“A traditional Arab sewn plank boat with sails can be made from the coconut tree alone as ‘coir’ the fibrous husk of the nut is fashioned into ropes and sails, while the dried nut kernel yields an oil which can be used to waterproof the planking.” McGrail (1987, 24) identifies that the many species of wood differ in attributes such as density, run-of-grain, average length of bole, strength, resistance to splitting, durability and shrinkage. It can therefore be ascertained that certain species of wood are more suitable than others for particular uses. Wood is also ‘anisotropic’. This creates variation in the strength and shrinkage of the wood depending on the “orientation of the cells.” (McGrail, 1987, 24) It is imperative that this factor is taken into consideration when fashioning a particular artefact from the bole, branch or root of a tree. There are many advantages in using timber for water vessels. Timber is water-resistant and can be treated with waterproofing mixes to increase this property. It is relatively easy to work with and can be converted, fashioned or bent into a variety of shapes, however attention must be given to the nature of the grain or this could spell disaster! Different parts of the tree can be matched to the various strength requirements of the different elements of the boat. (McGrail, 1987) It would therefore appear that boat-building is a highly skilled task in which knowledge of the properties of wood is essential. Selecting and collecting wood is also important. In the ‘Heimskringla’ the medieval Icelandic author Snorri Sturluson described the building of Olaf Trygvason’s ship ‘Long Serpent’ and noted that,
“All timber that was used was selected very carefully.” (Foote & Wilson, 1970, 52)
It would appear that within the range of timber species available individual trees were selected to match the type of boat and its purpose. In essence however, this could mean that a region could be exhausted in a type of wood. Christensen (1968, 72) has remarked that oak was abundant in northern Norway while pine and beech were found in the south during the medieval period. Within northern and western Europe from the Mesolithic onwards a wide range of species of wood was available and used by man in prehistoric Britain and Ireland. Heal (1978, 25) argues that oak, ash, birch, elm, hazel, alder, beech, yew, lime, willow and pine are known to have been used in boat-building in north west Europe during the Prehistoric and medieval eras. In general oak appears to have been preferred for the main structural elements of boats. Evidence, which shows this is from the Ferriby boats, dated to the middle of the second millennium BC and also the early fifteenth century ships. The sample of boat finds is undoubtedly biased as oak has a greater chance of survival than most other species. Converting a tree for usage as a boat-building material is extremely important. Moisture is present in fresh wood and after felling a tree begins to dry causing the moisture content in the wood to change. (McGrail, 1981, 28) This effect on the wood also causes shrinkage, which in turn may cause distortion and result in the timber splitting. McGrail (1981, 28) suggests that early boats were built of unseasoned timber and a protective coat of tar or resin was used to reduce shrinkage. After selecting the wood type and endorsing the appropriate procedures to prevent shrinking, the next stage is planking. ‘Planks’ of wood are shaped from logs. Strips of bark are removed and a spilt is made using ‘oak’ wedges along the section chosen of the log. (Meharg, per. com) The remaining bark along with the outer sapwood is removed and the inner surface of the log is worked until a plane surface is obtained. (Meharg, per, com) Planking argues McGrail (1981, 29) is required for the central parts of larger boats, this must be long and straight. However, in the case of smaller boats, such as a fishing yawl, planking is rarely parallel-sided. The planking is worked so that its curve follows the natural curve of the grain, ensuring maximum strength. (refer to figure 2.10)
