Bamboo Raft Design Details from Voiliers d’Indochine

Bamboo Raft, Circa 1940,
from Voiliers d’Indochine

The modern bamboo rafts of Indochina, which I’ve only seen on the beach at Sam Son, Vietnam, not too far South of Hanoi, are one of the last surviving types of Vietnamese working sail. They carry fully functioning sail rigs—big standing lug sails—but also have very efficient outboard engines. Still, their ancestry is perfectly clear and they continue to go to sea for two days at a time fishing. Just as they have for at least 100 years.

In Vietnam in times past, bamboo rafts (Ghe Be in Vietnamese) were rigged with up to three masts and sails, steering oars and dagger boards for lateral resistance (as well as steering) and were reported by French sailors to be fast sailing and sea worthy, up to a point. Apparently those pure sailing rafts went very well off the wind or across it and sailed well enough upwind, but pounded heavily in a head sea.

Modern Raft Construction

The modern version aren’t really bamboo rafts anymore, rather they are Styrofoam rafts, with the Styrofoam scraps captured in split lengths of bamboos. Where the construction of the original bamboo raft was very straightforward, simply lashing the flotation bamboos directly to cross pieces of timber or bamboo, the modern version is a little more complex. For one thing, they bend the side bamboos (which really are full-length, full-round bamboo stems) up to make a sharply rising bow, which no doubt helps a great deal with the problems the French recorded 70 years ago: pounding into a head sea and overwhelming the raft. The bending is done by toasting the bamboo over a low fire (as planks are bent for most Vietnamese boats), which does in fact seem to weaken them somewhat, but not enough to affect their functioning. A few of the rafts I saw at Sam Son in 2010 actually used at least a little timber framing in the raised end, forming the sides. The sides and the bottom are all constructed as a single unit, the bottom made from a number of splits of the heavy bamboo, lashed together on short stout crosswise pieces. Then the Styrofoam is packed into the area between the sides and a second layer of split bamboos pre-lashed to their own cross pieces is laid over the top and the whole assembly is basically quilted together, stitching with very heavy monofilament fishing line which is routed over the crossbar pieces in the top and bottom, securely imprisoning the Styrofoam between two durable layers of bamboo and the long bamboo sides. By the time the lashing is completed, the structure is really very strong but very flexible.

Modern Rafts: Sam Son, Vietnam

Modern Sailing Rafts at Sam Son Beach

In sailing days the daggerboards (up to three of them) were simply shoved down between appropriate hull-bottom bamboos and were wedged against arched supports that spanned clear across the hull. Nowadays there are apparently no daggerboards in use and no provision is made for shoving them down through the hull. Thus, although they have and use full working-sized standing lug sails, which used to be the ordinary working sail on this coast, they no doubt only use sails for working broadly downwind and trust to their new diesel engines to get them back upwind.

Raft Engine Details with callouts

Long-Tail Motor and Drive Train used on Bamboo Rafts

Raft Engines

The arrangement of the engine is very similar to the long tail outboards used on so many of the Mekong River freight boats; a single-cylinder Chinese diesel engine of perhaps 10 horsepower is mounted on a homemade pivoting frame that also supports the drive train all the way back to the propeller. The drive train includes:

Unlike the Mekong River long-tail outboards, which use a small diameter pipe bent and flared at the end and facing directly into the prop blast to pick up the cooling water for the engine, these rafts use a separate centrifugal pump with its suction stuck down through the slot in the raft. This small pump supplies cooling water to the engine as well as service water to the bearing and coupling at the upper end of the drive shaft.

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Modern Raft: Sam Son

Engine in Use

The aft end of the raft has its center section cut away for about 18 inches wide by five or six feet long: wide and long enough to pass the prop shaft from its resting position above decks down through the hull and into solid water (the propeller is two feet or so behind the raft). The outboard unit is not used for steering, only propulsion, and a large T-handle sculling oar mounted on the port side of the vessel is used for steering as well propulsion. In use, the engine is started with the prop in the air as assorted helpers, wives and neighbors, urge the boat out into knee deep water or better and a strain is taken on an anchor that was left offshore when they approached the beach, starting the raft away from the shallow water. As she moves into water deep enough to run in, the spinning prop is gradually lowered into the water, splashing some of course, but getting a bite to move out to sea. They pick up the anchor as they motor over it on the way out.

The beach at Sam Son is fine soft sand, so a slight miscalculation probably does little harm, if any, to the machinery. The return to the beach is done the same way; the raft makes an approach toward a bit of beach it can land on, drops what will become the offshore head line anchor and attracts the attention of wives, fish mongers and the crews of other rafts already on the beach. The steersman works away with his sculling oar, just steering as they make their approach, while his partner stands by the hoist rope for the motor and its equipment. As the water shoals, he begins to hoist the propeller clear of the water a bit at a time, finally hoisting it clear up and setting it into a rest on the back deck while shutting off the engine. Meantime, the welcoming committee from shore wades out thigh deep and helps push the thing up onto the beach where it needs to go. All the while, the steersman is sculling and steering with his long sweep, finally swinging the oar aboard as well. They don’t leave the raft with her stern offshore, but immediately swing her around with eight or ten people working, so her bow faces out, then begin off-loading the catch. When I’ve watched them working at Sam Son they had sailed before daylight and had been offshore a mile or so both north and south of the town, towing a net of some sort under power. They landed large baskets full of tiny pink shrimp, a fairly clean catch, with just a few sardines mixed with the shrimp.

Raft in Northern Laos

Raft in Northern Laos

River Rafts

Besides the ocean going rafts at Sam Son, there are of course long slender bamboo river rafts built just as you have seen them in Chinese paintings—only a few bamboos wide, absolutely flat for 20 feet or more, then sometimes at one end all the bamboos bent tidily up at the bow. Whenever I’ve seen them they have been propelled with a pole pushing off the bottom of the relatively shallow river. They’ll easily carry a person or two and some small freight. They can’t cost very much in the jungle country they’re found in and they certainly serve the purpose well.

Raft Bridge in Laos: Ou River

Raft Bridge Over the Ou River in Laos

It’s only a short step from the graceful, free riding river raft to the Laotian floating bamboo bridge. Where the traffic warrants (and where other river traffic won’t be impeded) the people will build a series of such rafts, anchor them in the river, all pointing upstream, perhaps five or six feet apart, and then weave a bamboo deck from one to the other across the stream. . .and then ride motorbikes across it! We’ll not count that as a boat though, no matter its ancestry.

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