed to be built from strip planks materials. Minimal framing is in the hulls but where strength is required full size bulkheads are included. Notice the angle of the crash bulkheads in the “bows” of the main hull, a wise approach. The 2 full bulkheads in the centre of the main hull are required because of the mast caps and shrouds supporting the mast. The cross beam bulkheads and structure are self-explanatory.

    This proa could be used as a fast cruiser if required as it has enough accommodation space for 4 people but I suspect its more a racer cruiser than a fast cruiser.

    The jpegs give the idea. I do not know if this proa was built.
     

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  12. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    The NG designed Catathai 50 performance bridge deck cruising catamaran is 50 x 27 foot and has a weight of 17,900 lbs as a shell from the yard. When loaded for cruising the designer claims a displacement of 23,000 lbs but a second hand version had a displacement approaching 30,000 lbs. An indication of what is loaded on the cat was EG a fast fill dive tank compressor, Lithium house batteries, large freezers, twin 53hp Yanmar engines, a large Fischer Panda 15000 generator, 760W of solar panels, Siam Cooling air conditioning system, hot water system, electric flushing loos and an Echotec water maker capable of producing 110 litres per hour, two 350 litres of water tanks, 90 litres of waste water and two 270 litres fuel tanks. The full tanks of liquids alone would weigh 2900 lbs.

    The 60 foot fixed aluminium mast carries a mainsail of 915 square foot, a self-tacking furling jib of 430 square foot, a gennaker of 1185 square foot and a spinnaker of 1935 square foot. I suspect we are talking electric winches and several crew with a rig this size. I can put a 1000 square foot spinnaker up by myself but pulling down, undamaged, singlehanded a 1000 square foot spinnaker requires either very good timing or luck even with spinnaker socks etc.

    The daggerboards are a little unusual being “in hull” lee boards. The bottom of the daggerboards drop from a chine step above the waterline. Good for keeping the daggercase slot clean but it would have a slight performance down side. The fixed spade rudders draw 3 foot. the hull length to beam and underwing clearance is unknown.

    The build structure of the boat is polyester PVC foam glass or epoxy strip plank cedar. The build jpegs are of the lower hull mould for the foam glass version. NG Design work in many materials for their designs from chine plywood, strip plank, foam glass to aluminium. There is a 45 foot cat that you can have any of these material options.

    The numbers indicate this cat will sail well and as you can see from the jpegs it is sitting with its chines well clear of the water. An interesting performance cruising cat.
     

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  13. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Today we will talk about a 25 x 14 foot day sailing catamaran. This cat displaces about 2000 lbs and carries a cloud of sail in its gaff rig on a 18 foot solid wood mast. The mast, booms and prodder are 130 mm diameter solid timber some of them tapered. The front prodder is 16.75 foot carrying an 18 foot jib boom. The jib is 128 square foot and the mainsail is about 270 square foot with the sails being made from canvas. The rigging is 9.5 mm wire rope. The draft is 1.5 foot. The hull length to beam is 8.5 to 1. The hull appears to be curved forward then go into a chine with a flat bottom. The rudders have an interesting steering cable connection to the rudders.

    The structure is basically timber. The hull bottoms are 22 mm thick carvel, the hull sides and decks are 10 mm timber in 50 mm wide strips again carvel. The bow frames and timber are curved from the bow to frame 7. The frames from frame 7 are 50 x 25 mm straight edged timber. All frames/ribs are 400 mm apart. The aft sections are also slightly curved. The keel is 50 x 130 mm deep and gunnels are cut from 60 x 60 mm timber. The crossbeams 150 x 35 mm timber. The glue is unknown. The deck is covered with canvas. The estimated cost of the cats materials is $60.

    Why didn’t they use plywood, fiberglass, epoxy and Dacron sails? Because they were not invented for another 50 years. Did I forgot to mention the design and specifications were done by “Paddlefast” and was first presented in an 1878 (yes, 1878) Scientific American magazine. Paddlefast claims the cat can sail at 14 knots.

    The designer was probably inspired by Nat Herreshoff 25 foot catamaran Amaryllis built and raced in 1876 to about 1880 (jpegs below). Paddlefast also suggested that the cat could be extended to 30 x 15.5 foot with increased timber dimensions. The length to beam on the 30 foot version is 12 to 1. One feature I liked was the need to carry a 30 lbs anchor in the 25 foot cat and a 34 lbs anchor for the 30 foot version.

    The first jpeg is of the above 25 foot cat. The next are of Nat Herreshoff 25 foot cat and the final is the hull lines of the 34 foot version of Nat Herreshoff cat. We have come far in terms of materials and rig design, but the basics of the cat design concept was well established 150 years ago. Well done Nat Herreshoff and Paddlefast.
     

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    Last edited: Feb 22, 2021
  14. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    you need to put that boat on a diet...

    basically walk throughout and eliminate or change the weights you can

    when a boat owner has the thing, overtime, they just keep adding and adding; after awhile; there are 5 rolls of duct tape, 16 screwdrivers, chest freezers.

    I like to take the weights of everything I remove and then see how little I add back and I actually spreadsheet it; recently, I removed 53 pounds from a 16' skiff by drop adds..
     
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  15. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Othmar Karschulin wanted a racer for the 10 foot class. He choose a proa. The proa is 10 x 6 foot and weighs about 120 lbs with a maximum displacement of 300 lbs. The mast can be an 8 foot segment of a windsurfer mast which supports a 65 square foot Gibbons rig. The Gibbons rig requires a boom and spirit which can be created from EG bamboo or again broken windsurfer masts glued together. The sail can be a flat polytarp or light sail cloth. The rigging is low stretch ropes. The main hull has a length to beam of 9.5 to 1 and a prismatic coefficient of 0.65. The float is 7.5 foot long and displaces 80lbs.

    The main hull is constructed from 4 mm plywood with all frames and the stems made from 8 mm plywood. The box hull shape has 15 x 15 mm chines and gunnels. All glued with epoxy. The cross beam holders are made from 8 mm plywood. The float is a V section stitch and glue shape of 4 mm plywood with 15 x 15 gunnels. The cross beams are 50 mm aluminum tubes. The asymmetric daggerboard is 3.2 foot long with a flat 8 mm ply face 200 mm wide and a 4 mm ply curved face with a 15 x 15 mm centre web. The main hull has a daggerboard case.

    No performance details but it would be a bit of fun to find out. The jpegs give the idea.
     

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