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  1. Birdman100

    "New" Hummel Bird? How?

    Cri-cri and Hummel Bird are two successful small planes, but now fairly old designs. If you were to design a good successor how would you do that? For me, carbon composite is apparent choice, and I will pick one (nose) engine solution. What engine, 2s/4s...? Is there market for such new plane?
  2. Birdman100

    Laminate Calculator

    I made Calculator for composite laminates and sandwiches in excel and decided to share. You can play with different fibers (carbon, glass, aramid, or mixed carbon-aramid (hybrid)), different resins (epoxy, polyester, vinyl ester), different fiber/fabric areal weights and fiber fractions and so...
  3. Birdman100

    single seat, composite, ultralight STOL - would you like it?

    Imagine a small, very light, single seat all carbon fiber pusher STOL. It should be open cockpit (wind in the hair), with flight feeling similar to this shown in this VIDEO, but powered and STOL! Something you could jump to the friends barbecue with and land in its backyard drink a few bears...
  4. Birdman100

    How far your enthusiasm goes?

    What are you ready to do and how far are you ready to go to accomplish your "homebuilt" dream? Are you ready to... ...transform your flat into workshop? Like me 5 yrs ago when I was building my first homebuilt project IKAR (well I understood "homebuilding" quite literally)... ... to...
  5. Birdman100

    Prop in separated flow - cons?

    I just read Normans comment in a thread about VGs, evoking issues if prop is in separated flow. Think of it for a moment and it sounds completely logical - avoid positioning prop behind some obstacle. But then, thinking again it seems answer is not that simple. First, we use to think that any...
  6. Birdman100

    slotted airfoils experimental data?

    In order to check/validate CFD tool Im working in, I need some reliable airfoil data. Simple, isolated airfoils are not an issue; there is plenty of (older) experimental results (Nasa, Wortman etc). But I want to verify CFD at more complex cases like airfoils with slots, slotted flaps (or...
  7. Birdman100

    Theoretical question (aspect ratio)

    Well known formula for induced drag coeffic is Cdi=CL^2/(AR*PI*e). Formula for AR is AR=b^2/A (b-span, A-wing area). What confuses me, is that these formulas (especially the latter) give same results for, what I consider as aerodynamic different cases. Picture will help: All tree cases...
  8. Birdman100

    Gelcoat or PU coating on composite?

    It seem that Polyurethane paints and lacquers are becoming more frequent choice for composite surfaces instead of gelcoats. Am I right about that and what do you think is the reason? Surface quality? Weather (UV) resistance? Weight? Processing? Cost? Other? As far as I know there was a lot of...
  9. Birdman100

    movable vortex generators

    Hi all! I came up with the idea about moving (or controllable) vortex generators. I didnt find the same thing on the web, so does anyone have some info on the existence of such a thing? The idea would be to install VG's that could be rotated by command, so that they are aligned while in flight...
  10. Birdman100

    Finite wing Cm?

    It is evident that Cl and Cd are different for 2D airfoil, and real 3D wing. But, what about Cm?? I have never find any expression showing the way the Cm changes due to 3D effects. Is it possible that Cm does not change in case of 2D and 3D? I would say that Cm must change because moment, or Cm...
  11. Birdman100

    Resin Infusion - thin laminate

    Is it possible to do resin infusion with very thin laminates (1 x 160gsm textreme carbon)? My assumption is that there will be much "friction" in such a thin laminate...(?). Can anyone name a few really good (if not the best available) Epoxy systems for RI process, with superior mechanical...
  12. Birdman100

    Archaeopteryx airfoil

    Hi all! Anybody have a drawing of Archaeopteryx (Swiss made foot-launhable glider) wing airfoil? Thanks! I was investigate it looking at fotos but I would like to have the exact airfoil shape (coordinates if possible)...