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  1. Norman

    Pushers...way to go ?

    There's your answer then.
  2. Norman

    Pushers...way to go ?

    Do you know of any powered airplane that's lighter than its cargo?
  3. Norman

    Pushers...way to go ?

    Much better. There should be as little stuff in front of the propeller as possible to avoid vibration and power lose due to distorted airflow. If you must have a tail it really should be behind the prop. Tail in front of the prop designs are DUMB. 50 years ago it may not have been so obvious...
  4. Norman

    Pushers...way to go ?

    A cardan shaft uses universal joints to adjust for the misalignment due to the suspension system jumping around. Airplanes don't have nearly as much misalignment unless there's something seriously wrong. The big problem with long propeller shafts is torsional resonance. As I understand it Molt...
  5. Norman

    Achieving The Best Reflexed Airfoils for Flying Wing use in the Small Plane Categories

    OK you asked 2 questions that I can identify within my terribly limited ability to deal with compound questions. Q1: I can not see the reason behind [reflex]? A: It's cruise efficiency. A symmetrical airfoil section has its minimum drag at zero lift. Adding camber moves the point of...
  6. Norman

    Lift theories

    That's all well and good but you can't actually apply Bernoulli's theorem until you have those vectors. Euler's flow function can give you the direction of those at any given point on the streamline but not the scale. Kutta and Joukowski figured out how to assign an appropriate scale. Once...
  7. Norman

    Short video featuring Arup

    Depends on how you define "Arup". Dr Snyder hired an engineer named Raoul Hoffman to refine his ideas into the powered Arups. They parted ways in 1933 and Hoffman moved to Florida where he designed one more low AR plane. The plane in the video is the 1934 Hoffman. It crashed after an...
  8. Norman

    Airfoil selection for a flying plank, how to achieve statical equilibrium?

    Aft swept wings typically have too much spiral stability at low speed which is what causes dutch roll when trying to fly in a straight line slowly. Washout tends to increase the directional stability of a swept wing so it shouldn't be surprising that Horten wings thermald fine. 2 Horten H.IIIs...
  9. Norman

    Fauvel musings

    3 millimeter thick fuselage skins? Not likely.
  10. Norman

    Streamline theory

    Now combine the starting and stopping vortices from the first video with the trailing vortices from the second video and you have a rectangular vortex ring that's getting stretched out by the airplane that's riding the wave at one edge.
  11. Norman

    Streamline theory

    This is not what's meant by "circulation" in the Kutta-Joukowski theorem. The stream function draws pretty pictures that were apparently good enough for boats but don't reflect reality for an airfoil with an angle of attack. The main problem with classical hydrodynamic theory i.e. "the stream...
  12. Norman

    Streamline theory

    Yikes! I suppose it's still good to know the math but it's all been worked into computer codes years ago and all the operator needs to do is look at the curves and decide where and how to tweak those curves. There are lots of programs that allow you to do this, some are even free and open...
  13. Norman

    career Choices

    Historically most mathematicians have been gamers. They do it because it's somehow fun for them. If anything useful comes from their games it's just a happy accident. But boy did some of those turn out to be useful.
  14. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    So you've verified that plywood would work for the skin. Now make two long skinny I-beams of the same proportions. The beams will twist before you get a significant bending load if they're not restrained so you'll have to make a constraint system. In a D-tube the nose ribs and skin are the...
  15. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    I did not say that the BKB-1 was badly designed, I said that the Bekas was. Kasper's "improvements" to the BKB-1 were suggested modifications from the flight test group in Canada, not his original ideas. When Stefan Brochocki heard that Kasper was flying aerobatics in that glider and...
  16. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    It was an auto-tow not an aerotow. He must have released the towline early. Notice the text I highlighted in red. h= 1-2 m
  17. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    L/D~100 in ground effect Structural failure at 4 Gs Not impressive!
  18. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    Kasper exaggerated a lot... one might even say he lied. He also sometimes used inaccurate data to back up his claims. There is no substitute for aspect ratio. Properly designed winglets can improve span efficiency but those fins on the BKB-1 were NOT winglets, they were just drag rudders...
  19. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    Sorry, I'm not really very interested in old sailplanes in general. I only know about these two from studying the Hortens.
  20. Norman

    Could a wooden sailplane beat a fibre glass/carbon sailplane in L/D ?

    Yes the Horten IV had 2 feet greater span than the Darmstadt D-30 but was 100 pounds heavier. They were the two highest performing sailplanes of their day. Was one better than the other? Depends on the mission but this thread asks about materials not missions. Wood is fine for skins but by...
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