Oarsmen learn the secrets of ancient Greek war machine : Almost unbeatable in battle, the triremes still had flaws. David Keys reports

A GROUP of British and American historians, naval architects and rowing enthusiasts have discovered how the ancient Greeks' greatest war machine worked.

With a 37m-long (121ft) replica of a 2,500-year-old Greek trireme - the Olympias, currently on a visit to London - the researchers have revealed just how effective, yet limited the ancient world's most famous ships were.

Sea trials by the Trireme Trust suggested that the vessels were highly manoeuvrable and could achieve top speeds of 10 knots (11.5mph). For maximum power the 170 oarsmen would have had to row at about 47 strokes a minute. Both sails and oars would have been used for speeds below seven knots.

But major limitations have also been exposed. The design stage revealed that triremes were very delicate and risked breaking in two in waves more than 1m high and 30- 35m long.

The trials showed a maximum range of about 200 miles. The main limiting factor was water: a 200- mile journey would have required at least 800 gallons weighing almost four tons. Another restriction was the immobility of the 170 oarsmen. As well as providing power, they were also the ship's ballast. If they moved they would upset the vessel's equilibrium.

The triremes would have been strictly limited in how long they could last in battle. Dog fights would have had to be over in 10 minutes because that was the period a crew could have rowed at or near maximum strength.

The design research and sea trials suggest that ancient Greek triremes would have cruised at about 51 2 knots, with a top speed of about 10 knots. Full speed would have produced only 47hp - marginally less than a Mini.

But the crew and researchers are still puzzled by how the rowing masters kept their oarsmen synchronised. The Olympias uses electronic loudspeakers, but the ancient Greeks could not.

The trials ruled out drums, singing and high-pitched reeded pipes. Communal humming was most effective - it even increased speed by more than 10 per cent.

'Humming worked extremely well,' said one of the Oympias' two rowing masters, Boris Rankov, a classical scholar and former Oxford University Boat Race oarsman. However, there is no literary record of the ancient Greeks humming.

An account of much of the sea- trial work - The Trireme Project - has just been produced by the archaeological publishers Oxbow Books, of Oxford. The Trireme Trust plans further trials and computer simulations of battles. This should enable classical historians to improve substantially their understanding of the many famous naval battles described in ancient texts.

Visitors will be able to see the Olympias moored on the Thames on Sunday 20 June, at a Greek cultural festival at Gabriels Wharf, London SE1 (by south end of Waterloo Bridge), 2pm-7pm, admission free.

(Photograph omitted)