Sailing Vessel Question...

[Kid Charlemagne]

*casts summon CarlZog

How wide should a channel be to allow a 120 ft ship to safely navigate through a rocky coastal area? Also, any idea how big a harbor you'd want for that size of a ship (or even two) to be at anchor?

Background - I've got a very rocky, treacherous bay in my campaign world, and I'm wondering how dangerous it would be for larger ships (120 ft is a pretty big one in the current timeframe - roughly analogous to 16th/17th century technology) to try to navigate this area. Obviously, low speeds would be in order, but I want to know how wide an area you'd want before risking getting dashed on the rocks.

 

[edemaitre]

Harbors

The width of the channel would depend on a number of factors, including but not limited to the following:

-Would the ships you describe sail in under their own power? If they were towed in (by beasts of burden harnessed to lines, like early 1800s canals in the U.S. Northeast) or assisted by magic or tugboats, the channel could be narrower.

-How deep is the water? If it's a deepwater harbor near an ocean shelf, there might be fewer waves and more stable shipping (but stronger undertows or possibly submarine monsters and races), but a shallower channel would require more delicate navigation.

-Where are the prevailing winds? If a sailing vessel has to tack into the wind, it would require more space for an indirect approach.

-How wide are the ships? Large Renaissance galleons are different from ancient Mediterranean biremes or Viking knarrs. Assuming that your ships are primarily wind-propelled and wide as well as long, you should have at least a couple of ship widths.

Try checking online for examples of historical harbors in the period you mentioned. Happy sailing and adventuring!

 

[Nefrast]

*casts summon CarlZog
How wide should a channel be to allow a 120 ft ship to safely navigate through a rocky coastal area?

It should be wide enough to allow passage for the beam width of the ship. The beam width is the width of the of the ship at it's most extreme point, usually the middle part between stern and bow.

The bow width of a ship with a length of 120 ft. of course varies depending on the build, but I think it would typically be around 20-25 ft.

I dunno what radius a ship needs for turning maneuvers. But it will probably be smaller if oars can be used.

 

[Imagicka]

Greetings...

Well, it isn't the length of your ship that is important... it's the depth, and the width. How deep in this channel? How wide is the ship? How treacherous is the water? Does the wind/waves push the ship into the rocks?

Navigation through such places is tricky, but usually done by breaking out the row-boats and towing the ship, or having the crew pull the ship through any straight with ropes and such. Or of course completely avoiding the location in the first place.

Being a rocky bay, the whole point is that it's not so treacherous. That the water and weather is a little calmer than on the open water, otherwise there is no point in being there.

Being a rocky area, you would have navigators/pilots that are familiar with the region, and would help harbour ships in. You drop anchor outside the bay, and the pilot comes aboard the ship to pilot it in.

Being in a situation like that, the questions I'd be asking are:

• How treacherous is the weather/wind? How much is it pushing us off-course?
• What can we do to magically reduce/control the wind/waves?
• What can we do to either raise the water, or remove the rocks completely?
• Why do we even need to go in the bay, and expose the ship to danger?
• Why can't we just break out row-boats and get ashore that way?

What made rocky bays so appealing to pirates is that they could drop anchor in a bay, and wait out storms, where as other ships that had to enter the bay were entering unknown territory, where they didn't know where the rocks and shoals were.

 

[Umbran]

Unless you're doing an underwater encounter in which the exact width matters for a battlemap or soemthing, I'll suggest the exact width isn't important. It is underwater - the PCs almost never see it directly. So you can use "wide" and "narrow" rather than an exact number of feet.

What matters is the DC of the sailing check required to navigate the channel. And that ought to be done by deliberate choice - small boats have an easy check, gettign harder as the boat gets bigger. When the boat is mere inches narrower then the channel, and has a turning radiuson the same order as any turns in the channel, the DC may be in the Epic realm

 

[Tzarevitch]

*casts summon CarlZog

How wide should a channel be to allow a 120 ft ship to safely navigate through a rocky coastal area? Also, any idea how big a harbor you'd want for that size of a ship (or even two) to be at anchor?

Background - I've got a very rocky, treacherous bay in my campaign world, and I'm wondering how dangerous it would be for larger ships (120 ft is a pretty big one in the current timeframe - roughly analogous to 16th/17th century technology) to try to navigate this area. Obviously, low speeds would be in order, but I want to know how wide an area you'd want before risking getting dashed on the rocks.

How small are you talking? Do you mean small like some of those little rocky fishing harbors on the Italian coast or something you see in a pirate movie? If so that is a cove or an inlet not a harbor. 120' is about the size of a carrack. It would be dangerous to enter a little rocky cove like those with a sailing ship of that size and it would have trouble geting out without help.

Entry and exit channels matter less as long as they are deep and straight enough and the current/wind isn't too bad. Honestly, the ship could probably navigate an approach channel of about its own length so long as it is straight, deep and cross wind/current is at a minimum. If the approach channel has turns or bad currents you need much more space. If the turns are sharp or the current is bad you need a LOT more space and it may become downright unsafe to try.

Sailing ships don't start or stop on a dime and they certainly don't turn on one. In a tight harbor, you can use tow boats (longboats with rowers) to tow sailing ships into position. Slow speed also won't help much because speed is an imprecise thing for sailing ships and there is also the matter of minimum steerage speed. Steerage speed is the minimum speed that a ship must maintain in order to be able to use its rudder to steer. In other words, there is only so slow a ship can move and still maintain its ability to steer itself.

The harbor you describe seems like a very bad one for sailing ships to try if they don't have to. If the bay/harbor is that treacherous, I would suggest setting up an anchorage at the safest point (beyond the rocks) and have cargo transferred to oared barges.

As for actual dimensions. That I have no idea. I would think at least a quarter-mile across to be safe if it has to maneuver without tow boats. If there are rocks or bad currents you may need a lot more. Also, there are maps on-line for medieval cities. You may want to try searching for some maps of smaller mediterranean cities to check out their harbors.

Tzarevitch

 

[kyloss]

You can always try to figure it out experimental with a 2 liter bottle some string and a tub full of water, just remeber that all of your experiments are IDEAL conditions, and pulling with the string represents towing or magic movement. Fill the bottle with varying amounts of water for draft depth and for wide ships use 2 bottles. Besides its fun to play with toys in the tub. And dont forget the obstructions to simulate the rocks.

 

[Pbartender]

Unless you're doing an underwater encounter in which the exact width matters for a battlemap or soemthing, I'll suggest the exact width isn't important. It is underwater - the PCs almost never see it directly. So you can use "wide" and "narrow" rather than an exact number of feet.

What matters is the DC of the sailing check required to navigate the channel. And that ought to be done by deliberate choice - small boats have an easy check, gettign harder as the boat gets bigger. When the boat is mere inches narrower then the channel, and has a turning radiuson the same order as any turns in the channel, the DC may be in the Epic realm

I think Umbran's got the right idea here, though...

You can always use Treasure Island as a guide:

The Hispaniola, described as a 200-ton schooner*, was anchored in the south inlet (look for the little anchor symbol just south of the swamp) in 3 fathoms (18 feet) of water, and was later beached in the north inlet in less than 2 fathoms of water. Also notice the small cove on the northeast corner of the island.

The inlets are roughly 1/4 mile wide at the narrowest, and about 1/2 mile wide at the widest.

*For reference, a typical 350 ton brig would have a 90-100 foot length, a 30 foot width, a depth of 15 feet or so, and carry a crew of 45-80 men.