might ask, how could I introduce a monohull description with a multihull
symbol? Well, my monohull had twin keels.
I was working on the original aft-rig concept, I was also intrigued
with the idea of homogenizing Bruce King's very successful twin
daggerboard, SORC race boat design with the British twin keel cruising
boat concepts. The 50' world cruiser,"Bluebird of Thorne",
became my base model. I drew up my idea of a real blue water cruising
monohull which made use of my mast-aft sailing rig. The twin keels
offered the similar shallow draft exploration features of the multihulls,
and the vessel could be beached in remote areas for cleaning the
bottom and/or work on the prop, rudder, thru-hulls, etc.
to the use of symmetrical twin keels as popularized by Westerly,
my design utilized asymmetrical foil keels which were placed at
a 3 degree angle to the fore/aft centerline of the vessel. The asymmetrical
foil shape was more efficient per square foot of keel area at developing
the leeway reducing forces, thus the total wetted surface area could
be reduced. The 3 degree toe-in was used to avoid the vessel having
to crab sideways to its intended direction in order to develop any
lift at all (symmetrical foils must be driven at some angle of attack
in order to develop lift). The asymmetry and the pre-set angle of
attack would act to significantly reduce the 6 to 12 degree leeway
experienced by conventional symmetric-keeled vessels.
combination of the foil shape and the skewed angle of attack was
accomplished with very little increase in total frontal area projection
over a traditional single fat-foil keel. The two keels were attached
to the hull such that as one became vertical upon heeling, the other
assumed a more horizontal attitude and contributed to the righting
stability of the vessel.
the mast-aft rig's absence of a conventional mainsail imposed less
leeway inducing forces so that the keel's surface areas could be
reduced (extra wetted surface area was always recognized as a nemesis
of twin-keeled vessels). The outer ends of both keels were tipped
with small end-plates which further contributed to their efficiency
,and acted as grounding plates. And the overall lower center of
effort of this sail plan allowed for less voluminous keels (less
single-masted ketch configuration, with all roller furling, meant
a sailing couple could handle up to a 70' version, and without having
to leave the cockpit/saloon house cocoon in nasty weather.