Re: [bolger] Flexibility (was Wing Nut - better link)
wmrpage suggests that the claimed benefits of flexibility in boats are 'balderdash'. I'd like to give a counterexample.
The Aleuts developed their baidarkas (Aleutian kayaks) over nine millennia and with them the reputation of moving through the water at impressive sustained speeds (see George Dyson's book "Baidarka" for the sources. George also wrote an article for Scientific American a few years ago.).
Anyway - one thing they did was to deliberately make the keel flexible by including 'hinges' to divide it into three parts. These were sometimes simple, like a table-leaf hinge, and sometimes more elaborate, with bone ball-joints worked in. In addition, they included bone inserts where major components were lashed to each other ( - deck beams to stringers for example - ), the better to allow them to slip without wear. Where they didn't want slippage, wooden pegs (dowels) were used to locate components rigidly.
The boats were by no means 'floppy', with the hinges being tightly lashed, but there was certainly a degree of 'elasticity' (for want of a better word) that you wouldn't find in a boat made without hinges.
Longitudinal stiffness was provided by the gun'ls, which were each made from one length of wood.
The 3-part keels had nothing to do with building their boats from short lengths of driftwood. Remember that we're in the land of Sitka spruce and excellent timber was available to them, unlike some of the Inuit groups elsewhere in the Arctic.
I've got a lot of faith that evolution over long periods of time can lead to near-optimal solutions, and few artefacts have evolved over a longer period than the baidarka. So whether we can explain it in engineering terms or not, the flexibility of the baidarkas was something that must have paid off in some way, otherwise it would have died out.
On another matter (related) we have an 1827 ship in Dundee harbour - the frigate Unicorn - built at Chatham in 1827 and still 95% original as it was never used in anger. As far as I can tell, it's the earliest ship to have been built using wrought-iron diagonal bracing and knees.
Bill
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The Aleuts developed their baidarkas (Aleutian kayaks) over nine millennia and with them the reputation of moving through the water at impressive sustained speeds (see George Dyson's book "Baidarka" for the sources. George also wrote an article for Scientific American a few years ago.).
Anyway - one thing they did was to deliberately make the keel flexible by including 'hinges' to divide it into three parts. These were sometimes simple, like a table-leaf hinge, and sometimes more elaborate, with bone ball-joints worked in. In addition, they included bone inserts where major components were lashed to each other ( - deck beams to stringers for example - ), the better to allow them to slip without wear. Where they didn't want slippage, wooden pegs (dowels) were used to locate components rigidly.
The boats were by no means 'floppy', with the hinges being tightly lashed, but there was certainly a degree of 'elasticity' (for want of a better word) that you wouldn't find in a boat made without hinges.
Longitudinal stiffness was provided by the gun'ls, which were each made from one length of wood.
The 3-part keels had nothing to do with building their boats from short lengths of driftwood. Remember that we're in the land of Sitka spruce and excellent timber was available to them, unlike some of the Inuit groups elsewhere in the Arctic.
I've got a lot of faith that evolution over long periods of time can lead to near-optimal solutions, and few artefacts have evolved over a longer period than the baidarka. So whether we can explain it in engineering terms or not, the flexibility of the baidarkas was something that must have paid off in some way, otherwise it would have died out.
On another matter (related) we have an 1827 ship in Dundee harbour - the frigate Unicorn - built at Chatham in 1827 and still 95% original as it was never used in anger. As far as I can tell, it's the earliest ship to have been built using wrought-iron diagonal bracing and knees.
Bill
[Non-text portions of this message have been removed]