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  1. ScaleBirdsPaul

    Small single seat 3 surface concept

    Wow that Rutan design is almost exactly what I had in mind with the 3-surface concept in my avatar. I would have gone with a narrower fore wing for better ground control though, so it wouldn’t be a true tandem 3-surface. I like your concept a lot Wild Bill, definitely striking!
  2. ScaleBirdsPaul

    Sun n Fun 2020

    I’ll be there for the beginning with the ScaleBirds crew, looking forward to meeting new people!
  3. ScaleBirdsPaul

    Odd questions

    Ive been looking into laminar foils more and I’ve had the same question as #1. Jack Lambie’s composite book says that a geometric flaw of only a few .001s of an inch is enough to trip the laminar flow, but that surface roughness is not as much of a factor as shape. It is important to have a...
  4. ScaleBirdsPaul

    Steve Wolf Samson

    Congrats to Steve! Fascinating guy, and the Mite is a gorgeous airplane.
  5. ScaleBirdsPaul

    XFLR5 update

    Looks like there’s an update on a new version of XFLR5 called flow5. Looks to be much more powerful but will be a paid software. https://flow5.tech/ There’s a series of YouTube videos that I’m working through to see if it seems worth the price.
  6. ScaleBirdsPaul

    XFLR5 update

    Normal convention is negative Cm is a nose down moment. At 18+ degrees AoA I’m guessing he’s well past the linear increase in Cl and XFLR is throwing out weird results.
  7. ScaleBirdsPaul

    XFLR5 update

    I found it very sensitive to how the wing was modeled. If you modeled the wing as one “section” with 50 spanwise panels you would get very different results (where stall would start) than 5 sections with 10 panels each, all else being equal. I didn’t like that.
  8. ScaleBirdsPaul

    XFLR5 update

    I’ve used XFLR5 quite a bit. I use it primarily as a GUI for XFOIL, however I use the wing analysis portion quite a bit. It’s the simplest program I’ve found to look at a 3-D wing in the early stages to get lift curves, pitching moments, and load distributions. I haven’t used the stability...
  9. ScaleBirdsPaul

    You're All Trash*, Part 234,567,988 - DarkAero

    As I hit enter I realized a slip would accomplish the same thing, but this is probably more comfortable than being cross controlled.
  10. ScaleBirdsPaul

    You're All Trash*, Part 234,567,988 - DarkAero

    The A-10 uses split ailerons as brakes as well. Just eyeballing it, I would venture a guess that’s it’s performance is roughly equivalent to two split flaps. I don’t think it’s going to turn the airplane into a Stuka, but it will give you the ability to quickly dump drag during a go around...
  11. ScaleBirdsPaul

    You're All Trash*, Part 234,567,988 - DarkAero

    I’ve been following them on Instagram. Seems like they’ve got a real nice setup and are making serious progress. I hope they succeed. My only thoughts on the project are that in a recent post they stood by the partially assembled airframe, and it was smaller than I expected. Not surprising given...
  12. ScaleBirdsPaul

    Aerobatic Tandem Two-Seater

    Man now that’s a cabin built for big guys. I’m sold. I’m a fan of the Riblett airfoils as well, although I’m not sure the perils of the NACA foils are as pronounced as he makes them seem In his book.
  13. ScaleBirdsPaul

    Aluminum Tube & Gusset Airbike / Legal Eagle / Parasol Thread

    Chris Heintz’s book “Flying on your own Wings” has an excellent discussion on loading of multiple fasteners in a line. He provides safety factors to account for the stress “flow” ( not to be confused with shear flow) around varying numbers and sizes of fasteners in a line. This should account...
  14. ScaleBirdsPaul

    Kitty Hawk reveals Heaviside, its latest flying vehicle

    They’re comparing the noise of a JetRanger with a single person vehicle. Not exactly a fair comparison.
  15. ScaleBirdsPaul

    PPL written exam...

    The Sporty's app was great, I would drill questions on my way to work or waiting in line. You could sort by topic and it had a huge database. It was kind of a pain for the navigation or figure questions, but those weren't too tricky to me. At first I had a lot of trouble with the wording of the...
  16. ScaleBirdsPaul

    Aluminum Tube & Gusset Airbike / Legal Eagle / Parasol Thread

    That's just wild. Doesn't appear to be the most sturdy Ferris wheel either, surprised it all held up.
  17. ScaleBirdsPaul

    How much pressure needed to deflect flaps, ailerons, rudder, elevator?

    Same here. To be fair, the terms are defined, but it’s not common phraseology. But the lack of units drives me up a wall. I will say though the reason his book is so valuable is that it shows you how to take your design and calculate real loads. Plenty of books show you how to determine lift...
  18. ScaleBirdsPaul

    How much pressure needed to deflect flaps, ailerons, rudder, elevator?

    Hiscocks book Light Aircraft Design has a lot of good information on control surface loads. Sizing the control surfaces is a two part problem. You need to ensure there is enough deflection (authority) to meet the design load cases at both the forward and aft CG cases. You also need to ensure the...
  19. ScaleBirdsPaul

    Aluminum Tube & Gusset Airbike / Legal Eagle / Parasol Thread

    I wouldn’t rely on fishmouthing for any sorting of real loads in a non-welded joint. If you’re intersecting at close to a 90 degree angle you might take up some compressive axial loads but that’s it. Fortunately a well-designed truss should minimize bending moments at the joints so that the...
  20. ScaleBirdsPaul

    Raptor Composite Aircraft

    This is not a defense of the Raptor project at all but I think you have to be very careful throwing out the scam term. Is every failed business then a scam? Investing is not 100% guaranteed. If the investor wants to get in on something that is “too good to be true” to either make a quick buck or...
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