knee

Recall that all wood has growth rings which happen to be places of weakness in the wood.  These rings are represented in a piece of lumber as its grain.  If you simply cut, say, the stem of a boat out of a straight grained board:

               ___
              |///|
              |///|
              |///|
              |///|
              |///|
              |///|
  ___________/////|
 /////////////////
|////////////////

you're placing the wood's weakest area at the point of its greatest stress.  Your boat will sink in the first storm.

So, ideally, you want the grain to follow the curve of the wood:

               ___
              |||||
              |||||
              |||||
              |||||
              |||||
              |||||
  ___________/////|
 /-----------'/////
|----------------/

Ok, so wood grain is hard to represent in ASCII.

How do you get a piece of wood like that?

• Steam bending.  Place a length of green wood in a steam box for a period of time, until it gets soft, then bend it into the shape you want over a frame.  This can be done for smaller knees, such as the seat supports in a small rowboat, but green wood can't really take a lot of stress.
• Lamination. In other words, take strips of wood and epoxy them together, creating in effect a bent chunk of plywood. Of course, epoxy hasn't always been around, and really treats a plane harshly.
• Grow it that way, or find a piece of wood that grew that way naturally.  These are the most satisfying knees to use.  Smaller knees can be made out of the crooks of apple or cherry trees.  Although you can get larger knees out of the places where hardwood (usually oak) trees branch, the hackmatack (aka tamarack or larch) tree grows in a most fortuitous way. Of course the trunk is upright, but a larch has a horizontal tap root, making the whole assembly shaped like, you guessed it, a knee.

Knee (?), n. [OE. kne, cneo, As. cneo, cneow; akin to OS. knio, kneo, OFries. kni, G. & D. knie, OHG. chniu, chneo, Icel. kn, Sw. kna,Dan. knae, Goth. kniu, L.genu, Gr. , Skr.janu, Cf. Genuflection.]

1.

In man, the joint in the middle part of the leg.

2. Anat. (a)

The joint, or region of the joint, between the thigh and leg.

In the horse and allied animals, the carpal joint, corresponding to the wrist in man.

3. Mech. & Shipbuilding

A piece of timber or metal formed with an angle somewhat in the shape of the human knee when bent.

4.

A bending of the knee, as in respect or courtesy.

Give them title, knee, and approbation. Shak.

Knee breeches. See under Breeches. -- Knee holly, Knee holm Bot., butcher's broom. -- Knee jerk Physiol. a jerk or kick produced by a blow or sudden strain upon the patellar tendon of the knee, which causes a sudden contraction of the quadriceps muscle; one of the so-called tendon reflexes. -- Knee joint. See in the Vocabulary. -- Knee timber, timber with knees or angles in it. -- Knee tribute, or Knee worship, tribute paid by kneeling; worship by genuflection. [Obs.] "Knee tribute yet unpaid."

Milton.

© Webster 1913.