Why even use Unity if this exists? Why even install an app if you could feasibly run a full-blown game with 3D physics in the browser on your iPhone at 60 FPS? Where in the world are all the browser-based games?
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
Definitely recommend taking an introductory ASA 101/102/103 classes from a local school! Will help you decide if you are into it while having some fun.
I built one recently to mostly help myself visualize how sail trim worked and how various boat controls like mainsheet and backstay affected sail shapes, various forces and boat performance. It uses a physics-based VPP and I calibrated it against Catalina 36 polar charts, so should be pretty precise!
I plan to integrate the simulator with the sail trim guide I'm building to help people learn.
There is a great school called Modern Sailing School in Sausalito. I highly recommend taking a class from them. I took one in the past and they are great!
Will help you figure out if you are into sailing or not.
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!
What are you using for your physics engine, or how did you go about designing your aero model? I've been poking about with wing aero for a toy flight simulator and there's not a lot written about the design process of modeling this stuff in near-real time.
I cheated a little bit and don't calculate the fluid dynamics in real time. Instead, I'm using force models from the excellent Aero-Hydrodynamics of Sailing book by Marchaj, which is sadly out of print. I then do iterative balancing of the drag force and combined drag/lift forces on sails until they converge.
Little confused. So you're mostly giving credit to a demo that then inspired your own demo?
Either way, both demos are fairly interesting, especially since there's so little exploration of sailing and the physics involved most of the time.
The second sailrhythm demo seems rather high quality and a better representation of the physics involved. Not sure if you're planning to work on it further, yet putting the rudder heading up near the top would be helpful, maybe with a circular dial you can select like the compass or broad reach displays. Kinda weird when the boat flips completely around to head left.
Some kind of visual representation on the Boom Vang, Cunningham, Outhaul, Backstay, and Jib Lead would also be helpful, since it's really difficult to tell if they're actually doing anything. Maybe a transparent deformation magnified overlay showing the sail profile surface deformation extended away from the actual sail in extreme distortion. Otherwise the changes are so minute its challenging to perceive.
Otherwise, it's a cool demo, and seems to be (from a not especially experienced sailor) relatively realistic of the forces involved. Suggested extension would be showing the wind flowing off the sails and how the forces transition. Also, showing other boats, particularly something complicated like a Windjammer [1], Full-Rigged Ship [2] or Schooner [3] varieties.
Also cool, simply because so few submissions seem to deal with sailing, boats, and generally water transport principles. Lots of possible VC ideas related to sails and sailboats. MarineTraffic [4] is currently tracking 300,000 ships out on the world oceans, and surprisingly small number use any form of sail based propulsion. Route planning and "this much cargo to this area with this speed of delivery" estimation relative to money spent on oil and fuel for a normal ship would likely be possible. From this Quora answer (suggested by Google) a small container ship (something with 15000 kW, 2000-3000 TEU capacity, maybe a Feedermax ship) might use 2000 tons of fuel crossing the Pacific (maybe $500,000 to $1,000,000 of fuel) [5]. This paper [6] has a much more complicated breakdown if you're interested in those types of calculations.
Also quite a bit with drones, and automated sailing. [7][8] Even a decent amount with land propulsion [9] that's been explored occasionally and there's even a tiny amount with space probes and planetary rovers as concepts [10].
SailRhythm is a bit WIP, so didn't want to share too early!
Thank you so much for the detailed feedback. I do have plans to implement wind flow visualization and have a way to visualize forces as well. Controls a bit tricky to do, but this is definitely something I've been pondering. As you said, at certain headings the changes sometimes are too small to perceive.
You're welcome on the feedback, and mostly just suggestions from trying the product / demo. Cool generally that somebody's actually investigating sailing.
Another thought of (if there's actually further interest in this kind of software) would be middleware like SpeedTree (https://en.wikipedia.org/wiki/SpeedTree). Seems like sailing games have been pretty popular lately (Sea of Thieves (40m player base), Assassin Creed IV (15m)) so there's probably at least some market for modestly priced middleware that handles sailing physics.
This site is an absolute treasure trove of technical material on sail and hull design, with a focus on model yachts but most of the physics scales up. It covers aerofoil theory (momentum, circulation, lifting line), sail twist, downwash, planform effects, Reynolds number, hull resistance, appendage design, VMG, and more.
Lots of spreadsheets and practical calculators too—bulb shape optimization, wetted surface area, simple VPP models. If you're into sail performance modeling or yacht design, this is one of the best resources out there.
Nice to see an enthusiast/engineering site that is putting cutting egde design ideas into the public domain.
Grew up with boat builders on the south shore of Nova Scotia, and knew and learned from some of the
last people to build and crew working schooners, that were also raced, I a boy, and they proud old men. Also know current builders and restorers of blue water boats.
A few years ago I stumbled onto footage of a big hydrofoil cat that was the first boat to break the 50 knot barrier, you could tell that any celebrating was waiting and would largely be to celebrate still bieng alive, big seas, 50+kn, and quite clearly nothing but flinders left if anything broke and they plowed into a wave.,..,........they were standing on deck
I prefer these days, when the absolute amount of information like this is higher, even if there's also higher amounts of junk.
I can just not look at the junk today, compared to 25 years ago when the information I wanted only existed in a physical library in a different country.
Even still a lot of information is not online. I've been building a web sail trim simulator and had to hunt down a physical copy of the Aero-Hydrodynamics of Sailing book by Marchaj, because a lot of the formulas and models I needed to simulate the boat were not online, and what was online was often wrong.
