Shipwrecks harbor evidence of ancient sophistication

PHILADELPHIA — Surprising insights about ancient shipbuilding have floated to the surface from the submerged remnants of two major harbors, one on Israel’s coast and the other bordering Istanbul, Turkey. Researchers described their finds January 9 at the annual meeting of the Archaeological Institute of America.

Analyses of salvaged crafts indicate that shipbuilders started making sophisticated frames for their vessels by about 1,500 years ago, 500 years earlier than had been suspected, reported Yaakov Kahanov of the University of Haifa in Israel. By a few hundred years later, craft constructors had steadily improved hull designs for a diverse collection of ships, says Cemal Pulak of Texas A&M University in College Station.

Frames provided greater structural stability for ships than an earlier hull-building technique that had relied on joining planks with adhesives and fasteners to form a shell. Such vessels date to as early as approximately 2,000 years ago.

Kahanov and his colleagues have documented the existence of frame-based hulls on five shipwrecks, all from the fifth to ninth centuries. Water-logged wood from the vessels was recovered at the now-submerged Mediterranean harbor off the island of Dor in Tantura Lagoon, south of Haifa. Researchers then transported the finds to the University of Haifa for study.

The late engineer Richard Steffy, who founded the field of ancient ship reconstruction about 20 years ago, had suspected that shipbuilders did not build frames for hulls until roughly 1,000 years ago.

“Several fully excavated shipwrecks at Tantura date the transition from shell-based to frame-based construction to the mid-first millennium, over half a millennium earlier than previously thought,” says Shelley Wachsmann of Texas A&M University, who was not involved in the research.

Analyses show that the vessels’ builders first fashioned wooden frames. They then nailed planks to the sides and used a type of caulk to fill in seams. Flat pieces of timber were used for ships’ floors. Hulls contained spots for attaching sail-bearing masts, Kahanov said.

Other ship-construction discoveries have come from excavations off Istanbul’s coast at what was Constantinople’s Theodosian harbor. Pulak leads a team of 50 archaeologists, architects and conservators — as well as 500 workers — who have been working at the partially submerged harbor since 2005.

Built by the Byzantine empire in the fourth century, the harbor now lies offshore of the Sea of Marmara. By the 11th century, what had been a major trade center for hundreds of years was rendered mostly unusable by the buildup of river silt.

In the last four years, Pulak’s team has recovered 32 shipwrecks ranging in age from the seventh to 11th centuries. These vessels represent a variety of types, including Byzantine naval galleys, cargo-carrying ships and small fishing and all-purpose craft.

All of the Istanbul ships were built from frames, Pulak said. Frame construction became more sophisticated over time as builders developed various design innovations. Such experimentation was focused on commercial ships, he noted. Warships were built by established methods considered most secure at the time.

Four long, narrow vessels discovered in the harbor contain holes in their sides for oars. Encircling these openings are remains of leather sleeves, known from historical accounts to have kept water from splashing into the ships. One boat retains the wooden benches on which rowers sat. Another contains boards once used as oars.

“For the first time, we’ll be able to work out the ergonomics of rowing on these boats,” Pulak said.