Building an ocean going houseboat! - The Quidnon

"It is covered with aluminum diamond plate, for good traction, excellent wear resistance and to keep the boat cool by reflecting most of the sunlight."

"..going with a Chinese Junk rig. It has numerous other advantages beyond relatively low cost.

For starters, it gives you the ability to raise, trim, lower and reduce sail all without having to ever set foot on deck. It doesn't require a winch, just lots of blocks and plenty of line.

Junk sails are quite easy to make because they can be cut perfectly flat and still work. However, there are some complaints about them. They don't pull to windward when there is hardly any wind. Also, they don't point quite as high as a sloop, and the tacking can be quite slow. But they are much better than any sloop off the wind.

But it's not too hard to camber the panels, as Arne Kvernland recommends doing. Cambering the panels as shown gives them “belly” or “bagginess” so that it is the panel's shape rather than the flex of the battens that forms it into an airfoil that can take advantage of the Bernoulli effect to generate lift and move the boat to windward. A cambered Junk sail can be just as good to windward as a sloop rig."

"At this point a typical snooty yachty person will snort and declare that this boat must sail like a pig. Not so; Hogfish (his earlier scow/flat bottomed boat) does a perfectly respectable 7.5 knots off the wind, and 5 knots to windward, and points as high as most sloops."

"I might do a few more towing and stability tests, to verify hull speed and initial stability angle, but we already have these numbers from the hydrostatic and hydrodynamic analysis. I don’t expect any surprises, and so there probably won’t be anything to report."

"One of the problems with Junk rigs is that they tend to twist: the upper panels end up sheeted in less tight than the lower ones. Since the direction of the wind is generally the same at every height (while its strength varies) what this means is that only part of the sail is able to perform at optimum efficiency; either the lower panels are pinching or the upper panels are luffing, or both.

One classical way to deal with this problem is by using a euphroe. It is a piece of wood with holes in it to send sheetlets through, and it allows one to distribute the sheet tension across the battens in such a way that the upper battens are sheeted in with more force than the lower battens, counteracting the twist. Sailboat designer Tom Colvin, who circumnavigated with a Junk rig, favored the euphroe. Other people are less in favor of it, because it tends to flail about and hit things when tacking or jybing. I don’t particularly like the euphroe and would prefer something simpler to set up.

Previously, I proposed a design for an automatic traveler system that would move sheet blocks back and forth to counteract the twist. I don’t know whether it would work, because I haven’t tested it, mainly because I don’t like it. It’s too complicated. But I didn’t know what else to do… until yesterday.

Yesterday I looked at some traditional Chinese Junk set-ups, which use twin sheets. There are two separate sheeting set-ups for port and starboard tacks. Having two sets of sheets solves a couple of problems. One is that there doesn’t have to be a gap between the leach of one sail and the luff of the next for the sheets to move through, and a sail can overhang the transom without requiring a boomkin for sheeting, because each sheet hangs to the side of the sail. The other is that with the Junk rig the force on the sail acts differently depending on the tack: on one tack, it pushes the battens against the mast; on the other, it pulls them away from the mast. Because of this, the optimal sheeting angles are different for each tack, but with a single sheet there is just one attachment point on deck.

Now, that alone isn’t too interesting, but it becomes very interesting when combined with QUIDNON’s super-wide deck arches. You see, the twist happens because the forces on the different sail panels are different but the sheetlets all go to blocks that are all the same spot, at the same angle to the sail. But the deck arches allow the sheet blocks to be spaced apart so as to counteract the twist.

And so that’s the solution I finally arrived at. The sails are set up with blocks that hang from the boom and from each of the four battens. Since the higher battens need more sheeting force, because of higher wind speeds up top, the attachment points of the blocks move progressively further aft the higher up on the sail they are, with the topmost one almost all the way to the leach of the sail. The deck arches are set up with a padeye right in the center, and then two sets of blocks on two separate tracks to port and to starboard, for each of the sheets. The sheetlets start up at the padeye, go up to the block on the boom, then down to the innermost block on the track, then up to the lowest batten, then down to the next block on the track and so on.

The track allows the blocks to move, allowing the setup to be fine-tuned depending on conditions. For example, on the relatively flat and windless Chesapeake, where the most you might get is a few feet of chop, the lower part of the sail gets not much less wind than the upper part, and tends to twist less. On the other hand, out on the Pacific the swell can run at 20 feet or so, blanketing the lower part of the sail a considerable portion of the time, twisting the sail much more. To make an adjustment, one reaches up to the deck arch, unscrews the knob that holds the block in place, and slides the block over a bit. A bit of trial and error will give you a sail that can be sheeted in perfectly flat in the prevailing conditions.

I like this solution because of its simplicity. The trade-off is that the running rigging has gained two more lines, because now there are four sheets to manage instead of two. But then that’s not a big increase in percentage terms. Before splitting up the sheets into port and starboard there was the one sheet, two halyards (peak and throat), two topping lifts (fore and aft) and one downhaul. That’s 7 lines per sail. And now there are 8.

The twin sheets have a few additional advantages. They make it possible to backwind the sails, to slow down or even to sail backwards. This is sometimes useful; for example, for sailing into a slip at a marina. (Yes, Junk rigs make it possible to do things under sail that sloop and ketch sailors can only dream of.) It also makes it possible to heave-to in the traditional manner, by sheeting in the main, backwinding the foresail and lashing the tiller to leeward, rather than in the Junk manner—by simply letting go the sheets and playing with the rudder until the sails trail off to leeward at some comfortable angle. When becalmed in a swell they make it possible to tighten both port and starboard sheets so that the sails do not swing back and forth on the swell, snubbing at the sheets. Lastly, if a sheet parts (as they all do eventually) then it is still possible to sail—perfectly well on one tack, less well on the other.

There is just one question left to answer: Does this actually work? (I know, details, details...) Well, I rigged it up on the 1:12 model, and, lo and behold, it does! Here's the money shot: the mainsail sheeted in sets perfectly flat. This is about as good as it gets. This boat is going to sail to windward and short-tack like a dream!"

"Then there is the question of where to store all this power. My solution, which I know works well from experience, is to use Trojan T-105 6V 125Ah batteries. I plan to put 8 of them, in 2 banks, in a large, plastic-lined, vented battery box down in the bilge, under the cabin sole.

The two requirements for the battery enclosure are that it must never leak acid into the bilge, and that any hydrogen gas generated while charging is vented overboard (hydrogen is explosive under a wide range of concentrations and its flames are hot and invisible).

With all the sundry pieces added in (charger, charge controller, inverter, shore cable and plug, circuit breakers, wiring and outlets) the budget for the entire electrical system comes in just under $6,000 or 12% of the total budget, which is quite reasonable for a comfortable off/on-grid set-up."

"..various kinds of storage: shelves, lockers, hanging lockers, cabinets and so on. The space under the pilot berths is occupied by the water tanks, but everywhere else the space under the settees and the berths is also used for storage. This adds up to about 500 cubic feet of storage space, most of it close to the waterline."

"The model has been hydrostatically tested using Orca3D software. (We are very grateful that Orca3D has agreed to sponsor our project, and has donated two seats of their excellent software for our use.) Hydrodynamic tests will have to wait until we build a 1:12 scale model, and conduct towing tests and other types of in-the-water testing.

The good news is: there are no surprises at all. The hydrostatic tests have confirmed the initial calculations: QUIDNON, ballasted as initially designed, is going to be seaworthy and reasonably fast."

"..I designed a fan sail, which, as I have demonstrated yesterday, works remarkably well to windward. Here's my recipe. There are 5 panels, all fan-shaped, and 6 spars. Starting at the bottom, there is a boom, 4 battens and a gaff. All the panels are exactly the same in height at the luff and taller at the leach. The boom is horizontal, while each spar going up is angled 8º more than the previous spar, adding up to a 40º angle for the gaff."