3 ms·

While I'm not a naval architect, but your comment is nice reminder that naval hull drag is cubic with speed: For reference, see this document [1] from the US N

While I'm not a naval architect, but your comment is nice reminder that naval hull drag is cubic with speed: For reference, see this document [1] from the US Naval Acadamy. "It will be observed from the figure that the doubling of speed of the Navy YP from 7to 14 knots increases the power by a factor of 10!" [1] p.7 "Ship power is roughly proportional to the cube of the speed" [1] p.8 Hence the installed power you estimate may just work out. I do have many questions about the about sail handling and rigging. Stowed and raising these things are non-trivial! Telescopic mechanisms can have all sorts of issues, especially when loaded - like in a building storm! So while the entire concept really excites me, I'd love to see them iterate at smaller scale before trying to go full scale. [1] Chapter 7, RESISTANCE AND POWERING OF SHIPS U.S. Naval Academy: https://www.usna.edu/NAOE/_files/documents/Courses/EN400/02.07%20Chapter%207.pdf https://www.usna.edu/NAOE/_files/documents/Courses/EN400/02....

jasonwatkinspdx 6y ago
> "I do have many questions about the about sail handling and rigging. Stowed and raising these things are non-trivial! Telescopic mechanisms can have all sorts of issues, especially when loaded - like in a building storm!" I had some downtime while living on a marina for a bit, so I read a bunch of the research literature. Freestanding wingsails that can fully rotate like this have the neat property that they can "weathervane" with very little drag. In fact a bare mast on a traditional sailboat with the sail down generates a lot more drag than the wing, due to turbulence vs laminar flow. It's not clear from these renders, and I'm not motivated enough to dig into it, but most designs I read about in this category are self trimming. Saildrone is a good example, where it uses a 2nd smaller wing on a boom to control the overall angle of attack of the wing. Change the setting on the "tail" to change the angle of attack. The wing will follow the direction of the wind no matter how it shifts. So controlling these boils down to a small electric actuator, which is easy to make controllable via a screen, software, or what have you. In fact one of the motivations for people experimenting with this stuff at more modest scale is it could be huge for adaptive sailors, because it makes sail handling so trivial.

jasonwatkinspdx 6y ago

> "I do have many questions about the about sail handling and rigging. Stowed and raising these things are non-trivial! Telescopic mechanisms can have all sorts of issues, especially when loaded - like in a building storm!" I had some downtime while living on a marina for a bit, so I read a bunch of the research literature. Freestanding wingsails that can fully rotate like this have the neat property that they can "weathervane" with very little drag. In fact a bare mast on a traditional sailboat with the sail down generates a lot more drag than the wing, due to turbulence vs laminar flow. It's not clear from these renders, and I'm not motivated enough to dig into it, but most designs I read about in this category are self trimming. Saildrone is a good example, where it uses a 2nd smaller wing on a boom to control the overall angle of attack of the wing. Change the setting on the "tail" to change the angle of attack. The wing will follow the direction of the wind no matter how it shifts. So controlling these boils down to a small electric actuator, which is easy to make controllable via a screen, software, or what have you. In fact one of the motivations for people experimenting with this stuff at more modest scale is it could be huge for adaptive sailors, because it makes sail handling so trivial.