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. Kits will start at around $50k (USD). The design has been tested in simulation and prototype; full-scale production will begin next 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.