The purpose of this project is to design and mass-produce kits for a floating tiny house that can sail. It combines high-tech modeling and fabrication and low-tech assembly that can be carried out DIY-style on a riverbank or a beach. This boat is a four-bedroom with a kitchen, a bathroom/sauna, a dining room and a living room. The deck is big enough to throw dance parties. It can be used as a river boat, a canal boat or even a beach house. It's rugged and stable enough to take out on the ocean.

Saturday, February 29, 2020

Custom Hardware

Three years ago I bravely published a post titled “The Final Sheeting Arrangement.” I was filled with optimism at the time. After much experimentation I had discovered a simple way to keep Quidnon’s Junk sails sheeted perfectly flat. I had tested it out on a 1:12 scale model and verified that it worked very well indeed. But soon after I published it my friend and very experienced Junk rig operator Dave Zeiger blew my boat straight out of the water by pointing out a major problem with my design: it would not keep the sails anywhere near flat once they have been reefed. I accepted his critique with equanimity and, since I had no solution to offer, kept quiet about it for three years, during which, luckily, not a single person endeavored to build a single Quidnon, and so this unsolved problem hasn’t hurt anyone.

But now I believe I have finally found a solution. With this problem solved, the Quidnon project can finally move past the head-scratching phase and on to the next phase, which will involve grinding out a large number of mechanical drawings, assembly diagrams and other documentation without which no boat can ever get built. Here, then, is my plan, which I will call “The Final-Final Sheeting Arrangement.”

The previous, “final” sheeting arrangement involved attaching the sheet to a padeye on the deck arch near the centerline of the boat, sending it through a block on the boom, down through a block some distance out on the deck arch, up to the first batten, down to another block a bit further out, up to the second batten, and so on. The blocks on the deck arch are mounted on a T-track, allowing their positions to be fine-tuned. Likewise, the blocks hanging from the boom and the battens can be repositioned closer or further away from the leach of the sail for optimum performance on all points of sail. Here is what that looked liked on the scale model, in quite a stiff breeze.


The reason this arrangement works so well is that each block on the sail receives exactly 1/5 of the overall tension on the sheet.


However, this only works on the full sail, all 50 sq.ft (4.6 m2) of it. But if it’s reefed (lowered part way, that is) to compensate for stiffer breezes, more force is concentrated at the bottom, warping the sail and ruining its efficiency. This effect is only slight for the first reef, and gets progressively worse, so that by the time the sail is on its third reef it wouldn’t work as a sail at all because all of the wind would simply be spilled out of it.



As I mentioned, I have now found a way to solve this problem, using a custom piece of hardware.

But before I explain my solution, I’d like to mention another custom piece of hardware, which was already part of the plan: the take-up spool. It solves a number of problems. First, it eliminates cockpit clutter: all loose line magically disappears. Second, it makes a simple winch into a self-tailing one: just take a few turns on the capstan and crank; the take-up reel maintains the tension for you. Third, by automatically taking up slack, it reduces the chance that a loose sheet will get caught on the roach of the sail, requiring a trip out of the cockpit to free it.

Quidnon’s cockpit layout provides an ideal place to hide all of this loose line: directly under the cockpit floor, at the top of the anchor chain locker, where there is plenty of room. The details of the take-up reel are not particularly interesting. It is a sealed metal box bolted to a bulkhead that has a shaft sticking out of it. Inside it is the sort of mechanism found in every wind-up toy or mechanical watch: a constant-force spring and a gear reduction mechanism. The shaft goes through a shaft seal to keep water out and grease in, and the entire mechanism is designed to never require any maintenance. A spool is splined to the shaft and a fairlead some distance away from the spool makes the turns wrap onto the spool tidily.

There will be a total of 12 take-up spools hiding under the cockpit floor, 6 for each sail:
• Halyard (to raise the sail)
• Reefing line (to pull the battens down when reefed)
• Port and starboard sheets – tension end
• Port and starboard sheets – slack end

Why do the sheets have a slack end, and why does it need a take-up reel? That’s what I will explain next. The key element in my cunning plan is a custom piece of hardware that is probably something I invented, because in all of my years of perusing sailing gear catalogs I have never come across such a thing. It is a remote-operated locking sheet block.


In its unlocked state it is just like any sheet block: the sheet goes in one side, around a pulley and out the other side. The pulley is on a bearing and spins freely to minimize friction. In its locked state, the sheet is firmly clamped between the pulley and a shoe. The shoe has a dog that matches a recess in a pulley, preventing it from turning. The shoe has a channel with diagonal serrations similar those on a jam cleat which grab the sheet tighter when it tries to slip in one particular direction. That is, the locking action is unidirectional.

The block is switched between its free state and its locked state by means of a control line which goes through it. On the control line is mounted a very specifically shaped plug. It is prevented from slipping along the line by a ferrule which is crimped onto the line. The ends of the plug are tapered to reduce the amount of tension on the control line needed to move the plug into position by compressing a very strong spring whose job is to clamp the sheet in place. There is also a much weaker tension spring whose job is to keep the shoe away from the sheet when the block is in its free state.

The locking sheet blocks are mounted on the T-track on top of each side of each deck arch, observing correct orientation, so that the locking action is when the sheet is pulled to outboard. There are four signal lines which are sent through four cascades of five locking blocks each. A fairlead at each end of each cascade prevents the plug from escaping. Each of the four control lines is led to the cockpit, forming a loop.

When the sail is fully raised, the inboard-most block is locked. When the sail is at first reef, the next block to outboard is locked; and so on. As each reef is taken in, the sheet purchase is reduced from x10 to x8, x6 and so on down to x2, at which point only the topmost panel is showing (to use the mainsail as a riding sail when at anchor, or to use on the foresail for scudding off with a drogue in extremely heavy weather). Note that there are two control line adjustments to be made: one for the port sheet and one for the starboard sheet.

The steps to take in or to let out a reef (or two or three or four) are as follows:

• Open the sheet clutch to depower the sail
• Open the reefing line clutch
• Open the halyard clutch, pay out/haul in the required amount of halyard, close the halyard clutch
• Haul in the reefing line, close the reefing line clutch
• Move the starboard control line the required number of clicks; repeat for the port line
• Haul in the sheet to power up the sail, close the sheet clutch

Importantly, all sail evolutions can now be done without leaving the cockpit. This has been a requirement all along. Quidnon is designed for easy single-handed operation.

There are a couple more changes to the design which are small but important. Previously, the two pilot berths, which are on both sides of the salon and on top of the water/ballast tanks, were accessed by climbing up on the settees and going through a door in the two bulkheads that make up the keelboard trunk.




This plan raised several objections. First, this method of ingress seemed rather undignified, required rather excellent range of movement in the hips and wasn’t at all convenient if attempted in the course of a dinner party, during which the settees in the salon would be occupied. Second, cutting a door through the keelboard trunk resulted in some significant structural complications, Third, it wasn’t clear how to provide good sound insulation, which would be important if pilot berth occupants wished to sleep while a dinner party was in progress.

For all of these reasons, the pilot berths will now open to the stateroom, which is in the bow, with a small two-step ladder leading into each and with the opening fitted with a sliding door. This makes the layout of the pilot berths much more convenient, with some free space at the entrance, then the berth, and some cabinetry at the head.



Finally, the decision to eliminate one of the keelboards has been reversed. The reason is that a single keelboard positioned off-center would give Quidnon a different turning radius depending on which direction it was turning. If the keelboard were mounted to starboard, the boat would turn tighter to port; and vice versa. This seems like a very bad feature. With such a wide hull, it is important to be able to reliably execute the tightest possible turns when maneuvering in and out of marinas. Another advantage of having two keelboards is that they can be made smaller, easier to manage and less likely to damage the hull if they hit something underwater.

As I already mentioned, this completes the head-scratching phase of the project. The next phase will involve producing detailed construction plans and cost estimates.

Saturday, October 19, 2019

Engine Mount Design

Deployed — Stowed — Raised for maintenance

Quidnon is rather indifferent to choice of engine: just about any outboard over 25hp will do. But the leading contender right now is Yamaha T50 or T60 (the number is the horsepower rating and the T stands for high-thrust, which is bad for high-speed planing and good for pushing a heavy barge). The engine is installed in an engine well, making it an inboard outboard, if you will.

This arrangement presents a few design challenges:

• Normally outboard engines are hung directly on the transom. When not in use they tilt until they are out of the water. But in an engine well there is no room for the engine to tilt; instead, it has to slide up and down inside the well.

• Normally, control cables for the throttle and the shifter are led forward from the engine, but in an engine well the engine is up against a bulkhead, so control cables have to execute a tight 180º turn as they exit the front of the engine, which is something that cables can’t do.

• Also, engines are usually bolted into place (they come equipped with clamps, but these are far less secure than bolts). But bolting the engine into place when it is in the engine well would require reaching down, and perhaps hanging down, into the well—a very awkward working position—and this would have to be done every time the engine has to come out for maintenance.

• Lastly, what happens when the engine hits a submerged rock or some other obstruction? Does the engine’s lower unit get destroyed, or does it just get banged up a bit while it is the engine mount that fails. And when the engine mount fails, how does the owner repair it on the spot using provided spare parts and without having to haul out the boat?

Quidnon’s engine mount design solves all of these problems.

Backing up a bit, some contraption—be it a shop crane, a hoist or an improvised A-frame—is used to lift it into place, usually with the boat ashore. In exceptional circumstances two or three big, strong men can simply lift it into place with the boat backed up to a floating dock, but this is a risky operation. On Quidnon, which is designed to never need a haul-out, it has to be possible to install and remove the engine with the boat in the water.

This is done using a swinging hoist that is part of the aft deck arch. The hoist is used to lift the engine off a floating dock or a dinghy, lift it up to the deck (a rise of 10 feet/3m or so) swing it toward the engine well, and install it onto the engine mount. This would have to be done repeatedly because outboard engines don’t last that long, with 1200 hours being the typical point at which people give up on trying to make them run reliably and buy a new one.

Someone who motors all the way down the Intracoastal Waterway and back every year, putting around 300 hours on the engine each time, usually needs to replace the engine every four years. A lot depends on the amount of preventive maintenance, and with enough care that number can be doubled to eight years. A complete overhaul can stretch it out to ten. But Quidnon’s expected useful life is at least 30 years, so it will need to be repowered at least three times, and perhaps as many as ten. Luckily, outboard engines don’t cost that much. A Yamaha t50 with 0 hours costs around $10k. Now, $100k is quite a bit of money for most people, even over 30 years.

The amount of preventive maintenance an engine receives is generally a function of how easy it is to get at. Impossibly awkward and cramped engine spaces that are common on sailing yachts with inboard diesels will quite predictably receive less than the optimum amount of attention from their owners; but if the engine can be pulled out and placed on a stand without so much as breaking a sweat, working on it and tinkering with it will be a pleasure and it will receive all the care it needs. Quidnon’s dedicated engine hoist incorporated into the aft deck arch and the design of the engine mount are intended to make working on the engine easy and pleasant.

The engine mount consists of just seven major components:

• Four brackets that are attached to the forward bulkhead in the engine well, two at the top of the well and two at the bottom

• Two rods that run vertically between the two sets of brackets

Upper bracket
Lower bracket


• A slider car which slides up and down on the two rods and incorporates a large, solid piece of hardwood to which the engine is bolted

Car

The brackets and the car are welded up out of A500 steel and subjected to the same galvanization process used for anchors and anchor chains. They consist of tubes, square and rectangular pieces of channel and plates.

The two rods are of stainless steel because they have to be smooth to keep the slider car from binding up and can’t have a surface finish because it would wear through over time. The rods have caps welded to their top ends to keep them from falling through the brackets.

The brackets and the rods are not in direct contact. Instead, neoprene rubber inserts are used to isolate the galvanized steel from the stainless to keep them from galling together through galvanic action, to dampen the vibrations in the rods (which would otherwise ring like a bell at certain engine speeds) and to prevent engine vibrations from being transmitted to the brackets, the bulkhead and from there to the rest of the hull.

The car which slides up and down on the rods and on which the engine hangs uses similar inserts but of different material: Delrin plastic instead of neoprene rubber. This material is slippery and allows the car to slide easily. The inserts are forced into the pipes at each end of the car and slide freely on the rods.

The order of assembly is as follows.

• Hoist the engine aboard
• Bolt the engine onto the car with it hanging above deck
• Lower the engine into the well and skewer it into place by dropping in the two rods

There are a few more minor details:

• When the bottom of the engine hits a rock, the bottom two brackets are the designated points of failure. What fails on them is not the brackets themselves but the nuts that hold them against the bulkhead. The nuts are stripped off the pieces of threaded rod onto which they are threaded. In turn, the pieces of threaded rod is screwed into a socket that is installed from the opposite side of the bulkhead.

Designated point of failure marked in red

The repair procedure then involves lifting out the engine (it is left hanging on a lanyard, which is the usual precaution to losing it), removing the stripped pieces of threaded rod (they have a slot at one end, to accept a screwdriver), screw in new pieces of threaded rod (provided as spares) and reattach the brackets using fresh lock washers and nuts. Then the engine (with the damaged bottom unit replaced or repaired as needed) can be put back into place and into service.

There are a few more elements to the design that are small but critical:

• A small custom 3D-printed part to make it possible for the control cables to face aft and up instead of forward.

• Lanyards for each bracket, so that they don’t go swimming if they are torn off the bulkhead in an underwater collision.

• Clips to keep the rods from falling out in a capsize.

One last element of this design will most likely need to be determined experimentally: how much and of what kind of sound insulation to install inside the engine well to keep the noise level in the aft cabins low enough so that people can sleep soundly with the boat moving under engine.

The engine mount was the last important conceptual part of the design that needed to be completed. Now that it is, the work of putting together detailed construction drawings can begin. It’s taken a long time, but we have finally arrived at that stage. Thank you for your patience!

Tuesday, August 13, 2019

Hull Assembly Made Easy

This project is now in its fifth year and, dare I say, running smoothly. It started out as a pile of good ideas that came out of the experience of living aboard both custom-built and commercially built sailboats in various climates and social environments, plus a promise: that this project will result in plans and a kit for constructing a houseboat that can sail. A further stated goal is to make it possible to build and launch it quickly and easily using the efforts of moderately skilled people, working alone or in small groups. The reason it has taken so long has to do with the large amount of thought it has taken to bridge the gap between stating these good ideas and making them realizable.

One of the requirements for building the hull has been the following: “...low-tech assembly that can be carried out DIY-style on a riverbank or a beach.” Easier said than done! How can one build a hull that’s true and fair without having so much as a true horizontal surface for a reference?

Until now, the interim plan (for lack of a real one) was to build the hull upside-down, starting with the deck. Once the two layers of plywood that make up the deck are screwed and glued together, a frame is erected over the underside of the deck. Then the plywood panels that make up the sides are screwed and glued on, then the bottom. Then the entire bottom of the hull is sheathed in fiberglass, and the bottom covered in copper sheets. Finally, the hull is flipped right-side-up, and the upper surface of the deck and the superstructure (deck arches, cockpit, dodger and hatches) are completed. Then the hull can be splashed and the interior work finished with the boat in the water, preferably at a dock or in a slip at a marina.

There is a problem with this plan: assembling the deck requires a perfectly flat surface, or the deck, and then the frame, will end up warped, making the rest of the hull impossible to assemble. But where can one find a perfectly flat and level surface on a riverbank or a beach? Having to first erect a 20 by 40 foot platform makes the project take longer and cost more.

But there is an alternative: start by assembling the frame, still upside-down, and save the deck for last, to be assembled once the hull has been flipped right-side-up. The frame is built up in “stations,” which are vertical slices of the hull going from the transom to the bow. Once each station is in one piece, it is stood up vertically and joined to the previous station using longitudinal frame members. The stations can be propped up on bricks, cinderblocks, rocks, timbers, bits of driftwood or whatever else is readily available. The height of these makeshift supports can be adjusted by digging under them to lower them or by piling up soil or sand under them to raise them up. After each station is joined to the previous one, plywood panels that make up the sides are screwed and glued on immediately. To fine-tune the vertical alignment of each station of the frame, wedges can driven in under frame members.

Once the entire frame has been assembled and the sides installed, plywood panels that make up the bottom are added. Some amount of tugging at the frame left and right may be required in order to counteract the frame's trapezoidal tendencies and to align the frame with the bottom panels. This can be done using a Spanish windlass: a loop of rope and a stick with which to twist it. Once the bottom has been assembled, the sides and the bottom are sheathed in fiberglass. Finally, the bottom, topsides and transom up to the waterline are covered in copper sheets and the topsides above the waterline are faired and painted. Now the hull can be flipped right-side-up. At this point, a bit of foresight is called for, to make it easy, when the time comes, to roll the hull into the water over logs, dragged over skids, or whatever other arrangement can be contrived for the splashdown. Ideally, all that will be needed is to knock out some chocks and let gravity do the rest.

Once the hull has been flipped and until the deck is assembled, it is open to the sky, forming an above-ground swimming pool, and so the plan should be either to complete the deck in short order, or to erect a tent over the unfinished hull, because having it fill up with rainwater would be bad for it. Installing the deck involves laying down, screwing and gluing two layers of plywood, sheathing the top surface with fiberglass, and installing aluminum diamond hatch panels over it.

Once the deck is complete, the hull is ready for water and can be splashed immediately, although I suspect that most people would prefer to assemble and install the deck arches, the cockpit seats, the dodger and the hatch cover prior to launch. In any case, some amount of hardware needs to be added beforehand: gudgeons for the rudder, engine bracket, deck cleats, etc. Since the lifelines attach to the deck arches, and may be required for launch as a safety consideration, the deck arches need to go on first. Masts and sails can be added at any time later, or even not at all if sailing turns out not to be in the cards. The motor (Yamaha t50 long shaft is still the favorite) can be dropped into its engine well either before or after launch, or not at all if all that's required is to float in a marina slip or at a mooring ball.

This assembly procedure fulfills the promise of “...low-tech assembly that can be carried out DIY-style on a riverbank or a beach.” Plywood panels are installed using brushes for brushing on the epoxy and screw guns for driving screws through the plywood (where indicated) and into the frame members. Fiberglass sheathing is added by draping fiberglass cloth and saturating it with epoxy using squeegees and rollers. Copper for the bottom and aluminum diamond hatch for the deck are laid on using specific glue and caulk, but the procedures are simple. Fairing and painting the topsides is done using spreaders, sanders, rollers and brushes. All of this is very much within the skill set of anyone who is moderately handy and can follow instructions.

But what about frame assembly? Well, here is where there has been a recent breakthrough. Now the only tools required for assembling the frame are a wooden mallet and a ratchet with a hex socket. The frame can be hammered together and will hang together by gravity and friction.


The frame consists of brackets and frame members. The brackets are welded together out of aluminum square tubing, 3½ by 3½ inches if you build to imperial measurements, 100x100mm if to metric. The frame members are made of Douglas fir timbers, also 3½ by 3½ inches or 100x100mm. The ends of each timber are precisely machined: the last six inches on each end are taken down by the thickness of the aluminum tubing for a tight press-fit into a bracket and to compensate for any twist along the length of the timber; the very tip on each end is tapered for ease of insertion into the bracket; the ridges that are six inches from each tip are milled to set a precise length from ridge to ridge and therefore from bracket to bracket. Two sides of each timber, as needed, are planed flat to compensate for any bowing and twist. Once it is milled, each frame member is coated with penetrating epoxy, making it immune to short-term humidity fluctuations and preventing any further bowing or twist.

Building up the frame involves driving frame members into brackets using a mallet, then fixing them in place by screwing in a single self-tapping screw for each joint. The screw does the additional job of making the already tight, press-fit joint even tighter by compressing the grain at each end of each frame member. Since the tips of all frame members are confined within an aluminum tube, it doesn't matter if the screw splits the grain; that frame member isn't going to go anywhere. Then, once the boat is in the water, osmosis causes the water content of the frame members to increase, causing it to swell up slightly and further tighten the joints. The use of softwood will prevent the frame members from bursting the aluminum brackets, as would happen if hardwood were used.

Some two dozen different bracket designs are needed for the entire frame. One set, used throughout the frame, is quite generic: the brackets are designed for a variety of joints, but since the hull is square, all of these joints are at 90º.


Another set of brackets is used to join frame members along the bottom. These are fabricated in a variety of specific angles, to accommodate the shape of the bottom.


Here is the hull frame in longitudinal view with the brackets omitted and the locations of the transverse frame members indicated in magenta. Note the rounded plywood panel at the bow; there are four of them, and they are used to create the rounded shape of the bow, which is the only curve in the entire hull. There are four of these panels, located at Y=8, 1.5, -1.5 and 8 feet, where Y=0 is the centerline. Also shown is the inner layer of the plywood panels that make up the sides, which are screwed and glued into place as the frame is assembled, starting at the transom. All of the plywood panels will be marked with the locations of all of the screws.


And here is the top view of the horizontal cross-section of the frame corresponding to Z=8, which is the deck (horizontal cross-sections start at Z=0, corresponding to the flat part of the bottom, to Z=8 at the deck). This view shows all of the brackets that are located immediately underneath the deck and the inner layer of plywood panels that make up the deck. The plywood panels are staggered between the layers to maximize overlap while minimizing scrap.


At this stage, the end of the project’s design phase is starting to come into focus. At this point it is a matter of completing the mechanical drawings, numbering all the parts, generating tool paths for milling them out and, very importantly, generating a bill of materials in spreadsheet form for producing precise cost estimates and assembly time estimates. The project is now at a point where new design ideas are not necessary for completing it. If all goes well, detailed study plans and a cost estimator will be made available before the end of this year.

Sunday, June 16, 2019

Dismasting Made Easy

You are sailing along on a passage, on autopilot, the radar set up to wake up and do a sweep every 10 minutes or so and sound an alarm if it detects a collision course, with the entire crew (which could be just me and the ship’s cat) down below doing whatever people and cats do when they aren’t sailing. Then a squall kicks up, or a waterspout (a sort of water-borne tornado), or you royally screwed up and plotted a course that takes you under a bridge that’s too low. Suddenly, you find yourself minus the masts. This can be very dramatic, or not, depending on how the boat is designed. And since Quidnon is primarily a houseboat (that sails), drama is specifically what we don’t want.

There are a few different solutions for installing masts. First, there are deck-stepped masts. They are installed using a crane which lifts the mast up by a point somewhere above its center of mass so that it hangs down more or less straight. The heel of the mast is placed where intended, and then the standing rigging is hooked up, which consists of wire rope and turnbuckles with which to tension it. Standing rigging consists of a forestay, a backstay and some number of shrouds that go off to the sides of the deck and may go around spreaders. (By the way, spreaders are a terrible idea, unless you like your deck to be covered in guano, because they provide nice perches for sea birds.) Where there isn’t room for a backstay (such as with a mizzen mast on a ketch or a yawl) there are often running stays which are clipped on and tensioned as needed. There may also be baby stays (miniature forestays) and triatics that tie the tops of masts together.

Second, there are the keel-stepped masts. These go through a reinforced hole in the deck (which will at some point leak water into the cabin) and the heel of the mast is stepped in a bracket that’s bolted to the top of the keel. The nice thing about keel-stepped masts is that they don’t flop down instanter whenever some bit of standing rigging fails. On a deck-stepped mast, if the forestay fails, then the mast flops down on the cockpit, braining whoever happens to be in it; if the backstay fails, then it flops forward. The standard material for standing rigging is stainless steel wire rope, used because it’s less stretchy than regular galvanized wire rope, and stainless steel fittings to attach it (turnbuckles, shackles, etc.) The nasty thing about stainless (other than its exorbitant cost) is that unlike regular mild steel it tends to develop invisible microfractures over time, then fail catastrophically.

When standing rigging on a keel-stepped mast fails, it may soldier on for quite a while, enlarging its hole in the deck as it swings about. When it finally fails, it is likely to snap off at the deck, since that’s the point of greatest stress. Either way, what you end up is a rather large stick flailing about uncontrollably, tugging at a mad tangle of rope and cable that gets caught up on everything it possibly can, trying to rip it off. At that point, people generally rush about the deck with bolt cutters, tying to snap every bit of line and cable that connects the mast to the boat, in order to set the mast on a journey of is own, down to the murky depths.

There are also unstayed masts which have no standing rigging at all. These are always keel-stepped, since if they were deck-stepped they would simply fall over. They have to be quite a bit stronger than stayed masts, since they rather than the standing rigging have to withstand the press of the sails. To keep their weight reasonable, they are usually tapered. Mast-stepping techniques are a bit like the techniques for holding up your pants: deck-stepped masts with standing rigging are like wearing suspenders, keel-stepped masts without standing rigging are like wearing a belt, and keel-stepped masts with standing rigging are like wearing both. Which of these makes for the most exciting strip-tease (dismasting, that is) is, I suppose, a matter of taste.

Keel-stepped masts have some disadvantages. I already mentioned the almost inevitable leaks through the hole in the deck. There is also the problem of sagging, especially if there is standing rigging: the mast pushes down on the center of the boat while the forestay and the backstay pull up on the bow and the transom. Over time, this causes the hull to acquire a slight banana shape. In turn, this causes bilge water to pool around the mast heel. The bracket the mast heel rests in is usually made of mild steel while the mast itself is usually aluminum, and the two undergo a galvanic reaction: the bracket rusts while the mast heel rots away. If the forestay or the backstay and the mast heel both fail, then you have the bottom end of the mast ripping through the cabin.

Finally, keel-stepped masts chill the cabin. Aluminum is an excellent conductor of heat, and having an aluminum stick part of which is inside the cabin and part of it outside sucks heat out of the cabin most efficiently. Wrapping it in layers of radiant barrier and fabric helps somewhat, but it’s much more pleasant not to have it there in the first place.

Mounting the masts on Quidnon presents a rather interesting design problem. Since there is no keel, keel-stepped is not an option. Since there is a requirement that the masts be easy to raise and lower without recourse to a crane, deck-stepped is not an option either. And since the sails are Junk rigs, which rise above the top of the mast when fully raised, having forestays and backstays is not an option either. Lastly, Quidnon is a houseboat, and whereas with a sailboat built for sport or ostentation it is acceptable to respond to a dismasting at sea by declaring it a total loss, abandoning ship and setting off in a life raft expecting to be rescued (or not, as the case may be) with Quidnon the loss of two large vertical sticks should not compromise its ability to serve as a floating domicile, albeit one now temporarily deprived of its ability to sail. It is thus a requirement that a dismasting does not compromise the integrity of the hull.

Since Quidnons will spend most of the time sitting at anchor or at the dock and only once in a while undertake a journey under sail, perhaps as a seasonal migration to shift berth between summer and winter quarters, perhaps to relocate to a different permanent location as conditions warrant, most of the time the masts can be kept lowered and the sails bundled up into their sail covers and stowed on deck. Thus, it is yet another requirement that the masts be unobtrusive when lowered.

This mast tabernacle design has gone through a number of changes but is now in a state that fulfills all of these requirements. Here are the plan and elevation views with the masts lowered and resting on the deck arches. Note that with the masts lowered Quidnon is not any longer overall than with the masts raised. This is important, because marinas charge slip fees by overall length, which includes any overhanging objects. Quidnon fits into exactly 36 feet, makes full use of the width of a marina slip with its 16-foot beam, and provides very close to 36 by 16 feet, or 576 square feet of interior living space with ample headroom.



There are three deck arches, and they serve a large number of purposes:

• They provide support for the masts when they are lowered

• They allow the masts to slide back and forth, back before being raised, forth after being lowered, on rollers positioned close to the centerline

• The second and third deck arches have T-track with sheet blocks running along their tops

• They provide cabin ventilation through openings in their front and back, blowing air into the cabin and sucking it out again

• They serve as a frame for either a canvas cover or shrink-wrap for winterizing the boat

• The second deck arch has a block and tackle for loading and unloading the boat through the deck hatch

• The third deck arch has a block and tackle for installing and removing the outboard engine that lives in the engine well

• The first deck arch provides a mounting place for the radar’s radome

• The deck arches provide places to hang hammocks or swings, to mount solar panels, etc.

In short, deck arches are fantastically versatile and useful, which is why Quidnon has not one, not two, but three of them.

Here is the elevation view of Quidnon viewed from the transom, with the masts lowered and sitting side by side on the deck arches.



Note the various dimensions. The hull is basically an 8-foot by 16-foot by 36-foot box. It is 1 plywood sheet tall, 2 plywood sheets wide and 4.5 plywood sheets long, arranged in a pattern that generates minimum scrap. There is 5½ feet of vertical clearance below the deck arches, and the taller people will have to stoop to walk under them. On the other hand, they are low enough for most adults to be able to work with them, and with the masts that rest on them, without having to resort to footstools or stepladders. It’s a compromise. The bridge clearance with masts lowered is 14 feet, and most fixed bridges on navigable waterways provide at least that much.

Now let’s go through the details of the mast stepping arrangement. Here is a drawing of a mast (in this case, the mainmast, but the differences are subtle). There are three main elements:

• The mast itself, which includes a masthead fitting at the top and a heel plug at the bottom. The mast is made up of either a single 36-foot length of 6-inch Schedule 40 aluminum pipe or (since 6-inch Schedule 40 pipe is most easily obtained in 20-foot sections) two pieces joined together using a short length of inner tube and some epoxy. (Welding the two pieces together is also possible, but making structurally sound welds in aluminum is quite an art while the epoxied joint is dead simple and relatively idiot-proof.)

• The tabernacle, which is made of galvanized mild steel and can be fabricated using an oxyacetylene cutting torch, a stick welder and a grinder (although a plasma cutter and a TIG welder would work even better) and includes a mast hinge at the top and a pressure plate at the bottom.

• The mast trunk, which is a cylindrical piece of lumber that runs from the bottom of the hull through a hole in the deck and protrudes 3 feet above it. The mast tabernacle fits over it.



The set-up is basically of a deck-stepped mast, because the pressure plate rests on the deck. But the mast doesn’t topple without standing rigging because the tabernacle sits over the mast trunk, which is constrained to being vertical. It goes through a hole in the deck, where it is secured using a pin and caulked into place, so that there are no deck leaks. The heel of the mast trunk sits in a cup that is fastened to the bottom. There is an air gap between the bottom of the mast trunk and the hull bottom of the cup, so that the mast trunk does not exert any vertical force on the hull bottom as the hull flexes. It does exert horizontal forces, which the bottom can readily withstand.

Taking each of these elements in turn. The masthead fitting is a simple affair; like all the other elements except the mast and the mast trunk, it is made of galvanized mild steel. It consists of a short piece of pipe that fits over the masthead welded to an oval plate with two gussets that face fore and aft. The gussets have holes which take the pin of a D-shackle. This shackle is then used to attach, using teardrop-shaped thimbles, all of the needed lines: the halyard, two topping lifts and four running stays (of which more later).

Masthead fittings generally include some number of brackets for mounting a VHF antenna, an illuminated wind direction indicator and a wind instrument that measures wind speed and direction. It is also a good place to mount a 3/4/5G router; at some 50 feet above water it will “see” towers quite far over the horizon, making it possible to have internet and VOIP access even when sailing outside of sight of land.

All of these masthead instruments generate quite a mess of wiring which has to be sent down the mast and into the hull. To keep it banging around inside the mast, keeping people awake at night, a good trick is to squeeze the wiring into a tight bundle using large zip ties every foot or so and leaving the tail of the zip tie in place to push the wiring to one side of the mast. The masthead fitting plate has a hole in it for sending the wiring bundle through. It is then closed off with a plastic plug and the cracks caulked.


At the mast heel there is an indexing bolt that is used to align the mast with a recess milled into the mast hinge. It also serves the function of keeping the mast captive within the mast hinge.

Next down is the mast tabernacle. The mast slides through the 1-foot pipe that is part the top tabernacle hinge and is held captive by it because neither the masthead fitting nor the mast heel fitting can slide past it. The inside of the top tabernacle hinge pipe is coated with graphite-loaded epoxy to create a low-friction surface. When raising the mast, it is slid aft until the mast heel is aligned with the bottom of the hinge plate and rotated until the head of the indexing bolt fits into the matching recess in the hinge plate. Another bolt is then screwed in to hold the mast to the hinge, preventing it from slipping as it is raised.

Part of the top tabernacle hinge is a fitting that accepts a 5-foot gin pole which is used to raise and lower the mast using a hand winch. It is a solid 2½-inch steel rod that has to accept well over 1000 lbs. of load without flexing.

The top tabernacle hinge is connected to the bottom hinge using a slightly tapered hinge pin. A second tapered hinge pin is inserted on the opposite side of the hinge to secure it in place as soon as it is raised. The hinge pins can then be pounded until the joint and tight and secured using a nut and a stop nut. This immobilizes the hinge, preventing friction and wear.

All of the wiring going through the mast has to be fitted with connectors at the mast tabernacle. The connectors should be waterproof, because there will inevitably be condensation inside the mast.



At the bottom of the tabernacle is the thrust plate, which rests on deck, where it is, again, coated with epoxy loaded with graphite powder, creating a low-friction bearing surface. The tabernacle fits snugly over the mast trunk, which rises 3 feet above the deck.



Where the mast trunk penetrates the deck it is pinned into place and caulked, to prevent deck leaks. Thus, the mast trunk hangs from the deck rather than resting on its heel. Instead, its heel floats in its heel fitting, which is fastened to the bottom of the boat via a wooden block cut to the appropriate angle. The mast trunk heel fitting is not subjected to any vertical loads, only horizontal ones, which the bottom of the boat can readily handle. The mast trunk incorporates a slot that accepts the mast wiring bundle, which snakes all the way down into the bilge, through the mast trunk heel fitting, and back toward the cockpit. Within the cabin the wiring is hidden by installing a decorative cover over the slot.

A key feature of the mast trunk is the notch. It is located an inch or so above the deck and is the designated failure point in a dismasting event. The depth of the notch is calibrated so that the mast trunk is only slightly weaker than the mast tabernacle or the mast. Once the mast trunk snaps off, the mast and the tabernacle are free to topple overboard as a unit. Some amount of additional damage is inevitable. The wiring bundle will be pulled apart and the masthead instruments are likely to be destroyed. To free the mast, several lines need to be released: 4 running stays, the sheet, the halyard and the reefing line. But this isn’t a lot of work: 4 on snap shackle pins released and three rope clutches opened. Dismasting made easy!

But what is most important is that the rest of the boat remains undamaged. After a dismasting event, a Quidnon owner can say “Masts? What masts?” shrug and motor on nonchalantly. When the time comes to replace the masts, any welding/machine shop can fabricate a new mast tabernacle and mast fittings, any wood shop can make a new mast trunk, any canvas shop can stitch together the sail out of Sunbrella fabric (a tough material used for awnings), the pipe for the masts is quite standard and easily obtained, and masthead instruments and rigging components can be mail-ordered from the usual outfits. The rest is just puttering about, to be done at one’s leisure. And if the masts and the sails can be salvaged, then all that needs replacing is a piece of wood (the mast trunk) and some masthead instruments.

The only difficult task in replacing the masts is heaving them onto the deck arches. Each mast weighs around 200 lbs, so it is best to have at least three strong-backed people on hand to assist with this operation. The easiest way to do this is to place the masts on the dock next to the boat and roll them aboard using two loops of rope or strapping, one placed fore, one aft. One end of each loop is secured, and the other one pulled, rolling the mast onto the deck arches and into place. With this technique and four people, two people are pulling, exerting 50 lbs. of force each, and two more are making sure that everything stays nice and even. Once all the pieces are in place, the masts can be raised.

Prior to being raised, seven lines have to be attached to the masthead:

• Four running stays, two forward, two aft

• Two topping lifts, one forward, one aft

• One halyard, aft

These can be draped over the deck arches to keep them from snagging on things or getting dropped in the water as the mast comes up. The running stays can be shackled to their respective pad eyes on deck ahead of time; the rest of the lines can be tied off at the nearest available deck cleat.



For the foremast, the gin pole interferes with the forward deck arch, and so the deck arch, which is hinged at the front, is tilted forward and out of the way for the duration. This involves loosening two turnbuckles and removing two clevis pins.



The masts tend to wobble between port and starboard as they come up, or lean to port or starboard, or both, especially if there is a bit of a sea running, or if the boat lists a bit from the way it is loaded, or if there are wakes from passing boats. This is nothing to worry about: the mast tabernacle can spin around on the mast trunk. Once the mast is all the way up it can be rotated to the correct fore-and-aft position out by putting some extra tension on the hand winch line.

The masts have 1º forward rake (meaning that they lean forward 1º) and once they come up all the way they flop decisively into place. At that point, the second, forward hinge pin is inserted and the hinge pins pounded in and secured in place using nuts and stop nuts. The hand winch line can then be removed. The next step is to install the running stays.

Quidnon’s method of keeping the pants up is the “belt and suspenders” method. The mast trunk is the belt, and keeps the mast up even by itself, but it is not sufficient to withstand the pull of the sails or the rocking of the masts in heavy weather. For this, running stays (suspenders) are needed as well.



For the running stays, galvanized steel wire rope is an economical choice, but it tends to be rather cumbersome to store between sails because it has to be coiled. A more expensive but excellent choice is Spectra or Dyneema, which are synthetic fibers that are just as strong but so flexible that they can be stuffed into a bag. There are four running stays per mast, all going to the sides of the deck, two forward (to oppose the weight of the sails) and two back (to oppose the pull of the sails). The running stays need to be clipped into place and tensioned before the sails can be put up.



The procedure for raising the masts is now pretty simple:

1. Attach lines to masthead fitting, drape them over the deck arches; clip running stays into place

2. Roll the mast into position

3. Rotate the mast until the indexing bolt fits into its matching recess

4. Thread a bolt through the tabernacle hinge and into the mast (wait to tighten it until the mast is up)

5. Connect mast wiring cables at tabernacle hinge; test the circuits for opens and shorts

6. Attach gin pole (insert into top tabernacle hinge, insert retainer clevis pin and ring-ding)

7. Attach line from hand winch to D-shackle at the end of the gin pole

8. Heave the mast upright using the hand winch

9. Insert second (forward) hinge pin

10. Pound in and secure hinge pins

11. Tighten the bolt in the tabernacle hinge that holds the mast in place

12. Tension the running stays

The procedure for taking the mast down is almost the exact reverse of the one for raising it:

1. Pull the lines in the running stay purchases out of their jam cleats and flake their lines on deck so that they run out as the mast comes down

2. Loosen the hinge pins (loosen the lock nuts and the nuts and given the pins a tap so that they turn freely)

3. Attach the line from the hand winch to the D-shackle at the end of the gin pole and take out most of the slack

4. Take out the second (forward) hinge pin

5. Get the mast started by pulling back on it using any of the lines that run from the masthead

6. Ease it down using the hand winch; horse it onto its rollers if it comes down at an angle.

7. Detach the line from the hand winch to the D-shackle at the end of the gin pole

8. Detach gin pole (take out ring-ding, slide out clevis pin, remove gin pole from tabernacle hinge)

9. Disconnect masthead wiring at the tabernacle hinge

10. Remove the bolt that holds the mast in position

11. Slide the mast forward

12. Detach lines from masthead

I wish it were possible to simplify this procedure from this 12-step program, but I don’t see how. As it is, the design achieves the following important objectives:

• The masts are secure and unobtrusive when stored on the deck arches and don’t add to the overall length of the boat (thus avoiding any added expense)

• The masts can be raised and lowered by just one person in a couple of hours (probably less with practice)

• In the unlikely event of a dismasting, there is unlikely to be severe damage to the hull and the injured mast can be dropped overboard by undoing four snap shackles and releasing three rope clutches.

• A salvaged mast (which may survive undamaged) can be reinstalled after replacing a single sacrificial wooden component, spares of which can be kept on board, plus the ruined masthead instruments

The entire sailing rig design is at this point far enough along to be set aside for now; the next step is to produce detailed fabrication drawings. Some other previously missing parts of the design, such as the engine bracket (which slides up and down) are pretty much done too, and are at the same stage, but are not exciting enough to deserve an entire blog post.

Therefore, we will now move on to mapping out the build process, starting with the deck, then moving on to the frame and the bulkheads, the bottom, the topsides and, finally, the surface of the deck and the superstructure (which can be completed with the boat in the water).

Wednesday, May 22, 2019

The Rudder

Rudder assembly
Quidnon’s steering has evolved quite a lot since the original concept. Now all that’s left of the original concept is the idea that the rudder should have a kick-up blade: when sailing across shallows it should gently float up instead of getting torn off or getting stuck, and when the boat settles on its bottom at low tide the rudder blade should automatically get itself out of the way. Only now has a good solution to this problem finally been found.

Early on it was thought that twin rudders and wheel steering made sense, but this made the design complicated and expensive. Twin rudders require a complicated steering linkage that uses something called Ackermann geometry, which is also used in cars: when turning to the right, the right wheel has to turn more than the left wheel because, being closer to the point around which the car turns, it has to follow a tighter circle.

Later on, after single-handing a 36-foot sailboat from Boston to South Carolina, I discovered that wheel steering is a bad idea and that I prefer a simple tiller. There are very few steering positions that are comfortable with a wheel: sitting behind it and standing behind it are more or less the only choices, and they both get tiresome rather quickly. On the other hand, with a tiller, it is possible to steer the boat while standing, sitting or lying down, using hands, feet and hips, or, with a tiller extension clipped on, with the inside of the knee or the armpit. It is possible to operate the tiller remotely, by tying a bungee cord to one side of it and pulling it to the other side using a lanyard.

In turn, a tiller on a boat of Quidnon's size is only workable if the rudder is a balanced rudder, with about a third of its area ahead of its rotational axis, so that the boat can be steered with a fingertip instead of your heel on the tiller pushing with all your might, as is the case with an unbalanced “barn door” rudder that rotates around its forward edge.

Further on, I discovered that Quidnon doesn’t heel enough to make twin rudders necessary: just a single rudder would work fine, and so the design was changed to a single rudder hung off the center of the transom. But this arrangement was still somewhat problematic. First, the rudder assembly cluttered up the transom and made the boat a bit longer (which is a problem because marinas charge slip fees by overall length). Second, the pivot point of the rudder was too far from the cockpit to give the tiller a useful swing range.

Rudder assembly installed in engine well
And so the rudder was moved from the transom to the back of the engine well, where there is just enough room for it. This made it possible to solve a few more problems.

Quidnon doesn’t always need to have a rudder. It is a houseboat, and houseboats mostly just sit at the dock, where having a rudder is not just unnecessary but also rather inconvenient. The tiller tends to whip around and hit things whenever the tidal current shifts or a boat wake hits. Since it sits in the water, it tends to accumulate marine growth which makes it not work very well when the time comes to move the boat. A better solution is a rudder assembly that is easy to install and just as easy to take out again when the boat is at rest.

Gudgeons in engine well: top view; aft view

With the rudder assembly removed, all that remains on the hull are two gudgeons bolted to the back of the engine well along the centerline. To install the rudder assembly, it is turned 90º, so that the tiller faces directly sideways and lowered into the engine well using a hoist. The rudder shaft has two pintles that engage with the gudgeons. The lower pintle has a longer pin than the upper pintle, so that it can be engaged first rather than having to try to line up two pintles with two gudgeons at the same time.

Once the rudder assembly is dropped into place it can be turned to the 0º amidships position, with the bottom part of the assembly sliding under a recess in the bottom of the transom. This recess serves several purposes: it provides an exit path for the stream from the propeller; it also provides an exit path for the outboard motor’s exhaust when it is in idle (when it is in gear the exhaust goes through the propeller and into the water); lastly, it provides a space for the rudder assembly.

The bottom part of the rudder assembly consists of the rudder blade case and the rudder blade. The case is a box, welded out of mild steel and galvanized, with its bottom and rear open and forming a slot from which the rudder blade protrudes. It is welded to the bottom of the rudder shaft (a steel tube) and reinforced using a triangular gusset. The gusset has a hole in it for attaching a lanyard by which the rudder assembly is hoisted out of the engine well. The sides of the box have specifically shaped cut-outs in them.

The rudder blade is made of a 3/4-inch (20 mm) piece of plywood sheathed in fiberglass and painted. Close to the bottom of the blade is a circular cut-out that is filled with a lead disk, to ballast the blade to counteract the buoyancy of the plywood and to exert a certain downward force when submerged. The top of the rudder blade is surfaced with epoxy that’s loaded with graphite powder, to create a hard bearing surface.

Rudder blade detent mechanism: roller guide and rollers

The rudder blade is joined to the rudder blade case using 4 rollers, 2 on each side, that are through-bolted to the blade and ride inside the cut-outs in the case. The arrangement of the rollers and the cut-outs acts as a detent: in order to get the blade to kick up the force acting on the front of the blade generated by an obstacle has to be more than 4 times the downward force on the blade due to gravity.

The lead disk is sized so that this force is significantly more than 1/4 of the force generated by drag with the boat moving through the water at its maximum speed. Once this initial resistance is overcome, the rudder blade kicks up rather easily. Once the external force acting on it is removed (because the boat is again in sufficiently deep water) it floats down into vertical position and the roller mechanism clunks into place. When the blade kicks up, it fits in the recess under the transom.

Rudder blade in kicked-up position

The only necessary precaution is to avoid running aground while moving astern: the rudder blade will not kick up backwards. Most of the time the centerboard will strike bottom first, because it hangs down lower, and will stop the boat, shattering if it has to, in which case it will be time to pull the remainder of the centerboard out of its slot on deck and to drop in a new centerboard. But if the centerboard somehow misses the underwater obstacle and the rudder blade doesn’t, then the rudder may suffer a bit of damage.

If the bottom is soft and the boat is moving slowly, it will simply stop with the rudder blade stuck in the sand or the mud. If the obstacle is hard or the boat is moving fast, the bolts holding the rollers to the rudder blade, which are designed to be the weakest element, will shear off and the rudder blade will drop off. Then it will be time to pull out the remainder of the rudder assembly and to jump down into the water (all 4 feet of it) to recover the rudder blade and the rollers. Then the rudder assembly can be put back together with new bolts. There is also the chance that the rudder blade will strike and damage the prop, in which case it will also be time to pull up the motor and replace the prop. In short, don’t run aground when backing up!

To summarize: the rudder assembly easily installed and easily removed when not in use and for maintenance. With the rudder assembly removed, all that remains in place are two gudgeons mounted to the back of the engine well. It doesn’t kick up unless it encounters a hard obstacle, with no amount of moving water able to displace it from vertical. Its action is fully automatic, never requiring any operator intervention. It provides for fingertip steering using a tiller because the rudder blade is balanced, with 1/3 of the area ahead of its axis. The use of the tiller makes it possible to use the simplest and most affordable kind of autopilot: a tiller pilot that clips onto the tiller. The tiller itself is of a telescoping type, with a handle that slides into its body, so that it isn’t left swinging about the cockpit when the boat is on autopilot.

After all of the various evolutions, I dare say that this rudder design is very close to final.

Monday, May 13, 2019

The Centerboard


Although the Quidnon blog has been quiescent for the past three months, there has been some good progress on completing the design, and I can now report these results and see what comments, ideas and suggestions emerge. It takes time to come up with simple and cheap solutions to complex and potentially expensive problems.

One of the problems that is now solved is how to provide lateral resistance with minimal complexity and expense. The initial concept included chine runners, which are narrow ledges that extended horizontally from the hard chines at which the bottom joins the sides, and two centerboards that hung down from wrist pins and extended from slots in the bottom in such a way that they would kick up into their slots when encountering an underwater obstacle.

The chine runners were discarded when it turned out that Quidnon’s hull, being quite wide in order to provide relatively spacious living quarters (it is, after all, a HOUSEboat), doesn’t heel enough to allow the chine runners to bite into the water. All the chine runners did was add some drag (and, of course, complexity and expense).

The kick-up centerboards worked well enough, but there is a basic problem with them: since they hang down from a hinge, they are deflected when moving through water, and this makes for erratic steering behavior. The deflection can be minimized by adding ballast, but this makes the boards too heavy. It is also possible to add tensioner lines fed to cleats that pop open when the boards hits an obstacle, but this adds complexity.

The problems with the original centerboard design didn’t end there. How does one remove them for maintenance and cleaning, and put them back in? If this required the boat to be hauled out, then that would invalidate the very important requirement that Quidnon must never need hauling out (haulouts are expensive!). The copper cladding can be cleaned with the boat hard aground at low tide and there is nothing else down there that should ever need attention. And so a plan was created for installing and removing the centerboards with the boat in the water with the help of a diver. But divers are also expensive!

And then another good question arose: why are there two boards? Well, the initial thinking went as follows. Putting a single centerboard along the centerline wastes precious living space in the middle of the cabin by filling it with a centerboard trunk. Moving it off to the side makes the design asymmetric, and that’s functionally unimportant but aesthetically unpleasing. Therefore, let’s have two of them. The flaw in this logic is that the aesthetic consideration matters not at all because the centerboard isn’t visible. Your heart is on your left and your liver on your right, but nobody will ever call you ugly because of that.

If two centerboards are too many, how about zero centerboards? Well, it turns out that having a centerboard is rather important, but only when the boat moves. It is especially important when motoring in and out of marinas, because without the centerboard the boat will drift sideways instead of turning within a tight radius. It is also important when motoring, especially upwind. It is sometimes possible to sail downwind without the centerboard, but that’s about it. But if the boat doesn't move (as houseboats often don't) then a centerboard isn't needed at all, and having one that's quick and easy to install and remove would be a bonus.

And so just one centerboard is both necessary and sufficient. It will be located off-center (to starboard) with the centerboard trunk located unobtrusively in the back of a settee in the salon, sandwiched between it and the water tank. (But we’ll still be calling it a centerboard because offcenterboard is not a word.) The centerboard trunk forms an L-shaped slot that extends from the deck all the way to the bottom (and does extra duty as a deck drain). To one side of the slot is a channel that stops short of the bottom and tapers in a specific way before it stops.


The centerboard is just a piece of 3/4-inch plywood covered with fiberglass for durability. A circle is drilled out of it near the bottom and filled with lead in order to make the centerboard heavier than water, but not much heavier. It doesn’t have to sink particularly aggressively; it just can’t float up. To one side of the centerboard, near the top, is screwed a cam that rides inside the channel on the side of the centerboard trunk. At the very top of the centerboard is a hole used to attach a lanyard by which the centerboard is retrieved. If the lanyard breaks, a boathook can be used to grab the board by the hole. The centerboard is sacrificial and designed to snap without causing damage to the hull. Making a new one is neither expensive nor difficult.


The centerboard will spend most of its life sitting flat on deck. When the boat is getting ready to move, it is installed by unceremoniously dumping it into its slot.


If there isn’t enough water under the boat it won’t go all the way down, but that’s usually not a problem. (You may need to give its lanyard a tug when backing out of a shallow berth, to keep it from catching on things.)


When the centerboard hits something underwater with the boat moving forward (as boats normally move) it deflects aft, but in order to do so it needs to ride up a bit, so that the cam moves up inside the tapered slot. It can stay in this semi-retracted state, bouncing along the bottom, while the boat sails or motors across shallows. This will slow the boat down a bit, but will also provide good steering because the boat will pivot around the board as it digs a shallow trench in the sand or the mud of the bottom.


It is not necessary to remove the centerboard when anchoring above the low water line with the intention of drying out at low tide because it will be forced up entirely into its trunk.

This completes the conceptual design of the centerboard; next on the list are: the rudder; engine mount; mast steps and bow structure. These have all been reworked, and I will be detailing the new designs over the coming weeks.

Friday, February 8, 2019

Frame Joinery Redux

Although most of the problems with hull structure have already been solved, there remained one problem that stood in the way of completing the design: how to join together the frame. It consists of 4x4 softwood (fir) timbers (3.5x3.5 finished size) combined into a box structure that reinforces the bottom the deck, the bow and the transom and provides support for mast steps. After working out a design that included a dozen different steel brackets that had to be custom-fabricated at considerable expense, I realized that I don’t like it at all: too complicated and too expensive. And so, as usual, I sat back and waited for some new ideas to filter in from the ether.

Eventually this happened. An unrelated project required me to build a rectangular frame by joining together some square cross-section sticks using L-brackets. To avoid the wood at the ends of the sticks splitting as I drove in the screws, I wrapped the ends using several turns of fiberglass packing tape. It worked just fine. The tape took up all the force that would have gone into splitting the sticks along the grain, and the resulting joins were impressively strong.

Transferred to Quidnon’s frame design, this technique will make it possible to assemble the frame using just 3-inch-wide perforated steel strips cut to two or three different lengths and bent to various angles. Some of the brackets will need to be bent to specific angles other than 90º, but this is not a complicated procedure.

The procedure for fabricating the frame now consists of the following steps:

1. Using a chop saw cut 8-foot 4x4 timbers to required lengths.
2. For each timber, shave down the first 6 inches off each end on all four sides using a planer.
3. For each timber, router off the corners on the first 6 inches on all four sides using a router.
4. Roll on a layer of epoxy to the prepared ends, wait until it “tacks up.”
5. Wrap each end in three layers of 6-inch-wide fibergass tape.
6. Saturate the tape with epoxy; let it cure.


Frame assembly then consists of matching up the timbers and the brackets and connecting them together by driving in a lot of self-tapping screws using a cordless drill. There is no need to worry about the wood splitting, and the resulting joints are strengthened by the fact that they are pre-stressed: the wood is compressed between the screws and the fiberglass. In a humid marine environment the timbers will gradually absorb moisture and swell, increasing the pressure on the fiberglass and the screws, holding them in place securely. (The choice of softwood for the timbers is critical: when hardwood swells, it generates enough force to burst fiberglass.) The strength of the joint is determined by the force needed to crush the wood fibers, which is somewhere around 6 times greater than the force it takes to split them along the grain.


There are still several more complicated pieces that will need to be fabricated: engine bracket, mast tabernacles, masthead fittings, tiller and keelboard hardware and bow rollers. These are all key elements of the design and there is no way to simplify them. But the frame joinery is now very well in hand and can be done cheaply using components that can be locally sourced in many places around the world.