Comments on: Simulating Roman Trade Patterns

By: Malcolm Snook

Malcolm Snook — Wed, 11 Mar 2015 08:58:59 +0000

This is an amazing piece of work. I think we probably shouldn’t underestimate ancient seafarer’s abilities to navigate out of sight of land. Having lived on a boat and sailed for many years, much of it in the Med I know how heavily I relied on modern technology and charts, but if you read Sailing Alone Around the World by Joshua Slocumb (I know it’s not ancient as such) you will see just what can be achieved in navigational terms, with very little equipment by a seafarer with a lifetime of experience.
However where I take issue with this work is in the belief that a boat of Roman design with a square sail, carrying cargo could tack against the wind at all. My own ketch could ‘point up’ to a similar angle as shown in the diagrams above but her course over ground made no progress at all due to leeway. Even if a Roman ship could achieve the angles shown, which I seriously doubt, that still would not represent a true course. To be honest I think she would actually lose ground in real terms. This is partly why ancient seafaring was so dangerous as situations would arise where you could be pushed on to a lee shore with no possibility of escape, no matter what action you took. The most optimistic scenario is likely to be that a Roman ship could sail in three directions at best on any given day ie if the wind was from North she could go anywhere with no northerly component in it at all. I believe trading patterns must have been seasonal and that the ancients knew very well which winds they could expect to blow in any given season, Auster, Boreas etc, just as modern yachtsmen know to expect the Meltemi etc in particular regions at particular times. Try sailing northwards in the Aegean in mid summer!

By: Ben Allen

Ben Allen — Mon, 09 Mar 2015 01:22:55 +0000

Great work,I did not see a graph, showing number of days it may have taken to arrive at a certain port? Has any one ever attempted to reconstruct a roman ship? I have built a few boats , not sure I would want to attempt the mortise and tenon jointery. Thanks, very interesting!

By: Ronan Mandra

Ronan Mandra — Thu, 05 Mar 2015 03:04:48 +0000

This is a rephrased comment carried forward from my comment in Week 6 of the Jan 2015 Portus MOOC.
Figure 1 shows diagram of a Roman ship sailing against the wind. My understanding is that square rigged ships used wearing to change tacks. That is the vessel turns away from the wind with its stern of the vessel going through the eye of the wind. This was done as the square rigged ships were designed for wind pressure from the side or back. Wind pressure from the front might snap the mainmast. Alternatively, if the square rigged ship could go through the eye of the wind it was called boxhauling — to put (a square-rigged sailing vessel) on a new tack by bracing the head yards aback and backing onto the new heading. Ref: http://dictionary.reference.com/browse/Boxhauling
So my question is: “How did the Ancient Roman vessels change tack when going into the wind?” Note that I’ve looked for an answer on the internet without success. By the way, if Roman ships used wearing to go into the wind, Figure 1 should be updated.

By: Steve Harris

Steve Harris — Tue, 03 Mar 2015 14:11:35 +0000

Dave

What a great piece of work and very helpful. It’s amazing how different people with different skills are able to help one another so easily these days.

Just a thought, I know that the tides in the Med are only very slight to non-existent but maybe they could have had a small impact on the destination of a sailing boat in Roman times. Would they have been enough it impact your model?

Keep up the great work.

Best wishes.
Steve

By: Trevor Newman

Trevor Newman — Tue, 03 Mar 2015 10:05:00 +0000

Thanks Dave. Understood. My guess is that the trade to Portus was so great and demand for say oil marble and grain was so enormous that the supply chain could only be maintained by sheer shipping numbers. A square rigger is by its nature wide and stable. It could therefore be loaded to the gunnels with goods….(but as a result v slow). Therefore with inaccurate navigation and ponderous vessels this is probably the only answer?
Trevor

By: Trevor Newman

Trevor Newman — Tue, 03 Mar 2015 08:33:24 +0000

Hi Dave
I can find no navigational evidence for the Roman period on the web or elsewhere. In addition to sail a square rigged boat without a keel in anything other than a following wind would be directionally impossible with any accuracy thus tacking would be messy with huge lateral drift and next to no headway. The question therefore is how did they get from one side of the Med to the other with any accuracy at all. The only reasonable assumption would be “point and shoot”and navigate by sight when you get to the other side! What is you view Dave? With kind regards Trevor

By: Ronan Mandra

Ronan Mandra — Sat, 03 Jan 2015 05:07:47 +0000

If the Roman ships were using square sails, they would have to wear ship which is different from the sinusoidal curve shown in your diagram. For a Youtube video on wearing, check out: https://www.youtube.com/watch?v=Vfu_ZPFHlTU. From this video on a 19th century or so ship, it takes anywhere from 5 to 10 minutes to wear ship depending upon the wind speed.

Just some thoughts. Great article

By: Charles Weager

Charles Weager — Wed, 16 Jul 2014 17:18:43 +0000

I am fascinated by this, unfortunately have only snippets of probably unreliable information to guide me. For my sins I have just been to the Peleponenese which means a lot of reading and I have just read Lindsay Davis’ book “A Dying Light in Cordoba”. Which, while fiction, tackles the Roman Olive Oil trade between Ostia and the Spanish ports and “The Vikings” by Tim Severin which tackles sailing from Scotland in an arc eventually arriving in Newfoundland. I used to live on a Roman Road north of Bridgwater at Puriton, Somerset. At Dunball, Not Combwich, there may have been an export port for Roman Lead and Silver from the Mendip Hills (uncovered while straightening an M5 access road). This trade is mentioned by Pytheas. As a former Hydrographic Cartographer I understand the use of the North Atlantic Gyre by Colombus, anti-Clockwise from the Azores and the explorers such as Vasco Da Gama using the South Atlantic Gyre to reach their destinations, Clockwise to Brazil and then across to the Cape of Good Hope.
The points raised by Michael Byrne and Jane Anderson are pertinent because until the use of the Carvel Sail these voyages would have been nigh on impossible without some form of “extreme navigation”. I understand that even the Arab Dhows in the Indian Ocean had to wait for the correct Monsoon wind before being able to make the voyages that they managed.

By: Dave Potts

Dave Potts — Tue, 01 Jul 2014 22:15:51 +0000

What is the url for this resource?

Dave.

By: Dave Potts

Dave Potts — Tue, 01 Jul 2014 22:11:39 +0000

Patterns of trade are always subject to change and outside forces. when the Roman empire controlled both sides of the mediterranean, there were few issues, but outside of the pax romanan there were always going to be ‘problems’ with taxes different concepts off what an acceptable cargoes, getting your ship repaired if you have no form of acceptable/understood credit etc.