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  1. addaon

    new battery from lithium ion inventor

    Yeah, there are a few (very small) production solid-state lithium cells out there, and they’re a joy to work with. Big ones would be awesome.
  2. addaon

    Aerodynamics of Propulsion

    Thanks for the input, all. Consistent. Don’t be over ambitious, don’t take theory further then it goes, experiment. Agreed. The logic behind asking about expansion in both directions was (a) it fits my geometry reasonably well and (b) the wall angles would be less extreme, which seems like a...
  3. addaon

    Aerodynamics of Propulsion

    Let me clarify, definitely was fuzzy on my side. 1) The table I'm looking at in the book actually has a length of "3" (1.5x the heat exchanger height) for all the expansion ratios; I'm not seeing a formula for streamline diffuser shape, and indeed there's even a comment that an attempt to fit...
  4. addaon

    Facet Opel

    Thanks, Norman, that’s interesting.
  5. addaon

    New Alice Starts Taxi Testing

    Over 500 A water-cooled charging cables are standard, they end up thinner (but still hefty) — see the 250 kW Tesla chargers for an example. Electric cars have cells that prioritize energy density over power density. That’s not yet an option for aircraft, and is always a tradeoff. In general...
  6. addaon

    New Alice Starts Taxi Testing

    Smaller than the average supercharger station. Less than a refinery. Infrastructure development is definitely one of the more fun projects related to electrification.
  7. addaon

    Bourke engine viability?

    Where does the carbon in the fuel end up if not in CO2? Just about anything else (soot, deposits, carbon monoxide) is far worse.
  8. addaon

    New Alice Starts Taxi Testing

    Yes. I've worked on aircraft that charge about as quickly and conveniently as filling my Lycoming-powered aircraft. I don't see why this, of all things, is surprising. Edit: Part of this is an indictment of how we fill GA planes today. Heavy hoses, dual connectors for grounding and filling...
  9. addaon

    New Alice Starts Taxi Testing

    Hm, we might be talking at cross-purposes. For turn-around on a passenger airplane, there are a bunch of factors, including getting the pax off, cleaning, boarding again, etc.; but none of those seem like they would vary significantly with propulsion type. So the remaining part of turn-around...
  10. addaon

    New Alice Starts Taxi Testing

    Battery energy density is currently lower than energy density of common fuels, excluding oxidizer weights. By quite a large margin, but that margin will only decrease. Landing at takeoff weight is a disadvantage, but not an infinite one -- other advantages can easily outweigh it. (Heck, I've...
  11. addaon

    Facet Opel

    Why would planks be any more prone to flutter than any other planform? If nothing else there are fewer surfaces to flutter so fewer critical frequencies in play.
  12. addaon

    Any thoughts on my AC-5M project?

    Quick math: Assume that you get 3.5 lbs/hp at 55 kts, and get 30 hp before you hit the limiter at 55 kts... slight derating for increased speed. (We can do a better estimate here, but it won't be too far off.) You need 620 lbs / 17 = 36.5 lbs thrust to counter drag, which leaves you with 68.5...
  13. addaon

    My pico-light Flying Bike

    Processor speed is not the concern, servo speed is. Your control logic has built in assumptions about maximum servo lag, and can diverge (oscillate, etc) if those assumptions are not met. Good luck!
  14. addaon

    Any thoughts on my AC-5M project?

    One last thought -- how sudden is the cutout at overtemp? Do you have a temp gauge so you know when it's coming? The one scary scenario I can see is a Vx climb, trimmed for low speed, which is critical in both climb performance (or else why Vx) and cooling.... with a high thrust line. Sudden...
  15. addaon

    Any thoughts on my AC-5M project?

    Yeah, three minutes at full with no ambient flow seems pretty darn good. If you're comfortable with that amount of thrust, I wouldn't tweak it much further. Getting more thrust for less time (increasing pitch) probably isn't a win. 150 lbs thrust for 35 hp is 4.3 lbs/hp, which is pretty good but...
  16. addaon

    Aerodynamics of Propulsion

    Streamline Diffusers and that pesky Third Dimension Table 12-1 gives a table of coordinates for a streamline diffuser of different expansion ratios (0.25, 0.30, 0.40, 0.50). The coordinate system here is a bit odd -- I'm sure it's explained somewhere else in the book, but at a flip through I...
  17. addaon

    My pico-light Flying Bike

    (You have redundant control with four surfaces, and if you’re using something sufficiently configurable you may be able to get some small amount of yaw control out of the extra actuator —front left and back right down, front right and back left up should be neutral (with correct gains) in roll...
  18. addaon

    My pico-light Flying Bike

    Just repeating this because this is the key. Folks, hobbiest-level augmented stability is here, it’s cheap, and it works pretty well if you don’t look at absolute reliability numbers. We’ll see if this particular system can handle this level of instability (fast enough servos, etc)…. But the...
  19. addaon

    Any thoughts on my AC-5M project?

    What power usage were you seeing? Is full throttle hitting a current limit or an rpm limit? Good stuff!
  20. addaon

    Hurricane Ian

    Stay safe!
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