[HR] Naval Rules

General ACKS Forums House Rules
6

I wasn’t a D@W backer, so I don’t have the hex ranges for that. All of the missile ranges were taken from the ACKS core book, by taking feet of range and dividing by 30 to get hexes, with the onager and ballista tweaked slightly to give them S/M/L instead of just a generic range.

As far as ship widths go, all of them are one hex wide ignoring the oars (even the deceres’ hull is no more than 8.5 meters wide, which is 28 feet). After watching some video of Olympias, I’m OK with all of the ships being one hex - I was adding the length of the oars to the width of the ship, but a lot of that length will be used vertically to reach the water, so the only real potential from interference should come from multiple deceres next to each other, which is just enough of a fringe case to not worry about. For turns, moving on the center hex looks like it will work, with the 4 hex ships turning on their second hex (so the aft swings further than the bow).

7

OK, tweak to firing arcs and weapon mounts:

Firing arcs are described by a pair of numbers. These numbers are facings that the weapon can fire into, starting with 1 being the hex face directly in front of the ship, progressing clockwise to 6 being the front left hex face. All arcs are described clockwise, so an arc of 5-1 means that the weapon can fire into any hex bounded by lines extending from hex face 5 (rear left) to hex face 1 (directly in front), including those lines.

Arcs:
Forward (F) - 6-2
Forward Port (FP) - 6-1
Forward Starboard (FS) - 1-2
Port Broadside (PB) - 5-6
Starboard Broadside (SB) - 2-3
Aft (A) - 3-5
Aft Port (AP) - 4-5
Aft Starboard (AS) - 3-4
Fore Tower (FT) - 4-2
Aft Tower (AT) - 2-6

Mounts: Any ship can mount 1 F or 1 FP and 1 FS, 1 A or 1 AP and 1 AS. Each heavy warship can mount 1 ballista each FT and AT. Any ship may mount any number of weapons broadside.

Ramming: A ram attack is carried out as an attack by a 0-level fighter, modified by the captain’s INT modifier. An attack from ahead or behind uses the target’s AC. An attack from the side subtracts the target’s length in hexes from AC (examples: A trireme is AC 5, 3 hexes long. From the side, it is treated as AC 2 for ramming attacks only. An armored deceres is AC 6, 5 hexes long. From the side, it is treated as AC 1 for ramming attacks only). A successful ram, in addition to the standard ACKS damage, also inflicts a Hull Holed critical on the target.

Onager update: due to the lack of a stable platform on a ship at sea, and because the onager fires indirectly (as opposed to the direct-firing ballista), all onager attacks have a -1 penalty to hit.

General siege weapon update: Siege weapons can only be fired at ships, not at individual targets. The critical hit tables will account for striking crew.

Critical Hit Tables:
Ballista:
2 - Left Rudder Destroyed
3 - Captain Hit
4 - Weapon Destroyed
5 - Oars Fouled
6 - Oars Destroyed
7 - No Additional Effect
8 - Marines Hit
9 - Marines Hit
10 - Rowers Killed
11 - Navigator Hit
12 - Right Rudder Destroyed

Onager:
2 - Left Rudder Destroyed
3 - Captain Hit
4 - Weapon Destroyed
5 - Oars Fouled
6 - Marines Hit
7 - Oars Destroyed
8 - Hull Holed
9 - Hull Holed
10 - Rowers Killed
11 - Navigator Hit
12 - Right Rudder Destroyed

Critical Hit Effects:
Captain Hit - the captain suffers splinter damage
Navigator Hit - the navigator suffers splinter damage
Marines Hit - 1d4 marines suffer splinter damage. If there are multiple types of marines on board, 50% of the time the attacker chooses which type of marine, 50% of the time the target chooses which type of marine
Weapon Destroyed - 1 weapon is destroyed. 50% of the time the attacker chooses the specific weapon, 50% of the time the target chooses the specific weapon
Hull Holed - Target ship suffers a -1 turn rate (a turn rate of 1/3 becomes 1/4, etc)
Oars Fouled - Target ship suffers a -1 to speed for 1d3 rounds. Before rolling, the target can choose to reduce speed to 0 for 1 round instead
Oars Destroyed - 1d3 columns of oars are destroyed. If spare oars are not available, the ship is considered to have 1d3 fewer columns of rowers until spare oars become available. A bireme needs 2 spare oars per column, all other ships need 3 spare oars per column.
Rowers Killed - 1d6 columns of rowers are killed. Because oars are loosely tied to the ship to prevent rowers from dropping them overboard, they are not lost.

Columns of Oars: This is the total number of columns on board the ship. Half of the columns are on each side of the ship.
Bireme - 72
Trireme - 60
Quadrireme - 72
Quinquereme - 90
Hexareme - 110
Septireme - 128
Octeres - 148
Enneres - 168
Deceres - 190

If the active columns drop below 3/4, Sustained speed is reduced by 1 and Burst speed is reduced by 2. If the active columns drop below 1/2, Sustained speed is reduced by an additional 1 (2 total) and Burst speed is reduced by an additional 2 (4 total).

Note: I am adding these rules to my master document, so once the revisions are mostly done, a single post can be made with the updated rules.

8

Because I really shouldn’t assume anything - the critical hit charts are rolled on 2d6, and a critical is scored when a natural 20 is rolled to hit.

9

Just because I’d mentioned it, I thought I’d see how they compare:

Ballista – short range 5, medium range 10, long range 20
Onager – minimum range 5, short range 10, medium range 20, long range 40

At 30’ hexes (Domains At War Platoon Scale, platoons are 30 men or 15 mounted troops) ranges are:

D@W Ballista:

Light: Min 1, Max 16 hexes
Light, Repeating: Min 1 hex, max 16 hexes
Medium: 1-16 hexes
Heavy: 1-20 hexes

Catapults:

Light: min 10, max 20
Medium: min 12, max 28
Heavy: min 12, max 28

All Trebuchet: 12-32 hexes

Works out pretty similar!

There’s no range penalties in D@W; they also do a set amount of damage, but they’re stationary actors firing at stationary targets (fortifications) mostly, so artillery in that sense is more of a physics problem than an exchange of missiles.

Is splinter damage as per the damage dealt by the weapon?

10

For the critical hits, yes. It was an abstraction of the “damage to all creatures in a 5’ line” for the ballista and “damage to all creatures in a 5’ area” for the onager, but I didn’t define it thoroughly.

I’m also glad to see that the ranges mostly worked out. I wanted to have S/M/L so that they could be treated similarly to individual ranged weapons. The onager probably is a little bit long-ranged, but I haven’t had a chance to see how the combination of long range and poor accuracy (-6 at 21-40 hexes) actually works out.

New rule:
Initiative: Ships move on their captain’s initiative, with a +1 bonus for each time the captain has taken the Seafaring proficiency. Marines and weapon crews act on a separate initiative roll, with a bonus if the leader of the marines has ranks in Martial Strategy. (Note: if a campaign will focus on both sea and land battles, a Naval Strategy proficiency that functions identically to Martial Strategy but with MS specific to land and NS specific to sea may be prudent)

Clarification on firing arcs: broadside weapons may trace their line of fire from any hex that the ship occupies. F, FP, FS, and FT weapons trace line of fire from the front hex, while A, AP, AS, and AT weapons trace line of fire from the rear hex.

Topic for discussion: I am considering having a rammed ship forfeit its next movement and take a penalty to shots for one round to reflect the ship being shaken up. This would tie in to fleet rules, where initiative determines who moves first, with each “class” of ship moving before heavier ships, letting the light ships try to disrupt heavier ships by ramming.

11

Gotcha.

I’m gonna fly off into some D@W stuff here, so please don’t think I’m giving you the business, though I may be “selling” D@W a bit here. I’m just showing what ACKS “will have” in a couple weeks or so that might be conceptually usable:

So, officers in D@W have a few characteristics that might aid here:

Leadership Ability: Equal to your # of henchmen you can hire - 4+ChaMod+Proficiency if any.

Zone of Control: 1/2 the Leadership Ability, representing the radius in hexes a commander may activate units without penalty (give them orders)

Strategic Ability: Highest of Int or Wis bonus, minus worst of Int or Wis penalty if any, then Military Strategy added to that. That determines your initiative bonus in mass combat for the commander’s units.

Morale Modifier: CHA plus any class powers (battlefield prowess, etc)

So, you gain a number of activation points equal to your Leadership Ability that you spend to activate your units. (it also determines how many divisions you can have in the army you command).

I could see splitting the marines and weapon crews into separate “units”, that can be activated in the particular order the captain wishes, with the ship perhaps counting as it’s own “unit” for movement.

Furthermore, each ship can be it’s own “division”, thus limiting any given captain’s fleet size to what he or she is able to handle.

Zone of Control could be reworked to reflect whatever the historical signalling method (and effective range thereof) was between ships of the time, perhaps with bonuses from the Signalling proficiency, or overload the Naval Strategy proficiency.

Separating Naval from Military, proficiency wise, is a really good idea; they are two different beasts. Make the PC that wants to be a terror on land and sea work for it.

Regarding the rammed ship effects: There’s the concept of “shock” in D@W, if a unit takes enough damage or magical damage; a morale roll determines effects (rout, flee, recoil, stand firm). That might be something worth modifying, since you’re already using a morale roll in several different places.

Pursuant to that, a unit can become “disordered”, requiring another Activation Point to use. If a successful ramming would cause each unit on board to have to roll for “shock”, and those units fail the roll, the captain perhaps wouldn’t have enough AP in that round to activate everyone on ship, and may have to forgo movement or marines firing or weapons firing depending on who failed, thus reflecting the on-deck disorder of a rammed ship.

Or do it for the whole ship.

Perhaps a critical hit (a particularly good ramming) (if you know what I mean) might also force the roll for the ramming ship in addition to double damage or what-have-you.

Completely random thought: is it worth the complexity to have a “warm up” to gaining speed, espc. from a stationary start? Perhaps using burst rowing to reduce the effect?

12

Quick reply to the non-D@W question: “Completely random thought: is it worth the complexity to have a “warm up” to gaining speed, espc. from a stationary start? Perhaps using burst rowing to reduce the effect?”

Not really. During the Olympias trials, they were able to get to their average sustained speed in three to four strokes, which is quick enough that I don’t see it being beneficial to have an acceleration limit.

For the D@W ideas, I wouldn’t be surprised if I end up doing a tweaked set of rules incorporating D@W ideas, so that there will be both an “ACKS core” naval rule and an “ACKS+D@W” naval rule. Unless, of course, Alex plans to have naval rules in a supplement, at which point I’ll just be modifying the heck out of them to fit my own feeling of how things should be done.

13

Huh. That’s interesting. I guess the number of oars; etc. Someone on the internet probably has the physics on it.

D@W: Alternatively, he may just publish yours. :slight_smile:

14

The Dark, would you mind dropping me an email at alex@autarch.co to discuss?

I do not currently have plans for naval rules but they are in hot demand. What I have read so far has been impressive and I’d like to further the discussion.

15

Alex - I’ve sent you an email from my gmail account.

Additional polyreme variations:
The standard polyremes described above are cataphract, multi-level ships. This means they have a full deck and have rowers on 2 (bireme) or 3 (all others) levels. However, this is not how all polyremes were rowed.

Aphract - this variation does not have a full deck, but narrow partial decks. This type of polyreme is somewhat lighter and thus faster and more maneuverable, but more fragile and with less room for artillery and soldiers.
Aphract modifiers: -10% shp (round to nearest 5), 1/2 marines, 1/2 artillery (rounded up), +1 turn (turn 1 round sooner), +1 crew morale when Burst rowing.

Single-level - this variation uses as many rowers as possible on the fewest number of oars. Archaeological evidence shows that up to 8 rowers could be placed on a single oar. This type of polyreme was wider than the multi-level polyreme. This gave it more deck space for marines and requires fewer trained rowers, but it was less maneuverable due to the wider hull. Technically, enneres and deceres with this modification are rowed on two levels (4 and 5 rowers for the enneres, 5 and 5 for the deceres), but the end result is the same.
Single-level modifiers: -1 turn (turns take 1 more round to complete), +50% marines, -1gp monthly maintenance per 2 rowers.

16

Time for a mildly fantastic addition to the rules:

Transports:
Old warships can be converted to animal transports. As these ships are intended to be protected by warships, they carry neither weapons nor marines. However, they can carry one horse (or other horse-sized animal) for each marine they could normally carry. While the horses are larger than the marines, they are carried in slings without room to move around, allowing them to be carried closer to each other.

Flying transport:
Some nations that have both navies and soldiers who ride flying creatures, such as pegasi, griffons, or hippogriffs, have had the idea to combine the two for use as scouts and light combatants. Because these animals need room to move around, take off, and land, they cannot be stabled as close together as animals that are solely being transported. Thus, for each three marines removed from a ship, one flying animal and its rider may be added.

(non-rule author’s note: The potential number of mount-plus-rider pairs ranges from 2 for an aphract bireme to 45 for a single-level deceres. However, a wise captain will ensure he keeps enough marines on board to man the artillery. The ships that can fully man their artillery and fly the most creatures are the single-level octeres, enneres, or deceres, all of which can fly 16 pairs while still having a full group of artillerists)

17

Hot damn. Aircraft carriers.

I’ve got this dream of the biggest barge ever built launching rocs.

18

Ptolemy IV Philopator’s tesserakonteres (“forty”) might do it (for the giant roc, at least - the smaller ones could be used from existing ships). It was a catamaran hull (two “twenties” held together by a deck) that was 420 feet long, 57 feet wide, and on its trial run had over 4,000 rowers, 400 sailors, and 2,850 marines.

As a side note, I haven’t done up any ships larger than a deceres (“ten”) for a couple reasons. First, there’s fairly little information on them. Ptolemy’s beast is the only one I’m aware of with known dimensions. Also, there seems to be no evidence for any larger ships taking part in naval battles (although some may have participated in sieges).

19

That’s impressive. That’s only a little smaller than the first US carrier (converted from a different sort of ship), and about half the length of the first true carriers. For that matter, the small rocs have about the same wingspan as the late biplanes.

If I were to want to siege a coastal city, if I could weaken their navy first I’d certainly want to have engines on either side of the walls I’m trying to down. Just a good enough screen of smaller ships to protect what is essentially a mobile catapult platform.

20

Going back to my comment about the tesserakonteres being the only giant polyreme with known dimensions, if anyone has sources for any ancient or medieval (pre-gunpowder) ship sizes, I would appreciate it, particularly ones that mention length and beam and either draft or tonnage. The ones I’ve been trying to find information recently on are Chinese river warships and Imjin War ships, but good information on them is scarce (particularly after the rise in popularity of Zheng He thanks to Menzies’ work of historical fiction).

21

Sailing will be interesting, since there are multiple factors (some of which are “known unknowns” at this point). Obviously, wind direction and wind speed matter. So, also, does the type of rig (square sails, fore-and-aft, etc). That rig can have effects on the crew size (lateen rigs in particular require more crew for a given sail size).

WARNING: HIGHLY TECHNICAL (and potentially boring to laymen) DISCUSSION BELOW

One thing I am trying to do right now is work on some mathematical formulas to help me work out ships I’m not terribly familiar with. Part of this has involved learning about block coefficients and hull speeds.

Block coefficient is a way of describing (in a number) the overall shape of the hull underwater. To illustrate, if you multiply the length, beam, and draft of a hull, you get a number that assumes the shape is a perfect cube. However, ship’s hulls are streamlined to some extent, even on barges. The ratio of the actual volume of the hull underwater to the perfect cube is the block coefficient. Most ships are between a .4 (for a sleek yacht) and .8 (for a ultra large crude carrier - the giant oil tankers). This, in turn, ties into the tonnage of the ship, since the volume of water actually displaced has a mass equal to the tonnage of the ship. Being able to estimate block coefficient based on known dimensions lets me estimate tonnage for ships that don’t have a listed tonnage (or, on the flip side, if I have length, beam, and tonnage, I can estimate draft). The polyremes already done have block coefficients ranging from .35 (for the bireme) to .54 (for the quinquereme), averaging .47. This suggests they’re adequately streamlined, and that the bireme and trireme may be a bit light (they’re at .35 and .36, every other polyreme is at .47 or higher). Then again, they are the light warships.

Hull speed is the theoretical maximum speed of a hull, which is directly related to length - it’s 1.37 times the square root of the length of the hull (in feet). Many modern ships can go faster than this through planing or shaping the hull to change how waves form off the bow and stern, but for ancient ships, it’s an adequate rule of thumb for determining maximum speed. In my case, I’m also using a factor based on the block coefficient to figure hull shape into speed - that sleek racing yacht will, for the same length of hull, be faster than the blocky tanker (or, in ancient terms, the galley will perform better than the cog). Based on this, the maximum theoretical speed for the polyremes ranges from 13 knots to 15 knots, so I’m pretty happy with the burst rowing speeds of 9 to 11 knots, since those are under the maximum speeds and the power produced by the rowers may not be enough to get to maximum speed.

22

Excellent stuff. A few little nitpicks - your numbers of crew (sailors and marines) are on the high side. Any additional people not actually required for powering or steering a polyreme are endangering the vessel. The standard marine complement for a trieres/trireme was 14 marines (12 heavy infantry and two archers). They’d then throw themselves around as outboard steerage when necessary. Standard sailor complement was 10. The Romans did like to overload their ships with marines, but that was because they were poor sailors and usually operating close to land. If you were travelling any distance, those numbers would risk the ship if a storm blew up.

A bireme refers more to the oar arrangement than its size; you could get a ship with a similar number of rowers to a trireme that is a bireme (indeed it’s likely a lot of the larger polyremes used a bireme arrangement). I reckoned the “small galley” in the book was equivalent to a pentekonter or hemiolia. I then slotted in a “medium galley” representing a trihemiolia (again not necessarily accurate, it could also refer to a trireme that could lower its sails without taking their masts apart) with 120 rowers.

How will you measure oarsman quality (ie training/experience), condition (fatigue and food) and morale? Raw conscripts is fine for slaves chained to their benches or green crews, but what about professional oarsmen? Or well-trained citizen oarsmen like Athens could draw upon?

If you’ve distinguished Light Hulls, they should be undecked (since that aids in lightening). Which means you can target the rowers, since there’s just boards for moving about up top, rather than a complete coverage. It does mean better ventilation for the rowers, since they’re not enclosed in a small space.

A trireme was probably faster under oar than a quinquireme, something about the power:weight ratio. A quadrireme was also reckoned slightly faster, but nowhere near as durable in a fight. The heavier polyremes (sixes, sevens, etc) should probably be slower; there’s a number of good reasons the five remained the mainstay of any serious navy.

Lastly, I see ramming, but not oar-shearing as an attack. Skilled navies like the Rhodians preferred to attack the oars rather than risk getting stuck in another vessel and being boarded.

23

Kiero - thanks for the input. I know you did a lot of work for your Greek-inspired campaign, and I appreciate having another pair of eyes look this over.

The number of crew comes directly from the article Actium: End of the Roman Republic, by David R. Higgins, in Strategy & Tactics #201. While the numbers you cited for a Greek trieres are correct, a Greek trieres under these rules would be a light aphract trireme, and would have a maximum of 10 marines, 4 fewer than the historical number. The 15 “sailors” are all non-rower, non-soldier crew, which (on a Greek trieres) consisted of the trierarch (captain), kybernetes (helmsman), prorates (lookout), keleustes (bosun), pentekonteros (quartermaster), naupegos (carpenter/shipwright), auletes (piper), and 10 actual sailors, for a total of 17 “sailors”, 2 more than listed on the trireme description. I will admit to having 10 more rowers than the Greek trieres is generally listed with, so under the current rules, a Greek trieres will have 4 more people on board than it should - 10 extra rowers, 4 fewer marines, and 2 fewer sailors. If you have any sources regarding the crewing of larger polyremes, I would appreciate knowing what they are, since I am always looking for more information.

With regards to bireme, trireme, etc, the reme portion comes from Latin remus (“oar”), while the Greek version is eres (“rowing”) - hence a trireme in Latin is a trieres in Greek. The Latin is clearly not literal (i.e. “two-oared” up to “ten-oared”), since a quadrireme would not work, let alone a decireme, if it was literal oars. Three is the maximum number of rows that works. Four doesn’t work at all. Five is right out. Instead, the Greek is more correct in its terminology, and it refers to the number of rowers in each vertical column - a “two-rowing”, a “three-rowing,” etc, up to Ptolemy’s tesserakonteres, the “forty-rowing,” which was a catamaran of two “twenty-rowing” vessels attached to each other, thus being a (twenty plus twenty) “forty-rowing.” The number of levels is irrelevant with regards to the nomenclature of the ship in the Greek, and the Latin is just confusing. As hull length and ship mass grew, the number of rowers needed to move it adequately increased, which is why the “two-rowing” is smaller than the “three-rowing,” etc.

Oarsman quality is currently only tracked indirectly. The single-level modification abstracts the ability to use the a scaloccio rowing style (to anachronistically use a Renaissance Italian term for a method used well before the Renaissance) into a reduced maneuverability and lower cost for rowers, as the ship needs only one trained oarsman per oar. The use of slave rowers would mean lower morale, as with other hirelings, which will affect attempts to reach and maintain top speed.

The Light Hull modification was intended to reflect a thinner hull more than an open hull, but I will think about how to incorporate open hull forms into the rules so that rowers are easier to target.

Speeds are another area where I expect to have revision. The current numbers are from the Actium article, but I am still doing research on this plus other topics (I have around 5,500 pages of various naval archaeology papers on my to-read list at the moment). I also need to make a short road trip to one of my alma maters, since they have copies of “The Shorter Science and Civilization in China: Vol. 5”, “The Archaeology of the Roman Economy”, and “Mechanics of Pre-industrial Technology : Introduction to the Mechanics of Ancient and Traditional Material Culture”, all of which I believe will help me add to the rules. Right now, the maneuverability of the heavy polyreme is its only disadvantage, but that’s subject to change.

On the topic of oar-shearing, I just haven’t gotten there yet. As with rules for sailing vessels, it’s on the to-do list.

24

I don’t have sources, I’m afraid, going from memory of a range of things read where the author had sources, but I didn’t go back and check them specifically. I did always get the impression that the Romans had very high numbers of marines to compensate for their poor seamanship. They’d rather close and board than test their opponent’s skill. Plus it was leveraging their advantage in manpower.

It would be good to feature oarsman quality more directly - it gives the players an incentive to hire a professional crew or even train up one of their own if they have the opportunity to do so if it materially affects performance. And indeed it should.

Otherwise, carry on, looking good! I look forward to being able to playtest them at some point, when my Greek game resumes.

25

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:

  1. Maximum available tonnage is 60% of displacement tonnage. This is based on a 17th century estimate that tons burthen was 60% of tons displacement.
  2. Crew averages 150 pounds per member. This does not include equipment for marines. Crew mass subtracts from available cargo space.
  3. 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…)