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Entry #6

TRIMARAN

drawings - stats - boat - budget - explanation - bio

Drawings:

Stats:

LOA 5.6 m (18' 8") (w/o rudder)
LWL 5.3 m (17' 8")
Beam (Main Hull) 1 m (3' 4")
Beam (total) 2.40 m (8')
Height 3 m (10')
weight (empty) 120 kg
Loading capacity 340 kg
Draft (leeboards/rudder up) 15 cm (6")
Draft (leeboards down) 53 cm (1 ' 9")
Freeboard (fully loaded) 30 cm (1')
Total sail area 7.2 m2 (80 square feet)
Main 5.6 m2 (61 sq. ft)
Mizzen 2.6 m2 (29 sq.ft.)
Power 2 HP air cooled outboard

Boat:

Studying the report of Keith Drury, and considering the tight financial and temporal frame, it becomes clear that the voyage asks for flexibility. You'll probably need to make progress in any conditions in order to make it within the 90 days, in bad weather, in rapids and lakes with big waves and wind. There my be unforeseen events like boat repair, lack of fuel or engine problems etc.

My answer to this is a small and lightweight canoe with two floats linked to the main hull by means of platforms. This gives the canoe the needed stability and safety, plus enough living space.

The boat is flexible in terms of propulsion - it can be paddled, sailed or driven by the outboard. The long narrow hull has minimal water resistance, and the floats are mounted a bit higher, so that they barely touch the water in upright position. The floats can be made from glassed styrofoam or plywood. The main hull is glassed on the outside - two layers of 3 ounces/m2 fabric on the bilge panels and bottom.

Sailing

The boat has two short masts with Gunther batwing sails and sprit booms. The total sail area is about 7 square meters and each of the floats provides 130 kg lift - together with the beam of 2,4 m (8'), this means that the boat can sail unreefed up to about 4 Bft. It has two leeboards that are mounted to a shaft that hangs under the platforms, just as in my folding tri (see Duckworks article). The leeboards can be built massively with sink weights or hollow with a combination of rubber and rigid lines holding them in place.

The rudder is built as kick-up rudder with sink weight, as usually in Michalak designs (not visible in the 3D model). It is operated by means of lines that are linked to two pedals.

Motor

The outboard is mounted offset in front of the rear seat for a better weight trim (note that the outboard mount does not need to be as massive inside the hull as shown in the pictures - the model is a 3D equivalent of a sketch and therefore not to be mistaken as detailed design). It is fixed as the boat is steered only by means of the rudder.

Keith Drury writes that the silt in the Missouri will sooner or later destroy the water pump. Therefore I would buy the air-cooled Honda BF2D 4-stroke engine with 2hp. It has a very low fuel consumption, I read about 0.85 l/hour. Using it during the whole voyage, and making an average 4 knots (70% of the hull speed), you have about 660 operating hours and thus need 560 l (160 gallons) of fuel. I think the engine will burn more fuel in bad conditions, but probably a big part of the journey is made by paddle and/or sail, simply because that's how you will enjoy the trip much more. By the way, in calm conditions one horsepower should push the boat (920 lbs total, 17 feet waterline) at a speed of 4.7 knots according to a diagram in an old Michalak article about electric boating. (A rough estimation, of course, but the pointed canoe hull with a length-beam ratio of 5.6 is particularly efficient).

Accomodation

Flexibility is also provided in terms of accomodation. In nice weather, you may want to sit in the open air, then the open middle section is the "saloon", with the platforms serving as seat benches and a cockpit table mounted to the main mast.

To travel in bad weather, you mount the deck tent over a tube between the masts so that it lies flat on the platforms and raises just enough to provide sitting headroom in the middle section. So the helmsman can still look over the tent and the other one can sleep or read or just relax in the protected 200 x 100 cm space (6' 8" x 3' 4").

A second "tent" can be mounted over the raised mizzen sprit boom to protect the helmsman - the main sprit boom is then mounted to the transom transversally.

If things are really bad and you want to decrease air resistance to a minimum, you can lower the tent to the platform level and still have very basic shelter for a couple.

When you've anchored or pulled the boat ashore, you can mount the deck tent at full height and thus get a spacious cabin with standing headroom in the middle and two 200 x 70 cm berths with sitting headroom on the platforms (6' 8" x 2' 4"). On windy days, the foretent mounted between the deck tent and the bow makes the front more aerodynamic. It is open at the lower side, which gives dry access to the river. However, the main tent can be completely closed to keep the mosquitoes outside.

To make these many configurations possible, several strips of hook and loop tape are sewn on the tent and glued to the corresponding areas of the hull/platforms. The tent is made from heavy polytarp and the sews are sealed with adhesive tape.

Transport and Portages

The boat can be disassembled for transport - the crossbeams are pushed through openings in the main hull and bolted to the bulkheads. The platforms with the glued-on floats are screwed to the crossbeams and the main hull with drywall screws. After assembly some (removable) sealant should be passed over any gaps and the screws.

At the dams I would try to get a ride, as Keith Drury recommends. But to be on the safe side, build a primitive boat cart consisting of a (wooden) double-T profile with 20" wheels at both sides. The "board" is simply strapped under the main hull a bit aft of the middle.

If necessary, boat and gear will be transported separately. The boat can even be disassembled until only the main hull with about 80 kg is left.

Budget:

Financial Budget

plywood 10 sheets 50$ 500
lumber 100
Epoxy, glass, styrofoam 300
paint 200
polytarp for sail and tents 200
other building materials 175
Wheels for boat cart 100
foam for platform/berth matresses 50
Outboard Honda BF2D or BF2.3 750
600 l fuel (170 gallons) 300
3 fuel tanks (3 gallons each) 45
2 water tanks, 5 gallons each 30
used GPS 100
anchor, 10 m chain and 20 m rope 100
more ropes 50
2 life jackets 100
watertight bags/containers 100
top lantern, 12V battery 100
solar panel for charging battery 150
food/supplies 1500
maps 50
Total US$ 5000

Weight

boat 120
motor 13
tents 6
berth foams 4
anchor & chain 7
battery 10
paddles 4
water 30
fuel 36
food 20
sleeping bags 6
clothes, other equipment 36
cooking equipment 4
boat cart 10
life jackets 4
crew 150
total kg 460

Explanation:

Financial Budget

The boat is built in stitch and glue from a light 5 or 6 mm plywood - preferrably pine. The total net area of plywood needed is 21.5 square meters, that is 10 sheets are needed. Pine or fir lumber is used for framing and the cross beams. The lumber budget also includes smaller pieces of a heavy 16 mm plywood for the rudder, motor mount and cockpit table. (assuming the leeboards are profiled hollow construction from two 5 mm layers).

25 square meters of glass are needed for the bottom and the floats - about 100$ here in Europe. You'll need about 10 litres of Epoxy and hardener, that is another 100$. Then you need some styrofoam and blue foam for the floats and the inner parts of the platform sandwiches - another 100$ will do easily.

The paint is exterior latex - the bottom is glassed anyway. For Tents and sails you buy 40 square metres of polytarp for about 120$ and double sided adhesive tape and hook and loop tape for 80$.

"Other building materials" means glue, bolts, drywall screws, cable tiers, brushes, rubber gloves etc.

The boat cart wheels probably will come from a junkyard. The foam for the berths can also come from some unconventional source - or you buy two air matresses and repair kits.

The outboard should definitively be purchased new for the sake of reliability, fuel economy and low noise. Probably you won't need as much fuel as listed. I don't know the US fuel prices, but I assume it's about 1.75 $ a gallon. If it's more expansive you'll need to paddle a bit more. The fuel and water tanks are plastic, light and cheap.

The GPS and maps are important as you can't afford getting lost on the lakes. I think a used GPS should be available for 100$ or less.

The 4kg anchor has a chain forerunner of 10 meters. Maybe that is exaggerated for a river trip, but on a windy day it can save your boat. As for rope, I would try to get at least 20 m of 10 mm rope and about the same length of 6 mm line.

The watertight bags/containers play an important role as they provide additional lift if the boat should get swamped or leak, if tied firmly to the hull.

A top lantern is probably necessary in the parts of the river where you encounter substantial commercial traffic. Therefore, you also need a battery and a small solar panel to charge it. However I don't expect the lantern is used frequently - at night you'll probably look for a secure place in shallow water.

All this leaves 1500 dollars for food and other travel supplies.

Weight Budget

The total weight of the boat should not exceed 460 kg. By the way, all heavy items like anchor, battery, water and fuel are stored in front of the middle section to ensure a proper trim.

Bio:

Horst Werner

I'm a mechanical engineer and have been reading about boat design as a hobby since 1998. I've built a 4.70 m folding tri of my own design in stitch and glue (and written a Duckworks article about it) and participated in two earlier Duckworks design contests. I use a self-written design system ("Ligo") for modeling and calculations. Today I work as a software developer.

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