Here is a fun sailboat race simulator. It's very simple, but pretty realistic especially for open ocean racing. You can use their default race course, sometimes join a planned regatta, or make your own. (It was great during COVID, to try racing across the oceans, or around the world. It's in real time, so you might not need to change anything for days If you are in the trade winds, and open ocean, but then when you get closer to land, things get "Western" very quickly - just like with a real boat.
It's called SailNavSim. (Learned about it from HN.)
Eventually it made sense that boat-speed only changes the "apparent wind", as it's only simulating wind-boat interactions, not water-boat interactions.
One of the most mind bending facts I tell people, even sailors, is that sailboats are not limited to sailing at the true windspeed. Sails are wings, not bags. In fact, a boat's top speed is directly dictated by its ability to point into the wind (assuming, for example, the boat is not physically limited by it's displacement hull speed, as in the case of hydrofoils). The consequences of this simple truth are manifest.
First, consider the edge case where the sail is acting as a bag when you're sailing downwind. As the boatspeed approaches the true windspeed, the apparent windspeed falls to 0 and the sail will luff. In this specific case, the boat can not go faster than the wind.
Now consider the boat cutting across the wind at a 90 angle. When the boat starts moving, the wind comes 90 degrees off the bow. As the boat increases speed, the apparent wind shifts closer to the bow. Apparent wind is just vector addition of true wind and boat wind. If the boat achieves the same speed as the true wind, then the apparent wind is sqrt(2) ~ 1.4x faster than the true wind. More wind means more power, so with that additional wind, it can go faster. Continuing the example, as the apparent wind increases, it appears closer and closer to the bow. Eventually the sail will stall and produce less lift. This is the point where the boat will go no faster.
The slowest point of sail is directly downwind. In a race, it is often much faster to gybe back and forth rather than ever go directly downwind. When a boat goes directly downwind, their boat speed cancels out the true wind. In the strangest case, if a high performance boat going faster than the speed of wind (say, on a broadreach) goes directly downwind, the apparent wind will appear to be coming head on. They've effectively gone 'into irons', yet they're facing 180 degrees off true wind.
If you ever get the chance, you should see the SailGP boats race. Their sails are almost always hauled fully in, even downwind. The other thing is that they gybe downwind because to go directly downwind would be to stall. In effect, these boats can achieve multiple times the true wind speed, but so long as they aren't pointed directly into, nor directly away from the wind.
Into the irons/in irons being a dead sailing area, where boat is head on into the wind (wind's eye). A lot of people get surprised that you can sail upwind as well.
If other people are interested in sailboat physics -- this resource is a goldmine of information on how sailboat and sails work and physics around it: https://www.onemetre.net/Design/Design.htm
Most yachts have polar charts, and the speed is a function of sail area, heading, wind speed and direction amongst other things. Are you considering calculating estimated boat speed based on given conditions and controllable variables?
Not my demo! But I got inspired by it some time ago to build a simulator for monohulls which uses a physics based VPP to calculate the boat speed based on input controls like mainsheet, jib sheet, travelers, backstay and so on at https://www.sailrhythm.com/
It uses Catalina 36 Tall Rig as a base model for sailboat parameters and was calibrated to match ORC-published polars for it within 1-5% on both close, beam and broad reaches.
Mostly built it for myself to help me understand how less common control affect the sail shapes, angles of attack and boat heel and behavior in a visual way.
It's still WIP, but you might find it useful for yacht-specific stuff!
The blue cones are probably the wind coming to the boat but there is a wall of cones a little further away, visible by zooming out. Those cones don't have the same directions of the ones close to the boat. It's probably apparent wind (close to the boat) and real wind (further away.) It would help to start with a zoom level with both winds visible.
The biggest problem that is puzzling everybody is that speed never changes. I eventually decided that this is because the app calculates the setup of the mainsail to get the desired boat heading and speed given the wind. If you keep the heading constant and change the boat speed you see that the sail rotates around the mast.
It's the opposite of what we do when sailing: we set the sail to a shape and direction (let me use these terms) to go somewhere. In this simulator we do it backwards and adjust the wind to get the sail into a shape and direction.
I am still learning and would love to use this, so I can validate my thoughts :D
What would be great:
- change model. I sail mono hull and would love to have
- like others stated. Som kind of indicator that we are moving
- or clouds
I like the idea but I don't get this at all. Shouldn't the speed change based on the mainsail trim relative to the heading? I pointed the boat dead downwind, eased the mainsail all the way out and the speed is 0 kn. I can't even see the value for the trim, just speed, but you get speed from correctly trimmed sails.
It would be great if it would be able to limit the max speed based on the heading, right now the slider allows the same max speed for any heading. On this boats I suspect max speed is achieved going on a beam reach (90 degrees to the wind)
pomian|10 months ago
8bitbyte.ca
philips|10 months ago
MOARDONGZPLZ|10 months ago
reaperman|10 months ago
derbOac|10 months ago
api_or_ipa|10 months ago
First, consider the edge case where the sail is acting as a bag when you're sailing downwind. As the boatspeed approaches the true windspeed, the apparent windspeed falls to 0 and the sail will luff. In this specific case, the boat can not go faster than the wind.
Now consider the boat cutting across the wind at a 90 angle. When the boat starts moving, the wind comes 90 degrees off the bow. As the boat increases speed, the apparent wind shifts closer to the bow. Apparent wind is just vector addition of true wind and boat wind. If the boat achieves the same speed as the true wind, then the apparent wind is sqrt(2) ~ 1.4x faster than the true wind. More wind means more power, so with that additional wind, it can go faster. Continuing the example, as the apparent wind increases, it appears closer and closer to the bow. Eventually the sail will stall and produce less lift. This is the point where the boat will go no faster.
The slowest point of sail is directly downwind. In a race, it is often much faster to gybe back and forth rather than ever go directly downwind. When a boat goes directly downwind, their boat speed cancels out the true wind. In the strangest case, if a high performance boat going faster than the speed of wind (say, on a broadreach) goes directly downwind, the apparent wind will appear to be coming head on. They've effectively gone 'into irons', yet they're facing 180 degrees off true wind.
If you ever get the chance, you should see the SailGP boats race. Their sails are almost always hauled fully in, even downwind. The other thing is that they gybe downwind because to go directly downwind would be to stall. In effect, these boats can achieve multiple times the true wind speed, but so long as they aren't pointed directly into, nor directly away from the wind.
frainfreeze|10 months ago
cladopa|10 months ago
stass|10 months ago
m_herrlich|10 months ago
quaestio|10 months ago
Most yachts have polar charts, and the speed is a function of sail area, heading, wind speed and direction amongst other things. Are you considering calculating estimated boat speed based on given conditions and controllable variables?
stass|10 months ago
It uses Catalina 36 Tall Rig as a base model for sailboat parameters and was calibrated to match ORC-published polars for it within 1-5% on both close, beam and broad reaches.
Mostly built it for myself to help me understand how less common control affect the sail shapes, angles of attack and boat heel and behavior in a visual way.
It's still WIP, but you might find it useful for yacht-specific stuff!
pmontra|10 months ago
The biggest problem that is puzzling everybody is that speed never changes. I eventually decided that this is because the app calculates the setup of the mainsail to get the desired boat heading and speed given the wind. If you keep the heading constant and change the boat speed you see that the sail rotates around the mast.
It's the opposite of what we do when sailing: we set the sail to a shape and direction (let me use these terms) to go somewhere. In this simulator we do it backwards and adjust the wind to get the sail into a shape and direction.
0xcb0|10 months ago
I am still learning and would love to use this, so I can validate my thoughts :D What would be great: - change model. I sail mono hull and would love to have - like others stated. Som kind of indicator that we are moving - or clouds
gitroom|10 months ago
marktolson|10 months ago
867-5309|10 months ago
stass|10 months ago
inasio|10 months ago
unknown|10 months ago
[deleted]
ge96|10 months ago
zeristor|10 months ago
https://news.ycombinator.com/item?id=43756926
Thank you, you’ve resolved my despair.
unknown|10 months ago
[deleted]