The original program Logic was done in 2001 by Rick Robinson as a MS-DOS program (ZIP Archive with executable + source). In 2024, I decided to convert it to an in-browser HTML5/Javascript format with ChatGPT, as well as make one or two improvements (estimating the number of rowers given galley length). In this form, it works a lot better than the original MS-DOS program; as well as being accessible "on the go".

Olympias (Ολυμπιάς), a reconstruction of a Greek Trimeme had the following dimensions:

• LOA: 121.063 ft / 36.9m
• Beam: 18.04 ft / 5.5m
• Draught: 4.1 feet / 1.25m
• Displacement: 68 long tons / 70 tonnes
• Propulsion: 170 oarsmen in three banks (62 top, 54 middle and 54 lower)

to give you an idea of what's "plausible" for a galley.

Length at Waterline (ft)
Beam at Waterline (ft)
Depth (ft)
L/D Ratio of Hull
Block Coefficient Ratio (Acceptable Range: 0.2 to 0.8)

NOTES ON BLOCK COEFFICIENT

• 0.40 = Very fine, "hollow" hull.
• 0.52 to 0.55 = Typical Galley Hulls.
• 0.65 = Full or Shallow-Draft Hull.

NOTES ON AVERAGE # OF ROWERS PER BENCH

• A quinquereme might have two banks, with two men to an oar on the lower bank and three men to an oar on the upper bank. For this quinquereme you would enter the average of both banks or 2.5.
• For a big Renaissance galley rowing five men to an oar in a single bank, enter 5.
• For a classical trireme with three banks, one man to an oar on each bank, enter 1.
• For a medieval Venetian-type galley, with all rowers on one bank, side by side on a bench but each pulling his own oar, enter 3. (In practice, this arrangement, alla zenzile, was probably slightly more efficient than three men pulling one big sweep, al scalaccio; possibly it should be entered as 2 men to a bench even though there are three.)

Desired Speed (knots)

The speed formula(s) used in calculations are based off W.L. Rodgers Greek and Roman Naval Warfare, page 31.