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  1. autoreply

    E-Racer Blended Winglet and Interference Drag CFD Analysis

    That's a common misunderstanding. Winglets are better than any straight wing. Proof from reality; all open class sailplanes have winglets, even the ones with an aspect ratio of over 50.
  2. autoreply

    A 55% SR-71 Blackbird under construction!

    Visited them last summer, by then the SR71 was already out and delivered. Orange Aerospace is doing some cool stuff, including a narrow-isle large-format airliner scale model for aero research. More drone guys than airplane guys though.
  3. autoreply

    Roomy high wing options?

    Composite sandwich? 2x200g/m2 CFRP, pvc, 2x200g/m2. Areal weight below 2 kg/m2 (0.4 lbs/sqft). Even at that size, that'd be pretty light. That's a laminate you can walk on.
  4. autoreply

    Crossing the Atlantic Ocean with a homebuilt jet or an electric aeroplane.

    So let's reason from what is in existence and flying today. Best performance of sailplanes is about 1:70 @ 70 kts @ 1300 lbs. Let's assume we double mass with 200 Wh/kg batteries. That'd be 1:70 @ 100 kts @ 2600 lbs. Power required is about 11700N/70*50m/s= 8.3 kW. That's THP, with 80% prop...
  5. autoreply

    Pros and Cons on Composites vs Aluminum

    It always depends right? If you design a swoopy Lancair-type airplane, this would be a good technique to make a one-off or small series without building plugs, molds etc. Basically 21st century Rutan method, same as in the first video I posted in this thread.
  6. autoreply

    Pros and Cons on Composites vs Aluminum

    Anything that's thermoformable. Typically PET and PVC. Curveworks couldn't accomodate us for Rohacell or PEI because their system isn't set-up for high-temperatures, but there is no fundamental reason you couldn't do it that way. The big advantage with thermoforming is that for high curvature...
  7. autoreply

    Pros and Cons on Composites vs Aluminum

    Some inspiration to combat the old "endless sanding and tons of moulds": https://www.linkedin.com/posts/paul-dijkstra-31548a65_%3F%3F%3F-%3F%3F%3F%3F%3F%3F%3F%3F%3F%3F%3F%3F%3F-%3F%3F%3F%3F%3F%3F-activity-7139954018671304705-DBj0?utm_source=share&utm_medium=member_desktop I've used the same...
  8. autoreply

    Horrible news from Vans Aircraft

    This was actually one of the assignments at university. Do a trade off for I think it was a control horn and how D, d and t should be optimized. Values are true for aluminium, NOT for other metals (or composites, wood). I recall that by the time you're at 1.5D edge distance and 2D pitch, all...
  9. autoreply

    Pros and Cons on Composites vs Aluminum

    Here I guess. I've engaged the debate as in this thread in my entire professional life time after time again. Lots of legacy and "black aluminium" in all sectors I've worked in. Obviously, composites don't work ;-) You can certainly mass-produce a Van's like design at a reasonable cost level...
  10. autoreply

    1 000 km/h speed with a prop plane ?!

    Concorde also had (and to this day has) the most efficient turbofan/jet engines in history. That certainly doesn't bring it's supersonic fuel efficiency close to a modern airliner, but the difference is significantly smaller that what you'd think solely looking at the aerodynamics.
  11. autoreply

    Two engines one prop

    I've discussed this topic (two engines in the fuselage) at length. Bottomline; it'd only make sense with two props, counterrotating and the bearing in between them fully fire-proofed. All systems should be completely split, i.e. no joined batteries, gearboxes etc. The modern electric engines...
  12. autoreply

    Scanning and comparing prop blade profiles

    I have a patent application on my name for balancing tools for rotors/props. Key is removing friction from the system. Frictionless (air-lubricated) bearings are a good way. Forget about the bearing, let it roll freely and measure the angle to completely exclude friction. As for scanning...
  13. autoreply

    Verhees Delta D2 ? Does anyone know if any plans have ever been sold for it ?

    You got me triggered there. I'm one of those pros, designing, building, testing, flying and certifying new composite airframes and parts. Been doing it about half as long as Scaled and a decade longer then Dark Aero. Note that both Scaled and Dark aero do a lot of indirect composite molds.. For...
  14. autoreply

    Verhees Delta D2 ? Does anyone know if any plans have ever been sold for it ?

    That's about what I'd expect from an organisation like NASA and the absolute last way I'd do it myself. Develop the required unfolded structure (CAD or paper model). Transfer the unfolded pattern to lasercut steel or aluminium templates. Hand laminate or place a dry single layer of CF. Glue in...
  15. autoreply

    Verhees Delta D2 ? Does anyone know if any plans have ever been sold for it ?

    True. But I think that's a realistic price point for the amount of work required to convert a design into a fully worked-out production design. So DXF's, build instructions, parts list etc. If a couple dozen people cannot pony up that amount of money, I think we've answered the actual market...
  16. autoreply

    Verhees Delta D2 ? Does anyone know if any plans have ever been sold for it ?

    Any place with a decent waterjet or lasercutter of sufficient size is sufficient, precision exceeds what you'd need. Add a CNC controlled press and that's all you need. At least here in Europe, Trumpf cutters and presses are the standard to navigate by.
  17. autoreply

    Verhees Delta D2 ? Does anyone know if any plans have ever been sold for it ?

    I've flown the D2 and spoken to Bart at length with series production in composites in mind. Sidenote; I'm a composites guy that likes long slender wings ;-) I wouldn't convert this design to composites. You might gain a little bit here and there, but you can wonder whether that's worth the...
  18. autoreply

    New rotorcraft concepts

    A few of the eVTOL's have fixed rotors (no lead/lag or flapping hinges, nor pitch control). It's doable, but bending stresses on the rotors (due to asymetric load with forward flight) are enormous and too much for a typical rotor slenderness unless you make the blade of solid CFRP. Broader...
  19. autoreply

    OT: Design load factor for road vehicles?

    Anecdotal; even aerobatic sailplanes max out on their G-impact (road transport is >10G's) I've never nót maxed out trailering an airplane on pretty smooth tarmac driving sensible (who, me?) Frankly, for very stiff structures, a couple dozen G's wouldn't surprise me. Having some play in the...
  20. autoreply

    Verhees Delta D2 ? Does anyone know if any plans have ever been sold for it ?

    I have seen the D1 (starting two decades ago) and the D2. I've flown the Verhees D2 last year. I've also had a thorough look at both designs and a solid aerospace background to judge either. Bottomline: It's a well-thought out design, the D2 even more so. It serves it's mission (long-distance...
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