I guess I’m not the only person who opened the link from yesterday and didn’t see anything about sailing.

https://news.ycombinator.com/item?id=43756926

Thank you, you’ve resolved my despair.

Very cool demo...

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?

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

I am a lake sailer. And without landmarks or anything it is impossible for me to perceive the boat as moving.

You can set the wind to 0 and the speed somehow stays at 35 knots, I don't know much about sailing but that can't be right

A great project, but it needs some kind of grid movement and rocking, foam or something so you can perceive its movement.

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.)

8bitbyte.ca

why so heavy on the water graphics and light on the sail?

it's hard to tell if you're moving

That wake thing would've totally helped me too, felt weird not seeing any movement. Glad I wasn't the only one who got thrown off.

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.

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)