What's a Ship's Speed?

[Yair]

I'm planning an adventure, and one (possibly the last) scene is meant to happen on a ship, as it sails into harbor. The entire scene should transpire between the time the ship enters the harbor bay and when it reaches the docks (it's kinda a race against the clock). The thing is, I have no idea how big to make a harbor's bay, or how long it would take a (sail) boat to cross it. Can anyone help me out here

Yair

 

[jpwic]

Hmm, there is no easy answer to this, it depends on the sail yardage, wind speed and all sorts of variables, but 7.5 knots/hour was considered the top speed of a caravel (IE Colombus had two of these.) For those a little less nautically inclined a knot is 1.150 miles/hour.. So 7 knots a little more then 8.6 miles per hour.

John

 

[Yair]

Actually, this is supposed to be a greek-style setting, so I presume a bireme or something like it is in order. But probably without the oars, as it is not a warship (right?). It's supposed to be a trade vessel, the kind who will transport nobility around, but I don't really know my ships, I'm afraid.

The speed will also be cut down within the harbor bay, for lack of wind, right?

 

[Aaron2]

The thing is, I have no idea how big to make a harbor's bay, or how long it would take a (sail) boat to cross it. Can anyone help me out here

There is a thing called "Hull Speed" which is a limit on how fast a ship can go without planing. It has to do with the suction of the wake.

1.34 * sqrt (Waterline Hull Length in feet) = Hull Speed in Knots.

So, forex, a 50ft ship would be limited to 9.48 knots.

Its a good rule of thumb to use. Remember that its the max possible speed under ideal conditions.


Aaron

 

[Aaron2]

Actually, this is supposed to be a greek-style setting, so I presume a bireme or something like it is in order. But probably without the oars, as it is not a warship (right?). It's supposed to be a trade vessel, the kind who will transport nobility around

Galleys (ships with oars and sails like Biremes) were used for both war and trade throughout the Med up until just recently (1800s). If the ship was used for carting about nobility it would definately have oars to keep it from getting trapped by the wind.

The Greeks (et. al) also had clinker built sail-only ships for larger cargoes.
http://www.mlahanas.de/Greeks/Ships/Kyrenia.jpg


Aaron

 

[Jeff Wilder]

Since people seem to be ignoring the actual question, I'll give it a shot.

To be truly a "harbor" -- i.e., insulated from the worst of storms -- an inlet probably needs to be indented at least a mile or so into the coastline. The very harbors have "pinched" egress ... with arms of land jutting out to almost meet at the "open" end. Alternatively, or in addition, reefs off the coastline can provide protection from sea-weather.

Because they're close to land (obviously), harbors tend to be shallow. This means that a ship can't travel anywhere near its maximum speed. In busy harbors, it could take a ship two hours or more to move from open ocean to its mooring place (which will only be a dock if the pier extends into deeper water, or if the boat has a shallow draft). Some harbors might be so dangerously cluttered (submerged rocks or earlier shipwrecks) that a harbor-master actually requires a ship to take on a pilot, or to follow a pilot-boat (for a "reasonable fee," of course). A busy and cluttered harbor would be slow-going, indeed.

Ships with oars are more maneuverable, and they tend to have shallower drafts, both of which will shorten mooring time somewhat.

In general, I'd say you can manipulate the variables -- size, traffic, hazards, motive power -- to set whatever time-line you want -- from open ocean to mooring -- between 45 minutes and four hours.

Hope this helps.

(BTW, this is mostly pulled out of my ass, based on reading and the like. I've done a lot of reading on the subject, because my own campaign is set in Freeport, but I still make no claims as to its real-world accuracy. Works just fine in the game, though.)

 

[Yair]

Thanks Jeff, that was most enlighting!

And thanks Aaron and John too. I think I've got a good handle on things now.

 

[Gez]

BTW: "Bireme" and "trireme" mean "twin oar row" and "three oar rows". So a bireme without oars is like a bicycle (two-wheels) without wheels. Or a chili-con-carne without meat. Or a cheesecake without cheese.

 

[ironmani]

I'm planning an adventure, and one (possibly the last) scene is meant to happen on a ship, as it sails into harbor. The entire scene should transpire between the time the ship enters the harbor bay and when it reaches the docks (it's kinda a race against the clock). The thing is, I have no idea how big to make a harbor's bay, or how long it would take a (sail) boat to cross it. Can anyone help me out here

Yair

Make it as long as you need it to be. If you want to put the pressure on the heroes, play the time hard. Look at your watch and select a time that the boat docks. ie Its 1 pm when the fight starts, and by say 1:10 is when the boat docks. Or you could just fudge it. Loard knows I've done that with my players. I've placed a timer on the table and told my players that this how long you have to figure out this puzzle. That was fun watching them sweat.....