Tessarakonteres

Tessarakonteres (Greek: τεσσαρακοντήρης, "forty-rowed"), or simply "forty", was a very large catamaran galley reportedly built in the Hellenistic period by Ptolemy IV Philopator of Egypt.

It was described by a number of ancient sources, including a lost work by Callixenus of Rhodes and surviving texts by Athenaeus and Plutarch.

And besides all these there was another large body of men under the decks, and a vast quantity of provisions and supplies.Plutarch, writing in the late 1st century AD, also mentioned this immense vessel in his Life of Demetrius, part of his Parallel Lives series, disagreeing or misquoting slightly on the height to top of stern, which he reports as forty-eight cubits:[3] Ptolemy Philopator built [a ship] of forty banks of oars, which had a length of two hundred and eighty cubits, and a height, to the top of her stern, of forty-eight; she was manned by four hundred sailors, who did no rowing, and by four thousand rowers, and besides these she had room, on her gangways and decks, for nearly three thousand men-at‑arms.

But this ship was merely for show; and since she differed little from a stationary edifice on land, being meant for exhibition and not for use, she was moved only with difficulty and danger.Note that the translation of "forty banks" is overliteral; see below.

He points to the practical limit of eight rowers to an oar, giving a maximum size class of "twenty-four", as well as to the need for a vastly larger deck than one ship could provide in order to accommodate the reported numbers of marines.

Combined with Callixenus's description of the ship having two heads and two sterns, Casson suggests that the "forty" must have been a catamaran made up of two three-ranked "twenties" joined by a deck.

And in the trench he built props of solid stone five cubits deep, and across them he laid beams crosswise, running the whole width of the trench, at four cubits' distance from one another; and then making a channel from the sea he filled all the space which he had excavated with water, out of which he easily brought the ship by the aid of whatever men happened to be at hand; then closing the entrance which had been originally made, he drained the water off again by means of engines (organois); and when this had been done the vessel rested securely on the before-mentioned cross-beams.