This won't work for QUIDNON, which is to be assembled barn-raising style on some sheltered bit of coastline in a few summer weekends by people who have never built a boat before, and, if all goes well, never will build a boat again, boatbuilding being entirely incidental to the far more interesting activities of living aboard a boat and sailing it around.
Therefore, QUIDNON will arrive at the construction site in the form of a set of shipping pallets loaded with all of the parts pre-made. The kit of parts from which the hull is assembled will consist of a large set of plywood panels, milled out using an excessively precise numerically controlled machine. Each piece will be numbered, and each assembly step documented in a printed assembly manual.
The usual technique for assembling plywood-and-fiberglass hulls is to screw the plywood pieces to a light wooden frame using countersunk stainless steel screws while simultaneously gluing them in place with epoxy. After assembly, the joints are filleted using a bead of epoxy loaded with a special filleting compound. This is the so-called “screw and glue” method, and is known to result in a durable, long-lasting hull.
The choice of stainless steel is a compromise: stainless steel is not really stainless, and starts to rust as soon as it is deprived of oxygen. A layer of surface oxide called passivation is what gives it its stainless properties. It is unknown how well stainless steel fasteners fare when encapsulated inside a sealed wooden hull, where there is always the possibility that bacterial action will create an anoxic environment. Ideally, there would be enough osmosis happening, with water molecules migrating in from the outside and evaporating from the inside, and enough oxygen molecules would be carried along with the water to keep the stainless steel passivated. A safer choice would be to use bronze screws, but the cost of bronze is exorbitant.
Another, even better, and very cheap alternative is to use no metal fasteners at all. Instead, the plywood pieces are fitted together using a system of tabs and slots, all of them precision-milled using an NC machine. In instances where there is the possibility of making a mistake in assembly by choosing the wrong part, the joints are keyed using a unique combination of tabs and slots, making it physically impossible to assemble the hull incorrectly. The pieces are assembled in a certain sequence, which is made obvious by the consecutive numbering of the parts. After assembly, the joints are saturated with epoxy, then filleted to fill any minor voids and to bring each joint up to its maximum strength.
Several types of joints will be used.
- The simplest is the box joint: the edges of two pieces are made with complementary tabs, which mesh together in a rectangular zigzag pattern. This joint is used to join the bottom with the sides of the hull, and the transom, as well as in a lot of interior carpentry.
- Similar to it is the tab-and-slot joint: instead of teeth, one of the two pieces is made with slots that the tabs fit into. This joint is used to join the deck with the sheer clamp (the strip that goes all around the deck and is variously known as rail, or rubrail, or inwale, or gunwale, or bulwarks). In the case of QUIDNON, the sheer clamp has quite a number of duties: below deck, it is perforated by a row of holes for the deadlights that admit light into the cabin, covered on the outside by a strip of polycarbonate plastic; above deck, it holds scuppers that drain the deck and admit dock lines.
- Next is the zipper joint, which makes two pieces that are within the same plane act as one, by providing good strength under both tension and compression. This joint is used to join the sheer clamp to the sides, and to assemble the deck, the sides, the bottom and the transom out of separate panels.
- Next, it is sometimes necessary to have some tabs slide inside slots. Certain pieces of cabinetry need to be pre-assembled before being slotted into one panel while sliding in slots in another. Unmodified, this technique leaves voids, because the slots are longer than the tabs, and voids are a problem: they are hard to fully saturate with epoxy, can fill with water, get infested with mold and start rot. Such a sliding joint is also weaker than the others: if the joint fails and slips, then this can compromise the integrity of several other joints. The solution is to introduce a third piece, which locks the slip joint, filling the void and making it impossible for it to slip back.
- The last kind of joint is quite trivial. It is simply a shallow trough, used to position the piece that is joined to it at a right angle. It avoids positioning errors while making the joint stronger, because even a shallow trough (a single plywood veneer's worth) is enough to give the joint plenty of strength once it is saturated with epoxy and filleted.
The assembly process
The assembly team is best organized as two sub-teams: the stuffers and the gluers. These roles don't need to be gender-specific, although I suspect that in a lot of circumstances the stuffers will be mostly boys and the gluers will be mostly girls. The stuffers have to have good upper-body strength and some spatial reasoning abilities. The gluers need fine motor control and tidy habits. For the stuffers, all that matters is speed of assembly, since mistakes are made virtually impossible by the keying on all the joints. For gluers, the strength of the joints and the longevity of the hull critically depends on their attention to detail: all the joints have to be fully saturated, there should be no accidental drips of epoxy anywhere, and the fillets have to have the correct size and shape.
The construction then proceeds as follows. Most of the hull assembly happens with the hull upside-down.
• A stage is erected at a spot that is within 20 feet of the water at high tide, using straight dimensioned lumber and leveled using a laser pointer and wedges.
• The bottom, the sides, the transom, the bulkheads, the internal partitions and pieces of the engine well are assembled using zipper joints and set aside.
• The deck is laid down upside-down on top of the stage and assembled using zipper joints.
• Frames, of which there only two—one at each mast—are assembled next, and through-bolted to the underside of the deck.
• Internal bulkheads and partitions, and the engine well, are installed onto the underside of the deck
• Small brackets called knees are joined to the underside of the deck, going all the way around. The knees sit in shallow slots in the deck to make them easy to position.
• The first layer of sheer clamp is assembled by fitting it onto the tabs in the knees and pulling the joints together using straps.
• The second layer of sheer clamp is screwed and glued onto the first. The bottom edge of this layer (facing up during assembly) holds a zipper joint that joins with the upper edge of the sides and the transom.
• The sides and the transom are assembled next, pushed onto the zipper joints and clamped in place (this is where the stuffers get a good work-out). The sides and the transom mesh together using a box joint.
• The bottom is fitted on, joining the sides and the transom using a box joint. It is horsed on using tensioned straps.
• The joints between the sheer clamp and the sides and between the sides, the bottom and the transom are all saturated with epoxy all at the same time.
• The third layer of sheer clamp is screwed and glued in place.
• Tabs that stick out where the sides, the bottom and the transom meet, and around centerboard trunks, are removed using any number of techniques: a hand plane for the handy, a belt-sander for the well-equipped or a grinder for the those who like tools that have hundreds of uses.
• The centerboard trunks are pre-assembled, passed through apertures in the staging and the deck, propped into place and glued.
• Additional layers of plywood are screwed and glued onto the sides, the bottom and the transom to bring them up to full thickness.
• The bottom, the sides and the sheer clamp are fiberglassed using a layer of mat and 3 layers of cloth.
• The sides and the transom are faired using a lightweight fairing compound and sanded flat.
• Pre-cut copper sheets are screwed onto the bottom and parts of the sides below the waterline.
• The centerboards and the rudder blades are assembled, and the centerboards are installed
• The hull is flipped over. This is done by assembling a trapezoidal cage out of timbers, knocking out one side of the staging, and using a winch to roll the hull onto the cage, and then knocking out the sides and the top of the cage, leaving the hull sitting on just the bottom supports
• All the joints are filleted on the inside of the hull.
• The superstructure—two instrument arches and the dodger or pilothouse—is assembled.
• The deck is fiberglassed, then finished using pre-cut sheets of aluminum diamond plate, which are bedded with caulk and screwed into place.
• The hull is sealed with epoxy inside and painted inside and out.
• Polycarbonate plastic panels are screwed onto the outside of the sheer clamp
• Cleats, bow rollers and rudder post brackets are installed.
• The stage is reassembled as a slipway reaching under the hull. Four casters are inserted into holes in the chine runners, which rest in a slot in the slipway.
• The rudders, the rudder blades and the tiller are assembled.
• The boat is loaded with all of the remaining parts and supplies.
• The engine bracket is installed in the engine well, the engine is lowered onto it, and the fuel tank, battery bank and engine controls are installed.
• A line is secured to the boat, the bottom of the cage on which the hull rests is knocked out, and the boat rolls into the water.
• The crew climbs aboard, starts the engine and motors away from the construction site.
The remaining tasks—installing the concrete ballast and the mast tabernacles, the masts, the stanchions and the lifelines, rigging, plumbing, wiring, berths, cabinetry, galley appliances, etc.—can be completed with the boat in the water. While this is most easily done with the boat docked, but it's quite possible to do the work even at anchor, especially in a spot where it's possible to walk ashore except at high tide. It can remain in the water uninterruptedly for the next 30-35 years: the copper-clad bottom never needs painting, and there are no underwater through-hulls, propellers or other nuisance components to service.