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Recent content by Marc Zeitlin

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  1. Marc Zeitlin

    Sampling Light Aircraft Crashes

    It's funny - as someone who works with moldless composite construction airplanes every day, I feel the same way about AL planes - who knows where corrosion is hiding - there are a zillion places on an RV that you can't see with an inspection mirror :-). In any case, while there have been a few...
  2. Marc Zeitlin

    10/23 Raptor Video

    And it does. I've got a crude and introductory presentation on Canard Aerodynamics here: http://cozybuilders.org/Oshkosh_Presentations/2019_Columbia-Canard_Aero.pdf and on page 20, I discuss the downwash issue. Note that all of the graphics were stolen from the references shown on Page 33...
  3. Marc Zeitlin

    10/23 Raptor Video

    Good question. On the canards with the GU and/or Roncz airfoils, the aircraft (theoretically) trims itself to about 125 KIAS. A couple of folks have tested this on purpose and they do seem to have found that the self-trim IAS is somewhere in the 110 - 140 KIAS range. So that's where OUR canard...
  4. Marc Zeitlin

    10/23 Raptor Video

    Most, and possibly all, yes. The VariViggen's elevator hinge line was pretty far below the bottom surface of the canard/elevators, so there was substantial area increase with TE down motion there as well, but the planes seemed to have flown decently. So could this make the pitch sensitivity...
  5. Marc Zeitlin

    10/23 Raptor Video

    Both the GU and Roncz canard elevators used on Rutan derivative canard aircraft are also effectively slotted flaps, and the slot shape and elevator position are important to the functionality and hinge moments. In the interest of speed, Klaus Savier has a highly modified Roncz canard without a...
  6. Marc Zeitlin

    10/23 Raptor Video

    A cursory review of the first flight video disproves that theory. Raptor lifted off the runway at almost exactly 100 KIAS - clearly the canard was not stalled at that point (see 10:30 or so into the video). The rest of the flight was performed at approximately 105 - 118 KIAS - faster than...
  7. Marc Zeitlin

    10/23 Raptor Video

    Probably not, given just a few inches of difference, and the size of the canard tip vortex. I'd be surprise if that was a factor - just a few inches. See: http://www.pilotfriend.freeola.com/training/flight_training/aero/wng_vort.htm specifically the sentence that reads: "For an observer fixed...
  8. Marc Zeitlin

    10/23 Raptor Video

    Sure - could be - just never had it in any of the canards I've flown that are similar in waterline position of canard and wing to the Raptor, and my comment was with respect to Mr. Andreen's certainty regarding the canard tip vortices being the cause of whatever it is we're seeing.
  9. Marc Zeitlin

    10/23 Raptor Video

    I do not know who Mr. Andreen is or what his background or experience with Rutan derivative canard aircraft might be - canards on short coupled delta wing aircraft may have very different characteristics than the canard aircraft we're discussing. But I can say this - the relationship (wrt...
  10. Marc Zeitlin

    10/23 Raptor Video

    Just what you'd expect. Extremely crappy performance. But we actually have no idea what the power output is, nor what the issues with the flight were, nor whether what we're seeing is poor pilot technique, or..., or... Since 175 HP wouldn't allow the plane to accelerate the way the videos have...
  11. Marc Zeitlin

    10/23 Raptor Video

    COULD you? Sure - if Starship could have a swinging canard, you COULD do anything. As you say, a structural and control system nightmare, though. Far easier to just determine the correct CG range for the airplane after a thorough design process that takes deep stall analysis into account, and...
  12. Marc Zeitlin

    10/23 Raptor Video

    Take an awful lot of runway to get off the ground, even at SL on a standard day, assuming it could do so, and then climb like crap and fly slowly. But I have about 100 ft^2 of wing, and the Raptor has a lot more, so the wing loading is approximately the same. And I have a 180 HP engine, so at...
  13. Marc Zeitlin

    10/23 Raptor Video

    if the plane is designed correctly, then as long as you are in the approved CG range, a deep stall can not occur. But the answer is GENERALLY no - if you get into a deep stall, it’s a VERY stable condition and pitch, roll and power do almost nothing to get out of it. My hangar mate, Mike...
  14. Marc Zeitlin

    10/23 Raptor Video

    That seems a bit low - I’d expect the XL to be about the same as the COZY. I’d be interested to see the Phase 1 glide test data for your plane. Plus, I should go back and look at mine to make sure I’m not misremembering 😀
  15. Marc Zeitlin

    10/23 Raptor Video

    I don't remember exactly what the wing loading was on the Raptor - I think it was somewhere in the 20 lb/ft^2 range, which was approximately similar to the COZY MKIV at MGW. My COZY best glide speed is about 80 - 85 KIAS, although the curve is actually pretty flat between 80 - 90 KIAS, so it's...
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