af2008

Comment Threads

• dny commented on Directly downwind faster than the wind - part 3
  Re: Three questions for cart enthusiasts: Couldn't you just block the wind coming from the front and making the fan turn backwards? Then it would cease to be a factor. Here's an amateurish diagram I drew of what I'm talking about. The wind shield would have to be bigger, so it could cover the entire front of the fan and direct the air from the back down. This would have the added advantage of acting as both a sail from the back and a wing/needle from the front....
• tomtheblacksmith commented on Downwind faster than the wind, part 2
  Chris, This is a good description, and I will reply with my thoughts. The computer was gone for a couple of days, but I'll be back soon. Thanks for writing. Tom the Blacksmith...
• davefoc commented on Directly downwind faster than the wind - part 3
  Hi folks, there has been a long discussion going on at the JREF forum about this. Personally, I have almost zero doubt that it is possible and that it has been demonstrated. There is a fairly simple plausible explanation available. My cut at that: Energy can be recovered by extracting it from the rotation of the axle driven by the wheels. In the normal situation this will slow the card down to something less than the wind speed when energy is extracted from the rotation of the axle. However that available energy can be used to spin a propeller to...
• zerocarbonista commented on Downwind faster than the wind, part 2
  "Charles Platt made a miniature model of the vehicle and came to the conclusion that there is no such thing as a wind-powered vehicle that can travel faster than the speed of the wind." No propellers involved, but the Greenbird craft travels downwind faster than the speed of the wind. It is currently on Canyon Ferry in Montana about to attempt the Ice Speed Record. There is also a land version of the craft that was in Australia this year. Check out the site/blog. Greenbird is also on Twitter....
• ian9toes commented on Directly downwind faster than the wind - part 3
  This would have to come down to the efficiency of the propeller versus the drag of the wheels and bearings and pulley etcetera. So my comment is only on how to increase that efficiency. I'm talking about the cart with the big swivelling funnel and the exhaust leading out the back. What about having the exhaust go straight down, so when there is relative tail wind no wind can go up the exhaust and turn the prop the wrong way. In actual fact no wind would ever go up the exhaust as the swiveling top section is greater than the...