Dimensions: 64'6" LOD, 62'9" DWL, BOA 35'6" BWL of each hull 5'2", BMax per hull 7' 6", Draft in cruising trim, 3'9", Freeboard 7'6" in cruising trim, Cruising displacement, 45,000 pounds
Design statistics: Prismatic coefficient of .65. LCB 36.25, LCF 35.9, PPI per hull 1345# (multiply x 2 for the total PPI,) hull draft 1'2" at 45,000 displacement, Footprint weight 19.5 pounds per sq. ft. (This is the displacement divided by the footprint, or the overall length x the overall beam-The Gunboat 62 has a disp. / footprint of 17, and standard cruising catamarans are about 26,) DWL/BWL of hulls, 12.125. Bruce Number @ 45,000# 1.38, Air draft 70', Sail Area to Disp. ratio 30.35 (at 45,000 disp.,) Displacement to Length ratio 78.5 in cruising trim with full tanks, 61 lightship, and the Bill Roberts' K Factor of 3.3 which is governed by the DWL to BWL ratio, predicts a maximum speed of 26 to 26.5 knots. (Note: Where displacement is not specified, I am using the displacement in cruising trim for all calculations, with the vessel's very large tanks full. For lightship, subtract about 10,000 pounds, and for half-loaded, subtract 5,000 pounds. Unfortunately, most builders and designers don't tell the reader which displacement they are using. When in doubt, I assume lightship.)
The "V" section is carried right aft, insuring that the hulls will not slap even if anchored in an open roadstead. The transoms are well tucked up and the buttock lines exit at a very low angle, guaranteeing speed under sail. The bows are narrow at the waterline, have no bow overhang, and yet have a lot of reserve buoyancy to prevent burying the lee bow, because the deck is much wider at the bow than it is at the waterline. This feature is called flam, though it is often mis-called flare. Flam is a positive outward curve in a section, however, and flare is negative or reverse outward curvature in a section.
Design Features: In effect, this design has the accommodations of a standard 50' design stretched to 65' in length. What you get when you do this is a faster boat, as it has a longer waterline and a relatively narrower waterline beam for the hulls. You also get many watertight compartments, greater privacy for the cabins, full engine rooms with shaft drives rather than saildrives, and no more weight for a given set of materials. Additional benefits are simpler construction and no berth "shelves" to make noise and slow the boat.
(Read Charles Kanter's critique of shelves at Elusive Cruising Catamaran Performance )
This boat should move right along, as it has a long waterline, narrow hulls, light displacement, and a large sail area. The rig is low and easily handled, so there is no struggle or anxiety involved in getting the best out of its performance potential. The vessel has a high bridge deck with over 3 1/2' clearance in cruising trim. Even overloaded to 70,000 pounds of displacement, there is a 3' bridge deck clearance.
The sterns are designed to have low resistance even if the vessel is drastically overloaded, and if overloaded, the hull beam and length keep the 12 to 1 ratio as the beam and waterline length increase proportionally. The low 1'2" hull draft (at 45,000 displacement) makes a shoal draft possible, while still giving good lateral resistance due to the ample keels and skegs. This low hull depth is possible because the high-tech materials and construction, long length, and the relatively modest accommodations for a vessel of this size add up to a very light boat which displaces little water for its length.
This interior plan offers complete privacy, with 4 double cabins each of which has its own head and shower, and each of which is accessed from on deck rather than through a companionway. The engines are ensconced in their own spacious engine rooms, where their noise and fumes are isolated. There are 2 fore peaks with a single berth each, which could also have heads fitted for the use of a crew, bringing the sleeping accommodations up to 10 persons.
The use of beams to connect the hulls rather than bulkheads and cabin top gives the builder tremendous flexibility in customizing the bridge deck. In fact, if the builder wished, the cabin on the bridge deck may be omitted, and the helm station may be placed between the connector beams rather than above the aft connector beam. This would reduce the windage, improving windward performance. One option for the interior in this configuration would be to turn one cabin into a dinette and galley, or if a larger galley and dinette were desired, two cabins could be used for the galley and dining area. The bridge deck could then be covered with a tarp cover to provide shade for the 'tween beams area when in port. An open seating and dining area placed here would be quite nice in the tropics.
Flush Deck Version Another layout places two cabins with double berths on the bridge deck. In this configuration, you have 6 cabins with queen size berths and private heads with private showers. You still have two private single cabins with this layout, and so the boat sleeps 14 - 16, if you put bunk beds above the berths in the bridge deck cabins. In this layout, you also have a double dinette that seats 16 and a spacious galley, all on the bridgedeck. What a great layout for charter, sailing expeditions, or a sailing school! SOLAS exempts vessels that carry 12 passengers or less on international voyages, so this design escapes SOLAS requirements-leaving you with a crew of 4, that is, a skipper, two deck hands, and a cook, in addition to your 10 to 12 passengers.
8 Cabin Expedition / charter version There are 10 watertight compartments in the hulls, (5 per hull,) and full polyurethane foam floatation in the bridgedeck greatly exceeding the cruising displacement. The boat is designed to float high out of the water even if completely holed or upside down. The helm station can be either fully sheltered or very well ventilated, at the helmsman's preference of the moment. There is excellent all around visibility from the helm. Kobelt hydraulic steering is specified.
Rig: Easily reefed and furled fully-battened WingSail rig. Unstayed masts with no potential failures due to stainless stress or corrosion fatigue. Maximum and working sail area 2400 sq. ft. The biplane rig is self-tacking and requires no sheet winches, despite its large sail area, due to its balanced design and 7 to 1 sheet purchase. Because the sail can be made as separate panels, which may be attached to the battens rather than each other, and because it has no camber cut in it, the camber coming from the hinging battens, no sailmaker is needed. Using this rig should save over $100,000 USD compared to a marconi rig, which isn't a lot compared to purchasing a large catamaran retail, but it is a huge amount of money to the home builder. This rig saves the builder 25% to 33% of the cost of building the boat.
One version of the rig shown uses a wing sail, in which the sail camber is provided by a hinge at the point where the wing or fairing part of the batten assembly joins the straight portion. This version hides the mast inside the sail, so as to streamline the rig, creating an effect similar to a pivoting wing shaped mast. This is similar to the Swing-Wing rig, except that the fairing portion is a NACA foil shape, which the Swing-Wing rig does not use. This rig is as weatherly as a fixed keel catamaran can take advantage of, and the use of the biplane layout means that the sails will not back wind each other when running downwind. On a beam reach, the windward sail is slacked more than a marconi mainsail, the lee sail is hardened in more than a marconi mainsail, and they form, in effect, a single airfoil when seen in overview. This rig is capable of tacking through at least 90 degrees, and cruising catamarans are rarely capable of that, with tacking through 100 degrees being more common.
Engines: John Deere 6068SFM50 engines are shown. If this engine were tuned to its lowest rpm rating for maximum longevity (M1,) it would produce 182 hp flat out, and burn 9.62 gph. The Deere 6 cylinder (M1) engines would give a top speed of 17.8 knots at 45,000 pounds of (cruising) displacement at the M1 rating, and 14.3 knots at 70,000 pounds of (overloaded) displacement. These engines would be suitable for either commercial use or for a 100% / 100% motorsailer designation.
Running just one engine, the boat could cruise at up to 12.5 knots at 45,000 pounds of displacement, while burning 9.62 gph. To take this to an extreme, one of these engines run at 1000 rpm would push the boat at 4+ knots, giving it a range of 1660 miles, if loaded to a displacement of 45,000 pounds. Running one engine at 1000 rpm while motorsailing to windward would make various difficult windward passages much easier, such as Hawaii to Tahiti, Florida to Puerto Rico, or Panama to Jamaica.
ZF 85a transmissions would be suitable. The engines drive 1 3/4" ss. shafts with traditional bronze stuffing boxes fitted with GFO packing, 24" diameter props located in front of balanced rudders which are fully protected by skegs and rudder mounting struts. Racor 500MA fuel filters with bronze seacocks and cooling water filters, and fiberglass lift mufflers situated so as to be unable to flood engines under any circumstances. There are 440 gallons of diesel tankage under the cabin soles. Extra tankage could be provided under the berths on either side of the midships bulkhead, if more fuel or water than the already generous tankage provided were desired.
Smaller engines may, of course, be fitted. Planning for large engines insures that the vessel will have room for smaller engines and smaller propellers and that the weights on board will balance well with smaller engines. 2-80 to 100 horsepower diesel engines (such as Yanmar 4JH3-HTE engines,) for example, would push the boat at a maximum of 9.3 knots, if run at 2/3 of their rated horsepower with the vessel loaded to a displacement of 45,000 pounds.
Deere 4045TFM-135 hp.(M3) 4 cylinder engines run at 2/3 of their rated speed (106 hp. each,) would push the boat at up to 10.8 knots, if the boat were overloaded to 68,000 pounds of displacement, and at up to 13.5 knots, at 45,000 of displacement. The Deere engines would between them use 5.2 gallons per hour at 1800 rpm, though they can use up to almost 8 GPH each run flat out. Running one Deere engine only at 1800 rpm. (a common practice on catamarans,) would push the vessel at up to 9.5 knots at 45,000 displacement, burn 2.55 GPH, and give a range of about 1500 miles.
These engines are said to be good for 20,000 hours, and were Steve Dashew's choice for his new powerboat, Wind Horse. I think the Deere 4 cylinder engines would be my personal choice. With these Deere engines, ZF 63A 2.05 to 1 transmissions would give the boat 23" diameter propellers. Luke feathering propellers would be a good choice for the props.
Design type: Radius chine design. A radius chine design is a hard chine design where the chine has been replaced with a semicircle to soften the turn of the bilge. This design has a 2' diameter at the turn of the bilges in all sections intersecting with the chine. Despite the large 2' radius, only 2% of the displacement has been removed from the chine version by softening the turn of the bilges. The diagonal measurement of this radiused area is about one foot.
The hull and deck scantlings were designed to ABS Offshore Yacht rules, and the crossbeams to Lloyd's. Hull plans available as DXF files, complete equipment list, electrical, and plumbing plans available, all plans and details compliant with CFR 46. Hulls designed for easy DIY construction.
Materials: Vacuum infused composites using Vectorply quadra-axial e-glass, Reichhold flame-resistant vinylester, and 1" Baltek Gold pre-coated balsa above the waterline. There is only solid laminate below 12" above cruising DWL, and 6" above an overloaded 70,000 pounds of displacement. Connector beams, masts, and battens are made with Vectorply carbon fiber, Vectorply bi-axial e-glass, and Reichhold vinylester.
About 90% of the boat's structure is cored, and the cored panel layup weighs about 2.5 pounds per square foot. The decks and bulkheads can be lighter, if you use less dense balsa, which is permitted. The solid bottom laminate weighs 4.5 pounds per square foot. The wall thickness of the connector beams is about 1" of solid fiberglass, mostly unidirectional laid lengthwise.
The use of vinylester resin makes the hulls blister-proof, while giving almost the strength of epoxy resin without epoxy's high cost and working toxicity. There is no glass mat in the construction. Gregor Tarjan, author of "Catamarans, Every Sailor's Guide," rates epoxy at a 10 for strength, and vinylester at 9.7 (97% as strong.)
The use of balsa instead of foam prevents sun softening of the decks in the tropics, makes a stronger and lighter hull, and is less costly and more fire resistant than foam. The balsa is kept well above the waterline and well away from the deck edges, insuring that there will be few places where the builders need to protect the balsa core from penetrations. Lifeline bases and sampson posts, for example, are located in areas with no coring.
Construction method: Flat vacuum-bag infused panels are made on a melamine-surfaced laminating table. All panels except for the narrow hull bottom panels are made with balsa core. Hull panels are assembled on cradle with no mold required. No fairing or filling required except a minor amount at the chine radii, and at panel joins. All panels are made full-length, and so have a natural tendency to be very fair, as well as requiring few joins.
Detail of panel joints of hullsSince the hulls get their shape from the cradle, the cradle is essentially a negative of the chine shape, with cradle members at each section, so there are 10 cradle frames. There is no mold, however, except a small radiused area about 6" above and 6" below the chine. Purchasers of the plans can get custom-cut sheet metal connectors which have the correct angle for joining the chines already built in. We can supply these, or we can supply CAD files which builders can have cut at a local CAD shop, such as a laser or plasma shop. It is rather like using Simpson metal building brackets to build a house. This method eliminates lofting, mold making, and at least 90% of the fairing that usually is done when building a custom boat.
Easy method for making radius at chines: Radii at the chines made by attaching sheet material to the cradle at the chines, filling the chine area with Bondo, plaster with glass fibers, or similar, and scraping out the excess filler with a section of a 2' diameter circle cut in plywood while the Bondo or other filler is still wet. This forms an easily made mold for the radius, and makes the hulls easy for amateurs or professionals to make. The radii of joins between the topside and hull bottom panels are the only place where anything resembling a mold is used during the hulls' construction. The same method is used at the join of the deck and hull topsides, to provide a 3" radius. Note that the chine-radius filler is part of the cradle, not part of the boat, so it doesn't add to the weight of the boat.
Easy method for making composite masts: This simple mold-forming technique can also be used at the deck edge, and at any corner or edge to be given a radius. It can even be used to make a form for the masts, by making a mast-length plywood or OSB box and filling the box with reinforced plaster, Bondo, etc., and scraping out the excess while still wet. One may make an accurate taper by placing "bulkheads" at intervals in the box with the desired semi-circle at each point being cut in the bulkheads. Attach strips to form an overlap on one mast half per mast, and bond the halves with Plexus cyanoacrylate structural adhesive. This will give a circular mast section when finished.
Or, for those seeking something a little more traditional that still offers 4 private cabins, easy construction, and easy handling--
This monohull has 4 double berth private cabins, a dinette that seats 8, 2 heads, one with a shower, inside steering, a chart table, a "garage" for a single and a double sit-on-top kayaks, and the pilot house has excellent visibility for the cook, the helmsman, all 8 people sitting at the dinette, and the navigator. The compromises are that the navigator has to stand if he is using the navigation station, and the cockpit is only 6' long.
It has a junk schooner rig of the modern, weatherly, cambered sail type and a long 64' waterline. This long waterline gives it a hull speed of 10.8 knots, if it is calculated at 1.35 x the square root of the waterline. The DWL is only 15' wide, so it has an easily driven hull with a beam to width ratio at the waterline of over 4. It is very stiff, however, as it picks up bearing rapidly as it heels, due to the immersion of the chine. Despite the fine bow and stern, it has a shallow buttock exit line (an easy run, it is sometimes called,) for a good turn of speed and minimal fuss in the wake.
The design statistics for this monohull design are: LOD 64', DWL, 64', Beam Max 16 1/2', Disp. 61,000 lbs., Draft 6' 1.5", Ballast 24,000 lbs, Ballast/Disp ratio 39%, Square root of DWL 8, SA/Disp 21.79, (if you use 80% of the sail area to figure this, as this is the maximum possible sail area, the SA/Disp ratio is 17.44,) LCB 53%, LCF 54.5%, PC .57, CE Height 33.75', VCG 2" below the DWL, Hull form righting moment at 30 degrees of heel (does NOT include ballast effect,) 211,553 lbs.
This boat would be great for high-latitude expeditions or for sail training. Alternatively, you could put a sizable family on board, with privacy for a couple and 3 kids. It could easily be adapted for radius chine construction if a "yachtier" look were desired.
To purchase plans or kits, E-Mail Tim Dunn at:
dunnanddunn@gmail.com
Resin infusion links: See Tim's resin infusion links on the Yahoo resin infusion group Tim started.
Tom Speer's aerodynamic paper on wing masts and sails
Junk rig skeptics should know that this rig is not just a theoretical concept for me, as I sailed a 34' junk schooner whose rig was designed by Blondie Hasler, Batwing, from Seattle to: the Marquesas Islands, the Society Islands, Samoa, Tonga, New Zealand, Fiji, Tuvalu, Kiribati, Guam, the Caroline Islands, Papua New Guinea, Palau, the Philippines, and Hong Kong. Skeptics should also know that Batwing, displacing 18,000 pounds and having 770 sq. ft. of sail area, normally operated under sail rather than under its small 20 hp. motor and 2 bladed propeller, and that she tacked through many a strait and channel against headwinds.
Arne Kverneland's article on putting camber in the junk rig to make it more weatherly. He is a pioneer in this area.
Cruising World Article
Dunn and Dunn, Realtors -Offering large rebates, discounts, and full service to home buyers and home sellers in the Seattle metropolitan area and western Snohomish County.
Seattle Metro Real Estate A blog that addresses the question: "Is Seattle in a housing bubble?" with facts and logic, instead of hype and hysteria.
Steel Silhouettes A webstore selling cut metal art, crafts, gifts, and lighting fixtures with Pacific Northwest Indian and wildlife designs by Tim Dunn
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Tandem (Bi-plane) rigged catamaran links
http://marine.bdg.com.au/
http://www.schionningdesigns.com.au/www/page.cfm?pageID=271
http://www.sailcoolchange.co.nz/
http://www.parlier.org/hydraplaneur/actualites/superbreve.php?lang=fr&id=16
http://www.cat2fold.com/
www.flyingcarpet.co.nz/about.html/
www.jasmine.org.uk/~simon/boats/slippery/slippery_0_4.html
www.scrumble.com.au/a-different-sailing-rig-for-scrumble/
outside.away.com/outside/magazine/200011/200011sailing7.html
Windmek wingsail
Omer wingsail
Wingsails.com
Windjet wingsails
Wingsailor.com
rcsailing.net wingsails
Wingsails
Boatdesign.net wingsails
A go fast machine with a rigid wingsail in Oz
http://www.duckworksmagazine.com/04/s/vintage/multihulls/index.cfm
http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=54225 
The junk rig user's group on Yahoo. This group has an archive of almost 11,000 posts.
Another Kanter Article
Dave Gerr on Stability
Shuttleworth Articles
Elusive Cruising Catamaran Performance
Seaworthiness and Safety by Derek Kelsall
Offshore Sailing Performance by Derek Kelsall