1Archaeological excavations at the Islamic site of Al Baleed have brought to light numerous ships’ timbers dating to the medieval period (Belfioretti, Vosmer 2010). The site, facing the Arabian Sea and located near the modern city of Salalah, southern Oman, was an important maritime trading centre in the Indian Ocean during the 11th-16th centuries AD (Zarins 2007, p. 316). Called Zafar in historical sources, Al Baleed was renowned for exporting Arab horses to India and for the production and trade of frankincense (Zarins, Newton 2017, p. 65–66; Costa 1979, p. 111).
2Following the preliminary study by Belfioretti and Vosmer (2010) of five timbers discovered between 2006 and 2009, recent archaeological excavations, which resumed in 2016, have brought to light more ships’ remains, raising the number in the collection to over 50 specimens. Overall, the timbers discovered at Al Baleed exhibit the distinctive features of the western Indian Ocean sewn-plank technique: continuous sewing through holes drilled along the edge of the planks, fibre cordage, dowels, decoration and luting material (Prins 1986, p. 100, 163). The timbers were removed from sewn watercraft that sailed off the coast of Al Baleed during the 10th-15th centuries and reused as structural components, such as lintels, shelves, beams and ceilings in the buildings of Al Baleed’s citadel (husn).
3Knowledge of vessels that sailed the Indian Ocean during the pre-modern Islamic era (622–1500 CE) is still relatively limited and mostly relies on textual descriptions of European, Arab and Chinese travellers who journeyed through the region during this period. Their accounts are unanimous in describing sewing as the primary fastening method of western Indian Ocean ships (Procopius, Bell. Pers. I, 19, 23-25, translated by Dewing 1914, p. 183; Mookerji 1912, p. 31; Moreland 1939, p. 66–74; Prins 1986, p. 66–67; Agius 2008, p. 161), but are often vague and provide little details. References to sewn vessels appear as early as the 1st century AD when they were recorded in Azania (East Africa) and Omana, along the Makran coast, by the anonymous author of the Periplus Maris Erythraei (Casson 1989, p. 63, 141).
4In the 9th century, the geographer Al-Ya’qubi stated that sewn ships sailed the long journey from Ubulla to China (Agius 2008, p. 162), while a century later, the historian Al-Masudi describes Abyssinian watercraft that were fastened with fibre ropes (De Meynard, De Courteille 1861, p. 365).
5Later, in the 13th and 14th centuries, accounts of missionaries, merchants and travellers supply further descriptions of sewn-plank vessel construction in the region. Marco Polo provides one of the most detailed, but also the most dismissive account of sewn boats used by the merchants of Hormuz (Moule, Pelliot 1938, p. 36). During the same period, Ibn Battuta describes the process of making the coir ropes that were used as fastening cordage in the hulls of boats in Yemen (Agius 2008, p. 163).
6A transition in fastening techniques, from sewn to nailed construction, is generally assumed to have gradually taken place from the 16th century, following Portuguese expansion in the Indian Ocean (Johnstone, Muir 1962; Moreland 1939, p. 179; Hourani 1963, p. 93). However, references to sewn watercraft in the region continue well into the 20th century (Foster 1949, p. 73; Markham 1877, p. 6; Pâris 1843; Villiers 1952, p. 40).
7Iconography is also scarce and consists of a few stylised images of vessels, the most famous of which are the 13th-century illustrations from the Maqamat Al-Hariri (Hourani 1963, p. 8, fig. 7; BNF, MS Arabe 5847).
8To date, archaeological work related to sewn boats has also been relatively limited. The most relevant is the 9th-century Belitung shipwreck, which Michael Flecker surveyed for six weeks during salvage operations in 1999 (Flecker 2000, 2010). In Egypt, a few Islamic sewn-ships’ timbers were discovered during the excavation of the medieval necropolis of Quseir al-Qadim, in 1999-2003 (Blue 2006; Blue et al. 2011). In addition, a recently discovered wreck in Thailand, known as the Phanom-Surin wreck, promises to provide interesting information, but excavations have currently been stopped and very little has been published (Guy 2017; Jumprom 2014; 2019).
9One of the most significant bodies of evidence in Oman, which has previously received little attention, is the collection of timbers at the site of Al Baleed. These consist of over 50 remains, 36 of which have been identified as hull planks.
10None of the planks in the Al Baleed collection is entirely preserved. Their surviving length ranges between 230-2500 mm with the major part (79%) measuring between 500-800 mm. Planks Wo98A, Wo98B and Wo98C are the longest and are located in the eastern wall of the citadel where they were re-used in the locking system of the gate. Unfortunately, no accurate measurement could be made due to limited access, but the estimated length of the recess in the wall is 3.4 m (Belfioretti, Vosmer 2010, p. 115). Only two timbers have preserved one of their original ends, entirely in the case of BA0604128.73 and partially in Wo86. BA0604128.73 is a portion of a composite assemblage of three planks sewn together (Belfioretti, Vosmer 2010, p. 114). These planks, which are on the same strake, are connected at their edges with a plain scarf at an angle of 167˚ with a blunt shoulder (nib) at one of its ends. Timber Wo86 is the only other sample of the dataset displaying one end forming an angle of 152˚ with the plank’s edge (fig. 1a). The overall thickness range of the Al Baleed planks is between 22-59 mm. Planks between 20-30 mm and 40-50 mm thick are the most common, with 11 samples (28%) each.
Fig. 1: a) Timber Wo86 displaying holes evenly spaced along the edge of the plank associated with rebates, and an oblique end, b) Timber BA01.11.01 showing sewing holes without rebates.
11Only ten planks in the collection have retained both edges, and they have a width of between 90-303 mm. The remaining planks, which have either only one edge preserved or no original edges at all, range between 60-285 mm in width. They were probably cut prior to reuse in the citadel, or they had gone through a process of deterioration.
12Holes in planks can be distinguished between those drilled along the edges, which are used in plank-to-plank sewing, and those in the centre, which are used for frame lashing. The diameter of plank-to-plank sewing holes often varies both between planks and within the same plank, and measures between 6 and 15 mm. The majority of the planks (78%: 28 planks) have holes between 10 and 13 mm in size, with 12 mm being the most common (22%: eight planks). Spacing between holes ranges between 32 and 113 mm. Fifteen planks, representing 42% of the collection, have holes 70-80 mm apart, and their distance from the edge of a plank can vary considerably. Wo82 displays the longest distance, at around 70 mm, while the closest holes to the edges are those on BA1104065.450 and BA1104065.454 with a 14 mm average.
13Planks can be distinguished between those exhibiting rebates small channels on one of their surfaces, which are associated with the sewing holes (fig. 1a), and those without such rebates, illustrated by BA01.11.01 (fig. 1b). Rebates are carved perpendicularly from the holes to the edge of the plank in 31 planks (86%), and stitching ropes and fibre are still visible recessed in them. Their width is always smaller than the hole diameter and ranges between 3 and 10 mm. The average depth of the rebates can also vary significantly within the timbers, measuring between 4 and 19 mm. Wooden pegs, used for plugging the sewing holes and locking the cordage ropes in place, are preserved in many of the timbers (72%; 26 planks).
14Two timbers (BA0604128.73 and BA0604128.74) retain portions of sewing, providing information about the fastening technique, technology and materials (fig. 2). The sewing cord used in plank BA0604128.73 consists of three ropes with a diameter of 4 mm. The cordage is threaded through matching holes drilled along the edge of adjacent planks in continuous sewing. On one side, the sewing cord is recessed in rebates carved between the holes and the edge of the plank, forming a pattern of vertical disconnected stitches (I I I I). On the opposite side, a thick caulking roll (wadding) is firmly compressed over the seams of the planks by a series of vertical and crisscross stitches (IXIXIXI). The wadding, measuring 43-54 mm in width and 12-16 mm thick, is made of approximately 20 ropes running longitudinally along the plank seam.
Fig. 2: The section of the sewing preserved on timber BA0604128.73
15Twenty-five of the Al Baleed timbers display patterns of holes in the centre of the plank between the two rows of plank-to-plank sewing holes (fig. 3). These are drilled perpendicular to the plank’s surface and are arranged in pairs aligned transversally to the plank’s length. The holes are generally connected by vertical rebates and always share the same timber’s surface with the recesses of the sewing holes along the edge, and occasionally display ropes and fibres in situ. The hole diameter varies between 6 and 20 mm, with 11-12 mm, the most frequent, being observed in 14 planks (56%). The distance between all the closest pairs of holes ranges between 36 mm, recorded in BA1104065.454, and 215 mm displayed on Wo63. The most common distance is between 81 and 100 mm (40%; ten specimens). The distance between these sets of holes ranges between 373 mm in Wo83 and 55 mm in BA01.11.01, with the most significant number (30%) between 143 and 171 mm.
Fig. 3: Timber Wo54 with series of vertical stitches in the centre of the plank’s outer surface, indicating frame lashings
16The vast majority of the planks (89%; 31 timbers) display dowels or their channels on the plank’s edge. These were driven obliquely from the outside of one plank into the adjacent one through their faying edges. Their ends, protruding from each side of the hull, were cut flush with the plank’s surface. The diameter of the dowels varies between 5 and 22 mm, with 11 mm being the most frequently observed in 16 dowels (21%).
17Traces of a black substance are visible on 14 planks (41%), and usually located on the faying edge of the timbers and between the stitching holes and the edge of the planks on the surface without rebates. In a few cases, this material was smeared on both the whole surfaces of the planks. The best examples are BA1104065.454 and BA0604145.175, which have a thickness ranging between 2 and 5 mm (fig. 4). Chemical analysis carried out by Dr Jacques Connan at the Laboratoire de Géochimie Bioorganique Louis Pasteur, University of Strasbourg, confirmed the identification of the substance extracted from seven planks as bitumen (Belfioretti, Vosmer 2010, p. 113; Jacques Connan, personal communication 02/04/19).
Fig. 4: Timber BA1104065.454 with traces of bitumen between the sewing holes and the edge on the inside of the plank
The bitumen luting bore the impressions of the vegetal material used for the wadding, composed of grass or leaves.
18Species identification analysis carried out on 11 samples reveals a variety of materials including teak (Tectona grandis), palm (Palmae: species unspecified), Terminalia Sp., Ziziphus mauritania (jujube) and Leguminoseae Cisalpinaceae for the planking, with the cordage material resembling coconut fibre (Cocos nucifera) (Belfioretti, Vosmer 2010, p. 111–112; Capretti et al. 2010).
19Fourteen timbers have been radiocarbon dated by Beta Analytic Radiocarbon Dating Laboratory, Miami, Florida, showing a period between the 10th and 15th centuries AD (Belfioretti, Vosmer 2010, p. 114). Interestingly, the planks without rebates appear to be the earliest of the dataset and do not occur after the first quarter of the 13th century (Vosmer 2017, p. 199).
20Traditional boatbuilding techniques have persisted in the Indian Ocean and ethnographic studies have provided information on more modern sewn-plank boats of the region, e.g. Yemen, Somalia, East Africa, India and Oman. Recent sewn watercraft allow the identification of the Al Baleed timbers as ships’ planks and offer insight into the interpretation of their features.
21The first noticeable characteristic is the continuous sewing technique, as indicated by the holes spaced along the edges of the planking and by two planks displaying part of the sewing. The presence of fibre cordage, most likely coir, finds confirmation in historical sources, which are unanimous in describing it as the material used to hold planks together. However, despite mentioning the presence of sewn vessels in the region, textual sources provide very little detail regarding the fastening technique. The closest reference to continuous sewing is reported by the missionary Friar John of Montecorvino in the 14th century, who remarked that the ships of the Arabian Sea were “sewn like clothes” (Yule 1914, p. 66).
22Analysis of timber features suggests two types of sewing patterns. Planks with rebates indicate the most commonly recorded in the western Indian Ocean, a technique consisting of wadding under the stitching on the inside of the hull, and ropes recessed in rebates on the other side. This sewing method is ubiquitous in the western Indian Ocean and recorded in sewn boats from Oman (Pâris 1843, pl. 8; Vosmer 1997, p. 232–234), Yemen (Bowen 1952, p. 205; Prados 1996, p. 102), Somalia (Chittick 1980), East Africa (Hornell 1941, p. 60; Prins 1982, p. 94–98) and India (Varadarajan 1998, p. 58–60; Shaikh et al. 2012, p. 152–153). Since rebates are generally found outboard on recently built sewn vessels, with the purpose of protecting the sewing cordage against chafe (Prins 1986, p. 89; Severin 1985, p. 283), the surface with rebates on the timbers from Al Baleed would likely indicate the outside of the hull. Unfortunately, the planks are all straight and show no curvature that might help to determine the outer surface. This is due to their short length, rarely exceeding 1 m, and, perhaps, because the builders of the site of Al Baleed intentionally chose flat and straight timbers more suitable for being recycled as ceiling planks or shelves in the buildings of the site. A few planks of the dataset display the small tunnels created by shipworms (Teredo navalis) on the same surface displaying the rebates, further strengthening the hypothesis that these were carved outboard.
23Planks without rebates point to a different sewing method, and although the relevant timbers have no preserved portions of stitching, the lack of rebates suggests the presence of the wadding above the seam of the planking on both sides of the hull, which is known as a double-wadding pattern (Vosmer 2017, p. 200) or double web (Kentley 2003, p. 163). This pattern was observed on the 9th-century Belitung wreck, discovered in Indonesia and interpreted as an Arab/Indian/Persian vessel (Flecker 2000). The fact that planks without rebates are earlier than those with rebates might hint at a development from the double-wadding to the single-wadding technique (Vosmer 2017, p. 200).
24Another distinctive feature of the Al Baleed timbers is the presence of dowels, which underlines their primary role in sewn-plank construction in the Indian Ocean. Usually spaced evenly apart, they served the purpose of aligning and locking the planks into place during the assembling of the hull. Dowels were also employed to reduce longitudinal movement of the planks caused by hogging of the hull, which could result in water leakage (Coates 1985, p. 18).
25There are no frames in the Al Baleed collection of timbers, however, sets of holes drilled at the centre of planks point to their lashings and provide information regarding their size (sided dimension) and spacing. Overall, frames have a variety of thicknesses ranging from 36-210 mm and are spaced between 55 and 373 mm apart, which points to light framing that is widely spaced, reveals the flexible nature of a sewn vessel, and highlights the importance of other elements, such as the sewing, dowels and beams, in providing structural integrity to the hull. By describing the ships he observed in Cananor (Kannur), southern India, in the 16th century, Correa reports the only reference to frames in historical sources, stating these vessels had only a few ribs sewn to the hull (Stanley 1869, p. 240).
26Traces of a bituminous amalgam, and perhaps other substances such as resin, on the edge and surface of the timbers indicate the practice of luting and coating the hulls of vessels. Ancient boatbuilders smeared bitumen on the edge of the planks to seal the seams and waterproof the hull. Correa described this practice in the 16th century in the construction of Indian vessels (Stanley 1869, p. 241), and it is still employed today using resin by builders of the sewn-plank boats of Goa (Shaikh et al. 2012, p. 152).
27Bitumen on both the inner and outer surfaces of the timbers suggests that the vessels were coated to protect them against marine pest organisms, such as shipworms (Teredo navalis) and barnacles, as well as to improve the watertightness of the hull.
28As remarked by Belfioretti and Vosmer (2010, p. 116), a comparison with archaeological and ethnographic data provides an opportunity to speculate on the size of the ships from which the timbers had been removed. Several planks from Al Baleed exceed the thickness of 40 mm recorded in the Belitung shipwreck, which had an estimated length of 20-22 m (Flecker 2000, p. 205, 209). Thinner planks (20-30 mm) could have been employed in 8-10 m sewn boats, similar to Omani kambārī (Vosmer 1997), Somali beden (Chittick 1980) or the sewn sanbuq of Yemen (Prados 1996; Bowen 1952). The evidence from Al Baleed may indicate a variety of vessel sizes ranging from large cargo ships, measuring 20 to 30 m, to small coastal fishing and lightering vessels, ranging from 6 to 10 m in length.
29In light of still-limited information yielded by other archaeological evidence, the study of the Al Baleed timbers reveals interesting insights into Indian Ocean maritime technology in the medieval Islamic period. On the one hand, the timbers share similarities with archaeological evidence and 19th-20th century of sewn boats ricorded in the region, while, on the other, they reveal a variety of forms and techniques.
30Although the timbers themselves cannot confirm what the vessels looked like or give any indication of either their cargo or their route, their features provide a wealth of information about different sewn boats and boatbuilding technologies over a considerable period, allowing speculation about evolutionary trends in construction techniques and technology.
31The advantage of a collection of planks from different vessels covering a period of more than 500 years, such as that from Al Baleed, is that they offer a chance to identify building materials. Future wood identification analyses may furnish hints about the origin of the vessels, possible connections between the materials used and construction techniques, and boat size or function. Variations in wood species used for boat construction over time can offer exciting insights regarding material trade, furthering deepening understanding of fundamental maritime connections in the Indian Ocean during this period.
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I am thankful to H.E. Abdul-Aziz bin Mohammed Al Rowas, Adviser to His Majesty the Sultan for Cultural Affairs for providing the opportunity to study the timbers from Al Baleed, and to all his staff, particularly Dr Said al-Salmi and Hassan al-Jaberi for their support in Muscat, and to Ghanem Al Shanfari and Ali al Kathiri for their assistance at the Museum of Frankincense Land in Salalah, where the timbers are stored. I would like to thank IASA (International Association for the Study of Arabia, former British Foundation for the Study of Arabia) and the Barakat Trust for providing financial support to my research with the Small Research Grant and the ṢADAQA JĀRIYA grant. A special thanks is due to Alexia Pavan, director of the excavation in Al Baleed, for her help and generosity in sharing the information regarding the context of the timbers. Finally, I am extremely grateful to Tom Vosmer and Eric Staples for their invaluable comments and advice about the maritime technologies, traditions and history of the Indian Ocean.
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