Search results

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

  1. rotax618

    Low aspect ratio sport plane ideas

    It looks like the UFO has a rib spacing (stringer spacing) of about 300mm, for an aircraft of the UFO’s performance I recon that you could go to 400mm or a bit more.
  2. rotax618

    Low aspect ratio sport plane ideas

    A more stable vortex would form on that planform if the sweep from the nose to the false spar was less than the sweep from the false spar to the tip.
  3. rotax618

    Low aspect ratio sport plane ideas

    I really don’t understand why a circular or eliptical wing would be any more difficult to build than a diamond shaped wing, a circular/eliptical wing doesn’t need ribs, David Rowe used stringers bent over 3 or 4 lightweight spars - you could use blue foam infill to stiffen them - the sem-span of...
  4. rotax618

    Low aspect ratio sport plane ideas

    If the mission is to build a successful small LAR airplane that can operate in and out of a small field the formula is fairly simple. 1. Keep the wing loading as low as possible, and the power loading as high as possible. 2. Choose a planform that provides the greatest wing area for a given span...
  5. rotax618

    Low aspect ratio sport plane ideas

    My experiments with LAR indicates that to perform well they need a very low wing loading, you can compensate with power but increased wing loading means increased induced drag which takes away the advantages of LAR. It is not too difficult to design a low wing loading for LAR, the UFO is only...
  6. rotax618

    Low aspect ratio sport plane ideas

    I was replying to bi_dg who's post advocated scaling up a couple of RC pure deltas. I did say that these types are not the subject of this thread - maybe if it flew with 46HP it maybe a contender.
  7. rotax618

    Low aspect ratio sport plane ideas

    Dyke did design and build a single seat “Stingray”, it was of wood construction and flew for many years before being consigned to a museum. The Dyke Stingray and Verhees Delta are not light nor simple, they are in another class of LAR - having a relatively high wing loading, a long takeoff roll...
  8. rotax618

    Low aspect ratio sport plane ideas

    For a very light LAR the planform is important, a pure delta or a double delta as you have shown are not the best, the double deltas have a deep stall problem as SAAB found, plain deltas don’t have a progressive vortex formation as circular, Zimmerman and reverse Zimmerman planforms have.
  9. rotax618

    Low aspect ratio sport plane ideas

    I built a couple of “Drifters”, and as Matthew said, their performance varies, I found the glide to be approx 8 - 12: 1. If you observe the videos of the various iterations of the UFO, it is plain to see that it has pretty good climb and cruise performance for its modest power (46HP). It...
  10. rotax618

    Low aspect ratio sport plane ideas

    David Rowe reported that the power off glide of one of his UFOs was “about the same as a Drifter”. As far as using a rectangular centre section, there is probably no reason why that wouldn’t work, note that the leading edge of the UFO is relatively sharp because the disc planform doesn’t stall...
  11. rotax618

    Low aspect ratio sport plane ideas

    Charles Zimmerman‘s original quest was to investigate the effect of span (aspect ratio) on wings with a Clark Y airfoil. His wind tunnel model was a wing with circular wingtips, he progressively reduced the span until only the circular wingtips remained, whereupon he found a marked increase in...
  12. rotax618

    Low aspect ratio sport plane ideas

    there is no washout, it only appears so because the disk is flat bottomed And the chord line is greater for the wider chord inner ribs.
  13. rotax618

    Inverting a G13bb

    A 4 bearing 3 cyl or 5 bearing 4 cyl crank should be strong enough if driven off the flywheel end, provided they are not fitted to an aerobatic aircraft. Of course they require some sort of a flywheel the tame TVS.
  14. rotax618

    Low aspect ratio sport plane ideas

    A LAR is not a plank and has a much larger “tail volume”. You can see the the small amount of reflex in the UFO.
  15. rotax618

    Low aspect ratio sport plane ideas

    This may shed some light on the advantages of various planforms for a LAR wing. https://apps.dtic.mil/sti/pdfs/ADA397533.pdf
  16. rotax618

    Low aspect ratio sport plane ideas

    The Farman has the least efficient LAR planform, it is only a short span conventional airplane.
  17. rotax618

    Low aspect ratio sport plane ideas

    Personally, I wouldn’t be too “experimental” with the structure. The aerodynamics is experimental enough, it is best to stick to less problematic construction methods. Since the aircraft is small, very light and has very deep spars, the ribs could be cut from blue foam with epoxy fibreglass tape...
  18. rotax618

    Mold Material That Can Be Laser Cut

    A CNC path can have a a finishing cut that can use a very small dia. tool if that is what is required, or a “dog bone“ corner which is good for stress relief and allows sharp corner fit.
  19. rotax618

    Mold Material That Can Be Laser Cut

    A simple diy CNC cuts/shapes MDF beautifully.
Top