Bird of Passage 57
Liveaboard Full Power Auxiliary Voyaging
The clients desired a sailing vessel for offshore use and living aboard that would still be able to cruise the canals of Europe. She was designed to be a full time home for two adults, two children and up to two guests. The styling was based upon the principle that form follows function.
The owners designed the interior themselves but wanted to be sure to have room for a sauna, which can double as a childrens cabin when there are guests aboard. There would be a workbench in the engine compartment. The master stateroom needed to be large enough to have two office areas with computers and plenty of bookshelves. There is a wheelhouse or a deck saloon with large windows and a comfortable place to navigate the boat from inside. In addition there will need to be one small head for children and guests forward as well as the larger head for the parents aft.
The design was requested to be as light a displacement as can fill the requirements and still sail and point well. The owner's previous boat was 14.5 meters by 3.3 meters and proved too small. It had a retracting keel. They therefore were hoping for something about 15 to 16 meters long by 4.3 to 4.6 meters wide. They felt displacement should be well under 20 tons. They wanted headroom of between 1.9 and 2.0 meters.
The major challenge was that they wanted shallow draft with a hoped for maximum of 1.5 meters. This presents the two major problems that we needed to solve. First, we needed to get the center of gravity lower than the fixed draft would allow in order to be reasonably sure we had a low enough center of gravity to bring the vessel back from a roll over due to wave action in a storm. It was soon evident that the only way to do this was with a hydraulically retracted and extended keel. Second, we were faced with the fact that in this size boat the proposed maximum fixed draft was too shoal to allow a rudder with sufficient control to prevent broaching downwind. There were only two reasonable solutions to this. One would have been to use a retracting outboard rudder. However this represented engineering problems that appeared excessive. The second solution, and part of the strategy we eventually adopted, was to use a small aft "trimming" board just forward of the rudder. This can be used to vary the center of lateral plane sufficiently to reduce the required load on the rudder to whatever degree seems appropriate. In addition we have designed the rudder with end plates at both top and bottom to increase the effective pressure differential and help avoid ventilation from the surface. This will cause a slight increase in drag but is worth it because of the increased safety at sea.
The clients expressed the hope that we can work in full foam flotation. In light of this we laid out a carefully proportioned bulkhead arrangement that would allow the type of interior they wanted and still leave room for some flotation in the ends. Combined with the installation of additional foam in normally inaccessible areas they should be able to develop sufficient flotation to make the boat unsinkable if they don't go too overboard on equipment and interior complications.
Development of the Concept
After going over all these requirements I came up with a minimum load waterline requirement of roughly 13 meters and about 17 meters over all. We restricted the beam to essentially 4.3 meters, the minimum suggested amount, to get the draft requirement as low as possible. We used the fixed draft of 1.5 meters. With the keel locked fully down we are showing 3.16 meters draft. The fixed draft will probably still allow sailing to windward in shallow coastal areas with the keel fully retracted in modest winds.
The clients, after discussion with us, and taking into account some powerlines they need to clear initially had us design a double headsail yawl rig with plenty of working sail area, easy reefing, very few light sails, if any, and extreme simplicity of gear. Ultimately they had us design the single masted rig shown here. They have a preferred spar builder who will build them aluminum spars to the basic engineering specifications. Therefore there doesn't need to be much detail on the rig. The staysail will be self-tending. We also suggest making provision to set a large drifter flying, unless they intend to just start the engines whenever the wind falls light. The storm trysail should be on a separate track on the main mast. We would suggest avoiding the expense and complication of jib and main roller furling gears in favor of simple reefing gear based on lines and blocks.
The single masted rig as designed at present will allow fitting a windvane on the stern provided you don't need the over the stern boarding shown. We advise against over the stern boarding as it is only possible use it when in a completely sheltered harbor. If there are any waves at all you are much safer boarding over the side slightly aft of amidships at the point of minimum motion. With the help of the trimming centerboard it will probably be possible to achieve a neutral helm. This would make it quite easyr for a windvane to control this vessel.
As well as the sloop and yawl rigs shown you could have a number of other variants on this size vessel quite easily.
Since this is intended to be a cruising and voyaging vessel, there should be enough parts in all sheets to make any winches largely unnecessary. Halyard winches will be desirable. Aside from this the only winch on board will probably be the anchor windlass.
In this drawing we have allowed only one element to be based solely on fashion. This is the reverse transom that the client requested. We found that this seemed to work well with the conventional sheer. We drew the bow out to a moderate overhang and allowed it to take a natural shape to give reasonable forward sections and good reserve buoyancy. This will look quite different from the "straight line" chopped off stem profiles that are so common at present. This is intended to give us an opportunity to get better reserve buoyancy, better control down wind, and better spray throwing capability.
The stern shows an optional cut in stern platform at the right height for boarding from a dinghy. It is also, with the addition of a swing down ladder, of the right proportions to allow a swimmer or diver to sit comfortably while getting ready for the water.
The sheer has been very carefully proportioned to look best in three dimensions. Further it is carefully proportioned to be essentially planar. That is, as the boat heels away from the eye or the eye travels fore or aft around the boat, no awkward humps and hollows will appear from any angle. From any angle the eye will flow over this hull without strain or interruption.
The hull itself, aside from the reverse transom should be completely timeless. It will look "right" to the eye now, twenty years from now, or fifty years from now.
The deckhouse/wheelhouse and seating area require a certain amount of explanation. First it is important to understand that these will look significantly lower on the completed boat. First the cabin top centerline is 7 feet further from the eye than the sheer. Second, the wheelhouse side itself is significantly further from the eye than the sheer. Both of these factors will lower the apparent height of the wheelhouse. Many people would describe this nowadays as a "traditional" wheelhouse. However this is because it and the seating area aft of it is designed to be constructed primarily of filleted and taped together flat panels. We are accustomed nowadays to seeing trunks that are less functional but are designed primarily to be easily to lay up in a female mold. These are supposedly more "modern". More explanation of why everything is proportioned the way it is will be provided below.
The deck arrangement is essentially flush with a modest camber. There are intended to be normal hatches and ventilation into all compartments. Since this craft will divide its time between offshore work and canal work, there will normally be good reasons to avoid ports through which you cannot help but see non-restful views at sea and through which dockside on lookers tend to peer when in canals and marinas. With the good visibility from the large lounging areas in the wheelhouse this should not be a problem. We have assumed that deck prisms and clear hatch tops will be used as desirable to let plenty of light in. On the other hand there is no reason why round fixed ports should not be used in the hull if the clients wish. These should be the type with inside storm covers. On this size vessel they will not detract from the appearance as long as they are all the same distance below the sheer. If ports are used in the hull, a dark color should be used for the topsides. Otherwise you get that cannonball through the hull look.
The wheelhouse is the height it is for two reasons. This height allows full headroom in the wheelhouse and sitting headroom in the engine room under it. Every effort should be made to produce an engine room that is easy to work in, with tool benches, toolboxes, etc. This is especially true since we are going to be fitting twin diesels. The second reason is that it will then allow a low backrest on the seats immediately aft of the wheelhouse. This outside steering, control and general lounging area has a very slightly raised flat floor that gives more headroom in the aft cabin. This allows the sheer to be about 23 centimeters lower than it otherwise would be and still allows full headroom through most of the boat. This, combined with the illusions produced by viewing the vessel in three dimensions, will make the boat appear long, sleek and very fast with out in any way appearing delicate.
The forward face of the wheelhouse has deckboxes built onto it. These can have ventilation for the galley built into them and also allow storage of gear that should remain on deck. They are proportioned for easy chair like lounging while reading a book or talking in port.
The seating in the steering and control area aft of the wheelhouse is also composed of deck boxes, which can be used for similar gear storage.
The trimming board will have a crank within reach of the helmsman so that balance may be adjusted easily.
Unless a client decides to pay us for another drawing or two the interior details are pretty much up to them. At this point I have done little more than indicate the suggested general usage of various areas of the interior. My feeling is that a poor interior won't kill you and can always be torn out and redone. However, it is a very good investment for a purchaser of these stock plans, or any others on the site for which the purchaser contemplates a new interior, to have us do the work. It will generally save you both time and money during construction, allow you to get more enjoyment out of the boat, and if and when you need to sell it you will get a better resale value.
Here is the way I see the interior that the original clients requested: Starting with the master stateroom aft they wanted a double berth in the center. Remember that this will leave large amounts of room on either side. I would not try to make these areas to get out of bunk on. Rather I would suggest putting lockers with slanted faces here so that in port this can be a very comfortable, companionable lounging area. The forward ends of these I would orient toward being part of the two office areas. There is no reason not to use a "lee cloth" down the middle of the bunk if it must be used at sea.
The two office areas, not counting any use of space outboard of the double berths are each approximately 1.5 meters long. This should give quite large desks. They should not be pushed too far outboard as you do not want people to have too far to fall at sea anywhere in the boat. For the seating for these to be useable at sea even in good weather, the chairs will need to be on tracks recessed in the floor with stops that can be engaged to prevent sliding when the boat heels.
Forward of the office area we would assume they will want a head to port with shower, and lockers to starboard, or perhaps a head to port and a separate shower to starboard. The doors could be arranged to either shut off the head, shower and lockers separately or combine them into one big room. This space is about a meter long and over 4 meters wide.
We assume you would have a companionway into the wheelhouse and doorway into the engine room. These may be combined. There may turn out to be room for a passageway between aft and forward cabins without going through the wheelhouse. This depends on how things are laid out.
In the wheelhouse there could be a lounging area to port and a navigation area and inside steering station to starboard. If this is done there probably will be room for a standing headroom passage under the navigation area.
Forward of the wheelhouse there could be all sorts of arrangements. One could assume a rather large U-shaped galley immediately to starboard. We would suggest a diesel range for northern latitude cooking and heating and probably a wick-type kerosene stove for hot climate cooking. We often specify an insulated cooker cupboard for the stove to allow cooking more comfortably in hot climates.
To port of the galley you could put a double cabin. We would use one settee berth and one pilot or alcove berth above and outboard of it.
Forward of the double cabin and galley you could put another head. This will have nearly as much room as the aft one.
Forward of the head would be a good place for your sauna or for another double cabin.
The vessel has ample standing headroom everywhere under the deck. For some reason I do not understand the owners of the first vessel have decided to add a cabin trunk above the deck forward of the wheelhouse. Since when we conceived the design, which was done just entirely to suit them, with a flush deck and entire trunk is well above anybody's head and you'll never see anything out the ports, this seems odd, to say the very least. I guess they'll be able to open the ports by reaching above their heads, but if they want to open a hatch for ventilation they'll need a step ladder to stand on or a pole to poke it with.
The lines are shown in several simple renderings on this site. Remember several things in looking at them. The raked and radiused transom is not shown. This makes the stern appear a little "heavy". The drop keel and trimming board are not shown. The rudder is shown faired into the back of the keel and without the top and bottom endplates dictated by the extreme shoal fixed draft. When looking at the lines from aft you may see the fairing toward the end of the keel as having a "hard spot" in the tuck. This is because actually the rudder is back there and doesn't fair into the hull.
The general hull shape is simple but with great attention paid to keeping the diagonals as long and smooth as possible. We've been told that the boat was extremely straightforward to plank.
The general shape will promote good handling in all conditions and will have pitch dampening waterlines. There will be good reserve buoyancy and moderate extension of the waterline with heeling.
All and all there is every reason to expect the boat to be very fast and reasonably docile in her behavior.
The sheathed strip construction is described in detail on the plans. However given the size of the boat the great stiffness and unitary nature of this construction will be especially important. Construction is generally robust but simple. Due to the size of this project every effort hasl been made to keep construction easy and straightforward for the owners to build themselves. However, the client's requirements for shoal draft but also offshore capability demand the retracting keel. The engineering involved here is not terribly complex but the forces involved are considerable. We used large safety factors to account for periodic shock loading. Nevertheless, one's engineering is only as good as the assumptions that go into it. We fervently hope that we have given due consideration to every type of strain. We redesigned the whole system several times as we kept seeing more we could do to simplify and improve it.. However only building the boat and sailing it would really be sufficient to check this work. As an aside, we wish more designers were more scared of the stresses imposed by keels. The recent rash of keels tearing off of racing boats is completely ridiculous. Usually this is simply too many big bolts going through too small an area for there to be any way to make it strong enough. At least we have avoided this.
Unfortunately the owners of the first boat to be built to this design have chosen to go against our wishes and modified the retracting keel trunk and mechanism to be made of stainless steel instead of the bronze that we specified. Since we have very little faith in stainless steel when used near the water or underwater, especially in combination with the other materials used, we have to say that we would not be surprised to hear that this boat failed to make port someday. Let's all hope this won't happen.
We can picture a run from a secluded anchorage to a little village at the entrance of a canal system. Since this is a really full days run you have set a small alarm clock. It sits on your desk because this is just far enough away from your bunk so that you actually have to get out of bunk to turn it off. Since you are in northern climes you have left the diesel stove running on a low setting all night. Since there is a heating coil in the stove and radiators through out the boat, there is only the slightest shock when you scramble out of your warm bunk to turn off the alarm. A quick trip to the wheelhouse confirms that there is enough light to start getting underway. Though the low hills on either side of this little harbor leave your surroundings quite dark you can look south through the wheelhouse windows out of the harbor into the sea where you can see that dawn has nearly arrived.
While your spouse slips through the passageway under the wheelhouse to put a little cocoa on the stove, you go to the inside steering station to start the engines. Since the engine room is very well sound insulated and the two engines are not large, there is some hope that the children, who were up late with you in the wheelhouse planning your trip through the canals at the chart table, will be able to sleep in a bit. Each engine has a completely separate fuel system with its own filters and separators. Also you always filter the fuel through a Baja box before it goes into the tank. Therefore, as expected, both engines start immediately.
Since you came in from some threatening weather the day before the retracting keel is down, as is the anchor, of course. While the engines warm up a bit you go back down into the aft cabin and change into your clothes. Going back up into the wheelhouse in a minute or two you go out on deck and walk forward onto the foredeck and throw a lever on the hydraulic assisted windlass which starts cranking up the 75 lb. CQR. When it breaks the surface it has a fair amount of mud on it so you use a mop to knock off most of the mud. After rinsing the mop you have the windlass crank it the rest of the way up into the anchor roller fitting.
Going back to the wheelhouse you put both engines into gear and move at idle speed out of the little harbor toward open water where we can see from the light ahead that the sun is already above the water.
You are just clearing the headlands when a mug of cocoa appears up the hatch next to you. The arm holding it pauses for you to grab it. It then disappears and quickly reappears with a plate and utensils with eggs and bacon on it. As you see more the horizon to the east you soon can see the sun just coming up over the sea to your port. Your spouse comes up with a mug and plate also and sits in the corner of the settee on the port side of the wheelhouse with plate and mug in easy reach on the table. You increase the rpm on the engines a bit.
Companionably you watch the morning lighten and wait for the first signs of a morning breeze.
You are well away from the land and the sun is much higher before the occasional little catspaws begin to merge into larger and larger area of riffled water. You and your spouse follow your own strict rules for family voyaging and put on your safety harnesses and clip on as you go out on deck. Your spouse takes the outside wheel. Since the wind is a little abaft the beam you cast off the down haul on the jib, take a turn around the winch on the wheelhouse top and start pulling up the jib. When things start getting a little heavy you take another turn and grab the lever at the bottom of the winch and crank it up the rest of the way.
By the time you have done the same with the main there seems to be enough wind so that you probably arent getting much of a boost from the engines. You reduce power to idle and put them in neutral. Below you both props automatically feather their blades for minimum drag and you can feel that the boat is actually picking up a bit of speed. You stop the engines.
What starting the engines failed to do, stopping them achieves and suddenly your children are peering out of the wheelhouse doors bursting to come out and see the day but well aware that the rule is life jackets and safety harnesses on deck. Standing on the top step they can look forward at the horizon and aft at the receding land with the wind ruffling their hair. This is obviously more satisfying than merely looking out the portlights in the wheelhouse.
After quick looks around there are insistent suggestions that breakfast should soon be forth coming. Your pretended surprise that they should want breakfast when breakfast is clearly all over is not viewed with great amusement. So you go down and reheat the remainder of the cocoa and cook some more bacon and eggs, which is served in the wheelhouse with thick slices of bread baked in the oven the day before and covered with butter and marmalade. This disappears at a rapid pace and the children then vanish suddenly below to dress.
Your spouse has been steering for some time by the heading on the GPS in the cockpit. There seems to be a fairly strong cross current because you need to steer a bit to windward of the course on the compass to make good the proper course on the GPS. Because the landmarks are easy and the coast is high with readily identifiable features you havent followed your frequent practice of aiming slightly to one side of your destination so you will know which way to turn to find it.
The wind continues to freshen to the point where you round up briefly and pull down a reef in the main and a little later one in the self-tending jib. Since this is a one-day passage and everybody is well rested there doesnt seem much point in setting the windvane as you can steer more accurately inshore by hand. However you do adjust the trim board so the boat is mostly sailing itself toward your destination and only a light hand on the helm for minor course correction is necessary. Even the children get their turns at the helm.
For the mid-day meal however you set the wind vane temporarily so that everyone can take a bit of a break from the wind and sun. You all sit together in the wheelhouse and eat while discussing the upcoming exploration of the canals, lakes and rivers of the land ahead of you.
As the afternoon wears on the wind begins to drop again and you are able to shake out the reefs for full sail. Finally the wind has dropped enough so that you need a little more speed to reach harbor before dusk and you set the very large drifter made of spinnaker cloth. This is done by lowering the jib, attaching the tack line, which has been led from a block at the stem outside of the shrouds back to the cockpit, attaching the sheet and finally the halyard. The drifter is then hauled up in the lee of the main. The tack of the sail is drawn around and down to the foredeck and the sheet is pulled in. This gives you plenty of speed until just after you sight the harbor entrance in late afternoon. You then start the engines again, release the tack line and take in the drifter in the lee of the main.
As you approach the harbor entrance you take down the main, jib, staysail and mizzen and furl them. One of the children takes the job of hoisting the Q flag to request entrance by customs as you slip into the walled harbor entrance. An old boatman gestures you to tie up to several other yachts rafted against a wall that forms one side of the street along the harbor. Once tied up you keep the engines running for a bit while you use the hydraulics to operate a hydraulic motor driving a large machined bronze screw which raises the keel up into the boat to be ready for tomorrow's entrance into the canal system.
While you wait for the customs officer you tidy up the boat, make supper and talk quietly about the days and weeks ahead exploring deep into another land.
Drawings Provided in the Complete Set of Plans
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