Knees are an imme­di­ate indic­a­tion of the boatbuilder’s abil­ity to make good look­ing shapes. 

Ideally one would like to use an oak crook. However, in these hon­est times, crooks are pretty hard to come by and also must be well seasoned before use, par­tic­u­larly if there is to be some con­fid­ence that they will not be caught. Half-lap­ping is a reas­on­able altern­at­ive and has the added bene­fit of being eco­nom­ic­al in tim­ber use. Thwart knees should be one inch thick. Machine tim­ber appro­pri­ately, half-lap and glue together. 

Consider the ori­ent­a­tion of the knees so that the joints will all appear uni­form port and star­board. For example you may want to see the hori­zont­al joint of the half-lap when look­ing at the dinghy from for­ward and the ver­tic­al joint when look­ing from aft. In order for this to come about the port side half-laps will have to be cut in the oppos­ite ori­ent­a­tion to the star­board side. 

Each cent­ral thwart has two knees per side, the for­ward thwart one knee and the after thwart no knees.

At each bay between the ribs where a knee will be loc­ated, fit pack­er up between the gun­wale and plank­ing. If this is for­got­ten, when the rivet is tightened in the knee head it may crack the plank, as the plank can be pulled into the fresh air between the plank and gunwale.

Plane the under­side of the knee foot flat. It may also have to have a slight bevel. Push it out­board until it touches the gun­wale and clamp it in position.

Make a chock of wood the size of the gap between the inboard face of the gun­wale and the inboard face of the plank­ing. Use this chock to trace the shape of the boat onto the knee. This can also be done with a pair of dividers.

Cut out to the line. The knee on the for­ward thwart will be square to the hull and is easy to cut on the band­saw. The knees on the cent­ral thwarts will have a bevel where they touch the hull because they line up with the thwart which is square to the centreline yet the out­line of the boat is a curve.

Either use hand tools, a jig saw with a bev­el­ling foot, or bevel the band­saw bed. Inevitably, get­ting the knee bevels to fit is time consuming.

Fit all of the thwart knees before shap­ing the curved face. Shape one knee and use it as a tem­plate for the others.

The head of the knee is square; it stands proud inboard of the gun­wale ⅞in. The body of the knee must not be par­al­lel with the plank­ing oth­er­wise it will seem too upright. It must gradu­ally increase in width until it curves into the foot which is gradu­ally taper­ing, nar­row and long; in essence it must be elegant.

A sand­ing drum in a drill is use­ful to smooth the curve of the knee; knobbly knees are never attract­ive. Put a light cham­fer on the edges of the knee.

Once the knees are shaped a pair of 13G riv­ets may be put through the half-lap so that should the glue fail in sev­er­al dec­ades time, the knees will hold togeth­er and do their job. Consider the ori­ent­a­tion of the riv­ets so that they are all facing the same way.

Glue the knees into the boat. This will serve two pur­poses: firstly it will pre­vent water wick­ing under the knee and sit­ting atop the thwart which will even­tu­ally lead to decay, and secondly it will make it much easi­er to fasten the knee in the exact pos­i­tion that you want it to sit.

Check the double knees from the oppos­ite side of the boat to ensure that they are par­al­lel and also to ensure that the gap between the knee and the edge of the thwart is parallel.

To fasten the foot of the knee, drill down through knee and thwart. Make sure that the fasten­ings in the knees are all drilled the same dis­tance from the knee’s toe.

Lightly coun­ter­sink and drive a 10G 2½in or 3in nail down through knee and thwart. Leaning on the nail head, clench or bend the nail over into the grain under­neath the thwart. This is a neat­er meth­od than riv­et­ing; nobody likes to see a pair of limpets on a thwart foot.

To fasten the head, drill out­ward angling the drill down slightly so that the nail head is below the upper rub­bing strake. If the knee is one of a pair drill its neigh­bour at the same time, mak­ing sure that the angle of the drill is the same so that the nail heads are in line on the out­side. Rivet the knee head with a 10G nail and 7/16in rove.

In the plank below the sheer plank, drill through from the out­side of the boat into the back of the knee. Countersink the hole and drive in an 8G by 2in bronze grip­fast nail. If the dinghy is a lar­ger sail­ing dinghy she may also need a second grip­fast nail through the sheer just above the cove line.

As with the thwart knees, the gun­wale must be packed out in way of any breast hook or quarter knee fasten­ings. The quarter knees have two riv­ets in each arm. The arm along the transom is slightly longer than that on the gun­wale. The arm on the transom must be lif­ted slightly above level. If level, the quarter knees look like the ears of a sad dog—downcast.

The breast­hook has two riv­ets in each arm. To look right the breast­hook arms must be longer than one might think they need to be: twelve inches for a breast­hook arm is not too long. If she is a sail­ing dinghy she must have an addi­tion­al rivet through the stem head and centre of the breast­hook. The arms of the breast hook and quarter knees need to be long and tapering.