Multihull Structure Thoughts

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

  1. oldmulti
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    oldmulti Senior Member

    After yesterday’s tri today is about an affordable sailing cruising cat for a lot of people. The Lady Hawke 33 is an Erik Lerouge VIK 101 design of 32.8 x 18 foot with a weight of 7,800 lbs and a displacement of 10,800 lbs. The 42.5 foot rotating aluminum mast carries 485 square foot square top mainsail, 270 square foot jib and a 540 square foot genoa. There is an optional 49 foot rotating carbon fibre mast and larger sail area available. The low aspect ratio keels draw 3 foot. Power can be two 20 HP diesel inboards or EG 2 x Oceanvolt SD6 6 kW electric sail drive motor powered by 48 volt batteries and a generators.

    The interior has 3 double cabins for 6, a large toilet and shower, a spacious saloon containing a dinette and compact galley. There is full headroom in the wing deck and hulls in most areas. There is a reasonable cockpit with twin steering and most control lines leading to the cockpit.

    The build of the cat is polyester resin and 75 KG PVC foam of 15 mm in hulls etc and 30 mm in main bulkheads and under wing. The molded cabin roof has substantial reinforcing under the genoa tracks and around the mast base. The hull underwing mould is done as one unit as are the deck cabin roof. The wood used for the interior are in marine okumè plywood and Rovere light. Erik Lerouge has a lot of design and build experience prior to the start of 2008 production and cats were still being produced in 2017. They are still advertised.

    The cat peak speed is quoted at 17 knots which is realistic. One test sail said “Sailing is also very good, on sea trials, with a wind of about 13-15 knots, the maximum speed was 9-10 knots. On a reach, we confidently sailed at a speed of 6-8 knots with an appropriate wind.” This is a solid cruising boat. The cat sails upwind well and tacks without backwinding.

    This is more about a good sailing cat that can be sailed by a couple, at a size that is affordable and does not take a lot of people or effort to take out on a day sail. The jpegs give the idea.
     

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  2. oldmulti
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    oldmulti Senior Member

    Lady Hawke additional jpegs.
     

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  3. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    The following is a summary of several web sites on issues with Lagoon catamaran bulkheads. Main bulkheads and secondary bulkheads on certain models have had issues. As one owner said “From my research on L400, not big issue if not worried about upwind performance. If bulkhead cracks. then you gotta fix it.” Other owners seem to want to go to windward and are little more concerned

    Lagoon 450 bulkhead issues 2021: 450 450 Bulkhead issues - Report them please. - Cruisers & Sailing Forums https://www.cruisersforum.com/forums/f139/450-bulkhead-issues-report-them-please-249741.html

    “It appears that the main mast bulkhead on the L450 was underbuilt. It is a defect that is hidden under the trim and will not cause damage in the marina. However with 100s of boats out sailing oceans it is starting to show up too often to ignore.

    It is repairable and the repaired boat will be better than new, but the repair involves removing a lot of cabinetry and $$. It would be easier and cheaper to solve on the production line, but that means the manufacturer would have to admit to the problem and retrofit all unsold inventory.

    The OP is trying to start an organized program to address the issue, but is meeting resistance from the manufacturer and the current owners who have taken the head in the sand approach. I don't see the manufacturer as the solution--like defective airbags in cars--the manufacturer doesn't have the resources to fix the problem on their own.”

    Facebook group regarding the bulkheads is: Facebook Groups https://www.facebook.com/groups/902269000568556

    Lagoon 38 bulkhead issues 2019: Re-tabbing Bulkheads on a Production Catamaran https://www.boatdesign.net/threads/re-tabbing-bulkheads-on-a-production-catamaran.62499/

    “Problem statement: After numerous years of full-time cruising in the Caribbean, we have noticed that many of the smaller bulkheads and furniture paneling has separated from the hull. This specific manufacturer has a history of poor varnish application and service life. Finally, after one too many rough passages, we began to notice that some of the glue joints (it is believed to be Plexus, but if anyone knows what was being used in France back in 2003 please let me know) have failed at the wood interface. It is only the wood interface that the adhesive has failed. During some destructive testing, I did observe that the bulkheads were varnished prior to tabbing and that the varnish under the fillet has lifted from the wood, thus creating a tabbing failure (through no fault of the actual adhesive).”

    Lagoon 440 bulkhead issues 2020: How to upgrade the bulkhead on a Lagoon 440 https://catamaranimpi.com/2020/07/28/how-to-upgrade-the-bulkhead-on-a-lagoon-440/

    “According to the Lagoon factory there are main structural bulkheads and non structural bulkheads.

    The structural bulkheads are the mast bulkhead and the engine compartment bulkhead. They provide some rigidity to the hull. These are tabbed in.

    Then there are several smaller non structural wood bulkheads which form the floor frames. These are stiffened by a composite process, a kind of resin putty is applied to fix them to the hulls.”

    “A common occurrence on a Lagoon 440 is that the non structural bulkheads get cracked.

    Later models such as Impi which is a late 2009 model have the entire main bulkheads from mid hull starboard to mid hull port glassed all the way around. However, some earlier models were not glassed on the top section where the deck meets the bulkhead under front windows / above the water tanks. The issue then is that the ‘mast forces’ through the mast support post can work this section loose. Therefore, it is important to remove the water tanks and glass that section in if not already done.”

    “To recap – the main bulkheads are glassed in from midship of one hull to midship of the opposite hull, the outer sections are fitted with a resin or resin putty type bonding material which although very strong is not strong enough to hold in severe flexing situations.”

    “For this reason when we purchased Impi we decided to tackle the serious parts of this – let me use the worst section as an example – itʼs no secret that on a 440 and some 450ʼs the weak point is the port side bulkhead under the forward cabin section where one climbs over to get into bed.”

    This is information and please read the web sites and facebook page for further detail. Comments are welcome but please keep to known facts. Jpegs of the Lagoon 440 bulkheads attached. The PDF is a photo of the Lagoon 38 bulkhead.
     

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    Last edited: Jul 11, 2021
  4. oldmulti
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    oldmulti Senior Member

    This performance cruising catamaran design comes from one of the worlds best boat builders. McConaghy Boats has built some of the fastest global racing multihulls such as Ellen Macarthur’s 75 foot B&Q. Some of McConaghy Boats previous performance cruising cats have been very high tech and very interesting.

    The new S-49 is a Schoinning performance cruising cat design being built and released by McConaghy Boats. The S-49 is 49 x 25.9 foot with a weight of 18000 lbs and a displacement of 26,900 lbs. The mast height is 59 foot (optional rotating carbon fibre) with a 870 square foot mainsail, 433 square foot self tacking jib, 533 square overlap foot headsail and a screecher of 861 square foot. The hull length to beam is about 13.5 to 1 with a draft of 2.1 foot with boards up and 7.1 foot with daggerboards down. The underwing clearance is 2.75 foot. There are two 50 HP engines.

    The cat was designed primarily as an efficient fast sailing cat with high bridge deck clearance and chamfer panels to minimize slamming. Weight is centralised to reduce pitching and build weight is around 30% lighter than most of the competition. Twin daggerboards improve windward performance. The S49 will be very easy to sail using electric winches at the raised helm station, with all lines running back to the helm position it makes her a good single or shorthanded cat. Single line reefing and furling headsails operated from a static control station makes handling a breeze.

    The accommodation features 3 double berth cabins in the hulls with each with their own ensuites. The main bridge deck cabin contains seating, table large galley an entertainment area. The lower cockpit has a large door to the main cabin. The steering and sail control cockpit can seat 2 and is located on the lower cockpit roof top.

    The cat is built in E-glass, epoxy, and PVC foam sandwich construction with carbon fibre structural elements. The bulkheads are the same structures. The advanced engineering of the boxed bridge deck not needing a back beam and moving the main sheet track up onto the cabin top which is visible and controlled from the helm station.

    Now, I am officially bored. This is about the fifth version of a Schoinning design in the 47 to 50 foot performance cat design that has similar dimensions and structure. Some are production cats but EG the G Force 1500 can be built at home. This size range can produce very fast, well balanced cruising cats from many designers and as long as you have electric winches can be handled by a couple. They have to built lightly but as you can see from the S-49 E-Glass PVC foam and epoxy with some carbon fibre is all that is needed and in the capability of a home builder.

    The jpegs give the idea.
     

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  5. oldmulti
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    oldmulti Senior Member

    Folks I am confused, the Torr 679 looked familiar then I read the promotional material where it said “The Torr 679 Catamaran was designed as an easy to sail multi-hull yacht, which could also be trailed by the average family car without the need for demounting or expensive collapsible trailers” followed by “the TC 670 is ideal for a couple, or a family with young children.” In short, the company, Andaman Boatyard, appears to be building a “version” of a Waller TC 670 catamaran.

    The details are lacking from Andaman so I will assume the TC 670 specifications are fairly close. The TC670 is 22 x 8.2 foot weighing 1730 lbs and displacing 2400 lbs. The sail area is 250 square foot.

    The major differences are a more rounded and streamlined deck shape and round bilge hulls. The Torr 679 diagrams show hull based dagger boards but the publicity write up says it has a central rudder and wing based central daggerboard as in the TC 670. The Torr 679 bows shape have a slight reverse shape. The stern cross beam and cockpit area has also been modernised to allow steps from the stern to the cockpit. The wing seats on the TC 670, used for additional stability, have been eliminated in the Torr 679.

    There is no mention of the build materials for the Torr 679 but it hopefully is in foam glass, as the shapes of the hulls and decks would be a little hard to produce in plywood and timber. The original TC 670 was a full plywood timber structure with a simple multi chine hull.

    I hope this is a fully approved design variation by Mike Waller as his original TC670 was/is a good sailing cat for those who want a relatively fast cruising real trailer sailor. Why the slight caution? I know of one owner who had a Jarcat 6, a 20 foot plywood cruising trailer sailor with similar internal accommodation. He sold it to buy a TC 670. After a year of sailing the TC 670 he sold it and purchased another Jarcat 6. His reason for the change to the TC 670 was to have a faster cat with the Jarcat 6. The TC 670 proved to be “to much” boat for him. The TC 670 could go faster at times but took more attention and physical effort to drive fast. When cruising the Jarcat 6 was easier to sail and had accommodation that suited his needs better. In short both cats worked for him but one was more suited to his style of sailing.

    So, does anyone know any more about Andaman, the Torr 679 especially the build and how much Mike Waller was involved. It looks a shapely design but is this vapourware or reality? The jpegs give the idea followed by TC 670 jpegs and Jarcat 6 jpegs.
     

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  6. Burger
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    Burger Junior Member

    That's progress for you.

    Jarcat 6 to Waller 670: more freeboard, more weight, a slightly tighter interior layout and slightly more money/time to build.

    Waller 670 to Torr 679: much higher cost due to round bilge foam/glass structure, unnecessary streamlining of cabin, fashionable but pointless reverse bows. The stern steps are an improvement. Looks cutting-edge and racy, but in real world probably performs much the same as the other two.

    I've been inside both a J6 and a Waller 670, and definitely prefer the J6 interior arrangement. About the same space, but a much more open feel, which matters on a small boat.
     
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  7. oldmulti
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    oldmulti Senior Member

    Gary Baigent, I hope you can help filling in some details. The following jpegs are all I know about the design beyond some limited detail. The trimaran is known as “Bladon Racer” which was a 40 foot trimaran designed by the late great Jim Young from NZ.

    The rig called a “sketch” has two 45 foot aluminium masts carrying a 380 square foot mainsail on each mast with a 400 square foot genoa. “This was a low sail plan which kept the centre of effort down and reduced the tipping moment,” said Jim Young. Jim thought the tri would have been really fast if it had more sail on a single mast. Another version of this trimaran was built for the Kendall family with a single mast named Trilogy (jpeg below).

    Blaydon Racer was built using West System in Tauranga by the late Dooley Wilson for his son Nick Wilson who still lives in Tauranga on Devonport Road. Dooley Wilson is a skilled builder and I assume it is moulded plywood and timber construction. The diagrams indicate aluminum cross beams with waterstays. The centreboards are in the floats. Although Young drew water ballast to be carried in the windward float to provide extra power, this was not fitted by Wilson. In the clever drawing, tanks which were linked to the centre board cases, could fill or empty to produce either buoyancy or lever arm weight. The rudder is kickup and mounted on the stern.

    There is an aft cabin and what looks like a large main cabin area with a “centre cockpit”.

    An interesting design that was described as a fast cruiser. The tri is 40 years old but still sailing. If anyone knows more can you please advise.
     

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  8. guzzis3
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    guzzis3 Senior Member

    Yeah don't get me started on mini bridgedeck cabin cats. We should probably have a separate thread just to really discuss them.

    There have been quite a few, but self build and plans. I had a J5, but it shoul be pretty obvious the advantages and disadvantages of each type.

    The Waller is one of the bigger trailerable designs. It's not my favourite. If I built one I'd probably go for Ray Kendrick's 18' version but I'd prefer a jarcat rig and leeboards inboard on each hull, or fixed lar keels. These choices are compromises, but so is every option.

    Shame there were not more little barriers made.

    They are potentially great boats. Executed well they are as easy to trailer and launch as a small mono TS, have relatively vast accommodations, good performance and are terribly handy in thin or narrow water. Run it up on the beach, tow it with a small car, sleep a family of 4 in real comfort.
     
  9. oldmulti
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    oldmulti Senior Member

    The following trimaran “3D” is a home designed and built tri by Rémi Fermin (builder of 2 Mini Transat prototypes, including the last with which he finished 3rd in prototypes in 2013) in 2015. The tri is 35.5 x 27.9 foot with a weight of 5800 lbs. The 54 foot fixed aluminium fractional rigged mast carries a 475 square foot mainsail, a 230 square foot self tacking jib, a 430 square foot genoa and a 710 square foot code 0. The mainhull length to beam is about 9 to 1. The engine is a 15HP outboard.

    The accommodation is 1 double berth aft under the cockpit, 1 single berth forward, 1 bathroom and a saloon with galley.

    The construction throughout the main hull and floats is a sandwich of Airex foam / Epoxy. High modulus carbon fibre and epoxy is used in the rudder, float based daggerboards, cross beams and bowsprit.

    The numbers indicate a fast trimaran with very full buoyancy floats that will provide a lot of power matched with a rig that in light to moderate conditions provide a lot of drive. Performance is to quote the current owner “Indeed 3D is a simple, fast and comfortable boat that requires little maintenance and is remarkable under sail from all points of view. I realized an old dream going through the summer of 2018 of Guadeloupe in Brest alone with a remarkable 9 days of weather between the West Indies and the Azores”

    This is a well designed and built tri by a man who understands what is required to make a boat perform. It may not have the smooth looks or luxury accommodation but it is a very fast cruiser. The jpegs give the idea.
     

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  10. guzzis3
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    guzzis3 Senior Member

    Can someone explain the difference between a code 0 ad a screecher ?

    I thought they were the same but mono sailors call them code 0 and multi sailors call them screechers ?

    Either way I have thought that my next boat will carry one in leu of a spinnacker. I am less comfortable dead downwind especially in a following sea. A really broad reach seems better.
     
  11. redreuben
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    redreuben redreuben

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  12. oldmulti
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    oldmulti Senior Member

    Several people on this thread have made comment about small cruising catamarans as being practical trailer sailors. I will stay with known designs that have been built and sailed with an 8 foot beam and compare them. In all cases I am accepting the designer’s weight, displacement and basic sail dimensions. This will be a 2 part presentation with the cats description and some structural details provided today and “performance stability” calculations tomorrow.

    The cats are: Eco 5.5 (Kohler), Chat 18 (Woods), Scarab 560 (Kendrick double shuffle), Jarcat 6 (Turner), Saylon 20 (Woods) and TC670 (Waller).

    Eco 5.5 is 18 x 8.2 foot weighing 650 lbs and displacing 1390 lbs. Sail area is 200 square foot 123 square foot main and a 77 square foot jib. Deck 6 mm plywood, 12 mm ply underwing, 12 mm main bulkhead, 6 mm ply hull planking, 20 x 25 mm stringers timber. Rig centre of effort 13 foot, hull c/l beam 6 foot.

    Chat 18 18 x 8.2 foot weighing 700 lbs displacing 1500 lbs with a mainsail 120 square foot headsail 75 square foot mainly 6 mm ply with 9 mm ply underwing and bulkheads. Five 100 x 50 mm “cross beams”. Taped chines. Rig centre of effort CE 12 ft, hull C/L beam 5.9 foot.

    Scarab 560 18.3 x 8.2 foot weighing 1250 lbs with rig fuel water displacing 1800 lbs with a mainsail of 97 square foot and a jib of 54 square foot. The mast is 19 foot. 6 mm plywood hull planking, 9 mm underwing, bulkheads and some 9 mm plywood decks. 320 gsm glass in epoxy inside and outside. Taped chines. Rig centre of effort 11.6 foot, hull C/L beam 5.6 foot

    Jarcat 6 is 20 x 8.2 foot weighing 875 lbs displacing 1600 lbs with a mainsail of 120 square ft headsail 100 square foot 6 mm plywood hulls, deck and underwing sheathed with 84 gsm glass in epoxy. Bulkheads are 6 mm plywood with timber reinforcing. Chines are 20 x 40 mm stringers are 19 x 19 mm timber. Rig centre of effort 12 ft, hull C/L beam 6 foot.

    Saylon 20 20 x 8.2 foot weight 1500 lbs displacing 2050 lbs mainsail 140 square foot jib 75 square foot. Hull forward 2 layers 4 mm plywood, 6 mm plywood hull sides, 9 mm ply keel plate 6 mm plywood decks, 9 mm plywood underwing, 200 gsm cloth epoxy sheathing. Rig centre of effort 13.5 foot, hull C/L beam 5.75 foot.

    TC670 22 x 8.2 foot weighing (trail weight including mast rig some stores) 1720 lbs, displacing 2400 lbs with a sail area is 248 square foot. The hulls are 6 mm plywood and bulkheads, underwing, deck are 9 mm plywood all sheathed in 200 gsm or 330 gsm cloth and epoxy. There are 20 x 40 mm hull stringers, taped chines. Rig centre of effort 14.5 foot, hull C/L beam 6 foot.

    The rigs on these cats can be custom built but the majority use ex beach cat rigs and sails from eg the Hobie range of cats. All of the above cats are strongly built with 6 mm plywood hull sides etc. Woods, has 24 foot cats that have good 4 mm or 4.8 mm plywood sides that are sheathed in 200 gsm cloth. Interiors on the above vary with some using 6 mm plywood bunk tops others 9 mm plywood bunk tops, some use 6 mm plywood cabinet panels others 4 mm plywood cabinet panels etc. Result is for similar sizes of catamarans there are significant build weight differences which has performance impacts as we will see tomorrow.
     

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  13. guzzis3
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    guzzis3 Senior Member

    Thank you very much for that. It seems I have been mislead. All these years I've been calling a code 0 a screecher. This was because I was told that was the case. I wonder if sailmakers encounter this sort of mislabelling and get frustrated by it. Maybe if I'm getting sails made it's better to simply specify what I am trying to achieve rather than name the sail.
     
  14. redreuben
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    redreuben redreuben

    [QUOTE="guzzis3, post: 912261, member: 34257" Maybe if I'm getting sails made it's better to simply specify what I am trying to achieve rather than name the sail.[/QUOTE]

    Yes, very much so, even if you and sailmaker agree on the name like “mainsail “ you still have to specify wind range, longevity, preferred fabric or construction. Few **** ups are made from too much information but plenty with too little.
     
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  15. oldmulti
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    oldmulti Senior Member

    The performance of the 18 to 22 foot cruising cats range from moderate to good. A beach cat of this size will be faster but they do not have covered berths and some kind of galley or loo. The following performance calculations are done with simple formula so only show a trend not an accurate figure. Also, each cat’s rig and crew often define performance more than the basic cat hull form etc. In each case below there is the basic cats performance then a second case with outboard wing seats for the crew to sit on which adds more righting moment and improves sail carrying capability.

    Eco 55 basic has a 4170 ft lbs righting moment (RM). Maximum wind speed before capsize, 17.4 knots. The “average” boat speed would be 7.6 knots with a Bruce Number of 1.27.

    Eco 55 with outboard seats has a 5920 ft lbs RM. Maximum wind speed before capsize, 20.75 knots

    Chat 18 basic has a 4500 ft/lbs RM. Maximum wind speed before capsize, 18.1 knots. The “average” boat speed would be 7.4 knots with a Bruce Number of 1.24.

    Chat 18 with outboard seats 6250 ft/lbs RM. Maximum wind speed before capsize, 21.3 knots w/s.

    Double shuffle 560 basic has a 5040 ft/lbs RM. Maximum wind speed before capsize, 23.1 knots. The “average” boat speed would be 6.5 knots with a Bruce Number of 1.01.

    Double shuffle 560 with outboard seats 6860 ft lbs RM. Maximum wind speed before capsize, 27 knots.

    Jarcat 6 basic has a 4960 ft/lbs RM. Maximum wind speed before capsize, 17.5 knots. The “average” boat speed would be 7.8 knots with a Bruce Number of 1.27.

    Jarcat 6 catamaran basic has a with outboard seats 6365 ft lbs RM. Maximum wind speed before capsize, 19.8 knots.

    Saylon 20 basic has a 5950 ft/lbs RM. Maximum wind speed before capsize, 19.7 knots. The “average” boat speed would be 7.2 knots with a Bruce Number of 1.12.

    Saylon 20 with outboard seats 7750 ft/lbs RM. Maximum wind speed before capsize, 22.5 knots.

    TC 670 basic has a 6960 ft lbs RM. Maximum wind speed before capsize, 19.2 knots. The “average” boat speed would be 7.9 knots with a Bruce Number of 1.28.

    TC 670 crew on outboard seats 9120 ft lbs RM. Maximum wind speed before capsize, 22.3 knots.

    The wind speed figure is the apparent wind speed that will cause a capsize. Most sailors will reef a few knots of wind speed below the capsize wind speed. The outboard seats will provide more stability and in most cases the ability to handle 3 knots more wind speed. In most designs it would be practical to add outboard seats. Saylon 20 could have outboard seats added but the deign is more cruising orientated than other cats here.

    I regard cats capable of handling 25 knot apparent wind with full sail as coastal capable, below 25 knots capsize wind speed I would keep to bay and river sailing. Wave heights in 20 knots of true wind can generate up to 8 foot waves in open water. In 25 knots of true wind waves can range from 8 foot to 13 foot in open water on top of any swell. The reason this is important is studies have shown that cats are suspectable to wave capsize if wave heights are greater than the cats beam.

    From the above information the “safest” cat is the Scarab 560 Double Shuffle but it also is the slowest on average.

    The fastest cats are the Jarcat 6 and TC 670. The Jarcat 6 due to its light weight, the TC670 because it is the longest and has the biggest rig. The Eco 55 and Chat 18 are nicely balanced between build weight, sail area and speed.

    Each of the cats have a market, it depends on your needs for interior space, ease of building, structural strength and sailing capability. You, could “hot rod” all these designs by building them lighter (EG shorter wing decks, 4 mm ply on hull sides, 9 mm underwing, 6 mm ply bunks etc) and put bigger rigs on them with outboard seats but I take the words of Richard Woods. “Now that I have my own Chat 18, I realise it may have greater performance than some would wish. I know I have a beach cat rig which is more efficient than the gunter rig I drew, but even so some may find the standard rig more than they want. Accordingly, I have now drawn a smaller rig for those who are new to sailing, or who are less active, or even those who just want to chat!”

    In the real world, Jarcat 6 have “Under sail the J6 has bettered 20knots. You are likely to see 12knots in 15 knots of wind, sailing flat. Even to windward the JARCAT SIX can reach 12 knots.” Chat 18’s has “In 12 knots of wind top speed was 9.5 knots and 5.5 knots upwind.”

    The above cats can average 6 to 8 knots comfortably and some will see 16 plus knots in peak bursts or ideal conditions. You don’t need a large cat to go reasonably quickly and storing a boat at home is so much cheaper. The jpegs show a few sailing shots.
     

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