Boat construction

A demountable catamaran assembly includes a pair of cockpit-equipped, kayak-type canoe hulls laterally joined in spaced-apart relationship by the frame of a trampoline. Longitudinally spaced pairs of tabernacles on the two hulls removably receive four depending spigot components on the trampoline frame to maintain the assembly of the pair of hulls while a further tabernacle on the trampoline frame removably receives a sail mast.

This invention relates to boats, and more particularly to a system in which 
a boat hull is enabled to be converted from a manually-propelled vessel to 
a sailing vessel, and in which two such boat hulls may be joined together 
so as to constitute a catamaran. 
Canoes and catamarans have a common origin; canoes today are generally 
narrow-beamed craft, usually manually propelled by paddles rather than 
oars or sculls and have developed from the simple "dug-out", and the 
dug-out with laced-on side planks, through birchbark canoes, Eskimo 
"kayaks" and "umiaks", old Celtic skin-covered "curraghs", to the oceanic 
"proa", "lakatoi" and "pirogue". 
In the Indian and Pacific Oceans, the basic canoe was given one or two 
outriggers and eventually evolved into the great double-canoe of the 
Polynesians, which were ocean-going sailing vessels perhaps 120-160 feet 
long and providing ample living accommodation aboard. Unlike the 
coast-hugging longships of the Vikings, these double-canoes were capable 
of voyaging over thousands of miles in the Pacific Ocean. 
Today the simple canoe and its descendant the catamaran are sharply 
demarcated. (The word "catamaran" is derived from a Tamil word meaning "a 
bundle of logs"). 
At the present time, one can buy a canoe of the open kind, or of the 
turtle-decked kayak kind having one or two cockpits. Such a craft is 
generally limited to use in such bodies of water as rivers or lakes, and 
perhaps very sheltered bays, as it does not have a keel or centreboard, 
nor does it possess a rudder. Admittedly, such a canoe is usually fairly 
inexpensive but, not being a specialized competition craft, fails to 
inspire the adult boat-lover after its newness has worn off. 
From the simple and inexpensive canoe, the would-be sailor looks to a 
sailing vessel and has to make a choice between keelboats and catamarans 
(sailboards are akin to surfboards rather than to sailing boats and 
attract a quite different kind of "afficionado"). Keelboats and catamarans 
having a cost within the reach of the average buyer--most often a young 
adult--are almost invariably suited for day-long sailing only, having no 
cargo stowage space to permit protracted voyages. Examples of such "day 
out" keelboats are the various sailing dinghies, V.J.'s, Eighteen-foot 
skiffs and the like. Affordable catamarans include the "Hobie" type, "surf 
cats", "hydra cats" and the racing catamarans, all of which have no cargo 
space in their extremely narrow-beamed "plank-on-edge" hulls, which may 
actually be solid. 
From the above it will be realised that a need undoubtedly exists for a 
deep-water craft which is initially inexpensive and takes the basic form 
of a boat hull which can be converted from a simply, manually-propelled 
vessel to a sailboat, and which can be joined to a second such boat hull 
so as to constitute a catamaran. 
The present invention has as an object the fulfilling of this need in a 
relatively inexpensive and eminently practical manner and thus consists 
broadly in a demountable catamaran comprising a first kayak-type canoe 
hull, a second kayak-type canoe hull and a trampoline removably adapted to 
span and space-apart said hulls: each said hull having a spaced-apart pair 
of cockpits arranged in tandem; a pair of tabernacles one located forward 
of and the other located aft of said tandem cockpits, each tabernacle 
being adapted to receive removably therein an elongated spigot component 
substantially normally to the water-line of said hull; said trampoline 
having a rectangular frame provided with four depending elongated spigot 
components each adapted to be removably received in a said tabernacle; a 
further tabernacle mounted upon a forward cross-member of said trampoline 
frame; a mast, the butt-end of which is removably receivable in either (a) 
said further tabernacle or (b) said forward tabernacle of a said hull; and 
a sail for said mast. 
Preferably, each one of the kayak-type canoe hulls has a pair of 
water-tight cargo stowage holds, one located forward of and the other 
located aft of the said pair of tabernacles. Advantageously, each hull may 
also have a pair of buoyancy compartments, one located forward of and the 
other located aft of the said pair of cargo stowage holds, each buoyancy 
compartment being filled with flotation material. 
Each hull may well have, located substantially amidships, a fin-box adapted 
to removably receive therein a keel member, and each hull is preferably 
provided with a rudder which, when a canoe hull is used singly, is 
operable from the aft tandem cockpit but which is also capable of being 
coupled to its neighbouring rudder and operated by tiller means when the 
vessel is in its catamaran configuration. 
Ideally, each of the cargo stowage holds is provided with a screw hatch 
arrangement at its top centre; and above each hold may be a recessed deck 
load bay. 
In a further aspect, the present invention may consist in a waterborne 
vessel capable of being operated in any one of three modes, the first mode 
being as a manually-propelled canoe, the second mode being as a keeled 
sailing canoe and the third mode being as a catamaran; the waterborne 
vessel comprising a first moulded fibreglass kayak-type canoe hull, a 
second moulded fibreglass kayak-type canoe hull and a trampoline adapted 
to removably span and space-apart the hulls: each hull having a 
spaced-apart pair of cockpits arranged in tandem; a pair of tabernacles, 
one located forward of and the other located aft of the tandem cockpits, 
each tabernacle being adapted to removably receive therein an elongated 
spigot component, substantially normally to the water-line of the hull; a 
pair of water-tight cargo stowage holds, one located forward of and the 
other located aft of the pair of tabernacles, each cargo stowage hold 
being provided with a screw access hatch arrangement at the top centre 
thereof, there being a recessed deck load bay above each hold; a pair of 
buoyancy compartments, one located forward of and the other located aft of 
the pair of cargo stowage holds, each buoyancy compartment being filled 
with flotation material; a fin-box adapted to removably receive therein a 
keel member; and a rudder which, when the vessel is used in the second 
mode, is operable from the aft tandem cockpit and which is capable of 
being coupled to its neighbouring rudder and operated by tiller means when 
the vessel is used in the third mode; said trampoline having a rectangular 
frame provided with four depending, elongated spigot components each 
adapted to be removably received in a said tabernacle when the vessel is 
used in the third mode, a further tabernacle mounted upon a forward 
cross-member of the trampoline frame; a mast, the butt-end of which 
constitutes an elongated spigot component and is removable receivable in 
either the further tabernacle when the vessel is used in the third mode or 
in a said forward tabernacle of a said hull when the vessel is used in the 
second mode; and a sail for the mast.

In these Figures of the drawings, like integers are referenced by the same 
numerals throughout. 
FIGS. 1, 2 and 5 show the basic canoe hull, that is to say, both the first 
and second kayak-type canoe hulls. This basic kayak-type canoe hull may be 
a moulded fibreglass, 5.3 meter, tandem-cockpit, turtle-decked canoe of 
beamy proportions having a maximum beam amidships of perhaps 0.88 meter. 
FIGS. 1, 2 and also FIG. 6 illustrate the basic canoe hull accoutred to 
constitute a keeled sailing canoe, while FIGS. 3, 4 and 7 show the mode in 
which a first and a second moulded fibreglass kayak-type canoe hull may 
constitute a sailing catamaran. 
The drawings show such a kayak-type canoe hull 1 having spaced-apart 
cockpits 2, 3 arranged in tandem. Located forward and aft of these tandem 
cockpits 2 and 3 are a pair of "tabernacles", that is to say, sockets in 
which may be stepped such structures as a mast butt or other elongated 
spigot component. The illustrated canoe hull is of substantially 
V-section--to be best seen in FIG. 4--and has sheer fore and aft. 
Fore and aft of tabernacles 4 and 5, respectively, are the water-tight 
cargo stowage holds 6 and 7, each of which is provided with a screw access 
hatch arrangement 8, 9 at its respective top centre. 
Above each cargo stowage hold 6, 7 is a deck load bay, respectively 10, 11, 
which is recessed into the turtle deck and may be surrounded by a raised 
coaming or cofferdam, each sufficient to accommodate, say, a 75 liter 
capacity back-pack when fully loaded or, perhaps, tents and/or other trek 
equipment. Chainplates 12 are provided on each deck load bay for the 
securing of deck-borne loads. The watertight cargo stowage holds 6 and 7 
are eminently suitable for the stowage of such items as food, drink, 
clothing, etc., and also sails and rigging for the conversion of 
manually-propelled canoe to keeled sailing canoe. 
At bow and stern of the moulded fibreglass kayak-type canoe hull are 
buoyancy compartments 13 and 14 (see FIG. 1) when are filled with a 
recommended flotation material to accord with the International Standard 
Draft code for canoes and other small craft. 
Each cargo stowage hold 6, 7 is fitted with a drain plug, 15 and 16 
respectively, while from the bilges, a drain tunnel 17 passes through 
stern buoyancy compartment 14 to open into an outlet at the sternpost of 
the craft, this outlet being closable by a plug 18. Each cockpit 2, 3 is 
equipped with a one-piece moulded fibreglass seat, 19 and 20 respectively, 
contoured so as to allow the user to assume a relaxed posture while 
correctly supporting the back and legs in comfort over protracted periods 
of time. At bow and stern are the anchored-in rope carrying-handles 21 and 
22 which enable the vessel to be carried quite easily by two persons, and 
the craft is light enough to be hefted onto the roof rack of a passenger 
motor vehicle; there is also a bow-eye 23 to which may be belayed a 
painter or the like. Substantially amidships on the turtleback deck, a 
compass binnacle 24 may be mounted between cockpits 2 and 3, and at the 
stern is a pintle-post for the shipping of a rudder, later to be described 
herein. 
Referring now again to FIGS. 1 and 2 in conjunction with FIG. 6, the basic 
canoe hull 1 can be seen to be converted into an efficient and seaworthy 
sailboat. In this mode a 30-40 mm diameter aluminium mast 25 is stepped in 
forward tabernacle 4 in which it may be secured by a keyway and large 
set-screw working in a collar, the butt-end of mast 25 constituting an 
elongated spigot set into the keelson. Mast 25 is stayed by a pair of 
shrouds 26, 27, and a forestay 28, these being secured to shroud eye-bolts 
29, 30 and forestay fitting 31 all of which are bolted to the turtleback 
deck. The craft is cat-rigged with a single battened sail 32. However, 
alternative rigs such as, for example, a dipping lugsail, are considered 
suitable. 
Set into a fin-box 33, substantially amidships, is a demountable keel 34 
which may be of moulded fibreglass, polyurethane or other suitable 
material and hung on the stern pintle-post is an aluminium rudder bracket 
35 between the bifurcate limbs of which is affixed a rudder 36 of the 
shape illustrated. Rudder 36 may be of moulded fibreglass, polyurethane or 
other suitable material and it permits the craft to be brought into the 
wind very rapidly to prevent the vessel turning turtle in squally 
conditions. The rudder 36 may be actuated from aft tandem cockpit 2 
through the agency of a cross-arm 37 on rudder bracket 35, cables 38 and 
39, and foot control 40 in the aft cockpit. Thus, as will be realized, 
these are somewhat akin to simple basic aircraft controls. When the craft 
is operated in the keelboat mode, the canoe paddles, such as 41, are 
stowed in suitable clips affixed in the turtleback deck, these not being 
shown in FIG. 6 for reasons of clarity. The craft as described above has 
an exceptionally low centre of gravity to impart great stability while 
paddling or sailing the craft, and the hull design and geometry also 
provide stability during entry to and egress from the craft while on the 
water. The craft has virtually unmatched seaworthiness and safety factors. 
Attention is now drawn to FIGS. 3, 4 and 7 which depict an inventive 
catamaran comprising two basic, moulded fibreglass kayak-type canoe 
hulls--such as that previously referenced 1--joined parallelly together. 
This joining together of the hulls is brought about by way of a 
"trampoline", generally referenced 42, which has a rectangular frame 41' 
to which is laced the usual "deck" 43. The trampoline frame is provided 
with four depending, elongated spigot components 42' each adapted to be 
removably received in one of the four tabernacles of the two hulls, so 
that the trampoline spans and spaces-apart the hulls, the spigots being 
secured in the tabernacles by such means as a keyway and a large set-screw 
working in a collar. The mast previously referenced 25 is, in this mode, 
stepped in a further tabernacle 44 mounted upon the forward cross-member 
45 of the trampoline frame and is stayed by the shrouds 26, 27 and a 
divided forestay 46. Here again, the sail 32 may be a battened cat-rig 
sail. 
In the catamaran mode, steering is achieved by coupling the rudders 36 
through primary tillers 47, 48; coupling link 49 and inboard tiller means 
50. 
The catamaran configuration is able to handle almost any type of open and 
closed waters (sea, rivers, lakes, bays etc.). Sail or paddle may be used, 
depending on conditions. Good vision allows the crew to paddle or sail the 
craft at a brisk rate even against tides and head winds. The twin keels 
and the particular shape of the rudders give the crew full control under 
all sea and river conditions. Two adults are easily able to carry the 
catamaran by using the side members of the trampoline frame as handholds. 
As will be appreciated, the craft of the present invention provides 
virtually maintenance-free, low cost boating for a sole operator or a 
small group. Of great advantage is the fact that the craft may be 
purchased in stages, firstly the basic hull for use as a canoe, then the 
mast, sail, rigging and rudder, and finally a second hull and trampoline. 
From the abovegoing, the reader will realise that craft built in accordance 
with the present invention provide the public with a new or much-improved 
article or, at the very least, offer to it a useful and attractive choice. 
The claims defining the invention are as follows: