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Why does the Blackbird use a propeller, why not a simple high-performance land sail boat like the Greenbird, a design that fits with the original idea from the

Why does the Blackbird use a propeller, why not a simple high-performance land sail boat like the Greenbird, a design that fits with the original idea from the sailing community? There is nothing online that says a sail boat can go DDWFTTW. DDWFTTW is at least a 4 decades old term in the sailing community looking at magazines. Here's a design from 1985 using a propeller https://issuu.com/latitude38/docs/latitude3894apunse/162 https://issuu.com/latitude38/docs/latitude3894apunse/162 Sorry, you are mistaken.

cblconfederate 5y ago
the sails on those sailboats act like a wing even downwind . That's only usable with racing boats which use light foils fly over water instead of heavy keels , but yes they can move faster than the wind . Curiously i can't find a good explanation of their design. The Blackbird cannot use a land sail to go faster because it needs something to act like the keel on a sailboat and provide a counterforce. The propeller is an elaborate way to provide that force
- aaron695 5y ago
  You are agreeing current sail boats can go DDWFTTW which is directly downwind not a degree either way, faster than the wind, for a indefinite period of time? Tacking is not allowed, since that's not directly downwind. This should also mean going directly upwind is practically possible, not a degree either way, directly upwind for a indefinite period of time with sails. Do you have a link for this? Here's a link to a working directly upwind rotary sail boat model - https://www.youtube.com/watch?v=j1bR5hb8RCQ https://www.youtube.com/watch?v=j1bR5hb8RCQ
  - cblconfederate 5y ago
    I dont know much about sailboats but i think they mean this: https://en.wikipedia.org/wiki/Wingsail https://en.wikipedia.org/wiki/Wingsail . when they are at a slight angle and in combination with lightweight foils pointing the other way it seems they are able to go faster than wind in any direction, without anything like a propeller. In any case i think talking mixing wings, sailboats and propellers makes it confusing to understand what the blackbird does
    - aaron695 5y ago
      You can't go DDWFTTW with sails. No one has gone DDWFTTW on water. It will take a propeller to do when it happens. If you want to contradict this you need to post a link of someone agreeing with you, else you misunderstand DDWFTTW. (The link on Wingsail leaves out 0 and 180 degrees for the Points of Sail which are the only two we care about, directly downwind and directly upwind, the wiki article makes no comment on DDWFTTW. This thread is just people saying random words like AC72 or broad reach. If your ideas correct someone else will sum it up for you and you can link it. )
      - cblconfederate 5y ago
        There some speed graphs like this online: https://www.catsailingnews.com/2013/07/ac72-polars-penalties.html https://www.catsailingnews.com/2013/07/ac72-polars-penalties... I think what you re saying is that you can't be at 0 degrees to the wind, which i guess is true

cblconfederate 5y ago

the sails on those sailboats act like a wing even downwind . That's only usable with racing boats which use light foils fly over water instead of heavy keels , but yes they can move faster than the wind . Curiously i can't find a good explanation of their design. The Blackbird cannot use a land sail to go faster because it needs something to act like the keel on a sailboat and provide a counterforce. The propeller is an elaborate way to provide that force

aaron695 5y ago
You are agreeing current sail boats can go DDWFTTW which is directly downwind not a degree either way, faster than the wind, for a indefinite period of time? Tacking is not allowed, since that's not directly downwind. This should also mean going directly upwind is practically possible, not a degree either way, directly upwind for a indefinite period of time with sails. Do you have a link for this? Here's a link to a working directly upwind rotary sail boat model - https://www.youtube.com/watch?v=j1bR5hb8RCQ https://www.youtube.com/watch?v=j1bR5hb8RCQ
- cblconfederate 5y ago
  I dont know much about sailboats but i think they mean this: https://en.wikipedia.org/wiki/Wingsail https://en.wikipedia.org/wiki/Wingsail . when they are at a slight angle and in combination with lightweight foils pointing the other way it seems they are able to go faster than wind in any direction, without anything like a propeller. In any case i think talking mixing wings, sailboats and propellers makes it confusing to understand what the blackbird does
  - aaron695 5y ago
    You can't go DDWFTTW with sails. No one has gone DDWFTTW on water. It will take a propeller to do when it happens. If you want to contradict this you need to post a link of someone agreeing with you, else you misunderstand DDWFTTW. (The link on Wingsail leaves out 0 and 180 degrees for the Points of Sail which are the only two we care about, directly downwind and directly upwind, the wiki article makes no comment on DDWFTTW. This thread is just people saying random words like AC72 or broad reach. If your ideas correct someone else will sum it up for you and you can link it. )
    - cblconfederate 5y ago
      There some speed graphs like this online: https://www.catsailingnews.com/2013/07/ac72-polars-penalties.html https://www.catsailingnews.com/2013/07/ac72-polars-penalties... I think what you re saying is that you can't be at 0 degrees to the wind, which i guess is true