Investigation 9 

A personal Account. Paul Constantine

More about Trees 

What does it take to build an Anglo-Saxon ship?

Lots of wood. Oak, to be more precise and to make it usable it has to be quite straight for making planks or individually shaped for chosen locations within the ship, such as ribs or the stem and stern. We might not think that this is much of a problem today, but if you had to chop down a tree, remove the branches and then change it into planks you might think again. The biggest problem, after handling the mighty weight of the tree, would be in not having a saw big enough to cut it up. We might expect that the circular saws we use now have always been around, but they are hardly more than 200 years old, because they need power to drive them. Before such saws we mainly used men-powered saws and it would take so much effort to cut up a tree that splitting the tree was preferred. People noticed the natural splitting of felled trees and helped the splits by knocking wedges into them. Once a tree is split into halves each of them only weighs half as much as the whole trunk and so they get easier to move. If they can be split again, their weight is further reduced. (See The nature of wood, Investigation 8, this website)

 

The wedge-shaped pieces can be reshaped into planks. Traditionally, the tool for this job is an adze. It’s very similar to an axe, but with the blade fixed across the handle rather than along it. This whole lengthy process needs only very simple tools, like the adze and the axe that can be forged by the blacksmith. Even stone-age peoples have managed this whole procedure using stone tools. Apart from these tools you would need people skilled in their use, who know what they are doing, to split, trim and shape, then fix the planks in the form of the ship. With the Sutton Hoo ship we have just the single craft, but it wasn’t the only one, there would have been many more of all different sizes. They have all rotted away with hardly a trace, whereas this one in its unusual location away from the water, left behind a very delicate trace that we have been fortunate to find.

Once the planks are shaped they have to be assembled and this means lots of joining together. As the ship is built it gets heavier and heavier. We noticed that one Oak trunk was almost too heavy to move when it was whole, but now we are fastening many tree trunks together to make our ship. How will we move it to the water? The process is complicated and skilful and it doesn’t end with just the ship. It needs oars to power it and a rudder with tiller to steer it, seats for the crew, ropes and anchors to secure it.

Making a ship and all that it needs, is a mighty challenge, if we do not use electricity or engines; if we use only our muscles and simple hand tools, then we transport ourselves back to face the same circumstances as the people who built the original Anglo-Saxon ship. We have come to respect their skill and knowledge as we too wrestle with the same difficulties that they overcame. Are we up to that challenge?

 

Can sufficient Oak be found to build the ship?

This is a question frequently asked by interested people and fortunately the answer is 'Yes'. To gain an understanding I visited, along with Peter Bradbeer, the Sotterley Estate owned by Miles Barne, near Beccles to meet Andrew Falconer a forester who has contacts covering 5,000 hec of forest in East Anglia and his assistant James BroomWe had been put in contact with Andrew by Esmond Harris MBE a retired director of the Royal Forester Society.

The forestry people were given an outline of the ship project in the estate office and all their questions were answered. They understood that we were trying to understand what the problems might be in seeking timber for the ship construction. The examples we gave them were for a 50ft x 12ins x 6ins keel and, curved timbers suitable for stem and stern. We concentrated on the keel.

Below. A straight tree suitable for planking 

We drove to several managed woods that had been planted at different times to look at the growing trees, to understand their speed of growth. Miles identified the trees by their planting dates. The oldest trees were 1840 and the newest that we looked at were 1936. Each wood is divided into ‘compartments’ that were usually planted at the same time. Miles was very active in taking us to see individual sample trees. He knew them all and he was hands-on-active in making tree selection on a daily basis.

Background

Trees from good quality acorns are sourced from the continent, Netherlands etc. They are purchased as saplings and planted out 6.600 per hectare. If they were 1m apart there would be 10,000 per hectare. After growing for some years the forester walks amongst them identifying the most successful trees. They are marked with a white ribbon. Trees within about 3 - 4m around them are thinned, but some are left growing. The white-ribbon trees have lower branches lopped off. Speed of growth is determined by light; this is why some trees surrounding the selected trees are left alone. They encourage the chosen tree to grow more rapidly to reach the light. Hardwood trees are stronger the faster they grow. Softwood trees are the opposite; slower means stronger for them.

               The trees are left for more years and then the whole process is repeated. More, smaller trees are taken out and more lower branches taken off the selected trees. This produces tall and very straight trees resembling lollipops. Their girth is a mark of the length of time that they have been growing. After a period of about 100 years there will be about 70 selected trees per hectare. The ones that have been taken out will have had commercial uses. Trees to be felled are marked with red ribbons.

Older trees have a bigger circumference and if the branches have been left untrimmed they will have useful dimensions and be much more sinuous. Larger trees are more valuable. Some other species such as hornbeam are sometimes planted interspersed with the oak. Their function is to provide shade at a lower level thus encouraging the oak to reach higher for more light. The shade of the lower foliage also reduces the growth of other plants on the forest floor.

Height measuring

The height is calculated by laying a long tape in the ground with one end at the base of the tree. The tape may be 20m long. Someone stands at the end of the tape and uses an optical device called a clinometer to sight the top of the useful section. A series of figures is produced within the device that by calculation gives the height of the tree.

 

Relevant timber features

A tall young tree that produces a 50ft length within the bole or the butt (trunk) will have a large amount of sapwood, the area of immediate growth around the circumference just below the bark. It will also have the central core, the pith with annual rings circling it. Splits or shakes usually begin in the region of the pith. The area between the pith and the sapwood is known as the heartwood and this is the strongest timber.

             A young tree can be felled and the sapwood area mainly removed to ‘box’ the tree, making it roughly square/rectangular. The pith would remain within the heartwood with the annual rings surrounding it. This does not produce the strongest solution. The strongest solution is produced by having a keel with no sapwood and no pith, only heartwood. This means that it has to be cut from one side of the tree only, between the pith and the sapwood. This means that the tree has to be almost double the diameter and therefore considerably older than the younger-tree solution that included pith. The remaining timber from the tree would not be waste as it could be used for other components of the ship.

Right. Curve more suited to stem/stern

Value

The value of the timber produced depends on various factors. It can be seen that a keel with no pith included must come from a very much older tree and this becomes the prime timber that everybody wants, so it is very much more expensive.

Question. Can the keel be fashioned from younger timber that includes the pith? This saves much money. 

Answer. The answer must come from the experienced judgement of the shipwright and the finance available to purchase the material … but probably the answer will be No.

Question. If the pith is included where should it be positioned? This relates to strength.

Answer. This is a shipwright’s decision.

 

Hoppus Cube

Oak, as a timber is still calculated in Imperial sizes, feet and inches. When it is being sold from an estate it is often 'bundled', that is to say several trees are sold by auction as a single Lot. The size of the Lot is described by the dimension Hoppus Cubic foot. This is a system named after its originator Edward Hoppus that attempt to estimate the amount of useful timber in a round log after 'squaring 'it and cutting it to produce usable timber.

 

Liability

A tree may be identified as having the right qualities. It is cut down, but as it falls it is damaged. When the tree is felled it may be found to have rot, especially in the cruck of branches. Whose liability is this? Is the tree purchased standing? Is it purchased after felling? Such questions need to be determined and contractually agreed before cutting. This is especially true of grown-ribs ship's timber where selected forks can be shattered on hitting the ground. To avoid breakages it may be required to control the fall of the tree with ropes. This will be more expensive.

 

General

Selected trees in any one compartment will come to commercial use at roughly the same time. The owner may then decide to clear the compartment, so that it can be reused by planting saplings. When a compartment is cleared there are adequate supplies of timber and its price will reflect this. If a single tree is selected to be felled in a compartment, extracting it may be more expensive as other trees may have to be removed around it, to clear its fall. In one or two places there were huge trees. The owner referred to them as ‘monuments’. They were sometimes located to define the boundary of a compartment. They were retained to illustrate the magnificence of mature trees and for the pleasure of the owner when looking at them. They would not be cut down.

Purchase process

There are separate steps:

• Find suitable timber (shipwright & foresters) and reach agreement on liability

• Agree cost price • Determine transport arrangements (removal from wood & on road) to arrive at total cost

• Find finance/sponsorship                                    Tree 01547 known as 

• Commission timber to be supplied                        a 'MastOak' felled

   

      Above. The estate found a tree

       perfect for the keel of the ship

        Tree 01547 Clear for 50+ft    

Waste

If the quantity of timber required for the ship is calculated in (say) cubic feet or meters, then allowance must be made for wastage. Traditionally this is quantified as about 50% which doubles the amount needed. It remains a ‘best-guess’ figure even today, but much depends on the way the timber is converted (made into planks) and it is not clear whether the figure relates to the whole tree or after boxing etc. If a tree is converted by cleaving 25% and using more modern methods for the remaining 75%, the wastage will be different from using modern methods for 100%. Quartering by modern methods will be more expensive than cutting straight through, and produce more waste.

 

Sourcing

The forestry people were quite confident that all the timber could be sourced from their woods. They said that they would be disappointed if we had to go outside this country, because that would not be necessary. We did not talk about specific prices, because there are so many factors that would eventually determine a final cost, but a ballpark figure was suggested for a 50ft tree. Was this for young or mature? Later - (See illustrations above)

It is desirable that outline timber prices should be gathered from several places. 

            Timber should only be acquired as it is needed. There is restricted storage space at the build site. It must be worked green when it is soft and pliable. It is preferable to keep it cool and damp. A 6 year build time is envisaged and during this time, the material will harden, shrink and split unless it is carefully managed. How much timber is needed? this is a 'How long is a piece of string.' question. Sometimes it is phrased as 'How many trees will it take?' The easy answer is 'It depends on the size of the tree.' Let us take a look at some statistics relating to Viking craft. This comes with a warning. The Anglo-Saxons came before the Vikings historically and it would be a mistake to relate all things 'Viking' to people who were living 2-300 years before them.

 

Historically speaking it is not safe to backdate knowldege.

 

With this knowledge we can take a glance inside a book

The Viking World. James Graham-Campbell. 1980 (Professor of Medieval Archaeology University of London. Contribution from R. I. Page Professor of Anglo-Saxon at University of Cambridge. Emeritus)

Timber quantities. (Page 50-51)

(My explanatory comments are italicised in blue. P.C.)

Planking. (straight timber, no low branches, no spiral grain)

An average of 20 sound planks, some 12” (30cms) broad can be produced from a log 39” (1m) in diameter.

Ole Crumlin-Pedersen (A highly respected historian/archaeologist with a vast range of knowledge and experience) calculated that 1,765 - 2,050 cub ft. (50-58 cub. m.) of oak is required to build a 65 - 80ft (20 - 25m) ship. This would be equivalent to about 11 trees each 39” (1m) in diam and 16ft (5m) length of trunk, together with another tree 50 - 60ft (15-18m) for the keel. (These are not the dimensions of the Anglo-Saxon ship that had only 9 planks a side whereas the quite differently shaped Viking sailing ships had 11 – 16 planks per side.)

These timbers to be split radially using hafted metal wedges.

The wedge shape of the planks are suitable for clinker building as there is more wood on one edge for the cutting of the bevel where the planks overlap. (An important point to note.)

Keels, keelsons, crossbeams.

Mast, yard, (for sailing ships), oars (from different softwood timber).

Other components.

There are many and most do not require straight timber. (Very important to note this. There is a huge distinction between timber for planking and all the other timber for components such as these below. See the note on Frames for Sea Stallion.)

Some curve. Stem, stern.

More curve. Ribs, Crooks, Tholes, Knees.

Miscellaneous. Treenails, wedges, rudder, tiller, rigging blocks, gangplanks, bailers.

For building.

Clamps, battens, stakes, shores, skids and launching ways.

Timber is cleaved by a specialist team, possibly ‘at stump’ ie. in the forest and delivered to the builders. It is used ‘green’ i.e. not seasoned. Any timber not immediately required is stored underwater.

Other raw materials.

Iron. Anchors, nails, roves

Leather.

Hemp (or other caulking material)

Pine Tar for waterproofing.

 

Roskilde

We can now look at information provided relating to the construction of ‘Sea Stallion of Glendalough’ a sailing ship of 29.4 m length weighing 9.2 tonnes. This is bigger than the 27m Sutton Hoo ship, but the two craft are roughly comparable. This ship is also known as Skuldelev 2 from the place where it was discovered along with other craft.

The figures for this craft are as follows:

The rough total of timber used for the ship is 350 cubic meters

Planking 14 oaks 8 -10m in height, 4 ash (for oar-port planks, not used on Sutton Hoo) 10m height, 1m diam. at chest height

Keel, keelson, stems, mast partners (for sail), 6 oaks, 8 -10m height

Frames 285 pieces of naturally-grown curved oak timber

Oars Pine

Trenails 10 willows 20-25cms diam. at chest height.

Edwin Gifford (See Sae Wylfing on this website)

When preparing costings for the projected construction of the ship in 2004 noted:

Timber for planking keel and thwarts 6 trees.                                                                Unmanaged Oak

                                                                                                                                                Impossible for planks

So here you have some basic information from which work and                       Possible for tholes 

although it began as a ‘How long is a piece of string?’ question,

it should now be possible to develop it a little further as the following has been learned

Wood for planking, for the keel and gunwales has to be straight and this implies the easiest source would be from managed woodland. This is legitimate as there is strong evidence that the Romans were already using managed timber before the Anglo-Saxons. At the time of the original build forests were much more extensive and trees in enclosed locations would grow straighter as they seek the light.

Wood for Stem, stern, ribs, tholes, knees and rudder support must be shaped and this will be found in more naturally-grown open woodland or park land. Timber for this purpose will have to be individually selected and will be more difficult and time-consuming to find.

                                                                                                                                                                                                     

Ole Brixen Søndergaard who has been an integral part of the Nydam Two (Tweir project in Denmark, had been an invaluable adviser to the Anglo-Saxon ship project and he has drawn attention to other aspects to be considered relating to wood. Their project used many modern methods in the construction. This is some of his advice.

Just-in-Time

In order to work in fresh timber as far as possible the tree trunks were cut down as the logs were required. The logs were stored outdoor at the sawmill. They were delivered as sawn planks, in the quantity we needed, one-by-one to the building site and fixed in their correct place in the hull, in reasonable time.
             The remaining planks were stored outdoors on the ground, so they could suck up moisture to prevent drying out, covered up with solid plastic, in shadow, until a new delivery was asked for. The same system was used for other types of timber. Don’t cut down, as far as possible, before there is a need for the material. Trustworthy suppliers are valuable. Members of the Nydambådens Guild also kept a lookout for useful trees in the landscape and in woods, especially so, for the shaped timbers to be used for e.g. rowlocks, oars and curved timber (which were very difficult to find) for the framework/ribs.         

           You are using cleaved planks and I would advise that you do not to take too long in working them and fixing them one-by-one to the hull and in keeping the stored wood in naturally humid conditions until you need a new number of planks. This system has worked well for us for the 6 years it has taken to build Nydam Tveir. As soon as the planks were fastened in the right place in the hull we saw no problems as the planks slowly dried. The barn used as the building site was unheated and well ventilated. We only had a few deck boards that went too dry - solution - give them a bath overnight in a big plastic sack with water.

Warning!

Look out for dry-rot in the planks. We discovered dry-rot in part of the stern cutwater plank and it was decided to renew the part immediate, a hell of a job. (Dry Rot is a fungal attack and the chances of the fungus finding the wood will be increased if it is laid on the ground. It should not be forgotten that wood is a natural material that provides food for many insects and organisms that have evolved to live on it and break it down. The fungus relies on water and its latin name includes the word 'weeping' to signify this.)