Monday, January 26, 2009

Belief Systems Concerning the 5-Part Hull

This is (probably) the last post that I'll derive from Outrigger Canoes of Bali and Madura, Indonesia, by Adrian Horridge.

The "five-part" hull typical of the outrigger canoes of Oceania is an interesting construction unlike any Western design. As shown in the illustration (from Horridge), the five parts consist of the hull bottom, two upper planks that form raised gunwales, and fore and aft "crotches" that form the ends of the raised gunwales and serve somewhat like a stem and sternpost. Fastening methods differ, with the pieces either pegged or sewn together (pegged in Bali and Madura). In either case, the outrigger booms, which rest atop the raised gunwales, are typically lashed to cleats inside the hull bottom which are left standing proud when the hull is carved. These lashings therefore tend to hold the raised gunwales down against the hull bottom.

Indonesian canoe builders start building on ceremonially auspicious days, and some take care to launch on such days as well. "Like other cultures in the Austronesian tradition, the Balinese have a deep belief in the cyclical nature of life and the world," writes Horridge. "(An) aspect of the cyclical the flow of generations. The son becomes the father and generates another son, and every child in Bali is considered to be the same person as an ancestor. This means, in our context, that changes in the design of canoes are not acknowledged," even though the brief historical record shows significant changes, even since the introduction of photography.

"Another Malayo-Polynesian belief is that objects such as canoes must be made exactly in a specified way," he writes. "If a man should adjust the design of his fishing canoe and gain an advantage, it would be attributed to evil magic and he would expect to have to repay the evil spirits in retribution later, possibly by drowning at sea. There are strong forces, therefore, ensuring that all canoes are the same within the village and strengthening the local view that the designs have always been the same."

As to the source of those supposedly immutable design principles, Horridge writes, "The Balinese believe that ideal proportions are represented in the human body. Therefore, an outrigger canoe, being a creation of its maker and having a soul of its own, must always be constructed with every dimension calculated according to a simple rule of numbers." There are elaborate rules of thumb concerning the proper dimensions of every feature on the canoe, and these rules are invariably based on proportions to the builder's anatomy -- for example, his height, the span between his thumb and forefinger, etc. Such rules are based on the belief that the human form is perfect in its proportions (not unlike the belief by Renaissance European artists in the Vitruvian Man).

The association between the human form and the canoe goes deeper yet. The hull bottom is held to be female, while the crotch pieces are held to be male. During construction, the builder bores a hole in the joint between the two (not clear if it's at the bow or the stern), and deposits in it a minute quantity of gold, which Horridge states is symbolic of semen. Put it all together -- man, woman, a bit of jizz -- and you've got that wonderful living thing, a canoe.

Wednesday, January 21, 2009

Taiwanese Boat

Check out this incredible rowed canoe from Orchid Island, off Taiwan, and see Tim Shaw's post on the subject on his Chine bLog.

Monday, January 19, 2009

The Protolateen Rig

Here's an interesting rig, found on outrigger canoes (especially double-outriggers) in Madura, Indonesia. Called variously the Madurese Jukung Rig (a simple descriptive term), the Primitive Oceanic Lateen (so-called by Haddon and Hornell), and the Protolateen Rig (by Horridge), it is a two-boom triangular sail with no mast. I'm posting a photo and line drawing of the same basic rig, though the two boats are somewhat different.

The prop that supports the upper boom (the blue and white stripped pole in the photo), and hence the whole rig, can't be termed a mast, since it's movable and neither stepped nor supported by a thwart. Depending on the point of sail, much of the rig's weight bears on the tack, the forward corner where the two booms meet, which rests on the bow of the canoe itself. Guys or shrouds are rigged from the sail's upper boom back to both stern outrigger booms, to keep the rig down and keep it from blowing overboard. And in some examples, another line runs from the upper boom forward and down through an eye at the forward outrigger, and then back to the helm station. I believe that when tightened, this line keeps the tack down when sailing on the wind. When running downwind, I think this line is loosed so that the tack can lift and the whole rig be oriented somewhat athwartships.

Adrian Horridge, whose book Outrigger Canoes of Bali and Madura, Indonesia I cited in my previous post, believes the Protolateen rig is the original rig of the Austronesian people, that that all other Pacific rig types (with the exception of Western rigs introduced much later) derive from it. I won't try to paraphrase his complex arguments, but the diagram below shows his theory for the diffusion and evolution of the various Pacific rig types.

The Protolateen rig is shown in A, and a slight modification, with the upper boom hanging by a short line from the prop, is shown in B. It's easy enough to imagine either of the next stages of evolution: the addition of a short mast from which to hang the upper boom (C), or stepping the forward end of the upper boom and turning it into a quasi-mast (with stays or shrouds), while doing away with the movable prop (F).

Two other interesting details to note:
  • In the photo, note the extreme forward extension of the outriggers, several feet beyond the bow of the hull.
  • In the line drawing at top, note the unusual nature of the stern outrigger boom. It's a two-part boom, each part made of elaborately curved and carved pieces and lashed to the hull at a significant angle from athwartships.

All of the art here is from Outrigger Canoes of Bali and Madura.

Sunday, January 11, 2009

Indonesian Canoe Outriggers -- Pretty Clever

The outriggers of Indonesian double-outrigger canoes (jukungs) are as sophisticated in their design as they are rudimentary in the technology of their construction.

Many Balinese canoes have distinctive upward-curving outrigger booms, giving a graceful gull-wing appearance. The booms are lashed to the hull, and separate connector pieces are attached to the ends of the booms in a scarf joint, usually with a single wooden peg and lashings. The bamboo floats are attached to the lower ends of these connectors by lashings around the floats. Sometimes, the connector penetrates a hole in the float.

This arrangement has several advantages, some of them surprising. According to Adrian Horridge in Outrigger Canoes of Bali and Madura, Indonesia, "To an engineer it seems obvious that the direct connection (i.e., eliminating the intermediate connector piece) is the one most likely to survive (for a short time) in a rough sea... The direct connection has fewest weak points and is the least likely to work loose."

But Horridge goes on to cite three advantages to the indirect connection:
1. It brings the float down to the surface of the water, thus allowing the use of the gull-wing boom form, or of other booms shapes (even straight ones) that ride higher above the surface and so don't catch waves.
2. It provides "a flexible structure that will absorb the strain energy as the boat moves in the waves."
3. It allows the height of the float to be adjusted, for example, to accommodate different boat loadings or sea conditions.

Item #2 is the most fascinating. To quote Horridge again:
That a flexible structure lashed together from short pieces of wood can be the preferred design may seem strange if one is used to structures made of steel tubing; in fact, when a structure must be light and resist shocks and shaking, some designs that are apparently not firm or well engineered, and that are also troublesome to make, turn out to be the most resilient. Cloth, straw hats, leather shoes, baskets, chain armor, even human skin resist breakage for two reasons: the loads are distributed among many fibers or components, and forces that change suddenly are dissipated as friction between the parts. Gymnastics performed upon a hard wooden chair will soon loosen its joints and break it, but on a basket chair the gymnast will be exhausted before the chair collapses. When a structure receives a hard blow it will break unless the energy of the blow can be absorbed as heat energy in the structure, which is why composite materials such as wood, horn, bone, and fiber glass do not shatter when hit. So, when an outrigger hits a reef or the beach on coming into land, it is stronger if designed to absorb the blow. Melanesian outriggers, in particular, were built like basket chairs. Also, at sea, the continual kinetic energy of the waves is dissipated if the outrigger is flexible...

The floats are made of bamboo, with the shiny outside layer scraped off to reduce weight and to remove nodes, to make the surface smoother and reduce resistance. This also allows the fibrous portion of the bamboo to dry out between uses, and so prevents rot. Often, a small hole is bored in each segment of the bamboo to prevent cracking, and modern users sometimes coat the floats with epoxy. Even so, floats are removed after every usage and stored under cover.

Interestingly, the floats extend beyond the front of the canoe's hull, and they are always toed-out a bit toward the front. According to Horridge, native users explain this as being a guard against pitch-poling, but Horridge states that its more important function is to maintain sailing balance:
I think it more significant as a control of the "weather helm." (A sailing boat of any kind should preferably tend to turn into the wind if the wind suddenly blows harder. This feature is called "weather helm.") If there is a gust, the float on the leeward side tends to dig into the water. If the float extends far forwards, it will then suddenly shift the center of lateral thrust far forwards, creating more weather helm. How far the floats protrude forwards may be more important than how much they are turned outwards.

The line art, from the Horridge book, shows a Balinese jukung model, accurate except for the smaller number of seats than in an actual canoe. Note especially the connections between the outrigger booms and the floats.