Cutting the Rabbet (large vessels)

Introduction

Cutting the rabbet on any vessel is very important, it is where the planks interact with the centreline timbers (stem, keel, stern post, deadwoods etc.), either the planks’ ends or the side in the case of the garboard (first strake next to the keel). They are termed stem, stern or keel rabbet depending on their location.

The process of locating the rabbet has changed little over time, though the introduction of power tools has enabled a few short cuts to be applied. It is a very important joint to get right for the vessel.

Procedure

The process is demonstrated in the accompanying video clips with a step-by-step guide. The conversation with the boat builder, in this case, Chris Rees is unscripted and covers the technique from his experience.

From the lines plan of the vessel, it is possible to mark up the stem, stern and keel rabbet on the centreline timbers. If straight, a chalk line can be used, if there is a curve to it, a batten can be run through and pencilled in.

The above diagram shows the lines plan for the Grayhound and the outline of the rabbet is shown in red.

It is important to realise that the rebate shape changes along the rabbet line. This is shown in the drawing below; a plank was placed on the rabbet line and aligned with the shape of the hull. The red area shows what needs to be cut out to form the rebate.

As the angle between the planking and the keel or stem decreases, the area of the rebate increases. The example above shows a typical bow and midship sections, the midship plank is relatively flat, whereas the bow part shows the twist of the plank.

The red area will be cut out enabling the plank to set in the formed pocket which runs the length of the keel and runs into the stem and stern post. Letter ‘A’ denotes the rabbet line, ‘B’ is called the middle line (also known as ghost line, breading line, back rabbet), ‘C’ is the breading line (also known as the back rabbet). Depending who you speak to, these components of the rebate do vary in their name, however, everyone usually agrees that ‘A’ is rabbet line.

Once the rabbet line has been marked up, the next step is to cut it out. This is done in sections, starting with roughing out the rabbet line and an Arbortech cutter was used for this. The location along the rabbet line will influence the choice of the tool to be used. Adze, power plane, hand plane and chisels are all used to open up the rebate. It is important to check the rebate by using a planking block, this is a block of wood which matches the thickness of the planking being used, all square.

It is a process of removing some material, checking, then removing more material until the rebate has been opened up and planking block lies correctly within it.

Once the rabbet line has been developed on one side of the keel, the second side is done by measuring off the first and cutting to those measurements. Both rabbets should match.

 
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Tools Required

  • Chalk line
  • Electric grinder with arbortech cutter disc
  • Planking block
  • Adze
  • Power plane
  • Plane
  • Chisels
  • Hammer / Mallet
  • Steel ruler
  • Square
  • Straight edges
  • Personal Protective Equipment (PPE)
  • Pencil

Materials Required

  • The timbers used in the centreline timbers are greenheart and oak