Super economical wave piercing catamaran cruisers

[Greenseas2]

In St Thomas there is a fleet of passenger carrying wave piercing catamarans that are owned by Dohm's Water taxi and built by Gold Coast Yachts of St. Croix. The outboard powered work horses are definitely fast with their elongated bows and are inexpensive to operate. The long narrow low friction hulls slice through the waves with ease. The deckhouses on the larger boats are quite spacious and elevated well above the hulls. It doesn't appear that deck space has been sacrificed by the design and the superstructure is only moderately streamlined.

It would appear that the wave piercing catamarans of this particular design would be ideal for long distance live aboard cruisers whose primary focus is on fuel economy. A large version of the wave piercing design may be seen in Key West. It's used for taking passengers out to the Dry Tortugas and is inherently stable. One really great aspect of the design is that it leaves almost no wake at full throttle when operating in what could be considered past-hull-speed in monohulls.

The construction of the boats is composite wood/epoxy and should be well within the building ability of dedicated amateurs. Other than a very futuristic look, I can find no faults with the design and feel that there is a good future use for it with private as well as commercial applications.

[rwatson]

I have had the experience of riding in "wave piercing" commercial catamarans - (developed by Incat in Australia), and one design fault became obvious - the ride motion in fairly calm water at high speed.
I have expressed my opinion in a several threads on boat comfort over the last few months, but in brief they developed the name of "Spew Cats", and lasted only two seasons as ferries in open seas off southern australia.
I and most other passengers got queasy riding them in calm seas because the narrow hulls resulted in lots of 'dipping' as they did indeed slice through long smooth swells. It was like being in the back seat of a car where the suspension is way too soft.
In calmish waters, the ride on conventional hulls with stabilisers is much more agreeable.
I guess in rough seas, everyone gets sick no matter what type of boat, but to get queasy in fine weather is not a great feature.

[Manie B]

Any websites or pics available ???

[tom28571]

I have had the experience of riding in "wave piercing" commercial catamarans - (developed by Incat in Australia), and one design fault became obvious - the ride motion in fairly calm water at high speed.
I have expressed my opinion in a several threads on boat comfort over the last few months, but in brief they developed the name of "Spew Cats", and lasted only two seasons as ferries in open seas off southern australia.
I and most other passengers got queasy riding them in calm seas because the narrow hulls resulted in lots of 'dipping' as they did indeed slice through long smooth swells. It was like being in the back seat of a car where the suspension is way too soft.
In calmish waters, the ride on conventional hulls with stabilisers is much more agreeable.
I guess in rough seas, everyone gets sick no matter what type of boat, but to get queasy in fine weather is not a great feature.

The ride in sea swells in a big cat at speed can make passengers run for their barf bags. I did not get sick on two recent 130 mile trips across the English Channel on the "vomit comet" but some did. These do not have wave piercer bows. They seem to handle waves much better than the long period swells. The Key West cats are far smaller and might actually be easier on the passengers.

[SeaSpark]

A super economical boat will never go really fast, does anyone have experience on a wave piercing cat at lower speeds, say lower than or only a bit above the hull speed of a displacement boat at the same length?

[Fanie]

Reading Rwatson's post on this I can only agree with him. If the hull's don't move right with the water then you are going to get seasick, that's a given.

Super piercing hulls go through waves, often with the oposite motion (or not obvious or predicted motion). Me, I'll just stick to something that moves right. Besides, what's the fun going to be when there's no motion ? Aint that called 'land' ?

[rwatson]

"does anyone have experience on a wave piercing cat at lower speeds"

I can tell you about wave piercing hull performance at moderate speeds, based on a 20 ft trimaran.
I built the centre hull with a really fine entry, and when powered by a 6hp outboard, it was a real joy at around 10 knots. The wave piercing meant that in short uncomfortable chops, the boat wasnt knocked around like traditional runabouts. It stayed wonderfully level and comfortable. Being a trimaran, fishing was great, as the small swells didnt make the boat rock badly at anchor, which had been the bane of many fishermen in the 'standard' fishing boat.

[Greenseas2]

Ive ridden both the Key West wave piercer in rough weather and the Dohm's boat in St. Thomas and didn't experience adverse motion on either. I also had an opportunity to discuss economy of operation with the crews and found out that fuel consumption was less than half of an equivalent monohull. The drift of the thread is more toward speed and economical cruising in relatively protected waters. Of course, we can all introduce extremes that could make seasoned mariners heave their cookies. The economy of operation of a wave piercer would make it an ideal long distance cruiser on the ICW. It also has good load carrying capability.

[rwatson]

Do note however, I was complaining about SMOOTH weather operations.
My observations were that under autopilot, the small course corrections (say every 3 -5 minutes) were done by increasing pressure from one or other of the twin waterjets. This caused the accellerated hull to dip - giving the very uncomfortable feeling of being in a car whose driver was accellerating and turning the wheel every 3 minutes - most puke provoking.
They would have done better to have some sort of small rudder/trim tab to do the small course corrections I think.
In rough weather, all boats are the pits!

[SaltOntheBrain]

Hey Geenseas,
When I lived down there, one of those water taxi's hit a big wave on the south shore of St. John. It blew the windows out and scattered debris all over the place.

Here's my opinion: Those boats are fantastic for what they were designed for, which is a smooth ride in confused chop up to three or four foot wave height, but that bridge deck is an un-aero-hydro-dynamic wall not meant to meet big waves head-on.

Guys, when he called them fast, he's only talking about 20 knots or so, which is a lot higher than displacement speed, and is a pretty good rate of travel in the chop we saw most days down there.

I grew up fishing the Texas Coast, and when I moved down there, I never could figure how to time the waves in my little boat, I was always getting beat up and tired. Then I watched the water from a plane one day and notices a cross-hatch wave pattern. Waves came from two directions. From the SE (Caribbean) and from the NE( Atlantic). It was brutal in a small monohull, but those Gold Coast cats ate it up.

I just don't think they'd make a good cruising boat in the open ocean.

Lance.

[kengrome]

In St Thomas there is a fleet of passenger carrying wave piercing catamarans that are owned by Dohm's Water taxi and built by Gold Coast Yachts of St. Croix.I was curious about the appearance of these boats and no one posted any pix so I did a google search and came up with these:

http://www.watertaxi-vi.com/images/boat01l.jpg

http://www.watertaxi-vi.com/images/dwt3a.jpg


There are bigger pictures here: http://www.watertaxi-vi.com

A super economical boat will never go really fast ...I'm not sure what you mean by "really fast" SeaSpark, but according to Malcolm Tennant displacement catamarans can be as fast as planing boats. Tennant claims that as size increases the cost to make the boat plane becomes prohibitive, so he says larger displacement catamarans can be as fast as a planing hulls, but a lot less costly to reach these speeds. This is probably an over-simplification so I point you to the article he wrote since it explains better than I can:

http://www.catamarans.com/news/2006/04/CatComparison.asp

The economy of operation of a wave piercer would make it an ideal long distance cruiser on the ICW. It also has good load carrying capability.I'm thinking the same thing. I am hoping to take a trip on the ICW and do the Great Loop in a few years, in my own boat that I have built in my my little shop in the Philippines, and I'm interested in these boats because of their cruising economy ... and their spaciousness.

Boats like these might actually serve as decent ferries for shuttling people in between islands in the Philippines, although the typical Philippine 'banca ferry' seems to be relatively efficient at this task already. Here's a picture of one that appears to be enclosed, or perhaps only semi-enclosed:

http://www.imagesphilippines.com/images/011603_122918.jpg

But bancas are not "high-tech" enough for the rest of the world, whereas the super-efficient catamarans used by Dohm's Water Taxi just might be.

Guys, when he called them fast, he's only talking about 20 knots or so ...For me, 20 knots or so is plenty fast enough for most everything I would ever want or need in a cruising boat.

[masalai]

Ken, I am still researching, but have a look in my gallery. There is several pictures of a 10 metre Robin Chamberlin design which had 2 x 50 hp kubuto engines and did 16 knots for a 12 knot cruise getting near 1 litre/mile.

John is building a 12 m version in Brisbane now. I hope to see it before it goes to the buyer... should be ready in a couple of months....

Robin now lives in Tasmania (I think??)

[kengrome]

Hi Malasai,

The Chamberlain boat certainly looks efficient with those very slim hulls!

There's a new design I'm interested in investigating further, it is called "Derby Gravel Truck" (DGT) and it's from a little known designer by the name of Jeff Gilbert, a Kiwi who lives and works in Australia. Jeff's boat is smaller, and although it is designed for efficiency he has also given it a very desirable safety feature:

Derby Gravel Truck is a genuine SELF-RIGHTING catamaran!

I guess he figured that if he could design a self-righting cruising power catamaran he will have accomplished something no one else in the world has managed to do. He gets his efficiency from the catamaran design of course, but it could be said that the proper classification for this boat is a motor sailer since he also specifies twin "downwind sails" to help with efficiency whenever the boat is moving in the right direction, which theoreticlaly should be at least half the time, right?

Here's a preliminary sketch, which as you can see is particularly 'rustic' in terms of its appearance. Personally I very much enjoy seeing boats designed to look like real old fashioned working boats, rather than the high-tech 'space ships' that so many designers are producing these days:

http://www.boatdesign.net/gallery/data/500/medium/dgt.jpg

Note that Jeff has nothing more than the premininary sketches of this boat at the moment. The plans are probably a year off or more since he is finishing his last year of "real employment" this year, after which he intends to devote full time to his boat design work.

Fortunately Jeff is very proficient at designing with the actual materials in mind. What I mean by this is that he considers every piece that goes into the boat and tries to design for the efficient and economical use of materials -- to keep the actual building costs as low as possible so that "less than wealthy" retirees can afford his boats.

Here are the rest of his sketches:

http://www.boatdesign.net/gallery/data/500/medium/dgt2.jpg

http://www.boatdesign.net/gallery/data/500/medium/dgt3.jpg

http://www.boatdesign.net/gallery/data/500/medium/dgt4.jpg

That's the grand total of all the images he has made public at this point in time. I have them in my gallery in case anyone wants to see larger views. Sorry for going off-topic here, I'll stop now so the conversation can continue on wave-piercing hulls ... :)

[masalai]

It is still "wave piercing"... Thanks for the other offer too...

[kengrome]

It is still "wave piercing"...I guess my idea of piercing is when the entire forward section of the hull gets completely immersed in water. I would call Jeff's boat (and most other catamaran hulls) wave slicing rather than wave piercing. Then again, I guess it's just an issue of the size of the waves that determine whether or not a hull is piercing or slicing them at any particular time ...

[masalai]

Thanks Ken, Mainly a legitimising ploy - "staying on thread?:D"

[kengrome]

Thanks Ken, Mainly a legitimising ploy - "staying on thread?:D"Good move, thanks for keeping me on-topic!

I often see these threads drifting on and off topic. I would create a new thread for the Derby Gravel Truck if the plans were finished, or if it were my goal to discuss the boat further. But right now they are not and I am not. I only wanted to mention the boat in passing at this time, in case others might find it interesting.

I think the DGT is a boat worthy of future discussions, and after Jeff finishes the plans I'm hoping to build one, assuming I still have the same interest in the design then as now. That's the time when it 'makes sense' to give the boat it's own thread ... :)

I posted the pix in my own boatdesign.net gallery yesterday and already someone has emailed me to ask me if plans are available. This is probably why Jeff has posted the pix only in his [jgbuilders] Yahoo group -- so he would not have to respond to numerous inquiries from others until he actually has the plans finished and ready for sale.

[masalai]

Ken, you are always welcome to use "Grumpy...." thread (saves me looking all around:D)

[warren mosler]

This is my boat:

http://pmyeditors.blogspot.com/2008/01/is-it-finally-happening-are-power.html

Be happy to discuss with anyone interested.

Currently at Goldcoast here in St. Croix nearing completion. I took it out several times before some of the systems were in place (head, generator, etc.) with excellent results.

Didn't notice any high speed calm water issues cruising at 24 kts burning under 15 gph apart from some spray from the bows misting the upper deck.

No spray at 20kts or less, and the leading edges of the bows are now being 'sharpened' to reduce drag and spray some, and an upper helm windshield is being installed as well.

[masalai]

Warren, How will you go in the following "challenge"? http://www.icecat.com.au/trial.htm - at the bottom of this page. This boat has achieved http://www.icecat.com.au/summary.htm a pretty impressive performance - fuel economy wise.

I reckon with current technology, 800 ml per nautical mile is do-able for a vessel capable of travelling 2,500 miles non-stop at around 12 to 15 knots. as per the "challenge criteria". How will yours go?

[warren mosler]

Hi!

Notes taken during the first sea trial show 3 gallons per hour at 10 kts (which looks like about 1 litre per mile?) and a max range of just under 2,500 miles with full tanks (600 gallons).

The conditions were pretty rough, 20+ kt winds, 6-8 ft seas, etc, so should be a touch better in calmer conditions?

Also, the sharpened bows should help a tad?

Weight should be about the same as a large pile of mechanics tools gets replaced by an upscale but lighweight interior trim package.

There was also about 200 gallons of fuel aboard (max is 600 gallons) and 10 of us aboard.

At 15 kts fuel burn doubled to about 6 gal. per hour so that means a max range of about 1,800 miles.

Not sure what the refueling rules are?

Looks close to or better than the Icecat design?

Also, with twin 190 hp vs twin 100 hp diesels and a higher bridge deck height above the water I can crank it up and cruise at 25kts all day into 6 ft seas as needed?

I also have two helms, 3 queen berths, and relaxed seating for 20 outside, and about the same inside.

Last, seems the beam on Icecat is wide enough for some uncomfortable 'snap roll?' Goldcoast kept mine down to 17 ft. to minimize it for passenger comfort.

[Greenseas2]

The design of the cats in St. Thomas are interesting and time tested for reliability. As mentioned in the first part of the thread, the design is for a long distance WP cruiser and one that would be the most efficient in fuel consumption and designed for ICW or waters of moderate wave conditions. It is assumed that a long distance cruiser would probably only be carrying 2 to 4 people at most. The goal here is to design the wave peircing cat cruiser that has a non-refueling range that would take it from Key West to New York. 1200 statute miles. Of all interesting hull designs, it is believed that a wave piercing cat has the best chance of doing the task with the least amount of fuel and at "reasonable" speeds. We aren't looking for engines in the hundreds of horsepower, but lesser hp with more efficient engines.....possibly a diesel outboard. With today's high fuel prices that continually move higher, hull and power plant efficiency are becoming more crucial for those who want to cruise, but are limited to a normal family budget. The end goal is for a wave piercing cat that can accommodate a max of 4 people in relative comfort and burn approximately 200 gallons of fuel for the 1,200 trip at a max of around 18 to 20 knots and leave no wake. Rather than spend big bucks on a preliminary design, building a large model first would be the best and least expensive method to achieve, "proof of concept" with a design. YOUR THOUGHTS?

[warren mosler]

My boat both fits that deiscription and more. Fuel efficiency won't increase with a lower hp diesel, unless the package is lighter, and the 190 hp Volvo d3 package with stern drive is only about 750 lbs per engine. Lesser hp doesn't mean more efficient, for all practical purposes. And the (composite) stern drive means no rudder and minimal underwater drag, and the blades tilt out of the water for overnighting.

It's perfect for 2-4 people, as the unused berths make for welcome, massive storage useful on long trips.

It can make the 1,200 mile trip on a 600 gallon tankful at 25 kts, and about half a tank at 'cruiser' slower speeds.

And virtually no wake at any speed.

Draft is under 2 ft, and the legs 'kick up' if they hit anything.

[Greenseas2]

Your boat is really great and performs well, but I hate to think of what one like it would cost. Definitely not for the home builder of course, but still close to what we're looking for.

[kach22i]

Some nice pictures in the links of this thread.

Look for them in the Random Picture thread.

[warren mosler]

I think the basic boat can be had for about $500,000, but it's easy to spend more than double that on electronics, fancy lighting, appliances, fancy paint, interior trim, high end fixtures, teak decking, etc. etc. etc. etc. etc. etc....

Another nice feature I forgot to mention is the main cabin a/c is a roof top 110v (about 1.8 kw) Seamax RV type unit that costs about $900. With the shades down it readily cools the whole cabin and the cold air also quickly works it's way to the lower berths.

Goldcoast sells the basic 'ferry' for about $450,000 with 225 hp outboards, with a single helm, single head, commercial white paint, etc. The D3 diesels shouldn't add more than about 25,000.

[Greenseas2]

Thanks Warren for the cost data. I suspected that the ferries would be in that price range. Gold Coast is a leader in the field of wave piercing cats that is close enough to be able to see some of their boats. I believe that what I'm really looking for is construction drawings for the less affluent to be able to build their own wave piercing cats from Gold Coast licensed drawings. A half of a million dollars is significantly above the price that most people can pay, but there is a lot of boat building talent out there that can do the job for a fraction of Gold Coast costs. A construction drawing package at reasonable cost may be a product that Gold Coast may want to develop to supplement income and, of course, as more people build the cats, input on innovations would benefit Gold Coast. Just early morning thoughts over coffee.

[BMcF]

I guess my idea of piercing is when the entire forward section of the hull gets completely immersed in water. I would call Jeff's boat (and most other catamaran hulls) wave slicing rather than wave piercing. Then again, I guess it's just an issue of the size of the waves that determine whether or not a hull is piercing or slicing them at any particular time ...

The fundamental problem with 'wave piercing' hull designs is that the reduced water plane and volume (what allows them to 'pierce' waves under some conditions) is also what contributes to two things that have given them, particularly the larger ones, their bad motion sickness characteristics:

1. Natural period of pitch is reduced compared to a stiffer hull form. Humans are most susceptible in terms of seasickness to periods in the 8-10-second range.

2. Damping is less..so when the wavepiercing hulls are operating in wave conditions where pitch resonance is excited..the pitch amplitudes are larger than those for a stiffer hull.

For most wavepiercers, their most spectacular 'piercing' behavior is observed when resonant pitching ultimately results in stuffing the bow violently and deeply in the the face of a wave. The consequences of such an event have been noted in an earlier post. On the other hand, I've always had a soft spot for wavepiercing cats..if it were not for those, we may never had been prodded to develop such elaborate and expensive active stablization systems in the early 90's that are the norm now on virtually all passenger carrying wavepiercers over 50m that were ever built.:D

[warren mosler]

two things.

yes, plans are available from Goldcoast. Not sure but probably in the $5,000 range. But that's just a guess.

second:

"For most wavepiercers, their most spectacular 'piercing' behavior is observed when resonant pitching ultimately results in stuffing the bow violently and deeply in the the face of a wave."

This is minimized on mine by having the bows shaped such that they can accelerate vertically with minimal drag, and also the upper bow is extended some and also shaped to provide lift as needed, as well as better protect the windshield.

Also, speed is a big factor. When going into tight, 10 ft head seas a month or so ago with several passengers, at 14 kts i was splashing and slapping some but not enough to do any damage. Slowing to 10 kts took away all the drama. By quartering rather than going straight into the waves 20 kts wasn't any problem, with no slamming or slapping, though a coffee mug would have sloshed the coffee all over the place.

We took 20 people, including several kids under age 10, home from St. John in 8 ft seas quartering all the way with a good time had by all and no one got sick on the two hour ride at 18- 20 kts.

A few weeks later in 3-5 ft head seas/chop, I was able to maintain the 24kt cruise speed without any drama and good stability.

Attached is a picture taken during construction and a computer generated model done before the design was finalized.

[yacht371]

A 45 foot wave piercer I designed a couple of years ago.

Grahame Shannon
Avia Design Group

[warren mosler]

Nice looking design!

A few comments-

Tops of lower bows look flat which will limit upward acceleration if they bury into a wave?

Upper bow far enough forward to come into contact with waves relatively quickly?

Looks like clearance over the water is relatively low limiting performance through waves over a few feet?

Looks like it would be fine in calm water at modest speeds?

[yacht371]

The design is preliminary only, although we have done some model testing.

The hull is almost a trimaran, with the central hull quite close to the water, but it has a very deep vee angle and is intended to contact big waves and provide reserve buoyancy.

After some experience with power and sailing cats of various types, any that have a bridge deck at all (as opposed to an open space with netting) will eventually slam when the wave height reaches a critical level. Up to that point they ride better than a monohull, often dramatically so, but once the bridge deck starts to slam, the ride rapidly worsens.

This design will actually start to slam sooner than a flat high bridge deck, but the ride will not deteriorate so suddenly. It will be able to continue in reasonable comfort at a slower speed in worse conditions than a more conventional shape.

Disadvantages? Expensive to build, the forward protruding bows can throw up spray in some conditions. We tried a similar concept without the forward protruding bows on the Motorcat 29 produced in Poland. The ride is very smooth until the waves get over about 4 feet (steep short ones, not long swells) then you must slow right down. Still in tests we did 20 knots into seas that had monohulls 10' longer turning for home.

The bigger the size of the boat, the better all this works. All I need is well heeled clients!

A 36' concept similar to the MC29 is below.

Grahame Shannon

[masalai]

yacht371, That looks like it is designed to fit in a standard marina berth. Have a look at the SharkCats and PowerCats - production designs developed for use offshore of the Australian Gold Coast, so as to be able to tend the shark nets set of the beaches to "protect the swimmers". Up to about 28 ft could not be surpassed and would do in ANY weather/seas, up to 40knots with twin outboards. They became a popular choice for the volunteer rescue services and sometimes as an adjunct to surf lifesaving operations of occasion...

They are highly regarded by those who need all weather short haul (200 miles or less) capability.

[Greenseas2]

When we address the design restrictions on a wave piercing cat, the most significant operational restriction is wave slap to the underside of the deck. Recently we tried a variety of WP cat designs for a major ship for the USMC and USN to be built after 2010. Testing was done at the Carderock USN test tank in Maryland. The vessel sign called for operations in seas state 3 and be able to straddle a pier for self loading/unloading with internal hoists.

In addressing larger wave piercing cats, wave slap has to be considered and it is generally found that this feature limits the height of the seas in which a WP cat can operate. Also, when considering wave piercing cats, different docking arrangements are in order other than slip width. As mentioned above, larger wave piercing cats for passenger or cargo carrying make good use of a pier that they can straddle and load/unload either through inner hull doors or from hatches in the under deck. Primary considerations of design are operating sea state conditions, economy of operation, speed (mostly moderate) and docking arrangement. The straddle-the-pier arrangement offers ease of handling passengers or a self loading capability, with no need of passenger "jet-way" type ramps or external gantry cranes and associated equipment.

[kengrome]

We aren't looking for engines in the hundreds of horsepower, but lesser hp with more efficient engines.....possibly a diesel outboard.Since there's no such thing as a diesel outboard, how about a 4 stroke gasoline powered outboard? They simplify things a great deal and they are easy to work on and replace as needed. Besides, most Americans have far less 'fear' of outboards than inboards.

The end goal is for a wave piercing cat that can accommodate a max of 4 people in relative comfort and burn approximately 200 gallons of fuel for the 1,200 trip at a max of around 18 to 20 knots and leave no wake.Good concept. What's your target retail price? What type of construction is preferred ... or accetable? Do you plan to build them in the USA or have them built overseas and ship them to the USA?

[masalai]

Since there's no such thing as a diesel outboard, how about a 4 stroke gasoline powered outboard?

I understand Yanmar make one rated at 27 hp, but it appears a bit dated & heavy however I believe there is other diesel outboards being developed?...

"retractable" electric legs with the motor at the bottom (propeller end) are being developed by "AfricanCats" for their hybrid sailing cats - by the address somewhere in Northern Europe... this link GREEN MOTION Retractable Drive System 31-05-2007 (http://www.africancats.com/resources/documents/PRESS_GreenMotion_ENG1467.pdf) at this site http://www.africancats.com/

[kengrome]

I understand Yanmar make one rated at 27 hp, but it appears a bit dated & heavy however I believe there is other diesel outboards being developed?Well, Yanmar used to make them, but they were apparently so costly and unpopular -- or possibly problematic -- that they discontinued them with no plans for re-introducing them.

[Greenseas2]

Actually the are two manufacturers of diesel outboards that still offer them Yamaha is one (rather than Yanmar) and China Diesel Imports in Jotul, California is the other. The reason that Yamaha isn't in the united States is that the engines don't meet US environmental standards. This, by the way, is also the reason that European diesel autombiles that represent a high percentage of sales in Europe aren't in the US.

In addressing diesel versus 4 cycle gassers, there are few, if any, gas engines that have the fuel economy of a diesel. Also, due to much higher torque, the diesel engines support a significantly larger prop than gas engines. In discussing design for a wave piercing cat, we're looking at a fairly large cruiser where engine weight of the outboard is a secondary consideration, but range is primary. In essence, the over all economy is a package that includes nfactors such as hull design and power plant efficiency. Another train of thought is the use of internal diesel generators with twin electric propulsion motors mounted in the hull. Food for thought.

[kach22i]

... this link GREEN MOTION Retractable Drive System 31-05-2007 (http://www.africancats.com/resources/documents/PRESS_GreenMotion_ENG1467.pdf) at this site http://www.africancats.com/
Cool link, great idea.

[rambat]

I think this new design will fit into the thread, we are showcasing a new 66' Swath type yacht that can ballast up to transit as a catamaran/wave piercer. We have had the test model running for several years and now have styled it for the up-market. like the GPH efficiency's discussed here, it is remarkable:

TOTAL FUEL OPTIONAL TANKAGE MILES/GAL(8KNOTS) RANGE(8KNOTS) MILES/GAL(20KNOTS) RANGE(20KNOTS)
250 BASE 3 750 1.5 375
570 320 3 1710 1.5 855
820 250 3 2460 1.5 1230

NOTES
1. FUEL TRANSFER SYSTEM REQUIRED WITH OPTIONAL TANKAGE
2. TESTS WERE TAKEN UNDER GOOD CONDITIONS

The new topside looks have been well received and most yachts magazines have showcased it in the last two months, that's a good sign it may not be too odd looking for the target market. That seems to be the challenge for many twin hull design of late. Running picture of the test bed and new design render attached.

[Greenseas2]

I'm rather surprised that the sponsons aren't totally enclosed . In a relatively high chop with water coming over the tops of the hulls, there would be 6 areas for water to impact and act as resistance whereas if they were enclosed, the water would simply flow down the sides. The designs are beautiful and as far as public acceptance goes, I sincerely believe that the public is ready for new and fresh designs as long as the designs represent greatly enhanced economy of operation. One suggestion though, being that hull speed is determined by the square root of the waterline length, it may be worthwhile extending the hulls further forward.

[rambat]

Our speed is limited by too small of waterjets right now, however the hull will project farther on the new design for more recovery buoyancy. The hulls are up only when running as a cat in smooth condition, otherwise the boat is better in Swath model when seas are rough.

[Pericles]

A coincidence, but the Ax Bow being discussed elsewhere on this forum is also a wave piercer with the added benefit of not being deeply immersed in waves.

Here's the article. Pages 5 & 6.

http://www.hiswasymposium.com/pdf/2006/J.%20Gelling.pdf

Pericles