stass (u/stass) - Readit News

stass commented on Sail-Trim Simulator simulator.atterwind.info/... · Posted by u/stass

hadlock · 8 months ago

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.

stass · 8 months ago

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.

stass commented on Sail-Trim Simulator simulator.atterwind.info/... · Posted by u/stass

araes · 8 months ago

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].

[1] https://en.wikipedia.org/wiki/Windjammer

[2] https://en.wikipedia.org/wiki/Full-rigged_ship

[3] https://en.wikipedia.org/wiki/Schooner

[4] https://www.marinetraffic.com

[5] https://www.quora.com/How-much-does-it-cost-to-fuel-a-cargo-...

[6] https://www.man-es.com/docs/default-source/document-sync/pro...

[7] https://en.wikipedia.org/wiki/Unmanned_surface_vehicle

[8] https://www.saildrone.com/

[9] https://en.wikipedia.org/wiki/Land_sailing

[10] https://en.wikipedia.org/wiki/Zephyr_(rover)

stass · 8 months ago

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.

stass commented on Sail-Trim Simulator simulator.atterwind.info/... · Posted by u/stass

867-5309 · 8 months ago

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

stass · 8 months ago

You get water graphics for free from three.js

stass commented on Sail-Trim Simulator simulator.atterwind.info/... · Posted by u/stass

stass · 8 months ago

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

stass commented on How a yacht works: sailboat physics and design onemetre.net/Design/Desig... · Posted by u/stass

McNutty · 8 months ago

Bring back more of this type of internet content!

stass · 8 months ago

Please!

stass commented on How a yacht works: sailboat physics and design onemetre.net/Design/Desig... · Posted by u/stass

Zeetah · 8 months ago

I know nothing about sailing. I've been on a few sailboats. I love the idea of wind power - probably why I like flying remote control sailplanes.

I would love to volunteer on someone's race/sail boat to get some experience. I'm happy to take the ASA introductory course or ? course.

Any advice on how to move forward? I'm in the Seattle area.

stass · 8 months ago

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.

This is how I started.

stass commented on How a yacht works: sailboat physics and design onemetre.net/Design/Desig... · Posted by u/stass

amelius · 8 months ago

I'd love to have a simulator for a sailboat, preferably running in a browser.

stass · 8 months ago

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.

It's a WIP, but accessible at https://www.sailrhythm.com/

Happy to answer any questions!

stass commented on How a yacht works: sailboat physics and design onemetre.net/Design/Desig... · Posted by u/stass

lasermatts · 8 months ago

I've been super interested in sailing since moving to San Francisco and running around the marinas/Embarcadero.

Did some digging and found a sailing school that I haven't asked about classes (yet) https://www.spinnaker-sailing.com

There's even a school that offers boatbuilding lessons in Sausalito -- a bit too far/much of a time commitment for me! https://www.spauldingcenter.org/current-offerings

stass · 8 months ago

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.

stass commented on Sail-Trim Simulator simulator.atterwind.info/... · Posted by u/stass

quaestio · 8 months ago

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?

stass · 8 months ago

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!