British Knees

(first published 14th May 2005)

A tutorial on knees - not the thing halfway between your foot and your naughty bits, but the wooden boat variety. Basically a knee is a wooden triangle which supports or reinforces two other bits of structural woodwork which meet (at approximately a right angle) in a wooden boat. Think of it as a bracket. Now, because wood has a grain and because wood is normally stronger along the grain rather than across it, knees need to be thought about. In fixing the main thwart in Lugg I will be using hanging knees, which is to say that the knees will be above the thwart, hanging it from the gunwale. To avoid the wood splitting under stress I have used oak instead of softwood - much tougher - and I’ve cut the knees so that the grain runs diagonally.

You can see from the diagram that when the grain runs vertically, if the wood splits, the thwart would detach from the gunwale; whereas if the grain runs diagonally the thwart will not become detached even if the wood splits.

In the photo you can see at top right the triangle of oak I cut for each knee, then the paper template I made up for the actual shape required and at bottom left the knee cut to (more or less) its final shape.



In this photo you can see the knee roughly in place (I’ve doctored this pic a bit to remove all the props and wedges I used to hold the knee temporarily in place). You can also see the direction of the grain. QED.



Today we have mostly shampooed all the carpets in the house and mowed the grass - not much boat time - and I'm tired now, so cheap epoxy putty (special recipe) next time. A bientot.