Marine Russian Stove, Take 2

[Update: I added a schematic of the hot water plumbing system and improved the description of how it will operate.]

Thanks to all the feedback I received for the previous iteration of the design, it is much improved.

The basic goals of this design are as follows:

• The stove has to be cheap and easy to fabricate as a kit out of sheet metal stock using a plasma cutter and a brake.

• It should be easy to assemble the kit using a few hand tools: wrenches, screwdrivers and a pop riveter.

• It should be able to burn either wood or charcoal.

• It should also make it possible to fit a propane burner as an option. (Some marinas do not allow solid fuel stoves.)

• It should provide heat to a cooktop, a water heater and an air heater. Each of these may or may not be in use at any given time.

• It should produce negligible amounts of radiant heat (except from the cooktop, and only when it is in use)

A lot of people commented in favor of heating a thermal mass, and this is indeed a good idea. Thermal mass heaters, such as the traditional Russian Stove, use masonry to hold heat. But masonry doesn’t have a place aboard a boat, and hiding a few bricks inside a sheet metal stove won’t make much of a difference. However, there is one substance that is better than masonry at storing heat, and it’s free. It’s seawater. It takes 4.18 J/gK to heat seawater, while soapstone—the preferred material for solid mass storage—is only 0.98 J/gK, so its more than four times worse at holding heat.

Quidnon holds 5 tons of water ballast, and the best way to store heat aboard a Quidnon is to heat the ballast water to some reasonable temperature, such as 15ºC (60ºF). Running salt water through the water heater will cause it to crust up with salt deposits that can only be removed mechanically, using a grinder. It is much better to reinject heated fresh water from hot water tanks into the fresh water bladders floating inside the ballast tanks. This would also heat the surrounding ballast water, producing the same effect.

But this was part of the plan all along. The following realizations, however, are new, and demonstrate the power of the design process we’ve been following on this blog, where experienced people contribute many excellent ideas.

The first very important realization, thanks to Rhisiart, is that the stovetop needs to be directly above the firebox in order to produce sufficient temperatures for applications such as stir-frying and generating steam for the sauna (via sauna stones). But the stovetop doesn’t need to always be hot. When the stove is being used to heat the interior of the boat (via hot air) and/or to heat water, it should be possible to close off the stovetop using a sliding baffle.

The second very important detail, contributed by Jef, is that it is very important to be able to completely seal off the firebox from the interior airspace and to feed the fire by taking in outside air. I already knew how important this is: lighting a charcoal stove on board on a stormy night would sometimes send ash and lighter fluid fumes flying into the cabin. The trick was to catch lulls to light the flame, because once the draft was established wind gusts no longer mattered much.

This has prompted me to follow Jef’s advice and to add two air injectors. The bottom air injector is used for stoking the flame and can be driven by a small fan. Once the fire is burning, the top injector is used to produce combustion of the flammable gases emitted by the wood at just the right spot. The flow rate for the injector can be turned down, to keep a couple of hardwood logs burning all night, or turned up, to rapidly heat the stovetop and/or a lot of water.

Other parameters of the design were relatively easy to derive. A 3-inch flue is reasonable for a boat-based stove (I’ve used it successfully before). The cross-section of the flue has to remain the same both inside and above the stove. There is enough space available on Quidnon for a 16-inch-wide stove (plus a couple of inches all around for rock wool insulation and an exterior jacket made of either aluminum or stainless steel sheets pop-riveted together). Thus, the width (w) of the flue box inside the stove is 16 inches, and its depth works out to

πr²/w = 3.1415 * (3 / 2)² / 16 = 0.44 = 7/16 inches

The most common size of firewood is 16 inches long, so the firebox is 17 inches deep. It is reasonable to keep the profile of the firebox reasonably square, so it is 16 inches wide by 16 inches tall. The ash box at the bottom and the stovetop compartment at the top, above a baffle, bring the total height to around 30-32 inches.

The reason the section below the stovetop is taller than at first appears necessary is because of the threshold. Thresholds are commonly used inside stoves to keep in the hot gases, raising the combustion temperature and making for a more efficient burn. There are two thresholds: one in the firebox, and one below the stovetop. The front opening of the stove (which is fitted with a door that seats tightly against a gasket) is sized so that the top of the opening is just below the bottom of the threshold, to keep combustion gases from escaping into the cabin while loading firewood. The ash box is similarly sealed from the inside air.

There are two heat exchangers: air and water.

The simplest and cheapest heat exchanger design is one with hot flue gases on one side of a metal plate and the medium to be heated on the other. For the air heat exchanger, just as with the flue, it is important to maintain the same cross-section both outside and inside the stove, and a 3-inch duct is reasonable for piping hot air under the cabin sole and distributing it throughout the boat. This translates to the depth of the air heat exchanger also being 7/16 inches. It may at first seem strange that the cold air is pumped in at the top, since hot air rises, but this makes no difference since it then has to be forced under the cabin sole anyway.

For the water heat exchanger, the flow is much slower because of the very high heat capacitance of water, and matching the cross-section of the input and output pipes to the cross-section of the heat exchanger is unnecessary. Above the stovetop, the flue forms a square box, insulated on the front. It shares its back wall with the water heat exchanger box, which has a couple of nipples welded to it for letting water in and out.

It is a given that the water heater will generate some amount of steam, and this steam has to be released. It is also a given that quite a lot of the time the water heater will not be used, and the stove’s sole job will be to heat air. This will make it necessary to vent the steam and to let the heat exchanger stand empty.

For this, I am thinking of doing the following.

A demand pump set to 16 psi injects cold water from the fresh water tanks directly into the hot water tank until the air release valve located near the top of the tank starts spitting water and is manually closed. The air release valve is connected to a nipple located a couple of inches from the top of the hot water tank, leaving an air pocket at the top that allows it to operate as an expansion tank, absorbing excess pressure periodically generated by steam. The demand pump keeps the tank permanently near full and pressurized as water is drawn from it. So far, this is just a pressurized cold water system with a reserve tank.

When the stove temperature sensor reads above 80ºC, a second pump starts injecting water from the hot water tank into the top of the heat exchanger. This is not a demand pump but a simple circulator pump, and it doesn’t particularly care what pressure it’s generating (up to a point). The heated water drains out of the bottom of the heat exchanger and back into the hot water tank through a check valve. It keeps running until a temperature sensor in the hot water tank reads above 80ºC.

It is at that point—when the circulator pump stops running—that an interesting series of events has to unfold, because the remaining water trapped inside the heat exchanger starts to boil and generate steam. Steam pressure forces most of the water remaining in the heat exchanger down into the hot water tank. As steam pressure in the heat exchanger continues to increase, the pressure relief valve opens and vents the steam.

As steam is being vented, pressure in the heat exchanger falls below 16 psi but the check valve keeps water from being forced back up into the heat exchanger. The heat exchanger then stands mostly empty (if the check valve leaks a bit, the pressure relief valve will periodically produce puffs of steam) until the hot water tank cools down below 80ºC, and if at that point the stove is still above 80ºC the circulator pump starts squirting water into the heat exchanger again. After some amount of hissing, during which the heat exchanger generates steam, the hissing stops and water starts being heated again.

Marine Russian Stove

During the decade or so we have spent living aboard, we went through a succession of methods to keep the cabin warm during the cold months. On our first journey south, we cast off from Boston in mid-October, the day before the marina would have kicked us out because we hadn’t signed a contract for winter dockage. We progressed south rather more slowly than we had expected, and made it as far as Charleston in early December. There we decided to overwinter, and proceeded further south three months later. When we first set off, all we had on board was an electric space heater, plus a propane heater powered by 1 lb. camp stove canisters. We went through a large pile of these. The electric space heater only worked when we were tied up at the dock and plugged in to shore power. While under way, we tried to keep warm by burning propane. But propane generates a lot of moisture as it burns, causing the entire cabin—the clothing, the bedding, everything—to become dank, robbing the body of heat, while the moisture in the air condensed on the underside of the cabin top, causing it to literally rain inside the cabin. (There are few things more disagreeable than an intermittent cold drip on your head as you are trying to sleep.) When we got to Baltimore, we tied up at a marina to which I had previously arranged to have shipped a propane-fired Cozy Cabin Heater. It was designed to be plumbed to a 20 lb. propane tank, and included a flue, thus solving the moisture problem. I installed it using the materials on hand and life got significantly better. Once in Charleston, where we overwintered, we used this heater along with the electric space heater, and the cabin stayed comfortable.

Eventually we got back to Boston, by which point the Cozy Cabin Heater died, as had the company that made it, and hunting down replacement parts for it turned out to be a nightmare. This is not at all unusual: most of the equipment manufactured for the recreational marine market is shoddy, overpriced and falls apart rather quickly. At that point, as part of a thorough refit, I replaced it with a Tiny Tot charcoal stove, made by a tiny company somewhere in Michigan. The heat it delivered was intense and very dry, and kept the cabin toasty all by itself on even the coldest nights with no condensation problems. But we had to get up every 2-3 hours to add 5-6 charcoal briquettes. Solid fuel stoves were forbidden at the marina where we stayed, but nobody noticed. Also as part of that refit I insulated the entire cabin with two layers of radiant barrier, ½ inches of Pink Panther foam insulation, another layer of radiant barrier and a layer of fancy 1/16-inch varnished cherry plywood with oak trim. This made a huge difference: there were no more condensation problems and the cabin felt warmer than one would have guessed by looking at the thermometer. The one remaining problem was the cabin sole: there was no way to insulate the bilge and it was still cold. In spite of putting down rugs everywhere possible, it was difficult to keep our feet warm.

We were about to set off sailing again when we became pregnant and had to “upgrade” to a larger boat. The reason “upgrade” is in quotes is because we sold a very good boat—Hogfish, the eminently serviceable, versatile and fun 32-foot sharpie custom-built by Chris Morejohn—and bought an unwieldy, boring maintenance nightmare that is the typical commercially built yacht—a 36.5-foot Pearson. Its only real selling point is that Pearson made a mistake and made the fiberglass of the hull ridiculously thick, thus making it fairly indestructible. Over the five years that I owned that Pearson I came to genuinely detest it. Rest assured that I will never buy another commercially built production boat again, having learned firsthand all the different ways in which they are crap. As far as I am concerned, it’s either going to be a Quidnon—or a nice homestead. But if all goes as we expect, I’ll have one of each.

The Pearson came with a very strange piece of equipment: a Newport evaporative diesel heater. It used a little electric pump to squirt diesel oil into a bowl, and it was your job to get it burning. This involved tossing in some tissue paper soaked in diesel, lighting it on fire, and using a little electric fan to vent the fumes and fan the flames until the bowl of oil heated up enough to start evaporating and burning on its own. When everything was working as it should, it produced a pretty-looking warm glow, much like a fireplace. The rest of the time it produced prodigious amounts of soot and made the cabin stink of diesel oil. And the once in a while—invariably on a cold and stormy night—it would blow out, and coat the walls of the cabin, and everything inside it, with a fine film of smelly, oily soot. We used that heater for one winter, then gave up on it and let it sit, unloved and unused. As far as the rest of the boat, we did get some use out of it. I moved it south one summer, single-handing all the way down the coast, then had my family fly down, and there it stayed, at the dock, until we sold it. I didn’t enjoy sailing it; it sailed like a pig, with a strange corkscrew motion and a jarring “stomping on the breaks” effect at every other wave as the Pearson buried its fat snout in it. Well, that’s what you get with a hull that’s shaped like an endive. Its best feature by far was the heads: it had a full-size shower stall. Its second-best feature was the galley—once I tore out and rebuilt half the cabinetry.

Another problem with an endive-shaped hull (and most production cruising sailboats are, unfortunately, shaped like that) is that is almost impossible to insulate. On Hogfish, the sides were made of flat plywood sheets, curved in a single direction, and this was easy to insulate by adding flat slabs of foam. This is also going to be the case with Quidnon. Also, on Hogfish the sides were accessible, while the Pearson the cabin was a mess of fiberglass forms, one wedged into another before the deck got screwed on. (Yes, the deck was screwed on, not bolted on, using sheet metal screws bedded in epoxy; the wonders of commercial boatbuilding never cease to amaze!) Clearly, the designer had spent zero minutes thinking about how this hull could ever be insulated. Thus, the Pearson stayed uninsulated, and the cabin felt cold no matter how many electric space heaters we had going. We used a thick rug in the salon and electric blankets under all the mattresses, and that helped. We also taped bubble wrap under all of the hatches and insulated the companionway hatch as best we could.

As an aside, the economics of unique, versatile, custom-built boats like Hogfish, and like Quidnon is going to be, and sloppy production boats like the Pearson are very different. When I put up Hogfish for sale it sold almost immediately, and I doubled my money on it. If I hadn’t accepted the first offer (which I did because the buyer matched my asking price) there would certainly have been a bidding war. The Pearson stayed on the market for six months and eventually sold for a miserably small amount of money, because there is a glut of very similar boats sitting on the market forever, unused and unloved. The closing date for the sale fell on my birthday, which I took to be a sign that Neptune had taken pity on me. This contrast hints at what the situation will probably be like with Quidnons, once there is some number of Quidnons floating about. There are likely to be bidding wars for any of them that come on the market, be they bare hulls or be they finished boats with all of the equipment and amenities installed.

Getting back to the question of how to heat the cabin, our plans for Quidnon is to make it very comfortable and cheap to heat. Last week, Chris Raine asked a profound question: “Will this houseboat also have a Русская печь?” This question, I thought, requires an equally profound response, so here it is. What follows is an excerpt from my book Shrinking the Technosphere.

The design of the Russian stove is several centuries old and seems to have emerged soon after the spread of firebrick, which is a formulation high in silica that is less susceptible to spalling when heated repeatedly. It is a massive masonry structure with its own foundation. At its center is a vault with an arched ceiling and a flat floor, often high enough for someone to squat inside. Fire is set inside the vault, far inside the stove. At the front of the stove is a flue, which includes a dogleg with a gate that is used for hanging meat and sh for smoking. Right back of the flue is a threshold that protrudes down from the top of the vault, holding hot combustion gases inside the innermost part of the vault, resulting in better heat transfer. The top of the vault is filled with solid fill and covered over with a layer of brick, forming a platform, and a straw-filled mattress, which is often big enough to serve as a bed for an entire family of five. Between October and May, when the stove is red twice a day, the temperature of the platform stays at a constant, comfortable 25–27ºC (76–80ºF). During the hot part of the summer, when the stove is not red because cooking is done at an outdoor hearth, the stove provides a cool place to sleep.

The outer wall of the stove has several niches. They improve heat conduction from the stove to the air in the room and are also used to dry clothes, herbs, mushrooms and berries, to keep food warm and to provide a place for the samovar, which boils water for tea. The firebox of the samovar, typically stoked using pine cones, exhausts into the flue of the stove. Under the stove is a space that is used to store firewood and can be a warm place for animals to sleep. The stove can also be used as a sauna—by sitting cross-legged inside the vault when it is relatively cool.

The Russian stove includes an entire dedicated set of utensils that are specific to it, each perfected over the centuries to have the largest possible set of functions. Food is cooked in clay pots and in cast iron skillets that lack a handle. The pots are placed inside the stove using stove forks, which come in three sizes and grab pots by the neck, while the bread and the skillets are moved about using a flat-bladed wooden spade, similar to the paddles used to handle pizza.

For the sake of comparison, let’s consider what you’d have to shop for if you didn’t happen to have a Russian stove. To heat the house, you’d need to buy a furnace and either install an oil tank or hook the house up to a gas main. Then you’d need to construct a way to distribute the heat, through either forced air or baseboard heating, and this involves installing lots of either ducts or pipes. You could also install a modern, energy-efficient wood stove, but then the bedrooms would be cold, so you’d probably run out and buy some electric space heaters and, to keep the beds warm, some electric blankets. To cook food, you’d need to buy a cooking stove with an oven, either gas or electric, a toaster and a microwave oven. You’d need a separate smoker for smoking fish and meat, plus some drying racks for drying things. Or you could just get rid of all this expensive, short-lived junk and render yourself naturelike by building yourself a Russian stove and using it in place of all of the above.

From Shrinking the Technosphere, p. 139-40

So, how does one adapt the Russian Stove concept to a boat? Obviously, placing a massive masonry structure on board is out of the question. But after giving the question some thought I found ways to provide for most of the rest of its uses, including all of the following, using a relatively lightweight structure made of sheet metal:

• Keeping the cabin warm and providing warm, dry places to sleep and sit
• Heating water for showering, bathing and washing and to keep water ballast tanks from freezing
• Cooking
• Making steam for sauna
• Generating electricity
• Drying things

There will be two identical stoves—one in the galley, one in the heads/sauna—that will burn wood, charcoal or propane (since some doing like having to stoke a stove, and some marinas forbid the use of solid fuel). To burn propane, the ash box is replaced with a propane burner; the firebox can then be repurposed as an oven and used for baking or broiling. But when cruising or overwintering along wooded shores propane may be hard to come by while firewood is likely to be plentiful and either cheap or free for the taking, and so the option to burn wood is very useful.

Above the firebox is a stack of three heat exchanger compartments. Flue gas from the firebox can be sent through any of them using diverter valves. Right above the firebox is the water heat exchanger; next is the air heat exchanger; and at the top is the hot plate used as a cooking surface. The flue gas is then discharged into an 10-foot smokestack that penetrates the deck and rises above it, to produce plenty of draft. The sides and the back of the stove are double-walled, with a layer of rock wool between the walls for insulation.

The back wall, which is in contact with the hot flue gas, is especially well insulated, with a layer of aluminum flashing sandwiched between two layers of rock wool to provide a radiant barrier. A patch of the back wall is left uninsulated; there, a thermoelectric generator module is attached directly to the steel plate that is contact with the hot flue gas. The cold side of the thermoelectric generator is cooled by circulating ballast water through a water jacket. The two thermoelectric generators will provide a total of 100W of DC current—50W on each stove—and also keep the ballast tanks from freezing.
In the heads the hot plate surface has a pile of sauna stones attached to it using a stainless steel mesh. Having a sauna on a smallish sailboat may seem like an extravagance, but the Finns, the Russians and many others would disagree. I am sure that anyone overwintering on a Quidnon would value having a sauna on board.

Since most people prefer to cook with propane rather than fire up the stove for that purpose, in the galley the hot plate will usually have a propane cooktop placed over it. Above it is an exhaust hood vented to the outside; in the relatively small space of the cabin, it is essential that cooking smells not be allowed to permeate the cabin.

Space heating is via warm air. A circulator fan takes a mixture of outside and inside air and pushes it through the air heat exchanger. The output is injected into a network of ducts and plenums under the cabin sole which distributes the heat evenly throughout the cabin.

The plenums can be adjusted for optimum heat distribution and to suit the preferences of the occupants of each cabin and berth. Some of the warm air is sent under all of the berths, to keep the bedding warm and dry. In addition, warm air can be sent into the cockpit lazarettes and the cockpit well, to keep the cockpit warm and to provide warm places to sit while sailing. To keep the heat in, the cockpit can be enclosed using sliding window panels along the sides and a transparent vinyl curtain across its aft end.

The water heat exchanger is used to heat up water in the hot water tank used for bathing, washing and showering. The hot water tank is fitted with an alarm: when the water temperature rises above 80ºC, an alarm sounds, informing the stoker that it is time to turn the diverter valve on the water heat exchanger to off and to turn off the hot water circulator pump.

There are several good reasons why there are two stoves instead of just one:

• When overwintering on a Quidnon in the far north, hauled out on ice or on shore, and temperatures drop below -20ºC, both stoves would need to be fired in order to to keep the cabin toasty.
• During the warm and hot months in the temperate latitudes, and in the tepid ones, people still want hot water to be available, but lighting the stove in the galley would make it uncomfortable to be in, but the stove in the heads can be used instead.
• Having a large wood-heated cooking surface is very useful when preparing large quantities of food—whether to feed large groups or to process and lay up supplies for the winter—but the one in the heads is occupied by a pile of sauna stones.
• Having a pile of hot sauna stones to throw water on is the excellent, traditional way to generate steam for a sauna.

Above deck, one more flue gas diverter and heat exchanger can be installed to supply heat to a hot box that can be used to dry various things: mushrooms, salted fish, herbs, fruits and berries, clothing and footwear, etc. The hot boxes—one for each stove—can be made in one of two ways: as an easily assembled temporary installation, or as a permanent fixture attached to the bulwarks. In either case, the hot boxes provide additional warm places to sit while out on deck.

Two things need to happen in order to make the Marine Russian Stove a reality. First, with your help, I hope to sanity-check the concept and see if I made any mistakes or omissions. Second, if the concept is sound, comes the step of doing the math and producing the mechanical drawings, and if any of you are knowledgeable about stoves and heating system design and have the interest, I would welcome your input.

Specifically Useful or Generally Useless?

I once made a cockpit awning. It was a fiberglass-over-plywood affair. Not only was it a cockpit awning, but it also could have been pressed into service as a mediocre paddleboard, a bus shelter for small children and/or midgets, a roof for a tiny gazebo, a protest sign, a miniature frog pond and, of course, a planter. It turned out to be a universally useful/useless piece of crap, depending on how you looked at it.

It started well. I used 1/16-inch Luan for the top and narrow slats of 1/2-inch for the frame, which I cut to gentle curves that made the top into a cold-molded conic section with just a tiny bit of spherical distortion for added stiffness. I filleted the inside joints, sealed the plywood with epoxy, fiberglassed and faired the top… and then I tossed it. Actually, I gave it to some artists, thinking they might use it for some sort of art installation. It didn’t make that good a cockpit awning: too heavy, too difficult to mount securely, plus it added too much windage aft. I didn’t think it would survive a hurricane (unlike the hard dodger I made earlier, which survived passing close to the eye of Hurricane Matthew with no damage).

I did most of the work on sawhorses on the floating dock at the marina. All of the other marina denizens, who mostly just sat on their boats and got drunk, were rather enthusiastic, and a few even tossed some business my way, fixing stuff on their boats. But the marina staff were less enthusiastic, talked about made-up “customer complaints” and eventually exiled me, together with my sawhorses and tools, to a windless, gravel-paved back lot, where I worked roasting in the sun. The hostile work environment probably had something to do with the project’s ultimate failure, but mostly I blame myself, for not spending enough time on the design phase.

There are plenty of designs that are specifically useful for their stated purpose, but are otherwise completely useless. In this category are special-purpose tools, like the egg slicer or the lemon juicer. Yes, they make short work of slicing hard-boiled eggs or juicing lemons, but beyond that they just add clutter. In a pinch, both can be used to prop open doors and windows, and the egg slicer makes a tiny out-of-tune harp, in case you are ever in need of a really pathetic sound effect. But that’s it.

Lots of boat designs are the same way. Most yachts, for instance, are only useful for showing off how rich the owner is (or was before he bought the yacht). Sporty ones are only good for pounding across the seas slightly faster than the competition and in great discomfort. Shantyboats, sailing scows and single-wides floating on barges or pontoons are cheap to maintain and comfortable to live aboard, but they give harbormasters and marina managers the vapors because they don’t look sufficiently yacht-like.

In setting out to design Quidnon, my objective was to create something sufficiently versatile to make it one’s single most valuable possession. It is a houseboat, a motorboat, a sailboat, a party boat and a beach house. It can handle deep water as well as the shallows. This level of versatility calls for some amount of compromise, and the question is, How much compromise is too much? “Better is the enemy of good enough” is a good saying, but how does one go about determine what’s good enough? And when should the alarm go off to indicate that a design has cross the line between generally useful and generally useless?

This requires lots of careful thought, and that is why the design phase of the Quidnon project is taking a few years rather than a few months. A typical boat for a rich guy to show off on or for a charter fleet is relatively easy to design. The design of a very unusual boat that will be useful as a home and a magic carpet to many different kinds of people all over the planet is far more challenging. And yet I think we’ve come quite far. A dozen or so well-defined design tasks stand between us and a set of plans from which we can build the first hull.

I know that are number of you are waiting for that moment. I am sorry to make you wait, and to make up for that somewhat I want to share with you the complete list of tasks to be completed before we can produce the design plans. Very importantly, these tasks need to be thought through before they can be drawn. As they say in the world of software, “with enough eyes, all bugs are shallow.” So far, this has been the case with Quidnon as well: over time, good ideas have been added and bad ideas eliminated simply through knowledgeable, thoughtful people asking good questions. If a question doesn’t get asked, a bad idea can stick around for a long time.

A case in point: Willie, a marine engineer who recently joined the project, asked a simple question: Why are there twin rudder blades? The boat doesn’t heel much, so angling the rudder blades doesn’t add much to the performance. The Ackermann steering geometry requires a complex (and expensive) linkage. And accommodating the twin rudders complicates the hull shape at the transom. Why not have one rudder, located amidships, where it can deflect the prop wash, for better maneuverability?

Some of this logic also applies to the twin keelboards. If the boat only heels 12º even when pressed hard (as shown by the scale model) then angling the boards has little benefit. But the second board does add complexity and cost; why not get rid of it and just have a single centerboard? It can be mounted off-center, as in some of Phil Bolger’s designs, to keep the center of the cabin unobstructed by the centerboard trunk.

And the answer is, I initially added the twin keelboards and rudders before I knew how little Quidnon would heel, and I didn’t revisit the question because until recently nobody had asked it. So, please ask! With that in mind, here are the known tasks to work out.

• Add a small deck arch at the bow to serve as a mast support

When the masts are taken down, they fit within the overall length of the boat while sitting on the deck arches with the sails (along with spars and battens) slung below them. But the masts are unsupported at the bow. Adding a post at the bow would preclude a boarding ladder from being deployed off the bow. This is useful when docking bow-to (to pick up or drop off passengers quickly), when nosing up on a beech or to an ice floe, etc. The arch should be skinny so as to not obstruct the view forward. And it should not incorporate vents, as do the other two deck arches, because there is often too much spray at the bow that would make it through. Ventilation for the U-berth will need to be provided in some other way, such as through airducts run under the cabin sole.

UPDATE: In response to this, Matt suggested that the mast tabernacles incorporate shelves to support the masts. This is a very good idea. The foremast is close enough to the bow so that this change would make no difference. Mast shelves on the mainmast would be useful too: when the mainmast is first lowered down and the tabernacle hinge pin removed, the forward end of the mast needs to rest on something before it can be pulled forward. The mast shelves should extend aft of the mast tabernacle hinges so the masts can rest on them as soon as they are unhinged.

• Add dinghy forks aft

This is a relatively small detail, but important. There is ample room for storing multiple dinghies on deck, but it is often helpful to be able to deploy a dinghy quickly. Setting a dinghy upside-down on dinghy forks that slide out from the transom and lashing it down securely is in many ways optimal, and in my experience better than hanging the dinghy from dinghy davits so that it rocks, accumulates spray and rainwater and blocks the view aft. The dinghy forks can be used as dinghy davits when Quidnon is at anchor or at the dock, just to lift it out of the water, to keep it from accumulating marine growth and to give would-be dinghy thieves second thoughts.

• Add skids to the bottoms of keelboard trunks

Having straight skids is useful in a number of cases, such as rolling the boat ashore over round sticks and dragging it onto and across ice. If one of the keelboards is eliminated, there will still be two longitudinal full bulkheads that can be extended below the bottom to form the skids. The bottoms of the skids will need to be fiberglassed heavily and finished with epoxy thickened with graphite powder to provide a durable, low-friction surface.

• Finalize design of sliding doors

There are a few places where two-panel “Star Trek” sliding doors (minus the silly swish-swish noise) make a lot of sense. We already have a good design that uses counterweights on loops of cable to keep the panels from sliding open or closed as the boat rocks. It just needs a couple of tweaks. The main one is to have two counterweights—top and bottom—to compensate for angular momentum.

• Design stoves for heads and galley

The two stoves can be identical. They need to be able to burn propane, wood or charcoal. When burning propane, burners are inserted into what is normally the ash pan; the firebox can then be used for baking or broiling. The top of the stove is a cooking surface for the galley stove and a rock heating surface (to make steam for the sauna) in the heads. There need to be two thermostatically controlled louvers to divert flue gas flow to two heat exchangers. One heat exchanger is air-to-air, the other is air-to-water. The hot air is piped around through ducts under the cabin sole and to the cockpit well, for heating. The hot water is piped through an insulated hot water tank, to be used for washing and bathing. In freezing weather, some of the hot water needs to be piped to the water ballast tanks, to keep them from freezing.

• Rework joinery to use “screw and glue” rather than “mortise and tenon”

The scale model, and the earlier plan, used a lot of mortise and tenon joinery. It worked quite well in some places and less well in others. Specifically, it worked well for orthogonal joints and badly for joining elements on a curve. And it suffered from three major overall defects: 1. because the joints had to be kept a bit sloppy to make assembly possible, it soaked up a lot of epoxy, adding weight and expense; 2. it turned out to be rather difficult to calculate the strength of these joints; and 3. a lot depended on how carefully the joints were filled with epoxy, leaving open the possibility of voids that would concentrate moisture and cause rot and in pinholes that would produce small leaks. For all of these reasons, we decided to use a much simpler joinery technique of using square or beveled fir sticks and screwing and gluing the plywood panels to them. This technique is time-tested, the pull strengths of fasteners and the holding power of epoxy joints are both well known, and the skill level required to achieve good results is quite low. But quite a bit of structural analysis needs to happen in order to determine the appropriate sizes and spacings of screws.

• Rework the shape of the bow and the transom

With the twin rudders gone, the shape of the transom is simplified. Previously, the bottom, where it meets the sides of the transom, had to be angled; now it can only be curved in one direction: fore-and-aft. The bow needs to be made deeper in order to compensate for the loss of some 3 tonnes of fixed ballast aft by adding a shallow stem to it, as I explained in a previous post. The addition of the stem will also help sweep aside floating debris and bits of thin ice. The exact shape of the bow will be determined by running Orca3D hydrostatic simulations, to make sure that the boat sits on its lines.

• Rework bow construction technique

This didn’t work out so well on the scale model because the curves are too tight to be cold-molded. I ended up having to steam-bend plywood, which is not something we should expect Quidnon assemblers to be comfortable doing. Plan B is to use a single layer of 1/8-inch plywood to create the shape, then use it as a male mold to lay up as much fiberglass as needed to give it the necessary stiffness and strength. On the other side of the 1/8-inch plywood will be a lattice of thicker plywood to support the shape from the inside.

• Rework sheer strip assembly, hull and deck joints

A major problem when assembling the scale model had to do with fitting the sheer strips, which were two layers of plywood. At least 3 layers of 1/2-inch plywood will be needed for the full-scale build. The holes for the deadlights didn’t line up and prevented the sheer strips from developing a smooth curve. It took a lot of clamps to keep it from becoming lumpy. So, the revised plan is to make the deadlight holes using a hole saw or a jig saw and a router post-assembly. Also, after a bit of math it turned out that the deck-to-sheer strip and sheer strip-to-topside joints needed reinforcement. The simplest way is to use perforated aluminum angles rolled to the right and curve and attached using stainless steel mechanical screws with fender washers and nuts. That’s a lot of hardware, but deck-to-hull joints are critical and notorious for developing problems.

• Rework the rudder to use a single, central rudder blade

The rudder blade assembly can be tucked under the transom into the recess between the engine well and the transom that is directly below the gas tank and the propane locker. The recess is already there so that the back of the engine well doesn’t catch waves or prop wash from the motor. The entire Ackermann linkage goes away (along with several thousand dollars’ worth of expensive hardware). Some amplification of the tiller angle using an adjustable linkage between it and the telescoping tiller extension may still be required to keep the useful swing range of the tiller inside the cockpit.

• Convert inboard sides of keelboard trunks into full-height, vertical, longitudinal bulkheads, then get rid of the port keelboard and its keelboard trunk.

This was a major area of concern. There is a lot of side force on the keelboard trunks from both the keelboards and the mass of the water ballast. The longitudinal bulkheads will have openings in them through which to access the pilot berths, which are on top of the ballast tanks, and the sides of these openings may need to be reinforced with vertical ribs.

• Create plumbing, electrical and air duct schematics

The plumbing schematic exists; the electrical schematic needs to be created. The routing for all of them needs to be laid out and components selected.

• Design engine mount

Similar engine mounts, in which the motor slides up and down instead of tilting, exist for catamarans, so it may be possible to repurpose or borrow an existing design.

• Complete design of standing and running rigging

The standing and running rigging for the sails needs to be tested on a physical prototype at 1:5 or 1:4 scale to work out where to place the blocks, etc. Of specific concern are the details of the mast parrels, the placement of halyard and downhaul for optimum sail tension, and the placement on boom and battens of sheets and reefing lines. Take-up spools for running rigging (which will live under the cockpit well, above the chain in the chain locker) need to be designed as well.

This is the list as it stands at the moment. A few more items will probably need to be added as we move along. If you have the time, the skills and the inclination to tackle some of these, please let me know; we are, of course, looking for more engineers to join the team. The work is on a volunteer basis until the project reaches the equity crowdfunding stage.

If any of this brings up questions in your mind, please ask! That’s the main purpose of this exercise—to see if anyone can poke holes in our plans, or open us up to ideas we haven’t thought of or considerations we haven’t been aware of.