Tim Kirk’s Shipwright’s Report for February

This month progress on the build has been very limited because of lockdown restrictions.  This report is about essential work that we are doing to source wood for the hull, frame and oars that will make the ship a strong, seaworthy vessel.

Readers of previous posts will know that we already have already obtained a straight grained oak log for the keel and another fine one to begin forming the curved ends of the ship.  Most of the rest of the timber needed for the hull is in two forms:

  • long clear runs of oak from trunks 6 metres to 9 metres in length and up to 1.2 metres diameter for planking and other longitudinal timbers, and
  • curved timbers up to 4 metres long and 0.4 metres diameters for frames or ribs

We will also need multiple smaller sections.

Oak for planking and longitudinal members must be straight-grained and clear of knots, shakes and other defects.   The twist in planks from trees that have grown with twisted grain (shown by spiralling of the bark fissures around the trunk) is not acceptable for constructing most of the ship.  But we do need just one length of timber with a twisted grain, about 6 metres long and 0.9 metres in diameter for the end pieces of the lower planks.

Twisted grain in a cleaved log

The framing of the ship is built up from multiple pieces of curved timber:

  • floors, which cross the centreline and provide much of the transverse strength
  • futtocks, which attach to the floors and frame sides of the ship; and
  • rongs, which combine a floor and a futtock.

Combinations of these frame sections, regularly interspersed along the length of the ship, minimise the weaknesses caused by scarfed joints and maximise the athwartship strength.

These timbers, made from curved trunks, or larger branches from the lower canopy of the tree, need to be up to 3 metres long and 0.5 metres diameter.  For strength, ideally we need to avoid using the central ‘pith’ and the outer ‘sapwood’.  However, there is some archaeological evidence from other ships that both the centre of branches and sapwood might sometimes have been used.

The key requirement to maximise strength is that the curvature of the grain in the frames meets the natural curve of the ship. This means that we have to place individual full-size patterns against the timber that we are planning to use to assess whether it is suitable.

The photo on the left below shows a frame section fitted to our full-scale model of the ship.  The softwood molds in the background are temporary. The drawing on the right shows the different frame sections and their placement within the ship.

We need larger curved sections to form the stem and the sternpost .  We already have one suitable trunk but we will need at least one more – up to 6 metres long.  The trunk in the photos below (shown standing and felled|) is 10.8 metres long and 0.9 metres diameter – big enough to obtain two pieces, one from either half of each length of timber.

We have made full-size patterns to test against potentially suitable trees.  We hope to find a group of suitable trees on one site as this would save time and reduce the costs of transport.

Other, smaller curved pieces will come from smaller branches in tree canopies.  This sort of timber isn’t easy to obtain as it is not commercial for timber yards and is often cut up for firewood.  The photo on the left below shows grown a ‘crook’ , needed for the end frames of the ship, and on the right a branch junction that will be used for making ‘tholes’ (where the oars pivot on the gunwale of the ship).

We need about fifty sections like these – each about 1.2 metres long and 0.3 metres diameter.

Oars – we will need about sixty in total, including spares and different experimental designs.  Although tholes (primitive rowlocks) were identifiable in the Sutton Hoo Ship excavations there was no evidence of oars. We have found out as much as possible about what the original oars might have looked like but there is a lot to be done on shape, weight and pivot points. This is a case where experimental archaeology comes into its own – all these issues will be covered in detail in a future research paper.

Initially we will trial different materials – oak, ash and scots pine – making about six of each type. The timber for oars needs to be straight sections about 6 metres by 0.2 metres with no knots or other defects.  Larger diameter timber could be used to make several oars from each trunk. Once we make a final decision on what sort of trees to use we will need enough wood for forty oars.

Other parts of the ship will come from offcuts of the larger sections.

We expect to use the equivalent of around twelve mature oak trees to build the ship.  Although this will undoubtedly require more than twelve trees to be felled one of our key targets is to replace each tree we use with ten saplings.

Tim Kirk, Master Shipwright