Carpow Logboat
The excavation, recovery and conservation of a 3,000 year old logboat.
Discovery
In August 2006 the Trust excavated and recovered a unique Late Bronze Age logboat from the Tay Estuary. The project began when the boat was first reported back in 2001, though developed to include conservation of the vessel prior to public display and extensive study leading to two major publications.
Logboats are simple water-craft carved from a single tree trunk, and are the first known boats in existence. The earliest known example is from the Netherlands Denmark, and dates to around 7000 BC. They have continued to be used in many parts of the world since then however, and continue to be used in some areas today.
While records of over 150 logboats exist from Scotland, these mainly dating from around 500BC to AD1000, and of these only around 40 survive. Of the records of 7 logboats from the Tay estuary, only one survives today, found by fishermen near Errol, which on display at the McManus Museum and Art Galleries in Dundee. The Carpow logboat was first reported in 2001, partially buried in the inter-tidal sands and gravels of Carpow Bank, at the head of the Tay Estuary.
Exploration
A radiocarbon date quickly verified that the boat was 3,000 years old, dating to 1130-970 BC, and small-scale excavation in 2002 and 2003 established the full length of the boat (around 9m), and confirmed that while the bow of the boat had been eroded by tidal action, the buried hull and stern remained in excellent condition.
Excavation in the inter-tidal zone was complicated by the Tay’s mean annual discharge of 160 cubic metres of water per second. The site could only be accessed over the summer for around 3 to 4 hours each day, and the site was reburied in tidal mud and sand at each high tide. The exploratory excavations identified Carpow as one of the best preserved prehistoric logboats from Britain, the second oldest boat from Scotland, and an important addition to what was known about Late Bronze Age life in the Tay Estuary area.
Monitoring, however, revealed that the exposed bow of the boat was rapidly eroding in the high-energy tidal environment. As a result, it was decided to excavate and recover the vessel for study and conservation, and to provide the catalyst for the first review of our understanding of Late Bronze Age Tayside for almost 40 years.
Excavation and recovery
By 2006 both the plan and funding were in place and the excavation and recovery was carried out over seven days in July and August 2006 by the Trust, with support from archaeological contractors CFA Archaeology Ltd, local marine engineering firm Moorings and Marine Services, and both the National Museums of Scotland and Perth Museum and Art Gallery.
Carefully excavated to avoid damage, the stern of the boat was discovered almost 1m below the ground surface, and water pumps were employed to remove the collecting water from the trench. Once fully excavated from the sand and gravel, the boat was rigged to float using air-filled barrels, secured within the vessel, and as the tide came in, the boat slowly started to lift, moving for the first time in 3,000 years.
Manoeuvred to the riverbank for safe keeping, the following day the logboat was once again floated and towed 1.5km downstream to Newburgh quay, where it was carefully inserted into a custom-built lifting frame and lifted by crane onto a flatbed lorry to be transported to the National Museums of Scotland.
Conservation and study
The oak boat had only survived because it has remained water-logged for all those years, and once out of the water, the vessel was at risk of disintegrating as a result of many complicated physical and chemical processes. The first stage of the conservation process involved cleaning the boat while keeping it wet to prevent it from drying out.
At this time a detailed study of the boat was carried out, identifying and recording fixtures and fittings, damage, wear, and so on. The transom, for example retained tool-marks from the socketted axes used to carve it, and moss caulking (a material to make a boat water-tight) even survived where it had been inserted by the Late Bronze Age builders.
The vessel was subsequently soaked in tanks of PEG (polyethylene glycol) solution: a process which replaces water in the cells of the wood with a more stable chemical compound, allowing the boat to be displayed in a museum atmosphere without the need to be kept wet. This is to be followed by a final phase of freeze-drying, in 2010, to remove any remaining water. Once this conservation process is complete, the logboat will return to Perthshire, where it will go on display in Perth Museum and Art Gallery in 2011.
The project has now been published both as a Society of Antiquaries monograph and a popular booklet, which use extensive illustrations to convey the story of the discovery, excavation, conservation, and how this remarkable find has contributed to our understanding of Bronze Age Tayside.