review of my other website discussion "Motor/Sailing Design"
written back in 2001, one paragraph jumps out at me, "The modern
catamaran motorsailer is blessed with such a dramatic improvement
in performance, that I have chosen to redesignate it 'Motor/Sailer'
to differentiate, and yet emphasize its motoring and sailing capabilities.
Those expedition yacht seekers of today should give serious consideration
to this type, and take a look at what's coming in future motor/sailers."
now want to present one of those future designs!
At the core of this new motorsailor design is an innovative new
sailing rig known as the DynaRig. The DynaRig concept was developed
in Germany in the 1960s, as a propulsion alternative for commercial
ships in the face of a looming energy crisis. When the crisis actually
materialized in the early 1970s, further refinement and some testing
followed, but no DynaShips were built and the idea eventually went
into the archives. Recently a resourceful and inventive gentleman,
Tom Perkins, has taken this technology to a higher plateau and built
a full size 'proof-of-concept' vessel, the 290 foot sailing yacht,
Maltese Falcon *
DynaRig is a modern version of a 'square-rigger', but here the yards
(yardarms/horizontal spars) do not swing around the fixed mast,
but rather are attached permanently to the mast which is allowed
to rotate to engage the wind angles. This requirement for a rotating
mast precludes the old traditional staying of the mast, and results
in a 'free-standing design'. Only recent developments in very hi-tech
materials such as carbon fiber have permitted this DynaRig technology
to be become reality.
German research had determined the optimum arc for the square-rigger's
yardarms & sails to be effective pointing to windward. This
12.5-degree arc was reconfirmed by the Maltese Falcon design team.
Much like the old square-rigs the total sail area on one mast is divided into rectangular panel sections 'stacked' on top of one another. Even the old names designating the different sails have been retained; the Courses on the bottom, then the Topsails, the Gallants, and finally the Royals. The individual rectangular panels can be
sized proportionately to account for the desired sail area to be
deployed for various wind conditions. Naturally the upper sails
that can exert more overturning forces are smaller in size. I've
chosen to make the 'courses' smaller than the 'gallants' for storm
purposes. But I kept the yardarms of the 3 lower sails all the same
length for manufacturing reasons.
interestingly the overall profile of this sail plan almost perfectly
matches that of the idealized semi-ellipital/parabolic planform
shape. The lift/drag factors for this optimized shape are so much
superior to those for the triangular sail-shapes of the Bermuda
Sailmakers was employed to test and build the sails for Maltese
Falcon. They discovered that when angled efficiently the square
sails suffer very low loading due to the very extensive 'square
edge support' provided by the yardarms. "In 50 knots of wind
no more than 900kg loading was measured, tiny compared with leech
loads on far smaller 'conventional' rigs." So simple Dacron
can be used to good effect, in fact only 4 oz cloth in most of MF's
multihull vessels (particularly catamarans) experience difficulties
keeping an 'aerofoil-shape' or 'flying shape' to their sails in
light-wind conditions. But with light-weight sail cloth stretched
between horizontal yardarms, the flying shapes can be better maintained.
Even in heavier conditions the flying shapes will remain almost
this DynaRig is done progressively from the top down. On Maltese
Falcon it was found that the 'royals' themselves (those right at
the top) accounted for 40% of the loads on the rig, and with those
furled her angle of heel reduced dramatically. The overturning moments
on our Dyna-rigged multihull should act accordingly. It might surprise
you that the 'royals' on Maltese Falcon are constructed of remarkably
light 2 oz Dacron, and are "effectively sacrificed in 80 knots
of wind." In other words, it will allow 'blow-out protection'
in microbursts and/or unseen severe squalls.
all the way down leaves just the 'course' sails flying. It has a
very low CE at this stage, and like all of the other reefed configurations,
it remains a 'balanced' sail plan. The course sail still presents
a sizable sail area for really heavy-air storm conditions. An ultimate
storm trysail arrangement is contemplated where the luff of this
sail would ride in a slotted track mounted onto the rear facing
outside wall of the mast tube, and then sheeted to the boat.
there is the possibility of two 'crow's nests' on the upper yardarms
whose visibility would depend upon the stage of reefing employed.
That slotted track for the trysail could be complimented with another,
and the pair could provide a guideway for an 'elevator ride' to
the crow's nest(s) with the help of an electric winch.
Maltese Falcon the sails roller-furl into a cavity in the body of
the mast. I believe there is a design variation that will avoid
this very extra complication, while concurrently allowing for a
sealed mast tube.
quick motions are very tough on a free-standing mast. Multihulls
are particularly guilty of providing sharp, quick motions that are
exacerbated the further from the motion center you are. To alleviate
some of the extra loading on the support structure of the free-standing
mast, there are some 'staying' possibilities envisioned. As the
mast only needs to rotate thru 130 degrees for sailing purposes,
it's very possible to utilize a full time 'fixed' backstay. More
intriguing is 'special running backstay' that could ease loading
on the base support, as well as bending in the mast section itself.
A 'removable/detachable' forestay for heavy pitching conditions
can also be accommodated, and this might well be capable of carrying
a roller-furled reacher sail as well. (Special note: there are no
backstays or rigging in the cockpit area to interfere with big game
Layout & Profile Accommodations Drawing
(click to enlarge)
DynaRig mast does not exert big compression loads to its base, but
it does require considerable bending and torque support. This is
provided by the X-structure formed by the athwartships 'spaceframe'
bulkhead, and the longitudinal 'backbone rib' nacelle/front-frame
combination. The 'bury' of the mast is approx 7 feet
a foot more than that deemed necessary by the free-standing Aero-rig
manufacturers. The 'spaceframe' bulkhead is patterned after Shuttleworth's
FEA research on an Aero-Rig catamaran design. Carbon rib-arches
incorporated into the cabin top are also envisioned.
automation is anticipated, but expected to be quite a bit less complicated
than that of Maltese Falcon. Single-handed sailing is a reality.
The auto-winching associated with sail handling will be done electrically,
and might require less hardware than on MF. The mast rotation gear
is accessible and located in a big compartment at the front of the
rig in its 'bare' state still represents a lot of windage. In a
storm, or at anchor, this sizable windage factor located forward
of the CLR of the vessel could cause the bows to be pushed off the
wind to some considerable degree. For this reason the 'radar arch'
has been fashioned bigger than would seem necessary to act as a
stabilizer at the rear. It's ironic that this arch is there at all,
as I swore a long time ago I did not like these things! I've tried
to keep the 'flybridge' control station's
drag at a minimum by utilizing a 'podium type' console, and a simple canvas top cover.
To compliment this futuristic DynaRig sailing rig, I offer a couple
of innovative solutions to the motor power options. I will cover
these in an outline form, and more completely in the "Power
Rim-Driven Propellers: Instead of propulsion blades being attached
to a central hub and propeller shaft, they are rooted to the rotating
inner rim of a circular nozzle type unit. The rim is electrically
driven with a permanent magnet motor, where the motor windings are
in the stator and where the rotor has a number of permanent magnets.
The electric motor is an integral part of the 'propeller nozzle'.
These units are cutting edge technology. First came the rim-driven
thrusters, and very soon the rim-driven propulsers.
There are lots of pluses to recommend this new technology:
diameter than prop counterpart at equal power densities
be tucked close under the hull skin for less draft and more keel
constraints as to location as with shafted props
can be located
away from transom pitching
unit can be contained in its own 'waterbox', & accessible,
& serviceable without hauling the vessel
mounting would allow for partial retractability in shallow waters
retraction under sail.
susceptible to fouling lines
safer for divers and marine life
reduction and direction gearboxes required, instant fwd/reverse
maneuverability, joy-stick operable (gamefishing plus, plus)
Diesel-Electric Powerplants: The rim drive units are electrically
driven, so they would require some portion of the latest technologies
associated with the ever expanding 'diesel/electric propulsion'
power generating units preclude the need for additional
fewer engines required onboard.
vessel could be powered by versatile options:
1 single big main-unit
2 equal-size units
2 unequal size units, for a high or low power need
- Considerable amounts of electric power would be available for all auxiliary equipments onboard, as well as for sail winching & furling operations
Conventional Propeller Drive: For those clients concerned about
the new diesel-electric technologies, there are several conventional
Long slender hulls are a key factor to efficiency of the catamaran
vessel. This is usually expressed as a 'slenderness ratio'. It is
best that this slenderness ratio not slip below 12-to-1, even for
present two offerings here:
displacement semi-circular bottoms of the more traditional multihull
type offer better sailing attributes, but provide less volume
for 'cruising amenities' and load carrying capabilities. Approx
modified Malcolm Tennant (CS) 'canoe-stern' type hull will tack
slower, but carry a bigger load. Approx 48-50.000 lbs.
CS hull form is depicted with an outdrive-leg propulsion unit.
Alternatively, this could be a rim-drive unit, or even a conventional
shafted- prop arrangement exiting the 'canoe area' of the hull
per existing designs.
hull types would make use of an 'anti-squat' lip at the stern,
akin to a built-in trim tab.
Hull, Chain Drive
(click to enlarge)
ITEMS of note:
is a nacelle structure down the centerline of the vessel that
acts as a bottom truss member, acts as a wave splitter, and provides
a mounting for two asymmetric centerboards, thus eliminating any
daggerboard or centerboard penetrations into the main hulls. And
cables, bearings, boards are all above the load
serviceable in remote areas.
central portion of the aft deck can be lowered to the sea level.
This might be advantageous to the fisherman or for family entertainment
is a dedicated outdoor cooking/galley area for true 'outdoor living'
are two possible crow's nest on the mast at the second and third
yardarm locations. These might be serviced by an 'electric lift'.
just a little bit more mast rotation, the lower yardarm can be
utilized as a crane to launch and retrieve the yacht's tender(s)
to be stored at the bow location. In many cruising locations your
tender assumes the role of your car, so having two onboard is
very convenient when there is a group of people aboard. I have
designed a custom RIB that would survive this bow location, and
offer significant other features of performance and carrying capacity.
could be a real fuel-sipping machine requiring less fuel weight
to haul and propel around, or seek out in remote locations. Demonstrated
savings can reach 30-50%.
sail she could make 18/20 kts
under power 18-25 kts. Range
could skim over depths as little as 4'. Explore those rivers, mangroves,
coves, lagoons. Dive or fish the flats and the reefs from the Bahamas
to the Pacific atolls.
could be the ultimate MotorSailer