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.

Friday, October 5, 2018

Coppered Bottom is a No-Brainer

The last post on the Quidnon blog attracted some attention from various places around the net. One in particular—the forum Sailing Anarchy—attracted over 400 visitors. I followed the link and tried participating in the discussion.

The sailing anarchists just couldn’t wrap their heads around the concept of a houseboat as a lifehack that lets one avoid getting wiped out by exorbitant real estate prices and rents. Well, I’ve said this many times before, but I’ll say it again, briefly: in the US, housing is a racket, on par with other rackets, such as health care, higher education, national defense and quite a few others. The very lightly regulated recreational vessel space offers a wonderful opportunity to escape the landlubber debt trap.

The sailing anarchists also couldn’t accept the idea that it is better to build a boat from scratch, at considerable expense, than to buy an existing, used boat, many of which can be had for very little money. The problem there is that none of the existing boat designs fit the bill. Sailboats are either big and unaffordable or small and too cramped. Powerboats with accommodations for a family are also too expensive, both to own and to move from place to place because of exorbitant fuel bills. Houseboats are generally dock-bound and not seaworthy in any sense.

Some anarchists thought that the Junk rig wouldn’t work well. Little do they know that the Junk rig is one of the oldest and most successful designs in the world that has stood the test of time, providing low-cost propulsion and ease of handling for more centuries than any other. Some thought that the boxy hull shape was unstylish, ugly and simply wrong, unaware of the fact that sailing barges, scows, cargo lighters, dhows, bateaux and junks of similar lines had been the staple of coastwise navigation around the world throughout the age of sail.

I presented my list of requirements which Quidnon must fulfill, but which no other boat does, to no avail. Apparently, these anarchists are rather closed-minded. Not a single comment they made was on target. But one valid question did come out of the discussion: Why cover the bottom with copper sheet when bottom paints are available. Since this is an easy question for me to answer, and since the answer is instructive and demonstrates the type of thinking that informs the whole design, I will answer it.

Quidnon’s bottom is 16 by 36 feet, or 576 sq. ft. The bow, transom and sides below the design waterline add an additional 208 sq. ft for a total of 784 sq. ft. Roofing copper comes in 4x8-foot sheets, or 32 sq. ft. Dividing one into the other gives us 25 sheets. 16-gauge (1/16-inch) copper sheet is currently priced at $91.29 per, for a total of $2,282.25.

This may seem like a considerable expense, but now let’s consider the cost of bottom paint. After much experimentation I settled on Interlux Micron CSC Ultra as the longest-lasting paint. It costs $209.99/gallon and its datasheet claims that a gallon of it covers 439.7 sq. ft in a single coat. The manufacturer recommends 3 coats and a minimum of 2. This gives us 784 sq. ft times 3 coats divided by 439.7 sq.ft/gallon, giving us 5.3 gallons or $1,123.

Note that the paint only works for about a year; after that, the bottom starts growing slime, then sea grass, then barnacles and mussels. If you don’t plan on going anywhere, then you can just let your boat turn into a floating island festooned with seafood. But the need to move may arise suddenly: the marina may close because of an approaching hurricane and kick everyone out; your job situation may require you to move your floating home to a new location; a shortage of money may require you to give up the slip at the marina and take up life at a mooring or at anchor. With a neglected, painted bottom the prerequisite to moving is an expensive and lengthy (3 days at least) haul-out which includes hiring a Travelift and someone to pressure-wash and paint your bottom (unless you yourself enjoy spending your days with a roller, wearing a bunny suit and a respirator, and being exposed to toxic fumes anyway). Haul-out and bottom painting costs vary, but you generally end up spending upwards of a thousand dollars, and if you want your boat to be able to move effectively, you need to do this every year.

And so by going with bottom paint instead of copper sheet you will save $2,282 minus $1,123 in construction costs, or $1,159. But every year thereafter you will spend a minimum of $1,123 + $1,000 or $2,123 in maintenance costs. Over the 30-year expected lifetime of the boat, this will amount to as much as $60,000. Compare that to copper sheet: yes, you will pay extra up front, but thereafter all you will need to do is a semiannual cleaning: find a sheltered, shallow spot that dries out at low tide, anchor, wait for the tide to go out, and then take a scraper on a long handle, a roofing spade or a similar hand tool and scrub all of the copper you can reach. The seafood you can’t reach will be crushed and fall off by itself. If that’s still too much work, then you can hire a diver to scrub the bottom for you while the boat sits at the dock. This service generally costs only a few hundred dollars and can often be done on short notice—when you find out it’s time to move.

Attaching the copper to the bottom is slightly technical but not particularly difficult. The bottom is made up of 3 layers of 1/2-inch plywood screwed and epoxied together. Fiberglass matt is then nailed to the plywood using bronze annular nails and saturated with epoxy. The matt is then covered with 3 layers of fiberglass cloth, leaving an epoxy-coated surface, tipped off with a soft brush to make it perfectly smooth. The task of attaching the copper sheet is then as follows:

1. Thoroughly abrade the epoxy on the bottom with 100 to 200-grit sandpaper using a rotary sander.
2. Clean off sanding residue using denatured alcohol. Be sure not to leave any fingerprints.
3. Thoroughly abrade one side of a copper sheet with 300 to 600-grit sandpaper using a rotary sander.
4. Degrease using trichlorethylene.
5. Rinse the copper sheet in one of two solutions for 1-2 minutes. Option 1: 6 parts copper chloride, 30 parts 70% nitric acid; 200 parts water. Option 2: 25% aqueous solution of ammonium persulfate.
6. Rinse with distilled water; let dry.
7. Coat the bottom evenly with epoxy and apply the copper sheet prepared side down. Use cotton gloves when handling the copper sheet to avoid contaminating the contact surface.
8. Cover the copper with polyethylene sheet, then weigh it down with sandbags until the epoxy has set.

Why don’t other boatbuilders use copper cladding for the bottom? Well, it used to be a popular option during the age of sail. Ships were periodically run aground (careened) to have their bottoms scrubbed. But ships now use powerful bottom paints (illegal for use on smaller recreational boats) while for smaller boats copper is simply not an option. Look at the bottom of just about any commercially produced boat. It is made up of compound curves, and it is an expensive proposition to make copper sheets take up compound curves. Add to that the fact that most commercially produced recreational boats are made of fiberglass and vinyl rather than epoxy, and these don’t provide a good substrate for attaching copper sheet. Quidnon’s bottom is curved (slightly) in one direction only—fore and aft—and can be tiled with sheets of copper: 4 sheets across and 5 sheets lengthwise, for a total of 20 sheets with almost no scrap.

There is nothing to stop anyone building a Quidnon from deciding to use traditional bottom paint instead of the even more traditional copper sheet, but the decision to use copper appears to be a no-brainer: lower costs, no need for haul-outs and time spent on the hard in a boatyard and generally more flexibility.


  1. Very good Dmitry! There's also the issue of all popular anti-fouling paints being a major pollutant in waterways…

  2. re:
    Copper plate

    We used C280 'Muntz metal' copper alloy plate in decorative sculptures. It anneals beautifully, and weathers consistently. All our sculptures are inland and above sea-level (so far), so we cannot contribute our experience to constant-immersion such as Quidnon might require.

    Which copper alloys are you testing?
    Which adhesives?

    Velocities should not be a concern while the houseboat anchors in rivers and estuaries. However, oxygenation may accelerate stripping of the protective corrosion film.

    At houseboat speeds == <6-knots ? == oxygenation probably has little-to-no galvanic opportunities due to cavitation caused by velocity. However, directional forces come on play, with parallel slip the least intrusive. Mooring or moving with the water flow suits this project; counter-flow creates additional opportunities for protective film reduction. Winds opposing water flow may impact velocity temporarily; at that point, plate thickness adds durability at the cost of freeboard, maneuverability, and initial construction expense. Adding durability and its costs may deter budget-conscious builders, leading some builders to eliminate essential structure and scantlings. The potential for the inevitable resultant bad-press needs to be addressed during the publicity prior to releasing the finished plans. Agreed?

    We are interested in Quidnon for its low-cost low-impact manufacturing by untrained hands, primarily owner-builders. The copper alloy type will depend on cost and availability. If the appropriate-alloy-for-use is only available on a different coast or different continent...

    1. The copper that's the most economical and will last the lifetime of the boat is 16-gauge roofing copper. The adhesive will be the same epoxy used to laminate the hull. I've looked carefully at System 3 and it seems to be a good fit for the job. The other considerations you bring up don't matter much.

    2. Dimitry,
      Partway through an 8-year Pacific circumnavigation aboard my 31-foot, backyard-built trimaran, Celerity, I tired of beach bottom jobs and coppered the keel using small boatnails and Sikaflex adhesive caulk. Saved a fortune and never painted below the hull again. -RWT

  3. Seems to me the seams are the weak link. The exposed copper bottom will oxidize and creep under the seam adhesive. Any chance of brazing or soldering the seam?

    Everyone in my area, and I mean everyone, has a camper/RV. All I hear about from them is how the place they want to go is booked out a year or two and when you get there it is row after row of campers/RVs and invariably their neighbors are noisy A-holes. Also the cost is hundreds of dollars a week end.

    My electric sternwheel pontoon boat can go anywhere up and down the willamette valley, poking into the many sidings and tributaries, spending the nights in the most magical spots all for free, well except for the $2 or $3 dollars it costs to recharge the battery bank after a long weekend. Almost never see anyone else out there.



    1. The copper develops some surface oxidation and pitting over the 30 or so years the boat will stay in service. I haven't heard of any issues of oxide getting through the epoxy and damaging the seams.

    2. You might want to give this a try:

  4. I have been following the project from two years or so. And i really believe that is a good project with really good potential when fuel starts to get expensive (And everything becomes expensive the next year)

    And I know you're an engineer like myself Dimitry, and maybe you think that letting a design speak for itself is a good marketing strategy, but it is not. And what worries me about Quidnon is not the design itself, but the lack of customers interested in that lifestyle, at least not from the start of production of quidnon. When things get worse from an energy standpoint, quidnon will start to shine, but until then, the feelins of the folks at Sailing Anarchy or any other fancy boat forum will be a reflection of the general public.

    1. Actually, it's a good project for anyone who wants to live comfortably aboard a boat for not much money and have the option to move. The lack of a marketing strategy (you are right, there isn't one) is not a problem. The biggest problem is this: Quidnon is a good solution to the problem of rent/mortage expense in the US, but there is an even better solution to this problem: leave the country.

    2. Maybe I phrased it badly.

      The objetive of the project and the bulk of the work that you're putting on has the aim of generating a boat for you, and then maybe sell plans if there is interest,

      Or is it more framed like a business in the long term? trying to extract profit from all the work that you and your team has done?

    3. There are some basic steps to the process. The first step is to have a design. The second is to build a hull, float it and sail it around. The third is to sell some plans and have others build them. And then we'll see.

  5. Quidnon keeps getting better and better. Thanks for doing the nuts-n-bolts $$$ expose of buying copper plate and its thickness. There is some copper plate sheathing documentation online but nice to have the research done already... and why it makes sense. Anyone who thinks they can just go over the side whenever their painted boat bottom starts to get slimy and scrub it is a buffoon.... it's damn hard work, even with a scuba tank on. And to do it all the time is ridiculous. As for a marketing blitz I'd imagine the more Quidnons that get built and with alluring user pix popping up all over the web it will just snowball. After personally owning and living aboard both a (flat bottomed) sharpie and a keeler I'd NEVER go back to a keeler unless I had to. Flat bottom, shoal draft ROCKS!!!! So much nicer to sail and use. One miserable grounding in a keeler will prove that out plus all the cool anchoring spots keelers will NEVER access. And after living on 2 junk rigged boats junk rig ROCKS TOO!!! A few nights offshore shortening sail in near blackness out on a pitching deck, fighting a flogging sail, will prove this out also. Plus so easy to build the junk rig yourself. And on and on.... but Quidnon hits the sweet spots in many ways. A no-brainer for that poor kid living in his parents basement, feeling trapped, or anyone who resents the crap out of debt and wage slavery.

  6. There are a few inefficiencies in the US "economy" and one of those is, a few things that are thought of as reserved for the rich, are not really all that expensive.

    On NPR last night there was a thing on a show called "Freakonomics" where they explained that if you get your kid into fencing, you know, with swords, it make it almost a shoo-in that your kid will go to a top ten college. Yes, they have to be pretty good academically, and pretty good at fencing (I've messed around a bit with it and if you practice and spar regularly you'll be fine) they almost "have" to take your kid.

    And fencing is cheap as sports go.

    But back to the boat thing ... it takes a fair amount of discipline to live on a boat, but if you can pass yourself off as a wealthy person who has loftier goals than doing something so gauche as spending much money, you can get by just fine.

    And yes, a better solution still would be to get the hell out of the US.

  7. I realise this is "off topic" Dmitry, and sorry for that, but I just couldn't resist wondering if you are aware you are now a source of valuable insight to the appalling piece of gutter - rag, the UK's Daily Mail??
    I quote "Putin's personal style of rule means he 'cannot hand over responsibility to someone else' for unpopular decisions, political analyst Dmitry Orlov told Vedomosti."
    This in an article claiming htat Putin's trust level is at only 39% in Russia, ""

    I had no idea you'd risen so high :-) !!

    1. That's a different Dmitry Orlov. I am not a political analyst, or a hockey player, or a bank president, or an actor...

  8. Orlov have you thought of another copper-option that I consider for my motor-boat, it is mixing copper-dust with permeable epoxy-resin (floor-epoxy) and simply paint it on the boat-bottom. It is said to have the same properties as copper-plate or even better because of larger copper surface area.
    "CopperCoat" is i commercialized variant of this but it is very expensive, I recon you can make it much cheaper by yourself.

  9. Concerning the mattresses in the berths. Are they a standard size, such as a "full", or will they have to be custom made?

  10. Where are you getting your prices for copper?
    At, their cost for a 3x10 ft sheet (cheapest per sq/ft) in .0625 (1/16th) is $962, or $32/Sq.Ft. That puts the sheathing for 784 Sq.Ft. at $25,088, or ten times higher than your listing.
    Even their thinnest listing (.0162 or 24 gauge) would still be about $7,200.


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