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 3-bedroom with a kitchen, a sauna and a dining 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. Oh, and 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.

Friday, January 9, 2015

The Engine

When I looked into replacing the inboard diesel on my current boat, I found out that it would cost about a third of the price of the entire boat, and much labor, to pull the old one and install a new one. Considering that this engine would get used a few days a year for a few hours at most—to pull in and out of marinas, to shoot an inlet, and maybe to motor down a canal or two—this level of expense is completely ridiculous and impossible to justify.

Add to that the space that an inboard diesel takes up, with its endless hoses and other mechanical junk. Add to that the stink of diesel, the periodic oil in the bilge when the beast decides to start leaking, the decommissioning/recommissioning boondoggle after and before each season, and the clatter and throb of a high-compression engine, and the inboard diesel's remaining charms seem rather few and far between, at least to me. The high price of replacement parts, or of diesel mechanics, doesn't charm me either. Nor am I pleased with the necessity of contorting myself in a cramped space full of filthy, jagged objects in order to work on it (sailboat engines are installed in some of the most uncomfortable, badly designed engine compartments on earth).

When a diesel engine isn't being used, its fuel accumulates condensation and grows slime, which then plugs up the fuel filter. You see, certain bacteria find diesel fuel delicious, and all it takes to get them started is a few drops of water at the bottom of the tank. Diesels are generally reliable, except when there are fuel problems, but that is almost all the time, meaning that they are not reliable at all. There is almost no other use for diesel fuel than to burn it in a diesel engine. Diesel causes kerosene lamps to burn their wicks in a big hurry, and kerosene heaters do work on diesel but stink up the cabin.

At this point some people would probably want to point out that diesel engines have certain advantages. They last an incredibly long time—tens of thousands of hours. You are just supposed to change the oil every 100 hours or so... which I never do, because I have never, ever racked up 100 hours on any engine I've owned, even when moving the boat between Massachusetts and Florida. Instead, I changed the oil once a year, whether it needed it or not. What a waste! Diesel engines are also more fuel-efficient than gasoline engines. But I don't care about fuel efficiency. I only care about overall efficiency, and in terms of overall efficiency (money, space, etc.) diesel engines are, for me, grossly inefficient. Lastly, some people will say that diesel fuel is safe because it isn't particularly flammable, as opposed to gasoline. This is true, but there are plenty of gasoline-powered boats in the world, and they hardly ever explode, which is good enough for me.

But what alternatives are there? Well, it is possible to do an electric conversion. Electric conversions are quiet and much more efficient, because they can generate constant thrust instead of constant revolutions. But once you decide that you need to be able to motor any great distance, you find out that something has to power the electric motor, and that something invariably turns out to be a diesel generator, returning you to square one. Well, not quite: the price of an electric motor, motor controller, batteries, charger and associated wiring and hardware, plus the price of a diesel generator, is two or three times what it costs to just to replace the old diesel with a new one.

Another alternative is to use an outboard engine. Outboards mounted on transom brackets can be seen on many smaller sailboats, but they don't work very well at all because of cavitation, where waves cause the prop to come out of the water. When that happens, the prop spins in the air, the engine screams, and the boat rapidly loses speed; it's a most unpleasant experience. There is no way to properly adjust an outboard bracket on a sailboat; either it sits too high and the cavitation is simply relentless, or it sits too low and gets drowned by waves.

To work well with an outboard engine, a sailboat has to be designed with a special aperture some distance forward from the transom: an engine well. Since there isn't room to tip the engine up when not in use, it has to slide up and down on a track. And since you don't want to be reaching down into a well every time you need to shift or adjust the throttle, it requires control cables going to a console.

But if all these things are designed correctly, this arrangement works remarkably well. If you need to work on the engine, you pull it out of its well using a hoist, put it on a work-stand and work on it comfortably standing up—no need to clamber around an inboard engine, stuffing yourself into tight spaces, skinning your knuckles and bruising your kneecaps.

Unlike a sailboat's diesel, many of which are exotic, with hard-to-find parts (Volvos are especially notorious) if the outboard engine ever fails, it can be replaced for short money anywhere in the world very quickly and easily. If you find that you need more power, the upgrade is an easy one, because, unlike diesels, outboards don't increase all that much in size as they increase in power. A 75hp is not all that much bigger than a 10hp. HOGFISH motored at about 6kt on a 10hp Yamaha. QUIDNON will probably need at least a 35hp to go as fast.

Gasoline left over at the end of a voyage or a sailing season can siphoned out and burned in dinghy engines and cars. Also, nothing eats gasoline, and if stabilized using some additives it keeps for a few years (in my experience at least).

My plan for QUIDNON is to build it with an engine well in the back of the pilot house. The engine bracket will slide up and down on rails that will be mounted on generous neoprene doughnuts to insulate the boat from engine vibration, and the engine well itself will be very well insulated against the high-pitched whine of an outboard engine. This, it turns out, is much easier than insulating against the clatter and throb of a diesel. I haven't worked out the horsepower requirements yet, but the range is between 35hp and 75hp.

If the engine needs to be lifted out to be worked on, a pad-eye on the roof of the pilot house directly above the engine well will accept a hoist. Once laid down in the pilot house, it can be carried out on deck by 2-3 people (a Yamaha F90 short-shaft, which I think would be overkill, weighs 366 lbs) and swung over the side onto the dock or into another boat using a hoist hanging from the end of the foremast boom.

17 comments:

  1. So long as ventilation and heat transfer is squared away, this sounds like a great idea. There are diesel outboards (and even multifuel ones), so if there is a pressing need, this could be put in. The ease of swapping out motors is another big plus, rather than having to deal with the inboard.

    Has anyone ever done this? To be fair, what are some drawbacks? The only one I can see is that you don't have an electrical power element - an inboard usually charges a battery, but if you have solar/wind, that is moot.

    ReplyDelete
    Replies
    1. The inboard-outboard well will have a blower to ventilate it. The outboards all have through-prop exhaust (this keeps them quiet, because they use the ocean as their muffler). I wouldn't use a diesel outboard (exotic technology = economic inefficiency)

      Yes, lots of people have done this, myself included. There really aren't any drawbacks. An outboard can charge the battery just as well.

      Delete
    2. Outboards in a well are not all all uncommon here in NZ, they work just fine and pretty much for the reasons given by Dmitry

      Delete
  2. BTW, will a dinghy be part of your setup, on davits at the back?

    ReplyDelete
    Replies
    1. I'll be presenting that in a bit. There will be dinghy forks (3 sets of them) that will slide out of the hull as needed and accept multiple dinghies. They are much more effective than davits, don't clutter the deck and don't expand the overall length.

      Delete
    2. I agree with all your points. Diesels are only any good if they are in constant use.

      Delete
    3. Exactly. Find me even one recreational sailboat whose diesel is in constant use. Not a single one to be found anywhere.

      Delete
    4. That actually brings up a question for me. My personal experience, thus far, with sailing involves a dingy with a small outboard on inland lakes; and I've found that I really suck at short-tacking, so if I know that I'll need to short tack for a while, I'll start the outboard and let it run at 50% throttle so I don't have to stress over getting caught in the irons, as the little (2hp) outboard will eventually push me out of it so I won't have to keep getting up and starting it every time I tack. It's GPH consumption is low enough that I don't even pay it any attention, and it doesn't seem to matter the rest of the time. Dmitri, you said Quidnon should be steerable at a fraction of a knot, but how much would the MINIMUM engine power be to maintain, say, one knot? If the smallest diesel outboard (with an alternator) available on the market were installed, and primarily used for, say, refrigeration power (at partial throttle, with the balance of power being used at the prop) during a long cruise, would that change your overall efficiency question? I understand that just running the smallest commercial genset one could find might be better, but I'm asking as a "what if" kind of thought experiement.

      Delete
  3. Hi Dmitry,

    I like your arrangements, but thought I'd mention a yawl-boat as a consideration. I understand they're still being used by the Maine schooner fleet.

    The part that sounds the most attractive is their versatility.

    Dave Z

    ReplyDelete
    Replies
    1. I would like to make it so that the same outboard can be used both on the big boat and the tender, in effect making it a yawl boat. My main hesitation with the use of yawl boats is that they require crew (somebody has to run the engine, and somebody else has to steer the big boat), and I single-hand much of the time, and like having that option always.

      Delete
  4. Armchair sailor disclaimer. Why can't you mount an outboard on the transom, but have a telescopic driveshaft to put the prop down under the cavitation depth? A longer driveshaft would provide a torque effect similar to a heavy flywheel which might be useful in a large boat like QUIDNON seems to be shaping up into.

    ReplyDelete
    Replies
    1. Outboard engines come with 3 lengths of driveshaft, but only the short driveshaft is useful on dinghies. The longest shaft available still doesn't solve the cavitation problem if the engine is mounted on a transom bracket. Adding weight at the transom doesn't help either.

      Delete
  5. I've been mulling over the outboard well idea myself, but I'm interested in what solutions are available for the bracket & rail system. Are there any rail lifting systems available or is it going to be a custom job? I've seen the Mayers Motor mount but that wouldn't work with a well. Also, will the well allow you to use short shaft motors?

    ReplyDelete
    Replies
    1. From what I know it ends up being a custom job that involves a lot of picking through industrial catalogs and a small amount of TIG welding of stainless.

      I am hoping that a short-shaft motor will work, so that it can do double-duty as a a dinghy motor. On HOGFISH I bought a replacement motor with a long shaft, put it in the inboard-outboard well and found that it interfered with the skeg. Then I had to glass in the engine bracket at a slant, so that it would miss the skeg. Then I found out that this gained me 1/2kt of speed at full throttle because the stream from the prop avoided hitting the skeg and rudder. Happy end, but I think I would have rather bought a short shaft motor and skipped the extra glasswork.

      Delete
    2. If the prop stream doesn't hit the rudder that would seriously limit your low speed manouverability, yes? In close quarters docking I currently steer with my outboard, and loosing that ability is my main concern with the outboard well. I would have thought that at least directing the prop wash would compensate.

      Delete
    3. No. At least on HOGFISH, I had the following results:

      1. The boat came with the outboard on a transom bracket, with a pivot controlled from the cockpit. It didn't help with close quarters maneuvering at all. I eventually got rid of it, even before I moved the engine to the inboard outboard well.

      2. If the prop stream is to one side of the rudder, the rudder still works from a standstill. In one direction, it deflects the stream; in the other direction, the stream is deflected by a low pressure zone it forms as soon as the flow is established. A bit mysterious, but it works.

      In the end, I got to be very comfortable with maneuvering HOGFISH in close quarters. Lowering the centerboard part of the way helped a lot by shifting the pivot point of the hull aft.

      Delete
  6. What effect would placing this engine well off of centerline have? Can it be placed a bit off centerline? Or would the torque on the boat cause it to want to travel in a circle under power? If Quidnon is only under power for less than 100 hours in a year, would this effect really matter? Likewise, if Quidnon is only under power for less than 100 hours; what does that say about the "overall efficency" of favoring an engine well over a transom mount anyway? Under what conditions have you *needed* to run under power in seas high enough to either swamp the top or expose the prop?

    ReplyDelete