Merchant Ships & Caravans Value

I’m still puttering around with my Pirate Cove thing ( looking to tie more in-depth values to hijink results.

I’ve been deconstructing the Merchant Ships & Caravans table, in concert with information given here:( that tell us what sort of trade traffic we’re expecting to be coming out of a market that we could pirate.

Taking a Class VI as the base example, it expects to field a single 10-horse caravan per month (presumably as a single atomic entity, as Merchants generate via their monster entry)

That’s about 6400 stone, on average, carried for that caravan.

The average cargo value listed in the MSC table (pg145) is 15,000GP for that 10-wagon caravan.

That’s about half the value you’d expect if you’d take the 6,400 stone the caravan carries and transform that into the “average load” (300 gp, 70 stone) - 6,400 stone of the 70 stone average load comes out to 91.43 loads @300GP per, or about 27,428 GP.

The multiplier for Class VI is about 1.83, going up to 2.01 for Classes I, II, III and IV.

That sort of consistency tells me I’m missing something either basic, obvious, or both.

If I alter my math to assume the average cargo load equates to common merchandise, at 180 gp/80 stone, I get multipliers of .96 to 1.05, which better matches the Avg. Cargo Value Carried.

So it seems like the MS&C table is either taking less precious cargo into account, or the ‘average haul’ value of 300GP/70st is a more adventurous number than would be expected…what am I missing (and/or messing up) here?

There’s probably repeated information from the one you linked, but this post might have something useful:

Ah! That is handy, thank you - that actually answers several follow-up questions I didn’t have formed yet.

So assuming 180/80 for the average cargo is more correct, according to that link. And, modifying my tables as such, my per-family “value of cargo” is 101 GP for a Class I, which given I worked backwards from the trade tables rather than forward from the actual demand of the populace as Alex did in that post, at least got me within some margin of error (as I’m also going from the later value of 30 Large Sailing Ships rather than 25 for the Class I)

Note, too, that the ships provided are of moderate size. The Small Sailing Ship (10k stone / 100k pounds / 50 tons) is actually too small for a Roman grain ship (the minimum was 10,000 modii, which works out to around 70 tons), and the Large Sailing Ship (30k stone / 300k pounds / 150 tons) would be a 3,000 amphora vessel, which was moderately common. During the late Republic, the muriophorio was a 10,000 amphora vessel, or roughly 100k stone / 500 tons of cargo. The grain ship Isis, based on its description, was somewhere around 1200 tons, about the same as the largest of the ships of the East India Company. The Roman cargo ship found at Madrague de Giens had a capacity of 300 to 400 tons, depending on how many layers of amphorae it carried. During the time of Nero, Egypt sent 8,400,000 stone of grain to Rome each year, or enough to fill 280 of the core book Large Sailing Ships. That was enough grain for four months, so Rome needed the equivalent of 70 ships per month just for grain (of course, Rome was also about a Class Negative IV, given how vast it was during the early Imperial period). Naturally, they preferred to use larger ships, although Isis was exceptional; most grain carriers appear to have been in the 350-400 ton range, or about 2.5 times the size of the Large Sailing Ship.


I’m going to attempt as much as I can to model this in a way that we’re presenting the average available cargo loads of active trade in a market’s sphere of influence - so the Judge can then divide that out into ships of whatever size fits their game; be that Early Egyptian to the Golden Age of Piracy in the Caribbean.

So I’m basically using the 30 Large Sailing Ship definition to arrive at a number of 900,000 stone of trade going though that (minimum size) Class I - which would be 9 muriophorios.