| Carlos Serodio: I made my spades long ago (see newsletter 26-17) and they almost canceled the adverse yaw "feature" of my BD4. After telling Roger about them he decided to make himself similar spades as well. He didn't get as much improvement as I did from his. Mine and his are the only BD4 fliers that I saw that have got spades. There is at least one more (see newsletter 26-17) but I don't know about his experience with his design. I later discussed this issue personally with Roger at Oshkosh and we concluded that 2 factors were contributing to the bigger effectiveness of my spades: mine is a stretched fuselage and my spades progressively opose the wind flow in a more frontal manner. Certainly the effectiveness of a spade of the type I designed comes from the size of its frontal area i.e. the bigger its arm the more of its frontal face will outstand from the wing tip. My design also aimed at avoiding the risk of aileron snatch. That is why the effect comes purely from the frontal surface of the spade. I attach some photos. Please note the photo "fullspade". It is looking to the spade as the wind flow will see it with fully deflected aileron. There is no gap between the spade and the wingtip skin from which snatch forces could be created. |
  
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The following are pictures from Steve Craigle's solution. He uses a simple steel plate welded to a rod. He eliminates the need for lead with a greater lever. Another advantage of this system is that the lower skin only has a thin slot. Simple, easy and very effective.
 The aileron is up, so the counterweight goes down. |
 The other side... |
 View from the front (I'm standing at the leading edge). That's how the air "sees" it |