> can also sail faster than the wind at times.
Really? Can you elaborate?
Really? Can you elaborate?
Or you can just think of it like squirting toothpaste.
The wind pressure on the sail and the water pressure on the keel form the two "objects" being pushed together and the sailboat "squirts" out the side.
Edit: The angle between the sail and the keel is like the angle on the triangle. The keel really was a great invention.
It's two concurrent visualizations of the same force.
The pressure that the air above the wing applies to the top of the wing is lower than the pressure that the air below the wing applies to the bottom of the wing. The net force is upwards.
The boat starts moving forward. But, because the wind is perpendicular to the boat, even when its moving the wind is still coming in at the same velocity, so it's still producing thrust. If you can get the boat efficient enough, it can harness enough of that wind energy to reach a velocity along the sailboat's line of motion higher than the velocity of the wind relative to the ground.
Note that boats can only do this when sailing at least somewhat offcenter from the wind direction. When sailing directly downwind, the faster the boat goes, the slower the wind is relative to the boat, leeching away thrust.
The motive force on that vehicle is a gear and chain between the prop and the wheels. And prop blades are set at an angle to the wind.
Consider a boat on a beam reach, where the wind over the water is at 90 degrees to its track. If the boat is travelling at wind speed, the apparent wind over the deck is at 45 degrees to the bow.
The useful angle of attack for airfoils goes up to about 15 degrees, so let us assume that the sails are set to this. Therefore, the chord of the sail is at 30 degrees to the boat's track, its lift is at 60 degrees to its track, and so half the total lift is in the direction of motion [1]. So long as this exceeds the total drag of the boat, from the water and the air, then it will continue to accelerate.
[1] To simplify (and to go faster!) assume a multihull sailboat, hydrofoil, or a dinghy with its crew hiked out so that is not heeling appreciably, as when a boat is heeled, a component of its sails' lift is directed downwards.
And of course here comes that:
https://newatlas.com/wind-powered-car-world-record/11346/
"March 29, 2009 With a wind speed of just 30mph (48kmh), British engineer Richard Jenkins has set a new land speed record for a wind-powered vehicle at blistering 126.1mph. "
\\ wing is to wind as seed is to fingers \\
There are two kinds of sailboats. There's the big square sailed ones which always have to move downwind. Then there are the triangular sailed ones, which can move in any direction except for right into the wind. (Maybe a 30 degree on each side dead zone).
The square sailed boats can't move faster than the wind, as they just rely on the air pushing on the sail to move with the wind.
That's also how the triangular sailed boats move when moving directly downwind. They too can't outrun the wind.
However, when moving sideways to the wind, the wind passes over the sail, which looks like a wing sticking out of the water. Like a wing, there's a "lift" force generated, although it's not up but sideways. The boats also have a fin sticking into the water, which prevents the boat from slipping directly along with that "lift" force, and instead move forward.
Actually, that's not true. Square rigged "pirate-style" ships are more efficient when sailing downwind compared to fore-and-aft style sailboats, but they can still sail just fine close-hauled (into the wind) or on a reach (perpendicular). There are some efficiency pros and cons to both styles, but they all have the same aerodynamic capabilities.
The main reasons square-rigged ships fell out of fashion, as far as I know, are mostly logistically. Square-rigged sails make sense when you have a really big ship. A single huge fore-and-aft sail would be too hard to handle. Square-rigged ships break that sail area down into a larger number of smaller individually manageable pieces.
But larger vessels are almost all powered now. For a smaller sailing vessel, it's easier to manage the simpler Bermuda sail plan, and its more efficient. I think maybe square-rigged ships have an efficiency advantage when going straight downwind, but most sailboats simply carry a spinnaker to cover that case.
(Caveat: I'm not a sailor, I've just read some textbooks.)
They typically (or maybe always?) have "staysails", which run fore-and-aft between the masts, which works mostly like the main triangular sail you think of with a simple sailboat (with the exception that, as far as I know, these staysails aren't on a boom that can change its angle relative to the ship). These are able to take the wind at an angle but still generate forward thrust.
The "yards", the sections that hold the square sails perpendicular to the ship, are also able to rotate between perpendicular and nearly-parallel to the ship, which lets them take advantage of a wide range of wind directions.
(I'm also not much of a sailor, I've just sailed some tiny single-sail boats, but I've learned a lot while reading through the Aubrey-Maturin series and from playing the game Naval Action)
This isn't quite right, as split fore and aft rigs existed that solved this problem. I suspect it is more that power replaced sail for crossing oceans and square sails make little sense for coastal work so they had already switched to fore and aft rigs (with a few notable exceptions, such as Humberkeels in the north of England).
True, but it gets more complicated than that. For fast long-distance commercial travel they were replaced by the steam and later diesel propulsion, which both a) were faster and b) required less crew (so were logistically superior).
On the other hand, where sailing is still used (and that's mainly sport and leisure) the square rig is still here, only in an evolved form: the spinnaker. But whenever the speed is not the primary factor, fore-and-aft rigs (primarily Bermuda) is preferred because it requires far less crew. And then again, when the goal is to have plenty of crew -- like in some navy office training -- classical square rig is still highly merited [1].
I think that only really applies when the sails were set from aloft. I'm familiar with square-rigged cargo vessels of around 60ft in the UK that were crewed by 2.
Some numbers from Wikipedia:
In 1902, the Preussen, famously huge square rigged ship launched with a crew complement of 45-49 while the contemporary Thomas W. Lawson, schooner rigged and even bigger, got by with 16-18.
https://en.wikipedia.org/wiki/Preussen_(ship) https://en.wikipedia.org/wiki/Thomas_W._Lawson_(ship)