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  1. K

    Ducted fan aircraft

    WOW, $125/kilogram or $60/lb of thrust! kenkad
  2. K

    NASA's segmented wing flaps

    I was wondering where you obtained the info about the 44 servos. Then I found this article http://national.spacegrant.org/meetings/presentations/2014_Spring_National/16.pdf and indeed it is 44 segments. But, using fiber optics to determine strain, WOW. Not too practical at this moment or...
  3. K

    NASA's segmented wing flaps

    This is interesting because it heralds more use of electronic controls rather than rods/cables. Sure would like to know the full story of the electronic interface and how they decide to balance loads on the wings. Photos of the Day: NASA kenkad
  4. K

    Is electric propulsion worth it?

    There was no market for the free piston linear generators until now. Electric vehicles need to extend their range. Batteries are too expensive and it adds too much dead weight. Then it takes longer to recharge, etc. I am interested in 5-10kW units (not 50-100kW) that can be paralleled if...
  5. K

    Ducted Fans

    check out this link! Catapulting Into the Skies: 3D Printed UAV Soars With Electric Ducted fan Engines - 3DPrint.com They apparently plan to build a 10 foot wing span next. A ducted fan no less. GO STUDENTS! The website is listed at the end of the article. kenkad
  6. K

    Is electric propulsion worth it?

    tilopa, Your hybrid is waiting for the free piston (opposing) generator. Very small form factor that should be able to be fitted easily into your aircraft design. I am sure there is much activity and progress besides Toyota. Not for the faint hearted because the electronic controls are...
  7. K

    Please Critique My Design Idea

    something-awful, If they have anything on the AC of a box wing, that would be great. Simplistically, I would guess that its the centroid of the center of lift of each wing, modfied by the ratio of the actual lift of each wing. Centroid moves toward the wing with the greater total lift. kenkad
  8. K

    Please Critique My Design Idea

    Tilopa I would like to pose the same question to you that I have asked others regarding ring, elliptical or box wing designers. How do you determine the aerodynamic center for this type of wing? I have a sketch of a box wing concept that has the cord of the back wing greater than the front...
  9. K

    Wing torsional structural design.

    An FEA 3D CAD analysis of that bridge structure in the wing past the 1/4 chord point compared to a standard rib approach should clarify the design attributes. I would then want to add ribs at the apex junctions and compare that as well. It really gets to the stressed skin. Might be great for...
  10. K

    Ducted fan aircraft

    Lucrum, Here is another link that I thought I had listed once before, but, here it is again. http://www.icas.org/ICAS_ARCHIVE/ICAS2010/PAPERS/150.PDF As you will be able to see (Section 5, Thrust Comparison), it is not just basic physics. As you can see decreasing hub and possibly boundary...
  11. K

    Ducted fan aircraft

    Lucrum, As you can now clearly see, just do your thing. Remember its just basic physics. If you are going to do a model first, I would be very interested in how you are progressing. kenkad
  12. K

    Ducted fan aircraft

    Autoreply, That is not the only factor causing loss for a single prop/fan. If you are claiming that it is the most dominant, please give us a link to some published data. Just words are not justification. kenkad
  13. K

    Ducted fan aircraft

    My approach is to get the motor/s out of the duct area, whether center hub or ring shroud. Keep the ducted fan assembly light, just sufficiently rigid. Anyway, like I said before, Trek CFD or Thingap motor designs are not on my 'I think I can/will buy that' list. My first 'off-the-shelf'...
  14. K

    Ducted fan aircraft

    staggermania, Better to do cogged belt drive to the counter rotating fans/props with one motor. It just might be possible to design a combined inrunner/outrunner BLDC motor with multiple (three?) sets of three-phase drives per motor section. Somehow you need to separate the coils (some kind of...
  15. K

    Ducted fan aircraft

    So many variables for ducted props/fans. Counter-rotating is necessary because the two props/fans need to rotate at different RPMs (get rid of flow straighteners). Separation distance between the two props/fans is speed dependent (not the rotation speed). Since the counter rotating props/fans...
  16. K

    Elytron 2S - the first commercial tiltrotor?

    Looks nice. Seems I have seen that kind of design in a single passenger concept that has dual counter rotating ducted fans. I did contact them and asked how they computed the NP for that joined wing since I could not get any useful information on HBA. I am curious if they will respond. kenkad
  17. K

    box wing neutral point equation

    Starjar, Box wing designs are by definition wing + wing. Both wings lift. That is why I believe the wing incidences are important to locate the NP. I suspect negative incidence of the rear wing relative to the front wing is needed. Still I would like to have found a paper or class room...
  18. K

    box wing neutral point equation

    If we take a scenario that both wings are identical is size, shape (same airfoils), sweep (+ and -) and incidence (assuming adequate separation) identical, then the NP is obvious. It is centered between the 1/4 MAC of the two wings. This assumes that the Cl (or lift distribution) is...
  19. K

    box wing neutral point equation

    Can someone please provide a link to a paper or discussion on how the neutral point of a box wing aircraft is determined (not joined wing)? Obviously the wings are swept and I already know how to determine the neutral point for a normal swept wing aircraft. Thank you in advance.kenkad
  20. K

    "minimum" personal mobility device --ground and airmobile.

    Rienk, A diamond pattern! Great steering problem depending on the actual diamond arrangement! Seems J Bede tried that. Watch the video. You ever see him go around corners at any kind of speed? Sort of like the bikes/cars that have wheels that go up and down when you stop and ride. Same...
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