[HR] Naval Rules

Just to test the construction system, I decided to try out a giant merchantman. It’s loosely based on the Roman grain ship Isis.

Our starting point is that the ship was 180 feet long, over a quarter that in width, and had a cargo hold that was 44 feet deep from the main deck to the keel.

So, to start, we’ll use a 180 foot length and a 3:1 beam, which gives us a rather tubby 180x60 ship, with a 15 foot draught. That’s probably not enough to be 44 feet from the main deck, so we’ll add a second deck to drop the draught to 22.5 feet. The ship has a seaworthiness of 5, and as a giant merchant ship, no rowers will be added. Isis is a 2068 ton ship, with a base capacity of 413,600 stone. Her base shp are equal to her tonnage, which is 2068. Because the Romans used mortise and tenon joining, she’ll be considered a clinker ship. This give +10% shp and +1 seaworthiness, but means rowers or artillery cannot be carried on any deck except the top deck. This means Isis has 2275 shp and a seaworthiness of 6.

At 180 feet, she could have up to six masts, for a total of 13 sails, but that’s far more than what the Romans actually did. Instead, we’ll go for a modest 3 masts and 5 sails. With square sails and the beaminess of the ship, that will require 66 crew to handle the sails. This also gives her a speed of 2 hexes per round when sailing with a fresh breeze (0 modifier) from an aft quarter (also 0 modifier). Given that the base turn rate for Isis is 11 (one 60 degree turn every 11 rounds), we’ll also add a bowsprit (which requires 2 more crew), to improve the turn rate to 10. It’s not much, but it makes her a little less of a wallowing pig. The total weight of masts, sails, and rigging is 5400 stone. Carrying a full spare set of sails and rigging adds another 1800 stone, so the total rig is 7200 stone.

With 68 crew needed to run the ship, an additional 7 crew (captain, navigator, bosun, and 4 spare sailors) are added to make an even 75 crew. At an average of 15 stone weight for a human, the crew weighs 1,125 stone. For the sake of this example, each crew member has 200 stone of personal gear and rations for the voyage, for another 15,000 stone in crew weight. The total crew weight is 16,125 stone.

Adding crew weight plus rig weight, the ship could sail with equipment taking up 23,325 stone, which would allow Isis to theoretically carry up to 390,275 stone in cargo, or about 1950 tons. However, a ship like this would also have marines aboard, and the real Isis also carried artillery on her top deck. These would reduce cargo space accordingly, but it shows the massive amounts she could theoretically carry.

For cost, the hull of Isis alone costs 227,500 gold pieces. The masts cost 36,000 gold pieces. Rigging costs haven’t been figured yet, but I anticipate they’d be somewhere around the cost of the masts, maybe a bit more. A normal crew would be 563 gold per month. So, it would cost approximately 300,000 gold to have the ship built, and a minimum of 563 gold a month to have a competent crew handle her. She can haul large amounts of cargo, but only at a speed of 4 knots in a moderate breeze, and she’ll pretty much only be used between Class I markets because of the amount of cargo she needs to haul to be profitable.

Excellent stuff.

How would a vessel at that level of seaworthiness handle storms and other bad weather at sea?

Seaworthiness 6 can withstand up to Beaufort Wind Force 9 before it starts taking damage. That’s more than I intended pseudo-Isis to be able to withstand, but it gives me a starting point to work from in balancing the rules. I haven’t done all the ship options yet, and this convinces me there need to be some that add a benefit but reduce seaworthiness to reflect ships designed for areas with calmer weather.

Out of curiosity, what happens under your rules if you add 13 masts to this design? I ask because the Romans presumably didn’t do so because the marginal return past the number of masts it actually had was poor, or even negative…

There are two constraints on masts. The first is a hard rule that a ship can only have 1 mast per 30 full feet of length, so the 13-mast ship would need to be 390 feet or longer. The second is an effect rule that if a ship has more masts than its Base Seaworthiness, it gets -1 to Seaworthiness for each additional mast. This represents the fact that as masts are added on, there are more stresses on their anchoring points and amount of weight higher in the hull increases, reducing stability. There are also diminishing returns built into the speed chart once you get to about 8 knots or so. Below that, each pair of sails adds about 2 knots to speed. Above it, each pair adds about half a knot.

Cool! I have zero knowledge that would allow me to assess the accuracy, but it certainly sounds real-world.

Just a small “ah-ha!” update. I took most of September off from writing because it’s my company’s end-of-fiscal-year, and my job gets crazy for about six weeks. When I came back to my files and started reading, I realized I had been trying to write the combat rules, non-combat rules, and construction system all at the same time, which made things incredibly convoluted. I am going to go back and reorganize what I have, and then focus on one area at a time. Hopefully that will let me be more efficient in how I write…stuff.

Good to hear. Making me feel a little guilty on how little I’ve done on MLT lately…

I’m doing a major revision right now - the original draft of the rules used a movement chart where speed bonuses or penalties moved you up or down the chart, but it had a lot of fractional movements. It worked OK for single-ship actions, but would be totally unwieldy for even a small squadron. I’m switching instead to a point-based movement system, which (so far) is going much smoother. There’s still math involved, but it’s much simpler math.

Damn, this is cool!

I might have missed these points, but here’s my two cents:

What happens if the captain decides to cancel a burst half way through? Or if the burts has to stop before the 2d3 rounds are up? Is the downtime in which the ship is slowed affected?

Perhaps you could look into defenses like protecting a harbour with a large chain - that would certainly ruin someone’s day.

And a few things I’m sure my players would come up with:

  • what happens if I chain 40 zombies to the oars? Obviously they won’t get tired, but I’m guessing bursts are out of the question as well.
  • more importantly: fire. Do you have riles for people trying to set other ships ablaze? Or was that historically not as common as I would imagine?

Good to hear you’re still working on this, I’m really looking forward to the results.

“What happens if the captain decides to cancel a burst half way through? Or if the burts has to stop before the 2d3 rounds are up? Is the downtime in which the ship is slowed affected?”

Good question - I hadn’t considered that yet. There should still be some downtime, but it probably shouldn’t be the full time, since the rowers haven’t been worked to exhaustion.

“Perhaps you could look into defenses like protecting a harbour with a large chain - that would certainly ruin someone’s day.”

evil grin I should point out that one of my major sources recently is William Murray’s ‘Age of Titans,’ which is heavily about naval siege warfare, including harbor defenses and using ships to ram city walls(!).

"And a few things I’m sure my players would come up with:

  • what happens if I chain 40 zombies to the oars? Obviously they won’t get tired, but I’m guessing bursts are out of the question as well."

Yes, undead won’t be able to do bursts. However, there is discussion of “non-living” power sources in the strategic movement section. That could be a steam engine, a magical engine, or Residual Human Resources. They may not be as fast for tactical movement, but their endurance is higher than living rowers.

“- more importantly: fire. Do you have riles for people trying to set other ships ablaze? Or was that historically not as common as I would imagine?”

…OK, that needs to be added to the To-Do list. If nothing else, there were the Rhodians (I think - may have been Cretans) using firepots, fire arrows, and (of course) Greek Fire. Plus, PCs have a tendency towards pyromania, so even if it wasn’t totally historical, it would still need to be included. Besides, at some point, somebody with a ship WILL anger a dragon (in addition to pyromania, PCs have a tendency to rather poor life decisions).

I’m somewhat wondering now how many water elementals it would take to move a ship of a given size, if they flatten themselves up underneath it and essentially “carry” it.

As an aside, it would be fun to have some sort of conversion system from whatever horrible sea monster to the statistics that would be compatible with your ships in combat, for polyreme vs. dragon turtle (next on SyFy!)

One side effect to switching to a Movement Point system is something that I just finished working out the math on. The MPs scale almost perfectly as long as I play around with time scales a bit, as follows:

On a tactical scale, 1 hex is 30 feet per 10 seconds, and generally costs 2-4 MP (depending on movement type, wind direction, etc). At a 6-mile hex size, the same MP will let you move 1 hex in 3 hours, so moving to a 3 hour time scale means the same MP equals the same amount of movement. Likewise, at a 24-mile hex size, the same MP lets you move 1 hex in 12 hours. No messing around with the number of MP, it’s just zooming in or zooming out to different scales of distance and time.

I had mentioned I needed to reorganize what I had written. I spent some time looking at how past books were set up, and using them as inspiration, have reorganized my working document. The combat rules, large-scale movement rules, and ship construction rules are mostly complete, with 13 pages of text in a semi-edited format. There will be at least two more sections, one with sample ships and the other…well, that would be telling.

Based on the Oberstimm river craft, here’s a light vessel that may be of use if characters want to travel between the river forts in SSoS:

River Galley
56’x8’x2’ (freeboard 1’4”)
Tonnage 9
shp 27
Base Seaworthiness 3
Armor Class 1
Base Rowing Speed 4 (equivalent to 4 knots or 1 hex per 90 minutes at 6 mile scale)
Required Rowers 22
Rowers 28
Rowing MP 4
Modifications: Light Hull (-2 AC, +1 MP), Flat Bottom (-1 MP, +1 save vs. ground, -2d6 damage from grounding)
Cargo capacity: 5400 stone
Cargo used: 14 stone (oars), 450 stone (28 crew and 2 passengers), 450 stone (5 days’ rations), 3000 stone (10 stone of equipment per person)
Cargo available: 1486 stone

Design considerations: The original ship was 51.5’ by 8.5’ and around 3.3’ from top to bottom. It worked out best as a 7:1, at 56’x8’x3.3’. It’s known to have a flat bottom, and reproductions done by Projekt Romerschiff have been rowed at around 4 knots (note: I do not know German, but Google Translate is a miracle of technology), so the light hull was added to bring the speed back to 4. This type of boat would be used to transport patrols. The 10 stone of gear is 6 stone for banded armor, 1 stone for shield, 2 stone for weapons (sword, dagger, and either spear or bow and arrows), and 1 stone for miscellaneous gear. Rations were calculated at 3 stone per person. If the troops were actually going on patrol, more rations would be carried, but at 1 stone per person for the days expected to be spent on patrol, rather than the 3 stone for rowing.

I hope this is helpful to someone. Working it through helped me see that I do seem to at least be in the ballpark for stats, and can do this for a relatively small vessel suitable to a (large) adventuring party.

…and I forgot to include cost. The hull of the ship is 2700 gp, the benches for rowers are 140 gp, and oars are 70 gp. Rations are 21.5 weeks of rations, so between between 6.5 gp and 130 gp for rations (based on 3 sp lowest for fresh and 6 gp highest for iron). For the sake of argument, make it 90 gp so that everything totals up to 3000 gp.

I finally managed to dredge this thread up from the deep - what's the latest?

I moved in November 2015, and haven't done much since. The rules are up to around 15 pages. There's also a page of notes regarding harbors and seven fully-statted ships (a river galley, four types of merchant vessel ranging in crew size from 4 to 21, a bireme, and a trireme). However, there are some gaps in the rules - one of the ships has a sewn hull, which I apparently never finished adding to the rules.

Fair enough, real life happens. Any plans to return to it in the near future?