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      CommentAuthorAngus
    • CommentTimeNov 27th 2018 edited
     
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      CommentAuthorAngus
    • CommentTimeNov 27th 2018
     
    I guess this does require a little explanation. The CEO of Artemis explains that the boat will do 30 kt in a 10kt breeze, which doesn't sound unreasonable for a foiling cat. He then points out that if you put it in a river in still air, the river flowing at 10 mph (notionally - pretty fast for an actual river), then the boat will see a breeze of 10 kt in the upstream direction from its drift. It can thus sail at roughly 30-10 = 20 kt upstream, give or take small factors for angle.

    What do we think?
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      CommentAuthorDuracell
    • CommentTimeNov 27th 2018
     
    Yes. Counterintuitive, but yes, I think he is right.
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      CommentAuthorAngus
    • CommentTimeNov 27th 2018
     
    1 for yes.
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    When it sails up the mighty Sacramento, I'll believe it.
    • CommentAuthorAsterix
    • CommentTimeNov 27th 2018
     
    Isn't it mostly a matter of conservation of momentum, not speed?
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      CommentAuthorAngus
    • CommentTimeNov 28th 2018
     
    @ Asterix : It's not much to do with either. It has to do with forces.
    @ Al : The mighty Sacramento is currently flowing at about half a mile per hour (didja notice that one?) according to the US Geological Survey National Water Information website. Too slow to work. The Amazon floods at 7 km/hr, which is closer to sailing speeds. Seymour Narrows up the road from here runs at 15 kt during the change of tides. That would work. If the idea works.
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      CommentAuthoroak
    • CommentTimeNov 28th 2018
     
    Posted By: AngusI guess this does require a little explanation. The CEO of Artemis explains that the boat will do 30 kt in a 10kt breeze, which doesn't sound unreasonable for a foiling cat. He then points out that if you put it in a river in still air, the river flowing at 10 mph (notionally - pretty fast for an actual river), then the boat will see a breeze of 10 kt in the upstream direction from its drift. It can thus sail at roughly 30-10 = 20 kt upstream, give or take small factors for angle.

    What do we think?

    While I know it's possible to sail roughly upwind (e.g. 30 degrees off directly upwind), how would you sail directly upwind (e.g. in the direction you are drifting on a river in still air)? I'm not understanding something about this boat.
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      CommentAuthoroak
    • CommentTimeNov 28th 2018
     
    Never mind. "Upstream." So maybe . . .
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      CommentAuthorAngus
    • CommentTimeNov 28th 2018 edited
     
    That would be about 30 degrees to the apparent wind. But these foiling cats can exceed the wind speed quite easily. So the true course will be quite different from 30 degrees off the true wind. Interesting problem, isn't it?
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      CommentAuthoraber0der
    • CommentTimeNov 28th 2018
     
    Posted By: AngusWhat do we think?


    I don't know.
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    Do we think?

    Or is it the other way round?
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      CommentAuthoroak
    • CommentTimeNov 28th 2018 edited
     
    Posted By: AngusThat would be about 30 degrees to theapparentwind. But these foiling cats can exceed the wind speed quite easily. So the true course will be quite different from 30 degrees off the true wind. Interesting problem, isn't it?

    Yes, but if the boat is drifting downstream, but sailing upstream, the "wind" resulting from the drift is coming from directly behind the boat. So now I'm not clear on how the true or apparent wind affects the analysis (assuming "still air" on the river).

    The boat is sailing upstream, but directly downwind (its apparent wind).
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      CommentAuthoraber0der
    • CommentTimeNov 28th 2018 edited
     
    Let's just wait until YAAFP chimes in and tells it like it is.
  3.  
    Posted By: AngusI guess this does require a little explanation. The CEO of Artemis explains that the boat will do 30 kt in a 10kt breeze, which doesn't sound unreasonable for a foiling cat. He then points out that if you put it in a river in still air, the river flowing at 10 mph (notionally - pretty fast for an actual river), then the boat will see a breeze of 10 kt in the upstream direction from its drift. It can thus sail at roughly 30-10 = 20 kt upstream, give or take small factors for angle.

    What do we think?
    Sounds perfectly fine.
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      CommentAuthorAngus
    • CommentTimeNov 28th 2018
     
    Last active August 2018??
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      CommentAuthorAngus
    • CommentTimeNov 28th 2018
     
    For the record, I say yes. But it might be damn tricky to do.