Updates on what I’m working on, although without significant rules updates:
I managed to get some good research in yesterday. It’s amazing what you can learn when you remember your college gives alumni access to the research library. I have a very rough draft of a system where I can input the dimensions of a ship and the number of crew, and get outputs regarding maximum sail size, speed, and “cargo” mass available (cargo in quotes because it includes passengers, artillery, etc). I don’t want to release the current form because it’s very much based on interpolating polynomials and has some extremely fugly maths in it.
I also have a rough draft of how sailing will function. Maximum sail sizes will be based on the number of sailors, again using historical numbers and calculating averages. Basically, a ship with square sails and brails only (such as Peloponessian War Greek ships) can have up to 12m^3 of sails per sailor, while ships with more developed systems of stays can have up to 16m^3 of sails per sailor. Most ships will carry far less, since having sailors sick or dead would reduce the crew available and make those large sails unmanageable. The longer a ship will be away from port, the smaller the ratio of sail size to maximum sail size should be. Also, it is possible to “over-canvas” a hull, where it carries more sail than it should for its size. This makes the ship less controllable, and the excessive heeling and broaching will actually reduce speed. I’m trying to include this in the calculations by looking at when a ship’s (calculated) speed under sails exceeds its theoretical hull speed; this is when a ship will start running over its own bow wave, and for an unpowered ship, this is when that sort of wallowing can be expected.
With regards to “cargo”, my current assumptions are:
- Maximum available tonnage is 60% of displacement tonnage. This is based on a 17th century estimate that tons burthen was 60% of tons displacement.
- Crew averages 150 pounds per member. This does not include equipment for marines. Crew mass subtracts from available cargo space.
- Rations (food and water) averages 1 stone per crew per day.
Equipment will have to be manually subtracted, at approximately .05 tons per stone (or 20 stone per ton).
To show some of the results, the Trireme above has 180 rowers, 16 officers and sailors, and 20 marines. Based on her dimensions and the number of rowers, her speed should be around 6.3 knots sustained and 9.5 knots maximum. (For comparison, Olympias achieved around 6.0 knots sustained and 8.9 knots maximum, but they had difficulties getting maximum power from their rowers because modern athletes are generally too large for the rowers’ space in a trireme). While she could carry 120 m^3 of sail, she actually carries a 95 m^3 mainsail (as well as a foresail that is primarily used for steering control and is not counted for speed) and is capable of 9.2 knots in perfect condition (note that this will probably be dropped by a rule limiting what wind conditions galleys can sail in - the rules don’t yet take into account sea state). The trireme can carry 48 tons of cargo, but 16.2 tons of that is the crew, and a single day’s rations is another 10.8 tons. Add in weapons for the marines and sailors, and there’s not a lot of spare mass left, particularly since the cargo is an absolute maximum and there would be some tools on board for the carpenter to effect repairs.
For comparison, Columbus’ ship Nina goes to the opposite extreme, carrying only 24 sailors on a 100 ton hull. She would have 150 shp, and is capable of carrying 320 m^3 of sail. The actual Nina only carried around 180 m^3 of sail, and this still left her over-canvassed according to my system. The Nina can carry 60.18 tons of cargo. Subtracting crew allows 58.38 tons, but adding 40 days’ rations reduces it to 10.38 tons; the most she can carry is 48 days’ rations with 0.78 tons of cargo space remaining. This puts the five week journey across the Atlantic within her range with some extra factor for delays, but there’s not much excess, and very little cargo space for such a long journey. Santa Maria, on the other hand, could carry 49 days’ rations and still have 33.34 tons of cargo space left over. Nina’s top sailing speed is 7.2 knots; Santa Maria could only accomplish 6.3 knots, while the swift Pinta was capable of 8.5. While this doesn’t perfectly accord with the Spanish reproductions’ speeds (6 knots for Santa Maria and 7 each for Nina and Pinta), it does accord with Columbus’ writings that the Pinta was swifter than the Nina.
Anyway, this is a long post and there’s a lot of broad detail in it. I’m not yet entirely happy with the sailing speeds for Greco-Roman polyremes, but I’m still reading on that. As mentioned above, I need to play with limiting their ability to sail in high winds, which will have the effect of limiting their practical speed under sail.
I am quite happy with sailing speeds for rounder ships, since I’ve run them on vessels varying from a 14th-century cog through the 15th-century Columbus vessels and up to a 18th-century 104-gun ship-of-the-line, and I haven’t broken anything so far (except for missing a parentheses early on and having the 104-gun ship sailing at 43 knots…)