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Sailor Al.

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About Sailor Al.

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    Sydney, Australia
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  1. Since the very definition of pressure is force per unit area, why is it nonsense to assert that Dynamic pressure (of the wind) times the sail area equals the force on the sail? I learned that in high school before completing my degree in mathematical physics, so please ease back on the derision.
  2. Yes, sorry, I have taken a while to digest your post. Thanks, I hope my comments are relevant.
  3. Maybe I should have done, I wasn't aware of its existence, thanks I'll. have a look. But I did start the thread and hijacking is discourteous.
  4. You guys have hijacked my sailing thread. Can you take your discussion to a gliding forum please?
  5. Hey, let's not lower the tone to insults. My 30+ years implementing terabyte relational databases has taught me that databases are brilliant for storing and manipulating large quantities of data. Spreadsheets are brilliant for presentation of computational work on small data, and yes, you can't beat a graph to assist in the presentation.
  6. Your post was in response to my comment: "Without gravity to hold the atmosphere down there would be no air for them to fly in, so it's a ridiculous proposition." I couldn't see how any answer to your question would add to the discussion, so I chose not to answer it. However, while looking at your question, I thought it worthwhile to make some side observations about your parameters. A standard club glider will have a best L/D speed of around 50 kts, with a glide slope of around 40:1. If your 10,000 ft altitude was also AGL, then in still air at 50 kts, you would be descending a
  7. If his drawing is not right, how can he not be wrong? Please point out to me and the professor of applied mechanics, where it is wrong.
  8. I'm not sure what type you're flying but if you're doing a steady 90 kts in still air, I would suggest your VS indicator is pointing seriously in the down direction and you'll be looking for a landing site pretty soon.
  9. Yes, you are correct: by providing the lift to counteract the aerodynamic side force, a keel, by virtue of its projection below the CLR, does provide a moment arm to increase the heeling moment. However here you are incorrect here: a keel does not produce thrust. The attached diagram, from Fossati's "Aero-hydrodynamics of Sailing Yachts" shows the total hydrodynamic force Fl can be resolved into Lift Pl (from which the keel increases the heeling moment) and Resistance Rl which acts in the opposite direction to thrust, as drag.
  10. Yes, but the glider in the current discussion is in level flight, so the apple isn't falling, and so there's no conversion of potential energy to kinetic energy.
  11. There must be someone out there who remembers enough of their basic physics to remind these gentlemen about the law of Conservation of Energy.
  12. I have already pointed out the fallacy in that statement. Without a change in height there's no potential energy conversion to kinetic energy. I'm done talking to you.
  13. Not true if, by "quite nicely" you mean maintaining height and speed. Gliding 101: In still air you have to trade height for speed.
  14. Without gravity to hold the atmosphere down there would be no air for them to fly in, so it's a ridiculous proposition.
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