Knees!

Today we’ll look at knees.

Nope, not these. Ouch.

These.

Knees are like angle brackets for boats. They provide support and stiffen the structure. For a boat the size of the Morgan, we need really big knees.

The thing that makes a piece of wood suitable for knee stock is that the grain has to follow the curved shape of the knee. If the grain doesn’t follow the curve, the knee will be substantially weakened.

We use the term “grown knee” to describe knees where the grain naturally grew in the shape that we want. In the rough, they may look like this.

or this.

We’re always on the lookout for suitable knee stock here. Considering the size of many of the vessels at the museum, it’s good to keep a stockpile of suitable candidates at hand.

When we find one that we like, we’ll start by sawing or hewing the sides parallel. Then we’ll shape it to fit a pattern. Here’s Walt working on one, shaping the inside curve with an adze.

Photo credit: Evelyn Ansel

Photo credit: Evelyn Ansel

John has been the main knee guy on this project. He’s been working down in the hold to replace the knees that were removed when the new ceiling was installed. The process starts with making patterns. John first copied the shapes of the existing knees.

He could then take these patterns out to our stock piles to look for suitable rough stock.

He also made a second pattern based on precise shape of the ceiling and deck beam at the location of each knee. Here’s where a knee goes,

and here are some patterns.

These patterns give more precise information about the exact shape of the ceiling and deck beams where the knees will be installed. He can also use this information to get the bevels (the fore-aft angle of the knee face to the curve of the hull) as they change going up the knee.

Once he’s found suitable stock, he has at it with chain saws, band saws, adzes and hand planes to get the shape he wants.

It’s a slow process, but the we’ve now got a hold full of knees.

It’s now final fitting time. Even after all the patterning, there’s always a little bit of fine tuning to get the knee to fit exactly right against the ceiling and deck beam. Roger recently came up with a nifty jig to help in this regard. It’s a little tough to see here, but I’ll try to explain.

The jig is made up of two staging planks with a gap in between them. The knee fits up into that gap.

Here it is in action

 

A little clarification may be in order. Zooming in…

The knee (green arrow) has a hole drilled through it, and a bar is inserted through that hole (red arrow). Blocks of wood with holes in them are also threaded onto this rod, one on each side of the knee. When the staging planks are lifted up into position, the knee hangs from this rod. To raise the knee, wedges are inserted under the wood blocks. The fact that the knee is hanging in the slot created by these two staging planks means that the knee can be slid back away from the hull. This way, John can fit the knee up against the hull and deck beam, determine where he needs to adjust the mating surfaces, slide the knee down and back, and work on it. The knee weighs hundreds of pounds, and this jig it makes it possible for one person to do this fitting on his own. Nice going, Roger.

By the way, when knees are oriented vertically, they’re called hanging knees. When they’re horizontal, they’re lodging knees. You can see both kinds in that early photo. The lodging knees are up high.