Usefull stuff for boatbuilders and virtual sailors...
First some stuff from SL. Further down some explanations about stuff in the real world.

Racelines, timers, start procedure, buoys, windsetters, windgetters, shadowing... in RL and in SL. This is only the beginning.

The racelines shout the remainding time to start in unixtime on channel -8001. This is what you need to know in order to make an onboard racetimer or an automated flag and gun system.

To make a timer: See racelines.

Starting procedure
SL by convention uses a 3 minute starting procedure. RL RRS uses 5 minutes. One might argue that 3 minutes is enough when the wind never changes and there's no current and no line skew to discover. However, if there is windshifts, deliberate lineskew current and possibly also a less than perfectly positioned top mark, it would often seem that five minutes is not enough.

Here's the RL procedure:
5 - gun + class flag up
4 - gun + preparatory flags (starting rules) up
1 - horn + preparatory flags (starting rules) down
0 - gun + class flag down

No more on that. Read the book.

Something about bopping buoys and currents and stuff. TBD.

SL wind
SL wind was designed to make plants and stuff look good. It's really fluffy, puffy and circulating 360 degrees every other minute or so. Completely useless for kites, boats and planes. That's why we need to synthesize wind with windsetters and stuff.

The the WWC windsetter does not communicate continuously with the boats. The WWC windsetter announces its presense and the active race if any on a regular basis. The boats pick that up and request - by email - the full environment of wind, waves, current and local variances. The request is sent once, and that's it.Now the boat knows the racing environment.

The WWC setter keeps  list of all boats in the race, so if the RD chooses to make a sudden change in order
to simulate a huge cumulonimbus cloud passing by, then the WWC setter will email those settings to the boats in the race.

These are the modules in the boats that communicate with the windsetters, and when they have received the windsettings, the windgetters also synthesize the wind.

Explanations of stuff from the real world:

Small changes in winddirection often swinging back and forth around some 5-15 degrees with a period of 15 to 20 minutes. Smaller shifts are also present with gusts.

Small puffs of stronger wind typically lasting 5-25 seconds and with a tendency to bend the wind so the windangle increases.

The angle at which the boat leans to the side.

Wind disturbances caused by one windward boat disrupting the windflow for a leeward boat.

Wind disturbances caused by one boat bending the windflow for a boat aft.

The ocean water flowing in a certain direction. Examples are tides, the gulfstream, local currents caused by changing winds.

Waves travel with the wind and they are affected by the depth.

Bow wake
The waves created by a vessel travveling through water. The bow wake travels like a wave from the point of its creation. The splash typically creates foam and bubbles that form the outer edge of the trailing wake.

The trail of a boat moving trough water. It is where the ocean clashes together after being split by the boat moving through the water. There is a million vortices in the water stemming from the boat and the keel. This typically forms a line of disruption in the ocean surface trailing the boat. Visible several boatlengths behind... five boatlengths at least...

Wool strings of approximately 15cm placed in the first quarter of the jib. Visible from the helmsman position. Used to steer the boat on upwind courses. Starboard telltail placed a telltail length above the port telltail. These are the singlemost important steering and trim indicators.

Wool strings - or spinnaker cloth strings - placed on the aft edge (leech) of the mainsail. These are used to trim the mainsail. There are typically 2 to 5 of these placed on the leech with regularity. The windfow at the top of the sail is different from the windflow at the bottom, so having just one leechtail isn't enough.

Sometimes there are leechtails in the jib too. For trimming purposes.

Velocity made good. Sometimes the direct route to a mark isn't the fastest way to get there. Sometimes the boat sails faster at a slightly different angle, and if the speedgain is bigger than the "angle-loss" that means the VMG is better even though the angle is worse. Experienced sailors develop some kind of instinct for this. The rest of us will need to buy an instrument that calculates and displays the VMG.

Even with no sails up, the wind causes a boat to move with the wind. With the sails up the drift becomes stronger, and when the boat heels over so that the effective keel area becomes smaller, the drift increases.

The effect from the keel traveling through water at an angle. Effectively the keel does not move straight through the water. Due to the windpressure there is often a sideways drift. The sideways movement creates an angle on the keel, and that makes the waterflow over the keel generate a lift that moves the boat upwind.

Having the current on the leeward side of the keel.

The arrow atop the mast showing the wind direction.

The angle at which the mast heels aftward.

Support the mast in the sailing direction. The headstay is the foremost stay, typically going from the foremost point of the hull to the top of the mast. A forestay is a stay at the front end of the boat but behind the headstay. The backstay sits opposite the headstay. From the top of the mast to the stern.

Running backstays
The running backstays sit opposite the forestay, i.e. not at the top of the mast. They terminate on the aft side of the boat, so there are two of these. They are adjustable while sailing, and the leeward running backstay is loose, while the windward running backstay is not. There can be more sets of running backstays and they are given names such as checkstays and baby stays.

Support the mast in the sideways direction. Typically there are two or more on each side. The upper or outer shroud is called the cap shroud. The inner one is just a shroud. The inner shroud terminates where the spreaders attach to the mast.

Two small "booms" horizontally going out from the center of the mast in a 90 degree angle from the sailing direction, - sometimes more. They hold the cap shrouds out from the mast. If there are only one set of spreaders they'd typically be places around the middle of the mast. There can be 2, 3 4 or more sets of spreaders on larger boats. It's a mess to trim.

Easy: The line used to trim the sailangle.

Sheet traveller
Less obvious to landlubbers: It is device used to move the angle of attack of the sheet. It changes the direction in which the sail is pulled by the sheet. The main sheet traveller moves sideways. The jib sheet traveller moves along the sailing direction.

Sailing upwind.

Wind from the side.

Wind from aft.

Sailing closer to the wind.

Bearing away
Changing course away from the wind.

Changing course from having wind on one side to having the wind come straight at you to having the wind on the other side. (Of you and your boat).

Changing course by steering away from the wind till it is at your back and then continuing to sail closer to the wind till the wind is on the other side. (Of you and your boat).

A hefty heel over to leeward of more than 60 degrees typically with a total loss of control since the rudder is out of the water.

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