Alien
https://drive.google.com/folderview?id=0B4fhfAcL5OlNLTZ5SUdCUk1Ta0k&usp=sharing
Alien
Proa Concept
Design Goals:
Fast Lake Michigan Crossings
Simple construction method
Full flotation
The design goal is to create a low cost, high performance proa for fast Lake Michigan crossings to Chicago. This is an 80 mile crossing, with typical conditions 6 foot waves and 20 mph winds. During frequent thunderstorms, conditions can increase to 15 foot waves and 50 mph winds.
This is a main hull designed to replace a sharpie hull on the existing Whaleback proa. Outrigger beams will likely pass through the hull through shafts under the seats. Alternatively, arched outrigger beams will be constructed.
Construction is ¼” exterior plywood, sheathed with 6 oz. glass and epoxy outside, coated with epoxy inside. All external chines are glassed with heavier cloth. All compartments except the cabin are filled with vertical sheets of construction insulation foam. The foam is placed so as to support the cabin floor. The foam is put tightly in place, then cut with a hot wire to fit the hull panels. Internal joints are glued with PL Premium Polyurethane or similar.
The main hull length is 23’-2” with two 36” rudders for a full length of 29’-2”. The maximum hull width is 28”. There are 8” wide (nominal) box ends in the main hull formed by 2’x8’ fir boards. There are two barn door rudders at each end, similar to the Kia Kia proa design. The rudder swing is away from the outrigger float , with a limited swing toward the outrigger float. Rudders are attached by galvanized barn door hinges. The rudders will be controlled by fir 2”x3” tillers angled to windward that move near the outboard end of the sidecar. There will be pole extensions to allow steering from within the cabin, with clamps to lock the pole extension in place when the rudder is in steering mode. There will be stop brackets on the outrigger booms which receive the tillers to lock the rudder in the neutral position when the rudder is at the bow.
Steering oars/sweeps will be stowed in a ready to use position for close quarters maneuvering and for situations where the barn door rudders are not able to turn the boat to wind.
The bottom vee section is 12” in height and is filled with construction foam. The cabin floor is at the top of the bottom vee section and this panel extends from end to end of the main hull. An alternative would be to build a water tank for approximately 30 to 40 gallons in the center of the bottom vee section. The forward and aft flotation chambers are filled with construction foam.
A sidecar will be built to allow for helming outside the cabin. A sit on top kayak will be lashed to supports on the lee side of the hull to provide buoyancy if knocked down.
The boat is a shunting proa with an oceanic lateen sail and rig. The mast will have a base plate riding on a rail and will be pulled fore and aft with a continuous line to allow shunting from within the cabin or in the sidecar.
The bottom vee section is 12” in height, with a panel width maximum of 18.5”. The cabin sides are 29” in height from keel to deck (not including windshield). The cabin and vee sides together should be able to be cut from one section of plywood butt scarfed to 4’ x 24’. The windshield is 18” high, with a side dropboard leading to the sidecar and two cabintop hatches.
A 2hp 4 cycle outboard motor on a sled will provide harbor power and will be used in low wind conditions.
The seating is made of removable ½” plywood panels supported by cleats on the cabin sides. There will be upright and reclining options. Seats will be removable for laying on floor (this requires moving the outrigger booms toward the hull ends).
Why not just build the bottom straight out of foam and fiberglass over it?
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not a bad idea… hmmm
a round bottom would be faster than a vee
There are two barn door rudders at each end, similar to the Kia Kia proa design. The rudder swing is away from the outrigger float , with a limited swing toward the outrigger float. Rudders are attached by galvanized barn door hinges.
Two things, first I think a boat intended to go fast should have as high a prismatic coefficient as possible which means that the ends (and rudders) need to be fatter.
Second, if the ends are fatter the ‘base’ of the rudders will wider which makes it possible to hinge them up ‘figure 8 style’ either with spectra type small rope or fab something up with regular hinges, probably would take 8 hinges per end at a minimum.
Cheers,
Skip
It would be nice to have rudders that hinge both ways. The only reason I dare to propose a one way rudder is that the builder of Kia Kia found them “highly satisfactory”.
It would be nice to have rudders that hinge both ways. The only reason I dare to propose a one way rudder is that the builder of Kia Kia found them “highly satisfactory”.
Am out on the road with just a laptop and no drawing facilities but maybe I can describe the thing. Take a pair of hinges and connect a leaf of each with a strut so that the distance between barrels equals the width of the inner rudder face. Make 4 for one rudder assembly. For lower pivot connect one leaf to starboard hull, the other to port rudder. Repeat in opposite direction, port hull to starboard rudder. Do the same for upper pivot.
Hope that makes sense, should work well for trailing rudder, for leading rudder to steer a socket like arrangement like on the Broomstick might be better.
Cheers,
Skip