The Adastra has a length/beam ratio (main hull) of 17:1 - this is extreme by any measure. But with a length of 42.5 m (over 139'), she still has plenty of room - not the same amount as other mega yachts her length, but more than the average trawler yacht.
Of more interest, is her efficiency at displacement speed - she burns 29 liters/hour (7-2/3 GPH) at 10.5 knots resulting in 1.37 NM/Gallon. This is "real" trawler economy and is her intended speed for ocean voyaging. Her top speed is 23 knots at over 8X the fuel consumption or 62 GPH. As a comparison, Island Pilot builds a 57', 60,000#, monohull that burns 8.4 GPH at 8.9 knots (we're both going slower and burning more than a 139 footer!!!) and at 30 knots, 66 GPH. These are apples and oranges - but interesting numbers.
John Shuttleworth Yacht Designs Ltd.
Island Pilot 535
A Kadey-Krogen 48' with a single 200 HP Deere at 9.1 knots is burning 6 GPH or 1.5 NM/Gallon, a bit better than Adastra at 10.5 knots. Of course, if you slow down the KKY, she'll get better mileage, as I am sure you would with Adastra, too. But to say that this 139 footer is NOT economical at displacement speeds is incorrect. The entire design project was based on making her as efficient as possible for long hauls with a modest amount of top speed. Kadey-Krogen 48' AE
Regarding these long, thin, outrigger-stabilized monohulls (or trimarans, if you must) - the ones designed for off shore voyaging, seem to do fine. Earth Race (one of the photos posted) circled the globe in record time in 2008. Earth Race, renamed Ady Gil, was rammed by a Japanese ship and became a total loss.
My interest in this type of craft is to create one for the pleasure boater who is shopping for a 30 something, economical, coastal cruiser (Great Loop, East Coast, Bahamas, etc.). I am working on a design that has not dissimilar proportions as Adastra except for overall size, luxury and price - the goal is a trailerable boat that has a base price in the low $200s with super economical cruising at 6 knots and economical cruising at 12 knots. One reason for steering towards this type is single propulsion machinery keeping installations as simple as possible, making up in length what we lose from beam.
The current design is hovering at 12m (39'6") with a waterline beam of 3'0" - If we can bring the waterline beam down to 28", we will be close to Adastra's 17:1 lenth/beam ratio, a good goal. Beam across the outriggers (amas), is at 15'0" - not too beamy to fit in many slips. Since the accommodations are long and lean (width of interior is 7'0"), we will end up with similar spaces as a typical monohull thirty or so feet long - and since boats are priced like steak (you pay by the pound), we expect pricing to be similar, too. If possible, we'll have 2, stand-up cabins (one queen & one twin) - one in the bow and one in the stern with a deck house between and an exterior bridge/sun deck aft (over one of the staterooms).
We built a 1/4 scale model and towed it at speeds up to the equivalent of 12 knots, full-size. Our 6 knot cruise was to our expectation using 6 kW/8 HP - with a modern diesel, we would expect 12 NMPG. At 12 knots, we see 65 kW/86 HP - 2.5 NM/Gallon. (See video of model being towed.)
To keep the price competitive, we are thinking of offering her with a variety of propulsion packages and are considering the following:
1. Single outboard
2. Small diesel for displacement speeds only - maybe 30 HP?
3. Plug-in electric power - 10-15 kW with 4 hours battery
4. 110 HP modern, computer-controlled diesel
5. Parallel Hybrid - 13 kW electric with 110 HP diesel (as above)
6. Serial Hybrid - 10-15 kW motor with variable-speed DC generator
7. Solar option - PV array for charging the battery - any of the above
8. Wind option - Wind turbine for charging the battery - ditto
All the electric drive/hybrid options would include a sizeable Lithium battery at 48 VDC.
Like Maltese feels there's a market for his efficient 52 foot cat, I feel there's a market for a smaller, ultra efficient cruiser with a price to match.
The outriggers (amas) are designed to be retractable for both trailering and for world-wide shipping in a standard 40' shipping container.