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May 22, 2006

'Pencil' raft- lighweight racing raft.


Kontiki Chairman's Challenge 2005 produced an experimental raft from our boy troop, as well as this raft from our girl troop. Extremely lightweight, this raft was pretty fast, and in fact won a sprint race. Using only 2 pioneering poles and 1 decking sheet, this is not the most comfortable raft for a long-term expedition. I have drawn it with the shelter and paddlewheels (one in front of and one behind the deck) removed to show the structure more clearly. The raft is named after the 2 groups of barrels, which have 'sharpened' ends, built with fibreglass cones that were specially made for the raft. These pencil tips at the front and the back are the anchoring points for six ropes that run from the front to the back, clamping the barrels together and holding them as one unit. The pencil concept was originally used on a full-size Kontiki raft and all of the components were made by the Beneke family.

The barrels connect to each other because of lugs that are attached around the rim of the barrel. These need to be attached very carefully- preferably by brazing and not welding. Try and find someone who knows their work to do this for you. We have had trouble with leaks around these lugs- the barrels are made of very thin metal and the heat needed to attach the lugs damaged the rubber seal. This is just about the lightest large oil drum raft I can imagine- there is very little weight wasted on structure. But the advantages of increased streamlining and reduced structural weight come at a cost-there is a good chance one or two will leak, so you might want to make some extra. Try this out if you have barrels to spare, but not if they are the only set you have to build a raft with.
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