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This article concentrates on dinghies as tenders for larger boats. Most often, dinghies are rowboats , or have small outboard motors. Sometimes a small sailing rig is available.
Dinghies are extremely important. Nothing can make a yacht so inconvenient to service as a wrong-sized dinghy. Almost as many yachtsmen are killed in their dinghies as in their yachts. This happens because many people attempt to operate their dinghies in states of exhaustion or drunkenness that they would never dare on their main boat. Therefore, safety is extremely important.
Dinghies range in length from 2 to 6 m. Larger auxiliaries are called pinnaces or lifeboats. The best size of dinghy for most yachts is about 3.5 to 4 m, because this can carry a complete family or a family's provisions for a month. However yacht size usually is the limiting factor.
The favorite modern material for building a dinghy is glass-fiber reinforced polyester (GRP), because it requires the least care and never rots. Water penetrating the outer coat can cause blistering and delamination. This can be prevented with a barrier coat of epoxy resin.
Aluminum and marine plywood also work well. Carvel and clinker-built wooden dinghys are beautiful, and have finer lines and better handling, but they are usually somewhat heavier. Favored woods, in decreasing resistance to rot, are locust, mahogany, fir and spruce. Modern urethane varnishes are sturdy and help resist UV deterioration.
There are four common shapes for rigid dinghys.
- Whaleboats are the classic premium rowboats, with a sharp bow, and stern fine lines and a canoe transom. They tip slightly, row, motor and sail the best because of their fine lines, but have less cargo capacity than prams.
- Whitehall Rowboats are the water taxis of the late 1800's until the invention of the small gasoline outboard. They are considered one of the most refined rowboats for harbor and lake use. Whitehall Rowboats are a descendant of the Captain's Gig which was used for a similar purpose on a navel vessel.
- Dorys are sharp-ended boats made of wood, fiberglass or aluminum. They cut the water well, but initial stability is low making them feel tippy in flat water. A loaded dory becomes more stable as more of the beam of the boat is submerged. Dorys are not generally used as service boats to yachts. A dory can be landed or launched through surf where a Whitehall may flouder.
- Prams are like wide dorys with flat bows. They don't tip and carry a lot of cargo, but don't cut the water well.
Fiberglass boats are all molded, so whaleboats have supplanted dorys as working fishing craft, which were once less expensive because they were easier to build.
For inflatable boats, the Zodiac-type inflatable, with a rigid deck and transom, have proven superior for engines. They row and sail about as poorly as prams because of their blunt bows. Inflation makes them tough, with large reserves of buoyancy.
Folding and take-down multipiece dinghies also exist.
The Dinghy Problem
On yachts shorter than 10 m there is not enough room for a reasonable dinghy, but there is a genuine need for one, because anchorages are far less expensive than slips or dock space.
Owners of small yachts compromise. They carry a small rigid dinghy, tow a larger dinghy or deflate an inflatable.
Rigid dinghys for small yachts are very small (2 m) dinghys, usually with a pram (blunt) bow to get more beam (width) in a shorter length.
Larger dinghies can't be kept on deck, so they are towed. A towed dinghy should have reserve buouyancy, an automatic bailer and a cover, or it is likely to be lost at sea. Most masters prefer a tow long enough to put the dinghy on the back of the swell, to prevent the dinghy from ramming the transom of the yacht.
Inflatables take extra time to inflate, and tow badly. During an ocean passage, they fit easily in their place.
Some owners have experimented with a two-piece rigid dinghy that's towed in harbor and disassembled into two nesting pieces while off-shore. When the joining method was sturdy, these reported good results.
A dinghy should have a strong ring on the bow, bolted through the keel in a position that will not score the yacht's deck when the dinghy is inverted on deck. The bow ring is used for the painter (tying to a dock), towing and anchoring.
The dinghy should also have two other rings, on each side of the stern transom.
All three rings are for lifting, and securing the dinghy for stowage.
The only other essential hardware are the oarlocks (see rowing, below). The boat can struggle along with a single sculling oarlock atop the transom. The oarlocks should have ropes and storage pockets, or permanent mounts.
The dinghy is generally inverted midships on yachts to avoid unbalancing the boat, and to keep the dinghy secure from waves. Inversion keeps water out of the dinghy. Most yachts launch their dinghies by hand, or with a simple lifting tackle rigged from the main mast. Davits over the transom are convenient and look good, but sailing in a heavy following sea can cause the loss of a dinghy.
When the dinghy is inverted amidships, many yacht owners prefer it to have hand-holds on its bottom. These help launch it, and also provide more handholds on deck.
If a dinghy is towed, an extra line with a loop in the end, known as a lazy painter should be attached to a twart, cleat or mast step so that when the towing line breaks, there is an easy line to grab with a boat hook. This extra line makes retrieval easier at sea, especially if the boat is partially swamped.
On all dinghys a name and identifying numbers should be stenciled to prevent theft. The classic place is the bow, but a good place for inflatables is the inside of the transom. The name should not be that of the main yacht, because this makes a dinghy tied to the dock an invitation to steal from the main yacht. Outboards should be scruffy-looking, and locked to the dinghy with a security cable. The dinghy should be locked to its place when stored on deck in a harbour, or alongside a public dock.
Conventional dinghies are rowed. Usually there is one set of oarlocks for each thwart (seat). Sliding thwarts allow far more powerful rowing. A removable thwart can permit standing rowing. A sculling oar can substitute for several oars on a dinghy normally moved by other power. A nice refinement is to place a notch or oarlock in the transom (rear wall) for a sculling oar, perhaps with a tie-down so the scull need not be pushed down by hand.
Outboard motors are also popular, though much more expensive. Engines always swing up so the dinghy can be grounded without damage. A horsepower per meter of length can move a dinghy faster than oars. Two horsepower (1.5 kW) per meter can reach hull speed. Ten horsepower (7.5 kW) per meter will put a flat-bottomed dinghy on plane. Conventionally, the gas tank is placed under the rear thwart.
Electric outboards and trolling motors are now readily available for quiet and pollution-free dinghy power. See Electric boat for more discussion of this.
The transom should not be cut down for the engine. If it is, then an engine well must be present. This prevents the boat from flooding from a low wave over the transom.
The typical sailing rig for a dinghy is a "gunter or sprit sail ". This is a two-piece folding mast that can be stepped through a thwart and rested on the keel. It is raised by pulling a rope. Generally, it resembles a single-sailed gaff rig rather than a marconi with a triangular mainsail and jib. The gaff rig has a lower center of force and a simpler rig. The bottom of the main sail is usually untended (no boom) in order to avoid hitting the passengers with a spar. A new, compact possibility is a power kite.
Sailing dinghies for racing usually have a daggerboard or centerboard to better sail upwind. The trunk for these is usually in the middle of the dinghy's cargo area. Traditional working dinghies have a lee board that can be hooked over the side. A lee board does not split the cargo space.
A sailing rudder is usually seized (tied by rope) to a simple pair of pintles (hinge pins) on the transom. The bottom pintle should be longer so the rudder can be mounted one pintle at a time. The rope keeps the rudder from floating off in a wave.
Rudders and centerboards always have swiveling tips so the dinghy can be landed. Rudders often are arranged so the tiller folds against the rudder to make a compact package.
A dinghy should have at least a sculling oar, life-jackets, a hand-bailer, a bailing sponge, a large flashlight, a mouth-blown horn (not a loud-hailer, but a breath-blown fog-horn), signal whistle, signal mirror and flares. This equipment should be in a bag made of water-resistant materials tied to a thwart or inside a locker.
Anderson-style self-bailers are useful for engine-driven and sailing dinghys. These are slot-shaped seacocks that project into the stream below the hull. They are opened when submerged and moving rapidly. The downside is that if the boat is beached in sand, it can clog the self-bailers until the boat is inverted and the sand removed.
A dinghy's crew can rest or fish if it has a small anchor. A rode (anchor rope) made of floating rope can't be cut by snags on the bottom. The traditional dinghy anchor is a mushroom, or small folding grapple hook. The mushroom anchor does well in muddy bottoms. Folding grapnels weigh less and work in currents, but don't anchor quite as well in mud. Some persons prefer a small danforth or plow, the same as they would use on a larger boat, but these have sharp edges, and need to be pulled-on to set.
A dinghy should not be able to scratch the mother-boat's paint. The traditional fender is a length of heavy rope seized (tied by small rope) to the outside of the bulwarks (top of the sides), and slightly loose to provide a handhold for launching, or men overboard. Many modern dinghies mold in a ridge of plastic.
Many people prefer a dinghy to have a fitted cloth cover which can shed seas, or act as a shade, cuddy, cargo cover or storage cover. Traditionally it would toggle to the fender-rope or be suspended from the gunter (small folding mast). These days it might be tied to a few points and secured with snaps or velcro. Acrylic canvas is a fine modern material that resists the sun. A couple of battens and windows to make it a tent are wonderful.
A dinghy should have a locker to secure its equipment. Traditionally this is under a thwart with a bronze padlock that is opened at sea. The locker is generally arranged so the boat's painter (rope to the front ring) can be locked around a mooring by placing a loop over a dowel or hook in the locker, and locking the locker.
Dinghies as lifeboats
The extra equipment can be stored in a bag that's tied to and kept under the dinghy at sea, and brought into the cabin in port.
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