Multihull Structure Thoughts

The Armorkite is one of the few production kite powered boats in the world. It is designed by architect, Etienne Bertrand who has designed 15 small monohulls to date. This mono provides some additional information about kite powered boats which is equally applicable to multi’s as it is to monohulls. The Armorkite is 21.25 x 7.2 foot monohull that weights 610 lbs. The boat has no ballast. The keel is a daggerboard which draws 3.25 foot. There is no mast on this design and the maximum sail area is 270 square foot. The boat has a limited cabin that contains 4 berths and not much else.

Now we get to the rig. The biggest kite sail is 270 square foot but there are 4 other size options of 89, 140, 226 or 248 square foot. This covers wind ranges from 7 to 35 knots. 7 knots of wind is the theoretical minimum required to get the kite off the water. To make it clear, you don’t reef, you change down to a smaller kite size to “reef”. So, we have two issues. One you cannot sail in true winds below 7 knots. Two, having to change kite sizes in eg 30 knots of wind would not be fun. Recovering one kite then having to set and fly another kite is not a 1 minute job. There is also another issue to initially fly a kite it helps to have a drogue behind the boat to help the kite do the initial take off.

There are several types of kites from high performance but less stable, more difficult to control to the so-called self-stable kites, but they have much reduced performance (speeds reduced by 50-60%). Fundamentally, a choice between performance and ease of handling. Armorkite choose a higher performance kite that requires constant attention to keep it flying for best performance.

To sail the kite, the kite is unfolded and the leading edge is inflated. Having inflated the kite, all five control lines are unwound simultaneously using the electric winch. In a low wind range the kite tends to stick to the water, and take off can be tricky requiring the drogue to help take off. The kite takes a couple of weeks to learn to fly, according to its inventors, but it requires constant attention and adjustments while flying which limits its sailing to day sailing, competition sailing or having many crew for 24 hour a day attention.

What does the kite rig achieve? Performance plus. Armorkite top speed to date is 19 knots. In 15 knots of true wind it can sail at 10-12 knots. When its close-hauled the ArmorKite holds a windward course that is comparable to a keelboat, sailing at 30° either side of true wind, at speeds very similar to a Mini 650 of 6-7 knots in 10-12 knots of wind. But where the boat becomes even more impressive is downwind. The test crew had 9 knots showing on the GPS with 11 knots of wind dead astern.

The downside of the Armorkite is although the power developed by the kite is impressive, if there is an error in the angle of the rudder or the kite, or a lack of synchronization between the helmsman and the trimmer, instead of the pulling power being transformed into speed, it tips the boat on its edge. The Armorkite has capsized twice. It was righted like a big dingy.

So, kite rigs can develop real power, provides speed, goes well upwind but needs development to simplify handling and operational usage. The jpegs give the idea. The catamaran was a test vehicle for the rig.

 

I mentioned a NG 45 foot cat that had many build options. The Hiva’oa 45 is a 45.9 x 24.6 foot performance cruising catamaran that weighs 15,200 lbs with a displacement 19,700 lbs. The 60 foot mast (options fixed aluminium, carbon fibre wing) with a 782 square foot mainsail, 443 square foot jib, 900 square foot Code 0 and a 1,505 square foot spinnaker. The fixed low aspect ratio keels draw 4.3 foot and there are underslung spade rudders. The hull length to beam is about 10.5 to 1.

The numbers indicate a performance cat that would be capable of easy 200 mile days and peaks of 20 plus knots. Depending on the rig chosen, 10 to 12 knots close hauled in the right conditions should be possible.

The accommodation is comfortable with 3 or 4 double berth cabins in the hulls depending on the version. There is a toilet in each hull. Look at the bridge deck layout, it’s a little different but logical with the galley and dinette in the centre of the bridge deck cabin allowing separate entrances to each of the hull cabins.

The construction options for this design are many. The plywood/timber version has a multi chine hull and is epoxy saturated. The DXF files allow the plywood panels to be cut to shape allowing faster assembly. The exterior has a moderate fiberglass layer over in epoxy. Next option is strip plank western red cedar and epoxy glass with round bilge hulls, decks etc. The bulkheads are plywood timber and its all taped together with epoxy glass. The next option is a polyester foam glass sandwich version. The designer can mix and match the options to have EG foam glass decks on strip plank hulls etc. NG design is also very competent at aluminium and has several designs in the 42 to 46 foot size in aluminium.

The jpegs give the idea. Also, it would be fun to fly to Tahiti to sort out the plan details. Some designers live in nice places.

 

A Swiss man had a dream of a more practical boat for him to cruise around Asia. He designed his own Proa “Nixe”. The proa is 38.7 x 25.6 foot with a weight of 4,050 lbs. The 37 foot hollow wooden round mast 150 mm in diameter carries a mainsail of 166 square foot, a jib of 150 square foot and a genoa of 295 square foot. The main hull length to beam is 12 to 1. The length of the Float is 26 foot with a length to beam of 9.5 to 1. The main hull beam at the gunnel is 8 foot. The proa draws 2 foot when the daggerboard rudders at either end of the main hull are raised and draw about 3.7 foot when down. An additional foil for more leeway prevention was installed later. The last jpeg shows it.

Nixe was designed to be a real cruiser for 2 people with a double berth, toilet cabin, dinette, galley and a lot of shelf storage. The proa has 6.5 foot headroom. It has 400 litres of water and 4 anchors, anchor chain, dinghy, outboard etc. To quote the designer “One of the reasons I build this boat is that I realised I don’t need that much space as I had in my previous boat. In 12 years I used the second cabin only 7 times and I also could have slept in the cockpit while the guest takes my cabin. That is not worth sailing an empty cabin around. So I found I don’t need a 11.70m yacht, but a 12m proa. I now have exactly the living space my wife and me need.”

The designer aimed at light weather performance as Asia especially around the equator has relatively low wind speed averages. She is a fast cruiser and goes very well in light winds. In strong winds she feels very safe and is fast. The designer measured the following speeds. In 4 knot wind speed it does 3 knots at 45 degrees to the wind. In 12 knots of wind speed it does 7.5 knots at 45 degrees to the wind. On a reach it does 5 knots in 5 knots of wind. He has sailed faster in stronger winds (it has sailed through 40 knot storms) but the design is not a racer. The numbers indicate 10 knot averages would be possible if the total displacement is keep to about 6,500 lbs.

There will be a second item on the structure and build of Nixe which was constructed in Thailand. This will be interesting as its build started 9/8/2012 and they were installing water tanks 11/9/2012. The structure is mainly plywood timber.

The jpegs give the idea. This is a boat that reflects the owner needs well.

 

The “Nixe” pacific proa build is interesting. A 38.7 foot boat that weighs 4,050 lbs that is effectively home designed and built is a good achievement. To commence the build on 8/2/2012 and launch the boat ready to sail on 23/3/2013 is amazing. The proa had a fully finished interior, plumbing and electrical system etc when it was launched.

So how was this short time frame achieved? Start with the build of the main hull. Scarph together a plywood panel that measure 39 x 8 foot of 8 mm plywood with the scarphs 100 mm wide. Do a 2nd 39 x 8 foot plywood panel. Glue sheer clamps to the inside of the ply panels plus a few short stringers on the inside of the panels. Drill holes around the stems and keel lines of the flat plywood panels and tie them together with wire. Cut out bulkheads with slight curves on the sides. Press the bulkheads in to the panels spreading the panels apart at deck level (gunnels) to about 8 foot. Insert temporary deck beams and secondary bulkheads. 3 weeks work so far and a formed hull shape. Epoxy fillet along the keel and stem lines, glass tape the inner keel and stem lines. Inset water tank bulkheads and fillet in and you are at 11/9/2012. Tape the external stems and keel line then start your fit out of internal furniture and shelving, which are the major stiffening and strength components of the overall hull structure. The float hulls were built the same way but used more intermediate bulkheads and less longitudinal shelving. The rudders are 900 x 650 mm on a 50 mm inside diameter stainless steel tubes. The rudder tubes have a deck head tiller which is connected to the steering in the cockpit by aluminium tubes.

The build technique used here is stressform (tortured plywood). Gougeon Brothers built a 10.70 m trimaran with a 7 mm tortured plywood hull so the proa builder up the ply size to 8 mm for a slightly longer and heavier boat. Also, he added more internal ‘framing” by way of increased internal furniture, shelving and eg bunk bottoms etc.

After the internal structure of the main hull was finalised deck beams and the 6 mm cabin roof structure with internal timber beams was built. The internals were then finished with all plumbing and electrics completed. Next came the round hollow wooden birdsmouth mast of 37 foot and 150 mm in diameter at the foot. The bare wooden tube weighed 135 lbs. The mast took one man one month to complete including all fittings. The mast base is offset to the float by 400 mm from the main hull centre line. The mast head “forestay” rigging goes to the bows which gives a “side stay” angle of 9 degrees. The mast is also supported by an aluminium tube that goes from the outer edge of the cockpit to about half way up to the mast.

The cross arms are plywood timber boxes that slot 800 mm into the main hull with a cockpit between the beams next to the main hull.

The proa was basically built by designer/builder, a boat builder and another occasional person depending on the task required to be done. The entire shell was glassed all over and professionally painted. After launch and initial sailing, additional lateral resistance was required for upwind work so the Vector fin was installed which is a good idea as it can be swung up to reduce draft.

This build idea could be used for a smaller (eg 32 foot) proa with a simpler internal fit out that would be a very fast build.

This is a very well thought out design that has proven to be a sound proa over time. It cost about $40,000 US to build and as I said took 13 months from start to build to sailing launch for a complete boat. The jpegs tell part of the story. Good job.

 

Additional Nixe pacific proa build jpegs.

 

I was familiar with Nixe, but never saw the details. I'd call it a good job too. Good design and approach. Thanks for posting that one.

 

The Mahe 36 was a production cat by Fountaine Pajot catamarans with Joubert/Nivelt designed hulls and Olivier Flahault's general layout. Notice, in 2006 the interior/concept is just as important as the hulls/structure requiring its own designer. The Mahe 36 is 36.1 x 19.4 foot and weighs 11,200 lbs and a displacement of 16,400 lbs. The first version (produced from 2007, over 120 of them were built) had a 55 foot mast stiffened by triple half-diamond stays and held up by the forestay and cap shrouds, fitted over twin sweptback spreaders. The roached main sports two full battens, two dual-line slab reefs plus lazyjacks and is 505 square foot. The 320 square foot furling genoa is about 120-percent overlap and there is a Screecher of 560 square foot. The main traveller is controlled from the cockpit, but the mainsheet is led for’ard along the boom then back to one of two dual-speed Harken 40 self-tailers on the cabin top just forward of the helm. The boat has fixed low aspect ratio keels that draw 3.6 foot. The rudders are underslung spades. The hulls have a length to beam of 9 to 1. The underwing is 2 2 foot of the water. This cat was noted for its reasonable performance in a “smaller” size French cat.

The second version from about 2010 had a cockpit roof and other upgrades to improve its comfort without adding any weight due to improved manufacture. The main cabin has 6.2 foot headroom within with little attempt at streamling. The forward windows are almost vertical for interior space and to minimize solar overheating. On deck by the mast, lockers house the anchor windlass and halyard tails. The halyards drop tidily through an aperture in the hatch and are ready when it's time to drop the sails. The water tanks are 265 litres, fuel tanks are 200 litres and waste tanks 50 litres per loo.

The structure in the first version hulls are vacuum-bagged solid glass below the waterline and foam sandwich above. The later version has resin infusion hulls and under wing. Both versions had a resin infusion foam glass cabin top and deck. Interestingly, there are escape/entry hatches fitted well forward on the inside of each hull.

Performance by 2 test crews reported “Off Key Biscayne, with 12 to 15 knots of wind and the roachy main was hoisted and the fractional overlapping jib was unfurled, the boat took off. I'd expected unexceptional performance, but the Mahé went to weather well and topped 9 knots on a close reach. It handled the chop in the Gulf Stream like a much bigger boat, too. I was reluctant to head back into the marina at the end of the day.” The second tester found “Under sail, the boat never missed a tack, which was excellent considering the light and variable winds on test day. In 10 knots true (11.5 apparent) we made 5.5 knots at 70° off the wind. When the wind dropped to 6 knots true (7 apparent) we still bettered 4 knots at 65° off the wind. Add a gennaker or screecher and these figures would have been much higher. Given stronger winds, the boat reportedly moves at up to 11 knots broad-reaching with a standard rig.”

The Mahé 36 appeared to be a fun, comfortable, entry-level cruising cat that the market wanted. Pity it was replaced by bigger “improved” models with more emphasis on accommodation. The jpegs give the idea.

 

After yesterday’s Mahe 36 design from Fountaine Pajot, I present a 2019 model to show the design evolution of modern French multihulls. The Elba 45 sold over 100 cats before the first one even emerged from a mould. The Elba 45 is 44.1 x 24.75 foot that weighs 31,000 lbs and displaces 42,000 lbs. The 60 foot fixed aluminum mast has double diamond stays and there is also an option to have a lighter carbon fibre mast. It has an 807 square foot fathead main and a 527 square foot genoa. There is no self-tacking jib on the cat with Fountaine Pajot saying “We prefer to have a genoa a little bit bigger to have a better-balanced sailing plan.”

Berret-Racoupeau designed the Helia 44 predecessor to the Elba 45. They tested a new range of hull shapes with lower drag. “We reduced drag by 10% and that helps the boat sail better at medium and high speed. Racoupeau explained it managed to make the hull some 15cm longer and 15cm beamier in the process, introducing a small chine in the aft section. “This kind of hull shape will be used on future Fountaine Pajot designs.” The hulls have low aspect ratio keels and underslung rudder.

Fountaine Pajot builds the hull lay-up using a vacuum infusion process with vinylester resin below the waterline and a final coat of epoxy primer under the antifouling. They use polyester and vinylester resin with glass on a core of balsa or PVC foam for the rest of the hulls and decks. Structural bulkheads (balsa sandwich or PVC foam) are made with resin infusion. The rudder blades are made of foam sandwich. The rudder posts are made of stainless steel. The stub keels are mounted by simply gluing them into a deep recess moulded into the hull, so there are no keel bolts to rip out in the event of a grounding or of striking a submerged object.

Now we get to the reason for the new design. Fountaine Pajot found blue water cruisers/charters spent about the 85% of the time at anchor so, the Elba 45 offers big internal accommodation volumes. You may spend a bit more time on passage compared to a more performance-orientated cat, but comfort ensures you’ll barely notice the extra passage time. This boat is about accommodation and to provide that accommodation the boat is 30% heavier than its same size predecessor with a similar size rig. The internal accommodation is self explanatory, please look at the jpegs.

A tester found “The 12 knots of wind encountered during a test seemed favourable to the cat with a rather high displacement. The test boat was equipped with a superb composite sail wardrobe and the cat picks up speed to 6 knots in 10 knots true, at 35 to 38° from the apparent wind. Going by the GPS track and the wake, leeway is low with the shallow skegs. A straightforward turn of the helm through the wind and the Elba 45 was immediately through without ever missing a tack. Coming off the wind the GPS indicated 7.5 knots. The Elba 45 seemed ready to accelerate further but would need more than 10-knot winds. Under certain sea conditions, the rounded bilge at the stern that skims the waterline "slaps" the surface of the water a little, but nothing disturbing.

The Elba 45's polars highlight a preference for points of sail close to having the wind on the beam - nearly 10 knots with 16 knots true and the efficiency of the sail plan with the overlapping genoa, since the gain with gennaker is "only" 0.5 to 1 knot. Note that the asymmetric spinnaker requires 10° more but still offers 0.5 knots of additional speed. Upwind, depending on the wind strength, the best VMG is achieved between 52 and 60° off the true wind.”

Translation, modern designs are about comfort at the expense of some performance. Fountaine Pajot has found space easier to sell than high performance. The cat appears to sail at about 50 to 60% of wind speed under most conditions. The jpegs help to tell the story.

 

We have spoken about monohull foiling sports boats before but the following production boat take our knowledge of foiling, sail control and a person’s ability to sail this boat across an ocean to a new level. The Pogo 3 foiler is a 21.3 x 9.9 foot (with foils retracted) and with foils fully out 17.7 foot. The Pogo 3 weighs 1610 lbs ready to rave without crew or stores. The carbon fibre mast is 39.3 foot high and can carry a 301 square foot mainsail, a jib of 226 square foot, a gennaker of 441 square foot and a spinnaker of 818 square foot. The jpeg of the spreaders show they have a reverse bend in them to allow more headsail area when it was sheeted in for upwind work. The draft is variable but it is a maximum of 6.6 foot. The keel moves from side to side and has controls to vary its depth to keep the bulb at 6.6 foot irrespective of the angle of the keel. The twin T foil rudders are hung from the stern and can be varied in depth and angle of the T foils.

Now we get to the lifting foils. The Mini 6.50 racing rules require a boat to start a race with a maximum beam of 9.9 foot. The foils can go to any beam and angle as long as the drat does not exceed 6.6 foot. Your foils can be any shape. Pogo choose T foils. Now the fun begins. You can vary the side length and vertical angle of the foils. You can also vary the fore and aft angle of the main lifting T foils which varies the angle of incidence of the foil in the water. Get all the foils at the correct angle and you can travel 5 knots faster than just leaving the foils at an “average” position with the same sail settings.

Next, I mention the person sailing the Pogo 3 foiler in a Mini 6.5 transatlantic race single handed. A Mini 6.5 racer has manual controls for all functions. That means you not only have to manually control the sails but also have to adjust the swinging keel but also have to adjust the lifting foils to optimise the boat for each sailing condition. That are 50 individual rope lines ending up in the cockpit and you need to pull the right rope at the right time or the boat can be damaged or broken. Just image what is required to tack the boat. Pogo choose not to have water ballast in the design as it would just be additional work.

Next point if fine adjustments can increase speed by 5 knots you need to be awake as much as possible. So, you are getting about 4 hours per day of broken sleep for 2 to 3 weeks while racing. The result can be sensational, try top speeds of over 20 knots and 245 mile day runs in a 4000 mile race. The Transat is from La Rochelle, France and goes 1350 nm to Las Palmas de Gran Canaria. The sailors expect to arrive after 7 to 10 days in the Canary archipelago. The second leg is from Las Palmas de Gran Canaria and will take from 15 to 20 sailing days to complete the 2700 nm course and reach Le Marin in Martinique, French West Indies.

A tester said “With the log showing 16 knots at 130° off a true wind of 18 knots, the foil whistles, sending spray in the helmsman’s face, but that doesn’t dampen the excitement of sensations that are closest to those of a racing catamaran. The performance and reliability, if not the simplicity, originally sought by the yard are clearly in evidence.” The Pogo 3 foiler 969 shown in the jpegs finished fourth in the 2019 Transatlantic race.

The Pogo 3 foiler is full carbon fibre pvc foam glass build in vinylester resin. The mast is solid carbon fibre in epoxy as are the foils. The jpegs give an idea of the boat. I suspect high performance foiling for an average person is limited to short day sails.

 

Montpellier Languedoc Roussillon is the first ocean sailboat with a real 2 part wing equipped “mainsail” with high lift devices. The rigs performance was astounding and ease to use. Montpellier Languedoc Roussillon was a pacific proa that is 69 x 49.2 foot that weighed 12,320 lbs with the ability to have 3,500 lbs of water ballast in the float. The mast is about 82 foot high and the rig is on a balestron (rig attached a boom that rotates to allow the rig to effectively be close hauled on any heading) with an integral 2 part wing sail mainsail and headsails. The total sail area is 1721 square foot upwind. The length to beam of the hulls are above 20 to 1.

The performance of this proa was very good. How about 8 to 10 knots boat speed in 5 knots of wind, the proa could do 2.2 times true wind speed in winds up to 16/18 knots. That means in moderate conditions it could do over 30 knots. This is America Cup type performance with a rig similar concept rig in a 1986 design and build.

Guy Delage designed the proa for the Montpellier region council in France. The region funded the proa as a promotion for tourism for the region. The Mayor expected immediate racing winning results but like all leading edge designs it took time to develop including a rig failure to overcome. A new mayor was elected and immediately shut down the project. The mayor then ordered the proa destroyed 4 years later prior to the next election so the region would not waste any more money on the project. Politics and boat sponsorship works well in New Zealand but rarely anywhere else.

The proa is a foam sandwich construction in vinylester and Airex foam with fabric and carbon fibre glass. The cross arms are have methacrylate foam (Roycell) in the foam sandwich. The balestron boom (weighs 1100 lbs) is made of carbon fibre, epoxy and honeycomb sandwich. The “solid” covering of the forward wind sail is thin Kevlar component over a carbon mast tube and some bulkheads. The mast head structures to support the second “mainsail” is a solid carbon fibre structure.

The water ballast was automatically adjusted by water pressure and two T- shaped foils to reduce pitching were controlled by the backstay tension.

The jpegs show more of the pacific proa. Please study them as they have may ideas in them. It was a very fast boat well ahead of its time in concept and rig. Well done Guy Delage.

 

The Stiletto 27 was produced from 1976 to 1986 with about 500 produced. The initial standard version first produced was 26.9 x 13.9 foot (that can be compressed to 8 foot for trailering) that weighed 1,100 lbs ready to sail. The cat carried a 35 foot rotating aluminium mast and mainsail of 230 square foot, a jib (genoa) of 159 sq ft and a spinnaker of 750 square foot. The hull length to beam is 11.3 to 1 and the transoms were immersed and wide. The draft of the initial version 4 foot with the central wing based kickup board.

I have spoken about the initial version. Various models of the 27 were produced with most being the Special edition and 6 were the GT version. The GT version was 26.9 x 16 foot that weighed 1725 lbs and carried a 36 foot aluminium mast with a 232 square foot main and 180 square foot mast head genoa with a 120 square foot fractional jib. The daggerboards were now in the hulls. The GT’s were heavier due to improved internal accommodation (carpets and a little internal furniture), wider beam and hull daggerboards. The racers stripped out the internals. By the way Stiletto were successful at marketing, offer a fast racer type boat to many but only about 10% of owners turned up to race the boat.

Stiletto also produced a 23 foot and 30 foot version of the cat. The real issue is what about 5% of the owners did to their boats. They ranged from owners who added higher carbon masts etc for racing to people who used the hulls as a base for a wing deck cruiser.

The accommodation in most versions is two 14 x 2.5 foot long bunks and small bench area. This cat was aimed at sailing or a camp cruiser.

Now we get to the structure. This cat was ahead of its time. Florida-based Force Engineering was build the Stiletto in the late 70s. Forces then marketing director, Larry Tibbe, worked for Ciba-Geigy, which manufactured Nomex etc. Stilettos construction was prepreg epoxy saturated e fiberglass over a Nomex honeycomb core. To cure the prepreg nomex layup, the mold was baked at 250 degrees for 90 minutes. At the same time, the fiberglass skins were vacuum-bagged to the honeycomb to ensure proper adhesion. Most builders vacuum-bagging process is done with a sheet of plastic into the mold and sucking the air out with a single pump. Force Engineering used a blotter to absorb excess resin and 16 spigots to distribute the vacuum, a more effective technique. This resulted in an incredibly strong long lasting hull and deck structure that weighs 0.6 lbs per square foot. Each of the Stiletto 27s hulls weighed only 220 pounds and were impressively stiff. The marketing at boat shows included hitting a hull with a hammer with no damage happening. The initial cross beams were 125 x 6 mm aluminium tubes that slide inside stub tubes in the hulls for 8 foot wide trailing.

Owners say it takes several people (two to four) several hours (three or four). To shrink the beamy (13 feet, 10 inches) Stiletto down to legal highway trailering width (8 feet typically), both the Stilettos crossbeams and the trailer collapse. The compression tube that spans the bows must be removed for trailering, as must the dolphin striker beneath the mast step and the 125-pound bridgedeck.

The Stiletto is a performance catamaran. In a breeze, owners report, is faster than a Hobie 16. Most Stiletto’s have been upgraded with genoas, drifter/reachers, and spinnakers. Many also sport deep reefs and storm jibs, required to keep the boat manageable in a blow. Result the performance of a given boat depends on its upgrades and owner enthusiasm. Some owners claim 20 knot peaks but the cats perform very well in light to medium conditions.

This is the first part of 2 items where we look at the rebooted Stiletto. The jpegs give the idea.

 

The new version of Stiletto was brought to market in 2017 by a new company. The Stiletto X was meant to solve some of the issues of the original Stiletto 27 with “modern materials, rig and foils”. The design was also conceived to more trailable with an integrated system that could expand the cat from 8 foot to 18 foot without having to “assemble” the component parts. The reason for telling you this is because the build company only produced 3 Stiletto X’s prior to significant problems. They expected funding of $12 million and were spending accordingly. Only $1 million arrived, a company in big trouble. The first cat was complete, the other 2 went to a second business for completion. So, I will be giving general numbers, as all 3 boats are slightly different.

The Stiletto X basic was meant to be 30 x 17 foot with a 45 foot rotating mast. The second one (“Cheshire Cat”) was 30 x 18 foot carrying a modified M32 rotating carbon fiber mast 51 foot high with a mainsail of about 450 square foot, a self tacking jib and a gennaker of 500 square foot all in carbon hybrid sail fabrics. The weight and displacements are unknown but a weight under 2000 lbs is likely. The original Stiletto X had hull kick up centre boards and rudders. The second and third cats had curved in hull based daggerboards and cassette rudders installed.

Next problem is the cats build. The first and second cat (‘Cheshire Cat’) hulls and decks were built in the prepreg E-glass and pvc foam. The third Stiletto is a carbon fibre pvc build. The cockpit components were meant to be part of the folding system but each of the X cats have solid carbon fibre box beams fore and aft. The carbon beams are stronger than alloy beams. Aluminium requires about 4 times the mass for equivalent strength to the carbon. The first carbon beam boxes measured 18 feet long with 5.5 mm wall thickness and weigh about 68 pounds out of the mold (design calls for 77lbs with reinforcement and compression tubes). Schedule 40 aluminium would be over 100 lbs per beam. The cockpit components are laminates with PVC cores to make the 3 piece cockpit the center, port and starboard seats. The prodder and rudders are carbon fibre. The curved daggerboards have carbon fibre skins with western red cedar spar cores.

The performance of the 2 Stiletto X cats sailing is good to spectacular. The first standard X cat could approach 20 knots with 8 knot performance in 9 to 10 knot winds. The Cheshire Cat X cat with a wider beam, bigger rig went faster in racing and the numbers indicate a better than wind speed cat in light to moderate wind. The accommodation is limited but a little better than the Stilleto 27. The accommodations includes a “twin berth” in each hull, a head and a sink with shower nozzle and a minimal bench for a galley.

The Stiletto-X was designed with folding beams integrated into the cockpit. As the cockpit lifts up, the beams fold, and the boat slides together on the trailer. This is accomplished in one fluid step under the power of a remote control electric trailer winch. I do not know if it was implemented on any cat.

The jpegs tell more. The black cat is the standard, the blue cat is "Cheshire Cat". Pity the manufacturer did not get into full production, this could have been a serious fun machine.

 

I've seen the third boat I think it's the one in pictures 7 and 8. I think it had curved lifting foils but may not anymore. Cool boat.

 

Scuff mentioned he had seen a third modern version of a Stiletto. The third one has “Price and Quantity” painted on its side. The Stiletto XF is 32.3 x 18.5 foot with a 55 foot carbon fibre rotating mast with 2 diamonds. The mainsail is a “fat square head” with more sail area than the high performance Stiletto X “Cheshire Cat”. “Price and Quantity” has carbon based sail fabrics with a jib, genoa and a gennaker of 500 square foot. The cat initially had in hull curved dagger boards and deep daggerboard rudders in a stern based carbon fibre cassette. The rudder cassette combination can kick up due to a small insert in the sterns.

The cat was based on Stiletto moulds and another firm in June 2018 we took over the build on the Stiletto XF. “Price and Quantity” was designed by Schickler Tagliapietra, who also designed the foiling Gunboat G-4. The main visual difference beside being slightly longer is the red cabin roof area on the hulls. There is no fighter like clear cabin top just a hatch and a small raised roof are to stand up in. The interior is all carbon fibre PVC foam and looks as though it acts as structural components as well. There is minimal “formal accommodation”. The cat is probably designed as a fast day sailor racer with minimal camping accommodation.

The construction is all carbon fibre and PVC foam in epoxy allowing the boat to be light to allow it to ultimately be a full foiler. The carbon beam boxes measured 18 feet long with 5.5 mm wall thickness with the majority of unidirectional carbon fibres intermixed with biaxial carbon fibre for torsional stiffness. The beams are bolted onto the hulls. The cockpit can be and beams can be “assembled” to allow the boat to be transported. Everything is vacuum bagged with either resin infusion or prepreg materials. Sorry, I cannot give more detail as I am working off jpegs and not much written word.

I do not know if the cat went to a full foiler as it has only been sailing for about a year. I suspect this is a wind speed plus type of cat with a good crew. If anyone knows anymore could they please tell us. Chershire Cat and Price and Quantity were upgraded by the same company as you will see in one jpeg. The jpegs tell part of the story.

 

Further jpegs of the Stiletto XF.