> Did they put the ivory in there to enhance the flexibility, or is it there
> to protect the wood when it flexes?

> If you are building a boat with a light weight frame, it is going to flex
> even without the ivory joints. With all that motion, joints are going to
> be subject to a lot of wear. It would be a good idea to protect those
> joints with wear resistant material.

> There is no way of knowing whether the Aleut put the ivory there to
> enhance the flexing or to protect a frame that already flexed. However,
> the ivories shown in the Scientific American article are not well suited
> to enhancing the flexibility, but would do a good job of protecting a
> joint with a lot of stress.

There are generally two classes of bone inserts, flat ones and flattened oval ones. Whereas the flattened ones could be construed to reduce wear another function could have been intended here, some have stated that noise reduction may have been the main reason as the kayaks were generally hunting craft.

The flattened oval ones seem to be found mainly in the keelson joints and the socket usually has a loose fit on the ends and a tight fit along the edges. This would imply the joint was intended to allow some axial (end to end) motion while restricting somewhat the ability of the joint to rotate from side to side.

Bram