Some good stuff for a roleplay? Finding the right wind!
Bonhumm wrote: ↑
Wed Aug 21, 2019 11:34 pm
So, unless the airship is trying to be inconspicuous or flying over a mountain range, I don't see why they'd go over a 1000 feet... or even 500.
I really would not discount the importance of finding a tailwind. It is absolutely vital.
Today's racing sail boats with fancy hulls and computer designed sails, etc. are amazingly fast. I read that the max speed achieved in the America's Cup is 47 knots. But lets forget these modern racers. A "typical" sailing schooner today might average 5 knots in most conditions, and top out at 10 knots at perfect conditions. The Cutty Sark was famous for being a fast sailing ship and topped out at 17.5 knots average for one 24 hour period. I see references to Viking ships averaging 4 knots over long distances, and galleys averaging 3 knots, with short sprints to 5 knots.
Looking at the 3rd edition gamemasters companion, most water vessels have speed ratings of close to 5 (Their water sailing speeds table is ridiculous and I am ignoring it). Most Air vessels have speed ratings of 10 to 12. So they tend to go at least twice as fast as sailing vessels. According to that book a speed rating of 10 is 16 mph (14 knots) and a speed rating of 12 is 20.9 mph (18 knots).
This is all MUCH slower than gasoline powered aircraft, Even the biplanes of WWI had max speeds of 100 knots or more. If you are zooming around at 100 knots, you can mostly ignore a 10 knot headwind or tailwind if you want. In the worst case scenario you are going to take an extra 10% more time getting to your destination. But if your max speed is 14 knots, then just a 10 knot wind is going to make a HUGE difference in how fast you are traveling.
OK, here is the thing. Once you get up above the trees and the buildings. There is usually a wind, even if it is not felt on the ground. These winds are at different strengths and at different directions at different altitudes. But it is not at all uncommon for the winds (just 100 feet off the ground) to be at least 5 or 10 knots. I mean sometimes there is no wind, but more than likely there will be.
but if you are in an airship going 14 knots. it is difficult to ignore a 10 knot wind. If it is a headwind, you are only making 4 knots over the ground! If it is a tailwind, you are making 24 knots over the ground. If it is to the side, you are actually traveling downwind of your target and you need to adjust course so that your true direction of actual travel over the ground is towards where you want to go.
And if your airship is going 14 knots through the air, and you are facing a 15 knot headwind, you are actually going backwards over the ground.
So I submit that the most important skill in piloting an airship, whether sail powered, oar powered, or powered by Blood Magic, if finding a good wind. Hopefully, somewhere up there is a wind that is going more or less in your direction. Or at least it is not going against you, and you need to find it.
It is probably usual for a captain and the ships elementalist to be up at dawn, the captain looking at clouds, the elementalist talking to air spirits. The ship might launch into a headwind that is pushing them backwards, but the crew works hard at gaining altitude until at 11,000 feet, they find the 40 knot wind that is going just 30 degrees off of their preferred course. Now that 40 knots is three times faster than they could go by themselves, so the crew need not work hard, just hard enough to offset that 30 degree difference between where the wind is blowing and the course they want. Then, after a lazy day of letting the wind take them in the direction they want to go, they use the last light of the sun to land the ship again. Perhaps the next day the captain and elementalist decide that today there is no tailwind to be had an any height/route they want, and they don't launch the ship because the wind would push them farther from their destination.
Winds aloft can be quite strong, and way up where the jets are, the jet stream's are often 170 knots or more. The typical wind aloft, even at treetop level will frequently be much faster than any airship can fly. So if the wind at your flight level is not going the desired direction, you are sailing backwards as measured over the ground. But often at a different altitude there is a different wind, that might be more to your liking.
Captains need to know the typical winds to expect along their route. There might be routes that can only be traveled certain times of the year, as during some months there may not typically be winds going in certain directions. Before the technology advanced to where ships could
sail against the wind, there were some trade routes where everybody sailed in one direction for 5 months out of the year, then when the winds shifted, they turned around and sailed back in the other direction. A square rigged sailing ship can
sail against the wind, but it is faster for a square rigged ship in the Caribbean to sail to Europe via Boston than to sail directly. It is twice the distance, but both legs are with the wind behind it, so it is faster and easier to sail trice as far than to try to beat against the prevailing winds. Airships add an exciting and challenging third dimension. A captain need not only concern himself with surface winds, but can make use of winds aloft as well.
There are good role-playing opportunities here, and the jargon when the captain explains why he has decided to remain at anchor today need not be complex. And hey, while we are waiting, you guys could explore! Honestly, it is not a complex topic at all, but it does complicate travel times. That 3rd edition book has a nice table that tells you how many miles an airship of a certain speed can travel in 8 hours. The fact that this table should probably be talking about airspeed, not speed over the ground, and that speed over the ground depends more on what the wind is doing than how fast a ship you has is a complication that many gm's might choose to ignore.
Or of course you can ignore the whole "headwind / tailwind" thing. A GM might want to simplify the topic out of existence and rule that the magic of airships is such that the wind does not push them around (except insofar as they have sails that are designed to use the wind), and their speed is always ground-speed, not airspeed. IE: a ship that travels 14 knots into a 20 knot wind will be traveling 14 knots over the ground, and the crew will feel a 34 knot wind, but the wind will not be pushing the ship backwards. A sailing ship makes use of the interaction between the movements of air and the water it sails in to move. It could be that an airship is somehow interacting with the ground or ocean that is far below it, and it's movement is thus always in relation to the ground, not the air it is in. This keeps things extra-simple, but in my opinion the whole headwind/tailwind thing adds an exciting dimension to traveling the skies. It allows the GM to add an easily understood aspect of skill and danger to air-sailing.